Physical properties of single-electron devices in the week Coulomb blockade regime are significantly dependent on non-perturbative effects. They arise as instanton solutions equations motion for corresponding Ambegaokar-Eckern-Schoen action. In equilibrium those known Korshunov instantons. this paper we study non-equilibrium Ambegaokar-Eckern- Schoen action using Keldysh technique. We found ins...