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6. Monitoring and testing
Power XPert® release triP unit for MagnuM PXr circuit breakers
MN013015EN January 2022 www.eaton.com
Figure 21. PXPM secondary injection test.
Secondary injection and simulated current can be configured
for trip or no-trip. Complete testing of the trip unit system
can be accomplished when a current sensor test is used in
conjunction with secondary injection test.
Testing prior to startup should always be done with the
circuit breaker either in a de-energized system, or in TEST or
DISCONNECTED cassette position, or WITHDRAWN from
cell. The system will prevent a test if more than 5% of I
n
is
measured in the breaker phases.
ote:
N
Because time-current settings are based on desired
system coordination and protection schemes,
the protection settings, if altered during any
test sequence, should be reset to their as-found
conditions.
6.4.1 Secondary injection test
Secondary injection testing utilizes a separate circuit that
injects a signal in parallel with the output of the current
sensor. This signal is measured the same as a signal from
the sensor would be measured. The protection circuitry and
trip algorithm operate with no knowledge of the secondary
injection circuit. The trip unit and circuit breaker respond,
and configured operation is verified.
PXPM software initiates the functional testing using second-
ary injection. Note that the circuit breaker must be carrying
less than 5% of In prior to the test, and the password must
be entered to initiate the test. Testing for overload, short
circuit, and instantaneous performance is accomplished by
selecting the equivalent level of primary current to inject in
either absolute amperes or as a multiplier of I
r
. When a level
is selected, remember to consider pickup and tolerances per
the trip curves. You can test any phase, including neutral.
Note that neutral testing is for internal neutral (4- or 8-pole
breakers), external Rogowski sensors testing is limited,
and external iron-core CT sensors are not supported. The
trip unit’s display can be used to observe the current being
injected, and the time until trip.
