TP-6953 7/19126 Section 7 Troubleshooting
Step Potential Cause
Explanation Troubleshooting
Fault: Bus Phase Rotation Mismatch
(Continued)
3 Generator sensing is
connected incorrectly
The controller measurement leads are not connected to the appropriate output
phases or the phases are incorrectly labeled.
Verify the sensing leads from the controller are connected to the
appropriate output leads from the generator. L1 should connect to phase A,
L2 to phase B, L3 to phase C, L0 to neutral.
4 Breaker to bus wiring
is inconsistent
In applications where the bus sensing is taken from a location other than the load
side of the paralleling breaker , it is possible to connect the wiring incorrectly
between the load side of the output breaker and the paralleling bus.
Verify the cable connections from the paralleling breaker to the paralleling
bus.
Fault: Bus Voltage Amplitude Mismatch- Phase A
1 The phase A voltage of
the bus does not
match the generator
The voltage measured on the bus sensing for phase A does not match the
voltage measured on phase A of the generator.
Verify the bus sensing wire for phase A is connected to phase A of the load
side of the paralleling breaker and there are no breaks in the wire.
Fault: Bus Voltage Amplitude Mismatch- Phase B
1 The phase B voltage of
the bus does not
match the generator
The voltage measured on the bus sensing for phase B does not match the
voltage measured on phase B of the generator.
Verify the bus sensing wire for phase B is connected to phase B of the load
side of the paralleling breaker and there are no breaks in the wire.
Fault: Bus Voltage Amplitude Mismatch- Phase C
1 The phase C voltage of
the bus does not
match the generator
The voltage measured on the bus sensing for phase C does not match the
voltage measured on phase C of the generator.
Verify the bus sensing wire for phase C is connected to phase C of the load
side of the paralleling breaker and there are no breaks in the wire.
Fault: Bus Voltage Amplitude Mismatch
1 The bus metering is
not connected correctly
The bus metering is not connected to the appropriate lugs of the load side of
the paralleling breaker (but there is some voltage present).
Verify the bus sensing wire for all three phases is connected to the
appropriate lugs on the load side of the paralleling breaker and there are no
breaks in any of the wires.
2 The generator
metering is not
connected correctly
The generator metering is not connected to the output of the generator. Verify the generator metering is sensed at the output of the generators. A
common mistake is to connect the metering to the center tap voltages V7,
V8, V9.
Fault: Phase Angle Mismatch
1 All of the bus sensing
wires are incorrectly
connected
The bus sensing wires must be connected to phase A, phase B and phase C of
the bus. If any two connections are reversed, the controller can detect the
reversed connections. This fault will only occur if all three wires are incorrectly
connected.
Verify the bus metering connections.
2 The phase connections
on the paralleling
breaker are
inconsistent with the
generator
The power leads from the generator to the paralleling circuit breaker must be
connected consistently. Phase A from the generator must go to phase A of the
line side of the paralleling (motor operated) breaker, phase B from the
generator to phase B of the breaker, and phase C of the generator to phase C
of the breaker.
Verify the output cable connections.
3 Generator sensing is
connected incorrectly
The controller measurement leads are not connected to the appropriate output
phases or the phases are incorrectly labeled.
Verify sensing leads from the controller are connected to the appropriate
output leads from the generator. L1 should connect to phase A, L2 to phase
B, L3 to phase C, L0 to neutral.
4 Breaker to bus wiring
is inconsistent
In applications where the bus sensing is taken from a location other than the
load side of the paralleling breaker, it is possible to connect the wiring
incorrectly between the load side of the output breaker and the paralleling bus.
Verify cable connections from the paralleling breaker to the paralleling bus.
Fault: Bus Frequency Mismatch
1 Abnormal condition Bus frequency is not similar to generator frequency with breaker closed. Verify bus metering is connected correctly. Reset the controller.
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