FDTD analysis using constant parameter modeling for the calculation of transient responses and voltage profiles on multiconductor overhead transmission lines

FDTD models have been used since many years for the calculation of transients in overhead transmission lines (OHTLs), modeling them either as lossless or with frequency dependent parameters. Their major drawback, especially in the latter case, is their high computational cost. But FDTD models allow also the efficient calculation of voltage distributions with high discretization along OHTLs. This is significant in tracing transient overvoltages in short line segments in HV substations and in the calculation of signal voltage levels along transmission lines in Power Line Communication applications. Modal domain and phase domain frequency dependent transmission line models can provide accurate transient responses. However, when they are used in multi-segment configurations for the calculation of voltage distribution along transmission lines they may lead to error accumulations, combined with other limitations due to computational requirements or to the approaches in modal or phase domain analysis. In this paper, a constant parameter FDTD model for OHTLs is formulated, incorporating losses due to skin-effect and to the imperfect earth, capable to handle properly also non-homogeneous propagation. The proposed formulation is successfully checked against frequency dependent line models of the ATP/EMTP software, as well as against a formulated frequency dependent FDTD model. The proposed FDTD model proves to be numerically stable and is efficiently applied in voltage profile calculations.