35kV干式空心电抗器匝间绝缘热-机联合损伤分析

Thermal-mechanical combined damage analysis of 35kV dry-type air-core reactor inter-turn insulation

针对干式空心电抗器现场运行中频繁出现的匝间绝缘故障,首先对电抗器进行正常运行、气道阻塞情况下的温度场进行仿真,得到了电抗器各包封的温度分布及热点温度,在此基础上,对电抗器匝间绝缘的主要绝缘材料聚酯薄膜进行材料热老化处理,对不同老化程度的试样开展了体电阻率、拉伸强度、局部放电以及击穿电压等测试,以对材料劣化特性进行表征.实验发现,随着老化程度的加剧,不同试样的体电阻率、拉伸强度和局部放电起始电压明显降低,但耐电强度变化不明显.分析认为,单一热老化并不会直接导致绝缘材料的击穿,而老化后材料机械强度的下降导致运行中力作用下出现的机械受损,可能是造成电抗器匝间绝缘击穿故障的原因.

In view of the inter-turn insulation failure of dry-type air-core reactors, the temperature field of reactor under the condition of airway obstruction and normal operation condition are simulated in order to get the temperature distribution and the heating point. Furthermore, thermal aging is done on the polyester film. The resistivity, tensile strengh, partial discharge （PD） as well as breakdown voltage tests are performed in order to characterize the insulation material degradation under thermal aging. The experiment results indicate that after thermal aging, volume resistivity, tensile stress as well as PDIV will obviously decrease while the changes of breakdown voltage are not obvious. This suggests that only thermal aging cannot directly cause the inter-turn breakdown. The mechanical degradation of insulation materials will cause insulation damage under mechanical stress, which will do damage to the inter-turn insulation system of the reactor.