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This study explores the feasibility of applying inductive filtering technology to high-voltage direct-current (HVDC) transmission system since only filtering in the net side may lead to a lot of harmonics in the converter transformer. Basic principles of inductive filtering technology are presented and detail analyses are discussed from the aspects of filtering, vibration, commutation, short circuit, and AC system strength. Simulations and experimental tests show that when inductive filtering technology is applied, most of the harmonics do not enter the net side of the converter transformer but are directly filtered in the valve side. Thus, the harmonics flowing in the converter transformer reduce and the vibration of the converter transformer becomes smaller. The commutation reactance decreases sharply which greatly reduces the overlap angle and improves the commutation characteristics. Moreover, the short-circuit reactance almost keeps unchanged and the short-circuit characteristics do not deteriorate, and so the requirement for the AC system strength is much lower. This study finally concludes that applying inductive filtering technology to the HVDC transmission system is feasible, based on a successful engineering application in the high-power rectifier system.

The shielding tube and stress cone of the intermediate joint of XLPE cable accessory make the potential distribution along the insulation surface linearized to optimize the electric field and. By establishing the finite element model of the intermediate joint of 10kV cable accessory, the electric field distribution of different structure shielding tube and stress cone in different position of the joint is simulated and analyzed. The results show that the structure of shield tube and the position of stress cone are also a parameter characteristic which can not be ignored in the design, and they have a great influence on the distribution of the field strength of the intermediate joint. On the basis of finite element analysis, the optimum shape of shield tube and the best position of stress cone are obtained by comparing and analyzing the variation law of electric field intensity.