SWITCHGEAR INSPECTION AND TEST PROCEDURE
1) VISUAL INSPECTION
2) WIRING AND FERRULING CHECK
3) BUS CONTINUITY, PHASING AND CONTACT RESISTANCE TEST
4) CURRENT TRANSFORMER CHECKS
5) VOLTAGE TRANSFORMER CHECKS
6) CIRCUIT BREAKER CHECKS
7) TESTING OF METERING ACCURACY BY SECONDARY INJECTION
8) TEST OF PROTECTION RELAYS BY SECONDARY INJECTION
9) PRIMARY CURRENT INJECTION TEST
10) HIGH- POT AND INSULATION RESISTANCE TEST
11) FUNCTIONAL CHECK
VISUAL INSPECTION
1 Check nameplate information for correctness.
2 Inspect enclosures for proper alignment, foundation fixing and grounding.
3 Inspect all covers, panels section and doors for paint work and proper fit.
4 Check for smooth and proper movement of racking mechanisms for alignment, shutters, rollers, rails and guides.
5 Check for proper alignment of the breaker primary and secondary contacts.
6 Check operation of all mechanical interlocks.
7 Check tightness of all bolted connections (torque wrench method).
8 Check bus and supports for defects such as cracked welds, chipped porcelain, cracked insulation, etc., and free of dust accumulation.
9 Verify that all front panel mounted devices (meters, push buttons, switches, indicator lamps, mimic buses, etc.) are installed as per drawings
10 Perform mechanical check and visual inspection on all circuit breakers.
11 Perform mechanical check and visual inspection on all current transformers.
12 Perform mechanical check and visual inspection on all voltage transformers.
13 Perform mechanical check and visual inspection on all disconnected and grounding switches.
14 Check for correct breaker position indication.
15 Check for correct spring status indication (spring charged/discharged).
16 Perform all specific checks on the breaker and spring operating mechanism.
17 Check that all control wiring is correct according to the approved drawing and terminal connections are secure.
BUS CONTINUITY, PHASING AND CONTACT RESISTANCE TEST
2. Check the continuity for each phase and phasing.
3. Check the resistance for all bus bar joint using micro-ohm meter 100 A.
4. The main circuit resistance test shall be performed by100 Ampere DC by micro-ohmmeter from panel to panel on each phase from cable spouts with all circuit breakers racked in service and on position.
5. For judgment, the resistance values from panel to panel should not vary too much if the number of joints and length of bus bar remains the same.
WIRING AND FERRULING CHECK
2 The wire nos. should be checked against the wiring table and the schematic drawing.
CURRENT TRANSFORMER CHECKS
1 Visual Inspection♦ Inspect for physical damage / defects
♦ Check nameplate information for correctness
♦ Check that all grounding cables are securely connected
♦ Check color coded for secondary wiring and size of wires against specs.
♦ Check proper lugs has been used in termination
♦ Check CT’s location physically and secondary terminal labeling printed
2 Insulation resistance test
♦ The insulation resistance shall be checked at the terminals with respect to ground / earth with a 1KV DC Voltage for One minute.
3 Winding resistance measurement
♦ Take CT Resistance measurements at the CT Terminals or at the Terminal Blocks in the LV compartment using a Micro-ohm meter.
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4 Polarity test
♦ Check the CT polarities on the Terminals as per the Schematic Drawing in the LV -compartment for correct polarity.
5 Ratio test by current primary injection
♦ Check the CT ratio by injecting 25%, 50%, 75%, & 100% (if possible) of the normal current on the CT primary winding and measure the corresponding secondary winding current
6 Magnetizing current test (minimum 2 points above )
♦ Check the Magnetization Curves by applying gradually increasing voltage to the CT Secondary and noting the magnetization currents.
♦ Apply the potential at the Terminal Block.
♦ The Readings are entered in the form and the program will automatically print the curves.
♦ The purpose of this test is to ensure that the Knee Point Voltage is correct and most important to ensure the protections and instrumentations are connected to the relevant cores.
