Historical
IEC 61557-8 Ed. 1.0 b:1997
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 8: Insulation monitoring devices for IT system
Specifies requirements for insulation monitoring devices which permanently monitor the insulation resistance to earth of unearthed IT a.c. and d.c. systems, and for IT a.c. systems with galvanically connected d.c. circuits.
International Electrotechnical Commission [iec]