Analysis on burning failure of main transformer in 220kV substation

Abstract

Abstract Neutral point ungrounded three-phase system is widely used in 10kV and 35kV low-voltage systems because of its higher power supply reliability. When the single-phase grounding short-circuit fault occurs in the system, the other two phases can continue to operate for a period of time to ensure the reliability of power supply. However, when the system operates under single-phase grounding fault, arc grounding overvoltage is easy to occur, which may damage electrical equipment or develop into phase-to-phase short circuit. This paper analyses a burning accident of main transformer caused by arc grounding overvoltage in 220kV substation, obtains fault recording information, points out fault causes and puts forward corresponding preventive measures.