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PRE COMMISSIONING TEST PROCEDURE FOR LT PANEL

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PRE COMMISSIONING TEST PROCEDURE F0R LT PANEL

This procedure is prepared to carry out various pre- commissioning tests to be conducted in systematic manner for LT Panel to ensure the healthiness and performance of the LT Panel

Scope

This procedure covers the Pre commissioning test for LT Panel as for the following

  1. CRM Test for Circuit Breaker
  2. IR Test for Circuit Breaker
  3. Timer Test for Circuit Breaker
  4. CRM Test for Bus Bar
  5. IR Test for Bus Bar
  6. CT Test
  7. PT Test

Resources – Tools and Equipment Required

  1. For CRM Test:
  • CRM kit
  • Connecting cables
  • Insulated Hand tools
  1. For Insulation Resistance measurement Test (IR Test):
  • Test Leads
  • 500 V, 5000 V Insulation Tester
  • Insulated Hand Tools
  1. For Timing Measurement Test
  • Timer Kit
  • Testing leads
  • Insulated Hand Tools
  1. Winding resistance test
  • Multimeter with leads
  • Coil Resistance measurement

Operational Sequence of work(Test Procedure)

Contact Resistance Measurement Test (Pole to Pole):

  1. Take the work permit from the client
  2. Ensure zero energy in the Bus Bar
  3. Keep the Breaker in closed condition
  4. Connect the earth from CRM kit to earth plate or earth pit
  5. Connect the CRM kit Current and Voltage leads across the Breaker contact R & R’
  6. Connect the CRM kit in A.C supply extension board with ELCB rated with 30 mA
  7. Inject the rated current to the Circuit Breaker
  8. Note down the contact resistance value from the CRM kit
  9. Repeat the above test for another phases (Y & Y’) & (B & B’)
  10. Switch off the power supply to the CRM Kit and disconnect them
DO’s DON’TS
  • Breaker should be in closed position.
  • Voltage leads should be connected inside the Current leads.
  • While doing this test, no external cables should be connected.
  • Proper grounding should be done for the kit.
  • Don’t change the connection sequence (i.e., V+, C+ should be connected to R or Y or B & V-, C- should be connected to R’ or Y’ or B’ ).
  • Don’t change the supply configuration (i.e., voltage should be applied outside the current leads).
  • Contacts should not have any dust during this test.

IR TEST (BREAKER OPEN CONDITION)

  1. Keep the Circuit Breaker in open position
  2. Connect the IR kit across the RØ Breaker contact (R & R’)
  3. Select the required voltage range in IR kit
  4. Switch ON the IR kit and press the test button take down the reading
  5. Repeat the above steps for the other phases (YØ & BØ)
  6. Discharge the voltage from the Circuit Breaker with respect to

IR TEST BETWEEN PHASE TO EARTH (BREAKER CLOSED CONDITION)

  1. Keep the Circuit Breaker in closed position
  2. Connect the IR kit Positive lead with RØ Breaker contact
  3. Connect the IR kit Negative lead with earth
  4. Select the required voltage range in IR kit
  5. Switch ON the IR kit and press the test button take down the reading
  6. Repeat the above steps for the other phases (YØ & BØ)
  7. Discharge the voltage from the Circuit Breaker with respect to
DO’S DON’TS
  • Remove all external wires from the CB contacts.
  • Check the calibration due of the test equipment
  • Ensure zero resistance when line and earth are shorted and switched on to know the zero value for the proper working of kit.
  • Keep some distance while doing the test.
  • After Insulation resistance test completion, note down the values and discharge the CT terminals and remove the test cables
  • Ambient temperature must be noted.
  • Don’t touch any cables and the kit when it is in running condition.
  • Don’t touch any bushing while doing the tests
  • Don’t connect any transmission line cables to the contacts.
  • Don’t test with damaged cables and improper clips
  • Don’t work in wet (rainy) conditions
  • Don’t lose your concentration while testing.

