Power Substation

Maintenance
Migration phase

1
Content
1. Electrical Safety

2. Training Objectives

3. Substation Maintenance
 Components of indoor substation

 Switchgear Accessories

4. Video Tutorial

Substation Maintenance 2
Electrical Safety

3
Hazards from electrical

Electrical shocks
 Received when current passes through the body
You become part of the circuit
 Severity of a shock depends on:
-Path of current through the body
-Amount of current flowing through the body
-Length of time the body is in the circuit

Electrical burns
 Occurs when you touch electrical wiring or equipment
that is improperly used or maintained.
 Typically occurs on the hands.
 Very serious injury that needs immediate attention.

Transformer Maintenance 4
How do we protect ourselves

LOCKOUT/TAGOUT
 Ensure by means of locking devices and/or
warning notices that no system
can be re-energized while work is in progress.

 Your personal lock and personal danger tag is what protects you from
systems being re-energized while you are working on them
 You are the only person authorized to remove them except under
specially controlled conditions
 If you don’t install them, you are not protected!

Transformer Maintenance 5
How do we protect ourselves

Always remember
 Never work on an energized
circuit.
Always make sure the system is
already de-energize

 Always Tag and if possible Lock

 Never depend on another person to take the power off a circuit

that you are going to work on.

Transformer Maintenance 6
Training Objectives

7
 Training Objectives:

 Primary objective of maintenance is to ensure a long lasting equipment life cycle without abnormal

failures and outage.

 Maintenance shall ensure that the system is kept in proper operational condition at all times.

 Maintenance shall secure the highest degree of energy availability and reliability.

 Troubleshooting and fault recovery in the shortest possible time.

Substation Maintenance 8
Substation
Maintenance

9
 Condition Monitoring and Maintenance:

 Visual Inspection (every 1-2 years)

 Signs of damage or leakages or flash over.

 Signs of Overheating and insulators appearance.

 Breaker operation counts.

 Non-intrusive condition assessment (every 5-10 years)

 Measurements and testing

 Cleaning

 Fully detailed overhaul (every 10-20 years)

 Dismantling of mechanism/moving parts if required.

Substation Maintenance 10
 Components of Indoor Substation

 Load Break Switch  Switchgear Accessories

 Power Transformer o Relays

 Instrument Transformer o Metering Devices

 Circuit Breaker o Fuses

 Capacitor Banks o Switches

 Bus Bar o Control Wires

o Indication Lamps

Picture 01: KKIA Indoor Substation

Note: There are a total of 63 Westinghouse indoor substations in KKIA
not including CS101, CS102, LC5 and LC3 (new power plant)

Substation Maintenance 11
 Load Break Switch

A load break switch is a disconnect switch that Switch Assembly

has been designed to provide making or  Check insulators, barrier boards, operating
breaking of specified currents. These switches mechanism, connecting links and all insulated
are used to de-energize or energize a circuit. and current carrying parts.
 Check the main blades contact pieces and the
leading edges of the flicker blades for arc
erosion
 Open and close the switch several time to
clean the main contact.
 Check insulator and blade alignment.
 Conduct Contact Resistance and insulation
resistance test.

Substation Maintenance 12
 Power Transformer

 The power transformers are big in size and  Insulation Resistance

used for high power transfer applications,  Winding Resistance Test
where the transmission voltage is greater than  Di electric test or Oil test
33KV.
 Transformer Turns Ratio
 Power transformers are used in transmission
line network of higher voltages for step-up and
step down application (400 kV, 200 kV, 110 kV,
66 kV, 33kV) and are generally rated above
200MVA.

Substation Maintenance 13
 Instrument Transformers

Potential Transformer
Check CT's and VT's for physical appearance
 A potential transformer (P.T.) is an instrument and that all related connections are tight.
transformer which is used for the protection
and measurement purposes in the power In case of withdrawable VT's, the isolating
systems. A potential transformer is mainly contacts should be checked, cleaned and
used to measure high alternating voltage in a lubricated sparingly
power system.

