Electrical System Design
Electrical System Design
Electrical System Design
COMPANY STANDARD
20208.ENG.ELE.PRG
Rev. 13 July 2021
Digitally Signed by
SORIN RUGAN
02/08/2021
08:56:48
Sorin Rugan
Paolo De
13 July 2021 Final Issue Giuseppe De Vincolis Fabien Duclocher
Bartolomeis
Massimo Gorlini
REV. DATE Reason for issue Prepared Verified Approved
REVISION TRACKING
For information about the content of this standard, please refer to persons mentioned on first
page or to COMPANY Standard Team (mbxc&st@eni.com).
INDEX
1 GENERAL.............................................................................................. 9
SCOPE ................................................................................................. 9
NORMATIVE REFERENCES ................................................................... 9
1.2.1 International, IOGP and European standards 9
1.2.2 Laws, Decrees, Directives 20
1.2.3 Internal standardization references 20
2 FUNCTIONAL REQUIREMENT.............................................................. 24
DEFINITIONS.................................................................................... 24
2.1.1 General definition 24
2.1.2 Specific definition 24
SYMBOLS AND ABBREVIATIONS ....................................................... 26
GRAPHIC, SYMBOLS, CODES AND IDENTIFICATIONS TAG ................ 27
OPERATIVE ENVIRONMENT .............................................................. 27
MEASUREMENT UNITS ...................................................................... 27
DESIGN AND ENGINEERING PRINCIPLES ......................................... 27
2.6.1 Protection against explosion and fire hazard 27
2.6.2 Standardisation of equipment and materials 28
2.6.3 Certificates, declarations and test reports 28
2.6.4 Energy efficiency 28
ELECTRICAL SYSTEM DESIGN ........................................................... 28
2.7.1 General 28
2.7.2 Electrical loads classification and load balance 28
2.7.2.1 Loads Classification ....................................................................................... 28
2.7.2.2 Load balance ................................................................................................. 31
2.7.2.3 Rated voltage levels and maximum voltage for the equipment ..................... 31
2.7.2.4 Selection criteria of voltage levels ................................................................ 33
2.7.2.5 Voltage drops ................................................................................................ 34
2.7.2.6 Voltage and frequency variation ................................................................... 34
2.7.2.7 Maximum value of rated current on switchgears bus-bars ............................ 35
2.7.3 Power factor 35
2.7.4 Harmonics distortion 36
2.7.5 Neutral earthing 36
2.7.5.1 Medium Voltage systems ............................................................................... 36
2.7.5.2 LV systems .................................................................................................... 37
2.7.5.3 AC UPS systems ............................................................................................ 39
2.7.6 Power distribution configuration 39
2.7.7 Electrical protection 40
2.7.7.1 Short circuits protections .............................................................................. 40
2.7.7.2 Overloads protections ................................................................................... 41
2.7.8 Intertripping and interlocking 41
2.7.9 Earthing and lightning system 42
2.7.9.1 Earthing system ............................................................................................ 42
2.7.9.2 Protection against lightning .......................................................................... 42
2.7.10 Emergency electrical system 43
2.7.11 Black start requirements 43
2.7.12 Motor starting system selection 44
2.7.13 Electrical Management System (EMS) 44
1 GENERAL
SCOPE
This COMPANY Specification defines the minimum electrical design, engineering and installation
criteria to be used and the minimum technical requirements for electrical equipment and
materials to be installed in both Eni onshore and offshore Oil & Gas facilities.
NORMATIVE REFERENCES
Materials and equipment shall fully comply with all requirements defined by the international/
European rules, laws, decrees, directives and internal standardization documents.
For facilities in Italy, the international and IOGP standards of the TABLE 1 shall be applied, with
the following amendments:
• If there is a “CEI EN” standard with the same number as the corresponding IEC standard,
the “CEI EN” standard shall be applied in lieu of the IEC one (e.g. CEI EN 61439 in lieu
of IEC 61439).
• If there is a “CEI” standard that replaces an IEC standard, identical or with modifications,
the CEI standard shall be applied (e.g. CEI 64-8 in lieu of IEC 60364).
• The standards indicated in TABLE 2 shall be applied in addition to those of TABLE 1.
• The cables shall be as indicated in 2.8.11.10.
• IEC 60502 series shall not be used.
• IEC 60092 series shall not be used for cables.
For facilities in countries that are members of CENELEC, the international and IOGP standard of
the TABLE 1 shall be applied, with the following amendments:
• If there is a “EN” or “HD” standard with the same number as the corresponding IEC
standard, it shall be applied in lieu of the IEC one (e.g. EN 61439 in lieu of IEC 61439).
• If there is a “EN” standard that replaces an IEC standard, identical or with modifications,
the EN standard shall be applied.
• The standards indicated in TABLE 3 shall be applied in addition to those of TABLE 1.
• The cables shall be as indicated in 2.8.11.10, for facilities in countries of the European
Union.
• IEC 60502 series shall not be used for facilities in countries of the European Union.
• IEC 60092 series shall not be used for cables in facilities in countries of the European
Union.
• Application of national standards shall be evaluated on project basis.
In any case, all Laws, Decrees and Directives, issued by local Entities and Authorities under
which equipment shall be installed, shall be applied.
The Regulation 305/2011 of the European Parliament and of the Council (“REGULATION (EU) No
305/2011 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 9 March 2011 laying down
harmonised conditions for the marketing of construction products and repealing Council Directive
89/106/EEC”) and its interpretation through National Laws and Committee shall be complied
with for cables installed in EU.
The Directive 2013/35/EU of the European Parliament and of the Council (“DIRECTIVE
2013/35/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 26 June 2013 on the
minimum health and safety requirements regarding the exposure of workers to the risks arising
from physical agents (electromagnetic fields) (20th individual Directive within the meaning of
Article 16(1) of Directive 89/391/EEC) and repealing Directive 2004/40/EC”) shall also be
applicable outside EU, in the cases indicated in the present document.
All systems, equipment, materials and engineering philosophies relevant to this specification,
shall comply with the COMPANY Standards listed here below:
• 20056.ENG.ELE.STD “Explosion-proof connection box with contactor for shedding”
• 02947.ENG.ELE.STD “Measurement of earth electrical resistivity”
• 03778.ENG.ELE.STD “Electric generator driven by gas turbine”
• 20213.ENG.ELE.STD “Diesel\gas driven engine generator set”
• 20231.ENG.ELE.PRG “Minimum technical content of documents for each project
development phase”
• 20168.ENG.ELE.STD “Synchronous electric machines”
• 28881.ENG.ELE.STD “M.V. switchgear and controlgear (over 1000V a.c. and up 52kV
a.c.) - typical incoming / outgoing feeders”
• 28880.ENG.ELE.STD “L.V. switchgear and controlgear assemblies (up to 1000 V a.c 1500
V d.c) – typical incoming / outgoing feeders”
• 20174.ENG.ELE.STD “Aids to navigation & helideck lighting system for offshore platforms
and floaters
• 28882.ENG.ELE.STD “AC uninterruptible power supply system - typical configurations”
• 28914.ENG.ELE.STD “Luminaires”
• 28915.ENG.ELE.STD “Electrical bulk material”
• 28916.ENG.ELE.STD “Cable ladders and cable trays”
• 28917.ENG.ELE.STD “Floodlight high masts”
• 20172.ENG.ELE.STD “High voltage substation with sulphur hexafluoride (SF6) insulated
metal-enclosed switchgear from 72.5 kV to 245 kV”
• 20173.ENG.ELE.STD “Air insulated high voltage substation from 52 kV to 245 kV”
• 20180.ENG.ELE.STD “Electrical Management System (EMS)”
The following COMPANY documents shall be complied with where referenced in the present
document:
• 20183.VAR.GEN.STD “Units of measurement”
• 20198.VAR.LCI.STD “Item numbering”
• 20452.ENG.MEC.PRG “Guideline for HVAC systems for offshore / FPSO production
installations”
• 20453.ENG.MEC.PRG “Guideline for HVAC systems for onshore production installations”
• 20456.ENG.STA.STD “Instrumentation & automation plants included In HVAC package”
• 20531.ENG.STA.STD “Measure, control, data processing and similar associated electronic
system protection subject to indirect lightning”
• 20532.ENG.STA.STD “Earthing systems for instrumentation plants”
• 21000.ENG.PRC.STD “Plant graphic symbology”
• MOD.ELE.RMA.022 “Data sheet for low voltage three phase cage induction motors (IOGP
S-703D)(TDS)”
• MOD.ELE.RMA.023 “Quality requirements for low voltage three phase cage induction
motors (IOGP S-703Q) (IDS)”
• MOD.ELE.RMA.024 “Information requirements for low voltage three phase cage induction
motors (IOGP S-703L) (DDS)”
• MOD.ELE.NAV.001 “Aids to navigation & helideck lighting system for offshore platforms
and floaters (TDS)”
• MOD.ELE.NAV.002 “Aids to navigation & helideck lighting system for offshore platforms
and floaters (IDS)”
• MOD.ELE.NAV.003 “Aids to navigation & helideck lighting system for offshore platforms
and floaters (DDS)”
• MOD.ELE.NAV.009 “Temporary navigation aids system (TDS)”
• MOD.ELE.NAV.010 “Temporary navigation aids system (IDS)”
• MOD.ELE.NAV.011 “Temporary navigation aids system (DDS)”
• MOD.ELE.MVS.001 “Data sheet for high voltage switchgear and controlgear (including
IOGP S-620D) (TDS)”
• MOD.ELE.MVS.002 “Quality requirements for high voltage switchgear and controlgear
(IOGP S-620Q) (IDS)”
• MOD.ELE.MVS.003 “Information requirements for high-voltage switchgear and
controlgear (IOGP S-620L) (DDS)”
• MOD.ELE.LVS.001 “Data sheets for IEC 61439 LV switchgear and controlgear assemblies
(including IOGP S-560D) (TDS)”
• MOD.ELE.LVS.002 “Purchaser order quality requirements (POQR) for IEC 61439 LV
switchgear and controlgear assemblies IOGP S-560Q) (IDS)”
• MOD.ELE.LVS.003 “Supplier deliverable requirements list (SDRL) for IEC 61439 LV
switchgear and controlgear assemblies (IOGP S-560L) (DDS)”
• MOD.ELE.LVS.008 “Electrical Power Unit - data sheet”
• MOD.ELE.GEN.005 “Electrical documentation and data books check list (DDS)”
• MOD.ELE.GEN.006 “Electrical production check list (DDS)”
• MOD.ELE.ACB.001 “Data Sheet for Batteries (IEC) (IOGP S-740D) (TDS)”
• MOD.ELE.ACB.002 “Quality Requirements for Batteries (IEC) (IOGP S-740Q) (IDS)”
• MOD.ELE.ACB.003 “Information Requirements for Batteries (IEC) (IOGP S-740L) (DDS)”
• MOD.ELE.UPS.001 “Data Sheet for AC Uninterruptible Power Systems (UPS) (IEC 62040-
3) (IOGP S-701D) (TDS)”
• MOD.ELE.UPS.002 “Quality Requirements for AC Uninterruptible Power Systems (UPS)
(IEC 62040-3) (IOGP S-701Q) (IDS)”
• MOD.ELE.UPS.003 “Information Requirements for AC Uninterruptible Power Systems
(UPS) (IEC 62040-3) (IOGP S-701L) (DDS)”
• MOD.ELE.UPS.005 “Data Sheet for DC Uninterruptible Power Systems (UPS) (IEC 62040-
5-3) (IOGP S-702D) (TDS)”
• MOD.ELE.UPS.006 “Quality Requirements for DC Uninterruptible Power Systems (UPS)
(IEC 62040-5-3) (IOGP S-702Q) (IDS)”
• MOD.ELE.UPS.007 “Information Requirements for DC Uninterruptible Power Systems
(UPS) (IEC 62040-5-3) (IOGP S-702L) (DDS)”
• MOD.ELE.ESH.001 “High voltage substation - technical data sheet (TDS)”
• MOD.ELE.ESH.002 “High voltage substation - inspection data sheet (IDS)”
• MOD.ELE.ESH.003 “High voltage substations - required documentation data sheet (DDS)”
• MOD.ELE.TRA.001 “Data sheet for transformers (IOGP S-720D) (TDS)”
2 FUNCTIONAL REQUIREMENT
DEFINITIONS
Normative References from paragraph 1.2 shall be used for the following definitions and
terminology.
COMPANY:
The party that initiates the project and ultimately pays for its design and construction. The
COMPANY will generally specify technical requirements. The term “COMPANY” may also include
agents or consultants authorised to act for, and on behalf of, the COMPANY.
CONTRACTOR:
Party that performs the design, procurement, supply, manufacturing, construction, testing and
commissioning activities (or some of them).
SUBCONTRACTOR:
Any supplier, distributor, vendor, or firm that furnishes supplies or services to or for a prime
contractor or another subcontractor.
SUPPLIER:
Organisation or person that provides a product.
VENDOR:
A supplier of material or services offered from a catalogue or price list and purchased by issue
of a purchase order.
The word shall is used to indicate that a provision is mandatory.
The word should is used to indicate that a provision is not mandatory, but recommended as
good practice.
• UPS;
• Batteries.
It is normally divided in:
• Switchroom;
• Transformer room;
• Battery room;
• Cable cellar;
• Multiservice room.
Instrument/automation cable It is used for transmission of information and command with a
voltage level less than 125 V AC/DC.
Small power Motors<1kW, lighting fixtures, power sockets, space heaters,
etc.
Site conditions The external factors, e.g. altitude, air temperature, wind
velocity, vibrations, relative humidity, etc., which may
influence the operation of an equipment.
Soft Starter It is a device that limits the initial inrush of current associated
with motor start-up. It provides a gentle ramp up to full speed
and is used only for start-up. Ramping up the voltage applied
to the motor produces this gradual start up.
