ANSI Standards

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Abbreviation:

ANSI stands for American National Standards Institute

What is ANSI?

In the design of electrical power systems, the ANSI standard device numbers show the parts of a protective device like a relay or circuit breaker. These kinds of devices protect electrical systems and parts from damage, when something unexpected happens like an electrical fault.

One physical device may correspond to one function number, like “29 Isolating Contactor,” or a single physical device may have many function numbers associated with it, like a numerical protective relay. Letters can be added to the end or beginning of the name of a device to give more information about its purpose and function.

An electrical power system is designed using the ANSI standard device numbers (as per ANSI/IEEE standard C37.2). If there is an issue with the electrical grid, these devices will prevent damage. Below is a list of ANSI device numbers and their corresponding abbreviations:

SL. NO ANSI STANDARD ABBREVIATION ANSI STANDARD DEVICE NUMBER
1Master Element1
2Time-delay Starting / Closing relay2
3Checking / Interlocking Relay3
4Master Protection4
5Stopping Device / Emergency Stop Switch5
6Starting Circuit Breaker6
7Rate of Change Relay7
8Control Power Disconnecting Device8
9Reversing Device9
10Unit Sequence Switch10
11Multifunction Device11
12Overspeed Device12
13Synchronous Speed Device13
14Under-speed Device14
15Speed / Frequency Matching Device15
16Data Communications Device16
17Shunting / Discharge Switch17
18Accelerating / Deaccelerating Device18
19Starting to Running Transition Contactor19
20Electrically-Operated Valve (Solenoid Valve)20
21Distance-Relay21
22Ground-Distance21G
23Phase-Distance21P
24Equalizer Circuit Breaker22
25Temperature control device or Heater23
26Volts per (hertz) relay24
27Synchronizing / synchronism-check device25
28Apparatus thermal device or Temperature Switch26
29Undervoltage Relay27
30Phase Undervoltage27P
31DC undervoltage Relay27S
32Third Harmonic Neutral Undervoltage27TN
33100% (Stator) Earth Fault27TN/59N
34Auxiliary Under-voltage27X
35Under-voltage Auxiliary Input27 AUX
36Bus/Line Under-voltage27/27X
37Accidental Generator Energization27/50
38Flame Detector28
39Isolating Contactor29
40Annunciator Relay30
41Separate Excitation Device31
42Directional Power Relay32
43Low Forward Power32L
44High Directional Power32H
45Watt-metric Zero-Sequence Directional32N
46Directional Power32P
47Reverse Power32R
48Position Switch33
49Master Sequence Device34
50Brush-Operating / Slip-ring Short Circuiting Device35
51Polarity / Polarizing Voltage Device36
52Undercurrent / Underpower Relay37
53Under-power37P
54Bearing Protective Device / Bearing Rtd38
55Mechanical Condition Monitor (Vibration)39
56Field Relay / Loss of Excitation40
57Field Circuit Breaker41
58Running Circuit Breaker42
59Manual Transfer / Selector Device43
60Unit Sequence Starting Relay44
61Fire Detector45
62Reverse-Phase (or) Phase Balance Current Relay (or) Stator Current Unbalance46
63Phase-Sequence (or) Phase Balance Voltage Relay47
64Incomplete Sequence Relay / Blocked Rotor48
65Machine or Transformer Thermal Relay / Thermal Overload49
66RTD Biased Thermal Overload49RTD
67Instantaneous Overcurrent Relay50
68Breaker Failure50BF
69Current Disturbance Detector50DD
70End Fault Protection50EF
71Ground Instantaneous Overcurrent50G
72Isolated Ground Instantaneous Overcurrent50IG
73Acceleration Time50LR
74Neutral Instantaneous Overcurrent50N
75Neutral Instantaneous Breaker Failure50NBF
76Phase Instantaneous Overcurrent50P
77Sensitive Ground Instantaneous Overcurrent50SG
