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Location of
Electrical Leak

Electrical Fault
Location with
9V Battery

Analog Centering
Technique

Derivation of
Fault Detection
Formula

Attachment 1

Manual Menu

Location of Electrical Leak

Brief Summary:

This section of the Technical Manual describes procedures commonly used for locating electrical faults or leaks in EM cables.

Introduction:

There are a number of techniques, which can be used to locate a short or leak in an EN cable. Depending upon the test equipment available and options available to remedy the problem, the individual who is performing the task can decide which technique would best suite their needs.

Discussion:

The following technique can be used on either single or multi-conductor EM cables to locate and eliminate electrical leakage from an electrical conductor to armor.

To find the exact location of the electrical leakage is a two-step process. First the location of the problem is located approximately using a battery and a digital voltmeter. If the goal of fault location is only to remove the fault, then the cable may be spooled to the approximate location, the line cut, and step one repeated to eliminate the fault. If the fault itself must be examined, then a second step is necessary. In this second step, the cable is spooled to the approximate fault location as determined in step one. Then a centering voltmeter and a battery are used to find the exact location of the electrical leakage.

The following technique can be used to locate the electrical leakage point to within a +100 ft. or closer depending onhow accurately the length of the line is known. The equipment needed is a digital voltmeter - preferable at least 4 digits accuracy and a battery. The length of the line L must be known.

Connect the positive terminal of the battery to one end of the conductor, which has electrical leakage to armor. Connect the negative terminal of the battery to the other end of the conductor, which has leakage to armor. Measure the voltage from the positive terminal of the battery to the negative terminal of the battery with the cable connected - call this voltage "V3." Measure the voltage from the positive terminal of the battery to the armor call this voltage "V1", See Figure 1 for details.                  

The distance "F" from the end of file cable connected to the positive of the battery to the point of electrical leakage is

F = (L X V₁) / V₃

A digital voltmeter is needed for this type test because the input impedance of this type of voltmeter is on the order of 10 Meg ohm. If an electrical leakage is causing problems, it usually has a lower resistance than 10 Meg ohm.

In some situations it is only necessary to remove the electrical leak. If this is the case, the line can be cut at the location determined by the above technique. Each of the two sections of the line can be tested to see which one still has electrical leakage problems. The line can be tested again once again using the above technique to locate the leakage. The point of leakage will be very near to the end of the section having the leakage. Short sections can be removed from that section until the point of leakage is removed.

If, on the other hand, it is desired to find and investigate the exact point of electrical leakage the following procedure can be followed. Once the leakage has been located approximately using the above method, it can be located exactly using the following technique. In this step, it will be necessary to have spooling equipment so that the cable can be spooled from one reel to another to find the exact location of the electrical leakage. The electrical equipment needed is a car battery or a battery charger and a center reading voltmeter - i.e. a voltmeter that can read both positive and negative voltages. An analog meter with a center needle is most often used but a digital voltmeter can also be used.

After using the approximate leakage location method described above, spool the line from one reel to the other to the computed approximate location of the electrical leakage. See Figure 2 for details.

Connect the positive terminal of the D.C. source (either the battery or battery charger) to the armor of the cable on one reel. Connect the negative terminal of the D.C. source to the armor of the cable on the other reel. Connect one lead of the voltmeter to one end of the conductor, which has electrical leakage to the armor. Slide the other lead of the voltmeter along the armor. Slide the second voltmeter lead along the armor until the polarity of the voltage changes. Continue to slide the second voltmeter lead along the armor until the spot is found where there is zero voltage across the voltmeter-This is the location of the electrical fault.

An alternative method for locating a conductor lead to armor is described in Figure 3. The derivation for this procedure can be found in Figure 4. The advantage of this procedure is that it does not require a power supply.

In the event the short or teak is intermittent and not persistent enough to obtain the desired results using the above mention techniques it may be necessary to "bum-in" the short with the use of a HiPOT device, an example of which can be found in Attachment 1.

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