報告書番号

U01023

タイトル（和文）

2000年鳥取県西部地震における変圧器被害の発生要因の究明

タイトル（英文）

The cause of transformer damages during The 2000 Tottori-ken-seibu earthquake

概要 （図表や脚注は「報告書全文」に掲載しております）

平成12年10月6日に発生した鳥取県西部地震(Mjma7.3)により，日野変電所にある2台の変圧器のうち1台の変圧器の二次ブッシングが損壊した．これらの変圧器は，切土および盛土の異なる地盤上に設置されており，被害の要因は異なる地盤による地震動の違いであることが考えられた．そこで，日野変電所での本震時の地震動を推定し，変圧器の動的解析から被害の発生要因についての検討を行った．その結果，切土地盤上の変圧器では，地震動の卓越周波数とブッシングの固有周波数が一致した共振現象により，地震動が設計条件の約3.3倍の地震力となり，損壊に至ったことが分かった．さらに，もう一方の変圧器は，盛土地盤による非線形効果により地震力が二次ブッシングに対して効果的に作用しなかったことにより，設計条件の約1.3倍程度の地震力となった．その結果，盛土地盤上の変圧器は対照的に無被害となったことが明らかとなった．

概要 （英文）

Tottori-ken-seibu earthquake with the JMA magnitude of 7.3 occurred on 6 October, 2000, and electric power facilities sustained some physical damages. In Hino-substation, the one transformer located on cutting soil was damaged, though the other one located on embankment was survived. In order to discuss these damage features, we estimate earthquake ground motions considering ground condition in Hino-substation during the Tottori-ken-seibu earthquake, and utilize it to simulate a dynamic response of those two transformers. 1-D subsurface cutting soil and embankment models in Hino-substation is constructed by using exploration data, and validity of these models is discussed by characteristics of ground vibration estimated from microtremor records. Incident wave at the basement layer in Hino-substation is estimated from 1-D seismic response analysis using subsurface model of SMNH01 station. The estimated ground motions of Hino-substation have peak accelerations of 798 Gal on the embankment and 764 Gal on the cutting soil, respectively. Then we carry out response analysis for two transformers modeled into mass-spring system, using estimated ground motion. We demonstrate that more than three times as much as design input seismic force is found to act on destroyed bushing located on the cutting soil during Tottori-ken-seibu earthquake, whereas on the other one located on the embankment, the seismic force is revealed as the same as design input seismic force. These results well explain the state of damages in Hino-substation. As a result, we demonstrate that contrast transformer performance is caused by great difference of input seismic forces arising from different soil conditions.

報告者

キーワード