1)Isolators (or disconnector switches) are not equipped with are quenching devices and, therefore, not used to open circuits carrying current
2)As the name implies, isolator isolates one portion of the circuit from another and is not intended to be opened while current is flowing Isolators must not be opened until the circuit is interrupted by some other means.
It can isolator is opened carelessly, when carrying a heavy current, the resulting are could easily cause a flash over to earth.
3)This may shatter the supporting insulator and may even cause a fatal accident to the operator, particularly in high voltage circuits.
4)While closing a circuit, the isolator is closed first, then circuit breaker Isolators are necessary on supply side of circuit breakers in order to ensure isolation (disconnection) of the circuit breaker from the live parts for the purpose of maintenance.
