Electrical equipment that requires more than () in coal mine must be equipped with good protective grounding.

Electrical equipment with over 36 volts in coal mine must be equipped with good protective grounding.

Installation and maintenance standards for protective grounding of underground electrical equipment:

1. Requirements for protective grounding:

(1) The metal shell, frame, steel belt (or steel wire) of armored cable, aluminum skin and shielding sheath of electrical equipment with voltage above 36V and possibly dangerous voltage due to insulation damage must have protective grounding.

(2) The grounding resistance value of any protective grounding point on the grounding network shall not exceed 2 Ω; The resistance value of cable core and grounding connecting wire for protective grounding between each mobile and handheld electrical equipment and local grounding electrode shall not exceed 1Ω. And check it once every quarter.

(3) The grounding bus connecting the main grounding electrode shall be made of copper wire with a cross section of not less than 5mm2, or galvanized iron wire or flat steel with a cross section of not less than 1mm2 (with a thickness of not less than 4 mm). The cross section of connecting ground wire shall be copper wire not less than 25mm2 or galvanized iron wire not less than 5mm2 or flat steel (thickness not less than 4 mm).

(4) The main grounding electrode should be buried in the main and auxiliary water tanks. Local grounding electrode can be set in roadway ditch or other nearby wet place.

2. Local grounding electrodes should be installed at the following locations:

(1) Mining area substation (including mobile substation and mobile transformer).

(2) Caverns equipped with electrical equipment and high-voltage electrical equipment installed separately. ?

(3) Low-voltage distribution points or places with more than 3 electrical equipment within 1 meters.

(4) At least one local grounding electrode should be set separately at the heading face powered by the substation. There should be at least one local grounding electrode in the transportation lane, return air lane and centralized transportation lane (belt transportation line) of the coal mining face without low-voltage distribution point.

(5) metal connecting device for connecting high-voltage power cable. The protective grounding installation of single underground low-voltage electrical equipment should be carried out according to the requirements of local grounding installation, and the resistance value of grounding point must be ensured to be not less than 2Ω.