♦ The knee point is the point on the magnetization curve at witch 10 % increase in excitation voltage produces 50 % increase in excitation current.
♦ Minimum two points over the knee point shall be taken.
7 Loop resistance measurement test (burden test)
♦ Check the CT Loop Resistance with a Micro-ohm-meter at the extreme end terminals to ensure the complete loop.
8 Phase identification test
• Check Phase identification test by injecting single-phase primary current.
• Check the secondary current in all phases.
• The secondary current should be zero in all phases except the one we injecting current on.
• After primary injection test and with the same arrangement check that the secondary circuit CT terminal shorting / isolation is actually working by closing the shorting link / open the slide link and check the current.
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9 Verify secondary circuits, terminals, shorting/isolating links by primary injection
• During normal HV tests on switchgear or GIS, the CT’s are included in the HV test.
• Shorted the CT’s secondary to ground and isolated from relays and meters.
10 High voltage test.
• It is imperative to ensure that only one end of the CT Secondary is earthed, especially where CT’s are paralleled.
11 Single point earthing check
• After performing all the mentioned tests for the CT, apply voltage greater than the knee point voltage gradually to the CT secondary winding.
• Go back gradually to zero voltage.
12 Demagnetize CT cores after all tests
VOLTAGE TRANSFORMER CHECKS
♦ Check nameplate information for correctness
♦ Check that all grounding cables are securely connected
♦ Check color coded for secondary wiring and size of wires against specs.
♦ Check proper lugs has been used in termination
♦ Check VT’s location physically and secondary terminal labeling printed
1 Winding resistance test
♦ Check the VT Resistance at the VT terminals or at the Terminal Blocks in the LV compartment using a Micro-ohm-meter
2 Insulation resistance test HV/LV/G
• Check the insulation resistance at the terminals with respect to ground / earth.
• The test voltage is 1 KV DC for one minute.
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3 Ratio test
• Apply one, 2 & 3 KV on VT primary terminal.
• Measure the corresponding out put on VT secondary terminal.
• Calculate VT turns ratio.
4 Polarity test
• Check the VT polarities on the LV compartment terminals as per the Schematic Drawing for correct polarity.
5 Check VT HV neutral solidly grounded
6 Verify secondary circuits, terminal to terminal for correctness and tightness
7 Loop resistance test and burden test
• Check the VT Loop Resistance with an ohmmeter at the extreme end terminals to ensure the complete loop.
CIRCUIT BREAKER CHECKS
1 Visual inspections.
• Check nameplate information for correctness.
• Check tightness of all bolted connections (torque wrench method).
• Check all wiring is correct according to approved drawings terminal connections are secured.
• Check quality of paintwork.
• Check that all grounding cables are securely connected.
• Check breakers, truck, rails, for proper alignment and smooth movement.
• Check operation of all mechanical interlocks with associated disconnects, grounding switches, racking truck mechanism, cubicle doors, etc.
• Check for correct breaker position indication (breaker open/closed).
• Check manual spring charge operation.
• Verify correct spring status indication (spring charge d/discharged).
• Verify that correct Dispatch Numbers have been installed.
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2 Contact resistance measurements.
• Close the CB.
• The micro ohmmeter test is conducted with a current of 100 ADC.
• Connect the test set to the first phase of the CB.
• Record the reading.
• Repeat it for all CB phases.
3 High- Pot and insulation resistance Test.
1 Insulation Resistance Test At 5kv DC.
At the CB Closed
• Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
• Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
• Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
• Record the corresponding Insulation Resistance readings.
At the CB Open
• Connect the phases R, Y, B Cable side to the ground.
• Connect the phases R, Y, B Bus side to the test set.
• Record the corresponding Insulation Resistance readings.
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2 High-Pot Test
♦ AC high- pot test shall be carried out in accordance with IEC standard at site.
♦ The test will carry out at test voltage 38 KV fore 60 second.
