Transformer Temp Trip

[dfdt]

I want to know your views on need to trip power transformers (>25 MVA)on high winding and/or oil temperature. In my opinion oil or winding temp tracks thermal loadng of the transformer and thus should always be enabled to protect the transformers.

 

[prc]

In transformers, OTI and WTI are used mainly as monitoring accessories than protective relays.Any overcurrent will actuate protective relays well before the WTI come in to operation,as time constants of OTI may be 1.5-3.5 hours and WTI 5-10 minutes.Sure sometimes it can act as a protective link, say in case some one load a transformer with the cooler bank completely cut off.Then Alaram contacts will operate followed by trip. But such scenarios are very rare in reality.

 

[dfdt]

Thanks for your comments but question is that one cannot set over current relay to match thermal overload capability of the transformer and hence it's good idea to configure some sort of thermal protection to trip the transformer in my view.

 

[inpran]

There are thermal overload protection for that. Not that the idea of tripping transformer on high windning temperature is uncommon.

 

[jghrist]

To trip or not on high temperature depends on how a high temperature alarm is handled. Also on the costs of tripping. A transformer can withstand a high temperature for a while with some loss of life. Tripping the transformer could result in loss of production or other high costs.

 

[dfdt]

As a matter of interest I am interested to know the the views of transformers manufacturers on this subject.Do they recommend to trip on high oil or winding temperature or not?