A method of detecting a leakage current in an electrosurgical system operating at a high frequency includes: coupling an RF generator to a pair of RF output leads via an electrical interface, the RF generator having an operating frequency； inducing a test signal at an output of the electrical interface, the test signal having a test signal frequency that is less than the operating frequency； and monitoring for a presence of an induced common mode current that would indicate the presence of leakage current.
