地铁车站35/0.4kV变电所接地设计探讨

Study on Grounding Design of 35/0.4 kV Substation in Metro Station

为了提高地铁领域中降压变电所接地设计技术水平,符合国际IEC标准及我国国家标准,对目前地铁车站中降压变电所低压侧中性点接地方案进行研究,分析"多点接地"设计方案中存在的问题和"一点接地"设计方案的优点,提出合理的接地方案;通过对35kV系统接地故障引起0.4kV系统中的工频过电压、故障电压的分析,以及弱电系统的阻抗分析,得出接地工频电阻值小于1Ω的要求是不合理的,应充分利用结构钢筋作为自然接地极,不需要设置人工接地网。

The technical level of grounding design of step-down substation of Metro station in China has to be improved so as to accord with the IEC standards and China-National standards. In this paper,the disadvantages of multipoint grounding and the advantages of one-point grounding are analyzed based on studying the grounding scheme of neutral point in low voltage side of step-down substation of Metro station; and then a rational grounding scheme is proposed. The power frequency overvoltage and fault voltage of 0. 4 kV system induced by grounding fault of 35 kV system and the resistance of weak current system are analyzed. It is concluded that the demand of grounding power resistance value of less than 1 Ω is irrational; the structural reinforcing bars should be used as natural grounding electrode; therefore the manual grounding network is not necessary.