GE EntelliGuard G - High Set Instantaneous Overcurrent (HSOIC); Making Current Release (MCR); Reduced Energy Let-Through (RELT) Instantaneous Trip

DET-653C EntelliGuard
®
G Circuit Breaker Application Guide
24-May-12 Section 3. EntelliGuard TU Trip Unit System
©2012 General Electric All Rights Reserved
23
High Set Instantaneous Overcurrent (HSIOC)
The EntelliGuard TU trip unit’s HSIOC pickup is similar to the
fixed override used by other trip units and circuit breakers in
the industry. In EntelliGuard G, the HSIOC setting is changed
automatically by the trip unit if the normal adjustable
Instantaneous is turned off (LVPCB only). When adjustable
Instantaneous setting is turned off, HSIOC nominal setting
becomes 98% of the circuit breaker’s Short Time withstand
setting. In all other cases, in the EntelliGuard G family of
circuit breakers, the HSIOC is set high enough to allow full
selectivity up to the circuit breaker’s short time withstand
rating.
For circuit breakers with an HSIOC trip function, the location
of the HSIOC trip is shown by the line that reaches the
0.01sec axis at the bottom of the TCC. The location of that
line is shown in Table 3.11. In many applications, the
EntelliGuard G circuit breaker with an EntelliGuard TU trip
unit will be completely selective up to the HSIOC pickup or
the circuit breaker’s full short circuit rating, even with the
adjustable Instantaneous on.
Making Current Release (MCR)
This form of Instantaneous protection is provided on all
EntelliGuard G circuit breakers. This function provides
protection in case the circuit breaker is closed on an
unusually high current. A circuit breaker that experiences 15
times (15x) or more its plug rating is possibly closing in on a
fault caused by incorrectly wired conductors, forgotten
grounding cables or some other type of unusual low
impedance fault.
Alternatively, it is closing on a very low impedance arcing
fault. In either case, there is a possibility that equipment may
be damaged by the high fault current or an arc flash hazard
has been inadvertently created. The MCR provides very fast
protection when the circuit breaker is closed and for the first
six cycles thereafter. After the six cycles have elapsed, the
MCR is turned off and the circuit breaker reverts to its
adjustable Instantaneous pickup and HSIOC if provided. The
MCR will clear fault current in 40msec or less.
Table 3.13. HSIOC Locations
Short
Circuit Tier
Interrupting Rating (A)
UL489
Override
UL1066
Override
240V
480V
600V
UL489 I
CW
UL1066 I
CW
S
65,000
65,000
50,000
42,000
50,000
42,000
None
N
65,000
65,000
65,000
42,000
65,000
42,000
None
H
85,000
85,000
65,000
50,000
65,000
50,000
65,000
P
100,000
100,000
65,000
50,000
65,000
50,000
65,000
E
85,000
85,000
85,000
N/A
85,000
N/A
None
M
100,000
100,000
100,000
65,000
85,000
65,000
85,000
B
100,000
100,000
100,000
N/A
100,000
N/A
None
L
150,000
150,000
100,000
85,000
100,000
85,000
10,000
• All UL Overrides are -0% tolerance, ANSI Override pickup at -0% or -9% based on Adjustable Selective Instantaneous being on or off.
Reduced Energy Let-Through (RELT) Instantaneous Trip
The EntelliGuard TU trip unit provides an optional second,
user-adjustable, RELT Instantaneous trip, which allows a
circuit breaker to be temporarily set to a more sensitive
pickup to provide better protection, only when better
protection is needed and some selectivity may be
sacrificed. The RELT pickup is adjustable from 1.5X to 15X
of plug rating, independently of the normal adjustable
selective Instantaneous. It may be set higher or lower than
the selective Instantaneous.
The user must make two entries at the trip unit: (1) Pickup
settings (1.5-15X of the plug) and (2) ON, OFF or REMOTE.
ON/OFF enables or disables the pickup setting. REMOTE
allows the RELT Instantaneous pickup to be enabled via
application of 24Vdc or Vac at the RELT input terminals or
serial communications via the Modbus or Profibus
communication port. The RELT pickup may be enabled via
serial communication or remote 24V signal, but both need
to be indicating “OFF” for the RELT Instantaneous pickup
to be disabled. The RELT input command may be wired to
a manual switch, automatic sensor or, via external logic,
to one or more signal sources.
When the EntelliGuard TU trip unit has the RELT
Instantaneous pickup enabled, the trip unit provides a
feedback signal via an optically isolated dry contact and
serial communication. This provides positive feedback that
the trip unit has received and reacted to the RELT Enable
command.
The EntelliGuard TU trip unit’s RELT capability provides the
ultimate in user flexibility for wiring and controlling an
alternate Instantaneous setting for temporary use to reduce
personnel hazard. The RELT Instantaneous pickup clears
fault current in 42msec or less at 60Hz.
RELT capability may be provided on a trip unit with or
without control power. If 24V is provided to the RELT input,
the trip unit will use the RELT Instantaneous trip setting.
However, without control power connected to the trip unit
permanently, indication that the trip unit is in the RELT mode
may not be reliably communicated. If reliable
communication that the trip unit is in the RELT mode is
desired, it is suggested that the trip unit be permanently
connected to 24Vdc control power.