Considering transient short-circuit currents of wind farms in overcurrent relays coordination using binary linear programming

Abstract

The presence of wind farms in network makes short-circuit currents (SCC) seen by overcurrent relays (OCR) have not fixed magnitudes and contain transient states. The transient SCC changes real operating times of OCRs compared with calculated operating times, in addition to, mis-coordination between primary and backup OCRs. In this paper, a new method based on the dynamic model of OCR is proposed for considering the effects of transient SCCs of wind farms on the coordination of OCRs, and determining proper settings for them. Since the proposed optimization problem is highly complex and nonlinear, and also uses large amount of data, the intelligent optimization algorithms have not sufficient ability for utilizing in the proposed method. Therefore, the proposed coordination method is formulated as a binary linear programming (BLP)-based approach. It is also shown that the speed of proposed BLP-based method can be increased by removing some unusable variables. It is found from simulation results and hardware tests that the proposed method has better performance in comparison with conventional coordination methods.