Research of vacuum switching tubes for converters of Static VAR Compensators

Static VAR Compensators (SVC) on the basis of semiconductor devices have been developed and introduced in power industry and in transmission lines. SVC provide control of active and reactive power in the system. SVC are based on converters and operate at voltage level 35 - 110 kV. Researches and development in FGUP VEI of high-voltage vacuum switching tubes with small power losses has allowed to start creation of the experimental converters of the static VAR compensators (SVC) on the base of vacuum tubes. A number of advantages of vacuum switching tubes in comparison with semi-conductor valves is stimulated researches in this direction. The advantages of vacuum switching tubes evolves high dielectric strength of the individual tubes (200kV and above), short switching time (fraction of microsecond), full current controllability, stability to breakdown, stability to electromagnetic interferences, an opportunity to work at high temperature. The basic disadvantage of vacuum tubes is limitation on a current and the high internal resistance of the tube in the open condition. Development of switching tubes of high power carried out in FGUP VEI has shown, that their internal resistance can be essentially reduced due to use of a high voltage on an control electrode (grid) with the subsequent deceleration of electrons flow on the anode. As far as power losses in the tube should be minimal it is necessary to form electron flow into the beam. Such tubes were named electron beam valves (EBV), and they can operate as switches of power converters. In this paper creation of powerful switching tubes for power electronics and development of the experimental converters on their basis are considered.