♦ If the test have been done at factory at 38 kV it will be done at site at 80% of the last time.
At the CB Closed
• Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
• Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
• Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
• Record the corresponding leakage current readings.
At the CB Open
• Connect the phases R, Y, B Cable side to the ground.
• Connect the phases R, Y, B Bus side to the test set.
• Record the corresponding leakage current readings.
3 Insulation Resistance Test Of All Low Voltage Wiring And Cabling At 500 V DC.
• Connect all the wires together (+ve and –ve) or (L and N) and apply the test voltage between the wires and ground.
• Record the corresponding Insulation Resistance readings
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4 Functional check of trip free and anti pump circuits.
♦ The Anti- Pump feature in the Breakers were tested as follows:
♦ The Breaker was closed and the control switch was held in close position.
♦ It was ensured that the breaker closes
♦ The Breaker was tripped as below while the control switch was held in Close position:
A: Manually
B: Electrically
♦ It will be noted from the results that the Breaker does not attempt to re-close if a permanents closing signal is applied.
5 Functional checks of breaker operation counter.
6 Check correct operation of all auxiliary contacts (for breaker open/closed positions).
7 Timing test using an electronic oscillograph.
• Connect the test set to the CB.
• Perform the following operations at the rated DCV.
• Close ( C ) , Open ( O ) , Close - Open ( C – O ) & Open – Close – Open ( O – C – O )
• Record the corresponding readings.
8 Check the correct functioning of interlocks and limits switches.
TESTING OF METERING ACCURACY BY SECONDARY INJECTION
Metering calibration shall be tested via front panel mounted test facilities.
Maximum demand indicator (MDI) meters shall be tested at 10% and 100% of full scale.
Current and voltage metering and transducers calibration shall be tested at 0, 25, 50, 100% of scale.
Watt and VAR metering and transducers calibration shall be tested at (+/- when bi-directional) 0, 25, 50,100% of rated load and with rated voltage and current at angles of 0, 45,180, 225, 270 and 315 degrees.
KWH and KVARH metering calibration shall be tested at 10% and 100% of rated current at angles of 0, 45, 90, 180, 225, 270 and 315 degrees.
Power Factor metering and transducers calibration shall be tested at rated voltage and at 50% lead, unity, 50% lag power factors at 10, 50, 100% rated current.
1 Ammeter check
• Connect the current test set on the ammeter terminals.
• Inject 25, 50 & 100 % of the full-scale current of the ammeter.
• Record the corresponding ammeter readings.
• Inject 100 % of the normal current.
• Record corresponding ammeter reading.
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2 Voltmeter check
• Connect the voltage test set on the voltmeter terminals.
• Apply 25, 50 & 100 % of the full-scale voltage of the voltmeter.
• Record the corresponding voltmeter readings.
• Apply 100 % of the normal voltage.
• Record corresponding voltmeter reading.
3 KWH meter check.
♦ Connect the current test set terminals to the Energy meter current terminals.
♦ Connect the voltage test set terminals to the Energy meter voltage terminals.
♦ Apply 0, 25, 50,100% of rated load and with rated voltage and current at angles of
♦ 0, 45,180, 225, 270 and 315 degrees for time.
♦ Record the corresponding Energy meter readings.
4 KW meter check.
• Connect the current test set terminals to the Power meter current terminals.
• Connect the voltage test set terminals to the Power meter voltage terminals.
• Apply 0, 25, 50,100% of rated load with rated voltage and current at angles of 0, 45,180, 225, 270 and 315 degrees.
• Record the corresponding Power meter readings
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5 Current transducer check
• Connect the current test set on the Current Transducer terminals.
• Inject 25, 50 & 100 % of the full-scale current of the Current Transducer.
• Record the corresponding Current Transducer out put.
• Inject 100 % of the rated current.
• Record corresponding Current Transducer out put.
6 Voltage transducer check
• Connect the Voltage test set on the Voltage Transducer terminals.
