Cable 
diagnostic test methods, systems and apparatus are disclosed that utilize “
standing wave” principles to facilitate identification and location of insulation defect(s) along a 
power cable. The methods / systems measure dissipation factors and 
dielectric constants associated with the 
power cable insulation and the impedance of the 
power cable conductor at any number of points or sections along the 
axial length of the cable. In an exemplary embodiment, the disclosed method involves (i) connecting an alternating 
voltage source to a cable at a “sending end” thereof; (ii) applying a 
voltage to the cable at a first frequency to set up a traveling wave along the cable that is reflected at the “receiving end” thereof; (iii) permitting a 
standing wave pattern to be established along the cable by the traveling wave and the reflection thereof; (iv) measuring the total complex 
power loss (Sin) at the sending end of the cable; (v) calculating the 
standing wave voltage at any point / section of the cable based on the load impedance (ZL) connected at the receiving end of the cable, and the 
characteristic impedance (ZO) of the cable, or the measured / calculated cable parameters for the first frequency of the 
voltage source, (vi) repeating the foregoing steps while one of: (1) varying at least one of: the load impedance (ZL) connected at the receiving end of the cable, the first frequency of the 
voltage source; the 
output impedance of the 
voltage source, a combination of the load impedance (ZL), the 
output impedance of the voltage source and the first frequency of the voltage source, and combinations thereof; (2) interchanging sending and receiving cable ends; and (3) a combination thereof, and (vii) determining a 
dissipation factor (tan δ) and a 
dielectric constant (∈′), for the insulation, and an impedance, for the conductor at predetermined points / sections along the axis of the cable.