A circuit model of vertical conductor using Semlyen's line model based on transient response calculated by FDTD

•A frequency dependent circuit model of a vertical conductor is proposed.•Semlyen's line model expressing the vertical conductor can be derived either from electromagnetic field analysis or measurement.•The method is applicable to not only a wind turbine, but also a transmission tower.

A circuit analysis method for analyzing a fast transient of a vertical conductor is proposed in this paper. The characteristic of the vertical conductor is previously calculated by a field analysis method, and is introduced into the circuit analysis method as a frequency dependent line model. In this paper, the vertical conductor is expressed by Semlyen's line model installed in Electromagnetic Transients Program (EMTP). The line parameters are derived by z-transformation method from discretized data obtained by Finite-Difference Time-Domain (FDTD) calculation. One of the application fields of the proposed model is a wind turbine tower. The proposed method enables an efficient surge simulation of the wind generation system with a high speed and high accuracy including a variety of internal circuits by the circuit analysis method. The incoming surge, which is determined by the tower characteristic, is introduced by the field analysis. The combined method is a practical approach to an accurate simulation for a surge simulation including vertical structures whose characteristic cannot be directly dealt with by the circuit analysis method. A calculated result obtained by a circuit analysis using Semlyen's line model derived by the proposed method shows a good agreement with a measured result using a reduced tower model. The proposed method accurately introduces transient characteristics of a tower into a circuit analysis method.