油纸绝缘在双极性衰减振荡冲击下的累积效应研究

Study on the Accumulating Effect of Bipolar Damped Oscillation Impulse on Oil-Paper Insulation System

电力变压器的内绝缘在雷电过电压的多次冲击下产生累积效应,影响其绝缘性能。研究表明实际雷电入侵波存在双极性衰减振荡波形的情况。首先用不同频率的双极性振荡衰减波波形,取低于其击穿电压的电压值,对油纸绝缘试品进行累积冲击,绘出其V-N特性曲线,验证了累积效应的存在性,探索了V-N特性的规律;继而用宽带频谱介电测试仪对在双极性振荡衰减波作用下累积冲击了100、200、300以及并未受冲击的绝缘纸进行测试,并对比分析了四种情况下复相对介电常数和介质损耗角正切值的变化规律,验证了累积效应对油纸绝缘的损伤。研究结果表明,双极性振荡衰减冲击电压和标准雷电冲击电压对油纸绝缘均存在明显的累积效应。在波形半峰值时间、所施加的电压幅值均相同时,频率越高的双极性振荡波击穿所需的冲击次数越少,复介电常数和介质损耗角正切值均随着累积冲击次数增加而变大,累积效应对油纸绝缘具有损伤。

The multiple invasion of lightning impulse in power transformers may cause accumulativeeffect on the internal insulation, which influence the insulation performance. The research indicates thatthe bipolar oscillating damped waveforms do exist in the actual waveform of the lightning overvohage.Bipolar oscillating damped waveforms with different frequency are firstly applied, and then the valuelower than the breakdown voltage is used to accumulatively strike the oil-paper insulation system. Afterthat the V-N performance curves are drawn to study the existence of accumulating effect, throughwhich the rules of V-N relation are also investigated. At last, the dielectric property parameters er andtanδ under different overvoltage waveforms and frequency are measured, and the facts of oil-paperinsulation failure by accumulative effect are verified. Research results indicate that, both bipolaroscillating dampedwaveform and lightning waveform have obvious accumulating effects oil-paperinsulation system. Under the same time of half-value and applied voltage magnitude, the higher thefrequency of bipolar oscillating damped waveform, the fewer the times of impulse for insulationbreakdown. The dielectric property parameters er and tanδ will increase with the times of impulsevoltage, meaning that accumulating effect does impair oil-paper insulation system.