Research on key technologies in ±1100 kV ultra‐high voltage DC transmission

Abstract

Based on completely mastering ±800 kV transmission technologies, the first ±1100 kV direct current (DC) transmission demonstration project is being constructed in China. Combining theoretical analysis and a large number of experiments, the margin of switching overvoltage in converter stations, the configuration scheme and performance of lightning arresters, the shielding angles of ground lines under different geographical conditions, and the maximum air gap of lines have been determined. The switching impulse flashover characteristics of equipotential sphere and typical rod-plane air gaps are also provided. The external insulation is designed differently for light, medium, and heavy pollution areas. For the ±1100 kV project, if the 8 × 1250 mm 2 conductors are applied, the pole gap is 26 m and the height of the line is 25 m, all the electromagnetic parameters will meet the requirement of international electromagnetic standards. The key design points of ±1100 kV converter transformers, smoothing reactors, converter valves, and wall bushings are researched and the 75 mH smoothing reactors, ±1100 kV/5000 A converter valves, and ±1100 kV/5523 A wall bushings are successfully made. The optimised hierarchical connection modes and coordination control measure of the ±1100 kV project are studied and the results can provide sufficient technical support for the demonstration project.

Surface‐modification effect of MgO nanoparticles on the electrical properties of polypropylene nanocomposite

“…Polymeric composite materials have been extensively applied in electrical insulation [1][2][3][4][5][6]. As the polymeric matrix, low-density polyethylene (LDPE) and cross-linked polyethylene (XLPE) were widely used in high-voltage direct current (HVDC) cable insulation because of their low permittivity and dielectric loss, high resistivity, decent mechanical flexibility and low cost [7][8][9][10]. However, the thermo-stability of LDPE cannot meet the higher temperature requirement of cable operation; XLPE has solved this problem by the cross-linking process, which made XLPE a thermoset material and introduced cross-linking by-products [11].…”

HVDC Transmission: Technology Review, Market Trends and Future Outlook

“…Asia has the highest average transmission voltage as many of its established HVDC links since 2010 are rated at ±800 kV, and lately up to ±1,100 kV using overhead transmission lines. Brazil has also recently inaugurated its first ±800 kV HVDC system for +2,000 km point-to-point power transmission at Belo Monte [51]. On the other hand, the maximum DC transmission voltage at any other location is currently limited to ±600 kV due to the moderate power rating and distance of the implemented projects.…”

Temperature‐dependent electric field distribution in ±800 kV valve‐side bushing insulation for a converter transformer

“…In particular, there are three types of fluids: air, SF6, and oil. Their density, heat capacity, and thermal conductivity are set as a function of temperature due to the fluid property [15]. Table 2 presents the detailed parameters of the aforementioned materials, and Table 3 presents the parameters of fluids for fluid‐thermal analysis [16].…”