Analysis of transient voltages and currents in short transmission lines on frequency-dependent soils

• Published in: Electric power systems research 2021-05, Vol.194, p.107103, Article 107103
• Main Authors: Pascoalato, T.F.G., de Araújo, A.R.J., Kurokawa, S., Pissolato Filho, J.
• Format: Article
• Language: English
• Subjects: Conductors; Electric power lines; Electric resistance; Electrical impedance; Electrical resistivity; Electromagnetic transients; frequency-dependent soils; ground-return impedance; Mathematical models; Parameters; Permittivity; Soils; Surge protectors; Transient analysis; Transient response; Transmission lines
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/j.epsr.2021.107103

•Real soils are characterized by its frequency-dependent soil electrical parameters which several formulations are proposed in the technical literature.•Frequency-dependent soil models are considered to compute the ground-return impedance by the Sunde’s approach.•Transient responses are obtained for different transmission lines on two types of ground which is represented by constant and by frequency-dependent soil models.•Significant variations can be obtained on the transient responses when fast-front disturbances are employed in the transmission lines.•Frequency-dependent soil models must be considered when soils of high resistivity and short transmission lines are present in the transient analysis. Accurate modeling of overhead transmission lines (OHTLs) for transient analysis require that the ground which the phase conductors are suspended be considered on the longitudinal impedance and transversal admittance matrices. In this framework, some models deal with the soil as an ideal conductor (constant resistivity ρg and relative permittivity εr). However, it is known fact that real soils are characterized by frequency-dependent (FD) electrical parameters (ρg(f) and εr(f)). Due to these conditions, different formulations to represent the soil with FD parameters have been developed in the last decades. In order to obtain a precise transient response, these models must be incorporated in longitudinal impedance, as the ground-return impedance, and transversal admittance matrices. In this article, an analysis to compute the impact of some FD soil electrical parameters on transient responses is carried out. These responses are calculated for an energization maneuver and ligtning direct strike on OHTLs with different lengths located above constant and FD soil parameter models of low and high soil resistive values. Results show significant differences between the transient responses obtained with the constant and FD soil models, which these variations are more pronounced for soils of high resistivity and for short OHTLs.