Short circuit and collapsing bus voltage analysis of vital instrumentation and control power supply distribution in nuclear power generating stations

It is a common practice to utilize regulated power supplies in Vital Instrumentation and Control Power Systems (VICPS) to meet the requirements of IEEE Std. 308 in nuclear power generating stations. Most of these power supplies have current limiting features. Consequently, for a short circuit in a distribution system feeder, it is necessary to factor the performance characteristics of the current limiting device into the analysis. The method of fault analysis described in this paper differs from traditional fault analyses that assume a constant prefault voltage up to and including circuit interruption. The analysis presented within specifies that the drop in output voltage of the current limiting device must be determined to calculate the magnitude of fault current that would be present at the time of interruption of the circuit by the fault clearing device. Computational approaches are developed to address these features to ensure a realistic determination of expected fault current at the time of circuit interruption. A review of the performance features of Inverters and Ferroresonant Transformers is also presented