【摘要】 220 kV系统变压器中性点部分接地运行方式会使不接地主变中性点产生过电压,主变绕组承受过大的短路电流危险;虽然可以通过主变中性点并联间隙与避雷器进行保护,但间隙放电受环境因素影响分散性较大,容易产生误动作,且可能与避雷器绝缘配合失调。为此本文对北方某220 k V系统利用PSCAD/EMTDC软件进行建模仿真,分析了中性点串接小电抗前后的各种类型过电压和短路电流。仿真分析表明:中性点串接小电抗后,中性点过电压显著降低,不会再出现高达相电压的过电压,且有效避免失地过电压和间隙与避雷器绝缘配合失调的可能,中性点无需再安装间隙,只安装避雷器限制雷电过电压即可;主变绕组短路电流也随小电抗的增加而显著减小;同时中性点串接小电抗对铁磁谐振、雷电过电压也有一定的抑制作用;最后分析了加装小电抗后的中性点过电压绝缘配合和小电抗参数的选择。更多还原

【Abstract】 The partial transformer neutral grounding operation mode in 220 kV system will cause un-grounded main transformer neutral point over-voltage,the main transformer windings are subjected to excessive short-circuit current risk; although it can pass the main transformer neutrality. The point-to-point gap and the lightning arrester are used for protection,but the gap discharge is greatly affected by environmental factors,there is a certain degree of dispersion,it is prone to malfunctions,insulation mismatch occurs,and it is unfavorable for the safe and stable operation of the system. In this paper,PSCAD/EMTDC software is used to simulate a 220 k V system,and various types of overvoltage and short-circuit current in the neutral point before and after neutral point series small reactance are analyzed. Simulation analysis shows that after the neutral point is connected in series with a small reactance,the overvoltage at the neutral point is significantly reduced,and the overvoltage up to the phase voltage no longer occur,and no overvoltage is lost. Neutral points do not need to install the gap and only the arrester is required to install. The arrester can limit the lightning overvoltage; the short-circuit current of the main transformer winding also decreases significantly with the increase of the small reactance; at the same time,the small reactance of the neutral point also has a certain inhibitory effect on the ferromagnetic resonance and the lightning overvoltage; finally,the analysis that the neutral overvoltage insulation coordination after installing a small reactance and selection of small reactance parameters is made.更多还原