Reduced Order Model of A Lumped Parameter Frequency Dependent Transmission Line

Accurately fitting rational functions to the frequency response of modal impedances is very crucial for including frequency dependency in lumped parameter models of transmission lines. Vector fitting is widely used for fitting rational functions to the frequency response of modal impedances and then a R-L equivalent circuit is obtained from rational functions to get lumped parameter transmission line model in the modal domain. A single-step method is proposed in this paper to directly fit a R-L equivalent circuit to the frequency response of modal impedances. A close enough fitting is achieved with lesser number of passive elements using the proposed method. This method is validated by comparing its EMTP-RV simulation results for a 3-φ 220kV line with cascaded constant lumped parameter π-model and the standard frequency dependent line of EMTP-RV.