Design of the power system
“The 2,000 kilowatt emergency standby power system was sized to power the entire building,” says Tim Edwards, physical plant director for the facility. “This includes our ground-water heat pump HVAC system, lighting and elevators. We also have three UPS systems: one for our data room, one to back up our dispatcher area and one in the jail central control area.”
The 2,000 kW generator set was purposely oversized for the current building loads to allow for future expansion.
Soft-load transfer meets dual needs
“To meet the need for both backup power and load-shedding capability, the power system was designed with soft-load transfer,” says Jerry Boggs of Interstate Power Systems in Bloomington, Minnesota, the local distributor for mtu.
“This system makes the transition seamless between utility power and generator power during load shedding or system testing,” he says. “For load shedding, the generator is started and paralleled with the utility after the generator set reaches speed and frequency. Then, the master control ramps the load off the utility onto the generator and opens the utility breaker, completely disconnecting the utility.” When the utility curtailment period is over, the process is reversed.
Exercise and maintenance ensure reliability
To ensure reliable and worry-free operation, the generator set is exercised several hours every two weeks. The regular exercise also helps burn diesel fuel that could otherwise get old and cause fuel filters to clog. The soft-load transfer system is also ideal for testing the power system using the actual building load.
The new Blue Earth County Criminal Justice Center has met its initial new facility goals, including the vision of a building with minimal environmental impact. Helping to make that vision a reality is the flexible power system from mtu, proving that diesel power can also be environmentally friendly.