On July 2, the "Key Technologies and Engineering Application of 550 kV Epoxy Paper Impregnated Bushings on the Grid Side of Converter Transformers" led by the DC Technology Center of the State Grid Corporation of China passed the technical achievement appraisal organized by the Chinese Society for Electrical Engineering.
The appraisal committee listened to the project's work report, technical report, development report, economic benefit analysis, product inspection report, installation test and operation report, and scientific and technological novelty report, and reviewed relevant technical data. After questioning and answering questions, research and discussion, the experts at the meeting agreed that the grid-side epoxy resin-impregnated bushing of the converter transformer developed by the project has the characteristics of small partial discharge, low temperature rise, high safety performance, and strong interchangeability. The overall technology of the project has reached the international leading level.
Most domestic high-voltage bushings on the grid side of converter transformers are oil-impregnated paper-insulated bushings. This type of casing has a high defect rate, and the main forms of defects are oil leakage, capacitor core discharge, abnormal internal gas production, and abnormal current-carrying connection components. Such defects will not only increase the workload of transportation and inspection, but also pose risks to equipment and personal safety.
Compared with oil-impregnated paper casing, epoxy resin-impregnated paper casing has no insulating oil inside, and there is no problem of oil leakage and abnormal gas production of insulating oil. In addition, the epoxy resin-impregnated paper sleeve core is flame-retardant and anti-explosive, eliminating the risk of cracking of the oil-side porcelain sleeve.
In order to take advantage of the advantages of epoxy resin-impregnated paper bushings and to solve various problems in oil-impregnated paper bushings at the same time, the State Grid DC Center has organized relevant units to start the "550 kV epoxy resin on the grid side of converter transformers" since 2017. "Key Technology and Engineering Application of Resin Impregnated Paper Sleeve" project. After nearly three years of technical research, the project team has developed and mastered the 550kV epoxy on the grid side of the converter transformer in response to the special technical requirements of high rated current, high harmonic content, and high operating temperature of the grid-side epoxy resin-impregnated paper bushing. The key technology for the design and manufacture of resin-impregnated paper sleeves has formed a series of domestically-made independent intellectual property rights; a large amount of research data has been accumulated by conducting electrical, thermal and mechanical performance verification tests on 550kV epoxy resin-impregnated paper sleeves It provides an important reference basis for the design and development of higher voltage grade epoxy resin impregnated sleeves.
At present, the epoxy resin-impregnated paper casing developed by this project has passed the routine test and type test of the third-party quality inspection agency, and its performance indicators are better than the requirements of the relevant standards. There are three casings within ±800 kV Yibin The network is connected to the Tianshan converter station and the operation is in good condition.
