Basler Electric DGC-2020HD - Manual (Page 107)

9469300990 Rev B 97
Synchronizer
Some applications require a generator set which can operate in parallel with other generators or a utility
bus. In order to parallel the generator, the speed and the voltage of the generator must be properly
matched to the bus. This is done by properly adjusting the generator’s speed control governor (GOV) and
automatic voltage regulator (AVR). Synchronization can be achieved manually by an operator or by the
use of an automatic synchronizer.
The DGC-2020HD digital genset controller has an integrated automatic synchronizer as an option to
perform synchronization. The controller monitors the voltages, frequencies, and phase relationships of
both the generator and the bus. It then sends a signal to the governor to increase or decrease the speed
of the engine to match the generator frequency and phase angle to the bus frequency and phase angle. It
also sends a signal to the voltage regulator to match the voltage levels. Once all of these conditions are
met, the controller sends a breaker close signal to the generator circuit breaker.
There are two types of automatic synchronizers available. A phase lock type of automatic synchronizer
controls the frequency of the generator and brings it into the predetermined phase angle window. After a
time delay expires while in the window, the close signal is given to the generator circuit breaker. The
anticipatory style of automatic synchronizer controls the slip frequency between the generator and the
bus. The synchronizer calculates the timing of the closing signal to allow the generator breaker to be
closed when the phase angle between the two sources is at 0 degrees. This calculation takes into
account the slip rate, generator breaker closing time, and the phase angle difference.
In order to minimize the effects of I/O communications delays on synchronization, it is recommended that
local I/O on the DGC-2020HD, rather than remote I/O on the CEM-2020, be used for generator breaker
open and close commands, generator breaker status, voltage raise and lower contacts, and speed raise
and lower contacts.
Operation
The synchronizer acts to align the generator voltage and frequency with that of the bus inputs when the
DGC-2020HD desires to close the generator to a live, stable bus. Several conditions must exist before the
synchronizer function begins to execute:
•
The DGC-2020HD must include the synchronizer option
•
The generator voltage must be stable
•
The bus voltage must be stable
•
The DGC-2020HD must be in the process of initiating a breaker close
Breaker close sources are:
•
The DGC-2020HD itself when the automatic transfer (ATS) feature is enabled.
•
The DGC-2020HD itself when the Run with Load logic element receives a Start pulse in the
programmable logic.
•
The DGC-2020HD itself when started from a Demand Start as part of demand start/stop and
sequencing.
•
The DGC-2020HD 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.
•
Breaker Close commands from the Control Screen in BESTCOMSPlus ®
•
Breaker Close commands initiated through the front panel of the DGC-2020HD.
Any of the above close sources work when the DGC-2020HD is in AUTO mode. Only the Manual Breaker
Close Input Contacts can initiate a breaker closure when the DGC-2020HD 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
on the BUS VB terminal. In other words, the DGC-2020HD 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
DGC-2020HD Synchronizer