Abstract: In Zhejiang power grid system, as a general rule, the low voltage winding of 220 kV three-winding transformer adopts the"△"connection mode.This paper illustrates two typical cases of low voltage winding DC resistance abnormal of large capacity transformer, summarizes the key points of detection, analysis and judgment of low voltage winding DC resistance unbalance problem in principles and methods, which provides effective reference experience for field treatment of DC resistance abnormal.It is expected to strongly improve the efficiency of similar defect detection and fault handling.