What Causes Winding Overheating and Hot Spots?
Quick answer — A winding hot spot is a local over-temperature caused by uneven cooling or current distribution, a partial oil-flow block, a stray loss, a poor connection, or an overload. The winding-temperature gradient and the design set the hottest-spot. A persistent hot spot ages the insulation locally and can cause an overheating or thermal failure. It is seen by temperature monitoring, DGA and a thermal inspection.
What causes a winding hot spot (overheating)?
Causes
Uneven cooling, a blocked oil channel, stray loss in the winding, a loose/poor connection, a turn fault, or a local overload create a hot spot.
Why it is dangerous
The insulation at the hot spot ages faster, so a local failure can develop even if the average temperature is fine.
Detection
Winding-temperature measurement, fibre-optic hot-spot sensors, DGA (for overheating gases), and a thermographic inspection reveal a hot spot.
References & standards
- IEC 60076-7
- IEEE C57.91
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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