热老化对XLPE电缆电树枝特性的影响研究

Study on effect of thermal aging on electrical tree characteristics of XLPE cables

交联聚乙烯(cross‐linked polyethylene,XLPE)绝缘电缆受长期热老化的影响,其理化特性和介电性能会发生改变,影响电树枝的生长过程等电学行为。该文研究热老化对XLPE电缆绝缘电树枝生长特性的影响。对加速热老化样品进行电树枝生长试验,并利用差示扫描量热法(differential scanning calorimetry,DSC)、傅里叶变换红外光谱(fourier transform infrared spectroscopy,FTIR)测试和宽频介电谱测试研究XLPE材料微观结构与介电性能的变化。研究结果表明:重结晶反应和热氧反应是导致结晶度J_(c)和羰基指数Q变化的主要原因,进而导致XLPE中的极性分子发生变化,使介电参数呈先缓慢下降,后迅速上升的趋势。研究还发现热老化评价指标J_(c)、ε_(r)和tanδ与电树枝生长速率G_(10)(10 kV时电树枝的生长速率)、G_(12)(12 kV电树枝的生长速率)之间具有显著性相关,通过多项式拟合分析,在G_(10)、G_(12)与热老化评价指标之间建立等效关系。该研究在已知XLPE材料理化特性和介电性能的前提下,可判断XLPE电缆材料电树枝老化程度,为电缆绝缘和寿命预测提供一定的参考。

The physicochemical properties and dielectric properties of cross-linked polyethylene(XLPE)insulated cables can change under long-term thermal aging,affecting their electrical behavior,such as the growth process of electrical trees.This paper investigates the impact of thermal aging on the growth characteristics of electrical trees in XLPE cable insulation.Electrical tree growth tests were conducted on accelerated thermally aged samples,and differential scanning calorimetry(DSC),Fourier transform infrared spectroscopy(FTIR),and broadband dielectric spectroscopy tests were used to study changes in the microstructure and dielectric properties of XLPE materials.The results indicate that recrystallization reactions and thermal-oxidative reactions are the main causes of changes in crystallinity(J_(c))and carbonyl index(Q),which subsequently lead to changes in polar molecules within XLPE.This results in a trend where dielectric parameters initially decrease slowly and then increase rapidly.The study also found significant correlations between the thermal aging evaluation indicators(J_(c),ε_(r),and tanδ)and the growth rates of electrical trees at 10kV(G_(10))and 12kV(G_(12)).Equivalent relationships between G_(10),G_(12),and the thermal aging evaluation indicators were established through polynomial fitting analysis.Given the known physicochemical properties and dielectric properties of XLPE materials,the degree of electrical tree aging in XLPE cable materials can be determined,providing a reference for cable insulation assessment and lifespan prediction.