First of all, when the transformer and the low-voltage distr

 

 

 

1, dry type transformer temperature control system dry type transformer safe operation and service life, largely depends on the safety and reliability of the transformer winding insulation. The insulation damage caused by the winding temperature exceeding the insulation tolerance temperature is one of the main reasons that the transformer can not work normally, so it is very important to monitor the operating temperature of the transformer and to control its alarm.

 

 

 

2, dry transformer protection according to the use of environmental characteristics and protection requirements, dry transformer can choose different shell. IP23 protective shell is usually used to prevent solid foreign bodies with diameter greater than 12mm and small animals such as rats, snakes, cats, finches and so on from entering and causing malignant faults such as short circuit and power failure, so as to provide a safety barrier for live parts. If the transformer is to be installed outdoors, the IP23 protective enclosure can be selected. In addition to the above IP20 protective function, it can also prevent water droplets within 60° of the vertical line from entering. But the IP23 shell will reduce the cooling capacity of the transformer, and attention should be paid to the reduction of its operating capacity when choosing.

 

 

 

3. The cooling method of dry transformer is divided into natural air cooling (AN) and forced air cooling (AF). In the case of natural air cooling, the transformer can run continuously for a long time under the rated capacity. Forced air cooling, transformer output capacity can be increased by 50%. Suitable for intermittent overload operation, or emergency overload operation; Due to the large increase of load loss and impedance voltage during overload, it is in non-economic operation state, so it should not be kept in continuous overload operation for a long time.

 

 

 

4. The overload capacity of the dry transformer is related to the ambient temperature, the load before the overload (initial load), the insulation heat dissipation of the transformer and the heating time constant, etc. If necessary, you can ask the manufacturer for the dry overload curve. At present, China's annual output of resin insulated dry-type transformers has reached 10000MVA, becoming one of the countries with the largest sales of dry-type transformers in the world.

 

 

 

With the popularization and application of SC(B)9 series with low noise (the noise of distribution transformers below 2500kVA has been controlled within 50dB) and energy saving (the no-load loss can be reduced by 25%), the performance index and manufacturing technology of dry-type transformers in China have reached the world advanced level.

 

 

 

 

 

With the popularization and application of dry-type transformers, its production and manufacturing technology has also gained considerable development. It can be predicted that the dry-type transformers will get further development in the following aspects in the future.

 

 

 

(1) energy saving and low noise: with the introduction of new low-consumption silicon steel sheet, foil winding structure, ladder core joint, environmental protection requirements, noise research, as well as new materials, new processes and new technologies such as computer optimization design, will make the future dry transformer more energy saving and more quiet.

 

 

 

(2) high reliability: improve product quality and reliability, will be people's unremitting pursuit.

 

 

 

(3) environmental protection characteristics certification: on the basis of the European standard HD464, to carry out the research and certification of the dry type transformer's climate resistance (C0, C1, C2), environmental resistance (E0, E1, E2) and fire resistance (F0, F1, F2) characteristics.

 

 

 

(4) capacity: from 50 ~ 2500 kva distribution transformer dry type transformer, to 10000 ~ 20000 kva / 35 kv power transformer is extended, as the city power load increasing, the city of substation network area is more and more into the city, residential quarters, large load centers such as factories and mines, 35 kv large area power supply power transformer center will receive a wide range of applications.

 

 

 

(5) multi-functional combination: from a single transformer to a multi-functional combined transformer development with air cooling, protective shell, temperature computer interface, zero-sequence transformer, power metering, closed bus and side outlet.

 

 

 

(6) Multi-field development: from distribution transformers to power plant transformers, excitation transformers, subway traction rectifier transformers, high-current furnace transformers, nuclear power plants, Marine transformers and oil production platforms and other special transformers and multi-purpose fields.

