Three-phase power and ground wire networks at four different coal mines, which have a special predetermined voltage levels. The "Safety Regulations for Coal Mines" stipulates that the distribution network voltage of various levels and the rated voltage level of various electrical equipment in coal mines shall meet the following requirements: high voltage, no more than 10000V; low voltage, no more than 1140V; lighting, signal, telephone and hand-held The supply voltage of electrical equipment does not exceed 127V; the rated voltage of the remote control line does not exceed 36V. When the electrical equipment of the mining area uses 3300V power supply, special safety measures must be established.

(2) Basic requirements for ensuring electrical safety

1. Special working conditions in coal mines

(1) There are explosive media such as gas and coal dust in the mine atmosphere. When the content reaches a certain amount, when electrical equipment or cable wires are sparked, a vicious accident such as burning or explosion will occur.

(2) Downhole roadways and electromechanical diverticulums often have dripping water, water spray, and even a large amount of water, and the relative humidity of the air is generally above 90%. Moreover, due to the influence of mine pressure, roofing and chipping accidents often occur, and electrical equipment, especially cables, are easily damaged by smashing, bumping, squeezing, and pressing. Therefore, personal electric shock accidents are prone to occur. Faulty sparks such as leakage sparks or short-circuit arcs are sources of electrical fires such as gas, coal dust, or explosions.

(3) Some underground electromechanical chambers and roadways have higher temperatures, and electrical equipment has poor heat dissipation conditions.

(4) The electrical equipment of the mining face moves frequently and often starts, and the load of the electrical equipment changes greatly.

(5) All power outages in the underground will cause such serious accidents as flooding mines, gas accumulation, personnel trapped or suffocating, and even gas or coal dust explosions.

2. Basic requirements for coal mine underground power supply system

(1) Coal mines belong to a class of users, and power outages will cause casualties and major production losses.

(2) The coal mine underground supply (distribution) power grid is not allowed to adopt the neutral point grounding working mode, and the neutral point of the underground distribution transformer is not allowed to be directly grounded. It is strictly forbidden to directly supply the transformer or generator directly grounded by the ground neutral point to the underground.

(3) The short-circuit capacity of the mine grid, the old mine is generally limited to 50mVA; the new mine is no longer subject to this restriction (generally 100mVA or 200mVA).

(4) In the mine high-voltage power grid, the single-phase grounding capacitor current must be limited so that it does not exceed 20A.

(3) Protective grounding

Since a voltage above 36V and insulation damage electrical equipment may carry dangerous voltage metal housing, frame, steel armored cable (or wire), transdermal, or lead shielding sheath and the like must be protected to ground. Mainly include: protective grounding grid, main grounding pole, local grounding pole, grounding busbar, connecting conductor and grounding conductor.

(4) Types and selection rules of underground electrical equipment

In order to safely use electrical energy in coal mines, whether it is a low gas mine, a high gas mine or a mine with coal (rock) and gas outburst, mining electrical equipment must be used. Mine electrical equipment is divided into two types: mine general type and mine explosion type.

1. General electrical equipment for mining

General electrical equipment for mining shall comply with the provisions of GB 12173-1990. The general type of mine is suitable for underground coal mines without gas, coal dust explosion hazard or other similar underground industrial production departments.

2. Mine explosion-proof electrical equipment

(1) Classification of electrical equipment used in explosive hazardous locations. Class I: Electrical equipment for coal mines; Class II: Electrical equipment for other explosive atmospheres other than coal mines. The distinctive features of these equipment enclosures are the special sign "Ex" for the use of electrical equipment in such locations. Mine explosion-proof electrical equipment shall comply with GB 3836-2 000 series of electrical equipment for explosive gas environment.

(2) Explosion-proof type and code of mine explosion-proof electrical equipment. Explosion-proof electrical equipment "d", increased safety electrical equipment "e", intrinsically safe electrical equipment "i", positive pressure electrical equipment "p", oil-filled electrical equipment "o", sand-filled electrical equipment" q", encapsulated electrical equipment "m", non-sparking electrical equipment "n", airtight electrical equipment "h", special electrical equipment "s".

Hose Reel Irrigation-aquago 40mm

Wide range of model selection from 65 to 90 series.The most precise irrigation, the remarkable energy saving and 100% well-distributed water jet.15 years of service life for the basic unit and ten years' service life for PE pipe.Simple assembling, easy handling and safe operation.Efficient water saving, the water-saving rate can be over 75%.

40Mm Hose Reel Irrigation,40Mm Pe Pipe Length,Small Hose Reel Irrigation,Hose Reel Irrigation

Shandong H.T-BAUER Water and Agricultural Machinery & Engineering Co., Ltd. , https://www.ht-bauer.com