三元混合式绝缘油与绝缘纸板“液–固”组合体系的沿面闪络特性

油浸式电力变压器中油-纸绝缘体系的"液–固"交界面易发生沿面闪络,导致变压器绝缘失效。为考察新型三元混合式绝缘油对油-纸绝缘体系沿面闪络电压的提升效果,为此以矿物油–纸绝缘为参比,研究了交流电压下三元混合式油–纸绝缘体系的沿面闪络特性,分析了沿面闪络电压、油浸纸板表面损伤、以及沿面闪络后的油中溶解气体特性。结果表明:当针–板电极间距离由5 mm增大至20 mm时,与矿物油–纸绝缘体系相比,三元混合式绝缘油-纸绝缘体系的沿面闪络电压约高10%~20%,主要原因在于三元混合式绝缘油–纸绝缘体系中针电极尖端的电场值较小,且三元混合式绝缘油的击穿性能优于矿物油。经历多次沿面闪络后,三元混合式绝缘油浸渍纸板的表面损伤程度弱于矿物油浸渍纸板,且三元混合式绝缘油中溶解的C2H2及总烃类气体含量低于矿物油。该结果为安全应用三元式混合绝缘油提供了数据支撑。

Creeping Discharge Characteristics of the Liquid/Solid System Composited of Three-element Mixed Insulation Oil and Insulation Pressboard

Among oil-immersed transformers, partial discharges might be easily developed at the interface of insulation oil and pressboard, which will lead to the failure of transformer’s insulation. To explore the improvement of three-element mixed insulation oil on creeping discharge voltage of solid/liquid system, we investigated the characteristics of creeping discharges under AC stress in the system of the three-element mixed insulation oil and pressboard, including the characteristics of creeping discharge voltage, damage of pressboard and gases dissolved in insulating oil, with mineral oil as a reference. It is shown that the creeping discharge voltage of three-element mixed insulation oil and pressboard system increases by 10%~20% compared to that of the system of mineral oil and pressboard, with the electrodes gap distance varying from 5 mm to 20 mm. The main reason is that the electric norm at the needle electrode’s tip in the system of three-element mixed oil and pressboard is much smaller than that in mineral oil. Besides, the breakdown performance of three-element mixed insulation oil is better than that of mineral oil. After multiple creeping discharges, damage on three-element mixed insulation oil immersed pressboard is much slighter. The content of C2 H2 is much less dissolved in three-element mixed insulation oil than in mineral oil, while the total content of hydrocarbon gases has the same characteristics. The results of this paper provide a data support for the securely application of the three-element mixed insulation oil.