Mine equipment safety knowledge
(1) grade of power grid voltage in underground coal mines
1.Level of power grid
The underground power grid of coal mine is different from the ground three-phase four-wire power grid, and its voltage grade has special provisions. The "coal mine safety regulations" stipulates that the voltage of distribution network at all levels and rated voltage grade of various electrical equipment in the underground coal mine shall meet the following requirements:
(1) high pressure, not exceeding 10,000 V;
(2) low pressure, not exceeding 1,140v;
(3) the power supply voltage of lighting, signal, telephone and handheld electrical equipment shall not exceed 127v;
(4) the rated voltage of long-distance control line shall not exceed 36 V;
(5) when the electrical equipment in the mining area USES 3,300v power supply, special safety measures must be formulated.
2.Coal mine underground power supply system basic requirements
(1) coal mine underground belongs to a class of users, power failure will cause casualties and major production losses;
(2) the underground power supply (distribution) network of coal mine is not allowed to use the neutral point grounding mode, the underground distribution transformer neutral point direct grounding is not allowed, and the transformer or generator directly grounded by the ground neutral point is strictly prohibited to directly supply power to the underground;
(3) short circuit capacity of mine power network, which is generally limited to 50 mVA in old mines;New mines are no longer subject to this restriction (generally 100 mVA or 200 mVA);
(4) for mine high voltage power grid, measures must be taken to limit the single-phase grounding capacitor current to no more than 20a.
(2) types and selection regulations of underground electrical equipment in coal mines
2.Mine explosion-proof electrical equipment
(1) applicable to the classification of electrical equipment in explosive dangerous places.
Ⅰ classes: coal mine electrical equipment;
Ⅱ class: in addition to the coal mine of other electrical equipments used in explosive gas environment.
Each of these enclosures is marked with a special "Ex" mark for electrical equipment used in such a location.Mine explosion-proof electrical equipment shall conform to GB 3836-2000 "electrical equipment for explosive gas environment" series standards.
(2) explosion-proof marks of common explosion-proof electrical equipment in coal mines.
Mine explosion-proof sign of flameproof electrical apparatus for Exd Ⅰ;Mine intrinsically safe explosion-proof electrical equipment flag is Exib Ⅰ (or Exia Ⅰ);Mine explosion-proof and intrinsically safe explosion-proof electrical equipment sign for Exd (ib) Ⅰ (or Exd [1] Ⅰ);Mine increased safety type of explosion-proof electrical equipment flag is Exe Ⅰ;Mine increased safety and intrinsically safe explosion-proof electrical equipment flag is Exe (ib) Ⅰ.
3.Selection of mine electrical equipment
The selection of electrical equipment for mining shall conform to the specified requirements.Otherwise, safety measures must be taken.
General type portable electric measuring instruments must be used in places with gas concentration less than 1.0%, and the gas concentration in the working environment must be monitored in real time.
(3) mine cables
2.Underground cable laying in coal mine
Laying cables (other than those connected to handheld or mobile devices) shall comply with the following requirements:
(1) cables shall not be laid in the general return air lane and the special return air lane;
(2) the cable must be hanging, in a horizontal tunnel in mine under 30 ° or dip, hook suspension cable applications;In vertical shafts or dip in more than 30 ° and mine, cable clip, clamp or other clamping device for installation.The clamping device shall be able to bear the weight of cables and shall not damage cables;
(3) cables laid along the borehole must be tied to the steel wire rope, and casing must be installed in the borehole;
(4) the cable shall not be hung on the air pipe or water pipe and shall not be exposed to water.Do not hang anything on the cable;
(5) coil or "8" shaped cable shall not be charged.However, the cables that supply power to mining and excavating units shall not be subject to this limitation;
(6) communication and signal cables shall be hung on both sides of the shaft and power cables. If conditions are limited, they shall be laid in the shaft away from 0.3 m of power cables.In the roadway, it shall be laid above the power cable 0.1m or more;
(7) when high and low voltage power cables are laid on the same side of the roadway, the distance between high and low voltage cables shall be greater than 0.1m. The distance between high voltage cables and low voltage cables shall not be less than 50mm.
(4) underground protection for grounding, leakage protection and over-current protection in coal mines
Protective grounding, leakage protection, over current protection, usually known as the coal mine underground electrical network of the three protection.