What is an electrical isolator?

Something that doesn't let electricity through

An isolator (UK terminology) or disconnector (US terminology) is a switch used to isolate a section of a circuit from any energised conductors, by presenting a visible break in the circuit. Isolators are not designed to break load currents (unless fitted with optional arc-breaking feature) or to break fault currents. In high-voltage systems, isolators are used in conjunction with circuit breakers -with the isolators opened after a circuit breaker has opened the circuit, and closed before the circuit breaker closes the circuit. For example, before one can perform maintenance work on, say, a high-voltage circuit breaker, the following sequence must be followed:

1. the circuit breaker is opened, breaking the circuit.
2. isolators located on either side of the circuit breaker are opened, presenting a visible break between the isolator and energised lines.
3. temporary earth (ground) connections are applied to each side of the circuit breaker.
4. barriers and warning signs are erected around the circuit breaker to define the permitted work area.
5. a permit to work card, listing the work to be performed, and any potential hazards, is issued to the personnel who are to maintain the circuit breaker.