Using The TEC-X35
The X35 is a hand-held meter for pre-locating electrical faults in underground feeders from above ground. It is used in conjunction with either a Thumper (Capacitive Discharge) or Thyratron configured DC high voltage test set (Test Set) or just the Test Set (Hipot) itself. Because the X35 cannot distinguish the difference between copper current and shield current, the meter is used to "pre-locate", not "pinpoint" feeder faults in network type systems. However, users with direct buried concentric neutral cable in which the shield is in constant contact with the earth have reported the ability to pinpoint. Pre-locating is defined as directing field operators to the general area of the fault, minimizing manhole opening. Meter accuracy is generally related to the quality of feeder bonds. With proper bonding, the X35 should identify the fault location to the sections of feeder that are between the fault and the nearest feeder bonds without opening manholes. The X35 is also unaffected by adverse environmental conditions, such as snow covered or flooded manholes, thereby permitting faster localization of a fault. In fact, the X35 was successfully used where other instruments failed, to pinpoint a submarine cable feeder fault 12 feet underwater in the middle of a three mile bay while on a boat.
The X35 is a complete self-contained unit. The unit contains a tuned magnetic pickup sensor, graphical display, and state-of-the-art signal processing electronics. The pickup sensor inside the X35 senses and measures the magnetic field that the Test Set current creates around the faulted feeder. Other nearby feeders create interfering background magnetic fields which typically dominate the Test Set created field. The X35 is designed to nearly eliminate the strong interference and amplify the unique "fingerprint" of the Test Set signal. The graphical display paints a picture of the Test Set pulse to trace to the fault location.
When the X35 is positioned above the faulted feeder, the X35 displays a visual representation of the test signal generated by the breakdown of the fault. The X35 displays a polarized signal (showing amplitude of the signal and direction the signal emanates from) for the Thumper and Hipot signal. The X35 displays the Thyratron signal as a unidirectional signal (i.e., amplitude only, not direction). It should be noted this document describes fault pre-localizing using only the Thumper and Thyratron signals. The Hipot, which is simply a variable DC high voltage power supply (sometimes called "proof testing"), is generally used only to condition the fault. Occasionally, the fault cannot be conditioned properly to use the Thumper or Thyratron. When this occurs, the fault can still be localized with just the DC high voltage test set (Hipot) and the X35. The instructions for "Fault Locating with a Thumper" should be followed when the fault is being localized while using just the Hipot. The only difference between the Thumper and Hipot is that the Thumper pulse is periodic (typically 6-7 seconds per thump), whereas the Hipot pulse is generated only when the operator increases the high voltage high enough to break down the fault. Some Test Sets in "proof" mode will automatically generate a repetitive breakdown pulse. The DC high voltage test set will charge up the feeder to a point (less than the maximum level recommended on your particular cable) where the fault will break down and then repeat. This operation, on either a conditioned or unconditioned feeder, is supported by the X35 and will provide the operator with signal level and directional information when searching for the fault.