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

• Main Authors: Zehong Liu, Fuxuan Zhang, Jun Yu, Keli Gao, Weimin Ma
• Format: Article
• Language: English
• Published: Wiley 2018-12-01
• Series: High Voltage
• Subjects: HVDC power convertors; poles and towers; lightning protection; air gaps; power transmission lines; reactors (electric); flashover; arresters; bushings; HVDC power transmission; power transformers; ultra-high voltage DC transmission; direct current transmission demonstration project; theoretical analysis; converter stations; configuration scheme; lightning arresters; shielding angles; ground lines; switching impulse flashover characteristics; equipotential sphere; external insulation; heavy pollution areas; pole gap; electromagnetic parameters; international electromagnetic standards; reactors; converter valves; wall bushings; transmission technologies; geographical conditions; rod-plane air gaps; converter transformers; impulse flashover characteristics; switching overvoltage; conductors; current 5000.0 A; current 5523.0 A; voltage 800.0 kV; size 25.0 m
• Online Access: https://digital-library.theiet.org/content/journals/10.1049/hve.2018.5023

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.