摘要
特高压换流变压器绝缘承受的直流电压高,绝缘缺陷劣化发展迅速,且单凭局部放电(PD)量值和放电次数无法对绝缘缺陷的发展阶段进行分析诊断。为此,研究了特高压换流变压器内部油纸绝缘缺陷直流局部放电特征及其发展过程,构建了油纸针-板等7种局部放电模型。采用阶梯式升压法研究在长期外加电压作用下,绝缘纸板从起始放电到被击穿的整个缺陷发展过程中脉冲电流信号的实时特征及其统计特性,通过拍照的方式给出各模型各发展阶段纸板表面电腐蚀状态,并给出各相应发展阶段电场的空间分布。结果表明:直流局部放电发展过程复杂,初期以大放电脉冲为主,放电频率低,等待恢复时间随机性强;中期和末期以小脉冲放电为主,等待恢复时间均匀分布;临界击穿时等待恢复时间分布集中。结合多种放电模型直流局部放电试验,可断定不同缺陷结构从起始直流局部放电到击穿的过程中,其局部放电的总体发展趋势表现一致。
The direct-current （DC） withstand voltage of ultra high voltage （UHV） converter transformer is high and defects of insulators degrade rapidly. However, the developing process of the defects cannot be diagnosed only by partial discharge （PD） and discharge times. Thus, the developing process and characteristics of the defects on ultra high voltage converter transformer oil-paper insulation were researched, and seven common defects models were established. The high voltage was increased step-by-step from PD inception voltage until the model was broken down, and the pulse current signal＇s real-time characteristics and statistical properties during the developing processes of defects were obtained. The cauterization on the board surface of the models under different phases was recorded by photos to study their changing processes; meanwhile, the spatial distribution of the electric field under different phases was obtained. The results show that the PD under DC condition has a complicated developing process： it is consisted of mainly large pulse discharges with a low frequency and random waiting-recovery times at the initial stage; the pulse discharge becomes smaller and the waiting-recovery time has a uniform distribution at the middle stage; and.then the waiting recovery time tends to focus at a certain value at critical stage till breaks down. Combined with the DC partial discharge test of different models, it is concluded that, regardless of the defect structure, the partial discharge follows an identical development trend from PD inception voltage until the model breaks down.
出处
《高电压技术》
EI
CAS
CSCD
北大核心
2012年第12期3249-3260,共12页
High Voltage Engineering
基金
国家电网公司科技项目(编号略)~~
关键词
特高压(UHV)
换流变压器
直流(DC)
局部放电(PD)
油纸绝缘
放电模型
电场
ultra high voltage（UHV）
converter transformer
direct current （DC）
partial discharge（PD）
oil-paperinsulation
discharge model
electric field
