Overcurrent Protection

1. The nominal rating of an overcurrent protective device should be

• a. Not less than the current

• b. Greater that the current carrying capacity of the conductors

• c. 5 times the load current

• d. Equal to the prospective short-circuit current

An overcurrent protective device must be capable of breaking a circuit

• Before an overload occurs

• After an alarm bell has given a warning

• After the main circuit breaker has tripped out

• Before any over load current could damage the insulation due to the rise in temperature

Which of these is no longer used for new installations:

• RCCB

• RCBO

• RCD

• ELCB

In relation to fuses, what does HRC stand for:

• High Resistive Current

• Heavy Rupturing Current

• Heavy Resistive Current

• High Rupturing Capacity

An RCBO is a device which is used only as:

• A Voltage Reduction Sensor

• An Overload Protection Device

• Overcurrent And Earth Leakage Protection

• A Short Circuit Protection Device

The type of fault which occurs when a phase conductor comes in contact with a neutral conductor is called:

• An Earth Loop Fault

• A Short Circuit Fault

• A Catastrophic Fault

• An Overload Fault

BS 88 fuses are used for protection of motor circuits because they can:

• Discriminate between overload and starting current

• Can withstand high current overloads for a long time

• Will disconnect the circuit quickly if a very small overload occurs

• Is cheaper than other fuses

What does a Residual Current Device (RCD) offer protection against?

• a) An overload current

• b) A short circuit current

• c) The nominal current

• d) An earth fault current

What classification of fuse is re-wirable:

• BS 88

• BS 1362

• BS EN60898

• BS 3036