Relay ANSI Codes

Relay’s Nomenclature as per ANSI:

No	Type of Relay
2	Time delay relay
3	3 Checking or Interlocking relay
21	21 Distance relay
25	Check synchronizing relay
27	Under voltage relay
30	Annunciation relay
32	Directional power (Reverse power) relay
37	Low forward power relay
40	Field failure (loss of excitation)
46	Negative phase sequence relay
49	Machine or Transformer Thermal relay
50	Instantaneous Over current relay
51	A.C. IDMT Over current relay
52	Circuit breaker
52a	Circuit breaker Auxiliary switch “Normally open” (‘a ‘contact)
52b	Circuit breaker Auxiliary switch “Normally closed” (‘b’contact)
55	Power Factor relay
56	Field Application relay
59	Overvoltage relay
64	Earth fault relay
67	Directional relay
68	Locking relay
74	Alarm relay
76	D.C Over current relay
78	Phase angle measuring or out of step relay
79	AC Auto reclose relay
80	Monitoring loss of DC supply
81	Frequency relay
81 U	Under frequency relay
81 O	Over frequency relay
83	Automatic selective control or transfer relay
85	Carrier or pilot wire receive relay
86	Tripping Relay
87	Differential relay
87G	Generator differential relay
87G	T Overall differential relay
87U	UAT differential relay
87NT	Restricted earth fault relay
95	Trip circuit supervision relay
99	Over flux relay
186A	Auto reclose lockout relay
186B	Auto reclose lockout relay