In low-voltage distribution networks with distributed photovoltaic (PV) integration, residual current waveforms are complex and their amplitudes vary randomly. This often leads to frequent maloperation of existing residual current protection devices, making them difficult to apply effectively. To address this issue, a dual-criterion approach is proposed, combining the ratio of the mutation values of residual current and repeated grounding current with the residual current setting threshold. First, the composition and variation of residual current in a TN-C-S system with PV power supply under electric shock faults are analyzed, considering increasing numbers of repeated grounding points and loads. Based on this, a threshold for the ratio of the residual current and repeated grounding current mutation is established as fault detection criterion. Then, the influence of repeated grounding points on the diversion of electric shock current is examined, and a method for fault location is proposed using the average value of the mutation ratio. Simulation results verify that the proposed criteria can accurately detect electric shock faults, demonstrate strong anti-interference capability, effectively reduce maloperation of protection devices, and achieve accurate positioning of fault sections under different fault positions.