华北电力大学电气与电子工程学院, 河北省保定市 071003
School of Electrical and Electronic Engineering, North China Electric Power University, Baoding 071003, China
Ultra high-voltage direct current(UHVDC)transmission lines, crossing a long distance and complex regions, usually have a high fault rate. However, conventional differential current protection has shortages in tripping speed and adaptability to high-impedance faults. A pilot protection scheme based on correlation coefficient of current variables is proposed. Time-domain expressions of steady-state currents at both terminals of DC line are firstly derived by using state-space analysis. Then, the current components are analyzed, and the angular frequency of the damped oscillation term can reflect the grounded fault and can be measured by correlation coefficient. Moreover, the sum and difference of currents at both terminals are used to highlight angular frequency characteristics, and correlation coefficients of them are calculated, followed by the construction of relay criteria. Subsequently, by virtue of different characteristics of internal and external faults reflected by relay criteria, a pilot protection principle is proposed considering the effect of control features. The principle, without compensation requirement of distributed capacitor current, has lower requirements on communication channels, which is easier to be applied in the process of construction. Comprehensive simulation experiments demonstrate that the proposed scheme has better performance while dealing with high-impedance faults of UHVDC lines, and faster operation than the conventional differential current protection.
DAI Zhihui, LIU Ningning, ZHANG Cheng,et al.Pilot Protection for High-resistance Grounded Fault of UHVDC Transmission Line Based on Correlation Coefficient of Current Variable[J].Automation of Electric Power Systems,2019,43(19):156-163. DOI:10.7500/AEPS20181203011.