Buchholz relay for transformer protection 3

[electricuwe]

In Europe the Buchholz relay is a very common protection device for oil-filled transformers, even for small (several 100 kVA) power ratings. It looks like that in other parts of the world the Buchholz relay is also known, but not very common. I would like to know if my assumption is correct at what type of protecion is used instead.

 

[electricuwe]

To yamin:

I guess it's not a good idea to add a time delay to avoid tripping during an earthquake. If Buchholz trip is delayed the transformer will be damaged more severe in case of a transformer failure. If earthquake might be a problem at your location you should try to interlock the Buchholz with a device sensing an earthquake.

But you also should consider if you really do not want the transformer to be tripped during an severe eartquake.

 

[prc]

Utilities do not want their trfs to be tripped for minor seismic tremors and for trfs to be installed in seismic areas utilities specify special Buchholtz relay and manufacturers do provide them.
Some cases Buchholtz relay trip can be slightly desensitised by adjusting the trip contacts with out adversely affecting the relay operation in case of a major fault.This will be required in case of maloperation of relay contact with the starting of oil cooling pumps.Other case is the operation of relay for an external line fault,the case explained by Peter.Many years ago , a hydro station was feeding power to 220 KV grid.Employees agitating for higher wages thought of pressing their demand by toppling a 220 KV tower near to station. Buchholtz relays in all generator trfs in the station tripped as the fault current caused the movement of windings inside trf which in turn cause a surge of oil to conservator tank causing the relay to trip.This will happen esp in case of water cooled trfs where oil qty will be less.Problem was solved by slightly desensitising the relays.But such desensitisation will not be helpful in case of frequent minor tremors,which are common in seismic regions.

 

[jbartos]

Suggestion. Rather than to time delay the Buchholz relay, because of its seismic sensitivity, it would be better to add a seismic relay that would shunt the Buchholz relay during earthquakes.

 

[sparky1976]

jbartos,
I've tried ABB website and siemens website, I cannot find any sismic relay, Could you advise me ?
thanks
Pitat

 

[prc]

Seismic proof Buchholtz Relays are not made by ABB and Siemens.You can get them from

http://www.cedaspe.com

http://www.messko.com

http://www.reinhausen.com