General Rules of Electrical Installation Design: Chapter A
General Rules of Electrical Installation Design: Chapter A
General Rules of Electrical Installation Design: Chapter A
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Contents
Methodology Rules and statutory regulations
2.1 Definition of voltage ranges 2.2 Regulations 2.3 Standards 2.4 Quality and safety of an electrical installation 2.5 Initial testing of an installation 2.6 Periodic check-testing of an installation 2.7 Conformity (with standards and specifications) of equipment used in the installation 2.8 Environment
A2 A4
A4 A5 A5 A6 A6 A7 A7 A8
3 4
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A10 A12
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A15 A15 A16 A17 A18 A19 A20
Methodology
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For the best results in electrical installation design it is recommended to read all the chapters of this guide in the order in which they are presented.
Service connection
B Connection to the MV utility distribution network
This connection can be made at: b Medium Voltage level A consumer-type substation will then have to be studied, built and equipped. This substation may be an outdoor or indoor installation conforming to relevant standards and regulations (the low-voltage section may be studied separately if necessary). Metering at medium-voltage or low-voltage is possible in this case. b Low Voltage level The installation will be connected to the local power network and will (necessarily) be metered according to LV tariffs.
E - LV Distribution
Methodology
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Reactive energy
The power factor correction within electrical installations is carried out locally, globally or as a combination of both methods.
M - Harmonic management
Harmonics
Harmonics in the network affect the quality of energy and are at the origin of many disturbances as overloads, vibrations, ageing of equipment, trouble of sensitive equipment, of local area networks, telephone networks. This chapter deals with the origins and the effects of harmonics and explain how to measure them and present the solutions.
Generic applications
Certain premises and locations are subject to particularly strict regulations: the most common example being residential dwellings.
Q - EMC guideline
EMC Guidelines
Some basic rules must be followed in order to ensure Electromagnetic Compatibility. Non observance of these rules may have serious consequences in the operation of the electrical installation: disturbance of communication systems, nuisance tripping of protection devices, and even destruction of sensitive devices.
Ecodial software
Ecodial software(1) provides a complete design package for LV installations, in accordance with IEC standards and recommendations. The following features are included: b Construction of one-line diagrams b Calculation of short-circuit currents b Calculation of voltage drops b Optimization of cable sizes b Required ratings of switchgear and fusegear b Discrimination of protective devices b Recommendations for cascading schemes b Verification of the protection of people b Comprehensive print-out of the foregoing calculated design data
(1) Ecodial is a Merlin Gerin product and is available in French and English versions.
Schneider Electric - Electrical installation guide 2009
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Low-voltage installations are governed by a number of regulatory and advisory texts, which may be classified as follows: b Statutory regulations (decrees, factory acts,etc.) b Codes of practice, regulations issued by professional institutions, job specifications b National and international standards for installations b National and international standards for products
Three-phase four-wire or three-wire systems Nominal voltage (V) 50 Hz 60 Hz 120/208 240 230/400(1) 277/480 400/690(1) 480 347/600 1000 600
(1) The nominal voltage of existing 220/380 V and 240/415 V systems shall evolve toward the recommended value of 230/400 V. The transition period should be as short as possible and should not exceed the year 2003. During this period, as a first step, the electricity supply authorities of countries having 220/380 V systems should bring the voltage within the range 230/400 V +6 %, -10 % and those of countries having 240/415 V systems should bring the voltage within the range 230/400 V +10 %, -6 %. At the end of this transition period, the tolerance of 230/400 V 10 % should have been achieved; after this the reduction of this range will be considered. All the above considerations apply also to the present 380/660 V value with respect to the recommended value 400/690 V. Fig. A1 : Standard voltages between 100 V and 1000 V (IEC 60038 Edition 6.2 2002-07)
Series I Highest voltage for equipment (kV) 3.6(1) 7.2(1) 12 (17.5) 24 36(3) 40.5(3)
Nominal system voltage (kV) 3.3(1) 3(1) 6.6(1) 6(1) 11 10 (15) 22 20 33(3) 35(3)
Series II Highest voltage for equipment (kV) 4.40(1) 13.2(2) 13.97(2) 14.52(1) 26.4(2) 36.5
Nominal system voltage (kV) 4.16(1) 12.47(2) 13.2(2) 13.8(1) 24.94(2) 34.5
These systems are generally three-wire systems unless otherwise indicated. The values indicated are voltages between phases. The values indicated in parentheses should be considered as non-preferred values. It is recommended that these values should not be used for new systems to be constructed in future. Note : It is recommended that in any one country the ratio between two adjacent nominal voltages should be not less than two. Note 2: In a normal system of Series I, the highest voltage and the lowest voltage do not differ by more than approximately 10 % from the nominal voltage of the system. In a normal system of Series II, the highest voltage does not differ by more then +5 % and the lowest voltage by more than -10 % from the nominal voltage of the system. (1) These values should not be used for public distribution systems. (2) These systems are generally four-wire systems. (3) The unification of these values is under consideration. Fig. A2 : Standard voltages above 1 kV and not exceeding 35 kV (IEC 60038 Edition 6.2 2002-07)
2.2 Regulations
In most countries, electrical installations shall comply with more than one set of regulations, issued by National Authorities or by recognized private bodies. It is essential to take into account these local constraints before starting the design.
