Basler Electric DGC-2020 - Manual (Page 96)

Demand Start/Stop Function
If the system demand is above the configured level setting for the specified time, and sequencing is
enabled, the unit will start, close its breaker, and take on load at the programmed load rate. Note the unit
will not start if sequencing is not enabled. If the unit is the only one on the load, it will provide the full load.
If the load drops below the stop level for the specified time, the unit will unload at the programmed load
rate, open its breaker, and stop. This mode works in conjunction with the run with load logic element,
otherwise it is completely independent of the other self-starting modes.
Interoperability of the Run with Load Logic Element and the Demand Start/Stop Function
These two functions can be used together; they are not independent of each other. Either one can start or
stop the system, but they can share functionality in that one can stop the system even if the other one
started it. Thus, if a machine was started by pulsing the run with load start, it could be stopped by demand
start/stop. This can be useful in a scenario where it may be desired to start a number of generators all at
the same time but sequence some off if the load does not require them. Run with load start could be
pulsed on all the units causing them to start and close their breakers, then demand start/stop and
sequencing could cycle them on and off as the load requirements change.
In order for Run With Load and Sequencing to operate reliably, it is recommended that the inputs to the
Run with Load logic element be pulsed rather than held constant. For example, if a unit was started by
sequencing, a pulse on the Run with Load Stop will shut down the unit. However, if the Run with Load
Stop is held constant, sequencing could never start a unit because the sequencing starts would be
immediately negated by Run with Load Stops. Similarly, if a Run with Load Start is applied and held
constant, sequencing cannot shut down the unit. Any stops generated by sequencing would immediately
be negated by the Run with Load Start.
Breaker Management
Introduction
The DGC-2020 is capable of controlling the generator breaker and the mains breaker. Once it is
determined that a valid breaker request is available, the DGC-2020 will attempt to operate the breaker if
possible. The user can choose to control only the generator breaker, the generator and mains breakers,
or none. BESTCOMSPlus
® is used to configure breaker management. Refer to Section 4,
BESTCOMSPlus
® Software, Breaker Management, for setting information.
Determining Breaker Status
The status of the breakers is determined by using BESTlogicPlus Programmable Logic to setup the
GENBRK and MAINSBRK logic blocks. These logic blocks have outputs that can be configured to
energize an output contact and control a breaker as well as inputs for breaker control and status.
Processing Breaker Requests
Types of breaker operate requests include:
•
Local Request - generated by internal functions and based on operating modes.
•
Com Request - generated through a communication port using BESTCOMSPlus
® or the front
panel HMI.
•
Logic Request - generated from BESTlogicPlus.
The type of response given for a local request depends on the operating mode of the DGC-2020.
RUN Mode
When in RUN mode, the generator and mains breakers can be closed manually using contact inputs or
the breaker buttons on the BESTCOMSPlus
® Control screen.
OFF or AUTO Mode (Not Running)
If operating in the OFF mode or AUTO and not running, the generator breaker cannot be closed because
the generator will not be stable.
AUTO Mode (Running)
When in AUTO mode and running, the mains fail transfer feature will automatically control the mains
breaker and the generator breaker or the external ATS (automatic transfer switch) will start the generator
3-22 DGC-2020 Functional Description 9400200990 Rev X