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In electric power systems and industrial automation, ANSI Device Numbers can be used to identify equipment and devices in a system such as relays, circuit breakers, or instruments. The device numbers are enumerated in ANSI/IEEE Standard C37.2 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations.
Many of these devices protect electrical systems and individual system components from damage when an unwanted event occurs such as an electrical fault. Historically, a single protective function was performed by one or more distinct electromechanical devices, so each device would receive its own number. Today, microprocessor-based relays can perform many protective functions in one device.[1] When one device performs several protective functions, it is typically denoted "11" by the standard as a "Multifunction Device", but ANSI Device Numbers are still used in documentation like single-line diagrams or schematics to indicate which specific functions are performed by that device.
3 - Checking or Interlocking Relay, complete Sequence
4 - Master Protective
5 - Stopping Device, Emergency Stop Switch
6 - Starting Circuit Breaker
7 - Rate of Change Relay
7F - Alternative number for Rate Of Change Of Frequency Relay (ROCOF)
8 - Control Power Disconnecting Device
9 - Reversing Device
10 - Unit Sequence Switch
11 - Multifunction Device
12 - Overspeed Device
13 - Synchronous-Speed Device
14 - Underspeed Device
15 - Speed or Frequency Matching Device
16 - Data Communications Device
17 - Shunting or Discharge Switch
18 - Accelerating or Decelerating Device
19 - Starting-to-Running Transition Contactor
20 - Electrically-Operated Valve (Solenoid Valve)
21 - Distance Relay
21G - Ground Distance
21P - Phase Distance
22 - Equalizer Circuit Breaker
23 - Temperature control device, Heater
24 - Volts per Hertz Relay (in some old analog applications, a 59 and an 81 device would be chained together as a 59/81 to implement the equivalent of V/Hz protection)
25 - Synchronizing or Synchronism-check Device
26 - Apparatus Thermal Device, Temperature Switch
27 - Undervoltage Relay
27P - Phase Undervoltage
27S - DC Undervoltage Relay
27TN - Third Harmonic Neutral Undervoltage
27TN/59N - 100% Stator Earth Fault
27X - Auxiliary Undervoltage
27 AUX - Undervoltage Auxiliary Input
27/27X - Bus/Line Undervoltage
27/50 - Inadvertent Energization
28 - Flame Detector
29 - Isolating Contactor
30 - Annunciator Relay
31 - Separate Excitation Device
32 - Directional Power Relay
32L - Low Forward Power
32H - High Directional Power
32N - Wattmetric Zero-Sequence Directional
32P - Directional Power
32R - Reverse Power
33 - Position Switch
34 - Master Sequence Device
35 - Brush-Operating or Slip-ring Short Circuiting Device
A suffix letter or number may be used with the device number; for example, suffix N is used if the device is connected to a Neutral wire (example: 59N in a relay is used for protection against Neutral Displacement); and suffixes X, Y, Z are used for auxiliary devices. Similarly, the "G" suffix can denote a "ground", hence a "51G" is a time overcurrent ground relay. The "G" suffix can also mean "generator", hence an "87G" is a Generator Differential Protective Relay while an "87T" is a Transformer Differential Protective Relay. "F" can denote "field" on a generator or "fuse", as in the protective fuse for a pickup transformer. Suffix numbers are used to distinguish multiple "same" devices in the same equipment such as 51–1, 51–2.[3]
Device numbers may be combined if the device provides multiple functions, such as the Instantaneous / Time-delay Overcurrent relay denoted as 50/51.[3]
For device 16, the suffix letters further define the device: the first suffix letter is 'S' for serial or 'E' for Ethernet. The subsequent letters are: 'C' security processing function (e.g. VPN, encryption), 'F' firewall or message filter, 'M' network managed function, 'R' rotor, 'S' switch and 'T' telephone component. Thus a managed Ethernet switch would be 16ESM.
^Tengdin, John (1 February 2009). "Knowing the Language: The History and Practice of IEEE C37.2". Electric Light & Power. PennWell Corporation. Archived from the original on 19 October 2017. Retrieved 18 October 2017. It may surprise some to learn that this standard—or more accurately its AIEE predecessor—is one of the oldest IEEE standards in use. It was first published as AIEE No. 26 in 1928 and was used to document the control systems in the then popular automatic railway substations.
^ abApplied Protective Relaying 1979 by Westinghouse Electric Corporation, 2nd Printing, "Appendix II, Electrical Power System Device Numbers and Functions" as adopted by IEEE standard and incorporated in American Standard C37.2-1970.
IEEE Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations', IEEE Std C37.2-2008
