The Distribution transformer is one of the important equipments in the power supply and distribution system of industrial and mining enterprises and civil buildings. It reduces the network voltage of 10(6)kV or 35kV to the 230/400V bus voltage used by users. These products are suitable for AC 50 (60) Hz, three-phase maximum rated capacity 2500kVA (single-phase maximum rated capacity 833kVA, generally not recommended for single-phase transformers), can be used indoors (outside), capacity is 315kVA and below Can be installed on the pole, the ambient temperature is not higher than 40 ° C, not lower than -25 ° C, the highest daily average temperature is 30 ° C, the highest annual average temperature is 20 ° C, the relative humidity is not more than 90% (ambient temperature 25 ° C), altitude Not more than 1000m. If it does not conform to the above conditions of use, the appropriate quota adjustment shall be made in accordance with the relevant provisions of GB6450-86.
Performance characteristics
a. Oil-immersed Transformer low-voltage windings, except for small-capacity copper conductors, generally adopt a cylindrical structure with copper foil winding; high-voltage windings adopt multi-layer cylindrical structure to balance the ampules of the windings and magnetic flux leakage. Small, high mechanical strength, strong resistance to short circuit.
b. The core and the winding are respectively tightened. The fastening parts such as the height and low-voltage leads of the machine are equipped with self-locking locknuts. They adopt a non-suspension structure and can withstand the shock of transportation.
c. The coil and the iron core are vacuum dried, and the transformer oil adopts a vacuum oil filtering and oil filling process to minimize the moisture inside the transformer.
d. The fuel tank adopts a corrugated sheet, which has a breathing function to compensate for the volume change of the oil caused by the temperature change, so the product does not have an oil storage cabinet, which obviously reduces the height of the transformer.
e. Since the corrugated sheet replaces the oil conservator, the transformer oil is isolated from the outside, thus effectively preventing the entry of oxygen and moisture and causing a decrease in insulation performance.
f. According to the above five performances, it is guaranteed that the oil-immersed transformer does not need to change oil in normal operation, which greatly reduces the maintenance cost of the transformer and prolongs the service life of the transformer.
Selection point
Load nature
1) When there are a large number of primary or secondary loads, two or more transformers should be installed. When any one of the transformers is disconnected, the capacity of the remaining transformers can meet the primary and secondary loads. First, the secondary load is as concentrated as possible and should not be too dispersed.
2) When the seasonal load capacity is large, a special transformer should be installed. Such as air conditioning refrigerator load in large civil buildings, electric heating load for heating, etc.
3) When the concentrated load is large, a special transformer should be installed. Such as large heating equipment, large X-ray machines, electric arc furnaces, etc.
4) When the lighting load is large or the power and lighting use the shared transformer seriously affects the lighting quality and the life of the lamp, a special transformer for lighting can be provided. In general, power and lighting share a transformer.
Use environment
Under normal medium conditions, oil-immersed transformers or dry-type transformers, such as industrial and mining enterprises, agricultural independent or auxiliary substations, and district independent substations, can be used. The available transformers are S8, S9, S10, SC(B)9, SC(B)10, etc.
Temperature environment
1 maintain long-term stability at 220 ° C
2 can withstand short-term operation at 350 °C
3 Maintain stable performance over a wide temperature and humidity range
4 at 250 ° C, will not melt, flow and combustion
5 at 750 ° C, will not release toxic or corrosive gases
Electricity load
1) The capacity of the distribution transformer should be integrated with the facility capacity of various electrical equipment to calculate the calculation load (generally without the fire load). The apparent capacity after compensation is the basis for selecting the capacity and number of transformers. Generally, the load factor of the transformer is about 85%. This method is simpler and can be used for estimating capacity.
2) GB/T17468-1998 "Guidelines for Selection of Power Transformers", the recommended capacity selection of distribution transformers shall be in accordance with GB/T15164-94 "Guidelines for Oil-immersed Power Transformers" or GB/T17211-1998 "Dry" Power Transformer Load Guidelines" and calculate the load to determine its capacity. The above two guidelines provide a computer program and a normal cycle load map to determine the distribution transformer capacity.
Installation points
Distribution transformers are an important component of substations, and oil-immersed transformers are typically installed in separate transformer rooms.
Relying on oil as cooling medium, such as oil immersion from cold, oil immersion air cooling, oil immersion water cooling and forced oil circulation. The main transformer of the general booster station is oil-immersed, with a ratio of 20KV/500KV or 20KV/220KV. The general power plant is used to drive the load with its own (such as coal mill, induced draft fan, blower, circulating water pump, etc.). The factory transformer is also an oil-immersed transformer, and its transformation ratio is 20KV/6KV.
