Large Grid Short-circuit Current Limiting Measures

With the expansion of power system, short-circuit current is increased year by year, which has become a serious problem for the planning and operation of power system. Besides, a heathier power market will set higher standards for transmission capability and reliability of power gird. Therefore, to effectively control the level of short-circuit current and find reasonable and economical limitation methods is one of the big challenges standing on the way of power system development.Aiming to effectively control the short-circuit current level for the whole power network, a mathematical model is built to find limitation solution with lowest investment, taking several different methods into consideration and using Genetic Algorithm to search for the global optimal solution. Tests on the 18-bus system show that the model is effective and reasonable.Based on the characters of framework and operation in the planning network of Ningxia province from 2008 to 2020, both of the increasing trend and deep-rooted causes for short-circuit current are analyzed; Taking the construction and development of 750kV electrical network in Ningxia province as background, thesis researches the measures which can limit short circuit currents. Simulation results show that: to adopt high impedance transformer can bring notable decrease of short-circuit current at the adjacent area of the 750kV substation; dispatching by levels and districts will be the best method to control short-circuit current globally as the 750kV power network becomes robust; to improve the interrupting capacity for some breakers which are too low and become the bottleneck for power system development is necessary; line-cutting can be a temporary measure; for 2020-yeat gird, installation of series rector is useful to reduce short-circuit current as a local limitation mothod.From the angle of measures' global effectiveness, continuity, limitation solution from 2008 to 2020 are put up, with reconstruction network being the first choice and change transformation devices being the second choice. Solution I aims to reduce short circuit current, and Solution II can not only realize short circuit current control, but also improve the capability of power system to operate in the condition of larger short circuit current. Their validity is proved by calculation.