How to install and debug dry-type transformers

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Dry-type transformer refers to a power transformer in which the core and windings are not immersed in oil, the coil and core are cast together, and are naturally cooled or air-cooled.

Dry-type transformer refers to a power transformer in which the core and windings are not immersed in oil, the coil and core are cast together, and are naturally cooled or air-cooled.
It has the advantages of high safety performance, simple maintenance, small size and few accessories. It is widely used in power transmission and transformation systems in factory workshops, high-rise buildings, commercial centers, airports, docks, subways, oil platforms and other places, and can be used together with switch cabinets to form compact complete sets of substations.
Today, we will mainly introduce the installation and debugging steps of dry-type transformers.

1. Pre-installation inspection

Before installing a dry-type transformer, the integrity of its packaging should be checked to eliminate the possibility of foreign matter or water intrusion.

After unpacking, first check whether the transformer nameplate data meets the design requirements, whether the factory documents are complete, whether the transformer is intact, whether there are signs of external damage, whether parts have been displaced and damaged, whether electrical supports or connecting wires are damaged, and finally check. Check for damage and shortage of spare parts.

2. Transformer installation

First, check the foundation of the transformer to see if the embedded steel plate is level. There should be no holes under the steel plate to ensure that the foundation of the transformer has good seismic resistance and sound-absorbing properties. Otherwise, the noise of the installed transformer will increase.

Then, use the rolling bar to move the transformer to the installation position, remove the rolling bar, and accurately adjust the transformer to the designed position. The installation level error meets the design requirements. Finally, four pieces of short channel steel are welded on the four corners of the embedded steel plate close to the transformer base to prevent the transformer from moving during use.

3. Transformer wiring

When wiring, the minimum distance between live objects and between live bodies and ground should be ensured, especially the distance from the cable to the high-voltage coil. The high-current low-voltage busbar should be supported independently and cannot be directly connected to the transformer terminals to cause excessive mechanical tension and torque. When the current is greater than 1000A (such as the 2000A low-voltage busbar used in this project), the busbar and transformer There must be a soft connection between the terminals to compensate for the thermal expansion and contraction of the conductor and to isolate the vibration of the busbar and transformer.

The electrical connections at each wiring joint must maintain the necessary contact pressure, elastic components (such as disc-shaped plastic rings or spring washers) should be used, and a torque wrench should be used when tightening the connecting bolts.

4. Transformer grounding

The grounding point of the transformer is on the base of the low-voltage side, and leads to a special grounding bolt marked with a grounding center. The grounding of the transformer must be reliably connected to the protective grounding system through this point. When the transformer has a shell, the shell 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. Inspection before operation of transformer

Check whether all fasteners are loose, whether the electrical connections are correct and reliable, whether the insulation distance between live parts and between live parts and ground meets the regulations, there should be no foreign matter near the transformer, and the coil surface should be cleaned.

6. Debugging before operation of transformer

(1) 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.

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

(3) The test voltage of the withstand voltage test should comply with the regulations. When doing the low-voltage withstand voltage test, the temperature sensor TP100 should be taken out. After the test, the sensor should be returned to its place in time.

(4) When the transformer is equipped with a fan, the fan should be powered on and ensure its normal operation.

7. Trial operation

After the transformer has been carefully inspected before being put into operation, it can be powered on for trial operation. During the trial operation, special attention must be paid to checking the following points. Are there any abnormal sounds, noises and vibrations? Is there any abnormal smell such as burnt smell? Is there any discoloration caused by local overheating? Is ventilation good?

8. Later maintenance

Dry-type transformers have an open structure and are susceptible to moisture. They should be operated in an environment with a relative humidity of less than 70% to achieve higher reliability. Avoid long-term outage to avoid moisture. When it is seriously affected by moisture, it should be stopped and returned to the factory for repair.

The above are the installation and debugging steps of dry-type transformers. It is recommended to choose regular, reliable and powerful transformer merchants to purchase transformer products, so that you can get more comprehensive installation and after-sales services.

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