Development of compact 250 kV DC filter for HVDC converter station

As a preliminary step toward the realization of compact converter station equipment for 500 kV HVDC transmission, a prototype of high-reliability, economical, compact 250 kV DC filter equipment is developed and its performance confirmed by a long-term in-service test. The compact dead-tank-type design reduces the installed area and height and the equipment weight to 1/12, 1/3 and 2/3 respectively, of those of the existing design. The size reduction of the capacitor unit is achieved by the use of a wide paper-film dielectric specifically developed for DC filter application and by housing bare capacitor elements in a dead tank and impregnating them with aromatic hydrocarbon oil. For further size reduction, the surge-absorption capacitor is housed in the same tank