Abstract
This paper evaluates the influence of frequency-dependent soil conductivity and permittivity in the transient responses of single- and double-circuit transmission lines including the ground wires subjected to lightning strikes. We use Nakagawa’s approach to compute the ground-return impedance and admittance matrices where the frequency-dependent soil is modeled using Alípio and Visacro’s model. We compare some elements of these matrices with those calculated by Carson’s approach which assumes the frequency constant. Results show that a significant difference can be obtained in high resistive soils for these elements in impedance and admittance matrices. Then, we compute the transient responses for single- and double-circuit lines with ground wires located above soils of 500, 1000, 5000, and 10,000 Ω·m considering the frequency constant and frequency-dependent parameters generated for two lightning strikes (subsequent stroke and Gaussian pulse). We demonstrate that the inclusion of frequency dependence of soil results in an expressive reduction of approximately 26.15% and 42.75% in the generated voltage peaks in single- and double-circuit lines located above a high-resistive soil. These results show the impact of the frequency-dependent soils that must be considered for a precise transient analysis in power systems.
Highlights
Several authors have studied the impact of the frequency dependence of electrical ground conductivity and ground relative permittivity (ε rg ) in the calculation of electromagnetic transients, especially those developed by lightning strikes on overhead multiphase transmission lines (TLs) or on grounding systems [1,2,3,4,5]
We understand that a more extensive analysis on the transient responses for commonly multiphase transmission lines located on the frequency-dependent soil electrical parameters are need. This objective of this paper is to evaluate the impact of frequency-dependent soil parameters in the transient responses of multiphase transmission lines generated by lightning strikes
As contribution of this paper, we analyse the transient responses generated by fast-front disturbances on single and double-circuit transmission lines with ground wires located above high resistive soils in a more realistic line configuration and length.We show that the proper modeling of soil affects significantly the transient analysis
Summary
Several authors have studied the impact of the frequency dependence of electrical ground conductivity (σg ) and ground relative permittivity (ε rg ) in the calculation of electromagnetic transients, especially those developed by lightning strikes on overhead multiphase transmission lines (TLs) or on grounding systems [1,2,3,4,5]. In 1930, Ratcliffe et al introduced one of the first laboratory measurements of effective conductivity σg and relative permittivity ε rg of the soil in radio frequencies [6]. In 1933, Smith-Rose presented a set of systematic measurements considering diverse soil samples [7]. Between 1964 and 1967, Scott proposed the first set of mathematical expressions to calculate the electrical parameters of the soil (σg and ε rg ) [8]. In the 70s, based on Scott’s formulae, Longmire and Smith proposed a semi-theoretical model, the Universal
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