Testing & Commissioning interview questions

1. A.DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature
2. B.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
3. C.ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
4. D.applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group

Answer + AI explanation with Pro

1. A.Polarisation index
2. B.Secondary injection
3. C.Turns ratio test
4. D.Insulation resistance test

Answer + AI explanation with Pro

1. A.Insulation resistance test — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
2. B.Insulation resistance test — test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
3. C.Insulation resistance test — measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge
4. D.Insulation resistance test — DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature

Answer + AI explanation with Pro

1. A.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
3. C.ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
4. D.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end

Answer + AI explanation with Pro

1. A.Tan delta test
2. B.Insulation resistance test
3. C.Secondary injection
4. D.Polarisation index

Answer + AI explanation with Pro

1. A.Polarisation index — ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
2. B.Polarisation index — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
3. C.Polarisation index — DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
4. D.Polarisation index — test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring

Answer + AI explanation with Pro

1. A.measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge
2. B.ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
3. C.DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
4. D.0.1 Hz withstand at about 2–3 Uo for 15–60 minutes per IEEE 400.2, preferred over DC hipot because DC leaves trapped space charge that damages XLPE

Answer + AI explanation with Pro

1. A.VLF hipot on XLPE cables
2. B.Tan delta test
3. C.Insulation resistance test
4. D.CT polarity flick test

Answer + AI explanation with Pro

1. A.Tan delta test — test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.Tan delta test — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond
3. C.Tan delta test — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
4. D.Tan delta test — measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge

Answer + AI explanation with Pro

1. A.applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group
2. B.0.1 Hz withstand at about 2–3 Uo for 15–60 minutes per IEEE 400.2, preferred over DC hipot because DC leaves trapped space charge that damages XLPE
3. C.ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
4. D.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end

Answer + AI explanation with Pro

1. A.Tan delta test
2. B.Turns ratio test
3. C.VLF hipot on XLPE cables
4. D.Winding resistance test

Answer + AI explanation with Pro

1. A.VLF hipot on XLPE cables — 0.1 Hz withstand at about 2–3 Uo for 15–60 minutes per IEEE 400.2, preferred over DC hipot because DC leaves trapped space charge that damages XLPE
2. B.VLF hipot on XLPE cables — DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature
3. C.VLF hipot on XLPE cables — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
4. D.VLF hipot on XLPE cables — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond

Answer + AI explanation with Pro

1. A.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
3. C.DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
4. D.DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature

Answer + AI explanation with Pro

1. A.Turns ratio test
2. B.CT polarity flick test
3. C.Pre-commissioning checklist
4. D.Winding resistance test

Answer + AI explanation with Pro

1. A.Winding resistance test — applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group
2. B.Winding resistance test — DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
3. C.Winding resistance test — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
4. D.Winding resistance test — measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge

Answer + AI explanation with Pro

1. A.battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond
2. B.applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group
3. C.DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature
4. D.ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak

Answer + AI explanation with Pro

1. A.Pre-commissioning checklist
2. B.Winding resistance test
3. C.Turns ratio test
4. D.Secondary injection

Answer + AI explanation with Pro

1. A.Turns ratio test — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond
2. B.Turns ratio test — applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group
3. C.Turns ratio test — test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
4. D.Turns ratio test — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end

Answer + AI explanation with Pro

1. A.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
3. C.ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise
4. D.0.1 Hz withstand at about 2–3 Uo for 15–60 minutes per IEEE 400.2, preferred over DC hipot because DC leaves trapped space charge that damages XLPE

Answer + AI explanation with Pro

1. A.VLF hipot on XLPE cables
2. B.Polarisation index
3. C.Insulation resistance test
4. D.Secondary injection

Answer + AI explanation with Pro

1. A.Secondary injection — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond
2. B.Secondary injection — test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
3. C.Secondary injection — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
4. D.Secondary injection — ratio of the 10-minute to the 1-minute megger reading; IEEE 43 treats 2.0 or more as acceptable for class B and F insulation and below 1.0 as unsafe to energise

Answer + AI explanation with Pro

1. A.DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
2. B.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
3. C.DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature
4. D.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end

Answer + AI explanation with Pro

1. A.Primary injection
2. B.Winding resistance test
3. C.VLF hipot on XLPE cables
4. D.Secondary injection

Answer + AI explanation with Pro

1. A.Primary injection — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
2. B.Primary injection — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
3. C.Primary injection — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond
4. D.Primary injection — measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge

Answer + AI explanation with Pro

1. A.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
3. C.DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
4. D.battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond

Answer + AI explanation with Pro

1. A.Winding resistance test
2. B.Polarisation index
3. C.CT polarity flick test
4. D.VLF hipot on XLPE cables

Answer + AI explanation with Pro

1. A.CT polarity flick test — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
2. B.CT polarity flick test — applies voltage to the HV side and reads the LV at each tap to confirm the ratio within ±0.5% of nameplate per IEC 60076-1 and to verify the vector group
3. C.CT polarity flick test — measures the dissipation factor of winding, bushing or cable insulation at several voltage steps; a value that rises with voltage (tip-up) points to moisture, voids or partial discharge
4. D.CT polarity flick test — battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond

Answer + AI explanation with Pro

1. A.test kit feeds currents and voltages directly into the relay terminals to prove pick-up, timing and characteristic, without exercising the CTs, PTs or field wiring
2. B.0.1 Hz withstand at about 2–3 Uo for 15–60 minutes per IEEE 400.2, preferred over DC hipot because DC leaves trapped space charge that damages XLPE
3. C.ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak
4. D.battery touched across P1–P2 with positive on P1 gives a positive kick on an analogue meter whose positive lead is on S1, confirming that P1 and S1 correspond

Answer + AI explanation with Pro

1. A.Pre-commissioning checklist
2. B.Polarisation index
3. C.Turns ratio test
4. D.CT polarity flick test

Answer + AI explanation with Pro

1. A.Pre-commissioning checklist — high current from a loading transformer is passed through the primary conductor so CT ratio, polarity, secondary wiring and relay response are proved end to end
2. B.Pre-commissioning checklist — DC resistance of every winding at every tap, compared phase to phase and with factory values within about 2%, to catch loose leads, broken strands or poor OLTC contacts
3. C.Pre-commissioning checklist — DC megger test at 500 V to 5 kV between winding and earth, with a rule-of-thumb minimum of 1 MΩ per kV of rating plus 1 MΩ, corrected to a reference temperature
4. D.Pre-commissioning checklist — ordered proof before first charging: mechanical completion, IR and continuity, relay settings from the approved sheet, trip and interlock checks, then charging and a no-load soak

Answer + AI explanation with Pro