Temporary installation It is defined as a time-constrained installation (e.g. facilities
for construction/commissioning activities).
Voltage Levels The following definitions regarding Low, Medium, High Voltage
levels are applied. Even if international IEC/EN standard
defines LV for levels up to 1 kV AC and HV for levels over 1kV
AC, for compatibility within Eni documents the following
definitions are maintained:
- LV for voltages up to 1 kV in AC (Low Voltage) ;
- MV for voltages over 1 kV in AC and up to 52 kV in AC
(Medium Voltage) ;
- HV for voltages over 52 kV in AC (High Voltage).
For symbols and abbreviations reference is made to the Normative References listed in 1.2.
Moreover the following are defined:
- AC Alternating Current;
- ACB Air Circuit Breaker;
- AFWF Air Forced Water Forced
- AGM Absorbed Glass Mat;
- AIS Air Insulated Switchgear;
- ASP Auxiliary Service Panel;
- CENELEC Comité Européen de Normalisation en Electronique et en
Electrotechnique;
- CE Conformité Européenne;
- COP continuous power;
- CT Current Transformer;
- DC Direct Current;
- DOL Direct-on-Line;
- DCS Distributed Control System;
- D.D.S. Document Data Sheet;
- EMS Electrical Management System;
- EPL Equipment Protection Level (see IEC 60079-0);
- ESP emergency standby power
- EU European Union;
- FCL Fault Current limiter
- FEED Front End Engineering Design;
- F&G Fire and Gas System;
- FLNG Floating Liquefied Natural Gas;
- FPSO Floating Production Storage and Offloading;
- GIS Gas Insulated Switchgear;
- GRP Glass Reinforced Polyester;
- HSE Health, Safety and Environment;
- HV High Voltage;
- HVAC Heating, Ventilation, & Air Conditioning;
- Ic capacitive current;
- ICSS Integrated Control and Safety System;
- Icw Rated short-time withstand current;
- I.D.S. Inspection Data Sheet;
- IEC International Electrotechnical Commission;
- In Rated Current;
- IOGP International Association of Oil & Gas Producers;
- IP Ingress Protection degree
- Ip arc permissible short-circuit current under arcing conditions
- Ips arc permissible short-circuit current under self-extinguishing arcing
conditions
- Ir resistive current;
- ISO International Standards Organisation;
- IT See IEC 60364-1 (onshore) and IEC 61892-2 (offshore)
- LCCA Life Cycle Cost Analysis
- LP Lighting distribution Panel;
- LPL Lightning Protection Level (see IEC 62305-1)
- LSS Load Shedding System;
- LV Low Voltage;
- MCB Miniature Circuit Breaker;
- MCC Motor Control Centre;
- MCT Multi-Cable Transits;
- MV Medium Voltage;
For graphic symbols, codes and identification tags reference shall be made to COMPANY standards
21000.ENG.PRC.STD and IEC 60617. Additional requirements shall be indicated in the Project
Documentation.
OPERATIVE ENVIRONMENT
Rating of equipment and systems shall comply with the range of ambient conditions (e.g.
temperature, humidity) indicated in relevant project documentation (e.g. Basis of Design).
Equipment that have to remain operational in case of partial or total shut down of HVAC shall
also be rated for the ambient conditions that can occur with such partial or total shutdown of the
HVAC.
MEASUREMENT UNITS
The measurement units adopted shall conform to the International System (S.I.) and COMPANY
Standard 20183.VAR.GEN.STD.
By exception, for cable conduits diameters and fittings in general the measurement in "inch"
may be used.
For all equipment (e.g. for generators, motors, adjustable speed electrical power drive systems,
MV and LV switchgear, UPS equipment and transformers), the CONTRACTOR shall provide as a
minimum the VENDOR's test reports in accordance with the equipment Inspection data sheet
(I.D.S.).
Certificate and test for equipment and materials for use in hazardous areas shall comply with
IECEx System Directives or with European ATEX Directive 2014/34/EU.
Overall design shall consider the reduction in energy consumption through the selection and
utilization of efficient electrical equipment. The use of high efficiency/power factor electric drives,
the use of adjustable speed electrical power drive systems for speed, flow or power control, the
selection of transformers with reduced losses, etc. shall be evaluated in terms of LCCA.
2.7.1 General
The electrical system design (generation and distribution philosophy, voltage levels selection,
equipment sizing, selection of type and characteristics for each component) shall be determined
by a technical and economic analysis considering the following factors:
• People Safety;
• Plant safe operation;
• Energy efficiency opportunities;
• Plant power demand;
• Single loads absorbed power and location;
• Availability and quality of power from external network, if available;
• Reliability of supply related to load classification;
• Reduction of equipment footprint and weight (especially in offshore installations);
• Environmental site conditions;
• Easy access for operation and maintenance;
• Flexibility for future expansions;
• Standardisation and availability of components;
• Integration with existing plant and uniformity with previous system design.
Loads shall be classified based on their required level of availability and reliability and
consequently the appropriate power supply shall be selected. Loads classification is shown in
TABLE 4.
Notes:
(1) Power supply of these users is required for technical reasons and therefore for reasons different from
those of providing personnel safety.
(2) Essential generation is normally required for floaters or for large manned offshore installations.
A schedule of the foreseen electrical loads, split by relevant supplying switchgear shall be
prepared. The load balance shall provide the demand load and peak load expressed in kilowatts
and kilovars, under the specified operating conditions identified during the project development.
The definitions are the following:
Demand Load Continuous Load + Intermittent Load
Peak Load Demand Load + % Stand-by Load
2.7.2.3 Rated voltage levels and maximum voltage for the equipment
Rated voltage and maximum voltage levels for the equipment shall be as per TABLE 5.
TABLE 5: Rated Voltage and maximum voltage levels for the equipment
The levels of generation and supply voltage for equipment and final users shall be selected
according to the criteria indicated in TABLE 6.
Electric system components shall be sized in such a way that maximum voltage drops, in steady
state operating conditions, never exceed the following values:
From main generator/transformer to MV
or LV switchgear 2% at rated current of generator;
From MV switchgear to MV switchgear 1% at rated current of downstream
switchgear;
MV overhead and buried transmission lines 5% at rated power;
MV motor feeder cables 3% for normal running at motor rated
current;
From transformer to LV switchgear 2% at rated current of transformer;
From LV switchgear to LV switchgear 1% at rated current of switchgear;
LV motor feeder cables 5% for normal running at motor rated
current;
Lighting circuits/small power users 3% from distribution board to last end user;
AC UPS circuits 5% at rated load (at the end user).
Between batteries and UPS 2%, with maximum between boost charge
current and the maximum direct current that
the inverter can absorb, increased of 25%
In steady state conditions, the sum of voltage drops of the various sections of a circuit, from the
power source / transformer to the terminals of the final load, shall be less or equal to 5 % of the
rated voltage of the circuit itself.
The voltage drop at MV switchgear shall not exceed 10% during motor starting.
The voltage drop at LV switchgear shall not exceed 15% during motor starting.
Under steady-state conditions, the voltage at generator and users terminals shall not deviate
from the rated equipment voltage by more than 5 % and the system frequency shall not deviate
from the rated frequency by more than 2 %. The combined voltage and frequency deviations
shall lie within Zone A as described in IEC 60034-1.
All loads shall be balanced so that the negative phase sequence components of voltage and
current at any point in the system shall not exceed the values quoted in IEC 60034-1.
Transient voltage deviations occurring at switchgear busbars during motor or group motor
starting/reacceleration shall be such as to maintain a minimum of 85% voltage on switchgear
busbars, and at least 80 %, but not more than 110 %, of rated equipment voltage on all other
users.
During motor or group motor starting/reacceleration, the voltage at the motor terminals shall
not deviate by more than +10 % or –20 % from rated equipment voltage.
Notwithstanding the above requirements, the limits set by the external power SUPPLIER
regarding the maximum voltage deviations that a consumer is permitted to cause at the point
of common coupling, e.g. due to the starting of electric motors, shall be adhered to.
The maximum current values (rated and short circuit currents) of the switchgear (main bus-
bars) shall be as per recommended values in TABLE 7.
The values are relevant to switchgears with single bus bar configuration.
TABLE 7: Maximum current and rated power on switchgears bus-bars
MAIN BUS-BAR
SHORT
RATED CURRENT
SWITCHGEAR CIRCUIT
RATED VOLTAGE [In]
TYPE CURRENT [Icw]
(1)
MV switchgear From 6 kV to 13,8 kV 4000 A 50 kA
MV switchgear From 20 kV to 35 kV 2500 A 31.5 kA
MV MCC 6 kV / 6,6 kV 1250 A 31.5 kA
Power Centre 0,4 kV/0,44 kV/0,48 kV 4000 A 100 kA
Power Centre 0,69 kV 4000 A 75 kA
LV MCC 0,4 kV/0,44 kV/0,48 kV 1250 A 75 kA
LV MCC 0,69 kV 1250 A 50 kA
ASP 0,4 kV/0,44 kV/0,48 kV 800 A 20 kA
Notes:
1) Site condition
In case of connection to an external network (except for more stringent requirements by the
external power SUPPLIER itself), the overall system power factor in steady state operating
conditions, inclusive of reactive power losses in transformers and other distribution system
equipment, shall not be less than 0,92 lagging.
In case of self-generation the power factor shall remain over 0,8 lagging, otherwise a power
factor correction system shall be provided.
Power factor correction shall be achieved by one or more of the following methods stated in
order of preference. The method selected depends on reliability and economic considerations:
1) permanently energised static capacitor banks connected to MV switchgears;
2) variation of the excitation of synchronous generators;
3) variation of the excitation of synchronous motors;
4) permanently energised static capacitor banks connected to distribution switchgears
(Power Centre).
The individual harmonic voltage distortions at any point of the system shall not exceed the levels
as defined in IEC/TR 61000-3-6 table 1. The Total Harmonic Distortion (THD) shall not exceed
8%. At MV switchgear incomers, the planning levels indicated in IEC/TR 61000-3-6, table 2 shall
not be exceeded, and the Total Harmonic Distortion (THD) shall not exceed 6,5%.
Such requirements shall be satisfied with the main power sources designated as spares in shut
down. In case of connection to an external grid in parallel with local main power generation, the
requirements shall be satisfied also when all the main power generators are in shut down. On
emergency distribution, such requirements shall be satisfied also when fed by the emergency
power source.
In case of connection to external grid, the requirements of the energy SUPPLIER shall be
respected if more stringent.
The electronic devices shall be suitable for electromagnetic environment class 2 according to IEC
61000-2-4.
Equipment shall be capable to operate continuously in the conditions present on the network at
point of installation, considering also emergency conditions such as operation with emergency
power source.
Connection of two or more neutral earthing resistors in the same electrically separated system
(e.g. with bus tie closed) shall be prohibited by means of an interlock that shall be active even
in case the control logic is not operational.
In case the generators are connected to the switchgear by means of step up transformers, each
generator shall be provided with its own neutral earthing resistor, that shall always be connected
during operation. The neutral earthing on switchgear side, if the switchgear is in MV, shall be as
per point b) above.
If a switchgear can be fed simultaneously by transformers and generators, solution b) above
shall be adopted.
Control logics used to manage the connection of the neutral earthing resistors, or of the neutral
earthing transformers, shall be hardwired and shall have the following functions:
• They shall be operational even in case of fault of the single generators.
• Opening or closing of circuit breakers, contactors or switches shall not leave each
electrically separated system without earthing resistors connected. The logic shall
automatically execute the commands to bring the system in an acceptable configuration.
• It shall be possible for the operator to disable the control logic, but in such a case an
alarm shall be raised to the EMS. An alarm to the EMS shall be raised also in all the cases
in which, for any reason, the neutral is isolated.
The status of the connection of neutral earthing resistors and neutral earthing transformers shall
be visible in the EMS graphic pages.
In case solution b) is adopted, control logics used to manage the connection of the neutral
earthing resistors shall be implemented in the switchgear to which generators are connected.
A back-up protection sensible to voltage unbalance (such as 59N) shall be provided in order to
cover possible faults while the neutral is isolated, for example if the logic malfunctions.
For parts of the network connected to an external electrical energy SUPPLIER without interposed
transformers, the neutral earthing philosophy of the external network shall be adopted.
2.7.5.2 LV systems
The neutral of LV electrical systems shall be solidly earthed at each source of supply by means
of dedicated earth electrodes that have a direct, low impedance connection to the plant main
earth grid. The system of earthing shall be designated “TN-S”, in accordance with IEC 60364.
TABLE 8 shows the typical connection among generators / transformer / switchgear / users:
TABLE 8: System earthing selection guide
LV Generator PC TN 4 (R-S-T-PEN)
MV/LV Power
PC TN 4 (R-S-T-PEN)
transformer
PC MCC TN-S 4 (R-S-T-PE)
PC PMCC TN-S 5 (R-S-T-N-PE)
LV/LV
ASP TN 4 (R-S-T-PEN)
Power Transformer
MCC Users TN-S 4 (R-S-T-PE)
PMCC-ASP Users TN-S 5 (R-S-T-N-PE)
Note: According to IEC 60079-14, the TN-C system earthing is not permitted in hazardous area.
2.7.5.2.2 Typical interconnecting between MV/LV Power Transformer and Main Switchboard
2.7.5.2.3 Typical interconnecting between LV/LV Power Transformer and Main Switchboard
Further references concerning low voltage typical incoming / outgoing feeders are in paragraph
2.8.4.3.
AC UPS systems shall have neutral isolated not distributed (IT system), provided with an
insulation monitoring device. Such device shall raise an alarm to the EMS in case of earth fault.
The faulty feeder shall be identified by visual indication on the front of the UPS distribution
section or distribution board.
This shall apply both to phase to phase and to three phase systems.
