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The development of new technologies in power generation and application, together with the demand for the reliability and capability of power supply has drawn increasing attention to dc distribution and microgrid technology. This paper introduces the renovation project for a single-circuit XLPE cable line being converted into dc operation after its second failure under 35 kV ac. This is the first time ever in China for this type of system conversion, in which the existing XLPE cable line was put into operation in a bipolar voltage-source converter (VSC) dc system of 10 kV voltage and 150 A current to maintain its 3 MW capacity. The test methods for cable performance that were checked under the designed dc scheme were put forward and conducted on sectioned cable samples. After the cable test and equipment installation, the line was put into operation under the VSC dc topology in 2011. It has now been running for four years without any interruption. Compared with other alternatives for ac operation, this proposal shows advantages in aspects of economy, reliability and engineering. Besides, the theoretical evaluation suggests that the system capacity can be further increased by four times, and the first step is underway for that goal. [ABSTRACT FROM PUBLISHER]

In order to solve the frequently occurring lightning flashover problems on ±500 kV dc transmission lines in China, the authors have conducted the research on the dc line arrester since 2011. In this paper, the structure and installation, technical parameters, and protection performances, as well as their deterministic processes of the arrester are presented and analyzed in detail. In 2013, the authors successfully developed the arrester products, and the type tests show that they have excellent performance parameters and can act effectively against the lightning impulse and cutoff the dc follow current. By now more than 500 dc line arresters have been installed and used on seven ±500 kV dc transmission lines in eight provinces of China. About four years of operating experience shows that the arresters work safely and reliably over a long period of time, and have been effectively reducing the lightning flashover rate of the ±500 kV dc lines. [ABSTRACT FROM PUBLISHER]

An investigation into the effect of surface roughness on corona discharge for a 30-year operating conductor in the first 500-kV transmission line in China is presented. Many substances were found to adhere to the conductor surface. Corrosion and deposits had rendered the operated conductor surfaces much rougher than those of the new one. The results show that surface roughness has a significant impact on corona discharge, and the corona inception voltage of the operated conductor would be reduced while the audible and radio noise would be increased. [ABSTRACT FROM AUTHOR]

Ice-clad transmission lines can seriously damage a power grid, causing a partial or entire breakdown. De-icing the transmission line is a good method to prevent recurrence of such a situation. The development of dc de-icing technology can make difference in power grids preventing an ice disaster. Based on the calculation, analysis, and tests in the artificial climate chamber of the conductor de-icing parameters, the dc de-icing technical scheme for the typical transmission lines at various voltage levels in China Southern Power Grid is proposed. Two economical and practical topological structures of the dc de-icer have been proposed, and the prototypes have been developed and tested in the field successfully. Then, the defensive strategy of the power grid for ice disaster based on dc dicers is proposed. The application during the icing season of 2009–2012 in China shows that the dc de-icing method is an effective means to prevent an ice disaster in the power grid. [ABSTRACT FROM AUTHOR]