 

Timing Test for circuit Breaker:

  1. Keep the Breaker in closed condition
  2. Connect the earth from Timer kit to earth plate or earth pit
  3. Connect the Timer kit feedback cables R and R’ leads across the RØ Breaker contact
  4. Connect the Timer kit feedback cables Y and Y’ leads across the YØ Breaker contact
  5. Connect the Timer kit feedback cables B and B’ leads across the BØ Breaker contact
  6. Connect the Timer kit in A.C supply extension board with ELCB rated with 30 mA
  7. Give The open command and note down the value from the timer kit
  8. Give the close command and note the value from the timer Kit
  9. Give the close/open command and note the value from the timer kit
  10. Switch off the power supply to the Timer Kit and disconnect them
DO’s DON’TS
 

  • Charge the spring motor manually or electrically to close the CB and to measure the time.
  • While doing this test, no external cables should be connected.
  • Proper grounding should be done for the kit.
  • Check the three phase contacts’ switching times are in the specified limit and the same.
  • Don’t supply improper voltage to the tripping and closing coils (i.e., for 110V coil, 110V should be applied).
  • Don’t give the supply with fluctuations.
  • Don’t remove the power pack cables without discharging.

 

Contact Resistance Measurement (CRM) Test – Bus Bar

  1. Take the work permit from the client
  2. Ensure zero energy in the Bus Bar
  3. Disconnect Bus bar from the transformer
  4. Connect the earth from CRM kit to earth plate or earth pit
  5. Connect the CRM kit voltage leads to across the(R-Phase) Bus Bar joint
  6. Connect the CRM kit current leads to across the(R-Phase) Bus Bar Joint, at the same time Voltage leads should be connected inside the current leads
  7. Ensure that all the connections are connected properly
  8. Connect the CRM kit in A.C supply extension board with ELCB rated with 30 mA
  9. Apply the rated current to the Bus bar
  10. Note down the resistance value from the CRM kit
  11. Repeat the above procedures for remaining (YØ & BØ)Phases for CRM Test
  12. Switch off the supply to the CRM Kit and disconnect the connections
DO’s DON’TS
 

  • Ensure the bus bar is in the zero energy condition
  • Voltage leads should be connected inside the Current leads.
  • While doing this test, no external cables should be connected in the bus bar.
  • Proper grounding should be done for the kit.
  • Check the tightness for the bus bar joints
  

  • Don’t change the connection sequence (i.e., V+, C+ should be connected to R or Y or B & V-, C- should be connected to R’ or Y’ or B’ ).
  • Don’t change the supply configuration (i.e., voltage should be applied outside the current leads).
  • Contacts should not have any dust during this test.

 

IR TEST BETWEEN PHASE TO EARTH (BUS BAR):

  1. Check the Bus Bar tightness and panel earthing
  2. Connect the IR kit Positive lead with RØ Bus Bar
  3. Then connect the IR kit Negative lead with earth
  4. Select the required voltage range in IR kit
  5. Switch “ON” the IR kit and press the test button take down the reading
  6. Switch “OFF” the IR kit
  7. Discharge the potential from the bus bar with respect to earth
  8. Repeat the above steps for the other Bus bar phases (YØ & BØ)

IR TEST BETWEEN PHASE TO PHASE (BUS BAR):

  1. Connect the IR Kit across the RØ-YØ Bus Bar
  2. Select the required voltage range in IR kit
  3. Switch “ON” the IR kit and press the test button take down the reading
  4. Switch “OFF” the IR kit
  5. Discharge the potential from the Bus bar with respect to earth
  6. Repeat the above steps for the other Bus bar phases (YØ-BØ) &( BØ-RØ)
Do’s Don’ts
 

  • Personal Protective equipment (PPE) should be used while testing
  • All the testing equipment must be connected to the proper earth line
  • Ensure all the connections are in tight after testing
  • Ensure the external wires are removed from isolator
  • Before doing testing, discharge the Isolator terminals.
  • Test equipment’s to ensure zero energy state before beginning the work
  • Discharge the Bus bar after each test
  

  • Unauthorized persons should not enter the testing premises.
  • Avoid contact with energized electrical circuits
  • Do not use the twisted testing cables
  • Never bypass fuses and circuit breakers.
  • Don’t use the joint cables while testing.
  • Avoid testing during rainy season.
  • Do not make connection changes while testing

