服役25年变压器铁心中取向硅钢性能演变规律

Performance evaluation law of grain-oriented silicon steel in transformer core after 25 years service

研究了服役25年S9型配电变压器空载性能及铁心中取向硅钢的磁性能与涂层性能变化规律。运行25年后,变压器空载损耗上升至105.29 W,取向硅钢铁损P1.7为1.48 W/kg;取自铁心下轭1/4处、A相心柱中间位置、B相心柱靠近T节点处取向硅钢的绝缘涂层劣化程度依次上升,劣化最严重的B相心柱靠近T节点处部分硅钢片表面电阻系数低至2.6Ω·cm^2,涂层附着性为D级,扫描电镜下观察到涂层受腐蚀脱落。采用Infolytica电磁仿真软件模拟铁心温度场分布发现,铁心不同位置处运行温差可达9.1℃,长期处于相对较高温度、变压器油（酸和硫含量上升）及叠片间稀薄空气环境下取向硅钢绝缘涂层劣化严重。讨论了长时间服役后的二次取向电工钢片在配电变压器中的应用屏蔽措施。

The no-load characteristics of S9 distribution transformer and the magnetic properties as well as coating performance of grain-oriented silicon steel were studied. After 25 years in service,the no-load loss of transformer increased to 105. 29 W,while the core loss of silicon steel was 1. 48 W/kg. The degradation degree of insulation coating,which had serviced about 25 years,showed upward trend in position 1（ bottom iron yoke）,position 2（ phase A core column）,and position 3（ phase B core column）,respectively. The silicon steel located at phase B core column shows a dangerous surface resistivity of 2. 6 Ω·cm^2 and an adhesion of D level. Simulation result of temperature distribution base on the Infolytica software shows that the temperature difference in transformer core reaches about 9. 1 ℃,and the phosphate coating is deteriorated seriously after working in high temperature,transformer oil（ with the increased contents of acid and sulfur）and air environment for a long time. The shielding measures of second-used silicon steel sheets in distribution transformer were discussed.