5 Common Issues Found During Transformer Overhaul No transformer runs forever without picking up wear. Even units that seem fine on the surface often hide stress deep inside. Oil ages. Windings shift slightly. Paper insulation loses its shape. And over time, even minor issues build into something more. Opening up a transformer during overhaul tells you what routine monitoring misses. What you find inside usually reflects years of thermal, electrical, and mechanical history. Here are five issues that tend to show up most often during a full overhaul.
1. Insulation Paper That No Longer Holds Its Shape Insulation wear shows in more ways than just burning or tearing. In many cases, the paper becomes dry, brittle, or glossy. It begins to lose the grip it once had around winding turns. That shift opens up space for future movement, especially under mechanical stress. During overhaul, this weak insulation is either reinforced or replaced entirely. Skipping this can lead to early failure when the unit goes back into service, especially in areas with repeated load cycling. A reliable transformer manufacturing unit ensures proper insulation checks and quality standards to enhance durability.
2. Carbon Traces Around Tap Changer Contacts Tap changers go through arc wear with every switch. Over time, that adds up. You start seeing carbon paths along the insulating structure.
These paths give current more ways to travel during operation, often leading to flashovers or erratic switching. During an overhaul, it becomes important to clean these traces, examine the moving contacts, and inspect springs or pressure arms. In some cases, the fix involves replacing components altogether.
3. Coil Bracing That Has Shifted or Settled Bracing holds the winding in place against mechanical forces during faults or surges. But over years of vibration, heat, and system stress, bracing elements start to move. Spacers compress. Clamps loosen. And wedges may fall slightly out of place. This affects the way the winding behaves under stress. Even if no damage has happened yet, leaving loose bracing in place shortens the unit’s operating life. Most overhaul teams address this immediately to restore internal stability.
4. Gasket Material That Has Aged Out Gaskets wear down slowly, but the signs become clearer during an overhaul. Some stiffen and crack. Others turn soft and start bulging near bolt lines. Even when there’s no obvious leak, that seal may no longer hold up under pressure or vibration. Teams usually swap out old gasket sets with more durable options. Silicone rubber and nitrile blends hold their shape better under oil, temperature shifts, and mechanical tension, making them a better fit for long-term service. Many leading transformer brands rely on these gasket materials to ensure reliability and extended performance.
5. Oil That Has Visibly Degraded Fresh oil runs clear. Used oil doesn’t always show damage in lab numbers, but up close, the picture shifts. Sludge on the tank wall, a burnt smell, or patchy discoloration all point to stress that’s built up over the years. That’s why most overhauls include a complete oil flush. Fresh fluid helps reset the thermal behavior of the unit. It also reduces the chances of early hotspot formation once the transformer goes back under full load.
Final Thoughts Overhauls give transformers a second life, but only if the right problems are caught early.
In our experience, identifying wear patterns and reading the physical signs matter just as much as what the tests say. That’s how we support rebuilds that perform well long after the unit leaves the shop. Our team handles end-to-end refurbishments, helping facilities rebuild capacity without cutting corners on durability or performance. With the expertise of leading industrial transformer manufacturers like Makpower, we ensure reliable results every time.
