Is My UPS Distribution System Coordinated?

Abstract

Typical petroleum and chemical industry UPS (uninterruptible power supply) distribution systems are reviewed for interrupting device selectivity during short-circuit conditions. When selectivity is not achieved, alternative solutions are proposed. Distribution system selectivity comparisons are performed for standard circuit breaker panelboards, fuse panelboards and custom panelboards utilizing hydraulic-magnetic circuit breakers. When remote panels are implemented, application considerations include oversizing feeder cables or using step-up/step-down transformers. To determine the "ride through" response of individual operating plant UPS loads, the voltage depression time during UPS distribution system fault clearing is compared with the load "ride through" capability. General guidelines are provided for improved UPS distribution system performance