2.3 Standards
This Guide is based on relevant IEC standards, in particular IEC 60364. IEC 60364 has been established by medical and engineering experts of all countries in the world comparing their experience at an international level. Currently, the safety principles of IEC 60364 and 60479-1 are the fundamentals of most electrical standards in the world (see table below and next page).
IEC 60038 IEC 60076-2 IEC 60076-3 IEC 60076-5 IEC 60076-0 IEC 6046 IEC 60255 IEC 60265- IEC 60269- IEC 60269-2 IEC 60282- IEC 60287-- IEC 60364 IEC 60364- IEC 60364-4-4 IEC 60364-4-42 IEC 60364-4-43 IEC 60364-4-44 IEC 60364-5-5 IEC 60364-5-52 IEC 60364-5-53 IEC 60364-5-54 IEC 60364-5-55 IEC 60364-6-6 IEC 60364-7-70 IEC 60364-7-702 IEC 60364-7-703 IEC 60364-7-704 IEC 60364-7-705 IEC 60364-7-706 IEC 60364-7-707 IEC 60364-7-708 IEC 60364-7-709 IEC 60364-7-70 IEC 60364-7-7 IEC 60364-7-72 IEC 60364-7-73 IEC 60364-7-74 IEC 60364-7-75 IEC 60364-7-77 IEC 60364-7-740 IEC 60427 IEC 60439- IEC 60439-2 IEC 60439-3 IEC 60439-4 IEC 60446 IEC 60439-5 IEC 60479- IEC 60479-2 IEC 60479-3
Standard voltages Power transformers - Temperature rise Power transformers - Insulation levels, dielectric tests and external clearances in air Power transformers - Ability to withstand short-circuit Power transformers - Determination of sound levels Semiconductor convertors - General requirements and line commutated convertors Electrical relays High-voltage switches - High-voltage switches for rated voltages above 1 kV and less than 52 kV Low-voltage fuses - General requirements Low-voltage fuses - Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications) High-voltage fuses - Current-limiting fuses Electric cables - Calculation of the current rating - Current rating equations (100% load factor) and calculation of losses - General Electrical installations of buildings Electrical installations of buildings - Fundamental principles Electrical installations of buildings - Protection for safety - Protection against electric shock Electrical installations of buildings - Protection for safety - Protection against thermal effects Electrical installations of buildings - Protection for safety - Protection against overcurrent Electrical installations of buildings - Protection for safety - Protection against electromagnetic and voltage disrurbance Electrical installations of buildings - Selection and erection of electrical equipment - Common rules Electrical installations of buildings - Selection and erection of electrical equipment - Wiring systems Electrical installations of buildings - Selection and erection of electrical equipment - Isolation, switching and control Electrical installations of buildings - Selection and erection of electrical equipment - Earthing arrangements Electrical installations of buildings - Selection and erection of electrical equipment - Other equipments Electrical installations of buildings - Verification and testing - Initial verification Electrical installations of buildings - Requirements for special installations or locations - Locations containing a bath tub or shower basin Electrical installations of buildings - Requirements for special installations or locations - Swimming pools and other basins Electrical installations of buildings - Requirements for special installations or locations - Locations containing sauna heaters Electrical installations of buildings - Requirements for special installations or locations - Construction and demolition site installations Electrical installations of buildings - Requirements for special installations or locations - Electrical installations of agricultural and horticultural premises Electrical installations of buildings - Requirements for special installations or locations - Restrictive conducting locations Electrical installations of buildings - Requirements for special installations or locations - Earthing requirements for the installation of data processing equipment Electrical installations of buildings - Requirements for special installations or locations - Electrical installations in caravan parks and caravans Electrical installations of buildings - Requirements for special installations or locations - Marinas and pleasure craft Electrical installations of buildings - Requirements for special installations or locations - Medical locations Electrical installations of buildings - Requirements for special installations or locations - Exhibitions, shows and stands Electrical installations of buildings - Requirements for special installations or locations - Solar photovoltaic (PV) power supply systems Electrical installations of buildings - Requirements for special installations or locations - Furniture Electrical installations of buildings - Requirements for special installations or locations - External lighting installations Electrical installations of buildings - Requirements for special installations or locations - Extra-low-voltage lighting installations Electrical installations of buildings - Requirements for special installations or locations - Mobile or transportable units Electrical installations of buildings - Requirements for special installations or locations - Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses High-voltage alternating current circuit-breakers Low-voltage switchgear and controlgear assemblies - Type-tested and partially type-tested assemblies Low-voltage switchgear and controlgear assemblies - Particular requirements for busbar trunking systems (busways) Low-voltage switchgear and controlgear assemblies - Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access for their use - Distribution boards Low-voltage switchgear and controlgear assemblies - Particular requirements for assemblies for construction sites (ACS) Basic and safety principles for man-machine interface, marking and identification - Identification of conductors by colours or numerals Low-voltage switchgear and controlgear assemblies - Particular requirements for assemblies intended to be installed outdoors in public places - Cable distribution cabinets (CDCs) Effects of current on human beings and livestock - General aspects Effects of current on human beings and livestock - Special aspects Effects of current on human beings and livestock - Effects of currents passing through the body of livestock
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IEC 60529 IEC 60644 IEC 60664 IEC 6075 IEC 60724 IEC 60755 IEC 60787 IEC 6083 IEC 60947- IEC 60947-2 IEC 60947-3 IEC 60947-4- IEC 60947-6- IEC 6000 IEC 640 IEC 6557- IEC 6557-8 IEC 6557-9 IEC 6557-2 IEC 6558-2-6 IEC 6227- IEC 6227-00 IEC 6227-02 IEC 6227-05 IEC 6227-200 IEC 6227-202
Degrees of protection provided by enclosures (IP code) Spcification for high-voltage fuse-links for motor circuit applications Insulation coordination for equipment within low-voltage systems Dimensions of low-voltage switchgear and controlgear. Standardized mounting on rails for mechanical support of electrical devices in switchgear and controlgear installations. Short-circuit temperature limits of electric cables with rated voltages of 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV) General requirements for residual current operated protective devices Application guide for the selection of fuse-links of high-voltage fuses for transformer circuit application Shunt power capacitors of the self-healing type for AC systems having a rated voltage up to and including 1000 V - General - Performance, testing and rating - Safety requirements - Guide for installation and operation Low-voltage switchgear and controlgear - General rules Low-voltage switchgear and controlgear - Circuit-breakers Low-voltage switchgear and controlgear - Switches, disconnectors, switch-disconnectors and fuse-combination units Low-voltage switchgear and controlgear - Contactors and motor-starters - Electromechanical contactors and motor-starters Low-voltage switchgear and controlgear - Multiple function equipment - Automatic transfer switching equipment Electromagnetic compatibility (EMC) Protection against electric shocks - common aspects for installation and equipment Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for testing, measuring or monitoring of protective measures - General requirements Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for testing, measuring or monitoring of protective measures Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for insulation fault location in IT systems Electrical safety in low-voltage distribution systems up to 1000 V AC and 1500 V DC - Equipment for testing, measuring or monitoring of protective measures. Performance measuring and monitoring devices (PMD) Safety of power transformers, power supply units and similar - Particular requirements for safety isolating transformers for general use Common specifications for high-voltage switchgear and controlgear standards High-voltage switchgear and controlgear - High-voltage alternating-current circuit-breakers High-voltage switchgear and controlgear - Alternating current disconnectors and earthing switches High-voltage switchgear and controlgear - Alternating current switch-fuse combinations High-voltage switchgear and controlgear - Alternating current metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV High-voltage/low voltage prefabricated substations (Concluded)
The pre-commissioning electrical tests and visual-inspection checks for installations in buildings include, typically, all of the following: b Insulation tests of all cable and wiring conductors of the fixed installation, between phases and between phases and earth b Continuity and conductivity tests of protective, equipotential and earth-bonding conductors b Resistance tests of earthing electrodes with respect to remote earth b Verification of the proper operation of the interlocks, if any b Check of allowable number of socket-outlets per circuit
