A wind turbine fault detection circuit 200 and method is disclosed herein. In a described embodiment, the wind turbine fault detection circuit 200 comprises a magnetometer in the form of a hall-effect sensor 202 coupled between a power converter 108 and a ground element 204 of the power converter 108 and configured to measure a ground current from the power converter to obtain a real ground current Ig; and a comparator 206 configured to determine presence of a fault based on the real ground current Ig.