GE Industrial Solutions ProTrip Conversion Kits LA-600, LA-800, and LA-1600 - Manual (Page 13)

13
SECTION 6. TESTING AND TROUBLE-
SHOOTING
WARNING: Do not change taps on the current
sensors or adjust the trip unit settings while the
breaker is carrying current. Failure to adhere to
these instructions will void all warranties.
Testing
Before installing a converted breaker back into
service, perform the following steps:
1. Verify that the trip unit is securely installed by
performing a continuity test on the CT wiring
and the trip unit.
a. Disconnect the black CT wires at each phase
sensor.
b. Check for continuity with a continuity tester
or VOM from the white lead of the phase A
CT to the white lead of the phase B CT.
c. Repeat this continuity test for the white leads
of the phase A and phase C CTs.
d. Measure the resistance across each phase
sensor and compare the values measured to
the values listed in Table 1.
e. Reconnect the black CT leads to all of the
phase sensors. Ensure that this is done
before continuing with performance testing
of the breaker.
CAUTION: In addition to the continuity test
described in Step 1 and before performance test-
ing of the converted breaker, each phase of the
breaker should be primary injected with a current
level of about 10%, but no more than 20%, of the
CT rating.
WARNING: If the converted breaker is energized or
tested by primary injection with a sufficiently high
test current with a loose or open circuit between
the CTs and the trip unit, damage will occur to the
trip unit, wire harness, 50-pin trip unit connector,
and CTs. Failure to adhere to these instructions
will void all warranties.
2. Check the insulation on the prim ary circuit with
a 1,000-volt Megger.
3. Measure the resistance across the line and load
terminals for each phase using a micro-ohmme-
ter or millivolt tester. If the resistance differs
considerably from phase to phase, the electrical
connections may not be properly tightened or it
could also indicate improper contact wipe.
4. To verify that the breaker has been properly
retro fitted, perform a primary injection test on
each phase. This test will check the CTs, bus,
wiring harness, flux shifter, and trip unit as a
complete system.
a. A high-current, low-voltage power supply
should be connected across each line and
load terminal to simulate an overcurrent fault.
b. Set the long-time trip at 0.5 to minimize the
breaker stress.
c. When ground fault is installe d, the test can be
performed by wiring two adjacent poles in
series or by using the GE Digital Test Kit, cat.
no. TVRMS2. This will prevent the breaker
from tripping because of an unbalanced cur-
rent flow.
CAUTION: Do not attempt to use GE Test Kit cat.
no. TVTS1 or TVRMS on this trip unit.
Trouble-Shooting
When malfunctioning is suspected, first examine
the breaker and its power system for abnormal
conditions such as the following:
• The breaker is not tripping in response to over-
current conditions or incipient ground faults.
• The breaker is remaining in a trip-free state
because of mechanical interference along its
trip shaft.
• The shunt trip (if present) is activating improp-
erly.
Nuisance Tripping on Ground Fault-Equipped
Breakers
When nuisance tripping occurs on breakers
equipped with ground fault trip, a probable cause is
the existence of a false ground signal. Each phase
sensor is con nected to summing circuitry in the trip
unit. Under no-fault conditions on three-wire load
circuits, the cur rents add to zero and no ground
signal is developed. This current sum is zero only if
all three sensors have the same electrical charac-
teristics. If one sensor differs from the others (such
as by a different rating or wrong tap setting), the
circuitry can produce an output suffi cient to trip the
breaker. Similarly, a discontinuity between any
sensor and the trip unit can cause a false trip signal.
The sensors and their connections should be
closely examined if nuisance tripping is
encountered on any breaker whose ProTrip trip unit
has previously demonstrated satisfactory
performance. After dis connecting the breaker from
all power sources, per form the follow ing procedure:
1. Check that all phase sensors are the same type
(current range).
2. Verify that the tap settings on all three phase
sensors are identical.