湿热老化对电抗器匝间过电压耐受特性的影响

Influence of Demp Heat Aging on Withstand Characteristics of Inter⁃turn Overvoltage of Reactor

在干式空心电抗器的服役过程当中,水分有可能会大量地侵入包封并造成包封内绝缘的严重湿热老化而发生电抗器事故。但是目前对电抗器湿热老化并最终导致起火故障的详细过程和机理没有进行深入研究。由于湿热老化材料耐击穿性能下降,匝间绝缘在过电压的作用下有可能被击穿形成永久的匝间短路通路而发生故障,文中探讨这种短路故障发生的可能性,研究匝间过电压对匝间绝缘的影响。首先分析电抗器端口可能出现的最大过电压,然后利用链形回路计算电抗器在运行过程中可能遭受的最大匝间过电压,最后利用只包含两匝线圈的简易电抗器模型研究匝间过电压造成匝间绝缘故障的风险;结果表明:虽然电抗器在遭受过电压冲击时匝间绝缘有可能承受较大的过电压,但即使匝间绝缘已老化严重,过电压也不易将匝间绝缘击穿造成短路故障。

In the operation process of dry⁃type air⁃core reactors,moisture may invade the package,cause serious demp heat aging of the insulation inside the package,and eventually result in reactor accidents.However,at present the detailed process and mechanism of the demp heat aging and the fire failure of reactor have not been studied in depth.Due to the deterioration of the breakdown performance of the demp heat aging materials,the inter⁃turn insula⁃tion may be broken down under the action of overvoltage to form a permanent inter⁃turn short⁃circuit path and mal⁃function.In this paper,the possibility of such short⁃circuit failures is discussed and the influence of the inter⁃turn overvoltage on the inter⁃turn insulation is studied.First,the maximum overvoltage that may appear at the reactor port is analyzed.Then,the chain loop is used to calculate the maximum inter⁃turn overvoltage that the reactor may suffer during operation.Finally,a special reactor model containing only two turns is used to study the risk of inter⁃turn insu⁃lation fault by the inter⁃turn overvoltage.The results show that although the inter⁃turn insulation of the reactor,in case of suffering the overvoltage shock,is likely to withstand a large overvoltage,yet the overvoltage is not easy to damage the inter⁃turn insulation and lead to short circuit failure even if the inter⁃turn insulation is seriously aged.