Adaptability Analysis of Differential Protection for Series Transformers of Unified Power Flow Controller

The series transformer is one of the core components of the Unified Power Flow Controller (UPFC). The series transformer has a special primary structure and special system operating characteristics. Taking the simulation system of the actual UPFC project as an example, this paper discusses the factors that may affect the sensitivity and reliability of the series transformer differential protection under various faults. Combined with the simulation results of the typical faults in the series transformer, the longitudinal differential protection is analyzed. Reflecting the new problems that arise when series transformers have various types of faults, the adaptive analysis of the differential protection is formed. This paper also discusses the relationship between valve control protection and AC relay protection of series transformers from the perspective of protection equipment.