DIN EN 61557-3:2008 小于1000V交流和1500V直流低压配电系统中的电气安全性.防护措施的试验、测量或监控设备.第3部分:回路阻抗
Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 3: Loop impedance (IEC 61557-3:2007); German version EN 61557-3:2007