Summary
Power transformer is a vital component in the power system, and it must be protected against various core and winding faults. Turn‐to‐turn fault (TTF) is one of the most common faults in transformer that causes catastrophic events such as transformer explosion, winding, or core deformation. Conventional differential relay is a common device for protection of transformer protection, and it can diagnose the severe TTF; however, it fails to detect the TTF at incipient stage. Recently, several methods and techniques have been introduced to improve the differential relay performance against TTFs. These approaches use various quantities such as current/voltage, frequency, and magnetic flux to detect the TTF in transformer winding. This paper reviews and compares various online and offline TTF diagnosis methods. Moreover, the advantages and disadvantages of these methods are discussed in the paper to analyze their performance in different conditions.