解决电压互感器二次侧故障对距离保护影响的新方法

分析了电压互感器（TV）二次侧两点接地故障对电压的影响，得出TV二次侧两点接地只影响零序电压，从而影响接地距离保护的正确动作。提出了一种基于参数识别的距离保护原理。该原理基于输电线路R-L模型，采用准确测量的零序电流在系统阻抗上的电压降代替受影响的零序电压，有效地解决了TV两点接地故障对接地距离保护的影响。ATP仿真和现场数据验证了该原理的正确性和可靠性。

New Method for Solving Potential Transformer Secondary Side Fault's Effect on Distance Protection Based on Parameter Identification

Distance relays can not operate correctly when two-points-to-earth faults in potential transformer secondary side occurs.It is because that the faults will cause mistake of voltage measurement.It is concluded that relays for grounding faults will be influenced,because only zero sequence voltage are influenced when two-points-to-earth faults in potential transformer secondary side occurs.Based on the R-L equivalent circuit of transmission line,a novel distance protection algorithm based on parameter identification is proposed.The zero sequence voltage is taken the place of the voltage calculated with zero sequence current(normally,which can be measured correctly) and the system impedance.By using the proposed method,the problem of mal-operation of distance relays caused by two-points-to-earth faults in potential transformer secondary side may be solved effectively.Simulation with data from ATP verifies the validity and reliability of proposed method.And its practicability is also verified by field data.