Case Study: Complex Customer Integration – Standby Generating Plant
IEA designed and built a 16,000 kW (16 MW) diesel standby generating plant for a large national defense and civil aviation customer’s world headquarters. The facility is comprised of ten 1,600 kW capacity generators, each with its own 5 kV generator output breaker, with five generators each configured onto one of two 5 kV tie buses. Each tie bus is then connected through a tie circuit breaker to form a common bus (refer to the SCADA Schematic below). The common bus is connected through separate 5kV to 12.5 kV step-up transformers through 15kV
switchgear to incoming independent 12.5kV utility feeds equipped with 12.5kV breakers that allow for either extended parallel operation with the utility or isolated operation. Separate cross connect 5kV breakers in the system design allows for the two 5kV buses to be operated independently, each parallel separately with its incoming utility feed to allow flexibility during utility or customer distribution equipment maintenance outages. However, this is not the normal mode of system operation. Since the local utility does not want paralleling to occur across independent utility feeds, normal paralleling operations occur through one side of the system, the generators loaded and then its incoming 15kV breaker is tripped open while then the other side is loaded and remains paralleled through its 15kV utility breaker.
During normal standby readiness, the tie bus and utility breakers remain closed. During parallel system startup:
- Ten 5kV generator breakers close.
- One common 5kV buss cross-connect breaker closes.
- One 12.5 kV utility breaker opens.
- _ customer internal breakers reposition.
The reverse occurs upon system shutdown. These operations are controlled by the system computer to ensure that no power loss or perturbations to power quality are sensed by the customer’s internal sensitive equipment.
Each month an integrated, loaded system test is conducted to confirm operability. The system has been successfully used by the customer in response to sporadic utility outages as well as extended continuous runs of over 100 hours in response to severe weather. In addition, the equipment is called upon to support the local utility interruptible program.