Bus Entrances (Be); Basic Equipment Selection; Optional Indication Selection; Induction Motor Feeders (Imf) - GE SecoGear Application Manual

SecoGear Medium-voltage Switchgear Application and Technical Guide
SecoGear Switchgear Applications

BUS ENTRANCES (BE)

Bus entrance equipment, also referred to as a cable tap, is a
metal-clad vertical section in which one of the
compartments contains incoming or outgoing conductors
connecting directly to the main bus without the use of a
circuit breaker. Conductors can be either cables or non-seg
bus duct.

Basic Equipment Selection

Select this type of equipment as a means to connect either
incoming or outgoing conductors directly to the bus for
circuits that require no circuit breakers. See "SECTION 1" and
Figure 5-6 for configuration restrictions when selecting bus
entrances.

INDUCTION MOTOR FEEDERS (IMF)

Induction motor feeders are used to control and protect full-
voltage-start motors and are designated as "branch circuit"
protective equipment. Economics usually preclude
protecting a motor smaller than 1500 HP (IMF1) with a
device package as complete as one used for larger motors
(IMF2).
The equipment is specified for use on impedance grounded
or solidly grounded systems. See "Optional Equipment
Selection (for IMFE, IMF1, IMF2)" for modifications of this
equipment for use on systems with other types of
grounding. Also see IEEE C37.96-2000 IEEE Guide for AC
Motor Protection for relaying recommendations.
46

Optional Indication Selection

• Instrumentation and Metering: For circuits requiring
indication or metering of electrical quantities, add three
current transformers or two voltage transformers. If you
cannot locate both a set of CTs and VTs in a bus
entrance, select instrumentation and metering required
as necessary.
• Test Blocks: For circuits requiring provisions for insertion
of portable recording meters or other similar devices, add
current and voltage test blocks. A basic current block is
wired to maintain the circuit when the test plug is
removed.

Figure 5-6: Bus Entrance

Protective Scheme Selection

• IMF1: Basic equipment for IMF1 includes three-phase
running overload, locked rotor, and short-circuit
protection (49/50); undervoltage protection with time
delay (27, 62 – only one per lineup required); zero-
sequence ground-fault protection (50GS); and load
current indication. The overcurrent relays operate from
three CTs, one in each phase, and a ground-sensor CT.
Complete economical motor protection packages are
available in GE Multilin 339 digital motor protection
relays. For undervoltage protection when using Multilin
339, add a separate GE Multilin MIV undervoltage relay.
When using Multilin 339, specify the optional MPM
module, or add a separate MIV relay as noted above.
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