Dry type transformer refers to a transformer in which the iron core and winding are not immersed in insulating oil. Suitable for intermittent overload operation or emergency overload operation; Due to the significant increase in load loss and impedance voltage during overload, it is in a non economic operating state and should not be subjected to long-term continuous overload operation.

Dry type transformers should be aware of the following issues during operation:

1. Is the insulation resistance of the iron core to ground low?

Mainly due to the high humidity of the ambient air, the dry-type transformer is affected by moisture, resulting in low insulation resistance. Solution: Place an iodine tungsten lamp under the low voltage coil and bake continuously for 12 hours. As long as the insulation resistance of the iron core and high and low voltage coils is low due to moisture, the insulation resistance value will correspondingly increase.

2. How to solve the problem of zero insulation resistance between the iron core and the ground?

Explain the solid connection between metals (possibly due to burrs, metal wires, etc., being painted onto the iron core, with both ends overlapping between the iron core and the clamp; insulation damage on the foot causing the iron core to be connected to the foot; metal objects falling into the low-voltage coil causing the pull plate to be connected to the iron core;). Solution: Use lead wire to poke down the channel between the iron core stages of the low-voltage coil. After confirming that there are no foreign objects, check the insulation condition of the feet. If it still cannot be solved. The following methods can be adopted: connect the ground wire end of the welding machine to the grounding plate, click the foot with the welding rod (current of about 250A), and solve the problem with just one click.

3. What should be noted during on-site power transmission?

Generally, the power supply bureau sends electricity 5 times, and there are also 3 times. Before sending electricity, check the tightening of bolts and whether there are any metal foreign objects on the iron core; Whether the insulation distance meets the power transmission standards; Whether the electrical functions are operating normally; Is the connection correct; Check if the insulation of each component meets the power transmission standards; Check for condensation on the body; Check for any loopholes in the casing that may allow small animals to enter (especially at the cable entry point); Is there any discharge sound during power transmission.

4. What does it mean when the shell and the floor iron plate discharge during power transmission shock?

The conductivity between the aluminum alloy plates of the shell is not good enough, which belongs to poor grounding. Method: Use a 2500M Ω shaking table to break down the insulation of the board or scrape off the paint film of each connection part of the shell and connect it to the ground with copper wire.

5. Why is there a discharge sound during the handover test for power frequency withstand voltage?

There are several possibilities. The pull plate can be positioned at the tightening point of the clamp to discharge electricity. A gun can be used to strike here to ensure good conductivity between the pull plate and the clamp, and the problem can be solved; Pad crawling, especially in high-voltage products (35kV), has caused this phenomenon. Strengthen the insulation treatment of the pad; High voltage cables that are loosely connected to connection points or insulated close to tap boards or corner connectors can also produce discharge sounds. Increase the insulation distance and tighten the bolts again to solve the problem. Check if there are dust particles on the inner wall of the high-voltage coil. Due to the moisture absorption of the particles, insulation may decrease and discharge may occur.