Study on Structure Type and Operation Condition of UHVDC Wall Bushing

Abstract

Abstract When the ±800kV UHVDC capacity is increased to 10000MW, the transmission current is 5kA and 6.25kA, which will put forward new requirements for the key technology of UHVDC through wall bushing: in UHV level, the key of through wall bushing lies in the research of basic technology of voltage sharing and field sharing. In the case of large current carrying capacity, the key lies in the basic technology research of current sharing and heat sharing. When the DC wall bushing, converter bushing and outgoing line device operate at the rated voltage, the central conductor is heated due to the carrying large DC current. Therefore, the temperature field distribution inside and at the tail of the bushing core is uneven, and the resistivity is the function of temperature, resulting in the change of resistivity with temperature and the change of potential and electric field distribution with resistivity during operation. Therefore, under the above high current operation conditions, in-depth key technology research is required for the design of bushing current carrying device, calculation of internal potential and electric field distribution, voltage sharing, field sharing, current sharing and heat sharing technology. The combined action of electrical and thermal stress will significantly affect the internal electric field distribution of converter transformer core and accelerate the aging rate of core composite insulation material, which introduces new research topic for the key technology of UHVDC converter bushing. The electric field and voltage distribution of UHVDC bushing are theoretically analyzed, the insulation structure is optimized from the aspects of material and structure, and the manufacturing process and the test technology are deeply and systematically studied.