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 ... Insulation monitoring devices for IT systems

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.