Different Relay Device Number used in Protection of Power System

MARK NUMBERNAME OF THE DEVICE

2Time delay relay

3Checking or Interlocking relay

21Distance relay

25Check synchronizing relay

27Under voltage relay

30Annunciator relay

32Directional power (Reverse power) relay

37Low forward power relay

40Field failure (loss of excitation) relay

46Negative phase sequence relay

49Machine or Transformer Thermal relay

50Instantaneous Over current relay

51A.C IDMT Over current relay

52Circuit breaker

52aCircuit breaker Auxiliary switch Normally open (a contact)

52bCircuit breaker Auxiliary switch Normally closed (b contact)

55Power Factor relay

56Field Application relay

59Overvoltage relay

60Voltage or current balance relay

64Earth fault relay

67Directional relay

68Locking relay

74Alarm relay

76D.C Over current relay

78Phase angle measuring or out of step relay

79AC Auto reclose relay

80Monitoring loss of DC supply

81Frequency relay

81UUnder frequency relay

81OOver frequency relay

83Automatic selective control or transfer relay

85Carrier or pilot wire receive relay

86Tripping Relay

87Differential relay

87GGenerator differential relay

87GTOverall differential relay

87UUAT differential relay

87NTRestricted earth fault relay

95Trip circuit supervision relay

99Over flux relay

186AAuto reclose lockout relay

186BAuto reclose lockout relay