Transformer Tertiary is not loaded, why its winding temperature higher

[Beengineer]

THe tertiary is not connected to the load, but its winding temperature gauge reading is highest among the three windings.

I would like to listen to your opinion.

 

[DTR2011]

check the calibration of temp gauges

 

[Marmite]

More details required. Voltage ratio,rating, winding configuration, transformer purpose, unbalanced loading, harmonics etc.
Regards
Marmite

 

[rbulsara]

What are the temp readings? plus other info requested by Marmite. There is no useful information in your post.

Rafiq Bulsara

http://www.srengineersct.com

 

[marks1080]

zero sequence currents?

 

[Beengineer]

My point is that the winding temperature reading is the simulated value. Basically it's the oil temperature plus the diverted load current times a constant that was pre-calibrated by the OEM.

My question was, if there is the zero load current in the tertiary (tertiary is not connected to the load), how the tertiary winding temperature was higher than the other two winding? the winding temperature of tertiary should not exceed the oild temperature.

 

[alehman]

Probably need to talk to the manufacturer.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[DTR2011]

is the ct feeding the gauge from the correct winding? It could be that you have a ct from HV or LV wired to the TV gauge.

 

[waross]

If the tertiary is delta, unbalanced primary voltages may cause heavy circulating current in the delta.

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

 

[TurbineGen]

Imbalanced loads will overheat the tertiary. We once made the mistake of single phasing a 40 MVA transformer line to line at just a few MVA and smelled burned oil within minutes. The tertiary wasn't connected, but it sure burned up nice.

------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[Beengineer]

"Unbalanced Load" - Excellent Point, thanks!

 

[bacon4life]

How large is the temperature difference? I have measured adjacent probe pockets with a difference of several degrees C.

Is the CT feeding the gauge on the tertiary bushings, or on the delta part of the winding? If they are on the bushings you have a calibration problem.

Are they separate gauges or an electronic monitor?

 

[marks1080]

The tert windings are still connected to each other - ie: not open circuited. This acts like a shunt for unbalanced currents and is one of the main functions of a tert winding. Unless you are exceed temp limitation everything is probably fine.