I NEED TO KNOEW ABOUT BUCHOLZ RELAY ,how it worke, any PPT about it so can tell us more information about it.

Try this WEB page:

Buchholz relay - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Buchholz_relay)

BUCHHOLZ RELAY, CONSTRUCTION OF BUCHHOLZ RELAY,DESIGN OF BUCHHOLZ RELAY,ADVANTAGES OF BUCHHOLZ RELAY,DISADVANTAGES OF BUCHHOLZ RELAY,CROSS SECTION OF BUCHHOLZ RELAY (http://electricalandelectronics.org/2009/03/19/buchholz-relay/)