Electrical Tester Contractor edition
August 2016
Made to measure - time domain reflectometers

Made to measure - time domain reflectometers

20 August 2016

TDR2000/3 time domain reflectometer

You ask: I’ve got a shot at a rather attractive street lighting contract. Most of the work is straightforward, but I’ll need to be able to locate faults on the underground cables that supply the lights. Do you have any suggestions about how to do this?

We say: Fault location on buried power cables can be tricky but, with street lighting, a good time domain reflectometer (TDR) will almost always give you the results you need. The TDR works by firing a pulse into the faulty cable. Some of the energy from this pulse is reflected back to the TDR by the fault and, by measuring how long this reflected energy takes to return, the instrument can calculate how far away the fault is. TDRs come with many different options, but for street lighting you need an instrument like the Megger TDR2050. This has a built-in power blocking filter and can locate faults at distances of less than a metre from the point of connection up to around 20 km. It also has an Xpert key that’s very useful if you’re new to TDRs as it automatically adjusts the range and gain of the instrument, and positions the cursor over the first major event on the cable.

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Tags: TDR, TDR2000/3, time domain reflectometer