報告書番号

H04009

タイトル（和文）

FDTD法による配電線誘導雷電圧計算手法の開発

タイトル（英文）

Development of simulation technique of lightning-induced voltages on distribution lines using the FDTD method

概要 （図表や脚注は「報告書全文」に掲載しております）

帰還雷撃のプラズマチャネルを直列接続したL素子で模擬することで，帰還雷撃電流の進展速度を制御する雷道モデルを開発し，L素子のインダクタンスと進展速度の関係を表す近似式を求めた。開発した雷道モデルを用いて電流進展速度を光速の1 / 3とした場合，FDTD法で計算した誘導雷電圧は従来法の結果とよく一致する。実際の大地を模擬して大地導電率を 0.001 S/m とし，雷撃地点が配電線の中間点に近い場合（雷撃地点 P），端点に近い場合（雷撃地点 Q）の2通りとして，FDTD法で誘導雷電圧の計算を行った。雷撃地点 P の場合はFDTD法と従来法の結果はよく一致する。雷撃地点 Q の場合は，帰還雷撃の遠方では両手法の結果の相違は大きくるが，雷撃地点 Q の場合は大地導電率の影響により最大電圧の符号が線路途中で反転することが知られているが，FDTD法の結果においてもこの現象をよく再現できている。

概要 （英文）

Digital circuits are now used for low-voltage control circuits in power plants for instance in substations. It is said, however, that digital circuits are vulnerable, compared with formerly used analog ones, to lightning-induced voltages which may cause malfunctions and failure. Therefore, lightning-induced voltages in low-voltage control circuits should be predicted precisely. A low-voltage control circuit forms a complicated three-dimensional wire arrangement which cannot be handled by conventional surge-analysis techniques based on the distributed-parameter line theory, and thus, we use the FDTD (Finite Difference Time Domain) method for the prediction of such lightning-induced voltages. This report presents the following two items regarding the FDTD simulation of lightning-induced voltages: (i) A lightning-channel model whose development speed of a return stroke can be controlled is proposed to apply the FDTD method to lightning-surge analysis. (ii) For validation purpose, the FDTD method was applied to the calculation of lightning-induced voltages on a single-phase distribution line. When the conductivity of the ground is infinite, the simulation results by the FDTD method agree well with those by conventional methods. When a finite ground conductivity is considered, a good agreement with an existing method is observed in the case where the point of strike is close to the midpoint of the distribution line. Although comparison shows some difference when the point of strike is close to one of the ends, the FDTD simulation can also reproduce the phenomenon that the polarity of peak-voltage profile turns over along the distribution line.

報告者

キーワード