TEC-X35 Tips & Frequently Asked Questions

There are certain situations in which the X35 is ineffective. Most all of these situations are due to bonding issues. Having a good understanding of how the Test Set current flows, as well as the returning ground current, will maximize the effectiveness of the X35.

Frequently Asked Questions:

Questions and Answers:

Q. Can the X35 be used over snow covered streets and flooded manholes?

A. Yes.  The X35 is not affected by snow covered roads or water in manholes and vaults.  However, it may be more difficult to know when you are directly over the feeder if manholes are covered with snow.  For best performance, take multiple readings moving side-to-side to make sure you are centered over the feeder.

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Q. Will the X35 detect Test Set signals on "Unjacketed" and "Jacketed" Concentric Neutral Cable?

A. Yes and No. Direct buried "Unjacketed" Concentric Neutral cable, in which the neutral is in constant contact with the earth, has demonstrated excellent results. With Jacketed Concentric Neutral cable, the faults that occur are generally faults between the conductor and the Neutral of the cable. Since, Jacketed Concentric Neutral cable generally has infrequent bonding or grounding of the neutral to earth ground, all of the Test Set pulse energy will return on the "Neutral" of the cable rather than disperse partially into the earth. This equal and opposite energy on the feeder cable neutral and primary conductor, cancels the generation of the magnetic field which is detected by the X35. In most of these situations, the X35 may have difficulty isolating the fault to a specific location on the feeder.

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Q. Do buried metal plates in the road influence X35 Readings?

A. When massive metal plates are buried under the road, the magnetic field may distort making readings difficult to detect. In these situations, moving past the plate should restore the detection of the Test Set signal.

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Q. Do feeders coupled with water pipes and other large metal ground returns affect the X35 performance?

A. There are situations where the effectiveness of the X35 is significantly reduced due to the feeder cable being coupled or strapped with other highly conductive material such as large water pipes. In situations where feeder cables are submersed in water and highly conductive ground current carrying material is adjacent to the feeder, the behavior of the magnetic field could appear similar to Concentric Neutral cable. All the returning ground current could return on the adjacent conductive material reducing the generation of the magnetic field. In these situations, try placing the X35 on the ground. This will increase the sensitivity of the meter by approximately a factor of 4, increasing its detection capability.

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Q. Does the X35 work on bridges?

A. If an underground feeder goes overhead and spans from one land to another next (e.g. across a bridge), the X35 will most likely be ineffective on the bridge due to the lack of grounding.

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Q. Why do I sometimes get positive readings in many directions when near the fault?

A. The X35 detects a magnetic field generated by the current in a cable. When the fault breaks down, the current from the Test Set becomes present on the sheath of the cable. The sheath current will then travel to the nearest earth ground or grounds, as well as travel back on the sheath of the cable. This dispersion generally happens only in the vicinity of a fault. Since the X35 cannot distinguish between copper and sheath current, positive readings can occur on more than one section of feeder cable due to the various flowing currents (see figure below). When this happens, it is generally a strong indication that the fault is close. As shown in the figure, the strongest reading (when close to the fault) may be a leg to a nearby transformer if it contains a bond with the least resistance to ground. For this reason, the X35 can not pin-point to an exact location when earth grounding is infrequent or a connection is poorly made.

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Q. Why doesn’t the display seem to move?

A. This can be due to either the HOLD button being pressed, or that the display is zoomed "out" too far such that the Test Set pulses are too small to display. Try either pressing the HOLD button or zooming in to a much smaller scale.

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Q. Why are the Test Set pulses displayed at a faster rate than the Test Set outputs?

A. The X35 is either in "TEST" mode, or you are standing near a large noise source. If the X35 is not in TEST mode, try moving at least 30 feet away from your current location.

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Q. Why does the message "TOO HIGH" being displayed?

A. This message indicates that the Gain selected is set "Too High". Simply lower the Gain until the message no longer displays. Note that when changing the Gain, make sure you wait at least 10 seconds for a Thumper pulse to occur. Most of the time, the "Too High" message only will appear when the magnetic field is generated from the Thump, or in high noise environments.

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Q. Why doesn’t the X35 power up?

A. This can be caused by either discharged or defective batteries, or batteries that are installed improperly. Make sure the batteries are installed properly and with the correct polarity, and the battery contacts are clean. If the contacts are clean, batteries are fresh and installed properly, the unit may be defective. Try a different set of fresh batteries and if the meter still does not operate, contact TEC for service.

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Q. Which way do I go at a "Tee"?

