Abstract
As a type of engineering model used for solving lightning-shielding problems, the electrogeometric model has been widely used for assessing lightning-shielding failure in high-voltage and extra-high-voltage transmission lines. However, with the increase of voltage levels in ultra-high-voltage lines and the growth of the air gap, the results previously yielded by the electrogeometric model are no longer consistent with those observed. Therefore, this study corrected the equation for the relationship between lightning current and striking distance, by using data on a negative polarity 50% discharge voltage from the rod-rod gap −20/2500 μs switching impulse test wherein an air gap of up to 10 m was first tested. Subsequently, the return stroke velocity distribution observed by Idone was newly applied. In addition, the correction factor for the ground was corrected in this study. Thus, an improved electrogeometric model for application in EHV and UHV transmission lines is proposed in this paper. By employing the improved electrogeometric model to calculate the frequency of lightning strikes of 500 and 1000 kV transmission lines in Japan and a 1000 kV transmission line in China, we found that the results calculated using the improved electrogeometric model were closer to the actual observations in Japan than was the original electrogeometric model. The improved electrogeometric model provides a more reliable foundation for lightning-shielding design of extra-high-voltage and ultra-high-voltage transmission lines.
Highlights
To construct a more secure, efficient, and robust power grid, promote grid interaction with neighboring countries, and construct a global energy interconnection, it is necessary to construct an ultra-high-voltage (UHV) grid involving the coordinated development of all voltage level grids to serve as the core power grid [1]
With the improvement of the grids’ voltage level, the dimension of power facilities increase significantly, resulting in the existing lightning-shielding analysis methods and measures becoming unsuitable for lightning-shielding design of EHV and UHV transmission lines
Proposed by Whitehead and Armstrong in 1968 [3,11] originally applied a negative polarity discharge characteristic curve with long air gap to deduce the equation for the relationship between striking distance and lightning current
Summary
To construct a more secure, efficient, and robust power grid, promote grid interaction with neighboring countries, and construct a global energy interconnection, it is necessary to construct an ultra-high-voltage (UHV) grid involving the coordinated development of all voltage level grids to serve as the core power grid [1]. With the improvement of the grids’ voltage level, the dimension of power facilities increase significantly, resulting in the existing lightning-shielding analysis methods and measures becoming unsuitable for lightning-shielding design of EHV and UHV transmission lines. This is an unsolved problem that hinders safe grid operation [2]. Many researchers have attempted to correct this method through various rod-rod and rod-plane gap discharge characteristic testing approaches Through such tests, EGMs can continually be improved on the basis of engineering experience and data obtained from long air gap discharge tests, thereby enabling the development of an EGM suitable for the lightning-shielding design for HV and EHV transmission lines. The observed 500 and 1000 kV lightning strike data obtained in Japan between 2000 and 2005 (85 in total) indicate that the actual observed frequency of lightning strikes (3.33 strikes/100 km/year) was much higher than the rate predicted by the classic
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