There are three main types of protective relays: electromechanical, static, and digital. Electromechanical relays include the plunger type, clapper type, and electromagnetic induction disc type. Protective relays are used for over current protection and have definite tripping characteristics, with potential drawbacks that digital and static relays aim to address.

1.  PROTECTIVE RELAYS:
1. electromechanical relays.
2. static relays (semiconductor).
3. digital relays.
electromechanical protective relays:
1- The plunger type
2- The clapper type
3- The electromagnetic induction disc

8. 1- The plunger type

12. 2- The clapper type

18. The electromagnetic induction disc

20. 3
-
‫التغذية‬ ‫مصدر‬ ‫قوة‬
:
-
Strong sourse

21.  Weak source

40.  Over Current Protection
(Instantaneous Over Current Relay)

41.  Tripping Characteristics of Multi-Stage Definite
Time Over Current Relay

42. 
‫عيوبه‬
:

44.  Definite Time Over Current Relay with Internal
Timer