Types of Relay

First Letter - Operation Quantity

A - Phase angle comparison

B - Balanced Current

C - Current (Amps)

D - Differential

E - Direction

F - Frequency

K - Rate of rise of current

M - Manual

O - Oil Pressure

P - Poly phase VA

R - Reactive VA

S - Slip Frequency

T - Temperature

V - Potential

W - Watts

X - Reactance

Y - Admittance (Conductance)

Z - Impedance

Second Letter - Measurement

A - Attracted armature

B - Buchholz

C - Induction

D - Induction Disc

G - Galvanometer

I - Transmitter

J - Mixed Types

M - Magnet (polarized)

P - Plug

R - Rectifier

S - Synchronized Motor

T - Transistor

W - Weight (Gravity)



Third Letter - Application

A - Auxiliary

B - Testing

C - Carrier or Counting

D - Directional

E - Earth/Ground

F - Plug or Alarm Indicator

G - General or Generator

H - Harmonic Restricted

J - Tripping

JE - Tripping (Electrical Reset)

JM - Tripping (Manual Reset)

JS - Tripping (Self)

JC - Tripping (Conductor)

K - Check Alarm

L - Local Limiting

M - Same Phi or motor

N - Negative Sequence

O - Out of Step

P - Potential Failure

R - Re-closing

S - Synchronizing

T - Timer or Transformer

U - Definite Time

V - Voltage Resistant

W - Piolet Wire

WA - Interposing

WS - Inter-tripping

X - Supervisory

Y - Flash Back (Black Fire)

Z - Special Application

Z0 - Zero Sequence

Examples :

CDG - Current (operation), Disc(Measurement), General Purpose(Application)

CAG - Current (operation), Attracted armature(Measurement), General Purpose(Application)

VAJ - Potential (operation), Attracted armature(Measurement), Tripping(Application)

VTT - Potential (operation), Transmitter(Measurement), Transformer(Application)

VAZ - Potential (operation), Attracted armature(Measurement), Special Application

VAA - Potential (operation), Attracted armature(Measurement), Auxiliary (Application)