20
Electrically controlled valve
25
Synchronizing relay
27
Under voltage relay
32
Directional power relay
40
Field relay
41
Field circuit breaker
47
Phase rotation
50
Instantaneous overcurrent
51
Time overcurrent relay
52
Circuit breaker
55
Power factor relay
59
Over voltage relay
64
Ground protective relay
65
Governor
67
AC directional overcurrent relay
69
Permissive control device
79
Reclosing relay
81
Frequency relay
86
Locking out relay
87
Differential protective relay