特高压工频无局放试验变压器外电场模拟计算分析及试验布置优化

多级串级式无局放工频试验变压器是特高压设备研制和试验必不可少的试验设备。为此,对典型的串级工频无局放试验变压器成套设备的外电场分布开展了研究,进行了有限元法数值计算。分别讨论了变压器布置于理想户外、室内距墙10m和距墙7m这3种工况下场强分布特点以及最大场强随净距增加的变化规律,分析了工频无局放成套设备自身结构对最大场强的影响。在特有的计算条件下,比较分析3种不同分压器屏蔽顶罩型式下的场强分布。在顶罩圆环半径和球半径相近时,双环屏蔽优于孤立球屏蔽,且屏蔽圆环截面半径越大,最大电场强度越小。通过分析空间电场分布的特点,得出其它试验辅助设备和空间杂散物项发生悬浮放电的规律。当接地杆与该变压器相对距离>10m时,一般不会发生空间悬浮电位放电;在计算模型中,灯具尺寸越小,对空间电场的影响越小,当灯罩半径>10cm时会发生局部起晕。最后对试验空间的优化布置给出合理化建议,其可作为试验大厅设计和试验设备布置的参考依据。

Electric Field Simulate Calculation and Experimental Layout Optimization of Ultra High Voltage Power Frequency Test Transformer Without Partial Discharge

Multi-stage series connection frequency test transformer without partial discharge is very important for design and experiment of ultra high voltage(UHV) equipment.We developed a finite element method(FEM) to analyze the electric field of the space with a typical series test transformer,respectively discussed the characteristics of electric field distribution for the cases that the transformer locates in ideal outdoor,10 m and 7 m away from the wall indoors,and analyzed its law of maximum field strength changing with the clearance distance.Moreover,we investigated the effect of the transformer itself structure on the maximum field strength,and calculated and compared the field distributions under some specific modeling conditions for three different types of top shielding.Simulation results demonstrate the shielding effect of dual-ring type is prior to single sphere type with the equal radiuses of ring and sphere,and the maximum value of electric field strength decreases with increase in radius of shield ring section.Combining with the space electric field distribution,a law of corona discharge caused by other auxiliary equipments and space stray items can be obtained that discharge will not happen when ground rod is more than 10 m away from the transformer and the effect on space field distribution decreases with smaller light size in the model,when the radius of light was longer than 10 cm,partial discharge will happen.Finally the layout of test transformer is optimized.