b Cross-sectional-area check of all conductors for adequacy at the short-circuit levels prevailing, taking account of the associated protective devices, materials and installation conditions (in air, conduit, etc.) b Verification that all exposed- and extraneous metallic parts are properly earthed (where appropriate) b Check of clearance distances in bathrooms, etc. These tests and checks are basic (but not exhaustive) to the majority of installations, while numerous other tests and rules are included in the regulations to cover particular cases, for example: TN-, TT- or IT-earthed installations, installations based on class 2 insulation, SELV circuits, and special locations, etc. The aim of this guide is to draw attention to the particular features of different types of installation, and to indicate the essential rules to be observed in order to achieve a satisfactory level of quality, which will ensure safe and trouble-free performance. The methods recommended in this guide, modified if necessary to comply with any possible variation imposed by a utility, are intended to satisfy all precommissioning test and inspection requirements.
Type of installation Installations which require the protection of employees b Locations at which a risk of degradation, fire or explosion exists b Temporary installations at worksites b Locations at which MV installations exist b Restrictive conducting locations where mobile equipment is used Other cases According to the type of establishment and its capacity for receiving the public
Installations in buildings used for public gatherings, where protection against the risks of fire and panic are required Residential
Conformity of equipment with the relevant standards can be attested in several ways
2.7 Conformity (with standards and specifications) of equipment used in the installation
Attestation of conformity
The conformity of equipment with the relevant standards can be attested: b By an official mark of conformity granted by the certification body concerned, or b By a certificate of conformity issued by a certification body, or b By a declaration of conformity from the manufacturer The first two solutions are generally not available for high voltage equipment.
Declaration of conformity
Where the equipment is to be used by skilled or instructed persons, the manufacturers declaration of conformity (included in the technical documentation), is generally recognized as a valid attestation. Where the competence of the manufacturer is in doubt, a certificate of conformity can reinforce the manufacturers declaration.
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Note: CE marking In Europe, the European directives require the manufacturer or his authorized representative to affix the CE marking on his own responsibility. It means that: b The product meets the legal requirements b It is presumed to be marketable in Europe The CE marking is neither a mark of origin nor a mark of conformity.
Mark of conformity
Marks of conformity are affixed on appliances and equipment generally used by ordinary non instructed people (e.g in the field of domestic appliances). A mark of conformity is delivered by certification body if the equipment meet the requirements from an applicable standard and after verification of the manufacturers quality management system.
Certification of Quality
The standards define several methods of quality assurance which correspond to different situations rather than to different levels of quality.
Assurance
A laboratory for testing samples cannot certify the conformity of an entire production run: these tests are called type tests. In some tests for conformity to standards, the samples are destroyed (tests on fuses, for example). Only the manufacturer can certify that the fabricated products have, in fact, the characteristics stated. Quality assurance certification is intended to complete the initial declaration or certification of conformity. As proof that all the necessary measures have been taken for assuring the quality of production, the manufacturer obtains certification of the quality control system which monitors the fabrication of the product concerned. These certificates are issued by organizations specializing in quality control, and are based on the international standard ISO 9001: 2000. These standards define three model systems of quality assurance control corresponding to different situations rather than to different levels of quality: b Model 3 defines assurance of quality by inspection and checking of final products. b Model 2 includes, in addition to checking of the final product, verification of the manufacturing process. For example, this method is applied, to the manufacturer of fuses where performance characteristics cannot be checked without destroying the fuse. b Model 1 corresponds to model 2, but with the additional requirement that the quality of the design process must be rigorously scrutinized; for example, where it is not intended to fabricate and test a prototype (case of a custom-built product made to specification).