A. At a Tee or Branch, where one feeder splits into two, the reading on the outbound "faulted" leg is normally largest. Also, for Thumper or Hipot Test Set signals, the readings on the outbound "unfaulted" leg will often be negative, in contrast to the positive reading on the outbound "faulted" leg. If the readings at the Tee are confusing, take similar readings past the next manhole of each leg after the Tee. Taking measurements too close to the actual Tee can sometimes be confusing due to the splitting and orthogonal magnetic fields. If the situation is still unclear when measurements are made past the next manholes, a traditional measurement should be made at the Tee.

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Q. How are measurements made on a basket type feeder?

A. If the feeder is connected in a basket configuration (i.e. two parallel cables connected together at both ends), the X35 should only be used if the cable runs are sufficiently separated. If both cables use common manholes, distortions in the magnetic field may occur preventing accurate readings from being obtained. In this situation, measurements using traditional equipment should be made.

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Q. Why do the Thumper pulses go both positive and negative on the display

A. There are some cases where Thumper pulses are displayed both positive and negative. This can be due to a number of reasons, such as; 1) the Gain is set incorrectly, 2) there is a large reflection on the cable, 3) you are too close to the Test Set source, 4) a powerful test set is used and the cable depth is shallow, or 5) you may be standing close to a "Tee" where multiple magnetic fields may be present. Try increasing the Gain until the "Too High" light illuminates (and then back off one), or try taking another measurement further down the feeder away from any "Tee’s". This could also be caused by a distortion of the magnetic field due to either a change in feeder depth at your location or standing on top of a grate or manhole cover.  If the positive and negative pulses remain, you can still find the fault by always following the path with the largest signal level (even if its positive and negative).  

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Q. Why do I sometimes get a negative signal amplitude instead of positive when not directly over the feeder?

A. This situation can occur when the measurement is being made too close to the fault. The signal displayed is not the Test Set current on the main conductors, but rather the returning sheath or earth current that is returning from the fault breakdown along neighboring grounds, cables, or pipes.

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Q. Why do I see other pulses on the display that are not the Thumper?

A. Since the X35 detects magnetic fields, other equipment in the vicinity may cause interference with the X35. For example, the "caution flashers" of a utility truck that you may be standing next to, may create a pulsing field strong enough for the sensitive X35 to detect. The X35 has extremely high sensitivity to detect Thumper pulses in deeply buried cable, therefore a nearby current source above ground may be picked up and displayed. If this situation occurs, simply move away from the offending source.

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Q. The X35 is "on", but I can’t see any pulses on the display.

A. Things to check:

Q. The X35 seems to operate fine, but the TEST function does not seem to work.

A. The X35 contains an actual low voltage "Thumper" generator circuit to generate pulses that will be picked up by the X35 and displayed. If the X35 operates fine with actual Test Set signals but does not operate when the TEST button is pressed, the internal Thumper generator may have failed. This will not prevent the X35 from operating as intended, however, the TEST function is defective. The meter should be returned for service when convenient.

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Q. There is an excessive amount of noise on the display.

A. Excessive noise on a display is typically due to a nearby current source. For example, the sparking of a nearby motor, certain engine ignitions, arc welding, passing subways, etc., can cause interference to the X35. In these situations, simply move away from the noise source.

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Q. The signal level displayed is extremely small and difficult to read.

A. If you are working on a deeply buried feeder or a low output Thumper, the signal level may be small and difficult to see. Generally, a Thumper with at least a 12 microfarad capacitor is recommended for fault locating with the X35. If the level is difficult to read, try placing the X35 on the ground as compared with waist high. In most cases, you can get a 4 to 1 increase in signal level readings when the X35 is placed on the ground.

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Q. Why does the X35 operate but the backlight is disabled when the batteries fall to 30% of their capacity?

A. The X35 is designed to get the most operational time from your batteries. Therefore, the X35 will operate even when the battery voltage drops to very low levels. However, when the batteries are at this low level, they are not capable of providing the current required to operate the X35 AND the backlight. Since the X35 is typically operated during the day, an extra 2-3 hours of operation is achievable if no backlight is used. If you always want the backlight available, change the batteries when the X35 battery meter displays that the batteries are at 40% of their capacity (4 filled squares).

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Q. Why shouldn’t measurements be made where a feeder changes direction, Tee’s, or changes depth?

A. When a feeder changes direction, Tee’s, or significantly changes depth, magnetic fields are generated in multiple directions which could create false readings from the X35. Perform another measurement at least 20 feet from where the feeder changes direction or a significant change in depth occurs.

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