Double radial distribution shall be applied for all power distribution systems inside plants,
according to TABLE 9, with exception for local panels within packages, skids and buildings.
SYSTEM CONFIGURATION
Note: (1) With single busbar even if fed with two incomers
The coordination and selectivity among protections devices shall be guaranteed in order to avoid
unnecessary trips in case of fault. The coordination and selectivity study shall be implemented
considering that the failure downstream of any protection device in a switchgear shall not
compromise the power supply to other feeders.
The protection relays shall be equipped with a separate lock out relay (K86) with local manual
reset.
Electrical protections shall be provided with a separate power supply from UPS 230V AC.
Incomers and feeders of LV and MV switchgears shall be equipped with hardwired trip contacts
activated by a dedicated SIS signal in order to open the involved circuit breaker or contactor.
This signal shall be permanent type and resettable only by SIS system. If the circuit breaker or
contactor is already open, the trip signal shall inhibit its closure.
For ASP and UPS distribution boards, hardwired trip contacts activated by dedicated SIS signals
shall be foreseen, in order to disconnect single users or groups of users. These signals shall be
permanent type and resettable only by SIS system. If the circuit breaker or contactor is already
open, the trip signal shall inhibit its closure.
For all electrical equipment that use cooling with water (e.g. large MV motors or generators in
offshore, AFWF transformers) alarm against water leakage shall be provided.
All equipment shall be capable to withstand the effects of short circuits as a minimum for the
time necessary for the intervention of the protections.
For the calculation of the maximum short circuit current, the maximum values of the voltage
factor c shall not be lower than recommended in IEC 60909-0. Maximum short circuit currents
shall be calculated with all main power generators including spares connected, and external grid
if any, plus emergency power generators working in parallel.
Short circuit currents momentarily exceeding the design rating of the installation are permitted
only for make-before-break switching operation between incomers and bus tie circuit breakers
of a switchgear. In such a case, the configuration of the circuit breakers shall be in the conditions
in which the short circuit current rating is exceeded only for the period necessary for the
switching operation.
All circuits shall be protected against short circuits, with the exception of the connection of
starting batteries to engine for emergency machinery, such as emergency generators or fire-
fighting pumps.
The use of protective device with a short-circuit breaking or making capacity lower than
maximum prospective short-circuit at the point where it is installed (Backup Protection) shall not
be permitted.
A destructive fault current limited (FCL) in new installation (“green field”) shall not be permitted;
in case of revamping (“brown field”), the use of FCL may be permitted upon COMPANY approval.
In LV, TN and TT systems, switches with associated residual current relays shall be used for the
protection against indirect contacts of the final users.
In LV IT system, in case the protection against indirect contact is performed by means of
magneto-thermic switches, the impedance Zg of fault loop shall be verified.
The protections shall intervene also in case of minimum short circuit at the end of the line.
In TN systems, all incomers directly fed from generators or transformers and all feeders shall be
provided with protections against earth fault.
Motors rated 3 MW and over shall be provided with motor differential protection (87M), phase
shifting type.
Overloads protections shall be provided for all the circuits with the exclusion of:
• rotating machines excitation circuits;
• lifting electromagnets supply circuits;
• current transformers secondary circuits;
• connection of batteries to UPS or to engine starting systems;
• equipment that for safety reasons have to operate even in case of overload, such as fire-
fighting pumps and emergency diesel generators. However, such equipment shall be
protected against overload when operated for testing purposes.
As per relevant COMPANY standards (see par. 2.8.4.1 for MV switchgear and 2.8.4.2.3 for LV
switchgear) inter-tripping function between upstream and downstream circuit breakers (i.e.
power transformer outgoing feeder on MV switchgear and power transformer incomer on LV
Power Centre) shall be foreseen.
A key interlock shall be provided in MV switchgear between each earthing switch installed on the
front and the removable cover or door on the rear corresponding to the same functional unit, in
such a way that it shall be impossible to remove the cover or door unless the earthing switch is
in earthed position.
A key interlock shall be provided between earthing switch on MV switchgear feeder and
removable cover or door related to potentially live parts of the functional unit of the
corresponding LV incomer, in such a way that it shall be impossible to remove the cover or door
unless the earthing switch is in earthed position.
For LV switchgear located in different rooms, a key interlock shall be provided between LV feeder
and removable cover or door related to potentially live parts of the functional unit of the
corresponding LV incomer, in such a way that it shall be impossible to remove the cover or door
unless the upstream feeder is open, and withdrawn if applicable.
An interlock shall be foreseen between earthing switch on an incomer and corresponding feeder
on upstream switchgear, in order to avoid the risk of energization of an earthed circuit.
An interlock shall inhibit the starting, crank and slow roll of a generator if the switchgear incomer
to which it is connected has the earthing switch in earthed position.
A key interlock between the generator and the earthing switch of the corresponding switchgear
generator incomer shall inhibit the closure of the earthing switch when the generator is not
completely stopped, in order to avoid the risk of energization of an earthed circuit.
Electrical interlocks and intertrips shall be hardwired. The use of IEC 61850 for the purpose shall
be subject to the COMPANY approval and to the demonstration of its functionality during the
integrated factory acceptance test among EMS and related switchgear.
Electrical interlocks shall be fail safe.
Earthing and equipotential bonding requirements and recommendations of IEC 62305-3 and IEC
62305-4 shall be applied.
For the provision of SPD, the requirements and the recommendations of IEC 62305-4, including
Annexes C and D, shall be followed.
The lightning protection system for electronic devices is described in the COMPANY standard
20531.ENG.STA.STD.
The emergency electrical system shall be able to feed all the users classified as preferential and
safety.
The emergency power generation system shall be physically separated from the main power
generation source and shall be able to provide energy (including connection to switchgear) to
the system without relying on external auxiliary systems. Cooling by means of a source external
to the package, such as process water or sea water, shall not be permitted.
The emergency electrical distribution shall be derived from the main distribution system and
shall be supplied by an additional back-up power supply, consisting in an automatically started
emergency diesel engine generator.
The number of emergency diesel generators may be more than one in a facility.
Emergency power generation shall be in low voltage, with each generator with a maximum power
rating of 3150 kVA at a power factor of 0,8 lagging, according to the definition of ISO 8528-1.
Emergency power distribution shall be realized according to LVS 906 or LVS 905 of
28880.ENG.ELE.STD.
In case of main supply failure, the power supply to all emergency users shall be guaranteed
within 3 minutes.
To guarantee a stable and reliable emergency system, an automatic time sequence to energize
the loads shall be foreseen.
Distance between emergency diesel generator and relevant substation shall not be higher than
30m.
If different stand-alone emergency systems are foreseen, each emergency diesel generator shall
be located close to the relevant substation.
If the emergency absorbed power is limited, the emergency generation system may be powered
by a UPS with back-up batteries.
After main power generation restart, parallel between the emergency generator and the main
one shall allow the transfer of the load without any supply interruption.
The supply of safety users shall be guaranteed by a UPS with back-up batteries.
The apparent power of the emergency generator shall not be less than twice the sum of the
rated apparent output powers of all the UPSs. Only one out of two redundant UPS units shall be
counted for this purpose.
Black start facilities shall be provided. Black start philosophy shall be developed by focusing on
relevant equipment selection, location criteria and black start sequence.
The override of the SIS trip signals which are necessary for the plant black start shall be achieved
with an auto-reset logic circuit, commanded with a local device. The SIS trip signals override
shall be auto-reset upon SIS reactivation.
If the SIS signal override is active, an alarm shall be raised to the EMS and to the SIS, with
indication of the involved device, and in front of the involved equipment.
For electrical system calculation reports and studies during each phase of the project refer to
COMPANY Standard 20231.ENG.ELE.PRG.
Transformers with the same rated power that feed the same switchgear shall have the same
short circuit impedance, within tolerance limits.
Insulation class and maximum temperature rise for machines shall be according to Table 10.
TABLE 10: Insulation classes and temperature rise limits
Note 1: For LV/LV transformers, class of insulation H with temperature rise limited to 125 K is
also acceptable.
Note 2: maximum limits of absolute temperature indicated for each class shall consider the
corrections indicated in referenced standards, in particular regarding ambient temperatures
exceeding standard operating conditions.
In case of installation in hazardous area, the electrical equipment shall be selected and installed
in accordance with IEC 60079 series.
The following criteria shall be used:
a) LV motors, for both Zone 1 and Zone 2, shall have level of protection “db” “eb” or “eb”.
b) For both Zone 1 and Zone 2, MV motors shall have type of protection “eb” or “db” “eb”.
If such type of protection is not available, level of protection “pxb” or “pxb” “eb” shall be
used. In such a case, in the conditions when the IEC 60079-14 foresees alarm only in
case of loss of pressurization, the equipment shall also be switched off. Type of protection
“p” shall be however avoided for preferential users.
c) For luminaires, the requirements of 28914.ENG.ELE.STD shall be complied with. In
addition, lighting fixtures with integrated battery shall always be certified EPL “Gb” as a
minimum, including local accessories and junction boxes. Outdoors, emergency escape
lighting shall always be certified EPL “Gc” as a minimum, including local accessories and
junction boxes.
d) For junction boxes, socket outlets and plugs, motor control stations and cable glands, the
requirements of 28915.ENG.ELE.STD shall be complied with.
e) For bulk materials not comprised in 28914.ENG.ELE.STD or 28915.ENG.ELE.STD, the
minimum protection degree shall be IP55 for outdoor and IP44 for indoor.
f) Battery isolator box shall have level of protection “db” “eb”, in all installation locations.
g) Other equipment not listed above (such as switchgear and panels) shall have level of
protection “eb” or “db” “eb” for Zone 1 and Zone 2.
h) if level of protection “db” is used, the terminal boxes shall be protected “eb” (e.g. indirect
cable entry protection “db” “eb”).
In case of presence of dust or possibility of sand storms, outdoor equipment and bulk materials
shall be rated for IP65 or IP66, with exception of oil transformers.
If installed in non-hazardous areas, electrical bulk materials shall be industrial type as a
minimum.
The main electric system shall be able to supply all the users installed in the plant.
Its sizing shall consider:
• Total absorbed power calculated considering the total installed power with the use of
coefficients to consider actual utilization factor for each load, kind of service and the
operating contemporaneity;
• Presence of particular users such as large motors or other critical users;
• Availability of spares and allowance for future extensions.
The connection to external network in parallel with a self-generation system is permitted.
External network incomer, if required to operate in parallel with own plant generation, shall be
provided with:
• manual synchronising facilities;
• check synchronising relay;
• dead-bar override;
• bidirectional measurement (e.g. active and reactive power and energy)
• directional protection.
The above synchronising controls shall be located where control of the frequency and voltage of
the generators is exercised.
An islanding system shall be incorporated in the design. Provision shall be made to allow re-
synchronisation of islanded system with external network.
CONTRACTOR shall comply with the requirements imposed by the external power SUPPLIER (e.g.
power factor, sectioning and measuring equipment, protections, fiscal metering)
The generators selection (number and rating) shall consider the spare philosophy and, in case
of offshore plants, the space and weight constrains.
Configurations shall be with N+1 generators (with N ≥ 2), with N generators capable to cover
the load balance in worst conditions, with the margins defined at par. 2.7.2.2.
The solution with two generators only (1+1) may be accepted in particular cases after an
assessment to be approved by COMPANY against the above typical configurations in terms of at
least:
• performances of electrical system in term of reliability and functionality;
• generator utilization in different load scenarios.
The power rating of the generating sets shall be sized for continuous service in the whole range
of operating site conditions.
The rating, type and characteristics of the generating set shall fulfil the functional requirements,
as example operating in island mode, in parallel with other generating sets, in parallel with an
external power SUPPLIER or any combination of these.
The kW rating of the alternator in continuous service shall be higher than the output of the prime
mover, in the whole range of operating site conditions.
The generator rated power factor shall be 0,8 lagging unless otherwise specified in the project
documents.
During normal operation, the utilization coefficient of single generators shall never exceed 0,9
and never go below 0,5 for gas engine and 0.3 for turbo-generators, if not otherwise indicated
by VENDOR.
For further information on gas turbine generators, reference shall be made to the COMPANY
Standard 03778.ENG.ELE.STD.
The emergency diesel generator shall be sized considering the emergency loads.
No sparing philosophy is required.
Facilities shall be provided for periodic offload and on-load test.
According to ISO 8528 series, the RICE Emergency Diesel generator set shall be in accordance
with TABLE 12:
2.8.4 Switchgears
The use of switching devices in parallel to achieve the required rating is not permitted.
Nameplates and labels for switchgear to be installed indoors shall be in plastic with embossed
letters.
Nameplates and labels for switchgear to be installed outdoors shall be in AISI 316L with engraved
letters.
Base frame, accessories for switchgear and controlgear clamping, lift pad eyes or equivalent
devices, shall be provided.
If the motor starters are equipped with circuit breaker only (no contactor), an undervoltage coil
shall be foreseen.
Switchgear auxiliary power supply for space heaters, sockets and maintenance lighting shall be
provided from ASP.
Auxiliary power supply for control, logic, opening and closing circuits, protections, digital
instruments, signalling lights and spring charging motors of switchgears shall be fed by 230V AC
UPS, with the only possible exception of contactors for LV switchgears.
If switchgears are installed outdoors, the minimum protection degree shall be IP 55.
2.8.4.1 MV Switchgears
The use of GIS (Gas Insulated Switchgear) is permitted only for rated voltages of the system of
20 kV and over.
MV switchgears shall comply with IOGP S-620 “Supplementary Specification to IEC 62271-200
High-voltage switchgear and controlgear”.
The “circuit schedule” mentioned in IOGP S-620 shall be included in COMPANY form
MOD.ELE.MVS.001.
AIS assemblies shall comply with 28881.ENG.ELE.STD.
VTs shall be withdrawable for all air insulated switchgear and controlgear.