2.8 Environment
Environmental management systems can be certified by an independent body if they meet requirements given in ISO 14001. This type of certification mainly concerns industrial settings but can also be granted to places where products are designed. A product environmental design sometimes called eco-design is an approach of sustainable development with the objective of designing products/services best meeting the customers requirements while reducing their environmental impact over their whole life cycle. The methodologies used for this purpose lead to choose equipments architecture together with components and materials taking into account the influence of a product on the environment along its life cycle (from extraction of raw materials to scrap) i.e. production, transport, distribution, end of life etc.
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In Europe two Directives have been published, they are called: b RoHS Directive (Restriction of Hazardous Substances) coming into force on July 2006 (the coming into force was on February 13th, 2003, and the application date is July 1st, 2006) aims to eliminate from products six hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) or polybrominated diphenyl ethers (PBDE).
b WEEE Directive (Waste of Electrical and Electronic Equipment) coming into force in August 2005 (the coming into force was on February 13th, 2003, and the application date is August 13th, 2005) in order to master the end of life and treatments for household and non household equipment. In other parts of the world some new legislation will follow the same objectives. In addition to manufacturers action in favour of products eco-design, the contribution of the whole electrical installation to sustainable development can be significantly improved through the design of the installation. Actually, it has been shown that an optimised design of the installation, taking into account operation conditions, MV/LV substations location and distribution structure (switchboards, busways, cables), can reduce substantially environmental impacts (raw material depletion, energy depletion, end of life) See chapter D about location of the substation and the main LV switchboard.
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An examination of the actual apparentpower demands of different loads: a necessary preliminary step in the design of a LV installation
The examination of actual values of apparent-power required by each load enables the establishment of: b A declared power demand which determines the contract for the supply of energy b The rating of the MV/LV transformer, where applicable (allowing for expected increased load) b Levels of load current at each distribution board
The nominal power in kW (Pn) of a motor indicates its rated equivalent mechanical power output. The apparent power in kVA (Pa) supplied to the motor is a function of the output, the motor efficiency and the power factor. Pn Pa = cos
kW input so that a kVA input reduction in kVA input will so that a kVA input reduction will increase kVA input (i.e. improve) improve) thecos . of cos the value of value increase (i.e.
As noted above cos
The current supplied to the motor, after power-factor correction, is given by: cos I=Ia cos ' where cos is the power factor before compensation and cos is the power factor after compensation, Ia being the original current. Figure A4 below shows, in function of motor rated power, standard motor current values for several voltage supplies.
