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供用电系统的接地保护是防止人身受到意外电击(间接接触防护)的一种有效措施,同时也是保证电网安全正常运行的重要手段。常见的系统接地保护型式主要有:TN、TT和IT系统。其中,TT系统也是目前起重机较为常用的一种接地型式。按照TSG Q7015-2008《起重机械定期检验规则》规定:“采用TT接地系统时,起重机电气设备的外露可导电部分(电源保护接地线)的接地电阻不大于4Ω或者起重机械金属结
Grounding protection for power supply system is an effective measure to prevent personal electric shock (indirect contact protection), but also an important means to ensure the normal operation of grid security. Common system ground protection types are: TN, TT and IT systems. Among them, the TT system is also a crane commonly used a type of grounding. According to the TSG Q7015-2008 Rules for Periodical Inspection of Crane, ”When using TT grounding system, the grounding resistance of the exposed conductive part (power protection grounding wire) of the crane electrical equipment is not more than 4Ω or the hoisting machinery metal knot