This paper proposes and analyzes the breakpoint detection method for a long 22.9 kV submarine power cable based on a time domain reflectometer (TDR) depending on the various fault situations. Appropriate conditions are required in the fault situations to apply the detection method based on TDR impedance. The detection method requires that the rising time of the input source should be short enough to detect the length of the breakpoint. The shorter the rising time is, the more advantageous it is to detect the breakpoint, but a long power cable can significantly attenuate the high-frequency signal. Therefore, it is derived through analysis that the performance of the breakpoint can be determined depending on the input source and rising time.