Based on the superposition theorem and the symmetrical compoent method

the connection diagrams of Laplace transformation impedance for calculation of recovery voltages in three-phase symmetrical networks are deduced and some application examples by this method also presented in this paper. The calculated results of the first-pole-to-clear factors for three-phase earthed and unearthed short-circuit current interruption show that the factors in the actual networks are lower than that specified in the corresponding standards for high-voltage alternating circuit breakers.