• Inject 25, 50 & 100 % of the full-scale Voltage of the Voltage Transducer.
• Record the corresponding Voltage Transducer out put.
• Inject 100 % of the rated Voltage.
• Record corresponding Voltage Transducer out put.
7 KW transducer check
• Connect the current test set terminals to the Power Transducer current terminals.
• Connect the voltage test set terminals to the Power Transducer voltage terminals.
• Apply 0, 25, 50,100% of rated load with rated voltage and current at angles of 0, 45,180, 225, 270 and 315 degrees.
• Record the corresponding Power Transducer O/P readings.
TEST OF PROTECTION RELAYS BY SECONDARY INJECTION
1. Testing Engineer should provide the commissioning manuals and have the detailed understanding for testing and commissioning procedure.
2. All outputs / indications to be tested.
3. Initial tests of new protective relays must include operating characteristics checks for a representative range of available settings with Company approved computer operated test equipment running routines developed for the specific relay and test set involved.
4. Relay auxiliary devices such as external resistors, metrosils, etc. to be tested to conform to required ratings and manufacturer’s information.
5. Final calibration test of all protective relays must be carried out on approved settings, by secondary injection at the front panel mounted test facilities.
6. Auxiliary and tripping relay testing shall include,
7. Pickup and dropout voltage, verification of all contacts.
8. Operation timing at 80% and 100% nominal voltage.
9. Time delay relays shall be tested at 0%, set point and 100% delay.
10. Use of red and green tags for tested relays, meters, etc.
11. All the relays and meters which have been tested and found o.k must have green tags
12. The relays and meters found defective during tests should be tagged red.
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1 Over Current Relay
1. Over Current Pick-Up
♦ Apply the testing relays setting for over current on the relay as following.
o Definite Time Curve with minimum time delay.
o Disable All other protection elements.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Red phase to Neutral.
o Yellow phase to Neutral.
o Blue phase to neutral.
♦ Connect the timer to the relay tripping contact
♦ Slowly increase the current until the relay picked-up.
♦ Record the operating current.
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2. Operating Time Verification
♦ Apply the testing relays setting for over current on the relay as following.
o Disable all other protection elements.
o DT curve with 500ms delay.
o IEC SI curve with 0.1 TMS.
o IEC VI curve with 0.1 TMS.
o IEC EI curve with 0.1 TMS.
o IEC STI curve with 0.1 TMS.
♦ Select the time over current curve one at a time on the relay.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Red phase to Neutral.
o Yellow phase to Neutral.
o Blue phase to neutral.
♦ Connect the timer to the relay tripping contact
♦ Inject testing current and monitor the operating time of the relay.
♦ Record the operating time.
3. Instantaneous Unit Verification
♦ Apply the testing relays setting for over current on the relay as following.
o Disable all other protection elements.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Red phase to Neutral.
o Yellow phase to Neutral.
o Blue phase to neutral.
♦ Connect the timer to the relay tripping contact.
♦ Slowly increase the current until the pick-up indication operates.
♦ Record the operating current.
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2 Earth Fault Relay
1. Earth Fault Pick-Up
♦ Apply the testing relays setting for Earth Fault on the relay as following.
o Definite Time Curve with minimum time delay.
o Disable All other protection elements.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Any phase to Neutral.
♦ Slowly increase the current until the pick-up indication operates.
♦ Record the operating current.
2. Operating Time Verification
♦ Apply the testing relays setting for Earth Fault on the relay as following.
o Disable all other protection elements.
o DT curve with 500ms delay.
o IEC SI curve with 0.1 TMS.
o IEC VI curve with 0.1 TMS.
o IEC EI curve with 0.1 TMS.
o IEC STI curve with 0.1 TMS.
♦ Select the time Earth Fault curve one at a time on the relay.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Any phase to Neutral.
♦ Connect the timer to the relay tripping contact
♦ Inject testing current and monitor the operating time of the relay.
♦ Record the operating time.
