New Approach for Precisely Measuring the Zero-Sequence Parameters of Long-Distance Double-Circuit Transmission Lines

Based on transmission-line equations and the distributed parameter model, a new approach is proposed to accurately measure the zero-sequence parameters of long-distance double-circuit transmission lines using voltages and currents measured at the ends of lines. The mathematical model of the proposed method is explained in detail, and the differential equations of two coupled lines with different self parameters were solved for the first time with Laplace transform to obtain all of the zero-sequence parameters. And this approach is easy to implement since the measurement process is simple. PSCAD simulation experimental results of double-circuit 500 kV transmission lines with line lengths changing from 200 to 1000 km and a comparison of the measurement results between the proposed method and the traditional method are shown. Simulation experiments validate that whether the two lines are short or long, the new approach has high accuracy even if there is system white noise and interference from other coupled lines.

I. Introduction

The parameters of transmission lines are fundamental data for power flow calculation, short circuit calculation, relay setting and failure analysis in power systems. The accuracy of transmission-line parameters is very important for ensuring the reliable operation of protective relays and other automation devices in power systems [1]–[3].