基于脉冲电流法的低频与工频电压下油中电晕放电特性对比研究

Comparison of the Characteristics of Corona Discharge in the Oil under Low and Power Frequency Voltage by Impulse-Current Method

对于电容量较大设备的局部放电试验,采用低频电压代替工频电压可有效降低对试验电源的容量需求。低频电压下试验结果的有效性需要考核,为探究电压频率对绝缘油中电晕放电特性的影响,基于脉冲电流法开展了工频50 Hz到低频5 Hz下油中尖板电极的放电试验。研究结果表明,油中电晕放电的一些基本特性在低频电压下未改变,即正半周放电量明显大于负半周,放电分布在电压峰值附近,呈尖峰状。差异性主要是低频下尖峰特点趋于模糊;随着频率的下降,起始电压稍有上升;正、负半周放电停止相位提前,最大放电量、平均放电量与脉冲重复率整体呈下降趋势;各频率下放电相位分布图谱(PRPD)与统计图谱(qmean-φ、qmax-φ、n-φ与n-q)整体形状一致,但分布范围不同;统计图谱的部分分布特征参数有明显变化。试验结果可作为低频电压下局部放电模式识别的参考。与传统只用50 Hz电压进行试验对比,放电统计量随频率的变化趋势也提供了有关绝缘缺陷的更多信息。

For the partial discharge test of electrical equipment with large capacitance,the use of low-frequency voltage instead of power frequency voltage can effectively reduce the capacity requirements of test power supply.However the validity of partial discharge(PD)test under low frequency voltage needs to be evaluated.In order to investigate the influence of voltage frequency on corona discharge in the oil,the discharge test of the tip-plate electrode under the frequency from 50 Hz to 5 Hz was carried out based on the impulse current method.The results show that some of the main features of corona in the oil under low frequency do not change.The magnitude of discharge in positive half cycle is obviously larger than that in negative cycle.The discharge mainly distributes around the peak value of the voltage and forms a mountain shape,which becomes vague under low frequency.The inception voltage increases slightly.With the decrease of frequency,the terminal phase in positive and negative cycle are shifted to the earlier position.The average and maximum magnitude of discharge and repetition rate decrease.The phase-resolved partial discharge pattern(PRPD),discharge pattern(qmean-φ,qmax-φ,n-φand n-q)keep similar but have different range.Some characteristic parameters vary obviously.The results can be the reference for the recognition of PD mode under low frequency voltage.The trend of the measured parameters with the variation of frequency provides more information about the insulation defect than traditional measurements under a single frequency(usually 50Hz).