Question

Which of the following correctly presents the sequence of operations of isolator circuit breaker and earthing switch while closing a circuit?
A) Ensure circuit breaker is closed - close isolator – open earthing switch
B) Ensure circuit breaker is open - close isolator – open earthing switch if any close circuit breaker
C) Ensure circuit breaker is open - open isolator – open earthing switch if any close circuit breaker
D) None of the above

Answer 1

Hint : Isolator circuit breaker and earthing switch play a very important role to ground the residual charge in circuits. This is often done after disconnecting the load from a source or a power supply and while connecting it back.

Complete step by step answer
An isolator is a switch that is designed to break an electric circuit in a case where no load is attached to the system. Breaking of an electrical circuit by the Isolator is more reliable and safer than using a normal circuit breaker. This is because when using a circuit breaker, heavy current can flow through the contacts of the circuit breaker.
While closing a circuit, we first open the earthing switch so that the charge can no longer be flown into the ground. Then we close the isolator when there is no load in the circuit as the isolator can only handle a no-load situation and then finally the circuit breaker is closed so that the current can start flowing in the circuit.
Hence the correct answer will be option (B).

Note
For maintenance or any other purpose of power lines, if we need to open or break the circuit then we should follow a proper sequence for the operations of circuit breakers, isolators, and earthing switches. This is done for the safety of our equipment as well as our safety. A circuit breaker is used to protect the power line when the current exceeds the rated current while an isolator switch is used to physically disconnect any circuit when repairs are being done.