Megger delivers fast, effective fault location for LV cables

Designed specifically for use on underground LV cable networks, Megger’s new EZ-THUMP™ 3 cable fault location system makes it possible for even inexperienced users to accurately locate faults quickly and easily, thereby reducing the duration of power outages and the risk of costly penalties.

Many low-voltage cable faults can be found using a time domain reflectometer (TDR) such as the Megger TDR2050. The TDR acts like a cable radar, sending a pulse through the cable, then recording and timing the reflections from an impedance change such as an open or short circuit, and calculating the distance to the fault.

Unfortunately, a TDR will not see high-resistance faults which are very common in underground cable networks, so there is a need for a complimentary, combined approach. The EZ-THUMP 3 provides this, and finds cable faults by combining the TDR measurement with a surge generator to find high-resistance faults. It works by generating a low-impedance spark at the fault location, which can be seen with the TDR.

Unlike test sets designed primarily for use on MV cables, the Megger EZ-THUMP 3 can deliver its full 500 J surge discharge at lower voltages, allowing it to locate difficult faults effectively with minimal risk of further damaging the cable.

In addition to its dual-stage capacitor surge generator, the EZ-THUMP 3 incorporates a time domain reflectometer (TDR) that displays results on a high-brightness colour display that can be read easily even in direct sunlight. The TDR can be used on its own for pre-locating low-impedance faults, and also with the surge generator for pre-locating high-impedance faults using the arc reflection method (ARM).

For accurate pinpoint fault location, the EZ-THUMP 3 is used in conjunction with an acoustic/electromagnetic receiver or a voltage gradient detector. The instrument also supports cable sheath testing and sheath fault location using the step voltage method.

Designed from the outset to be easy to use, the EZ-THUMP 3 is controlled from a single rotary knob and, for normal operation, it requires no setting up. Users simply make the test connections to the cable and switch the instrument on. After it has verified that the earthing arrangements are correct, using Megger’s renowned F-OHM safety method, the EZ-THUMP 3 automatically pre-locates the fault and displays the results both graphically and numerically.

An expert operating mode is also available, which allows experienced users to fine tune the operation of the instrument to optimise performance as an aid to locating especially challenging faults.

The internal rechargeable battery used in the EZ-THUMP 3 has been designed to offer a long service life but, when replacement eventually becomes necessary, this can be carried out in the field by the user with no need to return the instrument to the manufacturer for servicing.

The EZ-THUMP 3 is ideal for use on street lighting, distribution and campus networks, and is small enough to transport in an ordinary car. It can be powered from either a normal AC mains supply or from its own internal rechargeable battery, making it ideal for use in almost any location, even where access is restricted.

Author: Cable Technology News Team

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