Optional Equipment Selection (For Imfe, Imf1, Imf2); Protection; Indication; Control - GE SecoGear Application Manual

DET-882
• IMF2: Basic equipment for IMF2 is GE Multilin 869 digital
motor protection relay, which includes (26/50/83) for
locked rotor and short-circuit protection;
overtemperature (49); undervoltage with time delay (27,
62); 3-phase self-balancing machine differential (87M);
one Type GE Series 95 lockout relay (86M); zero-sequence
ground fault (50GS); and full function metering. Additional
protective functions are available in the 869. Multilin relay
869 operates from three current transformers, one in
each phase, a ground sensor CT, and three current
transformers located at the motor.
• IMFE: Metal-clad feeder equipment (IMFE) is used for
controlling and protecting full-voltage-start, essential
service motors and is designated as motor "branch
circuit" protective equipment. Such motor feeders sound
an alarm only for motor overload, but trip the circuit
breaker for locked rotor and short-circuit conditions.
Basic equipment for IMFE includes a GE Multilin 339
digital motor protection relay, which provides three-
phase overload indication, locked-rotor tripping, short-
circuit tripping (49/50/83), zero-sequence ground-fault
protection, and load current indication. No undervoltage
protection is included. Multilin relay 339 operates from
three current transformers, one in each phase, and a
ground sensor CT.

Optional Equipment Selection (for IMFE, IMF1, IMF2)

Protection

For ungrounded systems, omit the ground-sensor
overcurrent relay and the current transformer. When
equipment is used to feed more than one motor from the
same bus, only one GE Multilin MIV undervoltage relay is
required. However, for multiple motors, add auxiliary relays
(27X), with sufficient contacts to trip each additional motor
feeder breaker.
For both smaller and larger motors (greater than 1500 HP),
complete protection including motor differential can be
obtained by using the GE Multilin 869 relay (with motor
mounted CTs). The CTs located at the motor and used for the
motor differential (87M) circuit are typically furnished by the
motor manufacturer. They are not supplied with the
switchgear.
For lineups with bus differential protection, add three current
transformers. For motors with RTDs, the GE Multilin 869, 369,
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SecoGear Medium-voltage Switchgear Application and Technical Guide
and 339 digital motor protection relays offer RTD sensing
inputs.

Indication

• Instrumentation and Metering: For circuits requiring the
indication or metering of additional electrical quantities,
and using Multilin 369 or 869 relays. For circuits without
metering built into the multifunction protective relay, add
a GE PQM II power quality meter, which includes
indication of all three phases of current, in addition to
Volts, Watts, Vars, PF, and demand functions.
• Test Blocks: For circuits that require the provisions for
insertion of portable recording meters or other similar
devices, add current and voltage test blocks. Basic
current test blocks are wired to maintain the circuit when
the test plug is removed.
• Indicating Lamp: For circuits requiring a circuit breaker
disagreement or spring-charged indication function, add
a white indicating lamp.

Control

• Remote Control; For circuit breakers controlled from a
remote location, choose the remote control scheme from
those listed in Table 4-1. From this table, Scheme C is
recommended, since it provides maximum operating
flexibility. It requires the use of a breaker control switch to
provide the permissive function. With Scheme C, remote
close and trip is possible only with the breaker in the
"connected" position; local close with the breaker in the
"test" position; and local trip with the breaker in the
"connected" or "test" position.
In addition, remote control for motors requires a lockout
relay (86) in order to prevent breakers' closing (after a
relay-initiated trip) until the lockout device is manually
reset. (The 86 device specified on IMF2 may be used for
both 87M and remote control.)

Location of Optional Devices

If several optional devices are added to motor feeder
equipment, there may not be sufficient space to mount them
all. In this case, specify that the excess relays are to be
mounted on an adjacent auxiliary compartment. This makes
the vertical section a custom section.
SecoGear Switchgear Applications
47