ANSI table

1 Main element 50 Instantaneous Overcurrent Relay

2 Start/stop timed function 51 Timed Overcurrent Relay
3 Interlocking or verification function 52 Alternating current circuit breaker
4 Main contactor 53 Relay for exciter or DC generator
5 Interrupt device Circuit breaker for direct current, high
54
6 Starting circuit breaker speed
7 Anode circuit breaker 55 Power Factor Relay
Power disconnection device of 56 Field application relay
8
control 57 Grounding or short-circuit device
9 Reversal device 58 Rectification failure relay
10 Sequence key of the units 59 Overvoltage Relay
11 Reserved for future application 60 Voltage balance relay/fuse burning
12 Overspeed device 61 Current Balance Relay
13 Synchronous rotation device 62 Timer Relay
14 Under-speed device 63 Gas pressure relay (Buchholz)
Adjustment or comparison device of 64 Ground protection relay
15
speed or frequency 65 Regulator
16 Reserved for future application 66 Supervision relay of the number of starts
17 Derivation or discharge key 67 Directional Overcurrent Relay
18 Acceleration or deceleration device 68 Power oscillation blocking relay
19 Transition starter-contactor 69 Permissive control device
20 Electrically operated valve 70 Electrically operated rheostat
21 Distance relay 71 Level detection device
22 Equalizing circuit breaker 72 Direct current circuit breaker
23 Temperature control device 73 Load resistance contactor
24 Overexcitation relay or Volts per Hertz 74 Alarm function
Synchronization checking relay or 75 Mechanism of Position Change
25
Synchronization 76 DC Overcurrent Relay
26 Thermal device of the equipment 77 Impulse transmitter
27 Under-voltage Relay Phase angle measurement relay / protection
28 Reserved for future application 78
against lack of synchronization
29 Isolation contactor 79 Reclosing Relay
30 Annunciator Relay 80 Reserved for future application
31 Excitation device 81 Under/Over frequency relay
32 Power directional relay 82 DC Reclosure Relay
33 Positioning Key 83 Automatic transfer/select relay
34 Motor-operated sequence key 84 Operation mechanism
Device for operating the brushes or 85 Telecommunications signal receiver relay
35
short-circuit collector rings 86 Auxiliary Blocking Relay
36 Polarity device 87 Differential protection relay
37 Undercurrent or underpower relay 88 Auxiliary motor or generator motor
38 Bearing protection device 89 Disconnect switch
39 Reserved for future application 90 Regulation device
40 Excitation Loss Relay 91 Voltage Directional Relay
41 Circuit breaker or field switch 92 Voltage and Power Directional Relay
42 Circuit breaker/ normal operation switch 93 Field Variation Contactor
43 Manual transfer device 94 Shutdown Relay
44 Starting sequence relay 95 to
45 Reserved for future application Used for specific applications
99
46 Phase current unbalance relay
47 Voltage Phase Sequence Relay
48 Incomplete sequence relay/ long start
49 Thermal relay
 COMPLEMENTATION OF THE ANSI TABLE:

50 N - instantaneous neutral overcurrent

51N - time-delayed neutral overcurrent (defined time or inverse curves)
50G - instantaneous ground overcurrent (commonly known as 50GS)
51G - time-delayed earth overcurrent (commonly referred to as 51GS and with time
defined or inverse curves
50BF - circuit breaker failure protection relay (also called 50/62 BF)
51Q - time-delay negative sequence overcurrent relay with defined time or
inverse curves
51V - overcurrent relay with voltage restriction
51C - overcurrent relay with torque control
59Q - negative sequence overvoltage relay
59N - residual overvoltage relay or neutral overvoltage (also called 64G)
64 - ground protection relay can be by current or by voltage. The diagrams
single wires must indicate whether this element is powered by TC or by TP, so that it
can define correctly.
If powered by TC, it can also be used as a unit 51 or 61.
If powered by TP, you can use a unit 59N or 64G.
The 64 function can also be found as housing protection, mass-bowl or
tank, being applied in power transformers up to 5 MVA.
67 N - neutral directional overcurrent relay (instantaneous or timed)
67 G - directional earth overcurrent relay (instantaneous or time delayed)
67Q - directional overcurrent relay for negative sequence
Differential Protection - ANSI 87
The differential relay 87 can be of various types:
87 T - transformer differential (can have 2 or 3 windings)
87G - generator differential;
87GT - differential protection of the generator-transformer group
87 B - differential of bars. It can be of high, medium, or low impedance.
One can find overcurrent elements connected in industrial circuits.
differential scheme, where the phase current transformers are summed and connected to the relay
overcurrent.
There is also a logical selectivity scheme to perform the differential function.
of bars.
87M - engine differential - In this case, it can be of the percentage type or of the type
self-balanced.
The percentage uses a differential circuit through 3 phase CTs and 3 CTs in the neutral.
do motor.
The autobalanced type uses a set of 3 TC's at the motor terminals, connected to
way to obtain the summation of the currents of each phase and neutral. In reality, it is about
a current overcurrent element, where the scheme is differential and not the relay.