Study of intelligent control device for circuit breaker controlled interrupting short circuit currents

An Intelligent control unit (ICU) is developed based on a field-programmable gate array FPGA and a digital signal processor DSP for the controlled interruption short circuit currents of high voltage circuit breakers. The sample value messages which meet with IEC61850-9-2LE protocols are received and decoded by the FPGA, at the same time a synchronization method is used to reduce the effects of network transmit delays on the performances of controlled interruption short circuit currents. Then the parameters of short circuit currents are estimated based on the least mean squares(LMS) algorithm and the receive sample values. The dichotomy algorithm is used to obtain the zero crossing of the short circuit currents as targets for synchronizing the tripping command to the circuit breaker so as to achieve a pre-determined optimum arcing times. Finally, a setup is made to verify the performance of the intelligent control unit and the algorithms, and the testing results show that the intelligent control unit for the high voltage circuit breaker is able to quickly realize controlled interruption the short circuit currents, and the performance meet with IEC62271-302 requirements to control accuracy in controlled switching, and the prediction errors of the short circuit current zeros are less than ± 1ms.