Cable Fault Location . . . Not for the Faint of Heart (Part I)

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The mere mention of cable fault location sends shivers down many a spine. Don’t lose heart, all is not lost.  Remember, cable fault location, like any other trade, simply requires some basic skills, proper tools and a sound procedure. Don’t be fooled into over simplifying the problem or solely relying on a single technique or instrument for every situation. Although many faults exhibit similar properties, all faults are unique and therefore different. A fault locating technique or instrument that works well in one situation may be completely useless in another.

A skilled golfer must be able to analyze a situation before reaching into his or her bag and selecting a club. A variety of clubs and knowledge of their performance allows the golfer to select the most efficient tool for the job. The same is true for a skilled cable fault locator. As in diagnosing any complex problem, following a step-by-step procedure will help in arriving at the solution or, in this case locating the fault efficiently. 

Gather as much information as possible about the cable you are about to test. Understand the test and measurement equipment available to you and the application it was designed for. Know how to properly operate the equipment and know its performance capabilities and limitations.  The first step in a healthy procedure is to conduct basic performance tests to determine the nature of the problem. Tests and equipment available for this step include (but are not limited to):

Cable Type

Tests Performed

Test Equipment

Telecommunication (Copper)

Hazardous AC and DC voltage on cable pairs.


Voltmeter (including multifunctional meters).


Voltmeter (including multifunctional meters).


Loop resistance

Ohmmeter (including multifunctional meters).


Insulation/Isolation or Stress Resistance

Insulation tester / Megohmmeter / Resistive Fault Locator



Open meter / capacitance meter


Metallic Noise / Power Longitudinal balance


Noise influence & balance meter

Low Voltage Signal & Control


Ohmmeter / Time Domain Reflectometer (TDR)


Insulation Integrity

Insulation tester / Megohmmeter / Resistive Fault Locator


Electric Power (Medium and High Voltage)


Ohmmeter / Time Domain Reflectometer (TDR)


Insulation integrity

Megohmmeter / DC Hipot / VLF Hipot / Tan Delta Bridge / PD Detector

ven with the proper equipment and experience, cable fault locating can present challenges. These challenges are minimized significantly by understanding the equipment and techniques available and perhaps most important; develop and adhere to a sound procedure.  Combining our vast inventory of cable test and fault locating equipment from premier vendors such as HV Diagnostics, High Voltage Incorporated, and Megger along with our years of industry experience, Protec Equipment Resources can guide you through each step of the way.  Give us a call.

In Part II of this blog series we will look at cable fault pre-locating techniques and equipment and finally in Part III we will address cable fault tracking and pinpointing techniques and equipment.