Application of power quality recording instruments for monitoring medium voltage static transfer switch operation

Continuous, uninterrupted AC power is required for mission-critical sensitive commercial and industrial loads. One way of providing "seamless" distribution power to key loads is to make available two radially fed independent medium voltage sources with a high speed transfer switch for selection of a preferred or alternate source. Static transfer switches (STS) with switching times as fast as four milliseconds were developed for this purpose. Due to the importance of monitoring power that serves important loads and substantiating proper STS operation, power monitors are applied at the source and load sides of the switches. This paper describes the application considerations for and results of power monitors applied to STS installations.