OSM-EE 18/5（EN 62368-1）测量接触电流时的地线通断状态

Standard: EN 62368-1:2014

Subject: Touch current measurement

Confirmed by TC108 at Busan, Korea, Oct 2018

Question:

Standard EN 62368-1 in clause 5.7.4 requires that at least one earthed accessible part shall be subjected to touch current measurement and refers to IEC/EN 60990:1999 for conditions of measurements.

a) Is it required to open switch e while conducting relevant faults 6.2.2.2 to 6.2.2.8 (parallel operation of switch e open with other switches)?

b) if a) is yes, doesn’t this means double fault (fault in earthing and in addition fault in network)?

Decision:

a) YES

b) NO, OSM is of the opinion that opening switch "e" is a loss of a safeguard. For measurements on class I equipment switch "e" must be open together with any combination of the other switches in the figure one at the time. Except for the line conductor switch "I" which simulates a line/neutral fault in the installation. If however the equipment contains a single pole mains switch,it shall additionally be tested with the mains switch in the equipment open and closed

问题：

EN 62368-1第5.7.4条款要求至少对一个接地的可触及导电零部件在电源连接故障后测量接触电流，测量方案参考IEC/EN 60990

a）测量IEC/EN 60990第6.2.2.2至6.2.2.8条款时，是否需要打开开关e？

b）假如a成立，是否形同双重故障（接地故障和断网故障）

决定：

a）是。要打开开关e

b）不。OSM认为打开开关e是一种无保护行为。对于Ⅰ类设备的测量，开关e必须打开后，再与其他开关进行任意组合，但用于模拟三相设备火零线故障的开关I除外。如果设备有单极电源开关，则要在设备启动和关闭状态分别进行测量

大侠提示：

以上是星形TN或TT系统设备接触电流测量网络原理图（本篇不谈及三相设备，但原理相同，朋友们自行翻阅IEC 60990即可）

开关e模拟不可靠接地设备保护接地导体断开故障

开关n模拟设备中性线导体断开故障

开关p模拟设备火零线极性反转

由于IEC/EN 60990第6.2.2.2至6.2.2.8条款要求每次只施加一个故障，所以凡是某个测量部位与地有电气连接，不论接地是否可靠（保护接地或功能接地），测量该部位的接触电流时开关e一律要打开（断开接地）再配合n/p开关（设备有单极开关则再加入启动和关闭状态）做任意组合测量。即使这时候是断开接地也断开零线的状态，不认为是双重故障。因为如果不断开接地，测量接触电流值会远远小于真实值（漏电流从接地那儿溜走了）

扫描二维码，添加关注“朱大侠的质检江湖”微信公众号，更多有趣安规小知识等着您哦~