78Split -Phase Instantaneous Current50SP
79Negative Sequence Instantaneous Overcurrent50Q
80Accidental Energization50/27
81Instantaneous / Time-delay Overcurrent Relay50/51
82Ct Trouble50/74
83Instantaneous Differential50/87
84AC (Alternating Current) Time Overcurrent Relay51
85Ground Time Overcurrent51G
86AC (Alternating Current)  inverse time overcurrent (locked rotor) protection relay51LR
87Neutral Time Overcurrent51N
88Phase Time Overcurrent51P
89Locked / Stalled Rotor51R
90Voltage Restrained Time Overcurrent51V
91Negative Sequence Time Overcurrent51Q
92AC circuit breaker52
93AC circuit breaker position (contact open when circuit breaker open)52a
94AC circuit breaker position (contact closed when circuit breaker open)52b
95Exciter (or) Dc Generator Relay53
96Turning Gear Engaging Device54
97Power Factor Relay55
98Field Application Relay56
99Short-Circuiting (or) Grounding Device57
100Rectification Failure Relay58
101Overvoltage Relay59
102Bank Phase Overvoltage59B
103Phase Overvoltage59P
104Neutral Overvoltage59N
105Neutral Voltage Unbalance59NU
106Auxiliary Overvoltage59X
107Negative Sequence Overvoltage59Q
108Voltage (or) Current Balance Relay60
109Neutral Current Unbalance60N
110Phase Current Unbalance60P
111Density Switch (or) Sensor61
112Time-Delay Stopping (or) Opening Relay62
113Pressure Switch Detector63
114Ground Protective Relay64
115Field Ground Protection64F
116Rotor earth fault64R
117Restricted earth fault differential64REF
118Stator earth fault64S
119Sub-harmonic Stator Ground Protection64S
120100% Stator Ground64TN
121Governor65
122Notching or Jogging Device / Maximum Starting Rate / Starts Per Hour / Time Between Starts66
123AC Directional Overcurrent Relay67
124Ground Directional Overcurrent67G
125Neutral Directional Overcurrent67N
126Earth fault directional67Ns
127Phase Directional Overcurrent67P
128Sensitive Ground Directional Overcurrent67SG
129Negative Sequence Directional Overcurrent67Q
130Blocking Relay / Power Swing Blocking68
131Permissive Control Device69
132Rheostat70
133Liquid Switch and Level Switch71
134DC Circuit Breaker72
135Load-Resistor Contactor73
136Alarm Relay74
137Position Changing Mechanism75
138DC Overcurrent Relay76
139Telemetering Device; Speed Sensor77
140Phase Angle Measuring (or) Out-of-Step Protective Relay78
141Loss of Mains78V
142AC Reclosing Relay / Auto Reclose79
143Liquid or Gas Flow Relay80
144Frequency Relay81
145Over Frequency81O
146Rate-of-Change Frequency81R
147Under Frequency81U
148DC Reclosing Relay82
149Automatic Selective Control (or) Transfer Relay83
150Operating Mechanism84
151Pilot Communications, Carrier (or) Pilot-Wire Relay85
152Lock-Out Relay; Master Trip Relay86
153Differential Protective Relay87
154Bus Differential87B
155Generator Differential87G
156Generator / Transformer Differential87GT
157Segregated Line Current Differential87L
158Ground Line Current Differential87LG
159Motor Differential87M
160Overall Differential87O
161Phase Comparison87PC
162Restricted Ground Fault87RGF
163Stator Differential87S
164Percent Differential87S
165Transformer Differential87T
166Voltage Differential87V
167Auxiliary Motor (or) Motor Generator88
168Line Switch89
169Regulating Device90
170Voltage Directional Relay91
171Voltage & Power Directional Relay92
172Field-Changing Contactor93
173Tripping (or) Trip-Free Relay94
174For specific applications where other numbers are not suitable95
175Transmitter96
176For specific applications where other numbers are not suitable97
177For specific applications where other numbers are not suitable98
178For specific applications where other numbers are not suitable99