The 5 Most Common Causes of Transformer Failure (And How to Prevent Them)

For any industrial or commercial operation, an electrical transformer is the heart of the system. It's a "set it and forget it" piece of equipment—until it fails. A sudden transformer failure is catastrophic, leading to unplanned downtime, expensive emergency repairs, and lost production.

The good news is that most transformer failures are preventable.

Understanding why they fail is the first step to building a reliable system. Here are the five most common causes of electrical transformer problems and what you can do about them.

1. Moisture and Contamination

Water is the number one enemy of a transformer. When moisture gets inside—either from a faulty gasket, a compromised breather (on oil-type units), or simple humidity (for dry-type units)—it severely degrades the insulation. This reduces the transformer's dielectric strength, leading to internal short-circuits and "arcing."

• How to Prevent It:

  • Oil-Type: Implement a regular maintenance schedule that includes oil testing. This test will detect moisture and other contaminants, allowing you to filter or "dehydrate" the oil before a failure occurs.

  • Dry-Type: Ensure the transformer is installed in a clean, dry, well-ventilated room, as their windings are more exposed to the ambient environment.

2. Overloading and Overheating

Every transformer has a kVA rating, which is its maximum safe load. When a facility expands—adding new machinery or increasing production—the electrical load often "creeps" up. Running a transformer consistently above its rated capacity generates excessive heat, which is the fastest way to destroy its insulation. Heat literally "cooks" the winding's solid insulation, making it brittle and weak until it cracks and fails.

• How to Prevent It:

  • Perform a regular load analysis to ensure you are not exceeding your transformer's capacity.

  • When planning a new project, invest in the correct size. A slightly larger transformer upfront is far cheaper than a replacement after a burnout.

  • Ensure cooling systems (radiators for oil, fans for dry-type) are clean and functional.

3. Electrical Surges (Lightning and Switching)

The electrical grid is not perfectly stable. Lightning strikes, even miles away, can send a massive voltage spike (a "transient") down the line. Even utility "grid switching" can cause smaller, repetitive surges. These spikes can puncture a transformer's insulation in a microsecond, leading to immediate failure.

• How to Prevent It:

  • Install and properly maintain high-quality surge arresters. These devices are the "shock absorbers" for your transformer, diverting dangerous voltage spikes safely to the ground.

  • Ensure your grounding (earthing) system is in excellent condition.

4. Lack of Maintenance

While transformers are reliable, they are not "zero-maintenance." Gaskets get old and crack, oil levels drop, dust and grime build up on cooling fins, and connections become loose over time. A loose connection creates resistance, which in turn creates a "hot spot" that can lead to a fire or burnout.

• How to Prevent It:

  • Implement a preventative maintenance schedule. This is the single most cost-effective thing you can do.

  • This schedule should include visual inspections, infrared thermal scanning (to find hot spots), and oil testing.

5. Old Age and End of Life

A well-maintained transformer can last 20-30 years, but it won't last forever. The transformer's insulation (paper and oil) degrades slowly over its entire life. After decades of thermal cycling, it becomes brittle and weak, and can fail from even a minor disturbance.

• How to Prevent It:

  • You can't prevent aging, but you can plan for it.

  • For critical transformers over 20 years old, start planning for a replacement. Budgeting for a planned replacement is far less stressful and costly than reacting to a catastrophic failure.

Don't Wait for a Failure

A reliable power system is built on prevention, not reaction.

At AZTransformer, we don't just supply new transformers; we provide long-term reliability. We can help you assess the health of your current equipment, recommend a preventative maintenance plan, or supply a high-quality replacement TMG transformer that will serve as the reliable heart of your operation for decades to come.

Contact us today to discuss your transformer needs.