Research On Three Phase Controlled Fault Interruption

Controlled fault interruption (CFI) is a terminology applied to the principle of coordinating the instant of opening of a circuit with specific target point on the fault current. It’s an effective solution for reducing arcing time so as to improve the breaking capacity and extend life span of the breaker. In the international, CFI is still being studied and there has no engineering application up to now.The key technology of CFI is fast and accurate fault parameters estimation. Researches and simulation analyses are put on some existing algorithms for parameters estimation. Based on the comparison between the algorithms, an improved least square method is chosen. The simulation results show that the method can get a predicted zero-crossing point in15ms with less than0.25ms error in the environment of30dB noise.A rapid fault inception detection method is proposed. It was also proposed the method to identify the fault type and the whole CFI strategy. In order to verify the whole CFI scheme, simulations based on sets of fault recorder data are done, and the results show that the proposed scheme can detect fault in2ms, and get a predicted zero-crossing point with less than0.25ms error when the relay protection acts.At last, a CFI system based on FPGA was developed. A test was put on with the relay protection testing device as fault generator, and the results show that the system can fulfill basic requirements of controlled fault interruption.