Circuit switchers are designed for, tested, and used in substation protection schemes to clear fault transformer internal faults as well as transformer thru-faults. If the circuit switcher fails to successfully clear the fault, it is common for a circuit breaker, upstream from the substation, to perform the interruption. The utility may use a distance relay scheme, a transfer trip scheme, or a scheme that introduces a local, high-speed ground switch that closes, causing a single-phase bolted ground fault that the upstream breaker will respond to. Operation of the upstream will affect a much larger portion of the utilities’ customer base.

Middle Tennessee EMC’s Larry Taylor and Tom Speas of Southern States will present a session entitled “Local, Series-Connected Interrupters Enhance System Reliability” at the Finepoint Circuit Breaker Conference in October. SaskPower, (Saskatchewan, Canada) and Middle Tennessee EMC, while having slightly different drivers, have arrived at a similar solution where installation of series-connected interrupters provides a cost-effective solution that improves reliability and minimizes the portion of the transmission system impacted by the fault.

Taylor will discuss how Middle Tennessee EMC has implemented the series-connected interrupter design as a replacement for the previous system design. That approach used a circuit switcher as the primary interrupting device and a high-speed ground switch as the back-up device, which would close and cause a remote circuit beaker to clear the fault.

Speas will present how SaskPower has implemented the series-connected interrupter design as a cost-effective and reliable solution alternative to using distance relays or a transfer trip scheme to protect power transformers at remote substations.

Larry Taylor is a substation electrical engineer at MTEMC. He has 13 years of experience in the power industry. He graduated from Tennessee Technological University in 1995 with a B.S.E.E and started his career with Clark Control Systems, Inc where he designed and built utility control systems for U.S. and overseas projects. He then worked for R.W. Beck, a consulting firm for two years designing control systems for U.S. and overseas projects

Tom Speas is the sales and marketing manager for Southern States. He graduated from Lafayette College in 1976 with a B.S.E.E. He is presenting for Charles Shih, engineering supervisor, Substations, Lines & Stations Department at Saskatchewan Power Corp., Regina, Saskatchewan, Canada. Shih joined Saskatchewan Power in 1975, after graduating with a B.S.E.E. from the University of Saskatchewan.