Local winding temperatures. Survey

[KnicksJets]

Just a survey question. Would appreciate if you can reply.

The local winding temperature gauges (analog, Qualitrol) on our GSUs are connected to the CT on HV windings. When we loose power to the cooling cabinet of the Transformer (that powers fans and pumps) we still get the winding temperature reading, coz the power is from CT.

Is this the configuration you have? Is that the normal case? Question arose when we had to shut down the cooling banks in the transformer and how we would monitor the winding temperature.

 

[Marmite]

It's going to depend on the design. In my experience with UK standard transformers, the answer would be yes it would still work. The CT heats a heating element within the winding temperature gauge itself and modifies the reading from the bulb and capilliary. That arrangement would still work without the auxiliary supply, but obviously you would lose pumps, fans and possibly (but usually not)alarms.
I recommend you have a look at the multicore drawing to see how it's wired for a definite answer.
Regards
Marmite

 

[rovineye]

Shipboard propulsion tansformers, with T-154 monitors with its own power supply.

 

[oldfieldguy]

Pdshah--

What you're describing is a pretty standard arrangement. These units require no external power to operate, as Marmite says.

If the transformer is under little or no load for a period of time, you'll probably see the oil temperature and winding temperature at essentially the same reading. When current starts flowing, the winding temperature will climb in proportion to the increased current through the windings. You have to remember that it is not a true measurement, but rather a simulation.

old field guy

 

[KnicksJets]

Thanks
A little late but it helps. This was just a survey, Our units have similar configuration.