绝缘纸在矿物油与菜籽油基天然酯中的加速热老化特性分析

Comparative analysis on accelerated thermal ageing characteristics of insulating paper in mineral oil and rapeseed oil based natural ester

天然酯较矿物绝缘油具有燃点高、可降解性好并且能延缓绝缘纸热老化速率等优点,作为提升变压器寿命或短时过载能力的液体绝缘介质正受到广泛关注。本文选取我国食用油中占比较大的菜籽油作为基油制备天然酯绝缘液,通过试验比较不同含水量绝缘纸在菜籽油基天然酯和矿物油中的加速热老化特性,并研究了氧气对绝缘纸在两种不同绝缘液中的加速热老化特性的影响。结果表明:在相同温度下,含水量是影响绝缘纸热老化速率的主要因素,氧气会降低菜籽油基天然酯对低含水量绝缘纸热老化速率的抑制作用。结合绝缘纸在绝缘液热老化过程中比强度与聚合度的实测数据,导出得到考虑含水量和氧气影响的绝缘纸纤维素分解反应数学模型,应用该模型可以对绝缘纸在绝缘液中的热老化过程和寿命进行预测。

Compared with mineral insulating oil,natural ester has the advantages of higher ignition point,better degradability,and can delay the thermal ageing rate of insulating paper,so natural esters are receving extensive attention as liquid insulating medium for extending the life of transformers or improving short term overload capacity.In this paper,we used rapeseed oil,which accounted for a large proportion of cooking oil in China,to prepare rapeseed oil based natural esters,and the accelerated thermal ageing characteristics of insulating paper with different water contents in rapeseed oil based natural ester and mineral oil were investigated.The effect of oxygen on the accelerated thermal ageing characteristics of insulating paper in the two different insulating liquids was studied.The experimental results show that at the same temperature,water content is the main factor affecting the thermal ageing rate of insulating paper,and oxygen will reduce the inhibitory effect of rapeseed oil based natural esters on the thermal ageing rate of insulating paper with low water content.Combined with the measured data of specific strength and degree of polymerization of insulating paper during thermal ageing in insulating liquid,a kinetic model of cellulose decomposition reaction rate of insulating paper considering the influence of water content and oxygen was established.The model can be used to predict the thermal ageing process of insulating paper in insulating liquids.