You just bought a high-quality transformer bushing and followed all the standards. But if the installation goes wrong, the bushing will not last long. Many field failures happen not because the part is bad, but because of small mistakes during the setup.
One of the biggest issues is simple dirt. When you take the bushing out of the crate, you might see dust or grease on the insulator. If you leave these marks there, they create a path for electricity to "leak" over the surface. This leads to tracking or a flashover later.
Always wipe down the porcelain or resin with the right cleaning agent before you put it in. Do not touch the clean parts with oily gloves.
People often tighten the mounting bolts by "feeling." This is a mistake. If the bolts are too loose, the seal won't hold and oil will leak out. If you tighten them too much, you can crack the flange or put too much stress on the porcelain.
You must use a torque wrench and follow the specific numbers in the manual. Also, tighten the bolts in a "star pattern" so the pressure stays even across the gasket.
It is tempting to reuse an old gasket if it looks "okay." Never do this. Once a gasket has been squeezed for years, it loses its ability to spring back and seal.
Using a new O-ring or gasket is a cheap way to prevent a very expensive oil leak. Make sure the gasket is sitting flat in its groove. If it gets pinched during installation, it will fail within a few months.
Bushings are heavy, so people use cranes or hoists to move them. If the bushing bumps against the side of the transformer tank, it might not look broken. However, this can cause tiny "micro-cracks" inside the material.
You cannot see these with your eyes, but once the transformer gets hot and starts vibrating, those cracks will grow. Always use soft slings and move the unit slowly.
Inside the transformer, the lead or cable must connect perfectly to the bottom of the bushing. If this connection is loose, it creates a "hot spot." The heat will eventually damage the insulation oil and the bushing itself.
Double-check that the draw-lead or bottom terminal is locked in place tightly. A simple check now saves you from a massive failure next year.
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