Basler Electric DGC-2020HD - Manual (Page 92)

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DGC-2020HD waits until it detects that the phases are aligned between the generator and the mains
before performing the open transition from the generator back to the utility.
An Open Transition Delay is provided to allow a user-specified amount of time where both breakers are
open. For example, this may be used to prevent damage to large motors in the load by allowing them to
spin down completely during open transitions.
In closed transitions, when a mains failure occurs, the DGC-2020HD starts the generator after the transfer
time expires. The DGC-2020HD opens the mains breaker either before the engine starts or after the
generator becomes stable based on the Mains Breaker Open Configuration setting. After the mains
breaker is open the DGC-2020HD closes its generator breaker to drive the load. When the mains power
returns, after the Mains Fail Return Delay time expires, the generator synchronizes to the utility and
closes the mains breaker, paralleling the generator to the utility. While paralleled to the utility, the
generator ramps down load until the load is at or below the level of the Breaker Open Setpoint or until the
generator has been paralleled to the utility for the duration of the Max Parallel Time setting. Then the
DGC-2020HD opens its generator breaker, leaving the load on utility power. A cool down cycle is
performed and the generator is stopped.
Note
Closed transition override can be enabled through BESTlogicPlus
Programmable Logic. When the Closed Transition Override element is set
true, it forces a closed transition due to mains failure, overriding an open
Mains Fail Transfer Type setting.
Two logic elements are present in BESTlogicPlus Programmable Logic that can be used on Mains Fail
Transfer enabled machines. These two logic elements are Mains Fail Test and Load Take Over.
The Mains Fail Test logic element, when true, causes the generator to react exactly as if the mains has
failed. The following sequence of events occurs:
1. Mains Fail Transfer Delay time expires
2. Generator starts
3. Mains breaker is opened either before the engine starts or after the generator becomes stable
(based on the Mains Breaker Open Configuration setting)
4. Generator becomes stable
5. DGC-2020HD closes its generator breaker to drive the load
When the Mains Fail Test logic element is false, the generator reacts as if the mains has returned: the
Mains Fail Return Delay time expires and the generator transitions the load from the generator back to
the utility in an Open or Closed transition, according to the Mains Fail Transfer Type setting.
The Load Take Over logic element is similar, except that the machine does not act as if the mains has
failed, and the transfer and return delay timers are ignored. If the Mains Fail Transition Type is set to
Open and the Load Take Over logic element is true, the following sequence of events occurs:
1. Generator starts
2. Mains breaker is opened either before the engine starts or after the generator becomes stable
(based on the Mains Breaker Open Configuration setting)
3. Generator becomes stable
4. Generator breaker closes to drive the load
When the Load Take Over logic element is false, the DGC-2020HD opens its generator breaker and
closes the mains breaker to transition the load back to the utility. If the In Phase Monitor function is
enabled, the transition does not occur until the generator and utility phases are aligned.
If the Mains Fail Transition Type is set to Closed and the Load Take Over logic element is true, the
generator starts, synchronizes to the utility, and the DGC-2020HD closes the generator breaker. When an
auxiliary CT is configured to meter the mains bus, the mains breaker power level is measured. In this
case, the generator takes on load either until the power measured at the mains breaker is equal to the
Zero Power Flow Level setting, or for the duration of the Max Parallel Time. Zero Power Flow Level is
found in the Breaker Hardware settings. Once the Zero Power Flow Level or Max Parallel Time has been
reached, the mains breaker opens, leaving load on the generator. When no auxiliary CT is configured to
Breaker Management DGC-2020HD