Frequency-dependent distributed-parameter modelling of counterpoise by time-domain fitting

A methodology has been developed for accurate distributed-parameter modelling of a transient on a buried bare conductor based on measured results. The developed bare conductor model including its frequency-dependent effect is implemented into the EMTP so that a transient simulation on a power system can be carried out by the EMTP. The EMTP simulation results agree well with measured results. Based on the wave propagation characteristics identified by the proposed method, it has been observed that the shunt conductance is dominant at a very low frequency and the series inductance plays an important role at an intermediate frequency. Finally the inductance and the shunt capacitance become dominant at a very high frequency. The observation explains most of the previous investigations. The results are expected to contribute to the derivation of analytical formulas for the series impedance and the shunt admittance, and also to predict transient induced voltages on control cables in substations.