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Technical Goals of Transformer Maintenance

3. Acid Problem

Motto: In most cases the delicate transformer insulation is allowed to stew in a chemical cocktail of its own waste.

To extend the life of a transformer, the content of the aging products in its oil inventory must be very often strongly reduced, because the organic acids, alcohols, metallic soaps, aldehydes and ketones not only atack the insulants, but work as a catalysts and promote (with the diluted water and the oxygen) so-called avalanche aging effect resulting in the exponential increase of the failure probability density in the time.

For the decision what treatment process should be used, serves most often NN- value (Neutralization Number) of the oil.

NN (mgKOH/g oil) Treatment
<< 0.1 no treatment necessary
>= 0.1 the change or reclamation of oil inventory
> 0.3 in situ long-term reclamation of oil inventory combined with desludging
> 0.5 long-term reclamation of oil invetory combined with the high- powered desludging

Continually working at, or allowing the transformer to reach the upper limits of contamination, rather than maintaining absolute limits of all, considerably increases the cost of maintenance, the risk of failure, and dramatically shortens the life span.

For the cost of the "transformer detoxication" See Economical Goals, Table E6