纳米MgO/环氧复合电介质的空间电荷特性研究

Space charge characteristics of nano-MgO/epoxy composites

环氧复合材料在高温高场等复杂的工况下易积聚空间电荷,造成局部场强畸变,严重时将引发局部放电乃至绝缘击穿。通过纳米MgO颗粒与环氧树脂(EP)混合制备不同掺杂率的纳米MgO/EP复合电介质,采用差示扫描量热分析(DSC)测试环氧复合电介质的玻璃化转变温度;采用热刺激去极化电流法(TSDC)拟合计算环氧复合电介质的陷阱特性;采用电声脉冲法(PEA)测试环氧复合电介质的空间电荷特性。结果表明:纳米MgO颗粒的添加可以提高环氧树脂的玻璃化转变温度,抑制环氧树脂内空间电荷积聚。随着纳米MgO掺杂率的增加,纳米MgO/EP复合电介质的玻璃化转变温度先上升后下降,深陷阱能级和密度均先增大后减小;空间电荷密度先下降后上升,电场畸变的变化趋势与空间电荷的变化趋势相似。当纳米MgO掺杂率为3%时,纳米MgO/EP复合电介质的玻璃化温度达到最大值,抑制空间电荷积聚和场强畸变的能力最好。

Epoxy composite is easy to accumulate space charge under high temperature and high electirc field condition,which would lead to local electirc field distort,and in severe case,partial discharge would produce and insulation would break down.Nano-MgO/EP composites with different doping rate were prepared by mixing nano-MgO particles into epoxy resin.Their glass transition temperature was measured by differential scanning calorimetry(DSC).Their trap characteristics were calculated by thermal stimulation depolarization current method(TSDC).Their space charge characteristics were measured by pulse electroacoustic(PEA)method.The results show that the addition of nano-MgO particles can increase the glass transition temperature of epoxy resin and inhibit the space charge accumulation in epoxy resin.With the increase of nano-MgO doping rate,the glass transition temperature of epoxy composite increases at first and then decreases,the deep trap energy level and density of nano-MgO/EP composite increase at first and then decrease,the space charge density of nano-MgO/EP composite decreases at first and then increases,and the electric field distortion trend is similar with that of space charge.When the doping rate of nano-MgO is 3%,the glass transition temperature of the nano-MgO/epoxy composite reaches the maximum value,and the ability to inhibit the space charge accumulation and electric field distortion is the best.