IEEE device numbers

Supervisory control and indication.

A similar series of numbers, prefixed by the letters RE (for “remote”) shall be used for the interposing relays performing functions that are controlled directly from the supervisory

system. Typical examples of such device functions are: RE1, RE5 and RE94.


Note: The user of the “RE” prefix for this purpose in place of the former 200 series of numbers now makes it possible to obtain increased flexibility of the device function numbering system. For example, in pipeline pump stations, the numbers 1 through 99

are applied to device functions that are associated with the over-all station

operation. A similar series of numbers,

starting with 101 instead of 1, are used for those device functions that are associated with unit 1; a similar series starting with 201 for device functions that are associated with unit

2; and so on, for each unit in these installations.


Devices performing more than one function

If one device performs two relatively important functions in an equipment so that it is

desirable to identify both of these functions, this may be done by using a double function

number and name such as:

50/51 Instantaneous and Time Over current



Suffix numbers

If two or more devices with the same function number and suffix letter (if used) are present

in the same equipment, they may be distinguished by numbered suffixes as for example,

52X-1, 52X-2 and 52X-3, when necessary.


Suffix letters

Suffix letters are used with device function numbers for various purposes. In order to prevent

possible conflict each suffix letter should have only one meaning in an individual equipment. All other words should use the abbreviations as contained in American Standard Z32.13-1950, or latest revision thereof, or should use some other distinctive abbreviation, or be written out in full each time they are used.

The meaning of each single suffix letter, or combination of letters, should be clearly designated in the legend on the drawings or publications applying to the equipment. In cases where the same suffix (consisting of one letter or a combination of letters) has different meanings in the same equipment, depending upon the device function number with which is used, then the complete device function number with which it is used, the complete device function number with its suffix letter or letters and its corresponding function name should be listed in the legend in each case, as follows: 90V, Voltage regulator. Lower case (small) suffix letters are used in practically all instances on electrical diagrams for the auxiliary, position, and limit switches. Capital letters are generally used for all other suffix letters.

The letters should generally form part of the device function designation, are usually written

directly after the device function number, as for example, 52CS, 71W, or 49D. When it

is necessary to use two types of suffix letters in connection with one function number, it is

often desirable for clarity to separate them by a slanted line or dash, as for example,

20D/CS or 20D-CS. The suffix letters which denote parts of the main device, and those which cannot or need not form part of the device function designation, are generally written directly below the device function number on drawings, as for example, or .

52/CC or 43/A


Auxiliary devices Separate auxiliary devices Actuating quantities

These letters indicate the condition or electrical quantity to which the device responds, or the medium in which it is located, such as:


Main devices

These letters denote the location of the main device in the circuit, or the type of circuit in

which the device is used or the type of circuit or apparatus with which it is associated, when

this is necessary, such as:


Y – Auxiliary relay 1)


R – Raising relay

L – Lowering relay

O – Opening relay or contactor

C – Closing relay or contactor

CS – Control switch

CL – Auxiliary relay, open (energized when main device is in open position)

OP – Auxiliary relay, open (energized when main device is in open position)

U – “Up” position-switch relay

D – “Down” position-switch relay

PB – Push button

1) In the control of a circuit breaker with so-called

X-Y relay control scheme, the X relay is the device whose main contacts are used to energize

the closing coil or the device which in some other manner, such as by the release of stored energy, causes the breaker to close.

The contacts of the Y relay provide the antipump feature for the circuit breaker.

A – Air or Amperes or Alternating

C – Current

D – Direct or Discharge

E – Electrolyte

F – Frequency, or Flow, or Fault

H – Explosive

J – Differential

L – Level, or Liquid

P – Power, or Pressure

PF – Power factor

Q – Oil

S – Speed, or Suction, or Smoke

T – Temperature

V – Voltage, Volts, or Vacuum

VAR – Reactive power

VB – Vibration

W – Water, or Watts

A – Alarm or Auxiliary power

AN – Anode

B – Battery, or Blower, or Bus

BK – Brake

BL – Block (Valve)

BP – Bypass

BT – Bus tie

C – Capacitor, or Condenser, or Compensator, or Carrier current, or Case, or Compressor

CA – Cathode

CH – Check (Valve)

D – Discharge (Valve)

E – Exciter

F – Feeder, or Field, or Filament, or Filter, or Fan

G – Generator, or Ground2)

