Historical information

Protective relays are one of the critical components of the elctrical power grid that serve to detect defective equipment or other dangerous or intolerable conditions and can either initiate or permit switching or simply provide an alarm to provide an alarm to provide a safer, more reliable delivery system. Used in power stations.
The function of relay is to quickly remove from service any equipment that might suffer damage or otherwise affect the operation of the system. Relays protect the electrical system in 2 ways: Prevent failure or damage to electrical systems. Mitigate the effects of failure when it occurs.
Switches that control other switches.
Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal.

Significance

Used by the State Electricity Commission of Victoria for the Kiewa Hydro Electric Scheme in the power stations. Manually operated by remote control for an external circuit breaker.
The relays were from a Kiewa Hydro Power Station control panel.

Physical description

Collection of black metal rectangular boxes (heavy) containing electrical wires forming a circuit. The longer, narrower rectangles have a bakelite knob at one end. Some of the boxes have one side of clear perspex and another has all sides of clear perspex. One is labelled "group relay". Another has windows with labels eg. 'turbine overspeed' 'emergency trip' and one has 3 steel knobs. - with 'stop', 'start'. One box is larger than the rest and has clear perspex side showing 'overcurrent relay' and workings.

Inscriptions & markings

One has a plaque attached.
Manufacture: "The English Co. Ltd. London