Overhead Line Fittings (UK) has used a Cropico microhmmeter for resistance measurement during an anti-corrosion product testing programme. The manufacturer works with the National grid, power distribution network operators and their contractors to provide bespoke insulators, fittings and conductor accessories used in the installation and maintenance of overhead power cables. As part of the services provided to customers, Overhead Line Fittings operates an in-house test facility at its headquarters in Atherstone, Warwickshire.It has been testing bi-metallic joints to assess how its oxide-inhibiting compound can reduce the rate of corrosion between electrical connections. This is a problem that costs utilities significant amounts of money in maintenance and repair costs and can cause delays to essential services such as railways when power distribution lines fail. Overhead Line Fittings's testing involved a heat cycle process that utilised a Cropico D05000 microhmmeter for the measurement of resistance levels. A current of 700A was passed through a bi-metallic joint in a cycle of one hour energised and 40 minutes de-energised.
Humidity levels averaged 60 per cent during the testing, which was conducted on both compound treated and non-treated joints continuously for 96 hours. Resistance readings were taken automatically at the rate of two per second, showing that levels rose as the galvanic corrosion started to attack the joint. The testing confirmed that an oxide-inhibiting compound can have a positive impact on the electrical performance of the type of bi-metallic joints used on transmission and distribution power liners. The Cropico D05000 microhmmeter enables accurate low-resistance measurement to be undertaken to ensure that products meet relevant technical performance standards and specifications.
Programmable current levels and the selection of different test speed settings give the D05000 tester the flexibility to accurately measure the resistance values of different cable products. These include single-end and plain soft wires through to bunched, stranded and large-diameter rope-type conductors. Accurate and reliable in-line cable resistance measurements taken in this way enable cable manufacturers to maintain optimum operating efficiencies in terms of copper raw material use.
