Which of the following is not a common reason for transformer failure?

The reason electromagnetic interference is considered not a common cause for transformer failure lies in the nature of how transformers operate and the precautions taken in their design and installation. Transformers are built to minimize the effects of external electromagnetic fields, and they typically have shielding and grounding practices in place that help reduce susceptibility to interference.

On the other hand, overheating, mechanical damage, and insulation breakdown are well-documented causes of transformer failures. Overheating can occur due to overloading, inadequate cooling, or poor maintenance, potentially leading to insulation failure. Mechanical damage might result from physical impacts or environmental conditions, while insulation breakdown can arise from age-related degradation, moisture ingress, or electrical stresses during operation. These three factors are prevalent in transformer operations and maintenance issues, making them key considerations in reliability and performance evaluations.