Breathing new life into old transformers

Technology from ABB can extend a transformer’s lifetime by up to 25 years, using a drying process that can finish the job in four or five days without moving the unit.

Transformers are among the simplest electrical devices, and they come in all sizes – from a tiny coupling transformer inside a microphone, to an 800-ton phase-shifting unit that regulates power flow in national power grids.

The problem is that the paper and mineral oil insulating the interior of many transformers degrades over time. This leaves a residue of water and acid that begins to accumulate inside the transformer, and eventually accelerates its breakdown.

Without proper insulation, a transformer gradually loses its ability to withstand the rigor of daily operations and stressful events like short circuits.

But ABB has developed a new drying method that combines low frequency heating and oil filtration to save the insulation, and ultimately, the transformer.

When this method was used to dry two, 69-tonne, 200-MVA, 300/125/17 kV Nett transformers for the Norse utility Lyse Energi, each transformer’s lifecycle was extended by 10 to 15 years, a significant savings for the utility.