EAL unit 4 revision 3

which earthing system is not recommended for petrol stations, caravans and marina pontoons?

• TNS

• TT

• TNC

• PME

What is the maximum value for Ze, for a TN-C-S system?

• 0.8

• 0.35

• 20

• 1666

which earthing system, due to a high possibility of high Zs values, must have additional protection?

• TNS

• TT

• TNCS

• PME

Which earthing system is frequently used in hospitals?

• TNS

• IT

• TNC

• PME

Which supply system uses a PEN conductor?

• TT

• TNS

• IT

• TNCS

the metalwork that does not form part of an electrical installation, but may be electrified under fault conditions, is called:

• extraneous conductive parts

• basic protection

• exposed conductive parts

• fault protection

which of the following is an extraneous conductive part?

• the metal casing on a washing machine

• metal switch back plate

• metal casing on an electric motor

• metal casing on a gas pipe

A current that goes beyond the rated value in an otherwise healthy circuit is one definition of:

• earthing

• bonding

• overload

• short circuit

the maximum disconnection time for TT systems, above 32A is:

• 5s

• 1s

• .2s

• .4s

A TNS earthing system operates through the:

• earth electrode

• PEN conductor

• supply cable armour

• the earth itself