Distribution transformer efficiency vs. aging 1

[Power0020]

I couldn't find any curve/relation between distribution transformer aging and reduction in efficiency. Oil degradation and winding insulation degradation are main causes of aging incerasing the failure risk. Any clue about efficiency vs. aging?

 

[waross]

From this site:

http://steel.keytometals.com/Articles/Art101.htm

The earliest soft magnetic material was iron, which contained many impurities. Researchers found that the addition of silicon increased resistivity, decreased hysteresis loss, increased permeability, and virtually eliminated aging.

I found another reference that stated that transformer steel is made with very low levels of carbon. Carbon inclusion was stated to promote ageing.

And this;
TRANSFORMER PRINCIPLES AND PRACTICE. 2nd Edition 1950
pp. 23
"Ageing always occurred in transformers built before the introduction of silicon steel (about 1910)


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jghrist]

Efficiency is a function of iron losses and copper losses, neither of which are affected by aging to any significant degree.

 

[prc]

Losses in a transformer will not increase with ageing. But of course 100 years back, situation was not like this. No-load losses used to go up with time, due to poor quality of insulation coating used and quality of steel/iron used.

 

[Power0020]

Clear. Does oil impurities add to any of these losses? distribution transformers on 11/0.4 kV level (IEC World) may be subject to low rate of oil checks and testing. Some engineers even aren't worried about oil quality at that voltage level while the word "aging" the insulation isn't a big issue with utilities having hundreds of lightly loaded transformers.

Should I worry about oil at that voltage level?

 

[unclebob]

I would do a Disolved Gas Analysis (DGA) and a standard ASTM test on the fluid to verify the quality of the oil and to determine if fault gases are present. If something is wrong in the transformer, these tests will show it.