報告書番号

T97024

タイトル（和文）

線路用避雷装置による柱上変圧器雷害防止効果の評価

タイトル（英文）

LIGHTNING PROTECTION EFFECTS OF SURGE ARRESTERS FOR POLE TRANSFORMERS

概要 （図表や脚注は「報告書全文」に掲載しております）

配電線路用避雷装置設置柱における柱上変圧器用避雷装置の省略について検討し，以下の結論を得た。（１）線路用避雷装置から変圧器バンドまでの接地線長さを短くすることが変圧器保護にとって重要であることを明らかにした。耐雷設備の施設形態にもよるが，例えば接地線長さを２．５ｍ未満にすることで，約８割の直撃雷から変圧器を保護でき，変圧器用避雷装置の省略は可能である。（２）変圧器ブッシング電圧に対する接地抵抗値の影響は小さく，接地工事が省略できる可能性があることを明らかにした。（３）避雷装置が密に設置された配電線路において，架空地線の有無は，変圧器保護に関してほとんど影響がないことを明かにした。

概要 （英文）

THE OUTAGE RATIO OF POLE TRANSFORMERS REACHES TO APPROXIMATELY 40% OF TORAL DISTRIBUTION LINE EQUIPMENT OUTAGES. THEN, IT IS NECESSARY TO DEVELOP AN EFFECTIVE PREVENTION METHOD FOR POLE TRANSFORMERS AGAINST LIGHTNING. HOWEVER, LITTLE QUANTITATIVE RESEARCH ON OVERVOLTAGES OF POLE TRANSFORMERS HAS BEEN CARRIED OUT. IN THIS PAPER, WE CLARIFIED THE RELATION BETWEEN A LIGHTNING CURRENT AND A INDUCED VOLTAGE OF A POLE TRANSFORMER CAUSED BY LIGHTNING CURRENT, AND EXAMINED THE LIGHTNING PROTECTION EFFECTS OF SURGE ARRESTERS FOR A POLE TRANSFORMER. THE MAIN RESULTS ARE AS FOLLOWS: (1) THE LENGTH OF THE GROUNDING CONDUCTOR FROM AN ARRESTER TO A TRANSFORMER MOUNTING BRACKET HAS A SIGNIFICANT INFLUENCE ON THE PROTECTION OF TRANSFORMERS. IN THE CASE THAT SURGE ARRESTERS ARE INSTALLED ON EVERY SECOND POLE, 80% OF DIRECT LIGHTNING HITS DO NOT DAMAGE A TRANSFORMER WITH A 2.5M-LONG GROUNDING CONDUCTOR. (2) EVEN IF THE HIGHER GROUNDING RESISTANCE OF THE GROUNDING CONDUCTOR IS AS HIGH AS 200 OMEGA, A GOOD PROTECTION EFFECT IS OBTAINED. IN THE CASE THAT SURGE ARRESTERS ARE INSTALLED ON EVERY SECOND POLE, 70% OF DIRECT LIGHTNING HITS DO NOT DAMAGE A TRANSFORMER WITH A 2.5M-LONG GROUNDING CONDUCTOR. (3) THE EXISTENCE OF AN OVERHEAD GROUND WIRE HAS NO EFFECT ON THE PROTECTION OF TRANSFORMERS IN A DISTRIBUTION LINE WITH SURGE ARRESTERS INSTALLED ON EVERY SECOND POLE. (4) IN CASE THAT RESIDUAL VOLTAGE OF A SURGE ARRESTER CHANGED FROM 29KV TO 50KV, PROTECTION LIMIT DECREASES APPROXIMATELY 70%.

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