Measures To Limit The Short Circuit Current Level Of Large Power Grids

With national economy persistently developing at high speed,electric loads are quickly increasing and the scale of electric networks are continuously extending,which result in 500kV electric network being step by step formed now.However,short circuit current levels of electric networks are also increasing because the electric magnetic meshed system between 220kV and 500kV is operated and the density of loads,electric networks and generations are intensifying.As a result of above phenomena,not only the security and stability of entire electric network but also construction and transmission capacity of electric network are directly impacted. So it is urgently necessary to research how to reduce short circuit current level of system.Based on analyzing the characters of framework,operation and short circuit current level in the 2015-year Zhejiang Power System,this dissertation studys the projects to reduce the short circuit current of the 2015-year Zhejiang Power System after analyzing and comparing the basic principles and traits of the different methods of limiting short circuit current;At the same time,the short circuit currents of the 2015-year Zhejiang Power System are computed after the projects of limiting short circuit current are carried out.The computing results shows that the short circuit current of the 220kV electric network can be effectively limited under reasonable short circuit current level depending on transformers neutral grounding by small reactance and bus splitting after the 500kV and 220kV electric networks of the 2015-year Zhejiang Power System are dispatched by levels and districts; And the short circuit current of the 500kV electric network can be also effectively limited under reasonable short circuit current level relying on changing framework of electric network and HVDC transmission system.