A portable cutting tool with movable cutting member, equipped with an active protection system, comprising at least - stopping means of said cutting member, - a control and processing unit apt to trigger said stopping means upon the detection of a danger condition, - a proximal electrode electrically coupled with a handle of said cutting tool and a distal electrode electrically coupled with said cutting member, the two electrodes acting as ideal contacts of two ideal armatures of a capacitor, said control and processing unit being arranged to feed an electric output signal into one of said electrodes and to detect an electric input signal on the other one of said electrodes, characterised in that said control and processing means include transmission means having the function of feeding said electric output signal modulated at said at least two different frequencies, a detection unit is also provided which is arranged to detect complex impedances of said ideal armatures of a capacitor by detecting said electric input signal at said at least two different frequencies, and said control and processing unit being arranged to determine a danger condition and to cause triggering of said stopping means based on a value of the magnitude of said complex impedance and on a phase difference of said complex impedance at said at least two different frequencies. - stopping means of said cutting member, - a control and processing unit apt to trigger said stopping means upon the detection of a danger condition, - a proximal electrode electrically coupled with a handle of said cutting tool and a distal electrode electrically coupled with said cutting member, the two electrodes acting as ideal contacts of two ideal armatures of a capacitor, said control and processing unit being arranged to feed an electric output signal into one of said electrodes and to detect an electric input signal on the other one of said electrodes, characterised in that said control and processing means include transmission means having the function of feeding said electric output signal modulated at said at least two different frequencies, a detection unit is also provided which is arranged to detect complex impedances of said ideal armatures of a capacitor by detecting said electric input signal at said at least two different frequencies, and said control and processing unit being arranged to determine a danger condition and to cause triggering of said stopping means based on a value of the magnitude of said complex impedance and on a phase difference of said complex impedance at said at least two different frequencies. said control and processing means include transmission means having the function of feeding said electric output signal modulated at said at least two different frequencies, a detection unit is also provided which is arranged to detect complex impedances of said ideal armatures of a capacitor by detecting said electric input signal at said at least two different frequencies, and said control and processing unit being arranged to determine a danger condition and to cause triggering of said stopping means based on a value of the magnitude of said complex impedance and on a phase difference of said complex impedance at said at least two different frequencies.