Research On Setting Of DC Protection In HVDC System

HVDC(high voltage direct current) transmission system has been developing vigorously in our country. DC protection is the core part of HVDC secondary system, which reliability determines the safety of dc transmission equipment and the stable operation of power grid directly, and its reliability mainly depends on the proper setting of protection value. Therefore, this paper studied on setting method of dc protection in HVDC system, which mainly includes the following contents:The difficulties of dc protection setting are analyzed, and the current setting method which is practical in engineering can be summarized into two steps, the first step is the setting of protection initial value, the second step is the evaluation of initial value to verify its correctness.In view of the current setting method of protection initial value has serveral problems, such as, the simulation workload of combined conditions is heavy, without considering the setting of delay time, a rapid setting method of dc protection initial value is proposed. This method takes into account the delay time, and proposes the fault location to be a subsection principle for multi section protection. Using the method of single influencing factor filtering one by one to combine fault conditions, which can filter out some factors or some types in a factor that have little effect, the nubmer of simulation is reduced, and the setting speed is improved. In addition, based on changed time window, the fault features of protection are extracted with abundant details. Taking valve short circuit protection as a typical example, the feasibility of this method is verified.In view of the low efficiency of the current evaluation method of protection value, a method is proposed based on customizable protecton modeling. This method makes model protection outside the EMTDC platform, to avoid the repetition of EMTDC simulation, and the action result of protection can be calculated by the way of batch processing in other platform, which greatly improves the work efficiency of the current protection value evaluation. Based on this method, a protection setting value evaluation software is developed to achieve customizable protecton modeling, still to take valve short circuit protection as example, the initial value of this protection is derived from the setting method of protection initial value which is proposed in this paper, the feasibility of this method is verified.