CITY & GUILDS 2365 UNIT 614
PRACTICE EXAM | QUESTIONS AND
ANSWERS |2026/2027 UPDATE | JUST
RELEASED
1. In the adiabatic equation t = (k²S²) / I², what does ‘k’ represent?
A. The fault current in Amperes
B. The time of disconnection in seconds
C. The cross-sectional area of the conductor
D. A factor based on the resistivity and temperature of the conductor
Answer: D
Conceptual Explanation: k is a factor taking into account the resistivity, temperature
coefficient, and heat capacity of the conductor material, as defined in BS 7671.
2. What is the maximum disconnection time for a 32A final circuit supplying a socket outlet in
a TN system?
A. 5 seconds
B. 1 second
C. 0.2 seconds
D. 0.4 seconds
,Answer: D
Conceptual Explanation: According to Table 41.1, for a TN system with Uo=230V, final
circuits not exceeding 63A with socket outlets must disconnect within 0.4 seconds.
3. Which factor must be applied when a cable is surrounded by thermal insulation for a
length of 500mm?
A. 0.725
B. 0.50
C. 0.63
D. 1.00
Answer: B
Conceptual Explanation: Regulation 523.9 states that if a cable is surrounded by thermal
insulation for 500mm or more, a factor of 0.5 must be applied.
4. When performing an earth fault loop impedance test on a 30mA RCD protected circuit, why
is a ‘no-trip’ test used?
A. To test the RCD’s mechanical operation
B. To prevent the RCD from tripping during the test
C. To bypass the RCD completely
D. To increase the fault current
Answer: B
, Conceptual Explanation: A ‘no-trip’ test uses a low current to measure Zs without
reaching the threshold that would cause the RCD to trip.
5. Which of the following describes the ‘selectivity’ of protective devices?
A. The coordination where the downstream device trips before the upstream one
B. The coordination where the upstream device trips before the downstream one
C. The ability of a device to withstand high fault currents
D. The manual selection of a fuse based on its color
Answer: A
Conceptual Explanation: Selectivity ensures that only the protective device closest to the
fault operates, leaving the rest of the installation energized.
6. What is the minimum required insulation resistance for a 400V circuit?
A. 0.5 MΩ
B. 2.0 MΩ
C. 1.0 MΩ
D. 5.0 MΩ
Answer: C
Conceptual Explanation: For circuits above 500V (e.g., 400V nominal), the minimum
insulation resistance value is 1.0 MΩ according to Table 64 of BS 7671.
PRACTICE EXAM | QUESTIONS AND
ANSWERS |2026/2027 UPDATE | JUST
RELEASED
1. In the adiabatic equation t = (k²S²) / I², what does ‘k’ represent?
A. The fault current in Amperes
B. The time of disconnection in seconds
C. The cross-sectional area of the conductor
D. A factor based on the resistivity and temperature of the conductor
Answer: D
Conceptual Explanation: k is a factor taking into account the resistivity, temperature
coefficient, and heat capacity of the conductor material, as defined in BS 7671.
2. What is the maximum disconnection time for a 32A final circuit supplying a socket outlet in
a TN system?
A. 5 seconds
B. 1 second
C. 0.2 seconds
D. 0.4 seconds
,Answer: D
Conceptual Explanation: According to Table 41.1, for a TN system with Uo=230V, final
circuits not exceeding 63A with socket outlets must disconnect within 0.4 seconds.
3. Which factor must be applied when a cable is surrounded by thermal insulation for a
length of 500mm?
A. 0.725
B. 0.50
C. 0.63
D. 1.00
Answer: B
Conceptual Explanation: Regulation 523.9 states that if a cable is surrounded by thermal
insulation for 500mm or more, a factor of 0.5 must be applied.
4. When performing an earth fault loop impedance test on a 30mA RCD protected circuit, why
is a ‘no-trip’ test used?
A. To test the RCD’s mechanical operation
B. To prevent the RCD from tripping during the test
C. To bypass the RCD completely
D. To increase the fault current
Answer: B
, Conceptual Explanation: A ‘no-trip’ test uses a low current to measure Zs without
reaching the threshold that would cause the RCD to trip.
5. Which of the following describes the ‘selectivity’ of protective devices?
A. The coordination where the downstream device trips before the upstream one
B. The coordination where the upstream device trips before the downstream one
C. The ability of a device to withstand high fault currents
D. The manual selection of a fuse based on its color
Answer: A
Conceptual Explanation: Selectivity ensures that only the protective device closest to the
fault operates, leaving the rest of the installation energized.
6. What is the minimum required insulation resistance for a 400V circuit?
A. 0.5 MΩ
B. 2.0 MΩ
C. 1.0 MΩ
D. 5.0 MΩ
Answer: C
Conceptual Explanation: For circuits above 500V (e.g., 400V nominal), the minimum
insulation resistance value is 1.0 MΩ according to Table 64 of BS 7671.
