500kV变电站二次系统等电位连接铜缆的接地方式

变电站自动化系统的过电压防护水平与变电站各类设备的接地方式,二次设备的过电压承受能力有较大关系。参照相应的行业标准和反事故技术措施,分析了广东韶关500kV曲江变电站二次雷害事故,提出了等电位连接铜缆的具体接地三种方法:一是所有等电位连接网络均应可靠接地;二是二次系统的金属部件与共用接地系统的等电位连接应采取"S"形或"M"形连接网络结构;三是钢或镀锌钢等电位连接排的截面不应小于50mm2。分析表明,采用等电位连接铜缆的接地方法,可确保雷电流造成的地电位差不会对弱电设备产生干扰。

Study on Earthing Mode of Copper Cable with Equal Potential of Secondary System in 500 kV Substation

In the automation system of a substation,the voltage protection level is closely correlated with earthing mode of substation equipment and the over-voltage withstand capability of its secondary installations.In the light of relevant industrial standards and certain technical countermeasures against accidents,and based on analysis two accident cases due to lightning strikes at 500 kV Qujiang substation,Shaoguan,Guangdong province,detailed three earthing modes with isopotential connection of copper cable are proposed: 1.reliable earthing of all isopotential connection network.2."S"or"M"shaped network connection mode for isopotential connection for metal parts of secondary system and common earthing system.3.the steel or zinc-plated steel connecting buses shall have section area not less than 50 mm2.The analysis shows that earthing of isopotential connection with copper cable can ensure interference-free of week electrical installations caused by lightning current.