不同热老化程度下油纸绝缘沿面放电发展特性

Evolutionary Characteristics of Surface Discharge Within Oil-paper Insulation Under Different Thermally Aged Conditions

为研究不同老化状态下油纸绝缘沿面放电的发展特性,分析老化程度对放电特性的影响,进而提出表征老化程度和放电危险度的特征量。通过加速热老化制备了4种不同老化程度的油纸绝缘试品,在阶升电压下获得了其局部放电发展过程中的谱图和脉冲序列特性。研究发现,沿面放电脉冲多以脉冲簇群形式出现且有脉冲幅值逐渐增大,脉冲波形上升沿、下降沿快于空气中放电的情形;油纸绝缘老化程度对沿面放电的起始电压和击穿电压影响不大,但对放电量的威布尔尺度参数α值和平均放电功率P影响显著;连续放电时间差Δt对放电发展阶段和绝缘老化程度反应灵敏,可用于放电危险度评估指标。

The main aim of this paper is to investigate the evolutionary characteristics of surface discharge within the oil-paper insulation under the different aging conditions and extract parameters which are capable of characterizing the risk of discharge events. Oil-paper specimens of four kinds of different aging intervals are obtained through thermally accelerating aging processes and the developing processes of partial discharge （PD）, and pulse sequences are acquired under step-up applied AC voltage. The results show that the current pulses of the surface discharge usually appear in sequence with growing amplitude and the rise/fall time of pluses are faster than the counterparts in gas. The aging conditions of specimens hardly affect the partial discharge inception voltage （PDIV） and breakdown voltage （BDV）, however, the parameters P and a are sensitive to the oil/paper conditions. The interval between consecutive discharges, Δt, is strongly dependent on discharge stage and aging condition of the insulation, and it can be used as the key parameter to the risk assessment of the PD.