報告書番号

W98008

タイトル（和文）

画像処理手法を用いた直流フリーアークの三次元挙動解析 --コラム経路推定手法の構築と長ギャップ水平アーク挙動の解析--

タイトル（英文）

Three Dimensional Analysis of DC Free Arc Behaviour by Image Processing Technique-Construction of Estimation Method of Column Path and Analysis of Long Gap Horizontal Arc Behaviour-

概要 （図表や脚注は「報告書全文」に掲載しております）

電力系統等で発生する故障点アークを想定した，電流域200～2000Ａの長ギャップ直流水平フリーアークを対象に，高速度ビデオカメラによる２方向同時撮影を行い，得られたアーク画像から画像処理手法を用いて三次元的なアークコラム弧心経路を推定し，さらにアークコラム長，コラムの空間的な拡がりおよびアークジェット部分の振舞について解析を行った。画像処理による弧心経路の推定においては，蒸気ガス等により生じる不鮮明箇所を考慮して，これらを良好に抽出できる二値化処理手法を提案している。また，アークコラム長および空間的な拡がりについては，各電流値ごとに３回ずつ行った実験結果より，電流値が同じであれば，これらの巨視的な時間変化はおおむね同様なものとなり，電流値依存性は発弧直後において顕著であることを明らかにした。さらに，アークジェット部分の振舞については，電極極性による明白な違いを明らかにした。

概要 （英文）

Long gap DC horizontal free arcs for currents in the range from 200 to 2000 A that may occur as fault arcs in power apparatus were observed simultaneously from two orthogonal views using the high-speed video camera to clarify the dynamic behaviour of the arc column. Image processing techniques were used to estimate the three dimensional core column paths of the free arc between the electrodes. For the estimation technique, we proposed a new method for treating the indistinct parts of the column in the original images of high current arcs by considering the variable threshold partially. The results of estimation of the core column paths of free arcs for up to 0.2s from ignition were used to investigate arc column length, spatial expansion of the arc column and deflection behaviour of the arc column near the electrodes that might be within the arc jet area. The following results were obtained from analysis of the core column paths from several tests:(1) Macroscopic changes in arc column length with time were roughly reproducible depending on the arc current magnitude. Significant differences in the dependence on the arc current magnitude were apparent in the first few milliseconds after ignition.(2) Macroscopic changes with time of the expansion radius, defined as the distance from the center axis between the electrodes to the furthest point in the core column path were also roughly reproducible depending on the arc current magnitude. For arc currents greater 1000 A, rapid increases in the change with time of the expansion radius were occasionally observed that were several times faster than macroscopic expansion. This was caused by sustained localized expansion without shortening of the arc column.(3) Deflection behaviour of the arc column near the electrodes showed differences between the anode and the cathode. The arc column near the anode tended to maintain a single direction. However, the arc column near the cathode tended to continuously oscillate over a wide range than near the anode.

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