Study on the Operational Equation for Valve Short Circuit Protections in HVDC Projects

As the primary protection for high voltage direct current(HVDC) converters,there are two kinds of typical operational equations for valve short circuit protections.Differences between the two kinds of operation equations were studied.Based on analyzing the character-istics of the currents under various converter faults,the performances of the two operational equations were compared.Furthermore,one of the operational equations was revised to have the function of locating faulty bridge.To coordinate the contradiction requirements of selectivity and sensitivity in protection settings,a setting function was proposed according to the analysis of existent setting functions.Then the protection setting method was described.The short-circuit faults in the converter and some outside the converter were tested with CIGRE HVDC Benchmark Model and the validity of the theoretical analysis was verified.