GE
The class 1 model GFM Ground Fault protection systems are designed to minimize damage
Model GFM - 353, 363,453,
Grid Solutions
Model GFM
Ground Fault Current Detection Systems
Model GFM Relay (For Use with GFM sensors only)
Adjustable Operating Range
Trip currents from 2.0 to 65 Amperes
Time delay from instantaneous to 36 cycles
Ambient Temperature Range
-30 °C to +60 °C.
Operation
Input Power
Self powered.
Frequency
50/60 Hz.
or loss to equipment caused by destructive arcing ground faults. This GFM systems is
designed for all polyphase applications and is ideally suited for motor control, motor
control centers, and medium voltage starters. System can be wye or delta, ground or
resistance grounded. When the ground fault current exceeds a pre-selected condition
(current and time setting) the relay trips.
The relay contacts can be connected in the control circuit of a motor starter, to the shunt
trip of a circuit breaker or similar disconnecting or alarm devices. The system has an
inverse time characteristic to prevent nuisance tripping. The relay tripping current value is
field adjustable over the trip current range of the sensor. The adjustable trip time delay
relay is field selectable up to 36 cycles.
Positive condition indication
Normal (Reset) - Green (“ON”)
Tripped - Red (“OFF”)
Manual Reset
Model GFM - 252
& Model 262
REGULATORY AGENCY APPROVALS
U
L
110395
and 463
LR80793
GFM Ground Fault Current Detection Systems
configuration of the power conductors. The Ground Fault Sensor will
Model GFM Sensors (For Use with GFM relays only)
2.0 to 65 Amp Trip Currents
Toroidal, Rectangluar, & 3 Hole Sensors
Frequency
50/60 Hz
Insulation Level
600 Volt, 10 kV BIL
Terminals
Terminals are brass studs No. 8-32.
Type GFM Ground Fault Current Sensors are available in three
different case styles and a variety of sizes and trip current ranges to
match the GFM Relay. The physical size of the sensor window
should be carefully determined by the physical size and
respond only to ground faults which occur between the position of
the senor and the load.
CAUTION:
Proper safety precautions must be followed during installation by a trained
electrician. It is recommended that the incoming power be de-energized before
installation. The sensor must have its secondary terminals short circuited or
the relay connected before energizing the primary circuit.
GFM Toroidal Sensors
Toroidal Sensors
*Dual trip current ranges 3.5 to 11 and 10 to 36
** Mounting bracket kits are available for all toroidal sensors except the Model GFM 094, GFM 125,
and GFM 156, which have molded mounting feet
2
GFM Ground Fault Current Detection Systems
GFM 3-Hole Sensors GFM Rectangular Sensors
Rectangular Sensors
* Model GFM 080 X 117SC is split core (take-apart style) for assembly to existing
electrical installations without the need for dismantling the primary bus or cables.
3-Hole Sensors (1-Core)
* The Model GFM 3P205 X 050 has a rectangle window 2.05 ” X 0.50”.
** UL Listed Only - No CSA Approval
3
Pick-Up and Time Delay Characteristics
GFM-353, GFM-453 relays do not have adjustable trip time delay, while the
GE GFM sensors are assigned a current range to indicate a pick-up
current level.
The GFM relay has a range select from “A” to “D”. “A” is the lowest current
magnitude pick-up and “D” is the highest . The pick up level is dependent
on the energy in a ground fault wave shape; therefore tripping initiation
depends on the wave shape and regularity of the fault current .
In general, the relay will pick up before 150 % of the low end of the sensor
current range on the “A” setting with a sinusoidal signal, and will pick up
before 150 % of the high end of the sensor range on the “D” setting. The
relay is adjustable continuously from “A” to “D” so that identical sensors
can be coordinated.
GFM ground fault system has inverse time current trip characteristics. As
the fault current increases, the trip time delay gets shorter. The GFM-252,
GFM-262, GFM-363, GFM-463 relays have adjustable trip time delay.
Trip time on Models with fixed time delay, may exceed a one second delay.
Fixed Delay Types - GFM Test Procedure
A Simulated fault current can be applied by the above test circuit.
An appropriate value of R1 should be selected to apply a minimum
of 1.5 times maximum trip rating of the sensor.
Trip time on Models with fixed time delay, may exceed a one second
delay at the pick up threshold. Trip time on Models with adjustable time
delay, may exceed a one second delay at the pick up threshold, however
the inverse time curve can be modified to vary trip time at multiples of
over current with an ordinal “1” to “4” is scale where “1” is faster and “4”
is slower.
The pick up time delay on the fixed time delay relays can be as fast as 0.02
seconds on the “A” setting, and 0.1 seconds on the “D” setting at high fault
currents.
For the adjustable time delay relays, a time delay of “1” in the “A” scale can
produce a time delay of under 0.15 seconds at a 600% sinusoidal fault . A
time delay setting of “4” will result in a time delay approximately 0.2
seconds slower than the “1” setting. Time delay will be greater for smaller
fault current .
Similarly, a time delay setting of “1” in the “D” scale can produce a time
delay of under 0.4 seconds at a 600% sinusoidal fault . A time delay setting
of “4” will result in a time delay approximately 0.2 seconds slower than the
“1” setting. Time delay will be greater for smaller fault current .
1. Assure that the GFM relay is in “ NORMAL ” (reset) position.
2. Close switch S1, and check for reset for response. Relay handle
will move to the tripped position.
3. Open S1, reset the relay and remove the test circuit from the
system. System is now back to normal.
This PROCEDURE should be performed by Qualified Personnel only.
ITI-Model-GFM-Spec-EN-2017-12-Grid-AIS-1134. © Copyright 2017. General Electric Company
and Instrument Transformers LLC reserve the right to change specifications of described
products at any time without notice and without obligation to notify any person of such changes.
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