Testers aid cable qualification

Verizon Communications is using test equipment from Megger to prequalify existing analogue outside plant cable installations prior to converting them for use with digital services.

Verizon Communications, one of the world's leading providers of high-growth communication services, is using test equipment from Megger to prequalify existing analogue OSP (outside plant) cable installations prior to converting them for use with digital services.

Modern digital subscriber systems continually subject cables to high voltages which, if there are weaknesses in the insulation, quickly lead to breakdowns.

To avoid this problem, Verizon's transmission and protection specialists searched the market for test equipment which would enable the insulation quality of all OSP lines scheduled for digital use to be checked quickly, easily and accurately.

After evaluating a wide range of products, the specialists decided that the BM81/2 insulation tester, and the DET62D three-terminal digital earth tester - both from Megger - best suited their requirements in terms of performance and value for money.

During testing, Verizon's field technicians use the instruments to measure tip-to-ring, tip-to-ground and ring-to-ground insulation resistance on the copper cable pair for each span (telephone office to repeater, repeater to repeater, repeater to remote terminal etc) of the carrier system.

The results of these tests enable the technicians to identify problems in the cable installation, which could lead to service disruptions with the new digital systems.

In addition to identifying potential insulation problems, Verizon's technicians have also found the instruments to be invaluable in revealing the presence of resistive and capacitive faults which might be detrimental to the service quality of a digital pair gain carrier.

The rapid identification of faulty cable pairs allows the technicians to take appropriate remedial action.

If vacant cable pairs are available, these may used as substitutes for the faulty pairs, or bad sections in the cables can be replaced.

In every case, the pre-qualification procedure using Megger instruments enables the installation to be brought up to the required standard before digital services are offered, ensuring a smooth, trouble-free changeover.

The compact handheld BM81/2 used by Verizon offers insulation measurement up to 200Gohm, and features a dual analogue and digital scale.

A live-circuit warning ensures safe operation, and the instrument also provides useful ancillary functions, including continuity testing and voltage measurement.

The DET62D digital earth tester is a readily portable instrument housed in a weatherproof IP54 case with integral carrying handle.

It offers accurate determination of earth resistance with automatically selected ranges of 0.1 to 199.9ohm and 0.001 to 1999kohm.

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