An investigation into the use of adaptive setting techniques for improved distance back-up protection

Changes in power system operating conditions adversely affect the reach point accuracy of distance relays. This paper discusses adaptation of the settings of distance relays within an integrated digital hierarchical protection system for the optimisation of relay performance. Specific reference is made to adaptation of the zone 3 setting to ensure optimal relay performance over a wide variety of operating conditions. Results illustrating the performance of adaptive methods compared to conventional fixed setting are presented for an application study of the North Wales 400 kV transmission network, UK.