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IFCS http://www.ge.com/indsys/pm/
Time-overcurrent Relays with Voltage Control

GE Protective Relays
DESCRIPTION The undervoltage unit in the Type IFCS
The Type IFCS relays include an relay should be supplied with phase-to-
induction disc time overcurrent unit with phase voltage preferably from the generator
wound shading coils controlled by the potential transformers . The induction disc
contact of an undervoltage unit. This unit is typically set to pick up on fault cur-
overcurrent unit is similar to the rents below maximum load current and is
IFC51(inverse) or the IFC53 (very inverse) prevented from operating on normal load
except that the shading rings on the U conditions by the undervoltage unit. It
magnet have been replaced with the wound should be recognized that accidental loss of
shading coils. potential to the Type IFCS relay will cause
the relay to trip if generator load current in
The Type IFCS relays are supplied with secondary amperes is greater then the pick-
two electrically separate contacts. One of up current of the relay. If a second set of
these contacts which operates the target potential transformers is available, an
seal-in unit is on the induction disc unit and additional relay, the Type CFVB voltage
can be used as a trip contact; the second balance relay, can be used to prevent false
contact of the seal-in unit can be used for tripping of the IFCS upon accidental loss of
alarm or remote indication. its ac voltage source.
The voltage-controlled phase overcurrent (Photo 8043487)
Fig. 1. Type IFCS relay (removed from case)
APPLICATON relays, and the inverse time overcurrent
The Type IFCS relays are designed to ground relay if used, should be connected to
provide backup protection at the generator trip a Type HEA hand reset auxiliary relay
against external phase faults which are not that in turn will trip the main and field
cleared by other protective equipment. An breakers, and sound and alarm. Voltage Unit
inverse time-overcurrent relay may be used The burden is at unity power factor and
for ground fault protection. AVAILABLE TAPS is listed below :
Such back-up protection at the generator (Time-overcurrent unit) Rated Volts Maximum Burden Watts
is normally provided by either a voltage- 1/12 amp--1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 4.0, 120 4.70
controlled inverse time overcurrent relay 5.0, 6.0, 7.0, 8.0, 10.0, 12.0,
such as the IFCS, or by a single-step
distance relay with definite time delay. The
choice between the two forms of back-up
relaying depends on the type of relays on the
adjacent system with which the back-up
relays must be selective. If the adjacent SELECTION GUIDE (0.2/2.0 amp target and seal-in)
Undervoltage Time
circuits are protected by inverse time Frequency Calibration Overcurrent Model Case Approx Weight
overcurrent relaying, then the voltage Voltage Hertz Range Unit Range Number Size Ib (kg)
controlled time-overcurrent relay Type IFCS (Volts) (Amps) Net Ship
can be used. Models are available with INVERSE CHARACTERISTIC
either in-verse or very inverse time
characteristics to coordinate with relays of 120 60 70-100 1/12 12IFCS51AD1A C1 8 14
like characteristic on the adjacent system. 120 50 70-100 1/12 12IFCS51AD2A C1 8 14

But if the adjacent circuits are protected by

high-speed pilot or step distance relaying, VERY INVERSE CHARACTERISTIC
then distance-type relays must be used for 120 50/60 70-100 1/12 12IFCS53AD1A C1 8 14
the back-up function with the definite time
delay provided by an auxiliary timer.
Three single-phase Type IFCS relays are
required to provide phase fault back-up
protection. The Current source for the relays
should be current transformers at the
neutral ends of the generator windings REFERENCES:
when such CT's are available. With these Dimensions . . . . . . . . . . . . . . . . Section 16
connections the relays will, in addition to How to Order . . . . . . . . . . . . . . Section 1
external fault back-up protection, provide Instruction Books . . . . . . . . . . . Section 17
generator fault back-up protection even if Target and Contact Data . . . . . . Section 16
the generator breaker is open or there is no Relay Standards . . . . . . . . . . . . Section 16
other source of generation on the system.

Generator Protection Relays

Page 10-6 Data subject to change without notice
 IFCS
Time-overcurrent Relays with Voltage Control

GE Protective Relays
BURDENS
Time-overcurrent Unit
Burdens at Min. Burdens in Ohms
Model Hz Range Min Pickup Min. Tap (Z) Times Pickup
Tap (Ohms)
Amps R Jx Z 3 10 20
1FCS51 60 1.09 4.41 4.55 2.46 1.00 0.77
1FCS53 60 1-12 1.0 0.35 1.18 1.23 1.21 0.82 0.51
1FCS51 50 0.91 3.68 3.79 1.80 0.83 0.64
1FCS53 50 0.29 0.98 1.03 1.01 0.68 0.43
NOTE : The impedance values given are those for minimum tap, the on the 1.0 ampere tap. The impedance of the 4.0 amp tap is
impedance for other taps at pickup current (tap rating) varies (1.0/4.0)2 x 1.23 = 0. 77 ohms.
inversely (approximately) as the square of the tap rating. For
example, an IFCS53 60 hertz relay has an impedance of 1.23
ohms

Fig. 2. Time-current curve for instantaneous

unit

Fig. 3. External connection for relay Type IFCS

with generator (275A3812)

Fig. 4. Operating time curves for the IFCS

(165A7560) for voltage unit.

Fig. 5. Internal connection diagram

(269A3197) for IFCS relay.

Generator Protection Relays

Data subject to change without notice Page 10-7