Live-Line Measurement Method for Zero-Sequence Distributed Parameters of Double-Circuit Transmission Lines Using Nonpower Frequency Power Source

This article presents a distributed parameter model for double-circuit transmission lines. It introduces a live-line measurement method for zero-sequence distributed parameters, utilizing a nonpower frequency power source. The proposed method, based on the transmission matrix of double-circuit transmission lines, employs Laplace transforms and similarity transformation techniques to solve the transmission line equations, ultimately deriving the zero-sequence parameter transmission matrix. By leveraging GPS/BeiDou synchronized measurement technology, the voltage and current measurements, taken synchronously at both ends of the lines under various measurement modes, are incorporated into the derived formula to precisely calculate the zero-sequence distributed parameters. The proposed method was validated through PSCAD software simulations and compared with an enhanced nonpower frequency method based on a lumped parameter model. The proposed live-line measurement method has been applied in field measurements of the zero-sequence distributed parameters of two 220-kV double-circuit transmission lines in the Northeastern China power grid. Both digital simulation and field measurement results demonstrate that the proposed live-line measurement method, based on a nonpower frequency power source, achieves high accuracy under complex field conditions and maintains robustness in environments with electromagnetic interference.