The invention relates to a method for insulation fault location in an IT power supply system, comprising the process steps: feeding of a test current, detecting of a test current portion in a branch of the IT power supply system and evaluating the detected test current portion. Furthermore, the invention relates to an insulation fault location for an IT power supply system having a test current generator for supplying a test current, having a test current sensor for detecting a test current portion in a branch of an IT power supply system and having an analyzing device for evaluating the detected test current portion. According to the invention, the insulation fault location system comprises a computing unit for adaptively determining a test current parameter of the test current depending on an electric system parameter of the IT power supply system.