Reflectometry on Asymmetric Transmission Line Systems

Time domain reflectometry is frequently used to localize faults in electrical systems. Most existing literature on reflectometry in transmission lines considers symmetric faults that are either shorts between the two conductors or open circuits where both conductors are disconnected at the same location. This paper investigates spread spectrum time domain reflectometry (SSTDR) applied to asymmetric twin-lead transmission lines in which either only one conductor is disconnected, or the reflectometry instrument itself is asymmetric. For asymmetric faults, we observe not only the expected dominant reflection corresponding to the location of the disconnection, but also an additional reflection from the end of the transmission line. In the second case, we leverage the asymmetric response of the SSTDR instrument to identify which of the two otherwise identical conductors has been disconnected.