Research On Controlled Vacuum Switches And Their Applications

Controlled switching, also called synchronous switching or phasing-control switching, is a terminology applied to the principle of coordinating the instant of opening or closing of a circuit with specific target point on an associated voltage or current waveform. Controlled switching has become an economical solution and commonly used to reduce switching surges. It is one of the advanced subjects of intelligent apparatus. This paper lays a strong emphasis on controlled capacitor switching, and represents the development and application of controlled switcing. The main contents are composed of controlled switching principle, design and realization of controlled switching system (CSS) based on Digital Signal Processor (DSP) and vacuum switch with permanent magnetic actuator (PMA), system tests of CCS, intelligent reactive power compensation with controlled switching technology and elimination of inrush currents by controlled switching unload transformer. The obtained results in this theis supply references to future research.Capacitor banks' switching for reactive power compensator is the most common application of controlled switching. The paper analysizes transient phenomena of traditional capacitor switching and presents controlled switching strategies of capacitor banks with different connection types. Important requirements for controlled switch, such as mechanical characteristics and electrical characteristics, are reviewed. In fact, the making instants do not coincide with the predefined target instants because of pre-strike and mechanical scatter. Thus a math model is established to determine the optimum closing target and maximum pre-stike voltage using the closing characteristic and the statistical deviation of the closing time. In addition, the applications for transmission line, reactor bank, unload transformer and fault current are introduced with three sides of switching transients, controlled switching strategy and applied effects.PMA has small mechanical scatter due to its fewer moving parts, and its output characteristics can perfectly match vacuum switch. PMA has been used more and more widely. Controlled vacuum switch is supplied with independent-pole operated PMA, and capacitor discharge supply can be chosen in the PMA exciting circuit. Thus the operation is controlled by high-current power electronic devices, and the control precision can be easily improved to some microseconds. The effects on operating times by mechanical factors including the contact wear of the switch and environmental changes like temperature should be considered. An algorithm is given by use of principle of bilinear interpolation and...