Quiz sheet for fault loop impedance

A circuit consisting of 10A socket outlets protected by a 20A Type C, RCBO requires a maximum permissible fault loop impedance of:

A) There is no specification in the wiring rules for fault loop impedance of outlets protected by an RCD

B) 1 ohm

C) 1.53 ohms

D) 0.5 ohms

ANSWER: A

A fault loop impedance tester is used:

A) to live test the actual impedance of an individual outlet on a circuit.

B) to live test the impedance of a  complete circuits of socket outlets.

C) to dead test the impedance of a  complete circuits of socket outlets.

D) to dead test the impedance of an individual socket outlet.

ANSWER: A

Fault loop impedance includes:

A) The supply impedance plus the impedance of the consumers mains active and neutral plus the impedance of the final sub-circuit active and earth 

B) The supply impedance plus the impedance of the consumers mains active only plus the impedance of the final sub-circuit active and earth 

C) The supply impedance plus the impedance of the consumers mains active and neutral plus the impedance of the final sub-circuit active and neutral.

D) The impedance of the consumers mains active and neutral plus the impedance of the final sub-circuit active and earth.

ANSWER: A

The maximum fault loop impedance of a circuit connected to a 32A Type D circuit breaker would be:

A) 0.58Ω

B) 0.96Ω

C) 0.38Ω

D) No set value

ANSWER: A

The maximum fault loop impedance permissible for a circuit of socket outlets protected by a 20A RCBO (Combination Residual Current Device and Circuit Breaker) is:

A) 1.35 Ω

B) 2.88 Ω

C) 0.98 Ω

D) no set value

ANSWER: D

The purpose of minimising fault loop impedance is to:

A) minimise the trip time for the breaker.

B) prevent the breaker form tripping too fast

C) ensure the conductors are not damaged by fault current

D) maintain equal potential between metallic parts in an earthed situation.

ANSWER: A

To dead test for fault loop impedance, it is acceptable to:

A) measure the resistance of the active and earth loop in the final sub-circuit and compare the result to table 8.2 in your wiring rules.

B) measure the resistance of the active and Neutral loop in the final sub-circuit and compare the result to table 8.2 in your wiring rules.

C) measure the resistance of the active and earth loop in the final sub-circuit and compare the result to table 8.1 in your wiring rules.

D) measure the resistance of the active and neutral loop in the final sub-circuit and compare the result to table 8.1 in your wiring rules.

ANSWER: A


Last modified: Monday, 31 May 2021, 9:05 PM