New methods and realization of live line measurement of zero sequence parameters of transmission lines with mutual inductance

Based on GPS technology and differential equations, two new methods of live line measurement of the parameters of transmission lines with mutual inductance are proposed. The principles and mathematical models of the steady differential method and the transient differential method are explained in details. Data processing algorithm by least square method is introduced in the measurement. The hardware structure of the measuring system and digital simulation results are given. Finally, an example of live line measuring 500kV transmission lines with mutual inductances in Northeast China power network is given. Comparison of results among the steady differential method, the transient differential equation method and the conventional method is also shown. The field measurement results prove that the new methods can meet the needs of live line parameter measurement of transmission lines.