Operation Analysis of Transformer Gap Protection in Mawan General Power Plant

Based on three operation examples of the gap protection for 220 kV main transformers in Mawan General Power Plant,this paper analyzes the operating cause of the gap protection,and indicates that the transient overvoltage produced at the moment of single-phase grounding of system leads to the gap breakdown at the main transformer neutral.It further analyzes the misoperation possibility of the gap overcurrent protection,and proposes to prolong the time limit of the gap overcurrent protection to avoid unnecessary trip-out of generator-transformer units.