Power quality improvement with solid state transfer switches

The solid state transfer switch (SSTS) is designed to replace the mechanical autotransfer equipment currently in use to switch major industrial and commercial facilities from one feeder to another-a process that typically takes 0.3 to several seconds. A SSTS can also provide large customers with a cost-effective alternative to an in-house uninterruptible power supply system. This paper presents a new SSTS concept based on bi-directional control thyristor (BCT) technology for the mitigation of voltage deviations (sags or swells), interruptions and other power supply system faults. A utility application of the solid state transfer switch is described and its performance discussed.