The accuracy class of CTs used for differential protection shall be indicated in project
documentation.
As a minimum, 10% unused spare terminals for control and auxiliaries shall be provided.
Terminals of amperometric circuits between CT, protection devices, control devices, and all
amperometric terminals of strips for external connections, shall be short-circuitable,
disconnectable and with a socket for portable instrument prods.
Unused CT secondary circuits and additional connection sockets shall be connected to the exit
terminal blocks. Unused amperometric terminals shall be short circuited.
Terminals of voltmetric circuits between VT, protection devices, control devices, and all terminal
blocks for external connections, shall be sectionable.
Simulation test to validate the interfaces with the EMS shall be performed, as described in IOGP
S-620.
2.8.4.2 LV Switchgears
Low voltage switchgears shall comply with IOGP S-560 “Supplementary Requirements to IEC
61439-1 & 2 LV Switchgear & Controlgear”, with the additional requirements indicated in
2.8.4.2.1 (all LV switchgears), 2.8.4.2.2 (all LV switchgears), 2.8.4.2.3 (all LV switchgears with
exception of HVAC switchgears), 2.8.4.2.4 (HVAC switchgears).
IOGP S-560 shall also be used for lighting and small power distribution boards rated less than
250A, with the indications included in 2.8.4.2.3.
• Auxiliary services of switchgear that are not fed by UPS, such as sockets, internal lighting,
space heater circuits.
The lighting distribution panels shall be used to feed the lighting system.
The maximum rating of panels shall be as indicated in TABLE 7.
If the maximum calculated short circuit current on the ASP is higher that the relevant maximum
short circuit current included in TABLE 7, insulation transformers shall be provided in order to
reduce the ASP short circuit current rating and to use modular switches with a short circuit
withstanding current up to the value indicated in the TABLE 7.
HVAC switchgear
Switchgear dedicated to HVAC loads and provided by HVAC SUPPLIER. The present document
refers only to power distribution part, for control section of HVAC refer to 20456.ENG.STA.STD.
For feeders of the PC type and for PC, MCC, PMCC incomers without ACBs, the following solutions
are permitted:
• Only the circuit breaker is withdrawable; or
• The whole functional unit is withdrawable.
For functional units with ACB, for feeders of the PC type and for switchgear incomers the term
“withdrawable” in the Data Sheets shall refer to the circuit breaker only, unless otherwise
indicated in the “Additional notes” column.
For each LV switchgear of PMCC and MCC type, in addition to the provisions already foreseen for
future development phases, for each busbar, at least 10% fully equipped spare MCC drawers
shall be provided, with a minimum of two spare drawers and of rating equal to the maximum
already present. In case the switchgear has more than one busbar, spares shall be distributed
in such a way that drawers of the same size are as evenly distributed as possible between
busbars.
For each LV switchgear of PC and PMCC type, in addition to the provisions already foreseen for
future development phases, for each busbar, at least one fully equipped spare feeder shall be
provided. The spares shall be feeders to ASP (LVS 530/535 of 28880.ENG.ELE.STD). The rating
shall be equal to the maximum already installed of the same typology, or 630A if the same
typology is not present.
For each ASP and low voltage distribution boards, including UPS distribution sections and
distribution boards, 20% fully equipped spare feeders shall be provided, with at least one for
each rating.
For ratings of 800A and over, ACBs shall be used.
The communication of protection relays and multimeters shall comply with 20180.ENG.ELE.STD.
Switching devices shall switch all phases or poles, with the exceptions indicated in
28880.ENG.ELE.STD.
MCBs that feed external circuits, with the exception of motor space heaters, shall be operable
from the front of the PSC-Assembly without need of opening the door. Covers may be used over
MCBs providing that after the removal of these the degree of protection is not lower than IP2X.
For local distribution panels in IT systems not directly fed from transformers, it is not mandatory
to have an insulation monitoring and earth fault detection system as described in subclause
8.5.3.111 of IOGP S-560, providing that automatic location of earth faults for individual outgoing
circuits is available in the upstream PSC-Assembly.
Indicator light colour coding shall be in accordance with 28880.ENG.ELE.STD for PSC-Assemblies
other than UPS distribution boards and UPS distribution sections.
Indicator light colour coding shall be in accordance with 28882.ENG.ELE.STD for AC UPS
distribution boards and AC UPS distribution sections.
Form of internal separation for ACB functional units shall be 4b.
Form of internal separation for PC, PMCC, MCC functional units other than ACBs shall be 3b as a
minimum.
For ASP and LP, for UPS distribution boards and UPS distribution sections, and for local
distribution panels, the minimum form of internal separation shall be 2b, with exception of local
distribution panels rated less than 250A, for which also 2a is permitted.
The distances indicated in mm in subclause 8.8 of IOGP S-560 are not mandatory for local
distribution panels rated less than 250A.
If normal and emergency HVAC loads are fed by the same switchgear (permitted only onshore),
means to disconnect and to inhibit starting of non-emergency loads shall be foreseen upon
unavailability of main power source.
Devices for operation, such as stop buttons, shall be placed on the front of the switchgear
(without necessity to open doors or covers).
For PSC-Assemblies with more than one incomer, protections to avoid the connection of
unsynchronized circuits shall be foreseen.
For motor and heater feeders, there shall always be the possibility to stop them from the front
of the switchgear.
Stop command shall be different than protection hand reset device.
For incomers, bus couplers and for feeders to subdistribution panels, possibility to open and
close from front of the switchgear shall be foreseen. In case remote operation is foreseen, it
shall be possible only by means of a local/remote selector located in front of the switchgear.
Possibility of opening the circuit shall be available regardless of the position of the local/remote
selector.
Incomers and bus ties shall be with circuit breakers.
PSC-Assemblies incomer functional units and bus coupler functional units (if any) shall be
withdrawable. Other functional units shall be as defined in the Data Sheet.
The term “withdrawable” in the Data Sheet shall be intended as follows:
• For all incomers and bus couplers and for feeders of the PC type, shall refer to the circuit
breaker only, unless otherwise indicated in the “Additional notes” column.
• For feeders of the MCC type, shall refer to the whole functional unit.
The minimum signaling mounted on front of the switchgears shall be as follows:
• Red lamp (trip) for each incomer / feeder;
• Green lamp (available) for each incomer /feeder;
• White lamp:
(closed) feeder;
(running) motor feeder.
If there is no visible evidence of the test or withdrawn position of a withdrawable part, such
condition (cumulative of test or withdrawn) shall be shown by means of blue lamp.
As a minimum, three phase voltage and current measurement shall be made available for each
incomer from the front of the PSC-Assembly.
Form of internal separation shall be 4b for ACBs.
Interface with EMS shall be as described in 20180.ENG.ELE.STD.
2.8.5.1 General
Power transformers, including LV/LV transformers, shall comply with IEC 60076 series.
In addition, they shall comply with IOGP S-720 “Supplementary Specification to IEC 60076-1
Transformers “.
The paint system applied to the transformer and its accessories shall provide protection against
the specific climatic conditions for the location of installation, in compliance with COMPANY
standard 29000.ENG.CPI.STD (offshore and coastal areas) or 29001.ENG.CPI.STD (onshore).
Anticondensation heaters, if provided (e.g. in cable box), shall be protected against direct contact
(IP2X) and in order to avoid burning if accidentally touched.
Winding temperature detectors shall be of platinum of 100 Ω at 0°C (PT100).
Space heater controlled with thermostat shall be provided in main cable boxes.
If cable connecting boxes are foreseen, these shall be separated for:
• High voltage side of the transformer
• Low voltage side of the transformer
• The auxiliary circuits of the transformers, such as CT secondaries and alarm/trip
measuring devices
• Forced cooling equipment terminals
• On load tap changer
• Neutral connection of transformers with secondary voltage > 1kV
Contacts shall be NC for alarm and NO for trip circuits.
All the power transformers (including LV/LV ones) shall be capable to sustain the thermal and
dynamic effects of short circuit, as specified in IEC 60076-5. The values of apparent short circuit
power of the network shall be used for the calculations. The ability to withstand the dynamic
effects of short circuit shall be demonstrated by calculations and design and manufacturer
considerations.
Rating plates shall be provided and made of stainless steel AISI 316L.
Junction boxes and control panels for auxiliary devices shall be rated IP44 if installed indoors (in
room enclosed on all sides), otherwise IP55. These shall be provided with space heaters
controlled with thermostat and protected with MCBs or with switch-disconnector-fuses. In case
motor starters are included, these shall be provided at least with protection with thermomagnetic
circuit breakers. Space heater terminals shall be provided with a warning label.
Transformers shall be provided with de-energized tap changer, with a tapping range of ±5% in
steps of 2,5%, unless on load tap changer is requested by COMPANY. In case on load tap changer
is foreseen, it shall be motorized and provided with remote control panel.
The protection degree of the remote control panel for on-load tap changer shall be IP 31 or
higher for indoor installation in room enclosed on all sides and IP 55 or higher in other cases.
The installation of power transformers inside switchboards is not permitted, including those used
to feed ASP or lighting and small power sections, with the exception of auxiliary transformers,
such as those used for UPS, that are treated as a component of the switchboard itself.
Two winding transformers with star connection both at primary and secondary windings shall be
rejected.
Power transformers connected to overhead lines or air insulated substations shall be protected
with surge arresters.
Transformers in series shall be accepted only for the following cases:
• If there is a preferential power generation in MV, for the transformers feeding preferential
loads;
• LV/LV transformer;
• If the LV loads are less than 20% of MV loads.
Autotransformers shall be permitted only if explicitly indicated in COMPANY standards.
For LV/LV transformers, the voltage ratio for the tappings other than the principal one may
exceed the tolerances of IEC 60076-1; in such a case, the voltage ratio of the tappings shall be
subject to agreement with COMPANY.
LV/LV transformers feeding ASP or lighting board shall not be rated more than 500 kVA.
Power transformers shall be dry type in resin, unless these have at least one winding rated more
than 36 kV, or power rating higher than 15 MVA. Over 15 MVA and up to 25 MVA, these may be
in oil or dry type in resin, providing that there are no windings rated more than 36 kV. Over 25
MVA, or if there are windings rated more than 36 kV, oil type shall be used.
In desert locations and wherever sand or dust storms are expected, dry type transformers in
resin may be used only up to 3,15 MVA. These shall be installed only indoors, in rooms
surrounded on all sides, with forced ambient ventilation. For sizes over 3,15 MVA, the
transformers shall be oil type. In such ambient conditions, oil type transformers may be used
also for power ratings of 3,15 MVA and below.
Power ratings indicated in this paragraph are referred to natural ventilation.
CONTRACTOR shall include in the project specification for the dry type reactors as indicated in
IEC 60076-6, the pollution conditions on the installation site. Lacking information, very heavy
pollution severity shall be assumed, according to the definitions of IEC TS 60815-1.
Magnetic clearance and protection from atmospheric effects shall be verified by CONTRACTOR
and VENDOR in relation to the conditions of installation. Demonstration that heating and reaction
forces induced in nearby metallic objects are negligible shall be provided. Verification shall also
consider the overheating of concrete rebars due to the interaction with electromagnetic fields
generated by reactors.
Dry type reactors shall be installed in a fenced area which shall be accessible, by means of
interlock, only when the equipment installed inside it are de-energized. Such fenced area shall
contain only the reactors and associated auxiliary equipment, if any. Reactors that are redundant
to each other shall not be installed in the same fenced area.
Oil immersed reactors shall be installed with the same requirements described in 2.10.1.2 and
3.1 for oil immersed transformers.
These shall comply with the same requirements indicated for oil immersed transformers in
2.8.5.3.
DC earth leakage monitoring shall be provided, with alarm on the UPS and on the EMS.
The UPS shall be interfaced with the EMS for monitoring purposes, as indicated in
20180.ENG.ELE.STD. The information to be shown in the EMS shall be as a minimum those listed
in IOGP S-701, § 8.4.2.5, § 8.4.3, § 8.4.4.2.
UPS distribution boards, if not integrated in the UPS, shall be interfaced with the EMS as ASP,
as indicated in 20180.ENG.ELE.STD.
UPS distribution board, if integrated in the UPS, shall as a minimum provide a common alarm
(cumulative of fault) to the EMS, plus the status and trip indication of the circuit breakers
upstream of the distribution bus bars.
UPS distribution board shall comply with IOGP S-560 and with 2.8.4.2 and subparagraphs of the
present document, both if integral to the UPS or separated from it.
If the UPS distribution board is not integral to the UPS, it shall be positioned in the same room
and as close as possible to it.
For the UPS distribution section, or distribution board, the COMPANY form MOD.ELE.LVS.001
shall be used.
The UPS shall respect the accessibility requirements indicated in subclause 8.5.5 of IEC 61439-
1.
Maximum height of the UPS shall be 2,5 m.
Protective treatments and surface finish colours shall be in accordance with the requirements
of the COMPANY specifications 29000.ENG.CPI.STD (offshore and coastal areas) or
29001.ENG.CPI.STD (onshore).
If redundant UPS configuration is used (i.e. UPS of type “B” or “C” according to
28882.ENG.ELE.STD), it shall be possible to replace components of a UPS unit keeping the other
UPS unit part of the redundant UPS configuration in service, without risk of accidental contact
with live parts.
Live parts of a redundant UPS that remain in service when one UPS unit is de-energized shall be
protected with barriers of at least IP2X with respect to an operator that is working on the de-
energized UPS unit.
The maintenance bypass switch and isolation transformer shall be mounted separately in an
adjacent compartment.
Cooling fans shall be replaceable while the UPS remains in service.
Battery isolator box shall be in AISI 316L or GRP.
Push buttons and manipulators shall comply with IEC 60073.
Fuses shall be used only when shown in 28882, or for protection of semiconductor devices if
strictly required by the Manufacturer.
