The faults appear in the transformer inside the insulating oil will be determined by Buchholz relay . In case any specific fault occurs in the transformer but not in oil then it can not be determined by Buchholz relay . Any flash over at the bushings are not adequately protected by Buchholz relay . Differential relays can detect such type of faults . Moreover Buchholz relay is provided in transformer for detecting any internal fault in the transformer but Differential Protection scheme detects the same in faster way .