DISTANCE PROTECTION ENGINEERING ACTUAL EXAM
AND PRACTICE TESTS NEWEST 2026/2027 EXAM WITH
COMPLETE QUESTIONS AND CORRECT DETAILED
ANSWERS| BRAND NEW VERSION!
1. What is the primary quantity measured by a distance relay to determine
whether a transmission-line fault is within its protection zone?
A. Apparent power
B. Impedance
C. Frequency
D. Power factor
Answer: B. Impedance
Rationale: A distance relay calculates the apparent impedance Z=V/IZ=V/I seen
from the relay location. The measured impedance is compared with predefined
zone characteristics to determine fault location.
2. For a solid three-phase fault on a transmission line, the impedance measured
by a distance relay is primarily:
A. Zero regardless of relay location
B. Equal to the source impedance
C. Proportional to the line impedance between the relay and fault
D. Equal to the load impedance
Answer: C. Proportional to the line impedance between the relay and fault
Rationale: For a three-phase fault, the relay measures the positive-sequence
impedance between its location and the fault, making the measured impedance
proportional to the electrical distance to the fault.
3. Which distance-relay characteristic is inherently directional?
,A. Reactance characteristic
B. Mho characteristic
C. Resistance-only characteristic
D. Thermal characteristic
Answer: B. Mho characteristic
Rationale: The mho characteristic is inherently directional because its impedance-
plane circle passes through the origin.
4. On an R-X impedance plane, the resistance is represented on the:
A. Vertical axis
B. Horizontal axis
C. Time axis
D. Current axis
Answer: B. Horizontal axis
Rationale: Distance-relay characteristics are commonly plotted on an R-X plane,
with resistance RR on the horizontal axis and reactance XX on the vertical axis.
5. Which relay characteristic provides better resistance coverage for high-
resistance faults?
A. Mho only
B. Reactance
C. Undervoltage
D. Overfrequency
Answer: B. Reactance
Rationale: A reactance characteristic can provide substantial resistive fault
coverage because its operating region is largely independent of resistance.
6. What is the main purpose of Zone 1 in a conventional distance-protection
scheme?
,A. Protect the entire interconnected network
B. Provide instantaneous protection for most of the protected line
C. Provide backup protection for adjacent lines only
D. Detect generator out-of-step conditions
Answer: B. Provide instantaneous protection for most of the protected line
Rationale: Zone 1 is normally set to cover approximately 80–90% of the protected
line and operates without intentional time delay.
7. Why is Zone 1 normally set below 100% of the protected transmission line?
A. To reduce CT saturation
B. To prevent overreach into the remote bus and adjacent line
C. To increase loadability
D. To eliminate the need for communication
Answer: B. To prevent overreach into the remote bus and adjacent line
Rationale: Setting Zone 1 below the full line impedance provides security against
measurement errors and system conditions that could otherwise cause undesired
operation beyond the protected line.
8. A typical Zone 2 distance element is generally:
A. Set to cover only 20% of the protected line
B. Set to cover the protected line plus part of the next line
C. Always instantaneous
D. Used only for generator protection
Answer: B. Set to cover the protected line plus part of the next line
Rationale: Zone 2 commonly provides time-delayed backup for the protected line
and extends into the adjacent line or remote-bus area.
9. Zone 3 is primarily intended to provide:
, A. Local measurement redundancy only
B. Remote backup protection
C. Transformer differential protection
D. Busbar differential protection
Answer: B. Remote backup protection
Rationale: Zone 3 is generally a time-delayed backup element that can reach
beyond the remote bus to provide backup for faults on adjacent transmission
elements.
10. Which equation represents apparent impedance measured by a distance
relay?
A. Z=VIZ=VI
B. Z=V/IZ=V/I
C. Z=I/VZ=I/V
D. Z=V+IZ=V+I
Answer: B. Z=V/IZ=V/I
Rationale: The relay determines apparent impedance from the measured voltage
divided by the appropriate fault current.
11. What is the principal purpose of a distance relay's polarizing voltage?
A. Increase CT burden
B. Provide a reference for determining fault direction
C. Reduce system frequency
D. Measure active power directly
Answer: B. Provide a reference for determining fault direction
Rationale: Polarizing quantities provide a stable voltage reference against which
the fault voltage/current relationship can be evaluated for directional
discrimination.
