Low Voltage Cable Reflectometer Built in Test Module

Time domain reflectometry (TDR) has been a trusted way to find faults in long cable runs through high voltage systems for years. However, short cables and low voltage systems both pose challenges for TDR. Frequency Domain Reflectometry (FDR), which measures the phase difference of the incident and reflected waves, should be able to provide an increase in detection resolution while maintaining low voltage levels within the system. Assuming cables are less than half a wavelength long with respect to the sensing frequency, phase shifts either above or below 180° will yield information as to whether a cable fault is a short or open and, based on the cable velocity, yield the distance at which the fault occurs.