Relevant Theoretical And Experimental Research On Synchronous Vacuum Switches

Synchronous switching, also called phasing switching, is used widely in electric power system to control and reduce switching transients, increase the interrupting capacity of switches, improve the reliability of electric power system and customer power quality. Many people have paid attention to the research and application of synchronous switching. In order to apply the technique of synchronous switching in our country, some theoretical and experimental research works on the fundamental of synchronous vacuum switches and its application of synchronous interruption short circuit currents and synchronous switching shunt capacitor banks are presented in this paper.Synchronous switching requires that operating times of switches retain stable in long term and have small mechanical scatters. Firstly, based on the compares with the conventional spring or electromagnetic actuators, synchronous vacuum switch with permanent magnetic actuator(PMA) and electronic control is proposed and some analysis of its control characteristic, control accuracy and reliability are performed. PMA with electronic control has some advantages including smaller number of mechanical movable parts, stable operating times and controllable motion of the poles. PMA with electronic control can ensure the contacts always close or open at the expected instant and provide foundation for implementing synchronous switching.Synchronous interruption of short circuit currents can increase the actual interrupting capacity and electrical lifetime of vacuum switch.Less results of short gap vacuum arcs when interrupting fault currets have been presented in the existing theories of vacuum arcs. So, the analysis of the dielectric recovery characteristic of short vacuum gap when synchronized breaking short circuit currents is performed, and a vapor density model is applied under the special boundary conditions to get some relations between arcing time and vapor density, the dielectric recovery time. And the analysis results show short arcing times corresponding short vacuum gap can reduce arcing energy the contact is subjected to, decrease the recovery time and minimize contact erosion. And a series breaking tested have been performed and the test results show a critical time of 2.5ms and the critical gap distance of 3.2mm for a commercial interrupter(12kV/25kA),which can provide some experimental proofs for implementing synchronous switching of short circuit currents.It is important for synchronous interruption to have accurate measurement, fast detection of fault currents and fast determination of the optimal tripping moment. A novel printed circuit board(PCB) Rogowski coil current transducer is designedto measure fault currents accurately and its static and transient response performances are measured and simulated. The results show the transducer designed can satisfy the requirements of synchronous interruption. For synchronous short circuit interruption, the fast detection of fault current is a key issue. A fast detection unit based on transient components is designed and simulated. The simulation results show the detecting time can be less than 1ms. In order to provide a fast determination of optimal tripping instant to achieve minimal contact erosion, a quick detection approach based on linear adaptive neurons called Adaline for fault current parameters and the moment of arc extinguishing at current zero is presented.Synchronous energizing or de-energizing shunt capacitor banks is one of the main applications of synchronous switching. The effects of the connection of three phases shunt capacitor banks and the selection of the reference voltage on synchronous control tactics are investigated and the synchronous switching tactics are presented. Whether or not obtaining expected effects of synchronous switching shunt capacitor banks mainly depends on the detection accuracy of zero points of the reference signal and the consistency of operating times of circuit breakers. So it is important to minimize the control error caused by the reference phase and the variat...