transformer

Transformers are not always filled with N2 gas. The transformer powering your computer does not have N2 gas. Now the transformers that do have nitrogen gas filling do this so that the gas around the wiring does not have any moisture to degrade the insulation of the gas and to prevent possible condensation from rusting the iron core and casing.

Because Oxygen and heat will oxdize and degrade both the dielectrc fluid and the cellulose insulation. Using N2 to replace the atmospheric air thus greatly reducing the O2 content of the head space gas in contact with the Liquid Insulation (Oil) will extend the life of the transformer.

Once the solid insulation (Cellulsoe based Kraft paper) on the windings in large transformer and the Liquid Insulation (the oil) is degraded the life of the transformer becomes shortened from the expected 20-40 years down to 10 or so.

Thus the Oil Preservation system (the N2 blanket or the Active Nitgrogen System or Conservator tanks with bladders) is critical in protecting the dielectrics and extending the life of this very expensive equipment.

Free breathing units are smaller units that do not get that hot or are relatively low voltage such as pole mount transformers and pad mts.

No moisture

Non-Flammable

Insulative

Environmentally Friendly

Easy to work with

Because the nitrogen is always maintained in a dry state and this has a great advantage that it maintains the oil and insulation in as dry a condition as possible.

The only disadvantage is the supply and cost of the nitrogen needed to maintain a constant supply thus adding to the routine maintenance activities.

In reply to several of the comments on N2 usage in transformers (Xfmr) which were almost correct but needed further comments to make them accurate.

Head space in transformers: Purpose/ function / requirement / cost/

Purpose of head space: for expansion of the oil as it heats from loading. Head space can be eliminated by using a conservator tank.

Head space can be air as in free breathing units or some low cost manufactures will put dry air into the headspace of sealed tank Xfmrs.

Why Nitrogen (N2)?. INERT. The more O2 that is eliminated from the oil and head space the longer the life of the oil and the cellulose insulation.

The Xfmr Manufactures (US and Europe) spend great effort and $ to dry the core and coils to less than 0.5% moisture. After tanking..the oil added must be less than 10 ppm of H20. This will prevent moisture from moving into the paper. Moisture, Oxygen and heat are the destructive forces on cellulose (Kraft paper) degradation.

Once the tank is sealed and to protect the oil and paper from excess H20...DRY (-50C Dew Point) AIR can be added as the head space gas.

PREFERRED for long life of the XFMR: Dry (-50C dew Point) Nitrogen is used in the head space. The nitrogen is 99.999 % N2. This protects the oil and paper from the effects of excess O2 which causes Oxidation and degradation of the oil and then the paper.

N2 (Dry, -50C dew point) is NOT any more expensive than Dry Air (-50C dew point). In sealed tanks it is a onetime fill unless bushing replacement or other reasons for compromising the head space is performed.

ACTIVE Nitrogen systems use attached bottles of N2 to maintain pressure in large power Xfmrs that undergo large loading changes or are in climates that cause high fluid temp changes. These changes cause the oil to expand and increase headspace pressure or when cold to contract thus creating negative headspace pressure. To keep the pressure somewhat stable...the Xfmr has a press relief valve that releases N2 and press during high loading. When loading decreases the head space may become negative and thus the gages release N2 into the head space automatically to maintain a fairly constant headspace press.

Key: DRY! Inert (low O2)! Cheap: N2 is cheap. Active: is expensive but only on very large power Xfmrs and most large power units are designed with conservator tank using Bladders to prevent any contact with air. Thus eliminate H20 and O2 contamination of the oil.

So why N1 is not using?

Giggle, you so funny.

Nitrogen is a 2-atom molecule, and is written N₂.