The Public Works building had an existing 600 V, 800 KW
generator designated for backup electricity in the event of loss of electricity
from the electrical utility.
A portion of the City's electricity bill every month was due
to peak KW demand during winter months.
The high peak KW demand set in the winter is applied as a KW demand
charge to a year of subsequent monthly bills.
There was an opportunity to operate the generator a few times a year
during the coldest times in winter months to reduce the peak KW demand and
avoid paying a high KW demand charge for many months. The savings on the electricity bills was much
more than the cost of some fuel used for a short duration to reduce this peak.
Power Precision designed and built new controls and 600 V
switchgear to take the place of the existing transfer switch. The existing transfer switch was removed and
the new switchgear was installed and connected to the existing power cables.
A generator and switchgear controller were installed in
another enclosure separate from the 600 V components for arc flash safety. The new controller is connected to the
generator engine controls and to the SCADA system for remote control and
monitoring of new controller and generator information via a data communication
With the new switchgear and controls, the same generator
will provide electrical power generation for peak-shaving in addition to
maintaining its function as a backup generator.
For peak shaving operation, the generator will synchronize
and operate in parallel with the electrical utility and supply electrical power
onto the electricity grid. In the event
of a power failure from the electrical utility, the generator will provide
electricity to the Public Works Building islanded from the utility until
utility power returns.
Now, with the ability to synchronize, the generator will
connect and disconnect without any disruption to the electrical supply for
testing and peak shaving operation and to make a ‘bumpless’ transfer of the
building loads back to utility power after operation.