PHASE-ANGLE REGULATING TRANSFORMER PROTECTION

This paper will describe the protection of a 345KV, 450MVA three phase , phase angle regulating transformer. The transformer includes load ta p changers which permit phase angle variations of 250 advance to 25 de grees retard in a total of 32 steps (16 advance, 16 retard). As shown in figure 1, the series unit and the exciting unit of the PAR are moun ted in separate tanks, with four throat connections between the tanks (three-single phase primary connections and one-three phase secondary connection). The series unit is rated 86270V/66122V with the secondary windings connected in delta and the exciting unit is rated 345000V/67 728V grounded wye - grounded wye. The exciting unit is three legged co re type construction.