High Voltage Fault Current Limiter by Fast Switch with Multiple Breaks in Series

As the rapid increase of power grid capacity, the short-circuit current of the grid could be very large in some certain district, which may seriously harm the stability and safe operation of the system. To solve this problem, a fault current limiter with multiple high speed switches in series is proposed in this paper. The features include “one-drag-two” topology and high-potential installation of the electromagnetic repulsion driving mechanism, and isolation transformers are applied to achieve high-potential power supply. Therefore, the insulating pole of the switch can be cancelled, which helps reducing the weight of the moving contact, so that it is easier to realize quick opening and closing. Meanwhile, the problem that the current limiter which is powered by capacitive voltage transformer (CVT) is not able to operate when the system is not charged does not exist in the proposed scheme. In addition, the parameters of the repulsion mechanism are optimized for two coils series connected structure using 3D finite element simulation. Also, the stray capacitances between switches and the ground are extracted, and then the equalizing capacitances are decided to guarantee the uniformity of voltages on each switch. A test system based on LC oscillation is built to test and verify the proposed 220 kV fault current limiter prototype. The dynamic voltage sharing characteristics of the prototype during the transition of the short circuit current to the current limiting reactor are obtained. Furthermore, the opening tests of the prototype with different arcing time are carried out. The test results show that the series-connected fast switches are capable of breaking 40 kA short circuit current with DC component more than 80% in 3ms after receiving the breaking command.