Transformer Maintenance 14
 Instrument Transformers

Current Transformer
Check CT's and VT's for physical appearance
 Current transformers are the current-sensing and that all related connections are tight.
units of the power system and are used
at generating stations, electrical substations, In case of withdrawable VT's, the isolating
and in industrial and commercial electric contacts should be checked, cleaned and
power distribution. lubricated sparingly

Substation Maintenance 15
 Circuit Breakers

Vacuum Circuit Breaker (VCB)

 A vacuum circuit breaker is a kind of circuit

breaker where the arc quenching takes place
in a vacuum medium. The operation of
switching on and closing of current carrying
contacts and interrelated arc interruption takes
place in a vacuum chamber in the breaker
which is called a vacuum interrupter.

Substation Maintenance 16
 Vacuum Circuit Breaker

3 Basic Electrical Tests for Medium-

Voltage Circuit Breakers

 Contact resistance test. The main contacts

and primary stabs need to be checked
periodically to detect abnormal wear,
inadequate lubrication, and loose pivot points
inside the circuit breaker.
 Insulation resistance test.
 Dielectric withstand voltage test.

Substation Maintenance 17
 Vacuum Circuit Breaker

Contact Resistance Test Insulation Resistance Test

The Contact resistance check is not required for An insulation resistance (IR) test measures the
routine maintenance but it is recommended to be total resistance between any two points
performed after any major maintenance that separated by electrical insulation. The test,
requires disassembly of any part of the primary therefore, determines how effective the dielectric
current path. (insulation) is in resisting the flow of electrical
current.

Table 03: Primary Resistance

Substation Maintenance 18
 Vacuum Circuit Breaker

Dielectric withstand voltage test.

 Dielectric breakdown testing is a test to

measure the withstand voltage of materials
used for electrical insulation.

 A dielectric strength test, commonly called a

hipot test, dielectric withstand, or high
potential, is a stress test of the insulation of a
device under test (DUT). Such a test applies a
voltage to the DUT that is much higher than
normal operating voltage; typically 1000V AC
plus twice the normal operating voltage.

Substation Maintenance 19
 Air Circuit Breakers

AIR CIRCUIT BREAKER (ACB)

 Air circuit breaker is a circuit breaker for the
purpose of protecting low voltage circuit,
mainly for energizing and cutting off high
current. It is used as the master of a factory
and building, and as a main circuit breaker of a
ship, and it is possible to attach various
accessories according to the purpose.

Substation Maintenance 20
 Air Circuit Breakers

Clean and lubricate all mechanical linkages.  Contact Resistance Test

Inspect all breakers, remove all covers and arc  Insulation Resistance Test
extinguishing shields, inspect for damage, wear
and deterioration, clean and lubricate as
required. Check, clean and dress (if required) the
main contacts, clean all covers and arc shields.

Substation Maintenance 21
Capacitor Banks:
 Inspect all contacts of power contactor if there is any heating indication and also check the capacitance of the
capacitor.
 Look for indications of overheating and insulation breakdowns. Rectify if any

Switchgear busbars connections:

 Ensure that all connections are tight and that good contact is maintained.

 This examination should include opening the boots for torque checks on the bus bar bolt joints.

Substation Maintenance 22
Substation Switchgear
Accessories

23
 Check the following:

Relays:

 Check the operation of the relays/contactors by energizing the control circuit.

Metering Devices:

 Voltmeters and ammeters

 Energy meters (active or reactive)

 Transducers (voltage, current, watt, var.)

 DC tripping/control supply

Fuses:

 Fuses should be tested for continuity and inspected for signs of deterioration

Substation Maintenance 24
 Check the following:

Switches:

 Auxiliary switches should be kept in a clean and operational condition because they are critical to the correct functioning of the equipment,

especially the protection system.

 Interlocks and locking devices should receive particular attention, especially those associated with earthing and testing facilities

Control Wires:

 Ensure that the connections are tight and good contact is maintained.

 The insulation material should be cleaned and closely examined for any signs of damage such as cracks, tracking marks or peeling.

Indication Lamps:

 Indicating devices such as pilot lamps, semaphores should be tested for good operations and blown/ busted lamps must be replaced.

Substation Maintenance 25
 Clean the following:

 Instrument and Control Panels:

 All dust and dirt found on the top covers should be

brushed off and cleaned prior to commencing any

dismantling to minimize ingress of dirt into internal

portions of the switchgear panel

 Use lint-free clean cloth to clean the switchgears.

Substation Maintenance 26
Video Tutorial

27
Medium Voltage Switchgear

Substation Maintenance 28
Low Voltage Switchgear

Substation Maintenance 29
Thank you
For Participation

Substation Maintenance 30