The electric tests of ordinate insulation in converter transformer by the method of applying voltage on single-phase

Converter transformer is the key equipment in HVDC. In the great capability direct current system used in the nonferrous metal (e.g. aluminum) electrolytic production, converter transformers are parallel connected. In order to reduce harmonics into power system, these converter transforms are installed phase-shifting windings to produce different phases on high voltage AC side and the neutral point is grading insulated. According to 12 impulse technology, delta and wye connection windings are used at low voltage side. The three phases of those transformers including regulating transformer and control transformer are installed in a tank. Generally, withstand voltage and leave line partial discharge of the ordinate insulation are measured in laboratory. The voltage is inductively applied by three-phase double-frequency power. In this paper, based on the field test of a 110 kV, 7. 5 MVA converter transformer applying voltage on single-phase and other phases supported, a new method is provided to measure the withstand voltage of ordinate insulation in the converter transformer by using present single-phase test equipment.