Danger – high voltage

By Jonathan Vail 

It is sometimes said that doctors bury their failures, but for cable makers we like to bury our successes, either within the ground or within the building structure. Our products should only be seen during installation and sometimes this means that the end client does not recognize the importance of a quality product. For our industrial users such as the oil and gas industry the overall cost of cable is a relatively small percentage of the project cost, but the potential loses from cable failure during the operational life of the facility are high. That is why for these customers it is not only the most cost effective solution that is important; they must have a reliable solution.

Ducab’s mission is to provide our customers with “Total Quality Excellence of product and service”. This means more than just providing cables that fully meet the customer’s specification.

In the UAE we do not have national standards for cables so customers often rely on international specifications such as IEC, which set a base level of requirement but no more. IEC specifications are written and agreed by international panels and are therefore almost always less stringent than national specifications such as the British BS standards or the German VDE standards. At Ducab we would not be content to offer a cable that only met the IEC standards. We manufacture within a quality system that ensures that our products exceed the requirements of IEC to give our customers a product that will be fit for purpose and give the service life that should be expected from a top quality cable.

To understand why is this important, let’s look at two fundamental components of any cable, whether it be building wire, medium voltage or even high voltage.

Conductors
If a conductor does not use the right grade of material or is manufactured in a careless fashion the resistance will be too high. If the conductor design is such that it is inflexible then there is a danger of conductor damage during installations leading to high resistance. A high resistance leads to the cable operating at too high a temperature, which can in turn lead to cable failure. Losing power within a domestic situation is uncomfortable for everyone especially now our lives are so dependent of electrical power. In an business or industrial situation loss of power can lead to considerable commercial loss as well as potentially giving rise to a safety hazard. For cables that are not buried but are installed in buildings or in air the high temperature generated by a poor quality conductor gives a high risk of fire with potentially lethal outcome.

Insulation
If the cable insulation is manufactured too thin it can lead to cable failure and if too thick can lead to installation problems for our customers as well as being more expensive than necessary. Use of sub-standard materials or poor process control can also lead to porosity or mechanical damage to insulation. These in turn can significantly reduce the life span of a cable even though they may meet the routine test requirements defined in the IEC standard. The Ducab routine test facility has one of the most sensitive factory based partial discharge test areas in the World. The mechanical damage shown in the photograph of a medium voltage core is clearly not acceptable but will pass the test requirements of IEC standards. Such damage is easily detected and failed by the more sensitive Ducab routine test.

It is the responsibility of manufacturers to ensure that products not only meet the standards but also meet the customers’ needs. At Ducab we will continue to refuse to accept lower standards in raw materials, processing or testing that may compromise the quality of product to our customers. We will also campaign with local and regional authorities for tough standards and rigorous third party quality auditing of manufacturing facilities to ensure that cable products supplied by us and others provide excellence of service by operating safely, reliably and efficiently.

Jonathan Vail, General Manager Technical – joined Ducab in 2001.
Jon holds a degree in Electrical Engineering from Imperial College and a Master’s Degree in Business Administration from Brunel University. He is a Chartered Engineer and a Fellow of the Institution of Engineering Technology. He has over 25 years of experience in the cable industry, at all levels from low voltage to 500kV systems. He is active in CIGRE study committee B1 on cables and overhead lines and is also a Director on the Board of BASEC (The British Approval Services for Cables).