Anti-Interference Measurement Methods of the Coupled Transmission-Line Capacitance Parameters Based on the Harmonic Components

The traditional measurement methods of capacitance parameters of coupled transmission lines bring large measurement errors under a strong electromagnetic-interference environment. To solve this problem, new anti-interference measurement methods based on harmonic components are proposed. First, the voltages and currents at the head end and the tail end of the transmission line are sampled synchronously based on global positioning system ( GPS) technology, then they acquire the third harmonic components from the measured data with an interpolation fast Fourier transform algorithm, and substitute them to the calculation formulae, so that the power frequency interference signals are filtered as noise and the capacitance parameters can be accurately measured. The wiring diagram of line parameter measurement and the hardware structure of the measuring system based on GPS are given. The simulation results with PSCAD and an example of measuring two 200-kV coupled transmission lines are given. The comparison of measurement results between the proposed methods and the traditional methods is also shown.