输电线路综合阻抗纵联保护新原理

提出了一种基于综合阻抗的纵联线路保护新原理。利用故障时线路两端电压相量和与电流相量和的比值，来判断线路上是否发生故障。在外部故障时，该比值反映输电线路上的容抗，其虚部为一个绝对值较大的负数；内部故障时，其虚部为正数或为绝对值较小的负数，据此可以区分线路上的内部和外部故障。新原理易整定，本身具有选相能力，不受电容电流的影响，可用于带或不带电抗器补偿的线路，抗过渡电阻能力强。EMTP仿真和动模数据验证了新原理的有效性。

Novel Transmission Line Pilot Protection Based on Integrated Impedance

Based on the ratio between the sum of voltage phasors and the sum of current phasors at two terminals of the transmission line, which is defined as the integrated impedance, a new transmission line pilot protection principle is proposed. When an external fault occurs, the integrated impedance reflects the capacitance impedance of the line, its imaginary part is negative, and the absolute value of its imaginary part is large. When an internal fault occurs, the imaginary part of the integrated impedance on the faulty phase is either a positive value or a small negative value. According to such characteristics, the fault, whether it locates within the protected line or not, can be distinguished. The new criterion doesnot need capacitance current compensation, can be applied to the line with or without shunt reactor. Also, it can be easily set. Simulation with EMTP and dynamic model data shows that the presented principle has high sensitivity and reliability.