Orange County Sanitation District (OCSD) Potable Water Pumping Station Back-up Power Automation

Huntington Beach, CA

PACE provided design services to OCSD for a new standby power source to the existing OCSD Plant 2 City Water Pump Station.  The pump station is divided into two motor control centers (MCCs), with each MCC bus sub-fed by 480 VAC from one of two transformers located immediately outside of the station.  An interconnecting circuit breaker is located within the pump station switchgear, connecting the two MCCs, in order to energize either MCC from either sub-feed.  The project provides a third standby power source to the pump station and connects to the electrical circuits using two new automatic transfer switches (ATSs) located downstream of the transformers but upstream of the existing MCC main breakers.

This setup will maintain the ability to electrically isolate each of the MCCs using the existing MCC main breakers, but will also allow the use of the MCC inter-tie breaker to power across the two sub-feed circuits.  By having two ATSs, one on each circuit, if either or both of the sub-feeds were to lose power from the utility sources, the generator source would be activated to take over power service on the sub-feed.  The control automation for the system required careful consideration due to the multiple power feed sources, dual MCCs, and various control scenarios including a separate feeder for control/lighting power only.