Short-circuit current level of power transmission system may increase with high penetration of converter-type sources
and power equipment selection will be faced with higher requirements for dynamic and thermal stability. Three-phase short-circuit current expression of converter-type sources is obtained by analyzing measured short-circuit current waveform and its change rule of envelope line. According to current output characteristics presented by converter-type sources in different periods of fault
equivalent circuits of fault transient state and steady state are proposed. In power grid with converter-type sources
superposition theorem is used to calculate AC component and DC component of short-circuit current. Then the peak value of short-circuit current is evaluated effectively
and the calculation results can be used for grid planning as well as equipment selection. Finally
the calculation results of proposed method and conventional method are compared with that of electromagnetic transient through 6-node 500 kV Huainan power grid and 35-node 220 kV Huaisu power grid
then effectiveness of the proposed method is verified.