ANSI DEVICE NUMBER
1 Master Element
26 Apparatus Thermal Device
2 Time delay Starting or Closing Relay
27 Undervoltage Relay
3 Checking or Interlocking Relay
27s- DC under voltage Relay
4 Master Contactor
28 Flame detector
5 Stopping
29 Isolating Contactor or Switch
6 Starting Circuit Breaker
30 Annunciator Relay
7 Rate of Change Relay
31 Separate Excitation
8 Control Power Disconnecting Device
32 Directional Power Relay or Reverse
Power Relay
9 Reversing Device
33 Position Switch
10 Unit Sequence Switch
34 Master Sequence Device
11 Multi-function Device
12 Overspeed Device
35 Brush-Operating or Slip-Ring ShortCircuiting Device
13 Synchronous-speed Device
36 Polarity or Polarizing Voltage Devices
14 Underspeed Device
37 Undercurrent or Underpower Relay
15 Speed or Frequency, Matching Device
38 Bearing Protective Device
16 Data Communications Device
39 Mechanical Condition Monitor
17 Shunting or Discharge Switch
40 Field (over/under excitation) Relay
18 Accelerating or Decelerating Device
41 Field Circuit Breaker
19 Starting to Running Transition Contractor
42 Running Circuit Breaker
20 Electrically Operated Valve
43 Manual Transfer or Selector Device
21 Distance Relay
44 Unit Sequence Starting Relay
22 Equalizer Circuit Breaker
45 DC over voltage Relay
23 Temperature Control Device
46 Reverse-phase or Phase-Balance Current
Relay
24 Volts Per Hertz Relay
25 Synchronizing or Synchronize-Check
Device
47 Phase-Sequence or Phase-Balance Voltage
Relay
48 Incomplete Sequence Relay
49 Machine or Transformer, Thermal RelayOLR
64S - Stator earth fault
65 Governor
50 Instantaneous Overcurrent Relay
66 Notching or Jogging Device
50G - Instantaneous Earth Over Current Relay
(Neutral CT Method)
50N - Instantaneous Earth Over Current Relay
(Residual Method)
50BF - Breaker failure
51 AC Inverse Time Overcurrent Relay
51G- AC Inverse Time Earth Overcurrent
Relay (Neutral CT Method)
51N- AC Inverse Time Earth Overcurrent
Relay (Residual Method)
52 AC Circuit Breaker
52a- AC Circuit Breaker Position (Contact
Open when Breaker Open)
67 AC Directional Overcurrent Relay
68 Blocking Relay
69 Permissive Control Device
70 Rheostat
71 Liquid Level Switch
72 DC Circuit Breaker
73 Load-Resistor Contactor
74 Alarm Relay
75 Position Changing Mechanism
76 DC Overcurrent Relay
52b- AC Circuit Breaker Position (Contact
Closed when Breaker Open)
77 Telemetering Device
53 Exciter or DC Generator Relay
78 Phase-Angle Measuring Relay or "Out-ofStep" Relay
54 Turning Gear Engaging Device
55 Power Factor Relay
56 Field Application Relay
57 Short-Circuiting or Grounding Device
58 Rectification Failure Relay
59 Overvoltage Relay
60 Voltage or Current Balance Relay
79 AC Reclosing Relay (Auto Reclosing)
80 Flow Switch
81 Frequency Relay
82 DC Reclosing Relay
83 Automatic Selective Control or Transfer
Relay
84 Operating Mechanism
61 Density Switch or Sensor
85 Communications,Carrier or Pilot-Wire
Relay
62 Time-Delay Stopping or Opening Relay
86 Lockout Relay/Master Trip
63 Pressure Switch
87 Differential Protective Relay
64 Ground Detector Relay
88 Auxiliary Motor or Motor Generator
64R - Restricted earth fault
89 Line Switch
90 Regulating Device
DME Disturbance Monitor Equipment
91 Voltage Directional Relay
ENV Environmental Data
92 Voltage and Power Directional Relay
HIZ High Impedance Fault Detector
93 Field Changing Contactor
HMI Human Machine Interface
94 Tripping or Trip-Free Relay( trip circuit
supervision Relay)
HST Historian
LGC Scheme Logic
95 For specific applications where other
numbers are not suitable
MET Substation Metering
96 Busbar Trip Lockout relay
PDC Phasor Data Concentrator
97 For specific applications where other
numbers are not suitable
PMU Phasor Measurement Unit
98 For specific applications where other
numbers are not suitable
PQM Power Quality Monitor
RIO Remote Input/Output Device
99 For specific applications where other
numbers are not suitable
RTU Remote Terminal Unit/Data
Concentrator
150 Earth Fault Indicator
SER Sequence of Events Recorder
AFD Arc Flash Detector
TCM Trip Circuit Monitor
CLK Clock or Timing Source
LRSS - LOCAL/REMOTE SELECTOR
SWITCH
DDR Dynamic Disturbance Recorder
DFR Digital Fault Recorder
SOTF - Switch On To Fault