kW
hp
230 V A 1.0 1.5 1.9 2.6 3.3 4.7 6.3 8.5 11.3 15 20 27 38.0 51 61 72 96 115 140 169 230 278 340 400 487 609 748 -
0.18 0.25 0.37 0.55 0.75 1.1 1.5 2.2 3.0 3.7 4 5.5 7.5 11 15 18.5 22 30 37 45 55 75 90 110 132 150 160 185 200 220 250 280 300
1/2 3/4 1 1-1/2 2 3 7-1/2 10 15 20 25 30 40 50 60 75 100 125 150 200 250 300 350 400 -
380 45 V A 1.3 1.8 2.3 3.3 4.3 6.1 9.7 14.0 18.0 27.0 34.0 44 51 66 83 103 128 165 208 240 320 403 482 560 636 -
400 V A 0.6 0.85 1.1 1.5 1.9 2.7 3.6 4.9 6.5 8.5 11.5 15.5 22.0 29 35 41 55 66 80 97 132 160 195 230 280 350 430 -
440 480 V A 1.1 1.6 2.1 3.0 3.4 4.8 7.6 11.0 14.0 21.0 27.0 34 40 52 65 77 96 124 156 180 240 302 361 414 474 -
500 V A 0.48 0.68 0.88 1.2 1.5 2.2 2.9 3.9 5.2 6.8 9.2 12.4 17.6 23 28 33 44 53 64 78 106 128 156 184 224 280 344 -
690 V A 0.35 0.49 0.64 0.87 1.1 1.6 2.1 2.8 3.8 4.9 6.7 8.9 12.8 17 21 24 32 39 47 57 77 93 113 134 162 203 250 -
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kW
hp
230 V A 940 1061 1200 1478 1652 1844 2070 2340 2640 2910
315 335 355 375 400 425 450 475 500 530 560 600 630 670 710 750 800 850 900 950 1000
540 500 -
400 V A 540 610 690 850 950 1060 1190 1346 1518 1673
500 V A 432 488 552 680 760 848 952 1076 1214 1339
690 V A 313 354 400 493 551 615 690 780 880 970
Nominal power (kW) 0.1 0.2 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 6 7 8 9 10
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Current demand (A) -phase -phase 27 V 230 V 0.79 0.43 1.58 0.87 3.94 2.17 7.9 4.35 11.8 6.52 15.8 8.70 19.7 10.9 23.6 13 27.6 15.2 31.5 17.4 35.4 19.6 39.4 21.7 47.2 26.1 55.1 30.4 63 34.8 71 39.1 79 43.5
3-phase 230 V 0.25 0.50 1.26 2.51 3.77 5.02 6.28 7.53 8.72 10 11.3 12.6 15.1 17.6 20.1 22.6 25.1
3-phase 400 V 0.14 0.29 0.72 1.44 2.17 2.89 3.61 4.33 5.05 5.77 6.5 7.22 8.66 10.1 11.5 13 14.4
Fig. A5 : Current demands of resistive heating and incandescent lighting (conventional or halogen) appliances
where U is the voltage between the terminals of the equipment. For an incandescent lamp, the use of halogen gas allows a more concentrated light source. The light output is increased and the lifetime of the lamp is doubled. Note: At the instant of switching on, the cold filament gives rise to a very brief but intense peak of current.
Ia =
Pballast + Pn U cos
If no power-loss value is Where U = the voltage indicated to the lamp, complete with its related equipment. applied for the ballast, a figure of 25% of Pn may be used. If no power-loss value is indicated for the ballast, a figure of 25% of Pn may be used.
Current (A) at 230 V Magnetic ballast Without PF correction capacitor 0.20 0.33 0.50 With PF correction capacitor 0.14 0.23 0.36 0.28 0.46 0.72
Electronic ballast
Single tube
Fig. A6 : Current demands and power consumption of commonly-dimensioned fluorescent lighting tubes (at 230 V-50 Hz)
(1) Ia in amps; U in volts. Pn is in watts. If Pn is in kW, then multiply the equation by 1,000 (2) Power-factor correction is often referred to as compensation in discharge-lighting-tube terminology. Cos is approximately 0.95 (the zero values of V and I are almost in phase) but the power factor is 0.5 due to the impulsive form of the current, the peak of which occurs late in each half cycle
Schneider Electric - Electrical installation guide 2009
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Current at 230 V (A) 0.080 0.110 0.150 0.075 0.095 0.125 0.170
Fig. A7 : Current demands and power consumption of compact fluorescent lamps (at 230 V - 50 Hz)
The power in watts indicated on the tube of a discharge lamp does not include the power dissipated in the ballast.
Discharge lamps
Figure A8 gives the current taken by a complete unit, including all associated ancillary equipment. These lamps depend on the luminous electrical discharge through a gas or vapour of a metallic compound, which is contained in a hermetically-sealed transparent envelope at a pre-determined pressure. These lamps have a long start-up time, during which the current Ia is greater than the nominal current In. Power and current demands are given for different types of lamp (typical average values which may differ slightly from one manufacturer to another).
