What is a primary reason for failures in a transformer core?

A primary reason for failures in a transformer core is the deterioration of insulation layers. Insulation layers are critical to the safe and efficient operation of the transformer, as they prevent electrical currents from leaking and causing short circuits or arcing within the core. When insulation begins to break down due to factors such as thermal aging, moisture ingress, or chemical contamination, it can lead to increased electrical stress on the core materials. This deterioration can result in partial discharges or even complete insulation breakdown, compromising the integrity of the transformer and potentially leading to catastrophic failure.

In contrast, while excessive load connected to the secondary can lead to overheating and operational issues, it does not directly cause failure in the transformer core itself. Improper grounding primarily affects safety and fault clearing rather than the core structure. Inadequate cooling of the core can lead to overheating, but this scenario would be more related to thermal issues than core insulation failure specifically. Thus, the deterioration of insulation layers stands out as the key factor contributing to transformer core failures.