 

 

 

 

 

 

 

Among them, the dry traction transformer used in urban subway and rail transit has three grades of voltage of 10, 20 and 35kV, and capacity of 800, 2500 and 3300kVA. In order to reduce harmonic pollution, it has developed from 12 pulse rectifier to 24 pulse rectifier. The exciting transformer of the world's largest 84000KW generator in the Yangtze Three Gorges has been successfully developed by Shunte Factory and passed the national acceptance.

 

 

 

It can be predicted that the distribution transformer of the 21st century will belong to the resin insulated dry type transformer with superior performance, low noise and energy saving.

 

 

 

Technical parameters of dry-type transformer

 

 

 

1, use frequency: 50/60Hz;

 

 

 

2, no load current: < 4%;

 

 

 

3, compressive strength: 20O0V/min without breakdown; Test instrument: YZ1802 pressure test instrument (20mA);

 

 

 

4. Insulation grade: F (special grade can be customized);

 

 

 

5, insulation resistance: ≥2M ohm test instrument: ZC25B - 4 type megohmmeter < 1000 V);

 

 

 

6, connection mode: Y/Y, △ / Y0, YO /△, autocoupling type (optional);

 

 

 

7, coil allowable temperature rise: I00K;

 

 

 

8, heat dissipation mode: natural air cooling or temperature control automatic heat dissipation;

 

 

 

9, noise coefficient: ≤30dB working environment O-4O ℃, relative humidity < 80% altitude: not more than 2500 meters. Avoid exposure to rain, humidity, high temperature, heat or direct sunlight. The distance between the heat dissipation vents and the surrounding objects should be no less than 40cm. Prevent working in corrosive liquid, or gas, dust, conductive fiber or metal fine chip more places. Prevent working in vibration or electromagnetic interference. Avoid long-term upside-down storage and transportation, can not be subjected to strong impact.

 

 

 

Wiring mode of dry transformer

 

 

 

1. The "input" and "output" terminals of the short transformer are tested with a megohmmeter for insulation resistance between them and the ground wire. When measured with 1000V megohmmeter, the resistance value is greater than 2M ohm.

 

 

 

2, transformer input and output power line section wiring should meet the current value size requirements; The current density of 2-2.5A/min2 is suitable.

 

 

 

3. The input and output three-phase power lines shall be connected with A phase, B phase and C phase respectively according to the color yellow, green and red of the bus of the transformer terminal board. The neutral zero line shall be connected with the neutral zero line of the transformer compressor, and the ground wire shall be connected with the transformer shell (if the transformer has A case, it shall be connected with the ground mark of the box). Check the input and output lines to make sure they are correct.

 

4. Power on without load first, observe and test the input and output voltage to meet the requirements. At the same time, observe whether there is abnormal sound, fire, smell and other abnormal phenomena inside the machine. If there is abnormal, please disconnect the input power immediately.

 

 

 

5. When the no-load test is completed and normal, the load can be connected. The overload capacity of the dry-type transformer is related to the ambient temperature, the load condition before overload (initial load), the insulation heat dissipation of the transformer and the heating time constant, etc. If necessary, you can ask the manufacturer for the dry-change overload curve.

 

How to take advantage of its overload capacity?

 

 

 

 

 

(1) choose to calculate the capacity of the transformer can be appropriately reduced: fully consider the possibility of some steel rolling, welding and other equipment short-term impact overload - try to use the strong overload capacity of the dry transformer to reduce the capacity of the transformer; For some places with uneven load, such as residential areas for night lighting, cultural and entertainment facilities and shopping malls for air conditioning and daytime lighting, the overload capacity can be fully utilized to appropriately reduce the transformer capacity, so that the main operation time is full load or short overload.

 

 

 

(2) can reduce the reserve capacity or number of sets: in some places, the reserve coefficient of the transformer is higher, so that the selected transformer capacity is large and the number of sets is many. The overload capacity of the dry transformer can be compressed when considering its reserve capacity. It may also be reduced when determining the number of standby units. When the transformer is in overload operation, we must pay attention to monitoring its operating temperature: if the temperature rises to 155℃(there is an alarm), load reduction measures should be taken (minus some secondary loads) to ensure the safety of power supply for the main load.