Transformer cooling
Transformer cooling
(OP)
we have installed a 90/120/160 MVA Power Tranformer, 65 oC rise temperature. We have two groups of radiator, each one with 8 fans.
This 16 cooling fans which start, one part (8) in the first lever of cooling and second part (6) in the second level of cooling together with 2 oil pumps (one upper tank and one down tank). 2 fans remains for a reserve in case of fan failure.
1. I have a doubt with the design of the cooling (especially) in the flow determinated for the fans (18.0003/h). Does anybody could indicate me where i find information about the fans cooling dimensions.
2. Does anybody could explain why a buccholz (for the same transformer) could operate (oil flow) caused by the start of one pump (upper tank). When both start together never trip the relay.
Thanks.
This 16 cooling fans which start, one part (8) in the first lever of cooling and second part (6) in the second level of cooling together with 2 oil pumps (one upper tank and one down tank). 2 fans remains for a reserve in case of fan failure.
1. I have a doubt with the design of the cooling (especially) in the flow determinated for the fans (18.0003/h). Does anybody could indicate me where i find information about the fans cooling dimensions.
2. Does anybody could explain why a buccholz (for the same transformer) could operate (oil flow) caused by the start of one pump (upper tank). When both start together never trip the relay.
Thanks.






RE: Transformer cooling
If there were a check valve in the system it would slam when one pump started but not two which certainly is a more abrupt transient. Check valves are very common where multiple pumps are in our plant systems but I have never seen one in a transformer.
Can someone refresh my memory on Buchholz... is that like a sudden pressure or a gas accumulation relay or something else?
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RE: Transformer cooling
A Buchholz-relay is a gas operated relay fitted into the oil pipe between the transformer and the conservator tank - used on conservator type transformers (only).
The Sudden Pressure relay is a pressure operated relay common on sealed tank transformers, but it can also be used on conservator type transformers.
Nandrade:
The J&P Transformer Book have some info regarding cooling. I don't have a copy right now, but when I return to work I'll will look if they state some standards.
Regards
Ralph
RE: Transformer cooling
ko (www.ecooling.biz)
RE: Transformer cooling
http://www.emb-online.de/Buchh_en.htm
is fairly typical of a European Buchholz relay.
This type has two floats in a chamber and a pivoted flapper plate suspended between the inlet and outlet ports. The two floats operate reed switches via magnets mounted on the float arm. In normal conditions the relay chamber is full of oil. If a gassing fault occurs, gas collectes in the chamber, causing the float to fall as trapped gas displaces the oil. The upper float is usually configured to alarm when gas accumulates in the chamber. The gas may be removed for analysis. The lower float is usually configured as a trip, being activated by large volumes of gas or low oil level. The trip contact is also operated by the flapper which responds to oil surge in the conservator pipe by pivoting from its neutral position. Oil surge typically signifies a major problem developing within the tank.
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RE: Transformer cooling
electricpete, Buchholtz relay is used with open type conservators (free breathing or with air cell ) in place of gas accumulating relay used in US with nitrogen sealed trfs.
Operation of Buccholtz with start of pump is not un common .It means an oil surge is created in the oil pipe (hope relay trip is working and not alarm )when the pump sucks or pushes the oil .Sometimes it may be due to wrong design of pipe lines (cooler and Buchholtz) By closely watching the trf when pump is switched on ,one can normally detect the cause of maloperation .Practical solution at site :slightly desensitise the relay or modify pipe line.Normally manufactuers should check and ensure that relay is not activitated by the start of pump.
Why doubt the cooling by fan ? Any indications -excessive oil temp rise ? Check whether the fan direction is correct.Normally propeller fans will be pushing air in to radiators.Of course all radiator valves must be in open condition !If you give size of raiators (length *width *no of elements ) &fan details (sweep ,1/3 phase, flow rate ) I can comment.