1. There must be a clear grounding mark in the protective grounding place.
2. Grounding device and cable in the metal reinforced core and metal block tide layer, armored layer connected, grounding line must be no less than the area of 6mm^2.
Voltage resistance level: Grounding device and the box and rack between the voltage resistance is not less than 3000V (DC), 1min does not penetrate, no flying arc.
Insulation Resistance: The insulation resistance between the grounding device and the box metal workpiece must be not less than 2x10^4mω, and the test voltage is DC 500V.