On-line battery capacity testing shall be provided, to discharge the battery into the load.
With batteries at the discharge minimum voltage, the UPS shall allow the recharge of the battery
to at least 80% capacity in a period of maximum 10 hours.
The UPS shall allow a black start, delivering power to the users at the rated output with only the
batteries as power source.
The inverter section of the UPS shall deliver the short circuit current necessary to operate the
downstream protections in case of fault on an outgoing circuit.
If the UPS has two or more inverters to be operated in parallel, alarm of inverters not
synchronized shall be shown on the UPS front by means of HMI or LED signaling lights, and an
alarm shall be raised to the EMS.
If remote manual reset of trip functions is foreseen, this shall be performed from the EMS.
Each inverter shall be able to operate even if the batteries are disconnected and the power is
fed only by the relevant rectifier.
If there are motors among the loads of the UPS, the UPS motor starting capability shall be
verified in all possible operating configurations. In case the UPS is not capable of starting a
motor, adjustable speed electrical power drive system shall be provided for starting and
integrated in the UPS distribution board or UPS distribution section.
Temporized disconnection of loads with different autonomy times shall be as shown in
28882.ENG.ELE.STD.
For earth fault detection and alarm, refer to 2.7.5.3.
Coordination and selectivity of protections shall be guaranteed in such a way that a fault on a
single outgoing circuit does not compromise the power supply to other feeders.
Baseframe, lift pad eyes and accessories for UPS installation shall be provided.
For AC UPS rated more than 5 kVA, the incomer shall be three phase.
For AC UPS rated more than 120 kVA, the output shall be three phase.
Type A
The configuration with one UPS of type A is permitted only in case the loads to be fed are not
related to people safety or equipment integrity, and following specific COMPANY approval.
The configuration with two UPS of type A, may be used if it is required to have two fully
independent units in different locations. If the two UPS of type A are used also for loads that are
not fed through redundant AC/DC converters, the outputs of the two UPS shall be synchronized.
If there are loads with single power supply, these shall be fed from both UPS distribution boards.
An intermediate panel shall be provided with a break-before-make automatic transfer switch.
The inrush current of the loads shall be verified against the capacity of the inverter.
Type B
This configuration may be used for all electrical loads.
This configuration may be used for the instrumentation and telecom loads which do not require
redundant power supplies.
This configuration may be used if the electrical and instrumentation UPS are merged in one.
The inverter outputs shall be synchronized.
Type C
This configuration may be used only for instrument and telecom loads (such as DCS, SIS, F&G
etc.) which require redundant power supplies.
UPS distribution board, if integrated in the UPS, shall as a minimum provide a common alarm
(cumulative of fault) to the EMS, plus the status and trip indication of the circuit breakers
upstream of the distribution bus bars.
UPS distribution board shall comply with IOGP S-560 and with 2.8.4.2 and subparagraphs of the
present document, both if integral to the UPS or separated from it.
If the UPS distribution board is not integral to the UPS, it shall be positioned in the same room
and as close as possible to it.
For the UPS distribution section, or distribution board, the COMPANY form MOD.ELE.LVS.001
shall be used.
Protective treatments and surface finish colours shall be in accordance with the requirements
of the COMPANY specifications 29000.ENG.CPI.STD (offshore and coastal areas) or
29001.ENG.CPI.STD (onshore).
It shall be possible to replace components of a UPS unit keeping the other UPS unit part of the
parallel redundant DC UPS configuration in service, without risk of accidental contact with live
parts.
Live parts of a parallel redundant DC UPS that remain in service when one UPS unit is de-
energized shall be protected with barriers of at least IP2X with respect to an operator that is
working on the de-energized UPS unit.
Cooling fans shall be replaceable while the UPS remains in service.
Battery isolator box shall be in AISI 316L or GRP.
The UPS shall respect the accessibility requirements indicated in subclause 8.5.5 of IEC 61439-
1.
Maximum height of the UPS shall be 2,5 m.
Push buttons and manipulators shall comply with IEC 60073.
Fuses shall be used only for protection of semiconductor devices, if strictly required by the
Manufacturer.
On-line battery capacity testing shall be provided, to discharge the battery into the load.
With batteries at the discharge minimum voltage, the UPS shall allow the recharge of the battery
to at least 80% capacity in a period of maximum 10 hours.
Unless it is dedicated to feeding auxiliaries of non-emergency packages, the UPS shall allow a
black start, delivering power to the users at the rated output with only the batteries as power
source.
If remote manual reset of trip functions is foreseen, this shall be performed from the EMS.
The short circuit capability of the DC UPS shall be sufficient to operate the downstream
protections in case of fault on an outgoing circuit.
The UPS shall be able to operate even if the batteries are disconnected and the power is fed only
by the relevant rectifier.
Coordination and selectivity of protections shall be guaranteed in such a way that a fault on a
single outgoing circuit does not compromise the power supply to other feeders.
Temporized disconnection of loads with different autonomy times shall be foreseen.
Baseframe, lift pad eyes and accessories for UPS installation shall be provided.
Refer to opi hse 023 eni spa “Safety & Environmental Minimum Design Requirements”.
Batteries shall comply with IOGP S-740 “Specification for batteries (IEC)”.
Battery technology shall be one of the following:
• nickel-cadmium partial gas recombination, in accordance with IEC 62259
• valve-regulated lead-acid – AGM, in accordance with IEC 60896-22
• valve-regulated lead-acid – gel, in accordance with IEC 60896-22
Other battery technologies shall be subject to COMPANY approval.
Service life of batteries that are regularly under floating charge conditions, at the design ambient
temperature of the room in which they are installed, shall not be less than the following:
• 20 years for Ni-Cd batteries;
• 12 years for VRLA AGM batteries;
• 15 years for VRLA gel batteries;
Cells shall not require refilling during their service life.
The number of cells for UPS application shall be chosen in such a way that at the end of autonomy
time with the required load profile the DC voltage at UPS terminals is such as to guarantee that
the output of the UPS is within required limits.
For the single cells, values of rated voltage, gassing voltage and minimum voltage at the end of
discharge at 20°C shall be provided.
The elements cell containers of a battery shall be in totally or partially transparent material and
in a self-extinguishing material as per UL 94 (Standard for tests for flammability of plastic
materials for parts in devices and appliance).
The selection criteria of type of material cell (opaque or transparent) enclosure are the following:
• UL 94 class V0 (opaque) for offshore and floaters installation;
• UL 94 class HB (opaque or transparent) for onshore installation.
The batteries shall be installed into dedicated battery rooms. Exception is made for starting
battery sets installed on/close to generation set skid.
Other exceptions shall be subject to COMPANY approval (e.g. small offshore platform, etc.).
The required autonomy time shall be verified in the whole range of ambient temperatures,
including the case in which HVAC is not operational due to shutdown of main and emergency
power systems.
The containers shall bear the two polarity signs clearly visible near the respective poles.
The container of valve regulated batteries shall be provided with outlet valve, normally closed
to avoid oxygen entrance from external ambient.
Connecting bolts with anti-loosening device shall be used for inter-cell connections. Welded
connections shall not be accepted.
Battery terminals and electrical connections between cells, tiers and racks shall be insulated or
protected with covers in order to realize a protection against accidental contact with live parts
of at least IP 2X.
Tools required in IOGP S-740, subclause 9.2.1 shall be provided.
Commissioning charge, as per battery manufacturer recommendations, shall be possible with
one of the following solutions:
• With the UPS (for UPS batteries) or with the battery charger of the generator package
(for generator starting batteries)
• With a portable external battery charger, to be provided to COMPANY by CONTRACTOR
or VENDOR
If the weight of a single cell exceeds 25 kg, a battery lift or battery removal tool shall be provided.
Batteries for the UPS shall be on battery rack.
Battery rack shall be solidly fixed to the floor to avoid the falling of batteries.
Battery rack shall have a maximum of three tiers.
Maximum height of the rack, measured from the top of battery on the top tier to the floor, shall
be 1800 mm.
Material for battery rack shall be electrical insulation coated steel.
Material for battery rack shall be chemical resistant.
Battery rack shall be isolated from the ground.
Surface treatment of the rack shall comply with the requirements of the COMPANY specifications
29000.ENG.CPI.STD (offshore and coastal areas) or 29001.ENG.CPI.STD (onshore).
In FPSO and floaters, the batteries shall not spill electrolyte in the conditions indicated in IEC
61892-5 as the limits of inclination in which emergency machinery are required to operate.
For FPSO and floaters, the rack shall be anti-seismic.
For FPSO and floaters, the batteries and the rack shall not fall in the conditions indicated in IEC
61892-5 as the limits of inclination in which emergency machinery are required to operate.
Close to each battery rack a sectioning device (switch-disconnector or circuit breaker) shall be
provided, to isolate the rack for maintenance purposes.
MV asynchronous motors shall comply with IOGP S-704 “Supplementary Specification to IEC
60034-1 High Voltage Three-phase Cage Induction Motors”.
For interior locations, the degree of protection shall not be lower than IP 44.
If report from test on identical motor is not available, the test of noise level at no load shall be
performed.
Lateral analysis shall be performed for motors rated over 400 kW and for converter-fed motors.
Torsional analysis shall be performed for motors rated over 400 kW and for converter-fed
motors.
The sensors indicated in 28906.ENG.MEC.STD shall be provided.
Space heaters shall be provided for motor windings and for line conductor terminal box.
Motors shall have at least two ISO metric thread earthing terminals fitted externally on the
frame.
Components necessary for lifting and installation at site shall be provided (e.g. lifting lugs).
The use of magnetic bearings shall be subject to COMPANY approval.
Auxiliary fans and pumps driven by independent motor shall have a N+1 sparing philosophy and
in case of trip an alarm shall be raised to a manned location.
With reference to IOGP S-704, subclause 15.2, type test certification for use with converter shall
always be required for motors with type of protection “e”, according to IEC 60079-14.
Protective treatments and surface finish colours shall be in accordance with the requirements
of the COMPANY specifications 29000.ENG.CPI.STD (offshore and coastal areas) or
29001.ENG.CPI.STD (onshore).
Cooling methods based on water shall be acceptable for ratings of 2 MW and over in offshore,
and in other cases only following COMPANY approval.
LV asynchronous motors shall comply with IOGP S-703 “Supplementary Specification to IEC
60034-1 Low Voltage Three Phase Cage Induction Motors”.
Space heaters shall be provided.
For interior locations, the degree of protection shall not be lower than IP 44.
With reference to IOGP S-703, subclause 15.3, type test certification for use with converter shall
always be required for motors with type of protection “e”, according to IEC 60079-14.
Protective treatments and surface finish colours shall be in accordance with the requirements
of the COMPANY specifications 29000.ENG.CPI.STD (offshore and coastal areas) or
29001.ENG.CPI.STD (onshore).
Connections between equipment shall be realized by means of cables. The use of bus ducts and
cable bus may be considered on a case by case basis according to project requirements and
after COMPANY approval.
For outdoor installation the cables shall be mechanically protected over whole length by armour.
Cables shall be continuous; joints are not permitted, unless for particular cases to be specifically
approved by COMPANY. Junction boxes are permitted for lighting and small power circuits.
Single core Cables and multicore cables installed in ladder shall be fixed to ladder rungs with
cable cleats certified for the upstream calculated short circuit current. Single core cable shall be
fixed with trefoil cable cleats; in case of more than one core per phase each trefoil cleats shall
accommodate one core per phase.
All cables for onshore application (included internal wiring of switchgear and other enclosure for
electrical equipment) shall be in accordance with IEC 60502-1, IEC 60502-2, IEC 60840 and
shall be low smoke, halogen free and flame retardant, according to IEC 61034-2, IEC 60754-1,
IEC 60754-2 and IEC 60332-3-22.
Cables to be routed where there is risk of deposits or dripping of liquid hydrocarbons shall also
be hydrocarbon resistant, according to IEC 60811 series.
The following emergency/safety circuits shall be realized with low smoke, halogen free and fire
resistant cables, according to IEC 61034-2, IEC 60754-1, IEC 60754-2 and IEC 60331 series:
• Power and control of firefighting system
• Fire and gas detection system (1)
• Emergency escape lighting
• Interconnecting cables from battery to UPS
• Obstruction light
• Radio communication (1)
• Other emergency and critical loads defined in the project specification
Note (1): See also COMPANY Standard 28045.ENG.STA.PRG.
Even if indicated in The IEC 60502-1 and IEC 60502-2, the insulating compound “PVC/A” and
“PVC/B” listed in Table 2 is not permitted.
For lighting, small power and convenience sockets in indoor distribution, (e.g. Living quarter,
electrical rooms) according to IEC 60228, cables class 5 (flexible cables) or class 6 (more flexible
cable) shall be used.
The colors of cores of electrical cables shall be in accordance with IEC 60445. For cables with
one or two cores, the choice of colors of the cores shall be uniform within the facility.
The colors of outer sheath shall be:
• Black or gray for low voltage cables (up to 0.6/1 kV). However only one color shall be
used per facility.
• Black for electrical control cables
• Red, white or violet for Medium voltage cable (over 0.6/1 kV). For each voltage level
within a facility, only one color shall be used. For different voltage levels, different colors
shall be used.
• Yellow/green for earthing and protective cables
Fire resistant cables shall have specific color of outer sheath, different from the outer sheath of
power, control and earthing cables (e.g. orange).
Routine tests, sample tests, type tests, tests after installation shall be performed as per
indications of reference standards IEC 60502-1, IEC 60502-2, IEC 60840. Reports of the tests
shall be provided. Type tests already performed do not need to be repeated, if deemed
acceptable in referenced standards.
DC voltage test of the insulation shall be avoided.
In addition, reports of type tests as per IEC 60332-3-22, IEC 61034-2, IEC 60754-1, IEC 60754-
2 and, if corresponding characteristics are required, also IEC 60331 series and IEC 60811 series,
shall be provided.
