Inspection and Testing 317E

GN3 gives the maximum stable value of Ze for a TT installation as:

• 1660 ohms.

• 600 ohms.

• 200 ohms.

• 100 ohms.

Which type of earthing system relies on a separately supplied earth, usually the sheathing on the cable:

• TT.

• TN-C-S.

• IT.

• TN-S.

Which of the following would not be one of the human senses to use during the initial verification of an addition to a lighting circuit:

• sight.

• hearing.

• taste.

• touch.

During initial verification of a TN system the installation earth conductor was recorded as 16mm2. The minimum size of main bonding conductor should be: BS7671 CH54

• 4mm2.

• 6mm2.

• 10mm2.

• 16mm2.

Which of the following is not permitted for use as an earth electrode: BS7671 CH54

• Underground structural metalwork.

• Metal water mains pipes.

• Lead sheaths of cables.

• Earth plates.

Which one of the following does not need to be checked for compliance during the visual inspection of an installation:

• presence of fire barriers.

• correct connection of the supply authority's fuse.

• routing of cables in safe zones.

• connection of single pole devices in line conductors only.

The maximum disconnection time allowed for a TN system, not exceeding 32A, with a nominal voltage of 230V a.c. to earth is:

• a 0.2 seconds.

• b 0.4 seconds.

• c 1 second.

• d 5 seconds.

An earth fault loop impedance test Zs performed on a ring circuit would record:

• a The resistance of the protective conductor.

• b The resistance of the protective conductor and the line conductor.

• c The external loop impedance.

• d The resistance of the line conductor, the resistance of the cpc and the external loop.

During an external loop impedance test, the main earthing conductor should be:

• a Connected.

• b Disconnected.

• c Short circuited.

• d Insulated.

The prospective short-circuit current between line and neutral is measured at 850 A. The maximum balanced prospective short-circuit current level between lines on a three phase system, as a rule of thumb, can be assumed to be approximately:

• a 0.85 kA.

• b 1.7 kA.

• c 8.5 kA.

• d 17 kA.