Electrical transformers are complex, requiring synergy of multiple systems and regular maintenance to operate at full capacity. Why do transformers sometimes fail? Determining the weak link that caused a failure isn’t always easy. There are several factors that can cause a failure such as: Mechanical or electrical defaults, lightning or even human error. Fortunately, a long history of failure documentation and improved maintenance standards can help to prevent failures or detect them before the damage becomes permanent.
A common issue with aging transformers is insulation degradation. As a transformer heats up, the high temperatures can gradually weaken the insulation system. The weakening of the system will happen faster if the transformer is frequently overloaded. The net result of small, incremental increases in loading capacity over time is a weakened insulation system. Overloading causes overheating, and eventually thermal degradation that acts thrrough cracks in the insulation. Regular maintenance and diagnostic tests will help to detect this issue early. When thermal degradation has occurred, it will typically show as discoloration of cellulose.