Design temperature in Transformer data Sheet?

[bmoorthy]

I am not anelectrical engineer.

Recently some one asked me to have a look at Liquid type transformer (IEC 60076-1)data sheet.

It was observed there was a term called Design Temperature.

I know electricl personnel are concerned about Temperature rise, Ambient Temperature. (Bot the data are given).

In addition to this there was a term called Design Temperature.

When i asked the person who included this information in the data sheet, he was slippery, it apears that he has copied this data with out much thinking.

Now the question:

1) What is the significance of Design Temperature in a Transforer
2) How is this data processed (For example, in case of Mechanical items, this information is processed to find the allowable stress, Impact test requirement etc)
3) Where can i find reference to design temperature in the context of Transformer (In IEC or NEC or CEN or En)

 

[electricuwe]

You can buy a copy of the IEC Standard you refer to at

http://www.iec.ch

. I don't know the standard by heart, but as far as I remember all relevant terms used are explained inside.

Regarding temperatures of transformers you always have to consider that transformer isolation is designed to achieve a certain lifetime requirement. Ageing of isolation is subject to en exponential increase with temperature

Having high ambient temperatures / high load condidtions continously may lead to signifcantly reduced useful lifetime if the transformer has been designed as a typical distribution transformer.

 

[safy2004]

There are some important temperature factors in the transformer design, you can find them in the IEC standard, which states them in details, but regarding your question about the (significance of temperature in design), you should notice that: Temperature is one of the prime factors that affect a transformer's life. In fact, increased temperature is the major cause of reduced transformer life. Further, the cause of most transformer failures is a breakdown of the insulation system.

 

[JensenDrive]

I did a bit of searching for:
IEC transformer "design temperature"
via Google and MSN Search, but was not quickly enlightened by anything that came up in the first 20 hits or so. That sort of hints that "design temperature" is being used informally to state temperature rise above a specified ambient, but that is just a guess.