The Study Of Fast Making Switch For Synthetic Making Test Circuit Under Full Voltage

Although synthetic test method has been widely applied in breaking test of circuit-breaker, as synthetic making test under full voltage, it has been relatively less studied and applied. Besides the economic effect, the another greater important reason is that the validity of synthetic making test has brought higher requirements to the closing devices of current source and time precision of control system. In order to meet the equivalent performance with a direct test, it is recommended by international standard of IEC and national standard of China that the current source of a synthetic making test should be switched on to the tested circuit-breaker within 300 microseconds. So, the key device of the synthetic test circuit is a fast current making switch, which could withstand high static voltage and make high short-circuit current.Firstly, a general introduction of domestic and foreign situation of study and applications of synthetic making test is presented in the paper, then a brief introduction of fast making switches. According to the test condition of electric power test station in existence in China, a type of fast making switch system, based on triggered vacuum switch is proposed. To meet with the demand of high voltage class for isolation, the switch system is constituted by several modules, each of which has a TVS and a fast vacuum circuit-breaker (FVCB) with the same voltage class connected in parallel. TVS is applied to control the fast switching time on the making current accurately, and it has a delay-time conduction of several microseconds. FVCB acts as an auxiliary switch to protect TVS, and gets the same making instruction , together with TVS, from the control system. With the closing of FVCB, the making current of current source shifts from TVS to FVCB to reduce the ablation of the TVS contacts and to prolong its life. Then, the mathematical model of the process of the single module of the fast making switch is modeled, and the process of the current shifting from TVS to FVCB is analyzed and simulated with EMTDC/PSCAD, which is a software for electric power system. The result of simulation shows that, the short-circuit current can shift from the TVS branch to the FVCB branch successfully to achieve the original intention of the paper.The emphasis of the paper is the basic constitution parts of the fast making switch: TVS and FVCB. First, the triggered characteristic of TVS, which is the main control device of the fast making switch, is investigated, and the interval from the making signal to the conduction of main gap of TVS is about 86 microseconds in the experiments. Then FVCB, based on an advanced permanent magnetic actuator is designed and developed, which has a closing timeof about 8 milliseconds in the experiments, then a simulation of dynamic characteristic is calculated with ANS YS and MATLAB, and the results of simulation and experiment are well matched.Finally, the fiber control circuits of TVS and FVCB is introduced in the paper. And the results of practical operations proved that, the circuit can accomplish the control functions as expectance, and solve the problems of electromagnetic interruption and the isolation between the high-voltage test circuits and low-voltage control circuits.