A disconnector opens a circuit to create a safe, often visible, isolating distance. It may only be operated after its circuit breaker has interrupted the current, apart from small charging and magnetising currents, so interlocks enforce the order breaker first, disconnector second. Opening one on load draws a long arc that can engulf the switch and the operator.
Breaker's open, now open the line disconnector and lock it, then close the earth switch.
British engineers say isolator, North Americans disconnect switch. If a switching order says to open the isolator before the breaker, stop and query it.
Also heard as
- isolator
- disconnect switch
- disconnect
Related terms
Switchgear
Assemblies of breakers, switches, fuses, busbars and enclosures that control and protect power circuits.
Switching order
Written step-by-step sequence of operations used to isolate or restore equipment safely.
Permit to work
Formal written authority to work on equipment that has been isolated, earthed and declared safe.