1. Low voltage pulse method: By inputting pulsed radio waves into the line, the waves are transmitted at a fixed speed V and reflected back to the input end when encountering a fault point. The fault distance can be calculated by measuring the round-trip time T. This method is suitable for low resistance grounding, short circuit, and disconnection faults. For high resistance faults, it is necessary to apply DC high voltage or impulse high voltage to discharge them, and use flashover arcs to generate reflected waves.

2. DC high-voltage flashover method: Gradually increase the DC voltage applied to the tested cable until a certain voltage value is reached, and the fault point is broken down to form a flashover. The flashover arc is used to generate short-circuit reflection, and the reflected wave is measured to determine the fault location.

3. Impulse high voltage flashover method: When the fault resistance decreases to form a stable channel and it is difficult to apply high DC voltage, impulse voltage testing is used. Charge the cable through the ball gap until it breaks down, and use the flashover arc to generate short-circuit reflection. Add a measuring inductance L at the input end to read the echo, and calculate the fault distance based on the interval between multiple reflected waves. The entire process presents a cosine curve that is close to attenuation, with fast pulse reflection waves superimposed on it.