Current transformer defect detected by DGA

A defect of oil-paper insulated current transformer detected only by the DGA(Dissolved Gas Analysis) test is studied.Except the DGA,the results of all its routine and diagnostic electrical tests by manufacturer are shown normal.After disassembly,it is found that,the burr occurred on the wounded copper grounding bar of the primary windings induces the spark discharge and produces C2H2 in insulating oil.It is pointed out that,more attention should be paid to the defect which could not be detected by routine and diagnostic electrical tests.