報告書番号

T00030

タイトル（和文）

電力設備接地系のための過渡応答特性解析手法の適用性 -‐メッシュ電極への拡張‐-

タイトル（英文）

Computer analysis of transient performance in a grounding grid based on the FD-TD method

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応答特性の解明は，その雷害防止やコストダウンに極めて重要である。このため当所では，電磁界解析手法の一種である時間領域差分法（Finite-Difference Time-Domain Method）に基づき，種々の接地系に対して適用可能な新しい過渡応答特性解析手法（FD-TD過渡応答解析手法）を提唱し，鉄塔基礎のような体積を持つものについては本手法が適用できることを実証している。 本報告では，細い電線で形成されるメッシュ電極までFD-TD過渡応答解析手法の適用範囲の拡張を目的とし，メッシュ電極の基本要素である正方形ループ電極について，TTWモデルを使用してFD-TD過渡応答解析手法により解析を行った。この結果を当所赤城試験センターにおいて実施した実験結果と比較したところ，両者は概略一致した。 本報告と既報から，送変電設備に用いられる種々の接地系に対して適用可能な過渡応答特性の解析手法がほぼ確立できた。

概要 （英文）

There are reports that lightning strikes on bulk transmission lines have caused serious accidents involving electrical apparatus, such as the failure of electrical transmission. It is important to analyze the transient performance of the grounding systems of electrical apparatus with respect to transient electric potential, transient current, and transient grounding resistance, in order to understand all the phases of such accidents and to apply the results to accident prevention. However, in the past transient performance has been difficult to evaluate. Therefore, a method for computational analysis of transient performance which could be easily applied to grounding systems under various conditions was highly desirable. We proposed a novel simulation method in which the transient performance is analyzed based on the finite-difference time-domain (FD-TD) method, and confirmed its validity through comparison between experimental results of the transient performance measured at the foot of a transmission tower and analytical results. In this paper we apply the proposed simulation method to grounding grids which consist of thin wires whose diameters are smaller than the spatial discrete interval in the FD-TD method. The true thin wire model is used to simulate thin wires in the FD-TD method and it is confirmed that the novel simulation method is applicable to the grounding grids through comparison between experimental results of the transient performance with respect to grounding grids and analytical results. The simulation method is expected to facilitate the rational design of grounding systems. The characteristic features of the method are (i) it can be used to simulate propagation phases of transient electromagnetic fields and enable their visualization, (ii) it can be used to calculate transient electric potentials, transient currents, and TGR from the propagation phases for transient electromagnetic fields, (iii) because the FD-TD method is a type of computational analysis method in the time domain, the calculated results can be more intuitive and more easily understood than those of analysis methods in the frequency domain, and (iv) it can be used to precisely model grounding systems, although there are limitations depending on the computer resources available.

報告者

キーワード