Mixed-measurement of Zero-sequence Parameters of Parallel Coupled Transmission lines Based on Variable-frequency Electrical Measurement

Based on the demand of real projects that new overhead wires are been erected on the running wires with power flow, if zero-sequence parameters of the wires are needed, zero-sequence signals of different frequencies around the basic 50Hz can be added to the newly erected ones to generate zero-sequence signals, avoiding the short-term power down of the running wires. This paper analyses the structure of multi-coupled lines with different voltage levels, builds "double-Pi-shaped" zero sequence lumped-parameter circuit model, proposes a new algorithm based on variable-frequency electrical measurement to work out the zero-sequence parameters, including self-impedance, admittance and mutual parameters of the coupled lines. Simulation experiments for double circuit and triple circuit of different voltage levels are carried out in this paper. The simulation results reveal that the circuit models and zero-sequence parameter measurement algorithms are applicable to the zero-sequence parameters measurement of power system.