Electrosurgical system and method for checking the electrical connection between a neutral electrode and a patient

A method for checking an electrical connection between a neutral electrode (23) and a patient, wherein the method comprises the following steps:

• attaching the neutral electrode (23) via at least one contact surface (34) thereof to the patient so that an electrically conductive connection exists between the neutral electrode (23) and the patient;
• applying a measurement signal (US, IS) respectively at multiple different measurement frequencies (ω) solely to the neutral electrode (23) at different times;
• determining an impedance actual value (Zist(ω)) for individual measurement frequencies (ω) of the multiple different measurement frequencies (ω) of the measurement signal (US, IS);
• checking the determined impedance actual values (Zist(ω)) based on a predefined check criterion, and
• initiating a measure depending on a result of the checking of the determined impedance actual values (Zist(ω));
• wherein the predefined check criterion is based on a frequency-dependent model impedance (39);
• wherein the frequency-dependent model impedance (39) provides multiple parameters to characterize the neutral electrode (23) including a spatial dependency of surface portions of the at least one contact surface (34) of the neutral electrode (23) that are electrically connected to the patient with sufficiently low resistance or that do not have an electrical connection to the patient with sufficiently low resistance.