How large is the permissible overload current per square millimeter of the graphite electrode cross section?
The safe current is decided according to the conductor wire cooling conditions, cooling conditions, the overhead line package, an insulating layer and bare, cooling conditions are also different.
9A/mm2 safety current should be bare overhead, 5A/mm2 is obviously insulation lines, the indoor environment standards.
Overhead wires, radiating the best conditions, allowed the current largest. The insulated wire in the house is laid in the wall, which has the worst heat release conditions and the smaller permissible current, so there are different safety currents.
