Time Domain Reflectometry (TDR): Technology Review and Applications

Tom Sandri presents Time Domain Reflectometry (TDR): Technology Review and Applications. A time-domain reflectometer (TDR) is an electronic instrument used to determine the characteristics of electrical lines by observing reflected waveforms. It can be used to characterize and locate faults in metallic cables (for example, twisted pair wire, coaxial cable, or electric power). It can also be used to locate discontinuities in a connector, printed circuit board, or any other electrical path. This webinar will discuss the theory of operation of a TDR and explore its many applications.
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Protec is an administratively-approved course provider for the InterNational Electrical Testing Association (NETA).
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[@jluke6861]

Thank you for the Great Video.

[@ProtecEquipmentResources]

Thanks for watching!

[@protossid]

Thank you Sir, very informative video

[@ProtecEquipmentResources]

Glad it was helpful!

[@MarkSeager-dp2kg]

Can TDR be effective for underground non shielded power cables? For example, could a TDR measurement be performed on a PV source circuit, containing 2 500kcmil conductors run underground in conduit?

[@ProtecEquipmentResources]

Hi Mark, thanks for your question. From Bret Hammonds: The technology behind TDRs is ideally suited for two conductors separated by a homogeneous (equivalent) insulation such as what you would find in either a shielded cable or one with a concentric neutral. The case that you have presented is less than ideal for use of a TDR since it is only able to detect very significant changes in impedance such as an open circuit or a short circuit.
Having said that, it might be possible under some very unique circumstances for a TDR to be helpful in finding a fault in such a situation as what you have described. Those circumstances would include:
- Using either a grounded conductive conduit for your return or the two separate cables that are running through the conduit. In either case you would NOT have a homogeneous (equivalent) impedance throughout the distance of the cable run.
AND
- A significant fault that is either completely open circuited ( ~ ∞ ohms) or a very low impedance (for all practical purposes considered to be a short circuit between the conductors.)
If the fault is a high impedance fault, which is often the case, then the TDR will NOT be able to see the fault without being integrated into a more elaborately featured cable fault locating system.