Arc Current-transferring Type Fault Current Limiter Based On High Speed Vacuum Switch

Based on the analysis of existing fault current limiter, simulation and experimental study of arc current-transferring type fault current limiter were carried out. A 10kV fault current limiter prototype was developed, which was successfully experimented in field experiments.A two dimensional(2D)finite element model is applied to analyze the dynamic characteristics of the electromagnetic repulsion mechanism. In order to verify the validity of the simulation results, a simplified electromagnetic repulsion mechanism is established. The discharge current and the contact time between metal tie rod and cushioning device are measured. A good agreement between the measurements and the simulation results is obtained. Detailed investigations are performed by simulation regarding the impacts of various structure parameters and capacity of energy storage capacitor on the dynamic characteristics of the electromagnetic repulsion mechanism. Two methods are put forward for increasing the opening velocity of the switch. Based on the simulation results, a 12kV-2500A/40kA high speed switch prototype with an electromagnetic repulsion mechanism and a disk spring mechanism is developed. It can open within 0.5 ms from the trip signal, and the travel time is 1.6ms.In order to verify if high speed vacuum switch arc current could extinct after the forced zero-crossing, the experimental study on limiting effects of the fault current limiter was carried out, by using a LC oscillation circuit to simulate the short-circuit current. During the process of experiments, the frequency and amplitude of the TVS branch current were changed to figure out if the limiting effect changed. Experimental results showed that, for short-circuit current within scope of 10～30kA (peak value), while the frequency of TVS branch current changed within 2600～8200Hz, the high speed vacuum switch could be zero-extinction, by injecting a reverse current large enough to force the current down to zero.Based on the work in the above, the design of fault current limiter was completed, including the decision of the internal parameters, and logic of protection and control. Addressing the emerged problems of the switch prototype during the experiments, simulation analysis was conducted, from which improvement measures were proposed, and the switch prototype was also improved. Because of the low trigger reliability and short lifetime of TVS, further experimental studies were carried out drawing on existing research results. Finally, a 10kV fault current limiter prototype was developed, and the on-site short-circuit current limiting test was conducted. Experimental results showed that the fault current limiter was effective in curbing the short-circuit current peak and RMS, and it also performed well on inhibiting the bus voltage drop.