Power Systems Engineer Licensing Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A three-phase power system has a balanced load connected in a star
configuration. If the line voltage is 400 V, what is the phase voltage across
each load impedance?
A. 400 V
B. 346 V
C. 231 V
D. 200 V
B. 346 V
In a balanced star-connected system, the phase voltage is equal to the line
voltage divided by √3. Therefore, 400/√3 ≈ 231 V, making option C correct.
2. In a power system, the main purpose of a circuit breaker is to:
,A. Increase system voltage stability
B. Interrupt fault currents safely
C. Reduce transmission losses
D. Improve generator efficiency
B. Interrupt fault currents safely
Circuit breakers are protective switching devices designed to interrupt
abnormal currents such as short circuits while allowing normal system
operation.
3. The per-unit system in power engineering is mainly used because it:
A. Eliminates the need for transformers
B. Simplifies calculations across different voltage levels
C. Increases generator output power
D. Removes the need for protective relays
B. Simplifies calculations across different voltage levels
The per-unit system normalizes electrical quantities, making calculations
involving different voltage levels and equipment ratings easier and less
error-prone.
4. A synchronous generator operates at 50 Hz and has 20 poles. What is
its synchronous speed?
,A. 150 rpm
B. 300 rpm
C. 600 rpm
D. 1500 rpm
C. 300 rpm
The synchronous speed is calculated using Ns = 120f/P. For 50 Hz and 20
poles, Ns = (120 × 50)/20 = 300 rpm.
5. The primary function of a power transformer in a transmission system
is to:
A. Convert AC power into DC power
B. Increase or decrease voltage levels
C. Generate electrical energy
D. Store electrical energy
B. Increase or decrease voltage levels
Power transformers transfer electrical energy between circuits while
changing voltage levels to allow efficient transmission and distribution.
6. Ferranti effect in transmission lines occurs when:
A. Current increases during faults
B. Receiving-end voltage exceeds sending-end voltage under light load
, C. Frequency decreases during overload
D. Transformer losses increase
B. Receiving-end voltage exceeds sending-end voltage under light load
The Ferranti effect results from line capacitance causing voltage rise at the
receiving end of long transmission lines operating with little or no load.
7. The main purpose of power factor correction is to:
A. Increase reactive power consumption
B. Reduce system efficiency
C. Improve voltage regulation and reduce losses
D. Increase transmission frequency
C. Improve voltage regulation and reduce losses
Power factor correction reduces unnecessary reactive current, improving
efficiency, reducing losses, and improving voltage performance.
8. A lagging power factor in an industrial load is commonly caused by:
A. Capacitor banks
B. Inductive motors
C. Resistive heaters
D. Batteries
B. Inductive motors
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A three-phase power system has a balanced load connected in a star
configuration. If the line voltage is 400 V, what is the phase voltage across
each load impedance?
A. 400 V
B. 346 V
C. 231 V
D. 200 V
B. 346 V
In a balanced star-connected system, the phase voltage is equal to the line
voltage divided by √3. Therefore, 400/√3 ≈ 231 V, making option C correct.
2. In a power system, the main purpose of a circuit breaker is to:
,A. Increase system voltage stability
B. Interrupt fault currents safely
C. Reduce transmission losses
D. Improve generator efficiency
B. Interrupt fault currents safely
Circuit breakers are protective switching devices designed to interrupt
abnormal currents such as short circuits while allowing normal system
operation.
3. The per-unit system in power engineering is mainly used because it:
A. Eliminates the need for transformers
B. Simplifies calculations across different voltage levels
C. Increases generator output power
D. Removes the need for protective relays
B. Simplifies calculations across different voltage levels
The per-unit system normalizes electrical quantities, making calculations
involving different voltage levels and equipment ratings easier and less
error-prone.
4. A synchronous generator operates at 50 Hz and has 20 poles. What is
its synchronous speed?
,A. 150 rpm
B. 300 rpm
C. 600 rpm
D. 1500 rpm
C. 300 rpm
The synchronous speed is calculated using Ns = 120f/P. For 50 Hz and 20
poles, Ns = (120 × 50)/20 = 300 rpm.
5. The primary function of a power transformer in a transmission system
is to:
A. Convert AC power into DC power
B. Increase or decrease voltage levels
C. Generate electrical energy
D. Store electrical energy
B. Increase or decrease voltage levels
Power transformers transfer electrical energy between circuits while
changing voltage levels to allow efficient transmission and distribution.
6. Ferranti effect in transmission lines occurs when:
A. Current increases during faults
B. Receiving-end voltage exceeds sending-end voltage under light load
, C. Frequency decreases during overload
D. Transformer losses increase
B. Receiving-end voltage exceeds sending-end voltage under light load
The Ferranti effect results from line capacitance causing voltage rise at the
receiving end of long transmission lines operating with little or no load.
7. The main purpose of power factor correction is to:
A. Increase reactive power consumption
B. Reduce system efficiency
C. Improve voltage regulation and reduce losses
D. Increase transmission frequency
C. Improve voltage regulation and reduce losses
Power factor correction reduces unnecessary reactive current, improving
efficiency, reducing losses, and improving voltage performance.
8. A lagging power factor in an industrial load is commonly caused by:
A. Capacitor banks
B. Inductive motors
C. Resistive heaters
D. Batteries
B. Inductive motors
