ANSI CODE FOR ELECTRICAL EQUIPMENT

ANSI numbers for electrical circuit:

2	Time delay switching (or) closing
3	Checking (or) interlocking
7	Rate of change
21	Distance relay
24	Volt per hertz relay
27	Under voltage
30	Annunciation relay
32	Directional power relay
37	Under current (or) under power relay
40	Field over/under excitation relay
44	Unit sequence starting relay
46	Reverse phase (or) phase balance current relay
47	Phase sequence or phase balance voltage relay
48	Incomplete sequence relay
49	Mechanical or trans thermal relay
50	Instantaneous over current relay
51	Ac  inverse time over current relay
53	Exciter or dc gen relay
55	Power factor relay
56	Field  app relay
58	Rectification failure relay
59	Over voltage relay
60	Voltage or current unbalance relay
62	Time delay stopping or opening relay
64	Ground detector relay
67	AC direction over current relay
68	Blocking or out of step relay
74	Alarm relay
76	DC over current relay
78	Phase angle measuring relay
79	AC reclosing relay
81	Frequency relay
82	DC reclosing relay
83	Automatic selective control or transfer relay
85	Communication or pilot wire relay
86	Lockout relay (Master trip relay)
87	Differential protection relay
87L	Line differential relay
87T	Transformer differential relay
87G	Generator differential relay
91	Voltage direction relay
92	Volt & power direction relay
94	Tripping & trip frequency relay
1	Master element
2	Time delay starting or closing relay
3	Checking or interlocking relay
4	Master contactor
5	Stopping contactor
6	Starting circuit breaker
7	Rate of change relay
8	Control power distribution device
9	Reversing device
10	Unit sequence switch
11	Multifunction device
12	Over speed device
13	Sync-speed device
14	Under speed device
15	Speed or frequency matching device
16	Data communication device
17	Shunting or discharge switch
18	Accelerating or de-accelerating device
19	Starting to running
20	Electrically operated valve
29	Isolating contactor or switch
22	Equalizer circuit breaker
23	Temperature control device
25	Synchronizing check device
26	Apparatus thermal device
28	Flame detector
31	Separate excitation device
33	Position switch
34	Master sequence device
35	Brush operating or slip ring –sc device
36	Polarity or polarizing voltage device
38	Bearing protective device
39	Mechanical condition monitor
41	Field circuit breaker
42	Running circuit breaker
43	Manual transfer or selector device
45	Abnormal atmospheric condition monitor
52	AC circuit breaker
54	Turning gear engaging device
57	Short circuit or grounding device
61	Density switch or sensor
63	Pressure switch
65	Governor
66	Notching or jogging device
69	Permissive control device
70	Rheostat
71	Liquid level switch
72	DC circuit breaker
73	Load resistor contactor
75	Position changing mechanism
77	Telemetering device
80	Flow switch
84	Operating mechanism
89	Line switch
93	Field changing contactor
90	Regulating device
88	Auxiliary motor or motor generator

What is protective relay?

In electrical engineering, a protective relay is a complex electro-mechanical apparatus ( now a days this type of relays are replace by NUMERIC RELAYS), often with more than one coil, designed to calculate operating conditions on an electrical circuit and trip circuit breakers when a fault is detected. Unlike switching type relays with fixed and usually ill-defined operating voltage thresholds and operating times, protective relays have well-established, selectable, time/current (or other operating parameter) curves. Such relays may be elaborate, using arrays of induction disks, shaded-pole magnets, operating and restraint coils, solenoid-type operators, telephone-relay contacts, and phase-shifting networks. Protection relays respond to such conditions as over-current, over-voltage, reverse power flow, over- and under- frequency. Distance relays trip for faults up to a certain distance away from a substation but not beyond that point. An important transmission line or generator unit will have cubicles dedicated to protection, with many individual electro-mechanical devices. The various protective functions available on a given relay are denoted by standard ANSI device numbers. For example, a relay including function 51 would be a timed overcurrent protective relay.

Electromechanical protective relays at a hydroelectric power plant

Design and theory of these protective devices is an important part of the education of an electrical engineer who specializes in power systems. Today these devices are nearly entirely replaced with microprocessor-based digital protective relays (numerical relays) that emulate their electro-mechanical ancestors with great precision and convenience in application. By combining several functions in one case, numerical relays also save capital cost and maintenance cost over electro-mechanical relays. However, due to their very long life span, tens of thousands of these "silent sentinels" are still protecting transmission lines and electrical apparatus all over the world.

Next post we will see the ANSI device numbers. 

substation equipment's part-1

1. Current Transformer (CT)

testing of current transformer

2.Potential Transformer(PT)

3.Isolator

4.Circuit Breaker

5.Surge Arrestor