2025/2026 LADWP ELECTRIC STATION OPERATOR
EXAM: VERIFIED QUESTIONS AND ANSWERS STUDY
GUIDE FOR CIRCUIT BREAKERS, DISCONNECTS &
TRANSFORMERS
SECTION 1: ELECTRICAL THEORY AND FUNDAMENTALS
1. An Electric Station Operator is monitoring a 34.5 kV bus and observes that the line-to-
line voltage has dropped to 31 kV. What is the approximate percentage voltage drop from
nominal?
A. 5.2%
B. 10.1%
C. 15.3%
D. 20.4%
Answer: B
2. In a three-phase AC system, the phase-to-phase voltage is 480 volts. What is the
approximate phase-to-neutral voltage?
A. 240 volts
,B. 277 volts
C. 340 volts
D. 480 volts
Answer: B
3. An operator measures zero-sequence current flowing through a transformer neutral. This
indicates:
A. Balanced three-phase loading
B. An unbalanced fault condition or ground fault
C. Normal capacitive charging current
D. Transformer core saturation
Answer: B
4. An Electric Station Operator is performing switching on a 230 kV circuit. Which
parameter is MOST critical to verify before opening a circuit breaker to de-energize the line?
A. Ambient temperature
B. Load current on the circuit
C. Humidity level
D. Time of day
Answer: B
,5. Which law states that the current through a conductor between two points is directly
proportional to the voltage across the two points, provided the temperature remains
constant?
A. Faraday's Law
B. Ohm's Law
C. Kirchhoff's Voltage Law
D. Lenz's Law
Answer: B
6. In a purely resistive AC circuit, the RMS voltage is ___ times the peak voltage.
A. 0.5
B. 0.707
C. 1.0
D. 1.414
Answer: B
7. A transformer has a 10% impedance on its own 100 MVA base. What is the per-unit
reactance of this transformer?
A. 0.01 pu
B. 0.10 pu
C. 1.00 pu
D. 10.00 pu
, Answer: B
8. When two identical transformers are connected in parallel, what is the effect on the
equivalent impedance compared to a single transformer?
A. It doubles
B. It remains the same
C. It is reduced by half
D. It is reduced to one-quarter
Answer: C
9. An operator observes a wattmeter reading negative power flow on a circuit that normally
exports power. This indicates:
A. Normal power flow direction
B. Power flow has reversed direction (import instead of export)
C. The meter is calibrated incorrectly
D. Reactive power is being consumed
Answer: B
10. In a substation, the potential transformer (PT) ratio is 2000:1. If the secondary voltmeter
reads 115 volts, what is the primary voltage?
A. 57.5 kV
EXAM: VERIFIED QUESTIONS AND ANSWERS STUDY
GUIDE FOR CIRCUIT BREAKERS, DISCONNECTS &
TRANSFORMERS
SECTION 1: ELECTRICAL THEORY AND FUNDAMENTALS
1. An Electric Station Operator is monitoring a 34.5 kV bus and observes that the line-to-
line voltage has dropped to 31 kV. What is the approximate percentage voltage drop from
nominal?
A. 5.2%
B. 10.1%
C. 15.3%
D. 20.4%
Answer: B
2. In a three-phase AC system, the phase-to-phase voltage is 480 volts. What is the
approximate phase-to-neutral voltage?
A. 240 volts
,B. 277 volts
C. 340 volts
D. 480 volts
Answer: B
3. An operator measures zero-sequence current flowing through a transformer neutral. This
indicates:
A. Balanced three-phase loading
B. An unbalanced fault condition or ground fault
C. Normal capacitive charging current
D. Transformer core saturation
Answer: B
4. An Electric Station Operator is performing switching on a 230 kV circuit. Which
parameter is MOST critical to verify before opening a circuit breaker to de-energize the line?
A. Ambient temperature
B. Load current on the circuit
C. Humidity level
D. Time of day
Answer: B
,5. Which law states that the current through a conductor between two points is directly
proportional to the voltage across the two points, provided the temperature remains
constant?
A. Faraday's Law
B. Ohm's Law
C. Kirchhoff's Voltage Law
D. Lenz's Law
Answer: B
6. In a purely resistive AC circuit, the RMS voltage is ___ times the peak voltage.
A. 0.5
B. 0.707
C. 1.0
D. 1.414
Answer: B
7. A transformer has a 10% impedance on its own 100 MVA base. What is the per-unit
reactance of this transformer?
A. 0.01 pu
B. 0.10 pu
C. 1.00 pu
D. 10.00 pu
, Answer: B
8. When two identical transformers are connected in parallel, what is the effect on the
equivalent impedance compared to a single transformer?
A. It doubles
B. It remains the same
C. It is reduced by half
D. It is reduced to one-quarter
Answer: C
9. An operator observes a wattmeter reading negative power flow on a circuit that normally
exports power. This indicates:
A. Normal power flow direction
B. Power flow has reversed direction (import instead of export)
C. The meter is calibrated incorrectly
D. Reactive power is being consumed
Answer: B
10. In a substation, the potential transformer (PT) ratio is 2000:1. If the secondary voltmeter
reads 115 volts, what is the primary voltage?
A. 57.5 kV
