Line Impedance Resonance Analysis

A variable frequency signal generator injects a signal into the cable. The fault has a different characteristic impedance than the cable so some of the energy is reflected back to the source. Standing waves are set up in the section of cable between the source and the fault.

As the frequency is increased, the impedance as seen from the source cycles. It's a technique we used to call the peak and valley method. The frequency peaks (or frequency valleys) are measured, and knowing the propagation velocity in the cable, v, you can calculate the distance to the fault.

The difference between successive frequency peaks, f(n) and f(n+1), is the fundamental frequency f(1). The wavelength corresponding to the fundamental frequency is twice the distance to the fault.

df=f(n+1) - f(n)

D = v/(2 x df)

https://www.researchgate.net/publication/283300422_Advancements_in_Wire_Condition_Monitoring_Using_Line_Impedance_Resonance_Analysis_LIRA