Abstract
This paper presents a probabilistic evaluation, based on Monte-Carlo method, for the estimation of insulation risk of failure of overhead transmission lines (TLs). The proposed method takes into account the wide-band model of tower-footing grounding system. The wide-band model of grounding system in frequency domain is obtained by the method of moment solution to the governing electrical field integral equations. The electrical parameters of soil are considered to be either constant or frequency dependent. The time-domain representation of the grounding system is inferred through pole-zero characterization of its associated frequency response. The case of a typical 400-kV transmission line is modelled in EMTP_RV with the tower-footing grounding system integrated with the transmission line (TL) system. The results of the paper show that the failure risk of transmission lines is affected by the grounding system model. This effect is more pronounced when the soil electrical parameters are assumed to be frequency dependent.
Highlights
Lightning overvoltages are the leading cause of insulation failure in transmission lines (TLs)
It is assumed that lightning strokes are uniformly distributed on an impact area, Fig. 1, where its width Ymax is limited by a distance that corresponds to the maximum peak current magnitude and derived from the electro-geometric model (EGM) of transmission line [4,5]
A probabilistic procedure has been performed in this paper for the lightning related failure risk calculation of TLs insulators, considering the wide band model for two types of tower footing grounding systems namely a vertical grounding rod and a simple square grid were studied
Summary
Lightning overvoltages are the leading cause of insulation failure in transmission lines (TLs). A method has been presented in [8,9,10] for wide band modelling of grounding systems in the EMTP-like tools. This helps with the accurate calculation of lightning overvoltages. The statistical parameters of lightning are taken into account and insulation failure risk is estimated by a link connected between MATLAB environment and EMTP_RV program. The calculation of the lightning related failure risk is carried out based on the Monte-Carlo method
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