Ultra High Speed Relay for EHV/UHV Transmission Lines -- Installation-Staged Fault Tests and Operational Experience

A new protective relay that solves many of the problems associated with the protection of EHV systems has been developed by ASEA, Sweden. Based on a traveling wave approach the relay system operates at ultra-high speed and can detect and determine the direction to a fault within a few milliseconds. The first relay system was installed in Wonneville Power Administration's (BPA) 500 kV system in April 1976. It represents a substantial contribution to BPA's present effort to shorten fault clearance times. The relay's setting procedure is described. The outcome of staged fault tests and one year's operational experience is presented and has confirmed the validity of the relay concept showing an ultra-high speed performance consistent with earlier laboratory results, with operating times of two to six milliseconds.