Power transformer is based on the principle of electromagnetic induction, mutual inductance based on the phenomenon of a certain voltage AC power into different voltage AC power equipment, according to the different cooling medium can be divided into dry-type transformers and oil-immersed transformers.
Power transformer is composed of iron core or iron yoke composed of a complete closed magnetic circuit, made of insulated copper or aluminum wire coil, the formation of the original transformer, secondary coil. In addition to small-capacity dry-type transformers, most transformers are oil-immersed natural cooling, insulated oil from the coil between the insulation and cooling effect. Transformer in the insulating oil flash point of about 135 ℃, easy to evaporate combustion, mixed with the air to form an explosive mixture. Insulation pads and brackets inside the transformer are mostly made of cardboard, cotton yarn, cloth, wood and other organic combustible materials, such as 1000kVA transformer with about 0.012m³ of wood, paper 40kg, installed insulating oil about 1t. Therefore, once the transformer internal overload or short circuit, combustible materials and oil will be due to high temperature or spark, arc and decomposition, expansion and gasification, so that the transformer internal pressure surge. At this time, can cause the transformer shell explosion, a large number of insulating oil jet burning, burning oil flow will further expand the risk of fire.
Safety settings for power transformers
According to the "Building Design Fire Code" requirements, power transformer safety settings should meet the following requirements:
1, oil-immersed transformer room, high-voltage power distribution device room fire rating should not be lower than two, other fire safety design should be "thermal power plant and substation design fire safety regulations" GB 50229 and other relevant provisions of the implementation of the provisions.
2, oil-immersed power transformers, filled with fuel oil high-voltage capacitors and multi-oil switches and other buildings should be built independently. When there are difficulties can be adjacent to the layout of civil buildings, but should be separated by a firewall, and should not be close to the staff-intensive places.
3, change, distribution should not be set in the A, B plant or adjacent to the construction, and should not be set in the explosive gas, dust environment, dangerous areas. For the A and B plant dedicated 10kV and below the change, distribution, when using the doors and windows without the opening of the firewall, can be a side of the adjacent construction, and should comply with the existing national standard "explosion hazard environment, electrical design specifications" GB 50058 and other relevant provisions of the specification. Class B plant power distribution must be in the firewall when the window should be set to seal a fixed level fire window.
4, multi-storey civil construction and substation fire spacing, should be consistent with the "building design fire regulations" requirement. 10kV below the box-type transformers and buildings of the fire spacing should not be less than 3.00m.
5, oil-immersed power transformers, fuel oil filled with high-voltage capacitors and multi-oil switches and other space conditions must be arranged in the civil construction, should not be arranged in the staff-intensive places on the next layer, the next layer or adjacent , And shall comply with the following provisions:
(1) Transformer room should be located in the first floor or underground layer by the external wall.
(2) the door of the transformer room should be directly through the outdoor or through the safety outlet; outside the wall openings should be set above the width of not less than 1.0m of non-flammable fire eaves or height of not less than 1.20m window sill wall;
(3) between the transformer room and other parts should be used fire resistance of not less than 2.00h incombustible wall and 1.50h non-flammable floor separated. In the partition walls and floors should not open the hole, when the doors must be opened in the doors and windows, should be set up a fire doors and windows;
(4) between the transformer room, transformer room and power distribution room, should be used fire resistance of not less than 2.00h non-burning body wall separated;
(5) oil-immersed power transformers, multi-oil switch room, high-voltage capacitor room, should be set to prevent oil flow facilities. Oil-immersed power transformer should be set below the storage of all the oil transformer oil storage facilities;
(6) should be set fire alarm device;
(7) Fire extinguishing facilities should be provided in accordance with the capacity of the oil-immersed transformers and the size of the building. According to the "Fire Code for Architectural Design", a single oil and water transformer with a capacity of 40MVA and above, a single oil refinery with a capacity of 90MVA and above, a single transformer substation with a capacity of 125MVA and above, Set in high-rise civil buildings, fueled high-voltage capacitors and multi-oil switch room should use water spray fire extinguishing system. In the room of the oil-immersed transformers, fueled high-voltage capacitors and multi-oil switch room, can be used water mist fire extinguishing system.
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