大电机线棒超宽频带局部放电信号的时频特性研究

Study on the Joint Time-Frequency Characteristics of the Ultra-Wideband

利用开发的超宽频带局部放电测试系统 ,研究了退出运行的 30 0MW汽轮发电机定子线棒和 780kW电动机线棒的超宽频带局部放电特性 .运用联合时频分析技术 ,分析了这些放电信号的时频域特征 ,发现线棒的局部放电时域信号包含着丰富的高频分量 ,其直线部分和“R”部分的主放电特征峰出现的位置比较相似 .同时 ,还发现随着老化程度的加深 ,放电时延缩短 ,在时频联合域上能量密度向高频方向移动 .该发现为今后评估电机线棒的绝缘寿命提供了一种新的方法 .

The characteristics of the ultra-wideband partial discharge of both the stator bar of 300 MW turbo-generator out of service and the stator bar of 780 kW electromotor out of service are studied by using the developed ultra-wideband partial discharge detecting system. With the help of the joint time-frequency analyzing technique, the time-frequency characteristics of these samples are qualitatively analyzed. The results show that a partial discharge signal includes many impulses on which there are many small pulses, and the high energy density area of the partial discharge signal of the bars moves to the higher frequency after aging. The characteristic peaks of the straight part and R part nearly appear in the same place. The new method is proved useful for evaluating the insulating remnant life.