Ⅰ. Characteristics of dry-type transformers

Compared with oil-type transformers, dry-type transformers do not have fire, explosion, pollution and other problems because there is no oil. Compare with the china oil type transformer, so electrical specifications and regulations do not require dry-type transformers to be placed in a separate room.

1. Temperature control system of dry-type transformer. The safe operation and service life of dry-type transformers largely depend on the safety and reliability of the transformer winding insulation.

It is one of the main reasons that the transformer can not work normally when the winding temperature exceeds the insulation withstand temperature and the insulation is damaged. Therefore, the monitoring and alarm control of the operating temperature of the dry-type transformer is very important.

2. The protection method of dry-type transformer. According to the characteristics of the use environment and protection requirements, dry-type transformers can choose different enclosures. IP23 protective casing is usually used, which can prevent solid foreign objects larger than 12mm in diameter and small animals such as mice, snakes, cats, and sparrows from entering, causing vicious failures such as short circuit and power failure, and providing a safety barrier for live parts.

3. Cooling method of dry-type transformer. Dry-type transformer cooling methods are divided into natural air cooling (AN) and forced air cooling (AF). Under natural air cooling, the transformer can run continuously for a long time under the rated capacity.

4. The overload capacity of dry-type transformers. The overload capacity of the dry-type transformer is related to the ambient temperature, the load before overload, the insulation and heat dissipation of the transformer and the heating time constant. If necessary, the overload curve of the dry-type transformer can be obtained from the manufacturer.

Ⅱ. Installation and debugging of dry-type transformers

1. Unpack inspection before installation

Check whether the packaging is in good condition. After unpacking the transformer, check whether the data on the nameplate of the transformer meets the design requirements, whether the factory documents are complete, whether the transformer is in good condition, whether there is any sign of external damage, whether the parts are displaced or damaged, whether the electrical support or connecting line is not. If there is damage, finally check for damage and shortage of spare parts.

2. Transformer installation

First, check whether the embedded steel plate of the dry type transformer types is level. There should be no cavities under the steel plate to ensure that the foundation of the transformer has good shock resistance and sound absorption performance, otherwise the noise of the transformer after installation will increase.

Then, use the roller to move the transformer to the installation position, remove the roller, and accurately adjust the transformer to the design position. The installation level error meets the design requirements. Finally, four short channel steels are welded on the four corners of the transformer base, that is, the embedded steel plate, so that the transformer does not move during use.

3. Transformer wiring

When wiring, ensure the minimum distance between charged bodies and between charged bodies and the ground, especially the distance from the cable to the high-voltage coil. The high-current low-voltage busbar should be supported separately and cannot be connected to the dry-type transformer terminals, which will cause excessive mechanical tension and torque.

Necessary contact pressure must be maintained at the electrical connection of each wiring, elastic elements should be used, and a torque wrench should be used when tightening the connection bolts.

4. Transformer grounding

The grounding point of the transformer is on the base of the low-voltage side, and a special grounding bolt is drawn out, which is marked with a grounding mark. The grounding of the transformer must be reliably connected to the protective grounding system through this point.

When the transformer has an enclosure, the enclosure should be reliably connected to the grounding system. When the low-voltage side adopts a three-phase four-wire system, the neutral wire should be reliably connected to the grounding system.

5. Check the transformer before operation

Check whether all fasteners are loose, whether the electrical connection is correct and reliable, whether the insulation distance between the charged body and the charged body to the ground meets the regulations, there should be no foreign objects near the transformer, and the surface of the coil should be cleaned.

6. Debugging before transformer operation

Check the transformation ratio and connection group of the transformer, measure the DC resistance of the high and low voltage windings, and compare the results with the factory test data provided by the manufacturer.

Check the insulation resistance between the coils and the coil to the ground. If the insulation resistance of some transformers is significantly lower than the factory measurement data, it indicates that the transformer is damp. When the insulation resistance is lower than 1000Ω/V (operating voltage), the transformer must be dried.

When the transformer is equipped with a fan, the fan should be powered on and ensured that it is functioning properly.

7. Trial operation

After the transformer has been carefully checked before it is put into operation, it can be powered on for trial operation. During commissioning, special care must be taken to check the following points. Abnormal sound, noise and vibration. There is no abnormal smell such as burnt odor. Is there any discoloration caused by local overheating of the dry-type transformer. Whether the ventilation is good.