27 Plant Electrical Operations questions from the Plant & Utility Ops bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
Free to start: the 2-minute EE readiness check — six questions and a result.
A.controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
B.kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
C.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
D.same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
Answer + AI explanation with Pro
2. Which term means: "same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1"?
Junior
A.Load sharing between paralleled DGs
B.Station DC battery system
C.APFC panel operation
D.Transformer paralleling conditions
Answer + AI explanation with Pro
3. Which statement is correct?
Junior
A.Transformer paralleling conditions — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
B.Transformer paralleling conditions — same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
C.Transformer paralleling conditions — rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
D.Transformer paralleling conditions — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
Answer + AI explanation with Pro
4. What is DG synchronising conditions?
Junior
A.220 V or 110 V lead-acid or Ni-Cd bank with float-boost charger feeding protection, trip coils and emergency lighting; capacity proved by an IEEE 450 discharge test
B.under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
C.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
D.incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
Answer + AI explanation with Pro
5. Which term means: "incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes"?
Junior
A.DG synchronising conditions
B.Transformer paralleling conditions
C.Online double-conversion UPS
D.Fast bus transfer
Answer + AI explanation with Pro
6. Which statement is correct?
Junior
A.DG synchronising conditions — incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
B.DG synchronising conditions — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
C.DG synchronising conditions — same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
D.DG synchronising conditions — in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
Answer + AI explanation with Pro
7. What is Load sharing between paralleled DGs?
Mid
A.kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
B.incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
C.switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer
D.same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
Answer + AI explanation with Pro
8. Which term means: "kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation"?
Mid
A.Load sharing between paralleled DGs
B.APFC panel operation
C.Station DC battery system
D.Transformer paralleling conditions
Answer + AI explanation with Pro
9. Which statement is correct?
Mid
A.Load sharing between paralleled DGs — same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
B.Load sharing between paralleled DGs — under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
C.Load sharing between paralleled DGs — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
D.Load sharing between paralleled DGs — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
Answer + AI explanation with Pro
10. What is Load shedding scheme?
Mid
A.controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
B.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
C.under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
D.incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
Answer + AI explanation with Pro
11. Which term means: "under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island"?
Mid
A.DG synchronising conditions
B.Fast bus transfer
C.Station DC battery system
D.Load shedding scheme
Answer + AI explanation with Pro
12. Which statement is correct?
Mid
A.Load shedding scheme — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
B.Load shedding scheme — in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
C.Load shedding scheme — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
D.Load shedding scheme — under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
Answer + AI explanation with Pro
13. What is Station DC battery system?
Mid
A.same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
B.220 V or 110 V lead-acid or Ni-Cd bank with float-boost charger feeding protection, trip coils and emergency lighting; capacity proved by an IEEE 450 discharge test
C.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
D.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
Answer + AI explanation with Pro
14. Which term means: "220 V or 110 V lead-acid or Ni-Cd bank with float-boost charger feeding protection, trip coils and emergency lighting; capacity proved by an IEEE 450 discharge test"?
Mid
A.Station DC battery system
B.Load sharing between paralleled DGs
C.Online double-conversion UPS
D.Load shedding scheme
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.Station DC battery system — rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
B.Station DC battery system — 220 V or 110 V lead-acid or Ni-Cd bank with float-boost charger feeding protection, trip coils and emergency lighting; capacity proved by an IEEE 450 discharge test
C.Station DC battery system — incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
D.Station DC battery system — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
Answer + AI explanation with Pro
16. What is Online double-conversion UPS?
Junior
A.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
B.220 V or 110 V lead-acid or Ni-Cd bank with float-boost charger feeding protection, trip coils and emergency lighting; capacity proved by an IEEE 450 discharge test
C.same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
D.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
Answer + AI explanation with Pro
17. Which term means: "rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure"?
Junior
A.Transformer paralleling conditions
B.Online double-conversion UPS
C.DG synchronising conditions
D.Load sharing between paralleled DGs
Answer + AI explanation with Pro
18. Which statement is correct?
Junior
A.Online double-conversion UPS — under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
B.Online double-conversion UPS — switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer
C.Online double-conversion UPS — incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
D.Online double-conversion UPS — rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
Answer + AI explanation with Pro
19. What is APFC panel operation?
Mid
A.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
B.kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
C.controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
D.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
Answer + AI explanation with Pro
20. Which term means: "controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831"?
Mid
A.Station DC battery system
B.DG synchronising conditions
C.Load sharing between paralleled DGs
D.APFC panel operation
Answer + AI explanation with Pro
21. Which statement is correct?
Mid
A.APFC panel operation — incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
B.APFC panel operation — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
C.APFC panel operation — under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
D.APFC panel operation — same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
Answer + AI explanation with Pro
22. What is Two-out-of-three interlock?
Mid
A.under-frequency stages such as 49.0, 48.5 and 48.0 Hz, or a PLC acting on incomer trip, drop non-essential feeders in priority so essential loads survive on DG or island
B.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
C.same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
D.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
Answer + AI explanation with Pro
23. Which term means: "in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources"?
Mid
A.Two-out-of-three interlock
B.DG synchronising conditions
C.Station DC battery system
D.APFC panel operation
Answer + AI explanation with Pro
24. Which statement is correct?
Mid
A.Two-out-of-three interlock — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
B.Two-out-of-three interlock — incoming set must match bus voltage, frequency, phase sequence and phase angle, verified by a synchroscope or check-synch relay (ANSI 25) before the breaker closes
C.Two-out-of-three interlock — switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer
D.Two-out-of-three interlock — in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
Answer + AI explanation with Pro
25. What is Fast bus transfer?
Senior
A.switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer
B.in a PCC with two incomers and a bus coupler only two of the three breakers may be closed at once, preventing unsynchronised paralleling of the two sources
C.rectifier-battery-inverter chain that continuously regenerates the output, giving zero transfer time, unlike offline or line-interactive units that switch over on mains failure
D.controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
Answer + AI explanation with Pro
26. Which term means: "switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer"?
Senior
A.Two-out-of-three interlock
B.Fast bus transfer
C.APFC panel operation
D.Transformer paralleling conditions
Answer + AI explanation with Pro
27. Which statement is correct?
Senior
A.Fast bus transfer — kW is shared through governor droop or isochronous load-sharing lines, while kVAr is shared through AVR voltage droop or cross-current compensation
B.Fast bus transfer — controller switches capacitor steps by its C/K setting to hold target PF, with a reconnection delay so the capacitor discharges to 75 V or less within 3 minutes per IEC 60831
C.Fast bus transfer — switches running motors to the standby source within about 100 ms while the phase angle is still small, avoiding the torque and current transients of a slow residual-voltage transfer
D.Fast bus transfer — same voltage ratio and vector group, same phase sequence and polarity, percentage impedances within about 10% of each other and a kVA ratio not beyond 3:1
Answer + AI explanation with Pro
Free to start
Start with a free readiness check
Sign up free for the 2-minute EE readiness check and a scored result. Answers, explanations and the AI tutor on every Plant Electrical Operations question come with Pro.