Basler Electric DGC-2020 - Manual (Page 97)

and control the breakers itself. In addition, the generator breaker can be automatically controlled by the
demand start/stop function, the exercise timer function, or a RUNWLOAD (run with load) start from
BESTlogicPlus. The generator breaker can be manually controlled using contact inputs and outputs or the
breaker buttons on the BESTCOMSPlus
® Control screen.
Breaker Operation
The DGC-2020 will attempt to close a breaker only after verifying that it can be closed. If the breaker
cannot be closed, the close request will be ignored. Only one breaker can be closed at a time.
Synchronization is required before closing the breaker to a live bus. Closure to a dead bus can be
performed after meeting dead bus threshold and timing requirements set by the user.
Determining if it is Acceptable to Close a Breaker
Before the generator breaker can be closed, it must be configured in BESTCOMSPlus
®. If only the
generator breaker is configured (mains breaker not configured) the DGC-2020 looks at user settings to
determine if the generator side of the breaker is stable and the bus side is stable or dead. If both the
generator and the mains breakers are configured and open, the DGC-2020 will close the generator
breaker if the generator side of the breaker is stable. If both breakers are configured and the mains
breaker is closed, the DGC-2020 will close the generator breaker after verifying that both sides of the
generator breaker are stable and the DGC-2020 is synchronizing.
Before the mains breaker can be closed, it must be configured in BESTCOMSPlus
®. If both the mains
and the generator breakers are configured and open, the DGC-2020 will close the mains breaker if the
mains side of the breaker is stable. If both breakers are configured and the generator breaker is closed,
the DGC-2020 will close the mains breaker after verifying that both sides of the mains breaker are stable.
Changing the Breaker State
Synchronization is required when closing a breaker to a live bus. Bus conditions act as a supervisory
control over the synchronizing function. If synchronization is in process and either bus goes unstable,
synchronization is suspended. To close the breaker on a dead bus, the DGC-2020 generates a breaker
close request. The closing function is then run without synchronization.
The GENBRK and MAINSBRK logic blocks contain both Open and Close logic outputs that can be
configured to energize an output contact, which would in turn operate the breaker. The Synchronizer
screen in BESTCOMSPlus
® is used to set the output contact type to pulses or continuous.
If the breaker does not seem to operate properly, refer to Section 8, Maintenance and Troubleshooting.
Synchronizer Operation
The synchronizer acts to align the generator voltage and frequency with that of the bus inputs when the
DGC-2020 desires to close the generator to a live, stable bus. Several situations must exist before the
synchronizer function will begin to execute:
•
The DGC-2020 must include the synchronizer option
•
The generator voltage must be stable
•
The bus voltage must be stable
•
The DGC-2020 must be in the process of initiating a breaker close
Breaker close sources are:
•
The DGC-2020 itself when the automatic transfer (ATS) feature is enabled.
•
The DGC-2020 itself when the Run with Load logic element receives a Start pulse in the
programmable logic.
•
The DGC-2020 itself when started from a Demand Start as part of demand start/stop and
sequencing.
•
The DGC-2020 itself when started from the Exercise Timer and the Run with Load box is checked
in the Generator Exerciser Settings.
•
Manual Breaker Close Input Contacts applied to the Open and Close inputs on the left side of the
Generator Breaker logic element in the programmable logic.
Any of the above close sources will work when the DGC-2020 is in AUTO mode. Only the Manual
Breaker Close Input Contacts can initiate a breaker closure when the DGC-2020 is in RUN mode.
In wye, delta, grounded delta, or single-phase AB configurations, the synchronizer aligns the voltage on
the GEN VA terminal with that on the BUS VA terminal, and the voltage on the GEN VB terminal with that
9400200990 Rev X DGC-2020 Functional Description 3-23