Accessories for cables shall have been qualified as per IEC 60502-4, for the voltage range therein
indicated.
• containment of voltage drops within fixed values (steady-state and during transient), as
shown in 2.7.2.5.
• containment of temperatures within the limits allowed by the cable insulation at normal
operating current, at overload current and at short circuit current under actual installation
conditions, considering the fault clearance time of protective device. (Note 1)
• correct activation of upstream protections in function of the minimum impedance of the
fault circuit
Note 1:
Short circuit current is equal to calculated short circuit current plus 20%
In absence of project data, the fault clearance time of protective device is assumed equal
to:
• 0,5 sec. for Low Voltage system
• 1 sec. for Medium Voltage system
Sizing based on normal operation currents is executed considering the following criteria:
• cables connecting single equipment (such as generators, transformers, motors, heaters)
to the power switchgear shall be sized for the rated current of the equipment.
• cables connecting a switchgear to a sub-board (e.g. from PC to MCC) shall be sized for
the rated current of the sub-board busbar rated current.
• The power cables for socket circuits shall be sized as follows:
The main cable from the switchboard to each socket junction box shall be sized
according to its length, the number of sockets in the circuit taking in consideration
the diversity factor and considering at least n ° 1 socket (the farthest one) running
at full load (In).
The cable from JB to socket shall be sized according to socket rated current.
The power cables between battery accumulators and switchboard (AC or DC UPS) shall be sized
for the maximum between boost charge current (or maximum charging current, if boost charging
is not applicable to the battery) and the UPS rating on DC side considering the overload
capability, increased of 25%.
Moreover, the battery cables shall have the following characteristics:
• Single core cables
• Non-armoured type if the cable routing is within the same building (i.e. without outdoor
routing)
• Fire resistant in compliance with IEC 60331. Resistance to fire shall be 30 minutes or
more.
• External sheath with the requirement of “Resistance to chemicals and acids”
The system category of cables shall be “B” according to IEC 60502-1, IEC 60502-2.
The “C” system category shall be chosen in case the operating philosophy requires the continuity
of the electrical user with one phase earthed, or in case the system is not designed to open the
circuit on first earth fault.
Single core or multicore cables in parallel shall be used to avoid the use of cables with sections
higher than those indicated in paragraph 2.8.11.9.
The cables in parallel shall have the same impedance, the same length and the same section so
that the current is equally distributed on each cable.
Single core buried cables shall be fixed together with metal clamps.
For command cables, in case of cable routes of considerable length, the capacitance of cable and
voltage drop shall be considered to avoid relay malfunction.
All control/command multi-cables shall be selected by using VENDOR standard production with
number of cores greater than the number of cores actually needed, i.e. with the provision of
spare cores.
Cables in hazardous areas shall be armoured, for exceptions refer to paragraph 2.8.11.3.
All power and control cables installed outdoor shall be armoured-type; alternatively, the main
distribution cables of medium and low voltage, wholly installed in non-classified area, may be
non-armoured-type but shall be installed with appropriate mechanical protection and be
equivalent to the armour (i.e. cable tray with cover or conduit) for all extension up to equipment
terminal box entry.
If a cable route has a section in classified areas, precautions shall be taken to avoid the spread
of hazardous substances in a safe area; for example, cable trench with cover shall be filled with
sand or in the case of cableway in duct, they shall be properly sealed.
Cable armour shall be in tape, wire or sleeve, the choice depending on the section and the type
of flexibility required. In case of single core cables the armour material shall be non-magnetic
type.
Medium voltage cables, as well as control cables, shall be provided with screen.
The following tables show the recommended cross sections of cable conductors.
The choice of the maximum section shall consider the bending radius of cables in respect to the
available cable installation space.
Notes:
1) 300 mm2 is referred to offshore installation, 630 mm2 is referred to onshore installation
2) Ethernet cable excluded
Overhead transmission lines may be used to connect the plant with remote areas, outside of its
boundaries.
The requirements and recommendations of EN 50341-1 shall be followed.
Limits of exposure to electric and magnetic fields shall be as per national normatives and
regulations. If such limits are not defined in national normatives or regulations, the limits and
recommendations indicated in the Directive 2013/35/EU of the European Parliament and of the
Council shall be applicable.
To provide protection against atmospheric discharge on the overhead lines, surge arresters shall
be foreseen after the gantry structure (e.g. primary side of plant incoming transformer).
The OHTL shall be protected against lightning by means of earth wires that shall be sized in line
with the result of calculations that take in to account the value of expected lightning current.
Shielding of the line by means of earth wires shall be demonstrated by means of calculations.
The use of wooden supports for overhead lines is prohibited.
External painting of electrical equipment shall be in compliance with the COMPANY standard
29000.ENG.CPI.STD Appendix “A”, Table “A-2” (offshore and coastal areas) or
29001.ENG.CPI.STD Appendix “A”, Table ”A-2” (onshore).
Neutral earthing resistors and related testing activities shall comply with IEEE C37.52, including
the amendment issued in 2020. However, insulation levels and test voltages for applied voltage
tests shall be chosen according to highest voltages for equipment and standard rated short
duration power-frequency withstand voltages indicated in IEC 60071-1.
Reports of the test activities shall be provided.
Rated time of the resistors shall be 10 seconds.
The resistors shall be made of stainless steel.
The resistors shall be provided with removable links.
A contactor, circuit breaker or switch inside an enclosure (same enclosure ratings and access
protections as for NER, if different from it) shall be provided if it is necessary to have the
possibility to disconnect the resistor, in the cases indicated in 2.7.5.1. The switching device shall
be capable to be controlled (open/close and status monitoring) by a remote logic as per 2.7.5.1.
The earthing resistors shall be housed in a metallic enclosure providing a protection degree of a
minimum as follows:
• IP 23 for indoor installations in rooms enclosed on all sides
• IP 44 for installation in a room opened on one side to the outdoors, by means of grating
or louvers
• IP 55 in other cases
For offshore installations, and for onshore installations in aggressive environment (e.g. marine)
the enclosure shall be made of AISI 316L. In other onshore locations the enclosures shall be
made of galvanized steel.
Cable entrances shall be made of non-magnetic material.
External parts that can be touched by an operator shall not develop surface temperatures that
can result in burn hazards, both in normal operating conditions and in case of earth faults.
A mechanical interlock shall permit access to potentially live parts (i.e. when accessing to the
internal of the enclosure) only in case the resistor is de-energized, as well as the generator or
transformer to which it is connected.
An anti-condensation heater controlled by a thermostat or a self-regulating anti-condensation
heater shall be provided and protected on the feeding line by MCBs or with switch-disconnector-
fuses located in the junction box. Anticondensation heaters shall be protected against contact
(IP2X) and to avoid burning if accidentally touched.
Nameplates shall be engraved with writing on plates made of AISI 316L stainless steel. Related
accessories shall be made of the same material.
Junction boxes shall be provided for the connection of auxiliary circuits, such as space heaters
and amperometric circuits. These shall have protection degree minimum IP44 if installed indoors
in rooms enclosed on all sides, otherwise minimum IP55. Terminals remaining live when the
neutral earthing resistor is de-energized shall be provided with warning labels.
Current transformers for protection functions shall be provided inside the enclosure of the neutral
earthing resistor. Current transformers shall be installed upstream of the resistor. Current
transformer secondary neutral points shall be earthed via a disconnecting link. Current
transformer wiring connected to external circuits shall have shorting links located at the outgoing
terminals.
The resistors shall be provided with lifting eyebolts and accessories necessaries for installation
and maintenance.
Electrical requirements for electric process heaters shall be as per IOGP S-723 “Specification for
Electric Process Heaters”.
Regarding the power and control assembly, enclosures for LV applications shall be arc resistant.
IOGP Quality Requirements define CAS (Conformity Assessment System) levels, from A (the
maximum extent of verification) to D (the minimum extent of verification). Inspection and
testing activities, and COMPANY intervention, regardless from the entity that purchases the
equipment (e.g. COMPANY, CONTRACTOR or VENDOR), shall be minimum as follows.
• CAS “A” according to MOD.ELE.MVS.002 “Quality requirements for high voltage
switchgear and controlgear (IOGP S-620Q) (IDS)”
• CAS “C” according to MOD.ELE.RMA.023 “Quality requirements for low voltage three
phase cage induction motors (IOGP S-703Q) (IDS)”
If systems for safe shut down of turbines relying on electrical power are required, such as DC
UPS with battery back-up, these shall be with redundant battery back-up for the required
autonomy period and they shall be certified EPL “Gb”, even if located in safe area. Such system
shall not rely on equipment not certified EPL “Gb”. The gas group shall be determined at project
level, considering the potential emission sources present in the nearby hazardous areas.
Adjustable speed electrical power drive systems (including converters, transformers, filters if
any and motors) shall comply with IEC 61800 (all parts excluding IEC 61800-4).
With reference to IEC 61800-5-1:2016, subclause 4.3.3.3, protective measures against direct
contacts shall be provided even in case of installation in closed electrical operating areas.
Minimum protection degree of the drive enclosure shall be IP31. In case live parts need to remain
energized when the enclosure is open (e.g. during maintenance or installation), they shall be
protected to at least IPXXB.
With reference to IEC 61800-5-1:2016, subclause 4.3.5.1, protective class 0 is not allowed.
Adjustable speed electrical power drive systems shall include the protections against short
circuit, overload, ground fault for the motor and for the converter.
In case of outdoor installation, minimum protection degree of the drive enclosure shall be IP55.
BULK MATERIALS
LED lighting luminaires shall be selected within risk groups RG0 and RG1, according to IEC TR
62778:2014, Table 1.
Luminaires in external areas and in mechanically ventilated spaces drawing outside air shall be
constructed in AISI 316L stainless steel, GRP or aluminium alloy.
The lighting systems is divided and classified as follows:
Normal lighting is the lighting system designed to enable normal operating activities.
The normal lighting for outdoors areas, roads, yards and tanks shall be designed maximising the
use of floodlight towers.
Floodlight towers shall comply with 28917.ENG.ELE.STD.
The location of the floodlight towers, the types, number and orientation of floodlights shall be
chosen to guarantee proper lighting illumination level both for work and for people’s safety.
To reduce lighting pollution, floodlight towers shall be fitted with:
• narrow-beam floodlights
• screens to prevent the beam of the headlights to come out from the fence
Local lighting systems (i.e. lighting fixture poles) shall be used in addition to the floodlight towers
system, to illuminate dark areas, stairs, local controls and instrumentations apparatus.
The emergency lighting system shall consist of the same normal lighting system described in the
previous paragraph but powered by the emergency power system.
The lamps, belonging to the normal lighting system, which will be reenergized by the emergency
system, shall be defined in order to guarantee at least the 30% of the lighting level in normal
operating conditions.
The floodlight towers shall not concur to this minimum value of 30%, although it is permitted to
connect these to the emergency distribution.
The emergency escape lighting system shall be implemented through lighting fixture with
instantaneous insertion lamps. Indoor lamps shall always be on, with exception of sleeping
rooms (including sleeping rooms in infirmary area) and cinemas, in which the lamps shall be
normally off and shall be automatically turned on when power is not available on all the AC
incomers to the UPS feeding them.
Outdoor lamps shall be controlled in two modes, as shown in 28882.ENG.ELE.STD:
• In manual mode, always on
• In automatic mode, by means of crepuscular switch
The power supply for crepuscular switch shall be fed by UPS.
Control circuits for crepuscular switches shall be 'fail-safe', i.e., they shall switch the lights ON if
a fault occurs in the crepuscular switches and an alarm shall be raised to the EMS.
The lighting fixtures shall be positioned in the critical points of the plants and buildings, in order
to detect and allow the use of escape ways and the orientation of the personnel present.
Spot lightings shall be foreseen in proximity of communication points with control rooms and/or
rescue centres (i.e. phone and interphone locations).
Emergency escape lighting fixtures shall be placed all along transit ways with lightings that are
sufficient to allow personnel movement, along escape ways and where specifically required by
safety standards and regulations.
Floodlights shall not be used to concur to the lighting levels required for emergency escape
lighting.
The normal, emergency and safety lighting systems in buildings and cabins, such as electric
substations and control rooms, shall be managed by dedicated electrical switchboards installed
inside each building or cabin.
Each switchboard shall be provided with a normal lighting section, emergency lighting section
and Emergency escape lighting section, in exception to 2.9.1.2.1. Each section shall be provided
with general circuit breaker, MCB with RCD for every circuit and shall not be affected by
crepuscular switch state. Exception shall be made for IT system distributions, for which RCD is
not applicable.
For LV motors, motor control station shall be required in the project documents considering the
operability and maintenance requirements.
It shall comply with the classification of hazardous areas as per point 2.8.2 and shall be equipped
with the following lamps (led type):
• Green light – Motor Control Station enabled;
• White light – User ready to start;
and controls:
• Start-Stop control mode selector switch, with three positions: 0 = Central, position of
rest; Start: normally open contact, closes to left, with spring return to 0; Stop = normally
closed contact, opens to right, with latched position, padlockable. Starting shall be
operational only if enabled from the DCS or UCP, stopping shall always be available.
For MV motors, a local stop shall be foreseen. It shall always be operational, latched and
padlockable in the stop position. If the push button is in the stop position, the motor shall not
be seen as available for starting in the DCS or UCP.
Different arrangements (e.g. additional ammeter or emergency pushbutton) shall be provided if
required in the project documents.
For fire-fighting pumps, see specific requirements in relevant regulations.
Unless otherwise specified in the project documents, the power sockets shall be:
• 690V/400 V, 32 A, 3-Ph+N+E (or 3-Ph+E for IT systems);
• 230V, 16 A, 1-Ph+N+E (or 2-Ph+E for IT systems).
These shall be provided with interlock.
