基于数字局部放电检测的大型电动机主绝缘老化特性的研究

Study on aging diagnostics of large motor winding insulation based on digital partial discharge detection

大型电动机在长期的运行过程中 ,要遭受电、热、机械等多因子应力的联合作用 ,使主绝缘逐渐老化。为了研究主绝缘老化机理 ,评估其剩余寿命 ,需要对电动机定子线棒进行多因子应力综合老化试验 ,并寻找能反映主绝缘老化程度的特征参量。本文采用先进的数字局部放电检测技术对不同老化阶段的试样线棒进行了综合测试 ,分析了局部放电各参量与试样线棒老化程度的关系 ,给出了各种反映绝缘老化特性的指纹图形。测试结果表明 ,随着试样线棒的进一步老化 ,局部放电量、放电次数、放电能量呈增长趋势 ,最大放电脉冲相位产生偏移 ,其偏斜度由大变小。

In actual operation, the large motor stator winding insulation experiences various stresses, such as electrical, thermal and mechanical stress, and its dielectric strength deteriorates. It is necessary to conduct the accelerated multi stress aging test on motor stator bar specimen in order to explore its aging law, assess its remaining life and find a set of characteristic parameters which can indicate the condition of the insulation. The comprehensive measurements are carried out on the specimen at different aging state with the novel digital partial discharge (PD) measuring technology. The relationship between PD parameters and the degree of the aging is analyzed and the fingerprint diagrams are given. It is verified that the PD maximum magnitude, PD inception voltage, and PD energy tend to increase and the phase angle is found to deflect as well as the skewness of PD pulse distribution changes from positive to negative with further aging of the insulation. The results provide a basis for the evaluation of the residual life of large motor winding insulation.