3. Instantaneous Unit Verification
♦ Apply the testing relays setting for Earth Fault on the relay as following.
o Disable all other protection elements.
♦ Connect the current test set on the relay current terminals one at a time as following.
o Any phase to Neutral.
♦ Connect the timer to the relay tripping contact.
♦ Slowly increase the current until the pick-up indication operates.
♦ Record the operating current.
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3 Under Voltage Protection Relay
1. Under Voltage Verification
♦ Apply the testing relays setting with instantaneous tripping time on the relay
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Slowly Decrease the applied voltage until the relay pick-up
♦ Record the pick-up voltage 9.3.2. Delay Time Verification
♦ Select the operating time on the relay
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Apply the testing voltage and monitor the operating time of the relay
♦ Record the operating time.
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4 Neutral Over Voltage Protection Relay
1 Neutral Over Voltage Verification
♦ Apply the testing relays setting with instantaneous tripping time on the relay
♦ Connect the voltage test set on the relay terminals
♦ Connect the timer to the relay tripping contact
♦ Slowly increase the applied voltage until the relay pick-up
♦ Record the pick-up voltage
2 Delay Time Verification
♦ Select the operating time on the relay
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Apply the testing voltage and monitor the operating time of the relay
♦ Record the operating time.
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5 Trip Circuit Supervision Relay
1 Voltage Pick-Up Verification
♦ Slowly increase the voltage until the relay pick-up
♦ Record the pick-up voltage.
2 Voltage Drop-Out Verification
♦ Slowly increase the voltage until the relay pick-up
♦ While relay is still picking-up slowly reduce the voltage until the relay dropout.
♦ Record the dropout voltage.
3 Function Check
♦ All the internal and external wiring should be completed
1 The CB Is In Open Position
• At the CB control panel / box open tripping coils circuit one by one
• The trip circuit supervision relay should operate in each time
1 The CB In Close Position
♦ At the CB control panel / box open tripping coils circuit one by one
♦ The trip circuit supervision relay should operate in each time
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6 Tripping Relay
1 Voltage Pick-Up Verification
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Slowly increase the voltage until the relay pick-up
♦ Record the pick-up voltage 9.6.2 Voltage Drop-Out Verification
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Slowly increase the voltage until the relay pick-up
♦ While relay is still picking-up slowly reduce the voltage until the relay dropout
♦ Record the dropout voltage
1 Delay Time Verification
♦ Connect the voltage test set on the relay voltage terminals
♦ Connect the timer to the relay tripping contact
♦ Apply the testing voltage and monitor the operating time of the relay
♦ Record the operating time.
10 PRIMARY CURRENT INJECTION TEST
• As per Current transformers scheme
11 HIGH- POT AND INSULATION RESISTANCE TEST
1 Insulation Resistance Test At 5kv DC.
At the CBs in Service and Closed
• Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
• Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
• Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
• Record the corresponding Insulation Resistance readings.
At the CBs in Service and Open
• Connect the phases R, Y, B Cable side to the ground.
• Connect the phases R, Y, B Bus side to the test set.
• Record the corresponding Insulation Resistance readings.
2 High-Pot Test
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♦ AC high- pot test shall be carried out in accordance with IEC standard at site.
♦ The test will carry out at test voltage 38 KV fore 60 second.
♦ If the test have been done at factory at 38 kV it will be done at site at 80% of the last time.
♦ At the CBs in Service and Closed
• Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
• Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
• Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
• Record the corresponding leakage current readings.
♦ At the CBs in Service and Open
• Connect the phases R, Y, B Cable side to the ground.
• Connect the phases R, Y, B Bus side to the test set.
• Record the corresponding leakage current readings.
3 Insulation Resistance Test Of All Low Voltage Wiring And Cabling At 500 V DC.
• Connect all the wires together (+ve and –ve) or (L and N) and apply the test voltage between the wires and ground.
• Record the corresponding Insulation Resistance readings
12 FUNCTIONAL CHECK
As per control scheme
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