A method of controlling an electrosurgical system is described, the system including an electrosurgical generator and an electrosurgical instrument connected to the generator by means of a cable. A radio frequency signal is supplied to the electrosurgical instrument at an operating frequency, and the voltage of the radio frequency signal is monitored at a frequency corresponding to the frequency of a resonant circuit established by the electrosurgical instrument together with the cable. The monitored voltage is capable of indicating the initiation of arcing from the electrosurgical instrument, such that the voltage of the radio frequency signal can be adjusted in response to the monitored voltage at the resonant frequency. The magnitude of the monitored voltage is an indication of the degree of arcing. An electrosurgical system including an arc detector is also disclosed.
