Basler Electric DGC-2020HD - Manual (Page 103)

9469300990 Rev B 93
Mains Breaker Closure Conditions
The conditions under which the DGC-2020HD will close the mains breaker are described in the following
paragraphs. A flow diagram (Figure 45) is provided to show the conditions under which the mains breaker
will close. This diagram considers breaker status, bus voltage stability, and synchronization conditions.
Command Agreement and Dead Bus Close Arbitration conditions are omitted for clarity. Refer to Figure
35 for a diagram of a generator and mains breaker configuration. Figure 37 illustrates the same
configuration with load bus metering.
Generator and Mains Breaker Control Configuration
In this configuration, the condition of the load bus must be assumed based on the status of the generator
and mains breakers and voltage stability of the generator and mains buses.
Before the mains breaker can be closed, either Generator and Mains Breaker Control or Generator and
Mains Breaker Control with Load Bus must be selected. When the mains breaker is open, the mains bus
is stable, and the load bus is not metered, the state of the generator breaker is checked. If the generator
breaker is open, the mains breaker attempts to close. If the generator breaker is closed and the generator
bus is stable, the mains breaker attempts to close.
Generator and Mains Breaker Control Configuration with Load Bus Metering
Before the mains breaker can be closed, either Generator and Mains Breaker Control or Generator and
Mains Breaker Control with Load Bus must be selected. If the mains breaker is already closed, the DGC-
2020HD still attempts to close the breaker. It is assumed that since the breaker is already closed, the
closure conditions have already been met.
When the mains breaker is open, the mains bus is stable, and the load bus is metered, user settings are
read to determine the states of the mains and load buses. If the mains and load buses are both stable,
the DGC-2020HD continually monitors the synchronization status between the mains and load buses.
The mains breaker attempts to close when the mains and load buses are in sync. If the mains bus is
stable, the load bus is dead, and the generator breaker is open, the mains breaker attempts to close.
DGC-2020HD Breaker Management