XPLE电树枝生长过程中局部放电SHF信号特性研究

Characteristics of partial discharge SHF signal during the growth of electric tree in XLPE

交联聚乙烯(XLPE)电缆中电树枝的生长伴随局部放电(PD)的产生,二者间存在一定关联。XLPE材料绝缘强度较高,其中发生的PD在超高频(SHF,3~30 GHz)频段的信号幅值相对较高。文中采用基于针-板电极结构和XLPE绝缘材料的试样,在不同温度和电压下对电树枝生长过程中的形态和PD的SHF信号进行同步检测,分析了电压与温度条件对二者的影响,并研究了二者间的特征关系。研究表明XLPE中电树枝的长与宽和温度与电压呈正相关,电压较低时对分形维数较低,较高时分形维数无明显变化。SHF信号幅值也与温度和电压呈正相关关系,电压较高时,信号幅值呈现先增大再减小至平缓趋势,频率在电压较低时信号有一定程度下降。电树枝生长情况和SHF信号的幅值呈正相关关系,且当电树枝生长速度较快时,SHF信号的频率也会升高。

The growth of electrical tree in cross-linked polyethylene(XLPE)cables is accompanied by the generation of partial discharges(PD),and there is a correlation between the both.The rise time of the PD signal in XLPE with high dielectric strength is short,so the signal amplitude in the super high frequency(SHF,3~30 GHz)band is large.In this paper,the defect sample based on needle-plate electrode structure and XLPE insulation material is applied.The morphological of electrical tree and SHF PD signals are detected synchronously during the growth of electrical tree at different temperatures and voltages.The effects of voltage and temperature on the growth of electrical tree and SHF PD signals are analyzed and the characteristic correlation between the morphological of electrical tree and SHF PD signals in XLPE is studied.The results indicate that there is a positive correlation between the length and width of electrical tree in XLPE and temperature or voltage.The fractal dimension is usually lower at a lower voltage while it is not significantly changed with higher voltage.There is also a positive correlation between SHF PD signal amplitudes and temperature or voltage.Higher voltage leads to the trend that the amplitude of SHF signal increase firstly and then decreases to a plateau.The frequency of the signal decreases to a certain extent at a lower voltage.A positive correlation between the growth of electrical tree and the amplitude of SHF PD signals is acquired.The frequency of SHF signals also increases with a faster speed of the growth of electrical tree.