 

Insulation Resistance (IR) Test for CT Primary to Earth:

  1. Connect the Earth lead of the IR kit to the earth Terminal
  2. Connect HV lead of the IR kit to either P1 or P2 of the current Transformer
  3. Switch “ON” the IR kit and Select the required voltage range in IR kit
  4. press the Test button take down the readings
  5. Switch “OFF” the IR kit

Primary to Secondary:

  1. Connect HV lead of the IR kit to either P1 or P2 of the current Transformer
  2. Connect Earth lead of the IR kit to either S1 or S2 of the current Transformer
  3. Switch “ON” the IR kit and Select the required voltage range in IR kit
  4. press the Test button take down the readings
  5. Switch “OFF” the IR kit

Secondary to Earth:

  1. Connect Earth lead of the IR kit to the earth terminal
  2. Connect HV lead of the IR kit to either S1 or S2 of the current Transformer
  3. Switch “ON” the IR kit and Select the required voltage range in IR kit
  4. press the Test button take down the readings
  5. Switch “OFF” the IR kit

Between Secondary Cores:

  1. Connect HV lead of the IR kit to either S1 or S2 of the current Transformer
  2. Connect Earth lead of the IR kit to either S1 or S2 of the other core of the current Transformer
  3. Switch “ON” the IR kit and Select the required voltage range in IR kit
  4. press the Test button take down the readings
  5. Switch “OFF” the IR kit
  6. Discharge the voltage from the CT with respect to earth.
DO’S DON’TS
 

  • Check all the CT secondary wires are isolated
  • Check the calibration due of the test equipment
  • Breaker should be in open condition and in test position.
  • Ensure zero resistance when line and earth are shorted and switched on to know the zero value for the proper working of kit.
  • Keep some distance while doing the test.
  • After Insulation resistance test completion, note down the values and discharge the CT terminals and remove the test cables
  • Ambient temperature must be noted.
  

  • Don’t touch any cables and the kit when it is in running condition.
  • Don’t touch any bushing while doing the tests
  • Don’t keep the breaker in service and on position
  • Don’t test with damaged cables and improper clips
  • Don’t work in wet (rainy) conditions
  • Don’t lose your concentration while testing.

 

Polarity test for CT:

  1. Connect the secondary S1 terminal to galvanometer positive terminal and S2 to the negative terminal
  2. Touch the battery positive terminal to P1 in and negative terminal to the P2 terminal at the CT primary winding Terminals
  3. Check the deflection in the galvanometer
  4. It must be in clock-wise direction
DO’S DONT’S
 

  • Check the connections as per the diagram.
  • Check the CT secondary cable continuity from CT secondary to CT terminal block.
  • Check whether the battery is charged or not
  • Verify the galvanometer in good condition
  

  • Don’t use low batteries for testing
  • Don’t apply the charge continuously (apply single pulse).

Ratio test for CT

  1. Connect the variac and loading transformer
  2. Connect the loading transformer across the primary terminals(P1,P2)
  3. connect the variac in A.C supply extension board With ELCB rated with 30mA
  4. Inject the current across the primary terminals.
  5. Short Secondary
  6. Note down the corresponding secondary current at various cores.
  7. Switch off the supply to the primary injection kit
DO’S DONT’S
 

  • Check the current leakage testers are calibrated
  • Check the input voltage levels for avoid voltage variation, fluctuations
  • Connect the welding cables with full tightness in the loading transformer and CT primary terminals.
  • 80% of the rated current should be applied in the CT primary and measure the secondary current values.
  • Measure the CT secondary current in meters and relays end points.
  • Single point earthing should be taken in the CT secondary circuits.
  • Make the variac slowly to Zero position and remove the cables.
  

  • Don’t leave any CT secondary terminals in open condition during the test.
  • Multiple earthing should not in the CT secondary circuits
  • No loose connections should be in the CT secondary circuits.
  • Don’t leave the spare core in open condition.

 

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