My Mind, My Heart, My File

Abstract
The fact, that worldwide the percentage of power transformers with an age above the design life time is fairly above 50%, means, that nor the financial nor the production capacity will be sufficient in order to replace these transformers on a regular schedule. Further the increasing political pressure to maintain an uninterrupted reliable service requires well approved systems to keep even transformers with low remaining substance under acceptable controlled risk in service for a certain period. In order to take the technical and commercial optimized decisions the actual substance must be evaluated, the ageing behaviour taken in account and the necessary measures for conservation of a remaining useful substance applied.
The typical ageing behaviour due to the well-known ageing accelerators heat, water, acidity and oxygen of power transformers will be discussed. It will also commented, that the individual design of a transformer has a not neglectable influence also.
It will be discussed, how a acceptable substance evaluation is possible, using the complex information’s of the different ageing indicators. It is obvious, that only one indicator (i.e. Furan analysis) will often not give a sufficient detailed picture. At that time a rough scheme of 4 categories seems practicable: 1= full substance (new), 2= reduced, 3. conservable substance 4. No substance left.
The methods already on the market to conserve the substance under category 1-3 and the possibility to keep cat. 4 transformers for a certain time running observing the necessary responsibility will be critically discussed.
At hand of typical examples between a range of 20 to 600MVA transformers successful conservation schemes will be documented using classical DGA and sophisticated on line gas monitoring. At least, but not at last the positive technical and economical impact will be commented.

See detail in :  Ageing Behaviour, Substance Evaluation and Conservation of Power Transformers