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Basler Electric DGC-2020 User Manual

Page 98

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on the BUS VB terminal. In other words, the DGC-2020 aligns the generator phase AB L-L voltage with
the bus phase AB L-L voltage. In order for the synchronizer to provide correct phase alignment across a
breaker, the phase AB L-L voltages on the generator side of the breaker must be wired to the GEN VA
and GEN VB terminals on the DGC-2020. The phase AB L-L voltages on the bus side of the breaker (the
bus to which the generator will be connected when the breaker is closed) must be wired to the BUS VA
and BUS VB terminals on the DGC-2020. See Section 6, Installation, for a three-phase wye connection
for typical applications diagram.

In single-phase AC configuration, the synchronizer aligns the voltage on the GEN VA terminal with that on
the BUS VA terminal, and the voltage on the GEN VC terminal with that on the BUS VB terminal. In other
words, the DGC-2020 aligns the generator phase CA L-L voltage with the bus phase CA L-L voltage. In
order for the synchronizer to provide correct phase alignment across a breaker, the phase CA L-L
voltages on the generator side of the breaker must be wired to the GEN VA and GEN VC terminals on the
DGC-2020. The phase CA L-L voltage on the bus side of the breaker (the bus to which the generator will
be connected when the breaker is closed) must be wired to the BUS VA and BUS VB terminals on the
DGC-2020. See Section 6, Installation, for a single-phase AC connection for typical applications diagram.

Generator speed can be influenced by either the speed trim function, which is active at all times if
enabled, and the synchronizer. Since the speed trim function can cause some activity on the speed bias
outputs, when performing synchronizer troubleshooting it is recommended that the speed trim function be
disabled.

One way to tell if the synchronizer is active is to observe the DGC-2020 front panel. When the
synchronizer is active the DGC-2020 displays a synchronizer scope and angle and voltage error values
on the front panel.

Another method is to check for governor and AVR raise and lower output signals. First, disable the speed
trim function. If the governor or AVR bias control output type is contact, check for raise and/or lower
pulses coming from the DGC-2020 during synchronization. If the governor or AVR bias control output type
is analog, check the governor and/or AVR bias analog outputs on the load share module with a voltmeter
during synchronization. The voltages or raise/lower pulses should be changing when the synchronizer is
active. If there are no raise/lower pulses, or if the analog bias voltages do not change, the synchronizer is
not active.

A readily available method of verifying synchronizer operation during initial set up and commissioning is to
connect a light bulb from phase B of the machine being synchronized to phase B of the bus. Three bulbs,
one on each phase can be employed if so desired. The bulb(s) should be off or very dim when it is OK for
the breaker to close.

If it is not practical to use light bulbs, a voltmeter can be connected across the GEN VA and BUS VA
terminals. When the DGC-2020 reports that the slip angle is near zero, the voltage read by the meter
should be near zero. For single-phase ac systems, connect the voltmeter across the GEN VA and BUS
VA or GEN VC and BUS VB terminals.

If the DGC-2020 is indicating that the slip angle is at or near zero, but the slip angle measured across the
breaker is not near zero, it is likely that the signals measured by the DGC-2020 are not the signals that
are present at the breaker. In this case, all wiring should be checked to verify that the voltage at the GEN
VA terminal of the DGC-2020 matches the voltage present at the Phase A connection on the generator
side of the breaker, that the voltage at the GEN VB terminal of the DGC-2020 matches the voltage
present at the Phase B connection on the generator side of the breaker, and that the voltage at the GEN
VC terminal of the DGC-2020 matches the Phase C connection on the generator side of the breaker.
Similar verification should be performed from the BUS VA and BUS VB terminals on the DGC-2020 to the
Phase A and Phase B connections on the bus side of the breaker.

It is also required that phase rotation is the same on both sides of the breaker for synchronization to be
possible.

3-24

DGC-2020 Functional Description

9400200990 Rev X

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