Relaying the B. C. Hydro 500-KV System

A unique relay system developed for B. C. Hydro's Peace River Project is described herein. The line protection consists of a semi-static dual primary, direct under-reaching transfer trip and permissive over-reaching schemes with microwave and power line channels connected redundantly. The relaying system was thoroughly tested on a model transmission line so that adequate consideration could be given to the effect of load current, swings, and transients related to series capacitors, line shunt capacitance and switching.