Abstract: The small resistance grounding system is at risk of maloperation for the zero-sequence overcurrent protection on the feeder and the line selection device at the main station when a high impedance grounding fault occurs. To enhance the capability of small resistance grounding systems to withstand transient resistance, a detection method for high impedance grounding faults based on periodic differential energy and waveform self-similarity is proposed. Firstly, the characteristics of single-phase grounding faults in the small resistance grounding system are quantitatively studied, and the reasons for the maloperation of zero-sequence overcurrent protection and the line selection device are analyzed. Subsequently, the periodic differential energy of zero-sequence voltage is used for preliminary detection of various disturbances including grounding faults, and a threshold is set to prevent protection mis-operation due to data loss at sampling points. Based on this, consecutive cycles of steady-state zero-sequence voltage are selected, and the Tanimoto coefficient is utilized to calculate the waveform self-similarity of the zero-sequence voltage, further distinguishing between permanent grounding faults and transient disturbances. Finally, a simulation model of high impedance grounding faults in a typical small resistance grounding system is constructed by Matlab/Simulink, and various fault conditions and transient disturbances are simulated. The simulation results indicate that under 20 dB Gaussian white noise interference, the method effectively detects permanent grounding faults and intermittent arc grounding faults, is not affected by fault location or phase angle, and the limit of resistance to transient faults can be increased to 7 kΩ. Additionally, the line selection device is promptly locked during transient disturbances such as out-of-phase three-phase switching, demonstrating strong anti-interference capabilities. The entire detection process requires only the bus zero-sequence voltage, without the need for additional monitoring equipment, making it easy to implement and cost-effective.