Transformers are the most important devices in power distribution, whereby one distinguishes between distribution, machine, special, and coupling transformers.
In principle, all transformers consist of the following materials:

  • insulating material, e.g. pressboard
  • paper
  • wood and transformer oil, which is used for insulation and cooling
  • electrical sheets
  • copper

During normal operation, these materials are subjected to natural ageing, which is largely affected by the operating conditions. Normal operating life is about 25 to 30 years, provided the transformers are serviced and maintained professionally.

However, during its life a transformer can be subjected to events that definitely cannot be viewed as normal operation:

  • for example, overload or overvoltage with associated overheating, and problems in the cooling system.

All these events will accelerate the materials' ageing process. One of the most frequent sources of transformer problems is the oil. In order to detect oil deterioration at an early stage, the oil must be examined regularly. This permits counter-measures to be taken, which admittedly do not prevent the ageing process, but delay it considerably.