Current In(A) Starting PF not PF Ia/In corrected corrected 230 V 400 V 230 V 400 V 0.3 0.45 0.65 0.85 1.4 2.2 4.9 0.17 0.22 0.39 0.49 0.69
Period (mins)
Utilization
High-pressure sodium vapour lamps 50 60 0.76 70 80 1 100 115 1.2 150 168 1.8 250 274 3 400 431 4.4 1000 1055 10.45 Low-pressure sodium vapour lamps 26 34.5 0.45 36 46.5 66 80.5 91 105.5 131 154
1.4 to 1.6 4 to 6
9000
1.1 to 1.3 7 to 15
100 to 200
8000 to 12000
Mercury vapour + metal halide (also called metal-iodide) 70 80.5 1 0.40 1.7 3 to 5 70 to 90 6000 b Lighting of very 150 172 1.80 0.88 6000 large areas by 250 276 2.10 1.35 6000 projectors (for 400 425 3.40 2.15 6000 example: sports 1000 1046 8.25 5.30 6000 stadiums, etc.) 2000 2092 2052 16.50 8.60 10.50 6 2000 Mercury vapour + fluorescent substance (fluorescent bulb) 50 57 0.6 0.30 1.7 to 2 3 to 6 40 to 60 8000 b Workshops 80 90 0.8 0.45 to 12000 with very high 125 141 1.15 0.70 ceilings (halls, 250 268 2.15 1.35 hangars) 400 421 3.25 2.15 b Outdoor lighting 700 731 5.4 3.85 b Low light output(1) 1000 1046 8.25 5.30 2000 2140 2080 15 11 6.1 (1) Replaced by sodium vapour lamps. Note: these lamps are sensitive to voltage dips. They extinguish if the voltage falls to less than 50% of their nominal voltage, and will not re-ignite before cooling for approximately 4 minutes. Note: Sodium vapour low-pressure lamps have a light-output efficiency which is superior to that of all other sources. However, use of these lamps is restricted by the fact that the yellow-orange colour emitted makes colour recognition practically impossible. Fig. A8 : Current demands of discharge lamps
In order to design an installation, the actual maximum load demand likely to be imposed on the power-supply system must be assessed. To base the design simply on the arithmetic sum of all the loads existing in the installation would be extravagantly uneconomical, and bad engineering practice. The aim of this chapter is to show how some factors taking into account the diversity (non simultaneous operation of all appliances of a given group) and utilization (e.g. an electric motor is not generally operated at its full-load capability, etc.) of all existing and projected loads can be assessed. The values given are based on experience and on records taken from actual installations. In addition to providing basic installation-design data on individual circuits, the results will provide a global value for the installation, from which the requirements of a supply system (distribution network, MV/LV transformer, or generating set) can be specified.
= the per-unit efficiency = output kW / input kW cos = the power factor = kW / kVA
The apparent-power kVA demand of the load Pa = Pn /( x cos )
(1) From this value, the full-load current From this value, the full-load current Ia (A) taken by the load will be:
Pa x 103 V for single phase-to-neutral connected load From this phase-to-neutral connected load for single value, the full-load current
c Ia = b c Ia = b
Pa x 103 3xU for three-phase balanced load where: load single phase-to-neutral connected for
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(1) For greater precision, account must be taken of the factor of maximum utilization as explained below in 4.3
V = phase-to-neutral voltage (volts) U = phase-to-phase voltage (volts) It may be noted that, strictly speaking, the total kVA of apparent power is not the arithmetical sum of the calculated kVA ratings of individual loads (unless all loads are at the same power factor). It is common practice however, to make a simple arithmetical summation, the result of which will give a kVA value that exceeds the true value by an acceptable design margin. When some or all of the load characteristics are not known, the values shown in Figure A9 next page may be used to give a very approximate estimate of VA demands (individual loads are generally too small to be expressed in kVA or kW). The estimates for lighting loads are based on floor areas of 500 m2.
