18th Edition Part 4 Mock 2

Where the transfer of supply to an alternative supply is to take place in a TN system, a multi-pole switch must be used which switches the line and neutral conductors, this method prevents?

• a)       Electromagnetic fields due to stray currents in the main supply system
• b)       The earth-fault loop impedance exceeding maximum values
• c)        The prospective fault current tripping the main protective circuit breaker
• d)       The rated residual current tripping any RCD devices

Simultaneously accessible exposed-conductive parts shall be connected to the same earthing system?

• a)       Independent of each system
• b)       Individually, in groups or collectively
• c)        Not at all
• d)       Through a high resistance impedance

What is the minimum impulse voltage for 120 V Category II equipment?

• a)             1.5 kV
• b)          2.5 kV
• c)             4.0 kV
• d)            6.0kV

The external influence code CA2 refers to?

• a)        Where a building is subject to ground tremors
• b)        Where a building is mainly constructed of combustible material e.g. wood
• c)        Where a building is subjected to heavy water waves
• d)        Where a building is subjected to extreme ultra-violet radiation

In an IT system that does not have a neutral conductor it is permitted to omit a device to provide overload protection if?

• a)        The DNO supply fuse will provide this protection
• b)       The IT earth-impedance is sufficiently high enough
• c)         Harmonic currents will not be present
• d)        An RCD is installed in each circuit

A BS 88-2 fuse is to be fitted to a TN circuit with a Zs value of 2.4 Q and requiring a disconnection time of 0.4s What is the maximum rated fuse that couId be used?

• a)             25 A
• b)          32 A
• c)             16 A
• d)             20 A

A temperature cut-out device shall have only?

• a)        A manual reset
• b)       An automatic reset
• c)        A re-settable reset
• d)       A master reset

New to the 18th edition wiring regulation is a requirement with regards to luminaires in domestic premises which requires additional protection to final circuits by means of?

• a)     Ceiling roses to BS:67 which must be SELV
• b)     Conduit for cables to prevent nails and screws damaging cables
• c)      30 mA RCDs
• d)      100 mA RCDs

A veterinary surgery uses an IT system with an a.c. supply. If RA is the sum of the resistances of the earth electrode and the protective conductor connecting it to the exposed conductive-parts (in ohms) and Id is the rated residual operating current, then RA x Id must not exceed?

• a)              25 V
• b)         50 V
• c)         110 V
• d)             120 V

In locations where BE2 conditions exist, and where cables are bunched or installed in long vertical runs, the risk to the cables is?

• a)       From sagging due to the weight of the cables
• b)        From flame propagation
• c)        From large overcurrent
• d)       From short circuits