The current situation of dense power supply and large voltage level difference in northwest power grid is easy to cause short-circuit current overshoot. The commonly used current limiting measures will increase the attenuation time constant of the DC component of the short circuit current and affect the breaking capacity of the circuit breaker. This paper presents a simplified model of electromagnetic transient in the case of short-circuit in a complex multi-node power grid with large voltage level difference and intensive power supply in northwest China. On the basis of this model, the influence of DC component on the breaking capacity of circuit breakers is studied, the method of time constant conversion of DC component of short-circuit current is analyzed, and the restraining effect of resistance superconducting current limiter on short-circuit current of overstandard factory station is calculated. The results show that the decay time constant of the DC component needs to be converted to the test base value specified in the standard; Resistive superconducting current limiter can reduce the DC component time constant of the short-circuit current in the circuit near the installation location by about 25%, but it has a weak inhibition effect on the plant station with a long electrical distance. The conclusions in this paper can provide reference significance for the rational selection of circuit breakers and the application of new current limiting technology.