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LADWP ELECTRIC STATION OPERATOR (ESO) EXAM
2026/2027 COMPLETE (100) CURRENT TESTING
QUESTIONS AND CORRECT ANSWERS WITH DETAILED
RATIONALES.
LADWP
Prepare for the LADWP Electric Station Operator Exam with a focused study resource
designed to reinforce essential electrical power system and station operation
concepts. It supports review of all key domains including power system
fundamentals, circuit breakers, disconnect switches, transformers, switching
operations, safety protocols, and emergency procedures. Use the material to
strengthen technical knowledge, improve problem-solving skills, and identify areas
that may require additional review before the assessment. This resource is best suited
for aspiring Electric Station Operators, utility personnel, electrical technicians, and
candidates preparing for the LADWP Electric Station Operator examination.
MULTIPLE CHOICE.
SECTION 1: POWER SYSTEM FUNDAMENTALS & ELECTRICAL THEORY
(Questions 1-20)
1. What is the standard frequency for the LADWP bulk power system
interconnecting with the Western Interconnection?
a) 50 Hz
b) 60 Hz
c) 400 Hz
d) 25 Hz
Answer: b) 60 Hz
Rationale: The Western Interconnection, which includes LADWP, operates at
a nominal frequency of 60 Hz. The United States power grid operates at 60 Hz,
while many other countries use 50 Hz.
2. What is the primary purpose of a power transformer in a substation?
a) To convert AC to DC
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b) To change voltage levels while maintaining the same frequency
c) To increase the frequency of the power
d) To store electrical energy
Answer: b) To change voltage levels while maintaining the same frequency
Rationale: Transformers operate on the principle of electromagnetic
induction to step up or step down voltage. They do not change frequency,
which is determined by generator speed.
3. A three-phase 480V system operates in a wye configuration. What is the
phase-to-neutral voltage?
a) 120V
b) 208V
c) 277V
d) 480V
Answer: c) 277V
Rationale: In a wye-connected system, phase-to-neutral voltage equals line-
to-line voltage divided by the square root of 3 (√3). V_phase = .732 =
277V.
4. A potential transformer (PT) with a ratio of 2000:1 produces a secondary
reading of 115V. What is the primary voltage?
a) 115 kV
b) 200 kV
c) 230 kV
d) 345 kV
Answer: c) 230 kV
Rationale: Primary voltage = PT ratio × secondary reading = 2000 × 115V =
230,000V = 230 kV.
5. A circuit has a resistance of 6 ohms and a reactance of 8 ohms. What is
the total impedance?
a) 7.2 ohms
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b) 10 ohms
c) 14 ohms
d) 48 ohms
Answer: b) 10 ohms
Rationale: Impedance is calculated using Z = √(R² + X²). Z = √(36 + 64) = √100
= 10 ohms.
6. A three-phase motor draws 100A at 4,160V with a power factor of 0.8.
What is the true power (kW)?
a) 576 kW
b) 333 kW
c) 576 kVA
d) 416 kW
Answer: a) 576 kW
Rationale: P (kW) = (√3 × V × I × PF) / 1000. (1.732 × 4160 × 100 × 0.8) / 1000 =
576.4 kW.
7. What is the peak voltage of a standard 120V RMS AC waveform?
a) 120V
b) 169.7V
c) 240V
d) 84.8V
Answer: b) 169.7V
Rationale: V_peak = V_RMS × √2. 120V × 1.414 = 169.68V. This is important
for insulation testing and dielectric strength.
8. A three-phase load draws 500 kW of real power with an apparent power
of 600 kVA. What is the power factor?
a) 0.72
b) 0.80
c) 0.83
d) 0.90
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Answer: c) 0.83
Rationale: Power Factor = Real Power (P) ÷ Apparent Power (S) = 500 kW ÷ 600
kVA = 0.83.
9. One of the primary tasks of the Electric Station Operator is the ______ of
high-voltage circuits.
a) Maintenance
b) Switching
c) Design
d) Monitoring
Answer: b) Switching
Rationale: Switching high-voltage circuits is a core responsibility of Electric
Station Operators, involving the opening and closing of circuits to isolate
equipment, clear faults, or reconfigure the power system.
10. __________ switching is performed for maintenance, construction,
cleaning, and testing purposes.
a) Emergency
b) Automatic
c) Routine
d) Manual
Answer: c) Routine
Rationale: Routine switching is planned work performed for maintenance,
construction, cleaning, and testing of equipment.
11. __________ switching operations include automatic reclosers (ARs),
Voltage Pickup Units (VPUs), and Automatic Transfer Switching (ATSs).
a) Manual
b) Emergency
c) Routine
d) Automatic
Answer: d) Automatic
LADWP ELECTRIC STATION OPERATOR (ESO) EXAM
2026/2027 COMPLETE (100) CURRENT TESTING
QUESTIONS AND CORRECT ANSWERS WITH DETAILED
RATIONALES.
