基于电学性能的发电机线棒主绝缘热老化特性研究

Thermal ageing characteristics of main insulation for generator bar based on electrical properties

抽水蓄能发电机组长期运行过程中的热效应会对定子线棒主绝缘性能造成不利影响。本文以18kV抽水蓄能机组发电机VPI定子线棒为研究目标,制备试样并设计热老化方案,通过介电性能测试、电导测试及击穿特性测试,探究定子绝缘在不同热老化温度、不同热老化周期下的电学性能变化规律。结果表明:定子线棒弯曲段试样出现了较为明显且完整的损耗峰,在热老化过程中,绝缘材料的介电常数频谱整体随着老化周期的增加呈现增大趋势,其中弯曲段试样的介电常数随频率升高出现阶梯性下降趋势。随着老化的进行,试样的电导率逐渐上升,吸收比与极化指数均呈下降趋势,直线段试样和弯曲段试样的击穿强度均不断降低,其中弯曲段试样的击穿强度下降更为明显。

The thermal effect in the long-term operation of pumped storage generator sets will cause adverse effect on the main insulation performance of stator bars.Taking the VPI stator bar of an 18 kV pumped storage generator as the research object,we prepared samples and designed thermal ageing scheme.By means of dielectric property test,conductivity test,and breakdown characteristic test,the electrical properties of stator insulation under different ageing temperatures and different ageing cycles were explored.The test results show that there is obvious and complete loss peak in the bending section of stator bar.During the thermal ageing process,the dielectric constant frequency spectrum of insulating material shows an increasing trend with the increase of ageing period,and the dielectric constant of the bending section shows a stepwise decreasing trend with the increase of frequency.As thermal ageing progresses,the conductivity of samples increases gradually,and the absorption ratio and polarization index both show a decreasing trend.The breakdown strength of the straight section sample and the bending section sample continues to decrease,and the breakdown strength of the bending section sample decreases more significantly.