Power Systems Engineer Licensing Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A three-phase, 50 Hz power system has a line-to-line voltage of 400 V.
What is the phase voltage for a star-connected load?
A. 400 V
B. 230 V
C. 690 V
D. 115 V
B. 230 V
In a star connection, phase voltage equals line voltage divided by √3,
so 400/√3 ≈ 230 V.
2. Which device is primarily used to protect power systems from lightning
surges?
A. Circuit breaker
B. Surge arrester
C. Transformer
D. Reactor
B. Surge arrester
Surge arresters divert high-voltage transient surges safely to ground,
protecting equipment insulation.
,3. The main purpose of a load flow study in power systems is to
determine:
A. Fault current only
B. Voltage, real and reactive power in the system
C. Generator cost only
D. Transformer losses only
B. Voltage, real and reactive power in the system
Load flow analysis calculates steady-state voltage profiles and power
distribution throughout the network.
4. Which power plant has the highest efficiency under ideal conditions?
A. Thermal plant
B. Nuclear plant
C. Hydro plant
D. Diesel plant
C. Hydro plant
Hydroelectric plants convert potential energy directly to mechanical
energy with minimal thermal losses.
5. In a transmission line, corona loss is mainly affected by:
A. Frequency only
B. Conductor size and atmospheric conditions
C. Load current only
D. Transformer rating
B. Conductor size and atmospheric conditions
Corona loss depends on electric field intensity, which is influenced by
conductor diameter and air conditions.
6. The unit of reactive power is:
A. Watt
B. Volt-ampere
C. VAR
, D. Joule
C. VAR
Reactive power is measured in volt-ampere reactive (VAR),
representing energy exchange in AC systems.
7. Which type of transformer is used to measure high voltage in power
systems?
A. Power transformer
B. Distribution transformer
C. Potential transformer
D. Auto transformer
C. Potential transformer
Potential transformers step down high voltages to measurable levels
for instruments and protection devices.
8. The power factor of a purely resistive load is:
A. 0
B. 0.5
C. 1
D. Leading
C. 1
A purely resistive load has voltage and current in phase, giving unity
power factor.
9. Which relay is commonly used for overcurrent protection?
A. Differential relay
B. Buchholz relay
C. Induction disc relay
D. Distance relay
C. Induction disc relay
Induction disc relays operate when current exceeds a preset value,
triggering overcurrent protection.
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A three-phase, 50 Hz power system has a line-to-line voltage of 400 V.
What is the phase voltage for a star-connected load?
A. 400 V
B. 230 V
C. 690 V
D. 115 V
B. 230 V
In a star connection, phase voltage equals line voltage divided by √3,
so 400/√3 ≈ 230 V.
2. Which device is primarily used to protect power systems from lightning
surges?
A. Circuit breaker
B. Surge arrester
C. Transformer
D. Reactor
B. Surge arrester
Surge arresters divert high-voltage transient surges safely to ground,
protecting equipment insulation.
,3. The main purpose of a load flow study in power systems is to
determine:
A. Fault current only
B. Voltage, real and reactive power in the system
C. Generator cost only
D. Transformer losses only
B. Voltage, real and reactive power in the system
Load flow analysis calculates steady-state voltage profiles and power
distribution throughout the network.
4. Which power plant has the highest efficiency under ideal conditions?
A. Thermal plant
B. Nuclear plant
C. Hydro plant
D. Diesel plant
C. Hydro plant
Hydroelectric plants convert potential energy directly to mechanical
energy with minimal thermal losses.
5. In a transmission line, corona loss is mainly affected by:
A. Frequency only
B. Conductor size and atmospheric conditions
C. Load current only
D. Transformer rating
B. Conductor size and atmospheric conditions
Corona loss depends on electric field intensity, which is influenced by
conductor diameter and air conditions.
6. The unit of reactive power is:
A. Watt
B. Volt-ampere
C. VAR
, D. Joule
C. VAR
Reactive power is measured in volt-ampere reactive (VAR),
representing energy exchange in AC systems.
7. Which type of transformer is used to measure high voltage in power
systems?
A. Power transformer
B. Distribution transformer
C. Potential transformer
D. Auto transformer
C. Potential transformer
Potential transformers step down high voltages to measurable levels
for instruments and protection devices.
8. The power factor of a purely resistive load is:
A. 0
B. 0.5
C. 1
D. Leading
C. 1
A purely resistive load has voltage and current in phase, giving unity
power factor.
9. Which relay is commonly used for overcurrent protection?
A. Differential relay
B. Buchholz relay
C. Induction disc relay
D. Distance relay
C. Induction disc relay
Induction disc relays operate when current exceeds a preset value,
triggering overcurrent protection.
