自耦变压器中性点小电抗对短路电流及变压器保护定值的影响

Influence of Small Neutral Reactance of Autotransformer on Short Circuit Current and Transformer Protection Setting

【目的】为评估500 kV自耦变压器中性点加装小电抗器对零序等值网络、等值阻抗回路及变压器保护定值的影响。【方法】分析此措施对500 kV侧、220 kV侧单相接地短路电流的影响,以实际工程为例,计算加装不同阻值电抗值的效果。【结果】经分析可知,500 kV自耦变压器中性点加装小电抗器后,对220 kV侧、500 kV侧单相短路电流均有一定的限制效果,220 kV侧效果更明显,电抗值增加到一定值后,限制效果趋于饱和,并得到最优阻抗值。【结论】研究加装不同中性点小电抗对短路电流及变压器保护定值的影响,对提升电网可靠运行具有重要意义。

[Purposes]This paper aims to evaluate the influence of installing small reactor at the neutral point of 500 kV autotransformer on zero sequence equivalent network,equivalent impedance circuit and transformer protection setting value.[Methods]The influence of this measure on the single-phase grounding short-circuit current of 500 kV side and 220 kV side is analyzed.Taking the actual project as an example,the effect of adding different resistance reactance values is calculated.[Findings]The analysis shows that after adding a small reactor to the neutral point of the 500 kV autotransformer,the single phase short-circuit current on the 220 kV side and the 500 kV side has a certain limiting effect.The effect on the 220 kV side is more obvious.When the reactance value increases to a certain value,the limiting effect tends to be saturated,and the optimal impedance value is obtained.[Conclusions]It is of great significance to study the influence of small reactance with different neutral points on short-circuit current and transformer protection setting value,so as to improve the reliable operation of power grid.