PURPOSE: To improve the simulation accuracy of the voltage characteristics of load by providing constants for the constant power characteristic, constant current character istic and constant impedance characteristic of the load and executing simulation of the load characteristics by taking all these characteristics into consideration.

CONSTITUTION: The simulation of the voltage characteristics of the load is executed by using the equation; load value = load base value.[α+β.(V/VO)+γ.(V/VO)] in a load simulating means 6. In the equation, α: the constant for adjusting the load characteristic (constant power characteristic), β: the constant for adjusting the load characteristic (constant current characteristic), γ: the constant for adjusting the load characteristic (constant impedance characteristic), V: a current voltage: VO: an initial voltage. The simulation of the voltage characteristics of the load by taking the constant power characteristic, constant current characteristic and constant impedance characteristic of the load into consideration is executed by using this equation. The voltage VO is the load voltage at the time of starting training. The voltage V is the value calculated by a means 5 for responsive simulation of the electric power system. A load simulating system 6 preserves the load state simulation by this equation in a simulator data preserving area 4 and is displayed via the device 1.