Any power engineers here? Running transformers past their rating

[Mark R]

Just wondered what sort of safety margin utility distribution transformers have, in case you needed to increase the power flow.

Would it be common to run transformers at 900% above their rated power? Would there be any significant risks in doing that?

Text According to this article, thousands of transformers are being overrated in this way - many 400%, or more, above rated power. Is this article even credible?

 

[DainBramaged]

I'm a power ranger, does that count?

 

[NikolaeVarius]

I would imagine something would short and Blow after 400%. I mean 4 times rated output is not good.

 

[KMurphy]

I didn't read the article, but the utility in my area typically loads pole mounted transformers to 200% or so. A transformer would not last long at all (a few minutes maybe) at 900%. The risk is insulation failure within the transformer and it shorting internally. If primary protection (fuses or breakers) don't interrupt the fault quickly, the oil will overheat and explode.

 

[KMurphy]

I'm a power engineer for a large industrial complex and don't know capabilities of these smaller transformers. I wouldn't imagine the transformer manufacturer overdesigning their products by 900%; that is money on the table they are giving up. Internal temperature is the main thing to look at. The insulation is designed to withstand a specified temperature for a specified time; for larger transformers it's a 65C rise above 40C ambient for 30 years. Each 10C above rated temperature results in a halving of insulation life. The transformer is designed to handle a specified load without going over the rated temperature. If more efficient cooling can be achieved, loading can be increased respectively. I'm having trouble believing 900%.