What to Do When You Notice Your Bushing is Leaking Oil

Finding a pool of oil at the base of a transformer bushing is a common sight, but it is never something you should ignore. A leak means two things: valuable insulation oil is getting out, and dangerous moisture is getting in. If you spot oil on your bushing, here is how to handle it step by step.

Find the actual source of the leak 

Oil travels, so where you see the puddle is not always where the leak starts. Wipe the entire bushing clean with a dry cloth, then wait and watch. Check the top terminal, the glass sight window, and the large flange at the bottom where it connects to the transformer. Often, the leak is just a loose bolt at the very top, which is much easier to fix than a broken seal at the bottom.

Look at the speed of the drip 

Not all leaks are emergencies. If the metal just looks "sweaty" or has a damp layer of dust sticking to it, it is a slow seep. You can usually monitor this and fix it during the next scheduled maintenance day.

However, if you see active drops forming and falling, or if the oil level in the sight glass is visibly dropping week by week, you need to shut down the system and fix it immediately.

The danger of low oil inside 

Why is a leak so dangerous? The oil inside a bushing keeps the high voltage from jumping across the internal parts. If the oil level drops too low, the upper section of the internal core becomes exposed to air. This creates a weak spot. Without the oil to cool it down and insulate it, the bushing can catch fire or explode internally without warning.

Never just tighten bolts blindly 

When people see a leak at the base flange, their first reaction is to grab a wrench and pull as hard as they can on the bolts. This can make things worse.

If the gasket inside is already old and brittle, squeezing it too hard will just crack it into pieces, making the leak much bigger. Always use a torque wrench and check if the bolts are already at their correct tightness before adding more pressure.

When to change the seals 

If tightening the bolts gently doesn't stop the oil, the rubber O-ring or gasket is dead. You cannot fix this with silicone glue or tape on the outside. The only real solution is to drain some oil, lift the bushing slightly, and put in a brand-new gasket. It takes some work, but it is the only way to keep the inside of your transformer safe and dry.