交直流复合电压下油纸绝缘典型缺陷局部放电发展阶段评估

Assessment of stages of partial discharge process of typical oil-paper insulation defect under combined AC-DC voltage

随着特高压直流输电工程的持续推进,直流局部放电试验技术对换流变压器绝缘状态评价的实用性问题一直备受关注。为形成有效的状态评价依据,提高换流变压器绝缘状态考核的准确性,本文研究了模拟典型放电类型的4种绝缘缺陷模型(油纸复合绝缘针板电极、变压器油隙针板电极、油隙平行板电极与沿面放电电极)在交直流复合电压下的局部放电特性。研究结果表明,各种缺陷模型在局部放电的不同发展阶段均有可作为判断依据的明显差异特征。本文从三方面给出了局部放电类型和放电发展前期、中期与后期的评估依据:(1)基于放电图谱Q-Δtpr e、Qmean-Δtpre、n-Q、n-Δtpre图谱特点的评估依据;(2)基于放电图谱偏斜度Sk、峭度Ku、不对称度Asy与相关度Cc等18项指纹特征参数的评估依据;(3)基于产气特性的评估依据。

With the continuous development of UHVDC project, the practicality of DC partial discharge test to evaluate the insulation state of convertor transformer has been paid much attention. In order to form an effective evaluation reference and improve the accuracy of the evaluation of the insulation state, the partial discharge characteristics of four kinds of insulation defect models of typical discharge type under combined AC-DC voltage are studied in this paper, i.e. the oil-paper insulation pin-plate electrode, the pin-plate electrode in transformer oil gap, the parallel- plate electrode in transformer oil gap and the creep discharge electrode. The results indicate that each defect model has different characteristics that can be used as the reference for judgment of different stages of partial discharge. This paper provides three references for judgement, i.e. the reference based on the characteristics of discharge pattern Q-Δtpr e、Qmean-Δtpre、n-Q、n-Δtpre, the reference based on the 18 finger print parameters Sk, Ku, Asy and Cc, and the references based on the gas production characteristics.