LADWP
Prepare for the LADWP Electric Station Operator Exam with a focused study resource
designed to reinforce essential electrical power system and station operation
concepts. It supports review of all key domains including power system
fundamentals, circuit breakers, disconnect switches, transformers, switching
operations, safety protocols, and emergency procedures. Use the material to
strengthen technical knowledge, improve problem-solving skills, and identify areas
that may require additional review before the assessment. This resource is best suited
for aspiring Electric Station Operators, utility personnel, electrical technicians, and
candidates preparing for the LADWP Electric Station Operator examination.
MULTIPLE CHOICE.
SECTION 1: POWER SYSTEM FUNDAMENTALS & ELECTRICAL THEORY
(Questions 1-20)
1. What is the standard frequency for the LADWP bulk power system
interconnecting with the Western Interconnection?
a) 50 Hz
b) 60 Hz
c) 400 Hz
d) 25 Hz
Answer: b) 60 Hz
Rationale: The Western Interconnection, which includes LADWP, operates at
a nominal frequency of 60 Hz. The United States power grid operates at 60 Hz,
while many other countries use 50 Hz.
2. What is the primary purpose of a power transformer in a substation?
a) To convert AC to DC
, Page 2 of 32
b) To change voltage levels while maintaining the same frequency
c) To increase the frequency of the power
d) To store electrical energy
Answer: b) To change voltage levels while maintaining the same frequency
Rationale: Transformers operate on the principle of electromagnetic
induction to step up or step down voltage. They do not change frequency,
which is determined by generator speed.
3. A three-phase 480V system operates in a wye configuration. What is the
phase-to-neutral voltage?
a) 120V
b) 208V
c) 277V
d) 480V
Answer: c) 277V
Rationale: In a wye-connected system, phase-to-neutral voltage equals line-
to-line voltage divided by the square root of 3 (√3). V_phase = .732 =
277V.
4. A potential transformer (PT) with a ratio of 2000:1 produces a secondary
reading of 115V. What is the primary voltage?
a) 115 kV
b) 200 kV
c) 230 kV
d) 345 kV
Answer: c) 230 kV
Rationale: Primary voltage = PT ratio × secondary reading = 2000 × 115V =
230,000V = 230 kV.
5. A circuit has a resistance of 6 ohms and a reactance of 8 ohms. What is
the total impedance?
a) 7.2 ohms
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b) 10 ohms
c) 14 ohms
d) 48 ohms
Answer: b) 10 ohms
Rationale: Impedance is calculated using Z = √(R² + X²). Z = √(36 + 64) = √100
= 10 ohms.
6. A three-phase motor draws 100A at 4,160V with a power factor of 0.8.
What is the true power (kW)?
a) 576 kW
b) 333 kW
c) 576 kVA
d) 416 kW
Answer: a) 576 kW
Rationale: P (kW) = (√3 × V × I × PF) / 1000. (1.732 × 4160 × 100 × 0.8) / 1000 =
576.4 kW.
7. What is the peak voltage of a standard 120V RMS AC waveform?
a) 120V
b) 169.7V
c) 240V
d) 84.8V
Answer: b) 169.7V
Rationale: V_peak = V_RMS × √2. 120V × 1.414 = 169.68V. This is important
for insulation testing and dielectric strength.
8. A three-phase load draws 500 kW of real power with an apparent power
of 600 kVA. What is the power factor?
a) 0.72
b) 0.80
c) 0.83
d) 0.90
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Answer: c) 0.83
Rationale: Power Factor = Real Power (P) ÷ Apparent Power (S) = 500 kW ÷ 600
kVA = 0.83.
9. One of the primary tasks of the Electric Station Operator is the ______ of
high-voltage circuits.
a) Maintenance
b) Switching
c) Design
d) Monitoring
Answer: b) Switching
Rationale: Switching high-voltage circuits is a core responsibility of Electric
Station Operators, involving the opening and closing of circuits to isolate
equipment, clear faults, or reconfigure the power system.
10. __________ switching is performed for maintenance, construction,
cleaning, and testing purposes.
a) Emergency
b) Automatic
c) Routine
d) Manual
Answer: c) Routine
Rationale: Routine switching is planned work performed for maintenance,
construction, cleaning, and testing of equipment.
11. __________ switching operations include automatic reclosers (ARs),
Voltage Pickup Units (VPUs), and Automatic Transfer Switching (ATSs).
a) Manual
b) Emergency
c) Routine
d) Automatic
Answer: d) Automatic
