Double circuit transmission line parameter estimation using PMU

Accurate measurement of transmission line parameters is important for power system protection applications, especially distance relays whose zone settings are based on positive sequence line impedance. This paper presents a new method to estimate all the parameters for double circuit transmission lines. Double circuit transmission lines are widely used in the power system and are important from reliability, right of way and cost perspective. These lines are mutually coupled in zero sequence. In this paper we also propose a novel method to estimate the zero sequence mutual impedance during ground faults outside the double circuit transmission lines. The system is modeled in ATP and the algorithm is implemented in MATLAB. The result substantiates the claims of the proposed method.

I. Introduction

Double circuit transmission lines are extensively used by utilities for bulk transfer of power because of reliability, right of way and economic considerations. Due to the close proximity of the two circuits, the lines are mutually coupled. The positive and negative sequence coupling is negligible, whereas zero sequence mutual coupling is significant. The ground distance relays maloperates due to zero sequence mutual coupling and needs to be compensated for it. Hence accurate estimation of mutual impedance between the two circuits is necessary.