10kV配电网铁磁谐振消谐措施的仿真研究

在中性点不接地配电系统中,由于电磁式电压互感器(PT)励磁电感的非线性特性,在一定条件下容易产生铁磁谐振过电压,严重影响系统的安全运行。文章以嘉兴电力局斜桥变电所10kV配电网为模型,利用EMTP程序对PT高压侧中性点接非线性电阻、串单相PT、经消弧线圈接地、PT开口三角绕组接阻尼电阻或者分频消谐装置等多种消谐措施进行了详细的仿真分析和综合比较,发现中性点串单相PT的方式在消谐能力和全局性方面不如中性点串非线性电阻方式;在非线性电阻消谐方式下,正温度系数(PTC)热敏电阻和三次谐波滤波器可以较好地解决零序电压偏高的问题。此外,文章还定量研究了采用消弧线圈消谐的有效数值范围,分析了分频消谐装置在实际运行中不能很好消谐的原因,并对其他一些消谐方式的有效性进行了探讨。作者的工作可以为电力部门进行铁磁谐振过电压的防治提供较好的参考依据,对提高配电网的供电安全可靠性也有很高的实用价值。

Comparative Study on Ferroresonance Elimination Measures in 10kV Power Distribution System by Simulation Method

In the neutral ungrounded power distribution system, due to the nonlinear characteristic of excitation inductance of three-phase potential transformer (PT) the ferroresonance overvoltage is easy to occur under a certain condition, and this phenomenon will impact the secure operation of power system severely. Taking the 10kV distribution system in Xieqiao substation of Jiaxing power bureau for example and by means of EMTP software package, detailed simulation analysis and comprehensive comparative research on various measures to eliminate the ferroresonance, such as connecting single-phase PT to the neural point of three-phase PT high voltage side, connecting an arc-extinguishing winding to the neural point of power system, connecting a damping resistance or subharmonic ferroresonance eliminator to the broken delta winding of three-phase PT and so on, are performed. The analysis results show that connecting a nonlinear resistance is better than connecting single-phase PT in capability and entirety of ferroresonance elimination. Positive temperature coefficient (PTC) thermistor and triple frequency harmonic filter can reduce zero sequence voltage when a nonlinear resistance is used to prevent ferroresonance. In addition, the quantitative research on efficient numerical range of arc suppression coil, which is used to eliminate ferroresonance, is conducted, and the reason why the subharmonic ferroresonance eliminator can't prevent ferroresonance effectively are analyzed. Moreover, the validity of other ferroresonance elimination measures is discussed. It is proved out for electric power department to apply the results from above-mentioned research in practice to improve the power supply reliability of power distribution system.