零序电抗继电器在特高压交流输电线路上的适用性分析

特高压交流输电线路参数分布特征明显,阻抗继电器的测量阻抗与故障距离不再呈线性关系,而是呈双曲函数关系,因此接地阻抗继电器的动作特性受过渡电阻的影响严重,无法直接使用.传统高压、超高压线路普遍采用零序电抗继电器来提高抗过渡电阻能力.文中评估了零序电抗继电器在特高压线路上的适用性,分析了主要的影响因素.结果表明:零序电抗继电器的保护区明显缩小,同时动作灵敏度很低;影响保护区缩小的主要因素是采用保护安装处零序电流相位来估算故障支路电流相位的估算误差;影响继电器动作灵敏性的主要因素是较重的负荷电流.认为传统的零序电抗继电器难以直接应用到特高压交流线路上,新的算法有待研发.

Analysis on the Zero-sequence Reactance Relay Application in Ultra-high-voltage AC Transmission Lines

Due to the significant distributed nature of ultra-high voltage transmission lines, the measuring impedance is not linear but hyperbola function of the fault distance. The conventional earthing impedance protection relay can not be used directly since its high sensitivity to the interim resistance. To tackle the problem, zero sequence reactance relay (ZSRR) is widely adopted in high-voltage and extra-high-voltage transmission lines. The paper analyses the feasibility of using ZSRR in ultra-high voltage systems and key influential factors. Results indicates that the protective zone and sensitivity are largely reduced by the estimation error in the fault current phase angle based on the zero sequence current at the relay installed location, and the heavy load currents. New algorithm is needed for the application of ZSRR in UHV lines.