Relay setting considerations and operational experience of a long500 kV transmission line

The large capacitive susceptance, large load magnitude, and substantial phase unbalance before and after a single-pole trip operation have a substantial effect on the performance of the protective relaying systems of the Minneapolis-Duluth 500 kV line. Computer simulation studies show that correct operation of the relays can be assured if these effects are taken into consideration in determining relay settings. The selection, performance, and operation of the primary and secondary relay system are discussed, indicating that the relaying protection used achieved substantial security and dependability     

On site relay transient testing for a series compensation upgrade

This paper describes tests on the relays on a long 500 kV AC line carried out on site using the RTDS (Real Time Digital Simulator) of the Manitoba HVDC Research Centre. The purpose of the tests was to examine the relay behaviour when series compensation is inserted in the line in 1993. New settings for the relays have been found which will give adequate cover for all faults although some faults will be entirely dependent on the communication link for short clearance times