非正弦波电压下环境温度对云母-环氧表面间局部放电的影响

Effect of Ambient Temperature on Partial Discharge Between Mica-epoxy Surfaces at Non-sinusoidal Voltage Waveforms

电气设备局部放电在线监测通常在工频正弦波交流电压下测量,而离线局部放电试验则可以采用某些非工频电压和非正弦波电压激励。本研究以3种非正弦波电压为激励,即对称三角波电压、对称梯形波电压和近似方波电压,测量云母-环氧介质表面间空气间隙产生的局部放电,结合云母-环氧介质的频域介电谱测量,研究不同电压波形激励时环境温度对局部放电特性的影响。结果表明:3种电压波形激励下的放电起始电压均随着温度的升高而显著下降;三角波和正弦波电压下的局部放电特性随着温度的升高并无显著变化;随着温度的升高,平均放电量呈现较为规律的上升趋势,增加量与线性电压上升率的变化成正比;最大放电量在近似方波下较高,并随着温度的升高有明显增加的趋势;电压波形中水平电压阶段出现的局部放电活动受到环境温度的影响最为明显,近似方波中该阶段的平均放电次数和平均放电量随着温度的升高在整体上近似成指数增长趋势。

Partial discharges(PDs)in electrical equipment are normally detected with 50 Hz AC sinusoidal voltage stimulus in an online situation,but can also be measured at other non-sinusoidal and non-power frequency stimuli in off-line situations.In this work,three types of non-sinusoidal voltage waveforms,which are symmetric triangular-wave,symmetric trapezoidal-wave,and approximately square-wave voltages,were applied to investigate the effect of ambient temperature on the PD activity produced in an air gap between mica-epoxy surfaces,in combination with the frequency-domain dielectric spectroscopy(FDS)measurement of mica-epoxy dielectric.The results show that the PD inception voltage(PDIV)decreases greatly with the increase of temperature at three types of applied voltages.The PD behavior at symmetric triangular-wave and sinusoidal-wave voltages shows no obvious changing with the increase of temperature.With the increase of ambient temperature,the average PD charge exhibits regular increasing trend and the increment has almost proportional relation with the increasing rate of applied voltage;the maximum PD charge has the largest value at approximately square-wave voltage and also shows the increasing trend.The most obvious effect of temperature on PD activity lies in the constant voltage period of applied voltage.In this period,the average PD number and average PD charge both exhibit almost exponential increasing trend with the increase of temperature.