Abstract
Electric power systems experience abnormal conditions like faults and disturbances which lead to power interruptions, loss of stability and blackouts. To prevent or at least minimize the fault consequences, a protection system is designed, installed and adjusted. Protection system consists of different types of relays that have different characteristics and functions. Here, the directional component is taken into consideration and compared with the proposed method. Whereas the conventional directional component may not identify the fault accurately when there is a variation of line fault output characteristics in a transmission line with DFIG. This thesis analyzes the output characteristics of fault voltage and circuit of DFIG-based wind farm by proposing the simulation model of doubly-fed Wind Farm using PSCAD/EMTD. Further, this thesis also studies the criterion for conventional directional component, which can operate only when there is a three phase short circuit from wind farm outgoing line and not with a short circuit from power grid. Based on the relationship between the results obtained from the direction of short circuit, the new criterion for the directional component is proposed. The criterion is based on the positive sequence polarization voltage phase comparison and the analysis for protection under various fault conditions such as rotational speed before the fault, crowbar protection, line length and fault location. The simulation results show cases that the new criterion guarantees the reliability of the directional component under various fault conditions of a transmission line with a DFIG.