Transformer Relay 63 Problem During DGA Sampling

Go ahead and disconnect it.

It's oil, not soil.

In my opinion you need to discuss your proposal with the transformer manufacturer and obtain their response before doing anything. Do you know how to use a telephone, Mildred?

It depends on whether you do your oil sampling with the transformer energized or not.

Ideally, putting the sudden pressure relay in line with the sample valve is a bad idea just for the reason you are seeing. The change in pressure caused by opening the sample port operates the relay. Could you consider buying a different 63 relay that could be installed in a separate port on the tank of the transformer?

If sampling is done when energized, I assume that the 63 relay trips your breaker(s) but you don't want it to. The main reason you wouldn't want to disconnect the relay is that if there is a vacuum in the transformer's over-oil gas space, opening the sample port could draw air into the oil. The air bubble then making its way up through the oil inside the tank has a finite chance of causing an arc (dielectric strength of air is less than oil). If that happens, you want the 63 to operate!

If you deenergize the transformer to sample the oil, then go ahead and disconnect the relay temporarily. Your breakers will probably already be open, so the relay shouldn't do more than alarm. Just remember to reconnect the relay when your sampling is done!

if sampling valve is opened very slowly will it happen.

Thank you very much PeterT for your reply,

The idea to install new 63 relay is really new to me. If you don't mind, can you share several references for this?

We thought the reason why the sudden pressure installation installed in line with the sampling test, because during that time (1975) the DGA test is not popular. This design is also same for our plant transformers which manufactured in 1975..

@ Crabtree,

Actually we don't know who manufactured the transformer. The nameplate is already gone and also we cannot find the technical document in our library.

We already try to contact and email several transformer manufacturers for the past 3 months. But until now, we don't get any respond at all..so we hope CR4 can give us some opinions

I want to ask question again: In your plant, do you de-energize your transformer during sampling oil for the DGA test?

Your reply is highly appreciated.

Thank you.

"I want to ask question again: In your plant, do you de-energize your transformer during sampling oil for the DGA test? "

Answer : If it is safe to do so (and the load needs to have supply all the time) we do the sampling whilest the Transformer is energized otherwise de-energizing is always the best practice

The sudden pressure relays we see most often are made by Qualitrol. They either screw into a threaded port / hole in the transformer tank side or bolt to a flange. There is an auxiliary relay board that is often used with it (63FPX) that you should also consider. See the following link:

http://www.qualitrolcorp.com/Products/QUALITROL_900_910_Rapid_pressure_rise_relays/