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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]

A great progress in the electrical performance of high-temperature superconductor (HTS) REBCO tapes allows for a much increased transport current capability in cables especially at high magnet fields. This is of interest to future fusion magnet applications. A variant type of twisted stacked-tape cable called quasi-round twisted stacked-tapes conductor (QisTac) is proposed and developed for the superconducting conductor of the China fusion engineering test reactor. The stack of the twisted HTS tapes is wrapped by a tight spiral made with copper wires. The stack with the copper wire is, then, soldered to form the solid round conductor, which is reliable and easy to manufacture in long lengths. A QisTac sample with four REBCO tapes was prepared and measured at 77 K and in the self-field condition. The measurement result shows the expected critical current calculated from the individual tapes considering the self-field effect. The bending characteristic of the sample was also tested under different bending radii. The critical current is reduced by roughly 5% at 0.54% bending strain. Some residual bending strain is maintained when the maximal bending force is released. This result is promising, but reproducibility testing and tests at high field and current are needed for future high field application. [ABSTRACT FROM AUTHOR]

Sag is one of the important indicators for judging whether a transmission line is safe. The existing sag calculation method does not consider the temperature difference between conductor strands, causing the calculated results to often deviate from the values measured with a theodolite. In this article, a sag calculation method considering the temperature difference between strands is proposed. First, finite element analysis and experiments were used to analyze the temperature differences between each area and layer of the conductor when the wind blew the conductor, and then a correction calculation model for the conductor sag was proposed. Next, a sag monitoring system based on four-point temperature measurement was designed. Finally, the method was applied to a ±400 kV transmission line in Qinghai Province, China. The results show that after considering the temperature difference in the conductor strands, the error of the sag calculation result is much smaller than that without considering the temperature difference in the conductor strands, and the maximum relative error is reduced from 7.86% to less than 2%. [ABSTRACT FROM AUTHOR]

China Fusion Engineering Experimental Reactor (CFETR) is a major scientific project independently designed and developed by China and jointly with international cooperation. Engineering design and project infrastructure construction are currently underway. The design goal of CFETR is 1.5–2.0 GW fusion power, and the central magnetic field is up to 15 Tesla, which is much larger than the design parameters of ITER under construction in Europe. In order to achieve the desired high magnetic field, the pre-research of Bi-2212 high temperature superconducting CICC magnet was carried out. The performance test of Bi-2212 cable is the most direct criterion for the successful development of the cable. New cable performance judgment method is proposed because of the long test time and high test cost of sub-size cables. Two cables are manufactured, and one cable is disassembled into single wires for performance evaluation. If the performance of single wires is not significantly attenuated in comparison with the performance of single wires that have not been twisted, we will conduct the second cable critical current test. The test results show that the method of dismantling the cable test is feasible. It is also feasible for cables of different structures. This method can be used to judge the performance of the cable in advance. This method is only suitable for detecting damage in the cable manufacturing process. [ABSTRACT FROM AUTHOR]

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]

Condition monitoring and diagnosis (CMD) has proven effective in helping to ensure the safety of power grids. With development of the smart grid and ultra-high-voltage (UHV) transmission system, the demand for CMD systems has grown rapidly in China. In recent years many condition monitoring devices have been installed in the field, and much experience has been accumulated. At the same time, researchers and engineers have developed some novel sensors to overcome the drawbacks of the conventional devices. In addition, State Grid Corporation of China (SGCC) and China Southern Power Grid (CSG) have introduced more than 20 standards to regulate CMD systems in the field. In this paper some widely adopted and novel CMD devices specific to power transformers, gas-insulated systems (GIS), overhead transmission lines, and power cables are described, and the trends in CMD development are discussed. [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]