報告書番号

T03022

タイトル（和文）

数値電磁界解析に基づく垂直接地電極の高周波等価回路構成手法に関する妥当性

タイトル（英文）

Propriety of computational method of high-frequency equivalent circuit regarding vertical and rotatory symmetric grounding electrodes based on numerical analysis of electromagnetic field

概要 （図表や脚注は「報告書全文」に掲載しております）

電力設備接地系の（過渡）接地抵抗特性は，変電所におけるリレーや家庭内における情報端末など，半導体電子機器のEMCを考える上に重要である。このため，その簡便な推定ができ，これを電力系統の汎用過渡現象解析ソフトEMTPに組み込むことができれば実用的な意味は大きい。 回路理論から発展したEMTPは，地面に平行な線路やケーブルなどの解析には威力を発揮してきた。これは，地面に平行な線路やケーブルでは主にTEM波が伝搬すると考えてよいため，それらを解析式から分布定数線路や集中定数として容易にモデル化できることによる。しかしながら，地面に垂直な接地電極では，回路理論的なモデルがないため，EMTPでは取り扱えなかった。 このため，当所では，TM波が伝搬する地面に垂直な導体系に関して，それが回転対称であれば，インピーダンスを定義できることや，過渡接地抵抗の実験結果を再現できるFDTD過渡応答特性解析手法とRLC回路構成法などから高周波等価回路を求める手法（EG手法, computational method for Equivalent circuit of Grounding system）を理論的考察から提唱している。。 本報告では，地表面に垂直で回転対称な接地電極として代表的な配電用接地棒をとりあげ，その高周波等価回路をEG手法から求めた。そのうえでこれを用いたEMTP解析結果と実験結果との比較から，EG手法の妥当性を実証した。

概要 （英文）

It is important to study the transient performance of grounding systems for lightning surges, in order to ensure the electromagnetic compatibility (EMC) of sensitive electronics such as information devices and digital relays in substations and/or residential houses. Therefore, an easy method of estimating frequency response in order to represent the transient performance of grounding systems and its incorporation into EMTP are highly desired. EMTP based on circuit theory has been applied to resolve the transient performance of electrical apparatus consisting of cables and conductors parallel to the ground surface, which implicates propagation of TEM waves that are plane waves, and devices such as surge arresters represented by lumped elements, however, EMTP has not dealt with grounding systems that are vertical to the ground surface such as grounding rods of distribution lines because we do not have such model as impedance regarding vertical grounding systems. As for grounding electrodes rotatory-symmetric and vertical to the ground surface on which TM waves propagate, we have already reported that its high-frequency equivalent circuit was given by EG (computational method for Equivalent circuit of Grounding system), that was derived from theoretical approach based on electromagnetics and signal processing. Roughly speaking in EG, we calculate the potential and current in time-domain from the computational analysis of grounding systems based on the finite difference time domain method using derivative Gaussian pulse at first. Second, the impedance in frequency-domain is derived using the Fourier transformation of the potential and current in time-domain and then its high-frequency equivalent circuit is derived from the identification method of RLC circuit. In this paper, we show propriety of EG from making a comparison between experimental results and EMTP analysis.

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