H – Heater, or Housing

L – Line, or Logic

M – Motor, or Metering

N – Network, or Neutral 2)

P – Pump, or Phase comparison

R – Reactor, or Rectifier, or Room

S – Synchronizing, or Secondary, or

Strainer, or Sump, or Suction (Valve)

T – Transformer, or Thyratron

TH – Transformer (high-voltage side)

TL – Transformer (low-voltage side)

TM – Telemeter

U – Unit

2) Suffix “N” is generally used in preference to “G” for devices connected in the secondary neutral of current transformers, or in the secondary of a current transformer whose primary winding is located in the neutral of a machine or power transformer, except in the case of transmission line relaying, where the suffix “G” is more commonly used for those relays which operate on ground faults.


Main device parts

These letters denote parts of the main device, divided in the two following categories:


1. All parts, except auxiliary contacts, position switches, limit switches, and torque limit



2. All auxiliary contacts and positioning and limit switches

 for such devices and equipment as circuit breakers, contactors, valves and rheostats

and contacts of relays. These are designated as follows:


Standard reference positions of some typical devices are as follows:

BK – Brake

C – Coil, or Condenser, or Capacitor

CC – Closing coil

HC – Holding coil

M – Operating motor

MF – Fly-ball motor

ML – Load-limit motor

MS – Speed adjusting, or Synchronizing


S – Solenoid

SI – Seal-in

TC – Trip coil

V – Valve

a – Contact that is open when the main device is in the standard reference position, commonly referred to as the nonoperated or reenergized position and that closes when the device assumes the opposite position.

b – Contact that is closed when the main device is in the standard reference position, commonly referred to as the nonoperated or deenergized position, and that opens when the device assumes the opposite position.

aa – Contact that is open when the operating mechanism of the main device is in the

nonoperated position and that closes when the operating mechanism assumes the opposite position.

bb – Contact that is closed when the operating mechanism of the main device is in

the nonoperated position and that opens when the operating mechanism assumes the opposite position.


Device Standard reference position

Power circuit breaker Main contacts open

Disconnecting switch Main contacts open

Load-break switch Main contacts open

Valve Closed position

Gate Closed position

Clutch Disengaged position

Turning gear Disengaged position

Power electrodes Maximum gap position

Rheostat Maximum resistance


Adjusting means 1) Low or Down position

Relay 2) Deenergized position

Contactor 2) Deenergized position

Relay (latched-in type)

Non-latched-in position

Contactor (latched-in type)

Main contacts open

Temperature relay 3) Lowest temperature

Level detector 3) Lowest level

Flow detector 3) Lowest flow

Speed switch 3) Lowest speed

Vibration detector 3) Minimum vibration

Pressure switch 3) Lowest pressure

Vacuum switch 3) Lowest pressure, i.e.,

highest vacuum

The simple designation “a” or “b” is used in all cases where there is no need to adjust the

contacts to change position at any particular point in the travel of the main device or where the part of the travel where the contacts change position is of no significance in the control or operating scheme. Hence the “a” and “b” designations usually are sufficient for circuit breaker auxiliary switches.

Note: If several similar auxiliary switches are present on the same device, they should be designated numerically 1, 2, 3, etc. when necessary.


Other switches

These letters cover all other distinguishing

features or characteristics or conditions,

which serve to describe the use of the device

or its contacts in the equipment such as:


Device Standard reference position

1) These may be speed, voltage, current, load, or similar adjusting devices comprising rheostats, springs, levers, or other components for the purpose.


2) These electrically operated devices are of the non-latched-in type, whose contact position is dependent only upon the degree of energization of the operating or restraining or holding

coil or coils which may or may not be suitable for continuous energization. The deenergized

position of the device is that with all coils deenergized.


3) The energizing influences for these devices are considered to be, respectively, rising

temperature, rising level, increasing flow, rising speed, increasing vibration, and increasing



A – Accelerating, or Automatic

B – Blocking, or Back-up

C – Close, or Cold

D – Decelerating, or Detonate, or Down, or


E – Emergency, or Engaged

F – Failure, or Forward

H – Hot, or High

HR – Hand reset

HS – High speed

L – Left, or Local, or Low, or Lower, or


M – Manual

OFF – Off

ON – On

P – Polarizing

R – Right, or Raise, or Reclosing, or Receiving, or Remote, or Reverse

S – Sending, or Swing

T – Test, or Trip, or Trailing

TDC – Time-delay closing

TDO – Time-delay opening


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