Power System Protection and Switchgear Quiz 1

Relay contacts are normally made up of: _______.

• Silver

• Copper

• Aluminum

• Lead

Impedance relays can be used for:

• Phase faults

• Earth faults

• Both A&B

• None of the above

The most efficient torque-producing actuating structure for induction type relays is:

• Shaded pole structure

• Watt-hour meter structure

• Induction cup structure

• Single induction cup structure

Thermal relays are used for the protection of motors against over-current owing to:

• Short circuit

• Heavy loads

• Earth fault

• None of these

The relay used for the feeder protection is:

• Under-voltage relay

• Translay relay

• Thermal relay

• Buchholz relay

The values of fault current depend on

• Voltage

• Total impedance

• both (A) and (B)

• None of the above

A relay used for protection of motors against overload is

• Impedance relay

• Electromagnetic relay

• Thermal relay

• Buchholz's relay

The over-voltage surges in power systems may be caused by

• Lightning

• Switching

• Resonance

• Any of the above

The protection against over-voltage due to lightening is provided by

• surge diverters

• Low tower footing resistance

• Use of overhead ground wires

• Any of the above

Over-voltage transients may occur due to

• Lightning

• Switching

• Arcing grounds

• Any of the abov