PURPOSE: To obtain a parallel breaking test circuit for a breaker with a simulated parallel breaking of the breaker, by connecting shunt auxiliary inductances each having a surge impedance matched with a specified value in series to sample breakers, which are connected in parallel.

CONSTITUTION: A capacitor A14a for adjusting surge impedance is connected in parallel to a shunt auxiliary inductance A13a while a capacitor B14b for adjusting surge impedance is connected in parallel to a shunt auxiliary inductance B13b. A sample breaker A7a and a shunt auxiliary inductance A13a connected in series are connected in parallel to a sample breaker B7b and a shunt auxiliary inductance B13b likewise connected in series and then, connected in parallel to a voltage source circuit 16. Thus, various characteristics during parallel breaking of breakers are determined with an equivalence circuit having a specified surge impedance made up of the sample breaker s 7a and 7b, the shunt auxiliary inductance 13a and 13b and the capacitors 14a and 14b for adjusting surge impedance.