Influence of collection network parameters on performance of distance protection directional elements in offshore wind farms

Distance protection is one of the most advanced protection functions and is widely used in big-scale offshore wind farms (OWFs) as a main protection of collection array cables of different voltage levels. However, practical experience shows that performance of distance protection can be affected by various operational and design parameters of OWFs collection networks. The paper evaluates the influence of these parameters on response of distance protection directional elements of different types during single line to ground faults. Analysis has been performed using DIgSILENT PowerFactory software and the results have been verified by testing of several commercial distance protection relays in a laboratory environment. The paper reveals that the performance of some of the investigated distance protection directional elements can be severely affected by combinations of different system parameters of OWFs collection networks whereas some directional elements are stable. Several strategies to limit the negative effect of influencing system parameters are proposed.