Almost every major line or equipment in a substation has associated with it a means of completely isolating it from other energized elements as a prudent means of insuring safety by preventing accidental energization. These simple switches, called disconnects, or disconnecting switches, are usually installed on both sides of the equipment or line upon which work is to be done.

They should not be operated while the circuit in which they are connected is energized, but only after the circuit is deenergized. As a further precaution, they may be opened by means of an insulated stick that helps the operator keep a distance from the switch.
Locking devices are sometimes provided to keep the disconnects from being opened accidentally or from being blown open during periods of heavy fault currents passing through them.

Although not designed to be closed to energize the line or equipment with which they are associated, in certain circumstances they may be closed, using special care to close them firmly and rapidly.

Disconnects may be singleblade units or multiple units operated together.

Air break switches have characteristics similar to disconnects, but have the stationary contacts equipped with arc suppressing devices that enable them to be opened while energized, but recognizing a limitation as to the current that may be safely interrupted.