PT (potential transformer) loop disconnection detection method for shutdown state generator rotating speed measuring device

The invention provides a PT loop disconnection detection method for a generator rotating speed measuring device in a shutdown state, and the method comprises the steps: adding a 20Hz low-frequency power supply to a generator in a shutdown state based on an existing injection type stator grounding protection device, and coupling the 20Hz low-frequency power supply to a generator end through a generator neutral point grounding transformer; a plurality of PT speed measurement loops and a plurality of fluted disc speed measurement loops in the generator rotating speed measurement device are controlled, and the frequency of inter-phase voltage between every two phases in the PT loops at the generator end is measured; and comparing the frequency of the inter-phase voltage between every two phases with a preset frequency difference threshold value, and determining a target phase with a broken line fault in a PT loop for the generator rotating speed measuring device according to a comparison result. According to the