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It is a gas operated relay.It is placed between Main Tank & Conservator Tank,with an angle5-7 Degree.There are2 Mercury switches, one in the top & other in the bottom of Bucholz relay,filled with Transformer Oil. When small amount of vapour passes through the relay Top Float will operate, gives Bucholz alarm.In case of heavy internal fault, Large amount of Bubbles forms,operates the Bottom Float , Gives Bucholz Trip.In case of Bucholz Alarm/Trip Relay contact to checked first(IN Alarm/Trip Relay contact will change).then if there was any gas formation occured.Gas should be relaesed through the top Vent of relay( in that time hissing sound is observed in case of Gas present).Have to release all other top vent in Main Tank & Radiator Top.
In case of OLTC, there are saperare OLTC Surge Relay, same as Main tank Bucholz Relay.
After gas release if Trafo again tripped in Bucholz.Then there must be some hot spot/heavy internal fault in Trafo.other necessory testing to be carried out, like Ratio test,Magnetic Balance test,Vector group test,IR Test for further fault finding.
It is one of the simplest mechanism to catch incipient faults at the earliet stage and protect the transformer
Hence one should give it an important treatement when wiring it to the protection circuit ( At least at par with ANSI 87 T ) , Hence connect the original Un multiplied contact of BUCHOLTZ , Directly to the tripping coil or at least to ANSI 86 , Master tripping relay. If it is wired through contact multiplication or through a IED Relay logic the protection scheme is made dependent on a DC supply and reliability is reduced.
bucholz relay any fault in transfomer gas and hot oil move upwards from main tank to conservator tank and cold oil come down to conservator tank to main tank that's flow act relay called bucholz relay
Buchholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. Whenever any internal fault occurs in a transformer, the boucholz relay at once gives an alarm for some time, if the transformer is isolated from the circuit then it stops the alarm itself otherwise it trips the circuit by its own tripping mechanism.
Almost all large oil-filled transformers are equipped with a Buchholz relay, first developed by Max Buchholz in1921
A Buchholz relay is a gas and oil operated device installed in the pipework between the top of the transformer main tank and the conservator. A second relay is sometimes used for the tapchanger selector chamber.
The function of the relay is to detect an abnormal condition within the tank and send an alarm or trip signal. Under normal conditions the relay is completely full of oil. Operation occurs when floats are displaced by an accumulation of gas, or a flap is moved by a surge of oil.
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