Along with the growth of world energy consumption and the increase of renewable energy supply,
the scale of power grids needs expanding and the structure of power networks needs strengthening.
Although transmission capacity is improved and energy demand is satisfied by means of transmission network expansion, redundant and parallel transmission lines make synchronous interconnected AC power systems excessively compact
The compacter the power grid is, the greater the short circuit currents will be.
This improper power system planning directly leads to the rapidly increasing short circuit currents, which threatens the security of electrical energy transmission and poses great challenges for power grid operations.