Convenience sockets shall comply with local rules of the Country where the equipment is
installed.
2.9.4 Conduits
The electrical cable trays shall be ladder type and these shall be provided with cover.
The materials indicated in TABLE 16 shall be used.
MATERIAL INSTALLATION
AISI 316L
Offshore and Onshore outdoors in an aggressive
Glass Reinforced Polyester (GRP) environment (e.g. marine environment)
GRP cable trays shall not be used for cables that are required to be fire resistant.
Cable trays (ladder type) shall be filled with one layer of cables only, with exception of lighting,
small power and control circuits, for which bunched installation is acceptable.
Cable trays shall have at least 30 cm between the bottom of a tray and the cover of the cable
tray below. In the space below the false floor of the electrical room, a minimum free space of 80
cm shall be kept between parallel cable tray routes, in order to allow the access of a person.
Cable routes shall be designed to keep at least 20% of spare space after project completion.
For characteristics of cable trays, refer to COMPANY Standard 28916.ENG.ELE.STD “Cable
ladders and cable trays”. The use of special parts built in during construction in yard (like curves,
T section, slopes etc.) shall be strictly forbidden. All parts shall be part of the VENDOR cable
trays part list. No other assemblies shall be permitted.
For surface treatments of cable trays, refer to COMPANY standard 29000.ENG.CPI.STD (offshore
and coastal areas) or 29001.ENG.CPI.STD (onshore). Requested durability, when mentioned in
29000.ENG.CPI.STD or 29001.ENG.CPI.STD, shall always be more than 15 years.
For routing installation criteria refer to COMPANY Standard 28045.ENG.STA.PRG. (paragraph of
instrumentation cable ladders/trays).
Electrical resistance trace heating shall comply with IEC/IEEE 60079-30-1 and IEC/IEEE 60079-
30-2.
If electrical resistance trace heating is entirely installed in non-hazardous areas, and if
compliance with IEC/IEEE 60079-30-1 and IEC/IEEE 60079-30-2 is not requested in 3.3, IEC
62395-1 and IEC 62395-2 may be used instead of IEC/IEEE 60079-30-1 and IEC/IEEE 60079-
30-2.
Switchgear, local panels, junction boxes and transformers part of electrical resistance trace
heating system shall comply in addition with relevant requirements indicated in the present
document, and referenced standards.
Power transformers dedicated to trace heating shall have a kVA rating at least equal to the 125%
of calculated maximum trace heating loads.
The choice of the protective devices shall consider the start-up currents and the time necessary
to reach the design operating conditions, starting from the minimum possible temperature. No
more than five heating devices or segments shall be connected to the same protective device.
Back-up trace heaters shall be provided to satisfy the following requirements:
• At least 20% of back-up trace heaters shall be provided.
• In case of interruption of a single circuit, for protection intervention or maintenance, it
shall be possible to switch on a back-up trace heater to keep the required performances
of the trace heating system.
• If the trace heating is classified as emergency service, in case of fault of a circuit, a back-
up trace heater shall be designed to switch on in automatic.
Alarms generated by the electrical resistance trace heating system shall be visible in a manned
location. As a minimum, alarms shall be raised in case of fault on a trace heating circuit and in
case of temperatures outside the required operating limits.
The distribution to trace heating loads shall be designed in such a way that:
• The fault or unavailability of a single transformer does not leave any trace heating service
as unavailable.
• The fault or unavailability of a single switchgear busbar, or of a single local panel, does
not leave any trace heating service classified as emergency, or necessary for power
generation start up, or necessary for production, as unavailable.
Additional requirements for electrical resistance trace heating systems, depending on the
standard followed as per above requirements, are described in 2.9.8.1 and 2.9.8.2.
The methods to guarantee that sheath temperatures do not exceed the limits required in
IEC/IEEE 60079-30-1 and IEC/IEEE 60079-30-2, with respect to temperature class or ignition
temperature, and the methods for temperature control, shall be proposed by VENDOR, including
the use of temperature controllers, temperature limiters and sensors, and subject to COMPANY
approval.
Routine tests shall be as per IEC/IEEE 60079-30-1. Test reports shall be provided.
Type test reports shall be provided as per IEC/IEEE 60079-30-1.
The data indicated in IEC/IEEE 60079-30-2, Annex A, shall be provided by CONTRACTOR in
project specification or data sheet.
For systems located in non-hazardous areas, but nonetheless required to follow the requirements
of IEC/IEEE 60079-30-1 and IEC/IEEE 60079-30-2, the requirements shall be those of EPL “Gc”
as a minimum.
Documentation requirements shall be as per IEC/IEEE 60079-30-1, clause 7 and subclauses,
and IEC 60079-30-2, 8.7.2.3.
In addition, electrical resistance trace heating shall comply with IEC 60079-14.
2.9.8.2 Electrical resistance trace heating following IEC 62395-1 and IEC 62395-2
The methods of temperature control, including the use of temperature controllers, temperature
limiters and sensors, shall be proposed by VENDOR and subject to COMPANY approval.
Routine tests shall be as per IEC 62395-1. Test reports shall be provided.
Refer to 28915.ENG.ELE.STD.
INSTALLATION REQUIREMENTS
Electrical rooms shall be located in a safe area. If not technically feasible, a positively pressurized
system shall be foreseen. A pressurization system shall also be considered in the case of heavy
pollution (sand, dust, etc.).
Electrical rooms shall be designed with modular bays guaranteeing their extension at least at
one end of the short side.
The following equipment shall not be installed in the same rooms as the electrical switchboards
and UPS:
• Generator;
• Resin (1) /Oil transformer;
• Batteries (2).
Note 1 The installation of dry type resin transformers in the switchroom is permitted if an additional
protective enclosure is foreseen. See 2.8.5.2 for details.
Note 2 See 2.10.1.3
Notes:
1. VENDOR installation instruction.
2. With rear access: 600mm.
3. Minimum distance from fence considering operation, maintenance and safety as per VENDOR
recommendation.
4. Valid for the other three sides.
5. In case rear accessibility is required for maintenance.
In case of equipment with doors, the minimum front side clearance shall be equal to the door’s
width plus 200mm.
The minimum vertical clearance from equipment to ceiling shall be 450 mm. In case of presence
of flaps for the evacuation of gases produced during internal arc, the distances recommended
by VENDOR shall be respected. In case such gases are evacuated by means of a conduit, the
space on top of the conduit may be reduced below 450 mm, according to VENDOR
recommendations.
At least one access door shall be sized to allow the passage of the single largest part of an
equipment (at least the complete largest and tallest switchgear column).
A free area under the floor shall be provided to allow the installation of cable trays and cables.
The minimum available space excluding the space taken by the structure, shall be:
• cable cellar: 1800 mm;
• floating floor: 800 mm.
Outdoors, power transformers shall be installed in a fenced area. As an alternative, these may
be installed in a room with one side open to the outside by means of grating or louvers.
A key interlock shall be implemented to guarantee that opening of the gates of the fence (or of
the door to the room) shall be possible only if the transformer is powered off, unless the
transformer is mechanically protected to avoid direct contacts, or if all potentially live parts are
located out of reach, at a minimum height as per indications of IEC 61936-1.
Unless the transformer is oil immersed type connected to overhead lines, outdoor transformer
bay shall be equipped with canopy. Canopy shall be sloped to avoid the stagnation of water.
Neutral earthing resistors shall be placed in proximity of transformers.
Oil immersed transformers shall be provided with:
• oil catchment pit below the power transformer;
• fire-walls between each transformer (1).
NOTE 1 the separation distance between transformers shall be in accordance with IEC 61936-1. If it is not
practical or economic to allow for adequate clearance, then a fire-resistant separating wall shall be installed,
in accordance with IEC 61936-1.
For oil immersed transformers, the direction of emission of liquid from the pressure relief device
shall be away from the position of possible approach of an operator to the bay in which the
transformer is installed.
The electrical equipment inside the battery room shall be certified EPL “Gb”, gas group IIC or
IIB+H2, temperature class T3. The battery room ventilation shall be as per 20453.ENG.MEC.PRG
(onshore) or 20452.ENG.MEC.PRG (offshore), and in compliance with IEC 62485-2. A minimum
of two extracting fans shall be provided. The floor shall be resistant to the electrolyte used for
the batteries.
If cables of different insulation voltage levels and different services (e.g. power and electrical
control cables) are installed in the same cable tray, a metal barrier shall be used to separate
them.
The cable routes of safety users shall be kept separate from those in normal and emergency
system. Cables used for safety users shall be “fire resistant” type.
Single core cables shall be laid in trefoil or in linear laying with transposition of each phase.
Moreover, all crossings, passages, penetration of single core cables shall be realized in non-
magnetic material.
Laying of cables on the floor, on the ground, or on the bottom of the area under false floor, is
not permitted.
The required minimum depth for underground cables shall be:
• 1 m for MV cables
• 0,8 m for LV cables
Underground duct banks shall be provided with suitable cable pulling pit at both ends of the duct
bank in order to ease the cable pulling.
Cables shall be identified by means of the application of appropriate labeling in AISI 316L with
letters engraved in compliance with the COMPANY standard 20198.VAR.LCI.STD.
The label shall be installed:
• At both cable ends
• Where the cable changes the direction
• Before and after cable penetration (MCT, wall, etc.)
For MCTs, see 2.9.7.
In addition, the following cable entry methods for wall crossing may be used:
• sleeves welded to the plate, to be sealed with a locking compound and plugging fibre
after the insertion of cables;
• sleeves welded to the plate, with cable glands screwed to the external side;
• sealed and threaded transits provided with a threaded locking rings for the closing plate.
Every floodlight tower shall be provided with local panel containing the protective device for all
floodlight and for other electrical accessories (e.g. electric motor for mobile crown). The
enclosure shall be in accordance with the hazardous area classification. For details, refer to
28917.ENG.ELE.STD.
The power on three-phase or three-phase with neutral circuits shall be uniformly distributed
among the three phases. Similarly, the power on the single-phase distribution to luminaires shall
be balanced on the upstream three phase supply system.
The power to adjacent lighting fixtures shall be supplied from different circuits (at least 2) so
that in case of fault or planned cut-off of a circuit, part of the lighting can still be kept in
operation.
With the aim to avoid stroboscopic effects, feeding of luminaires in the same areas shall be
provided from different phases.
Circuit breakers feeding lighting circuits shall be designed considering the inrush current of the
lighting fixtures.
Lighting distribution to luminaires shall be single phase except for:
• Floodlight tower;
• Street lights.
The cable sections shall be coordinated with the corresponding entrances on the lamp
enclosures; if this cannot be achieved, a local junction box (one for each lighting fixture) shall
be foreseen.
If MV or HV equipment are present, a global earthing system shall be adopted for the entire
facility, according to the definition of IEC 61936-1 and EN 50522.
2.10.4.1 HV substations
The grid mesh of grounding system shall be calculated in order to comply with the requirements
of IEC 61936-1, but in any case it shall not be larger than 5 m x 5 m.
Surge arresters shall be connected with the shortest routes and, in any case, with large elbow
bending, to the earth electrode.
Every equipment and every other metal structures shall be connected to the earth electrode by
means of two earth wires.
Air insulated high voltage substation shall be protected against lightning by means of overhead
earthing wires.
The frame structures supporting the overhead earthing wires may be used as natural down-
conductor, provided their metallic continuity is proved.
A buried bare-wire ring shall be provided around the electric substations; the ring shall be
connected to the general earth electrode of the plant in at least four points. A ring of bare
conductor along the internal perimeter of the switchboard room or of the relevant cables room
is required, and shall be connected at external ring in at least four points. Every switchboard
shall be connected at the internal bare-wire in at least two points.
The substation metal structures and/or concrete reinforcement bars shall be electrically bonded
and shall be connected to the earth electrode, according to reference rules.
In substations with concrete flooring, with a pre-welded metal grid, the grid shall be connected
to the earth electrode by means of earthing bars.
Any metal structures, equipment, columns, tanks, rails etc. which are inside the area relevant
to the earth electrode shall be connected to the earth electrode through earthing conductors or
through other metal structures.
Electrical continuity shall be guaranteed in the piping spools to avoid sparking due to static
electricity. The flanges shall guarantee electrical continuity. If this is not achieved through the
metal to metal contact on the flange and the flange serrating bolts (due to painting insulation
thickness or nonconductive gaskets), this shall be achieved through bonding jumpers directly
installed on the flanges bolts. If flange insulation gaskets are foreseen to avoid corrosion between
different piping materials, isolating sparking gap connectors shall be used.
Any metal structures, cable trays, rails, pipes etc. entering or leaving the plant earth electrode
area shall be interrupted by means of insulating joints.
The armour or braid of electrical cables shall be earthed at both ends. The armour or braid shall
be capable to sustain the earth fault current flowing through it for the time necessary for the
intervention of the protections. For single core cables, the sizing of the cable shall also consider
the flowing of current in the armour during normal operation.
Screen of electrical cables, if present, shall be earthed at one end only. If one end is on field or
in classified area, this shall be the one to be earthed, otherwise it shall be earthed on switchgear
side. A specific study shall be made to verify the voltages between the screen and earth on the
unearthed side, considering the worst case (in terms of cable current and cable length).
Unearthed screen extremities shall be covered and isolated against the possibility of accidental
contact during inspection or maintenance activities. The unearthed side shall be isolated at least
with the same insulation level of the cable nominal voltage.
Specific requirements for interconnecting cables inside packages (e.g. motor and adjustable
speed electrical power drive system), if different from those above indicated, shall be declared
by the VENDOR.
Onshore, if a cable is connecting equipment located in areas with separate earth electrodes, the
armour or braid shall be in one of the two following conditions:
• Earthed at one end only. This is not permitted in LV. If one end is in classified area, this
shall be the one to be earthed. A specific study shall be made to verify the voltages
between armour or braid and earth on the unearthed side, and unearthed armour
extremities shall be covered and isolated against the possibility of accidental contact
during inspection or maintenance activities. The unearthed side shall be isolated at least
with the same insulation level of the cable nominal voltage.
