TP-7045 3/18c 69Section 9 Paralleling Generator Sets
Step Potential Cause Explanation Troubleshooting
Fault: Bus Sensing Connected to Generator Side of Breaker
1 Bus metering is
connected to the wrong
side of the paralleling
breaker
The controller sees the bus voltage always
matches the generator voltage, even when
the breaker contacts indicate that the
breaker is open.
Verify the bus metering is connected on the
load side of the paralleling breaker.
2 Breaker is closed and
status feedback is not
connected
The controller sees that the bus voltage
always matches the generator voltage,
even when the breaker contacts indicate
that the breaker is open.
Verify the paralleling breaker control wiring
is connected correctly and the status
feedback is connected to an “A” contact.
Fault: Failure to Open
1 Wiring between CB trip
relay and trip coil is not
connected
The CB trip relay is releasing, but the coil in
the breaker is not energizing, hence the
breaker is not opening.
Verify wiring to the trip coil (A4) is
connected correctly.
2 CB trip relay is not
receiving 24V power
The CB trip relay is releasing, but there is
no voltage to apply to the trip coil. This is
most likely to occur when the generator has
a 12V battery and there is an external
battery bank to operate the circuit breaker.
Verify the CB trip relay has a 24VDC
supply which is common to the CB close
relay and charge motor.
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