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Technical Goals of Transformer Maintenance

5. Gas Problem

In the last time is there a new and growing industry awareness, that by maintaining consistently low oxygen level in the transformer oil inventory, the transformer will be considerably less likely to fail partially or fully, and the life-expectancy can be considerably extended.

The theoretical and experimental works explicitly show - See e.g. Lampe, Spicar: Oxygen-free transformer, reduced Ageing by continuous Degassing, CIGRE 1976, paper 12-05, that the aging process in the cellulose insulants can be successfuly suppressed by the permanent:

The permanent reduction of the average temperature of a transformer can be relatively difficult ( auxiliarry radiators, ONAN » OFAF change, …).

The present methods for the strong reduction of the oxygen ingress into transformer / reducing O2 content in the oil are:

As a comparison level is used - 100% aging intensity of given transformer = oil inventory fully saturated with oxygen (~ 22 000 ppm) & temperature over 50 C

Oxygen content in oil (ppm) Intensity of aging process (%) Treatment
4 - 7000 ca 30 active systems
ca 4000 10 - 20 passive systems
< 1000 < 5 combined systems

The costs, advantages and draw-backs of a various methods are described in Economical Goals , Table E3, Table E4 and Table E5.

Because of the installation cost of classical "hermetization of transformer e.g. Bag-In Tank or Membrane-In Tank " is relatively very high and the transformer must be long-term shut-down for up-grade - in fact the whole conservator must be changed, the ARS-Altmann Group invent a completely new method without above mentioned draw-backs.

5.1 TRAFOSEAL

The free breathing conservator provides a continuous supply of fresh oxygen and other atmospheric gases to the transformers main tank.

ARS Altmann Systems have completely and permanently removed the problem of oil and air contact, by redesigning the plumbing or physical connection between the conservator and the main tank.

As a "seal" the stratification layer is used, a natural and therefore long-lasting (and) indestructible membrane-like physical phenomenon, which is always spontaneously created in:

between the hot oil from the main tank and the cold oil from the conservator.

The thermal stratification layer, between the cold (gas contaminated) oil from the conservator and hot (protected) oil in the main tank, acts therefore as a very thin "membrane" which divides both liquids and prohibits its mixing.