Fault sensing method, device and equipment for neutral ungrounded system, and medium

The embodiment of the invention discloses a fault sensing method, device, equipment and medium for an ungrounded neutral system, and the method comprises the steps: injecting a pilot frequency detection current, and determining a capacitance value converted to a PT secondary side from the ground distributed capacitance of a power distribution network and a ground distributed capacitance value of the power distribution network; the injected current signal with the reference frequency is used for respectively determining the impedance of the power distribution network when the power distribution network normally operates and when the system is in single-phase grounding; further determining the parallel impedance of the capacitance converted from the ground distributed capacitance of the power distribution network to the secondary side of the PT and the grounding transition resistor; determining a to-ground dielectric loss tangent value under the current signal injected with the reference frequency by combining