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.