Protective relay

Protective relay

Protective relay are "automatic devices which can sense the fault and send instruction to the associated circuit breaker to open" .

every part of the power system is prvided with a protective relaying system and an associated switching device.

all equipment associated with the fault clearing process are covered by the term "switchgear".

in addition to circuit breaker and protective relays, the associated equipment for controling, regulating and measuring can also be considered as switchgear devices.

switchgear includes switches,fuses,circuit breaker,isolator,relays,control panels,lighting arresters,current transformer, and various associated equipments.

switchgear is an essential part of a power system and also that of any electric circuit 

switchgear are also necessary at every switching point in the power system.

since, between the generation station and final load points, there are several voltage levels and fault levels hence, in various application, the requirements of a switchgear vary according to : 

1- location

2- rating, and

3- local requirements