交直流复合电压下热老化油纸绝缘空间电荷特性

Space Charge Characteristics of Thermal Aging Oil Paper Insulation under AC/DC Composite Voltage

换流变压器阀侧绝缘长期承受交直流复合电压的作用。为了研究油纸绝缘在交直流复合电压下空间电荷特性,该文开展了油纸绝缘加速热老化试验,搭建复合电压下电声脉冲法空间电荷测量系统,测量交流、直流以及交直流复合电压下油纸绝缘内部空间电荷积聚和消散情况,并进一步计算得到油纸绝缘陷阱深度。研究结果表明,不同老化状态的油纸绝缘在交直流复合电压下均出现铝电极附近的负极性空间电荷积聚,老化的油纸绝缘由于正负电荷不同的注入迁移特性,在交流电压下同样出现负极性空间电荷积聚;随着老化时间的增加,油纸绝缘中积聚的空间电荷先减少后增加;与直流极化相比,交直流复合电压极化后老化油纸绝缘的平均陷阱深度更大。

The valve side insulation of the converter transformer bears the effect of AC and DC composite voltage for a long time.In order to study the space charge characteristics of oil-paper insulation under AC and DC combined voltage,this paper carried out an accelerated thermal aging test of oil-paper insulation.This paper builds an electroacoustic pulse method space charge measurement system under composite voltage to measure the accumulation and dissipation of space charge inside oil-paper insulation under AC,DC,and AC/DC composite voltages.Furthermore,this paper calculates the trap depth of oil-paper insulation collapse.The research results show that oil-paper insulation in different aging states has negative space charge accumulation near the aluminum electrode under AC and DC composite voltage,and negative space charge accumulation occurs in aged oil-paper insulation under AC voltage due to the different injection and migration characteristics of positive and negative charges;with the increase of aging time,the space charge accumulated in oil-paper insulation first decreases and then increases;compared with DC polarization,the average trap depth of oil-paper insulation after AC-DC composite voltage polarization is larger.