Are the following statements true or false. Give a reason for each
a)The principle of operation of a three-phase and single-phase core balance Earth leakage relays is similar
b)Only the live conductors of three-phase four-wire system must be broken by the Earth leakage relays when it operates
c) in a three-phase installation, the Earth leakage relays will trip if the load is not properly balanced
d) a three-phase Earth leakage relays does not have test circuit
a) False. The principle of operation of a three-phase and single-phase core balance Earth leakage relays is different. Three-phase relays detect the imbalance in the current between all three phases, while single-phase relays detect the imbalance in a single phase.
b) False. In a three-phase four-wire system, the neutral conductor must also be broken by the Earth leakage relays when it operates to ensure the safety of the system.
c) False. Earth leakage relays in a three-phase installation do not trip solely based on load imbalance. They trip when there is a leakage current to earth, which can be caused by faults or insulation breakdown.
d) False. Three-phase Earth leakage relays typically have a test circuit to allow for routine testing of the relay's operation and sensitivity. Testing the relay regularly is important to ensure it will function correctly during an actual fault situation.