AND PRACTICE TESTS NEWEST 2026/2027 EXAM WITH
COMPLETE QUESTIONS AND CORRECT DETAILED
ANSWERS| BRAND NEW VERSION!
1. What is the primary quantity measured by a distance relay to determine
whether a transmission-line fault is within its protection zone?
A. Apparent power
B. Impedance
C. Frequency
D. Power factor
Answer: B. Impedance
Rationale: A distance relay calculates the apparent impedance Z=V/IZ=V/I seen
from the relay location. The measured impedance is compared with predefined
zone characteristics to determine fault location.
2. For a solid three-phase fault on a transmission line, the impedance measured
by a distance relay is primarily:
A. Zero regardless of relay location
B. Equal to the source impedance
C. Proportional to the line impedance between the relay and fault
D. Equal to the load impedance
Answer: C. Proportional to the line impedance between the relay and fault
Rationale: For a three-phase fault, the relay measures the positive-sequence
impedance between its location and the fault, making the measured impedance
proportional to the electrical distance to the fault.
3. Which distance-relay characteristic is inherently directional?
,A. Reactance characteristic
B. Mho characteristic
C. Resistance-only characteristic
D. Thermal characteristic
Answer: B. Mho characteristic
Rationale: The mho characteristic is inherently directional because its impedance-
plane circle passes through the origin.
4. On an R-X impedance plane, the resistance is represented on the:
A. Vertical axis
B. Horizontal axis
C. Time axis
D. Current axis
Answer: B. Horizontal axis
Rationale: Distance-relay characteristics are commonly plotted on an R-X plane,
with resistance RR on the horizontal axis and reactance XX on the vertical axis.
5. Which relay characteristic provides better resistance coverage for high-
resistance faults?
A. Mho only
B. Reactance
C. Undervoltage
D. Overfrequency
Answer: B. Reactance
Rationale: A reactance characteristic can provide substantial resistive fault
coverage because its operating region is largely independent of resistance.
6. What is the main purpose of Zone 1 in a conventional distance-protection
scheme?
,A. Protect the entire interconnected network
B. Provide instantaneous protection for most of the protected line
C. Provide backup protection for adjacent lines only
D. Detect generator out-of-step conditions
Answer: B. Provide instantaneous protection for most of the protected line
Rationale: Zone 1 is normally set to cover approximately 80–90% of the protected
line and operates without intentional time delay.
7. Why is Zone 1 normally set below 100% of the protected transmission line?
A. To reduce CT saturation
B. To prevent overreach into the remote bus and adjacent line
C. To increase loadability
D. To eliminate the need for communication
Answer: B. To prevent overreach into the remote bus and adjacent line
Rationale: Setting Zone 1 below the full line impedance provides security against
measurement errors and system conditions that could otherwise cause undesired
operation beyond the protected line.
8. A typical Zone 2 distance element is generally:
A. Set to cover only 20% of the protected line
B. Set to cover the protected line plus part of the next line
C. Always instantaneous
D. Used only for generator protection
Answer: B. Set to cover the protected line plus part of the next line
Rationale: Zone 2 commonly provides time-delayed backup for the protected line
and extends into the adjacent line or remote-bus area.
9. Zone 3 is primarily intended to provide:
, A. Local measurement redundancy only
B. Remote backup protection
C. Transformer differential protection
D. Busbar differential protection
Answer: B. Remote backup protection
Rationale: Zone 3 is generally a time-delayed backup element that can reach
beyond the remote bus to provide backup for faults on adjacent transmission
elements.
10. Which equation represents apparent impedance measured by a distance
relay?
A. Z=VIZ=VI
B. Z=V/IZ=V/I
C. Z=I/VZ=I/V
D. Z=V+IZ=V+I
Answer: B. Z=V/IZ=V/I
Rationale: The relay determines apparent impedance from the measured voltage
divided by the appropriate fault current.
11. What is the principal purpose of a distance relay's polarizing voltage?
A. Increase CT burden
B. Provide a reference for determining fault direction
C. Reduce system frequency
D. Measure active power directly
Answer: B. Provide a reference for determining fault direction
Rationale: Polarizing quantities provide a stable voltage reference against which
the fault voltage/current relationship can be evaluated for directional
discrimination.
