When the zero-sequence impedance of circuit Ⅰ of the double circuit transmission line is measured

zero-sequence induced current will flow through the path composed of overhead ground wire

earth and another circuit Ⅱ which is short connected and grounded in two ends and can be considered as shielding line with two terminals grounded

due to the mutual inductance between them.The path of those grounded lines is equivalent to a shorted secondary coil of circuit Ⅰ and cause demagnetization on its magnetic field.The measured value of zero-sequence impedance amplitude will be reduced as a result of the path formed by those grounded lines and the zero-sequence impedance angle will also be affected.Inaccuracy can be caused by this measurement error of zero-sequence impedance to relay protective setting

power flow calculation and stability analysis.This article analyzes Double Circuit Transmission Line with continuous ground zero sequence impedance grounding of the accuracy of measurement results

By EMTP of typical double-circuit transmission line tower with zero sequence impedance simulation

And analysis of the four 500 kV lines

two 220 kV lines

zero sequence impedance of the measured results

the measurement issues that should be noted

it puts forward some problems that should be paid attention to during the process of measurement and calculation.