Historical
IEC 60519-1 Ed. 3.0 en:2003
Safety in electroheat installations - Part 1: General requirement
"Lays down general safety requirements applicable to industrial electroheat installations, which may comprise electroheat equipment in the voltage range up to 3 600 V a.c. or 5 000 V d.c.."
International Electrotechnical Commission [iec]