Oil-immersed transformers are fully oil-filled. The corrugated tank housing is self-elastic to accommodate oil expansion and is a permanently sealed fuel tank. Oil-immersed transformers have been widely used in various power distribution equipment.
Preliminary preparation
1. Working hours quota: (According to the national quota standard) The total working day required for the main body installation is 21 working days. The work includes: unpacking inspection, body position, body inspection, casing, oil pillow and radiator cleaning, oil column experiment, accessory installation, horn and wheel stop production and installation, supplementary column and overall installation Seal test, grounding, touch up, etc. Whether the transformer needs to be dried during the installation process, after inspection and judgment, it needs to be dried. After drying with iron loss drying method, the working day is 20 days, and the oil filtering required working day is 3.38 working days/ton. The working days required for commissioning must be calculated separately.
2, installation site layout: power transformer overhaul and assembly work is best carried out in the maintenance room. If there is no maintenance room, you need to choose a temporary installation site. It is best to choose the transformer near the base station to make the transformer in place, or you can install it on the base station. There should be tents on the outdoor site. The temporary installation site must be convenient to transport, the road is flat, and there is sufficient width. The ground should be solid, flat and dry, away from the smoke window and water tower, and the distance from the nearby buildings should meet the fire protection requirements.
3. Designated safety measures: 1 Prevent accidents such as personal electric shock and falling. 2 Prevent insulation from overheating. 3 Prevent fires. 4 Prevent something from falling into the tank. 5 Prevent attachment damage. 6 Prevent the transformer from tipping over.
4. Develop technical measures: 1 Prevent the transformer core from being damp. 2 How to ensure that the connection parts are in good contact. 3 All parts should be sealed well without oil leakage. 4 How to ensure transformer insulation and oil insulation.
5, the basic procedures for installation work: 1 preparation work (tools, materials, equipment, drawings) 2 insulation inspection and judgment (mainly coils and iron core) 3 accessories inspection (should be complete, intact) 4 hanging core inspection (prevent Moisture absorption and tools, parts, etc. fall into the fuel tank) 5 accessories installation (appearance inspection, insulation measurement and strict test) 6 end work 7 handover test 8 trial operation
6, the organization of the division of labor: 1 installation of the chief commander and technical person in charge 2 security staff 3 oil filter group 4 hoisting and transport personnel 5 test personnel 6 installers.
7, the requirements of the transformer room: 1 level 1 fire 2 ventilation is good 3 safety distance should be enough 4 base station should be secure 5 lifting equipment should be intact.
8, tool material preparation:
(1) Installation of tools (such as vacuum pumps, oil pumps, oil tanks, compressed air machines, oil filters, electric welders, row light transformers, valves, various wrenches, etc.)
(2) Test instruments (such as shaker, medium loss angle detector, step-up transformer, voltage regulator, ammeter, voltmeter, power meter, thermometer, etc.)
(3) Cranes (such as cranes, hangers, lifting beams, winches, wire ropes, pulleys, chain cranes, etc.)
(4) Insulating materials (such as insulating oil, cardboard, cloth tape, electric board insulation paint, etc.)
(5) Sealing materials (such as right rubber gasket, asbestos rope, steel bottom, shellac paint, nylon rope, etc.)
(6) Bonding materials (such as epoxy resin glue, glue, cement, mortar, etc.)
(7) Cleaning materials (such as white cloth, alcohol, gasoline, etc.)
(8) Other materials (such as asbestos board, square wood, wire, steel pipe, oil filter paper, petroleum jelly, enamel, etc.)
9, transformer external inspection:
1 content without mechanical damage
2 box cap bolts are in good condition
3 pad seals are good
4 casing surface without defects
5 no oil leakage and oil leakage
6 no rust, complete paint
7 accessories are intact
8 The wheel track is consistent with the base rail gauge temperature.
Claim
1. When the transformer is transported over a long distance, it will be subjected to large vibrations and the body inspection is required. The body inspection of the transformer is divided into a suspension core and a suspension cover. Regardless of the sling or the sling, the contents of the inspection are consistent. The core inspection should be completed within one working day to speed up the inspection process.
2. Take the sling core inspection as an example: (1) The transformer sling core should be carried out indoors. If there is a tent outside, it is forbidden to hang the core in the bad weather such as rain, snow, fog and sand. (2) The temperature of the winter core should not be lower than zero, otherwise the temperature of the transformer should be raised so that the core temperature is higher than the ambient temperature by 10 °C. (3) The shorter the iron core is exposed to the air, the better, and the relative humidity should not exceed 16 hours when it is 65%. The relative humidity should not exceed 12 hours at 25%, and the calculation time starts from the time of oil discharge to the time of oil injection. (4) When the relative humidity of the weather exceeds 75%, the core inspection is not allowed. (5) During the inspection of the core, special care should be taken to prevent parts and tools from falling into the tank.
