Circuit breaker for protecting an electrical system comprising a mains supply line in alternating current, at least one electrical load and the circuit breaker, said breaker comprising: - a semiconductor switching element having a first and a second electrical terminal connected to the mains supply line and a control terminal, said switching element being controlled by enabling/disabling a control signal applied to the control terminal for switching between an open/closed status and a closed/open status for connecting/disconnecting at least one load to/from said supply line; - a drive adapted to enable/disable said control signal, - a current limiting circuit operatively associated with the mains supply line configured for sending a first signal to said drive for disabling said control signal switching the switching element from the closed status to the open status subsequent to the detection of a current value (Icc) indicative of a failure in the system; - a voltage regulator circuit (300, 400) connected to said first and second electrical terminal of the switching element characterized in that the voltage regulator circuit (300, 400) comprises: dissipation means of a residual electrical energy stored on the mains supply line subsequent to the switching of the switching element from the closed status to the open status due to the detection of said failure current (Icc), means for detecting a failure voltage between said first and second terminal generated by peak values of the failure current (Icc) at said switching of the switching element from the closed status to the open status, wherein said detection means are configured for sending a second signal to said drive for keeping said control signal disabled. - a semiconductor switching element having a first and a second electrical terminal connected to the mains supply line and a control terminal, said switching element being controlled by enabling/disabling a control signal applied to the control terminal for switching between an open/closed status and a closed/open status for connecting/disconnecting at least one load to/from said supply line; - a drive adapted to enable/disable said control signal, - a current limiting circuit operatively associated with the mains supply line configured for sending a first signal to said drive for disabling said control signal switching the switching element from the closed status to the open status subsequent to the detection of a current value (Icc) indicative of a failure in the system; - a voltage regulator circuit (300, 400) connected to said first and second electrical terminal of the switching element characterized in that the voltage regulator circuit (300, 400) comprises: dissipation means of a residual electrical energy stored on the mains supply line subsequent to the switching of the switching element from the closed status to the open status due to the detection of said failure current (Icc), means for detecting a failure voltage between said first and second terminal generated by peak values of the failure current (Icc) at said switching of the switching element from the closed status to the open status, wherein said detection means are configured for sending a second signal to said drive for keeping said control signal disabled. dissipation means of a residual electrical energy stored on the mains supply line subsequent to the switching of the switching element from the closed status to the open status due to the detection of said failure current (Icc), means for detecting a failure voltage between said first and second terminal generated by peak values of the failure current (Icc) at said switching of the switching element from the closed status to the open status, wherein said detection means are configured for sending a second signal to said drive for keeping said control signal disabled.