Investigation of distance relay settings under normal and stressed conditions in a wind farm environment

Abstract

This paper presents an adaptive methodology for setting distance relays connected to a network integrated with a wind farm system. The proposed trip boundary setting is capable of automatic adjustment with varying system conditions making the relay more reliable, faster and more accurate. A wind farm system delivers power according to the wind speed and penetration level at that instant. Distance relays having fixed trip boundary setting may underperform in such conditions as trip boundaries need to be varied according to the wind speed, penetration level, voltage ratio, power angle, system impedance and frequency. These variations in ideal trip boundaries, due to changing conditions, have been investigated. Furthermore, a smart coordination scheme is proposed for the improvement of backup protection (Zone 3) provided by distance relays. Inaccurate sensing of fault in Zone 3 due to load encroachment results in false tripping and makes the relay unreliable. The new scheme enables discrimination between fault inception and false tripping. A typical 400 kV system has been considered for simulation and testing in Matlab®/Simulink™ environment.