• Earthed at both ends. In this case, the earthing system of each of the two facilities shall
be verified also against an earth fault in the other facility.
In respect of electrostatic charges and lightning, all pipes penetrating a structure (e.g. plant unit
or building) shall be connected to the earth electrode at the point of penetration; furthermore,
their metallic continuity shall be verified and in case it is not guaranteed, equipotential
connections shall be installed. Earthing connections shall be designed considering cathodic
protection systems, if present.
2.10.4.5 Buildings
A bare-wire ring, horizontally buried at a minimum depth of 0,5 m and at a distance of 0,5 m up
to 1 m, shall be provided around buildings. The ring shall be connected to the general earth
electrode of the system in at least four points by means of an earthing terminal or earthing bar.
The main metallic structures of buildings shall be connected at regular intervals, not exceeding
20m, to the above mentioned ring, alongside the reinforcing bars of concrete. All external masses
shall be connected to the ring.
Metal fences which are inside the earth electrode area shall be connected to the latter at least
in two points and, in any case, every 20m.
Metal fences located outside the plant earth electrode area shall not be connected to the plant
earth electrode. If there are electrical equipment mounted on them (e.g. lighting fixtures, electric
gates) or nearby in such a way that they could be touched by a person at the same time as the
fence, a separated local earth electrode shall be provided buried under the fence itself. Such
equipment shall be fed through isolation transformer; for the cables supplying the transformer,
armour and screen shall not be earthed on transformer side and the PE conductor shall not be
provided. Users shall be protected with residual current protection.
If electric gates and/or lighting affect only a small part of the fence, the affected fence shall be
insulated from the other parts.
Tankers and other mobile containers of flammable materials shall be connected to the fixed
filling/discharging equipment and earthed by means of specific devices, before the flammable
materials are transferred.
The specific devices shall be in “Ex d” execution, suitable for operation in the hazardous area.
They shall be anti-tearing type which unlocks automatically in case it is forgotten, and they shall
be provided with interrupting facilities (e.g. auxiliary contacts) to allow the starting of the pump
or block it.
In pipeline valve control rooms which contain motor-driven valves, in metallic continuity with
the pipeline, the motor controlling the valve shall not be connected to the earth system of the
plant.
Protection against indirect contacts shall be guaranteed with isolation transformer. For the cables
supplying the transformer, armour and screen shall not be earthed on transformer side and the
PE conductor shall not be provided. Users shall be protected with residual current protection.
Aviation warning lights shall be installed in accordance with Volume 1 Chapter 6 of ICAO Annex
14. The luminaires shall consist of a double lamp unit with automatic changeover to the stand-
by lamp upon failure of the operating lamp.
Power sockets shall be provided for operative and maintenance purposes. Their position shall be
close to the point of possible use.
The sockets shall be located as indicated in the TABLE 18.
Process area excluding elevated platforms and 1 socket 690V/400V 32A every 30 m of range
passageways 1 socket 230V-16A every 15 m of range
The convenience socket (wall mounted) in the building or prefabricated cabins (package type)
shall be installed at an elevation not lower than 300 mm from the floor (measured from the
socket's centre line).
GENERAL
The design of the electrical system for offshore installation shall comply with chapter 2 of the
present document, with the exceptions and amendments indicated in this chapter 3.
The design of electrical systems for offshore installations shall be in accordance with IEC 61892.
In case IEC 61892 has different requirements than chapter 2 or chapter 3 of the present
document, the most stringent requirement shall be applied. Due to limited space and evacuation
time in case of danger, specific requirements regarding people safety shall be foreseen..
Materials and equipment with low risk of fire and smoke emission shall be used.
Cables with low smoke and zero halogen emission shall be used.
Outdoor equipment shall be rated IP 56 or IP 66 (IP 65 or IP 66 for lighting fixtures). For
transformers, refer to 2.8.5 and subparagraphs.
A floating floor shall be provided within switchroom (with minimum height of 800 mm) for cable
routing. Cable penetrations shall be by MCT.
In addition to TABLE 4, for emergency loads refer to IEC 61892-2, Annex B, considering that
some of the loads are however already classified as safety in the present document.
In some countries (e.g. Italy) the local regulation requires the segregation between emergency
switchroom and normal switchroom.
For FPSO and floaters, the main emergency switchgear shall be separate, and in a different
room, with respect to normal and essential switchgear.
For dry type transformers, AFWF cooling method is permitted, but only if the following two
conditions are verified:
• The transformer is not energized when the system is powered from emergency power
sources.
• The water system necessary for cooling is available and operational without prior
energization of the transformer.
If liquid immersed transformers are installed, the requirements of IEC 61936-1 shall be complied
with in this respect, in addition to the requirements of IEC 61892-6.
Liquid immersed transformers shall have internal cooling medium indicated with letter “K”
according to IEC 60076-2.
NEUTRAL EARTHING
The neutral configuration in offshore installation shall be in accordance with TABLE 19:
Neutral isolated or
impedance earthed
for power
distribution, process
users, vessel users,
essential generators,
emergency
generators (IT)
Notes:
(1) According to par. 2.7.5.1
Regarding the UPS, see par. 2.7.5.3. Regarding other low voltage switchgear with IT system,
insulation control devices shall be provided. In case of earth fault, an alarm shall be raised to
the EMS, with indication of the faulty busbar. The faulty feeder shall be identified by means of
visual indication on the front of the switchgear.
28880.ENG.ELE.STD has been designed for TN systems. If IT system is used,
28880.ENG.ELE.STD shall be updated by CONTRACTOR on project basis and submitted for
COMPANY approval.
In IT systems, the neutral conductor shall not be distributed.
In addition to par. 2.8.2, the requirements of ignition source control indicated in IEC 61892-1
shall be followed.
Moreover, considering a future reclassification of area, or to standardize and to reduce the spare
parts, electrical bulk materials shall be certified EPL “Gc” also if installed in outdoor non-
hazardous areas.
Electrical resistance heat tracing systems located outdoors, or required to fulfil the requirements
for installation in hazardous area due to ignition source control principles indicated in IEC 61892-
1, shall comply with IEC/IEEE 60079-30-1 and IEC/IEEE 60079-30-2.
PROTECTIVE DEVICE
Contrary to what is indicated in IEC 61892-2, subclause 11.2.3, the backup protection device is
not permitted; all devices shall have a breaking or making short-circuit capacity higher than the
prospective short-circuit current at the point where these are installed.
In addition to 2.7.7.1, in offshore it is permitted to use a FCL (fault current limiter) also for new
facilities, subject to COMPANY approval.
The use of FCL for new facilities shall also be subject to both the following conditions:
• The FCL is installed in, or connected to the switchgear to which main power generation
is connected.
• The nominal system voltage utilized for the switchgear where the main power generation
is connected is 11 kV for 50 Hz systems or 13,8 kV for 60 Hz systems, and the switchgear
has a rated short time withstand current equal to the maximum permitted in TABLE 7.
In addition to main and emergency power generators, essential power generators shall be
installed for FPSO-FLNG and may be required for offshore platforms.
Essential power generators shall guarantee the supply of all preferential users necessary to
maintain the unit in habitable condition, naval loads, offloading loads and all the process and
utilities to assure proper subsea field preservation. For additional details, see IEC 61892-2,
Annex A.
The typical configuration is 1+1, i.e. 2 generators each sized for 100% of load (1 running + 1 in
stand-by).
It shall be possible to feed the whole emergency distribution network from essential power
generation, and the whole plant under main power source.
In case of loss of main power sources, essential generators shall be capable to start and to
connect to the loads even if the emergency power generation is not operational.
Contrary to what is indicated in IEC 61892-2, subclause 4.2.1, essential power generators shall
not be used as spares of main power generators to fulfill the N+1 sparing philosophy requested
in 2.8.3.2, unless specifically authorized by COMPANY.
In case essential power generation is necessary for the black start of the facility, or to restore
the main power sources following a shut-down, essential generators shall be in N+1 sparing
philosophy.
TABLE 20 describes the operating mode for FPSO and floaters.
Notes:
(1) When the required total power exceeds the power rating of N generators, all generators may work
(including the stand by generator), subject to specific COMPANY authorization.
(2) When one main generator is out of service, a configuration with essential generators running may
be foreseen, subject to specific COMPANY authorization.
(3) Production and offloading mode may be supplied by Main and essential generator together, subject
to specific COMPANY authorization.
CABLES
All electrical power and control cables (included internal wiring of switchgear and other enclosure
for electrical equipment) shall be in accordance with IEC 61892 with the following amendment:
• § 9.1 Cables
In addition to what is indicated in the reference paragraph, the following circuits shall be
realized with cables low smoke, halogen free and fire resistant, according to IEC 61034-
2, IEC 60754-1, IEC 60754-2 and IEC 60331 series:
- Power and control of firefighting system;
- Fire and gas detection system (1)
- Emergency escape lighting;
- Interconnecting cables from battery to UPS;
- Navigation Aids, Aeronautical obstruction lights, helideck lights, helideck and boat
landing status lights.
- Radio communication (1)
- Other emergency and critical loads defined in the project specification.
Note (1): See also COMPANY Standard 28045.ENG.STA.PRG.
The outer sheath compounds of cables shall be SHF 1 or SHF 2 according to IEC 60092-360.
Even if indicated in IEC 60228, Aluminum conductor for electrical cables is not permitted.
Routine tests, sample tests, type tests shall be performed as per indications of reference
standards IEC 60092-353 (Tables 4, 5, 6), IEC 60092-354 (Tables 3, 4, 5).
Test after installation shall be performed as per Annex A of IEC 60092-354.
When fire resistance is required, type tests shall be as per IEC 60092-353 Table 7 and as per
Annex A of IEC 61892-4:2019.
Reports of the tests shall be provided. Type tests already performed do not need to be repeated,
if so permitted in reference standards.
DC voltage test of the insulation shall be avoided.
For projects for facilities in the European Union, see the requirements of 2.8.11.10.
If a cable is connecting two different plants of which at least one is offshore, the armour shall
be earthed at both ends. The earthing system of each of the two facilities shall also be verified
against the possibility of earth fault in the other facility.
The requirements and recommendations of IEC 61892-2, IEC 61892-3 and IEC 61892-6 shall be
complied with, in addition to specific regulations of the classification society. The protection of
exposed vents against the possibility of lightning strike shall be verified.
LIGHTING
Navigation and aeronautical aids system shall comply with COMPANY Standard
20174.ENG.ELE.STD.
Concerning the electrical parts of the swivel and turret, IEC 61892-2 shall be complied with,
including the recommendations included in Annex D.
Electrical distribution through the swivel shall be designed in such a way that a failure of any
feeder passing through slip rings does not render any essential, emergency or safety service
unavailable.
A minimum of 20% spare slip rings shall be provided on medium and low voltage swivel, if
present. As a minimum, swivel paths sufficient for two spare feeders for medium voltage and
two spare feeders for low voltage shall be provided. Rating of the spares shall be selected based
on the maximum rating of the slip rings foreseen, unless specifically otherwise approved by
COMPANY.
SUBMARINE CABLES
This paragraph is applicable to submarine cables connecting two surface facilities, and does not
cover umbilicals or feeding of subsea facilities.
Submarine cables and related accessories shall comply with IEC 63026, for the voltage ranges
and water depths therein indicated. For the purpose to choose submarine cable rated voltages,
the system shall be considered to be of Category C as per IEC 63026.
Submarine cables and related accessories shall be sized considering a margin of 20% on the
calculated current requirements.
Where a greater protection of the cable is required (e.g. in sea beds in presence of rocks or
reefs) an additional layer shall be applied to the armour, as explained in subclause 5.8 of IEC
63026.
As a minimum, the characteristics of the cable listed in clause 6 of IEC 63026 shall be provided
by VENDOR.
Routine tests, sample tests, type tests and tests after installation shall be performed as per IEC
63026. The possibility to keep the validity of type tests performed on similar cables shall be as
described in clause 12 of IEC 63026. In any case, COMPANY shall be entitled to witness all the
tests. Reports of all tests, including type tests on similar cables, shall be provided.
DC voltage tests of the insulation shall be avoided.
The cable shall include the minimum possible number of joints.
Progressive numbering for the determination of the length, repeated at constant 1 m intervals
on the external sheath of the cable, shall be provided.
If delivery in drums is applied, the extremities of each cable delivery length shall be sealed and
fixed to the drum. The extremities of each cable delivery length shall be accessible for checks
and tests without need of unwinding the cable. The internal and external flanges of the drums
shall be provided with metallic label indicating at least the following:
• Data at points a) and b) of clause 6 of IEC 63026
• Number of cores and conductor cross section
• Cable identification code number
• Drum identification number
• Length of cable on the drum
• Total weight of drum and cable
As a minimum, optical fibre shall be provided in order to realize intertripping and interlocking
functions between switchgear feeder and switchgear incomer located upstream and downstream
of the cable, as indicated in 2.7.8 and 28881.ENG.ELE.STD. Optical fibre inside the cable shall
comply with IEC standards developed by technical committee 86 and subcommittees.
Submarine cables and their accessories, if used for dynamic applications such as connection to
floating installations, or if used beyond the water depth limits indicated in IEC 63026, shall have
been subject to a qualification process. The procedure for such qualification process, that shall
consider the effects of extreme loads and a fatigue analysis related to conditions of installation
and during operational life, shall be proposed by VENDOR and subject to COMPANY approval.
The qualification process shall include fatigue testing and shall be based on sound technical and
scientific publications, such as:
• Cigré TB623 “Recommendations for Mechanical Testing of Submarine Cables”
• DNVGL-RP-F401 “Electrical power cables in subsea applications”