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Fluorescent lighting (corrected to cos = 0.86) Type of application Estimated (VA/m2) Average lighting fluorescent tube level (lux = lm/m2) with industrial reflector() Roads and highways 7 150 storage areas, intermittent work Heavy-duty works: fabrication and 14 300 assembly of very large work pieces Day-to-day work: office work 24 500 Fine work: drawing offices 41 800 high-precision assembly workshops Power circuits Type of application Estimated (VA/m2) Pumping station compressed air 3 to 6 Ventilation of premises 23 Electrical convection heaters: private houses 115 to 146 flats and apartments 90 Offices 25 Dispatching workshop 50 Assembly workshop 70 Machine shop 300 Painting workshop 350 Heat-treatment plant 700 (1) example: 65 W tube (ballast not included), flux 5,100 lumens (Im), luminous efficiency of the tube = 78.5 Im / W. Fig. A9 : Estimation of installed apparent power
Factor of simultaneity (ks) 1 0.78 0.63 0.53 0.49 0.46 0.44 0.42 0.41 0.40
Example (see Fig. A): 5 storeys apartment building with 25 consumers, each having 6 kVA of installed load. The total installed load for the building is: 36 + 24 + 30 + 36 + 24 = 150 kVA The apparent-power supply required for the building is: 150 x 0.46 = 69 kVA From Figure A10, it is possible to determine the magnitude of currents in different sections of the common main feeder supplying all floors. For vertical rising mains fed at ground level, the cross-sectional area of the conductors can evidently be progressively reduced from the lower floors towards the upper floors. These changes of conductor size are conventionally spaced by at least 3-floor intervals. In the example, the current entering the rising main at ground level is:
150 x 0.46 x 103 400 3 = 100 A
= 55 A
4th floor
6 consumers 36 kVA
0.78
3 rd floor
4 consumers 24 kVA
0.63
2 nd floor
5 consumers 30 kVA
0.53
1st floor
6 consumers 36 kVA
0.49
Fig. A11 : Application of the factor of simultaneity (ks) to an apartment block of 5 storeys
ground floor
4 consumers 24 kVA
0.46
A8
Number of circuits Assemblies entirely tested 2 and 3 4 and 5 6 to 9 10 and more Assemblies partially tested in every case choose
Circuit function Factor of simultaneity (ks) Lighting 1 Heating and air conditioning 1 Socket-outlets 0.1 to 0.2 (1) Lifts and catering hoist (2) b For the most powerful motor 1 b For the second most powerful motor 0.75 b For all motors 0.60 (1) In certain cases, notably in industrial installations, this factor can be higher. (2) The current to take into consideration is equal to the nominal current of the motor, increased by a third of its starting current. Fig. A13 : Factor of simultaneity according to circuit function
Level Utilization
Level 2
Level 3
Apparent Utilization Apparent Simultaneity Apparent Simultaneity Apparent Simultaneity Apparent power factor power factor power factor power factor power (Pa) max. demand demand demand demand kVA max. kVA kVA kVA kVA
Workshop A Lathe
5 5 5 5 2 2 18 3
4 4 4 4 1.6 1.6 18 3
Distribution box
Power circuit
Pedestalno. 1 drill 5 socketoutlets 10/16 A 30 fluorescent lamps Workshop B Compressor 3 socketoutlets 10/16 A 10 fluorescent lamps Workshop C Ventilation no. 1 no. 2 Oven no. 1
0.75
14.4
0.2 1
3.6 3
0.9
18.9
0.8 1 1 1 1 1 1 1 1
1 0.4 1
Distribution box
12 Socket4.3 1
oulets Lighting circuit
Power circuit
LV / MV
15.6 0.9
65
0.9
Workshop C distribution
35
0.9 0.28 1 5 2
Socketoulets Lighting circuit
37.8
Fig A14 : An example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only)
Fig. A15 : Standard apparent powers for MV/LV transformers and related nominal output currents
Apparent power kVA 100 160 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150
In (A) 237 V 244 390 609 767 974 1218 1535 1949 2436 3045 3898 4872 6090 7673
40 V 141 225 352 444 563 704 887 1127 1408 1760 2253 2816 3520 4436
A20
The nominal full-load current In on the LV side of a 3-phase transformer is given by:
U 3 where where b Pa = kVA rating of the transformer b U = phase-to-phase voltage at no-load in volts (237 V or 410 V) b In is in amperes.
In =
Pa x 103
In =
b V = voltage between LV terminals at no-load (in volts) Simplified equation for 400 V (3-phase load) b In = kVA x 1.4 The IEC standard for power transformers is IEC 60076.