特高压长线路电容电流对距离保护的影响

特高压输电线路是全国统一电网的骨干网架．为保证其安全可靠运行,分析指出了特高压长线路的分布参数特性使传统距离保护的测量阻抗不与故障距离成正比．研究表明,线路空载运行条件下发生经高阻故障时短路电流相对偏小,而特高压输电线路电容电流大,因此线路电容电流可能影响阻抗元件出现超越或拒动问题．同时提出了特高压长线路距离保护的改进措施,理论分析与仿真测试验证了传统距离保护应用于特高压长线路时存在的缺陷,并证明了距离保护改进措施的有效性与可行性．

Influence of Capacitive Current on Distance Protection of UHV Long Transmission Line

UHV transmission line is the framework of the state power system.The secure and reliable operation of power system brings new challenges to distance protection.The analysis in this paper indicates that the dis- tributing parameter character of UHV long transmission line leads to the nonlinear relationship between meas- ured impedance of traditional distance protection and fault distance.Further research shows that fault current is comparatively smaller when high-resistance faults occur in the circumstance of non-load operating.However, the capacitive current of UHV transmission line is huge,hence it may cause exceeding-to-trip or failure-to-trip problems on the distance protection.The improved method for distance protection of UHV long transmission line is proposed.Theoretical analyses and simulation resuhs prove the defects of traditional distance protection when it is applied in UHV long transmission line;meanwhile,the validity and reliability of the proposed method for distance protection is confirmed.