油浸倒置式CT双针缺陷模型设计及其局放特性研究

Design of Double Needles Defect Model in Oil Immersed Inverted Current Transformer and Its Partial Discharge Characteristic

导体表面金属突出物是油浸倒置式电流互感器(CT)的典型绝缘缺陷之一。为掌握其放电特性,在实验室内制造了模拟导体表面金属突出物的双针缺陷模型,使用ANSYS有限元软件对其电场分布进行仿真计算,根据计算结果进行试验缺陷设置。利用PDCheck和罗氏线圈两种脉冲电流法检测手段,测量不同缺陷下的局部放电特性。结果表明:双针缺陷下的CT局部放电脉冲可分为较低与较高放电量两类,分别代表着油中发生的局部放电与油中气隙发生的局部放电。当双金属突出物之间的距离增大至30 mm时,局部放电脉冲在整个周期随机分布,在局部放电相位分布图中难以将其与噪声信号分离。

Metallic protrusion on the electrode surface is a typical insulation defect of oil immersed inverted current transformer. In order to know its partial discharge （PD） characteristics, a double needles defect model is made in the laboratory to simulate the metallic protrusion defect, and its electric field distribution was calculated by ANSYS finite element software. According to the calculation results, two defects were selected to test their PD characteristics by PDcheck and Rogowski coil. The results show that the PD pulses can be divided into two kinds according to the PD magnitude, one kind of pulses represents the partial discharge happened in oil, while the other kind of pulses represent the partial discharge happened in air gaps of oil. When the distance between two needles increases to 30 mm, the PD pulses distribute randomly in the whole cycle. These pulses can be hardly separated from noise signals in the phase-resolved partial discharge （PRPD） spectra.