热机联合应力对油浸纸板绝缘及机械特性影响研究

Influence of thermo-mechanical combined stress on insulation and mechanical characteristics of oil-impregnated paperboard

油纸绝缘系统在热、机械等应力共同作用下所发生的绝缘老化与破坏是电力变压器发生故障的主要原因之一,文中针对热机联合应力对油纸绝缘的影响开展了实验研究。对油浸纸板进行不同时间的热老化后施加不同形式的机械应力,测量纸板产生的应变,分析不同条件对油浸纸板的耐压时间、局部放电相位分布(PRPD)谱图、平均放电量等局放特征的影响。对未经老化的油浸纸板,机械应力加载时间越长、应力幅值越高或者应力频率越低,油浸纸板受到的破坏作用越严重,机械性能和绝缘性能越差。油浸纸板经过热老化处理后,机械应力对其绝缘性能和机械性能的影响趋势与未老化时类似,但热老化后PRPD谱图形态多呈现"兔耳状"。随着热老化时间的增加,纸板的绝缘寿命先有所上升,然后一直下降。文中研究结果可为热机联合应力下油浸纸板老化模型的建立提供试验依据。

The main cause of transformer fault is insulation aging and damage caused by internal oil-paper insulation system under thermal and mechanical stress. The effect of thermo-mechanical combined stress on oil paper insulation is studied. Oilimpregnated paperboard is subjected to thermal aging at different times and different forms of mechanical stress are applied,and the strain generated by the paperboard under stress is measured. The effects of different loading conditions on the characteristics of withstand time,phase resolved partial discharge( PRPD) spectrum,average discharge capacity and other partial discharge characteristics were analyzed. The longer the stress loading time,the higher the stress amplitude or the lower the stress frequency,the more severe the damage of the oil-impregnated paperboard under the same mechanical stress,and the worse the mechanical insulation and mechanical properties of the paperboard. Under the action of thermo-mechanical accumulation,the effect of different mechanical stress is similar to that of unaged,but the morphology of PRPD spectra after thermal aging is mostly " rabbit-like". With the increase of thermal aging time,the insulation life of paperboard first increased,then decreased.The results of this study will provide a reference for establishing an aging model of oil-impregnated paperboard under thermomechanical combined stress.