Pilot Protection Based on Zero-Sequence Current Resistance-Capacitance Component for Large-Scale Inverter-Interfaced Power Stations

Abstract

At present, zero-sequence current protection is generally used as the main protection for single-phase ground faults in resistance-grounded inverter power stations. However, limited by the principle, it is difficult for current protection to take into account selectivity and rapid action when the neutral point resistance is large, so there is protection mismatch with the inverter-type power supply for low voltage ride through leads to the risk of large-scale disconnection of non-fault lines. Aiming at the above problems, firstly, a fault analysis model of the inverter power station considering the capacitance to ground is established to study the distribution characteristics of resistive and capacitive zero-sequence currents in the collection system, when single-phase ground short circuit occurs on different types of lines. Then, based on the characteristic difference between the resistance and capacitance components of the zero-sequence current flowing through the two ends of the tie line in case of internal and external faults, a zero-sequence pilot protection algorithm is formed. Compared with the traditional zero-sequence current differential protection, the proposed protection algorithm only transmits logic information without synchronous sampling, and has significant economy. Finally, the feasibility and effectiveness of the proposed protection algorithm are verified by an engineering simulation example.