Structure Characteristics of dry-type transformer

1. The core is made of high quality cold-rolled grain-oriented silicon steel sheet. 2. Winding Type (1) winding type (2) epoxy casting with quartz sand filling (3) glass fiber reinforced Epoxy Casting (i.e. thin insulation structure)(4) multi-strand glass fiber impregnated epoxy winding type (generally used 3, because it can effectively prevent casting resin cracking and improve the reliability of equipment)(1) high voltage winding, generally adopts multi-layer cylinder or multi-layer segmented structure. (2) low-voltage winding generally adopts layer or foil structure I. Is a commonly used form, its body and the atmosphere of direct contact, suitable for relatively dry and clean indoor, (ambient temperature 20 degrees, relative humidity should not exceed 85%) , generally have air self-cooling and air cooling two cooling methods. 2. Closed. The device is enclosed in an enclosure and does not come into direct contact with the atmosphere. Due to sealing, poor heat dissipation. Mainly used for mine it belongs to explosion-proof type. The main insulation is cast with epoxy or other resin, which has a simple structure. It is small in size. Suitable for small capacity transformer. Second, the characteristics and structure of dry-type transformer, relative to oil-type transformer, dry-type transformer because there is no oil, there is no fire, explosion, pollution and other issues, so electrical norms, regulations, etc. Do not require dry-type transformer placed in a separate room. In particular, the new series, loss and noise reduced to a new level, more for the transformer and low-voltage panel placed in the same distribution room to create conditions. The temperature control system of the dry-type transformer, the safe operation and service life of the dry-type transformer, to a large extent, depend on the safety and reliability of the winding insulation of the transformer. It is one of the main reasons that the transformer can not work normally when the winding temperature exceeds the insulation tolerance temperature, so it is very important to monitor and control the running speed of the transformer. Protection mode of dry-type transformer, according to the use of environmental characteristics and protection requirements, dry-type transformer can choose different shell. IP23 protective casing is usually selected to prevent solid foreign body with diameter greater than 12mm and small animals such as mouse, snake, cat, bird from entering, causing short-circuit power failure and other malignant faults, providing a safety barrier for live parts. If the transformer is to be installed outdoors, the IP23 protective housing can be used. In addition to the IP20 protective functions mentioned above, the utility model can also prevent the water from dripping in an angle of 60 ° with the vertical line. However, the IP23 shell will reduce the cooling capacity of the transformer, so it is necessary to pay attention to the reduction of its operating capacity when it is selected. Five, dry-type Transformer Cooling, dry-type transformer cooling methods are divided into natural air cooling (AN) and forced air cooling (AF) . When the air is cooled naturally, the transformer can run continuously for a long time under the rated capacity. When forced air cooling, the output capacity of the transformer can be increased by 50% . The utility model is suitable for intermittent overload operation or emergency overload operation, and should not be in continuous overload operation for a long time due to the large increase of load loss and impedance voltage. 6. Overload capacity of dry-type transformers, overload capacity of dry-type transformers is related to ambient temperature, load condition before overload (initial load) , insulation heat dissipation condition of transformers and heating time constant, etc. , the dry-change overload curve can be obtained from the production plant. At present, China's resin insulated dry-type transformer annual output has reached 10000MVA, become the world's dry-type transformer production and sales of one of the largest countries. With the popularization and application of SC (B)9 series with low noise (less than 2500kVA distribution transformer noise control within 50dB) and energy saving (no-load loss reduction up to 25%) , the performance index and manufacture technology of dry-type transformer in our country have reached the advanced level in the world. With the popularization and application of dry-type transformer, its production technology has also made great progress. It can be predicted that the future dry-type transformer will be further developed in the following aspects. 1. Energy saving and low noise: with the introduction of new low consumption silicon steel sheets, foil winding structures, stepped iron core joints, environmental protection requirements, further research on noise, and the introduction of new materials, new processes and new technologies such as computer optimization design, will make the future dry-type transformer more energy-saving, more quiet. 2, high reliability: Improve product quality and reliability, will be people's unremitting pursuit. (1) environmental certification: Based on the European Standard HD464, the research and certification of dry-type transformers'climate resistance (C0, C1, C2) , environmental resistance (E0, E1, E2) and fire resistance (F0, F1, F2) are carried out. 3. Large capacity: from 50 ~ 2500kVA distribution transformer-based dry-type transformer to 10000 ~ 20000kVA/35kV power transformer, with the increase of city power load, more and more substations of city network are going into the load centers such as city center, residential quarter, large-scale factories and mines, etc. . 4. MULTI-FUNCTION COMBINATION: from single transformer to multi-function combination transformer with Air Cooling, protective case, temperature computer interface, zero-sequence transformer, power metering, closed bus and side outlet. 5. Multi-field Development: from distribution transformers, to power station auxiliary transformer, excitation transformer, Metro Traction rectifier transformer, large current furnace transformer, nuclear power station, marine and oil production platform and other special transformers and multi-purpose field development. In order to reduce the harmonic pollution, the dry-type traction transformer used in urban subway and rail transit is developed from 12-pulse rectifier to 24-pulse rectifier, with the voltage of 10,20 and 35 kv and the capacity of 800,2500 and 3300 KVA The world-famous excitation transformer for the world's largest 840000kW generator in Three Gorges has been successfully developed by Suntech and has passed the national acceptance test. It can be predicted that the 21st century distribution transformer will belong to the resin insulated dry-type transformer with superior performance, low noise and energy saving. The overload capacity of dry-type transformers and the overload capacity of dry-type transformers are related to the ambient temperature, the load condition before overload (initial load) , the insulation heat dissipation condition of transformers and the heating time constant, etc. . If necessary, the dry-change overload curve can be obtained from the production plant. How to use its overload capacity? The author puts forward two points for reference: 1. When choosing to calculate the capacity of transformer, it can be reduced properly: taking full account of the possibility of short-term impact overload of some equipment such as steel rolling and welding, making use of the stronger overload capacity of dry-type transformer to reduce its capacity; For some places with non-uniform load, such as residential areas, cultural and entertainment facilities, air-conditioning and daytime-lighting shopping malls, etc. , their overload capacity can be fully utilized and the capacity of transformers can be reduced appropriately, causes its main running time to be at full load or short-term overload. 2, may reduce the standby capacity or the number: In some places, to the transformer's standby Coefficient request is high, causes the project to choose the transformer capacity to be big, the number is many. The overload capacity of dry transformer can be compressed when its spare capacity is considered and reduced when the number of spare units is determined. Transformer in overload operation, must pay attention to monitor its operating temperature: if the temperature rise up to 155 °C (alarm issued) should be taken to load reduction measures (minus some secondary load) to ensure the safety of the main load power supply.