Transformer clamps need to meet various performance requirements to adapt to the working environment. Mechanical strength is the primary requirement. They need to have sufficient compressive, tensile, and anti-deformation capabilities, and can withstand the weight of the transformer body and the axial force during short circuits for a long time. Rust and corrosion resistance is crucial. Because the transformer operating environment may be humid or have corrosive substances, clamps need to resist rust through surface treatment and other methods to extend their service life. In addition, they need to have a certain assembly adaptability, with high dimensional accuracy to ensure precise matching with the iron core, accessories, and other components, avoiding the impact of installation gaps on overall stability.
Fault Detection and Maintenance Skills of Transformer Clamps
The fault detection of transformer clamps needs to be based on an in-depth understanding of their operating status, and daily maintenance must follow refined operating specifications. In terms of bolt tightening inspection, bolts in different positions have different torque requirements: for the connecting bolts between the clamp and the iron core column, when the diameter is M12, the standard torque is 35-40N·m, which needs to be detected with a torque wrench with scales, at least once a quarter. If the torque deviation exceeds 10%, it needs to be adjusted in time. For the tie rods of large transformer clamps, their pre-tightening force is usually required to reach 60%-70% of the material's yield strength, which can be verified by measuring the elongation of the tie rods. For example, the standard pre-tightening elongation of a 45# steel tie rod with a diameter of 20mm is 0.15-0.2mm. Exceeding this range indicates a risk of loosening.
The treatment of rust on the clamp surface needs to be carried out according to the degree: when the rust area is less than 5% and only surface rust, fine sandpaper (with a grit size of 800 or more) can be used for gentle grinding first. After removing the rust, clean the surface with absolute ethanol, and then apply anti-rust paint of the same type as the original coating, with a dry film thickness of not less than 30μm. If the rust depth exceeds 0.1mm and obvious rust pits are formed, it is necessary to first use an angle grinder (equipped with a wire wheel) for thorough rust removal. After exposing the metallic luster, spray a layer of epoxy zinc-rich primer (dry film thickness 50μm). After 24 hours of curing, apply the topcoat to ensure that the rusted part is completely repaired.
When the transformer has abnormal vibration (vibration acceleration exceeding 0.1g) or noise (sound pressure level exceeding 65dB) during operation, the steps to check the clamp are as follows: first, check whether the insulating pads between the clamp and the iron core are worn or displaced. If the thickness of the pads is uneven, it will cause unbalanced stress on the iron core; second, measure the temperature of each part of the clamp. If a certain area is 5℃ higher than the surrounding area, there may be partial discharge between the clamp and the windings, resulting in poor contact; finally, check whether there are cracks in the welding parts of the clamp. Magnetic particle testing can be used. For large clamps, focus on testing the corners of the welds, which are stress concentration points and prone to cracks due to vibration.
For old transformer clamps that have been in operation for more than 15 years, mechanical strength testing is essential. Ultrasonic flaw detectors can be used to detect fatigue cracks in the steel. At the same time, samples of similar materials are taken for tensile tests. If the yield strength drops by more than 20%, it indicates that the clamp has aging phenomenon, and replacement is recommended. When replacing, attention should be paid to the size matching between the new clamp and the old iron core and windings. On-site mapping is necessary if necessary to ensure installation accuracy.
