Simple Things to Check the Bushings During Your Daily Walk-around

You don't always need fancy tools to tell if a transformer bushing is in trouble. Some of the biggest problems give off warnings that you can see or hear if you know what to look for. 

Doing a quick check every day can save your equipment from a total breakdown.

Listen for buzzing or hissing

When you walk near the transformer, it should have a steady, low hum. If you hear a sharp "spitting" sound or a constant buzzing coming from the top of the bushing, pay attention. This is often the sound of electricity jumping through the air because of dirt or a loose part. It’s usually louder when the air is damp or foggy. 

If the bushing is making noise, it needs a close inspection.

Look for "tracking" lines

Take a close look at the surface of the insulator. Do you see thin, black lines that look like tiny tree branches? These are called "carbon tracks." They happen when electricity crawls across the surface because the bushing is too dirty. 

If you see these black marks, you must clean the bushing soon. If you wait, those tracks will eventually cause a short circuit.

Watch the oil level gauge

This is the easiest check. Most bushings have a small glass window to show the oil level. The oil should be right in the middle. If you can’t see any oil, it might have leaked out into the transformer. If the oil is way too high, it might be getting pushed up by a problem inside the tank. Either way, if the level changes suddenly, call a technician.

Check the color of the metal

The copper or aluminum connectors on top should look like normal metal. If they look purple, blue, or black, they have been getting way too hot. This usually means the connection is loose or there is too much power running through a small point. 

You don't need an infrared camera to see this; the color change is a clear warning that the metal is "cooking."

Look for leaks at the base

Check the area where the bushing meets the transformer tank. It should be bone dry. If you see a dark, wet ring or dust sticking to one spot, oil is probably seeping out. Even a tiny drip can let moisture get inside over time. A clean bushing is a healthy bushing, so any sign of wetness is a reason to take action.