交联聚乙烯热老化与绝缘性能的关联关系

Relationship Between Thermal Aging and Insulation Properties of XLPE

为研究交联聚乙烯(cross-linked polyethylene,XLPE)绝缘材料的热分解活化能、电气特性和力学特性随热老化程度变化的规律,对交流电力电缆绝缘用XLPE材料在110℃下开展加速热老化实验。采用热失重(thermogravimtric analyzer,TGA)测试手段,对XLPE在20~600℃的热分解行为进行研究;采用交流击穿测试、宽频介电谱测试及体积电阻率测试,研究老化后XLPE试样的电气特性;采用拉伸实验测试,研究老化后XLPE试样的力学特性。结果表明:热老化使得XLPE的交联结构和结晶状态被破坏,XLPE活化能呈减小趋势。由于氧化反应快速进行,使得XLPE分子链发生断裂,交联结构变弱,导致XLPE绝缘材料严重劣化,其活化能、击穿强度、体积电阻率、弹性模量和断裂伸长率随老化时间增长呈下降趋势,而介电常数、介电损耗和电导率呈增加趋势。

In order to study the crossed-linked polyethylene(XLPE) insulation material in thermal decomposition activation energy,electrical and mechanical properties changing with thermal aging degree, accelerated thermal aging tests were carried out at 110 ℃on XLPE insulation material for AC cables. The thermal decomposition behavior of XLPE at 20~600 ℃ was studied by thermogravimtric analyzer(TGA) test. The electrical properties of the aged XLPE samples were studied by AC breakdown testing,broadband dielectric spectrum testing and volume resistivity testing;and the mechanical properties of the aged XLPE samples were studied by tensile test. The results show that the crosslinking structure and crystalline state of XLPE are destroyed by thermal aging,and the activation energy of XLPE tends to decrease. Due to the rapid oxidation reaction, the XLPE molecular chain breaks and the cross-linking structure weakens, resulting in serious deterioration of XLPE insulation materials. The activation energy, breakdown strength, volume resistivity, elastic modulus and elongation at break tend to decrease with the increase of aging time, while the dielectric constant, dielectric loss and conductivity tend to increase.