Toward error-free cable installations

Tests carried out in commissioning of underground cables have shown that as many as 50% of all faults discovered were due to errors in the installation of joints and terminations. Supplies and technologies have evolved, but training in their correct installation must not be ignored.

Medium voltage underground cable networks are being built in great length in Finland, so that the stricter demands for trouble-free distribution of electricity can be realized in given schedules. Elsewhere in the world, underground construction is escalating in response to urbanization and a growing need for electricity.

As the volume of underground cabling increases, concerns over the frequent installation faults revealed during commissioning testing have emerged. A snapshot of the current situation is provided by an example, reported by the network company Stromnetz Berlin, of a commissioning inspection for a new 10 kV customer network using 150 km of single-conductor cable, 180 joints, and 72 terminations. In total, 26 serious faults caused by incorrect installation were observed, half of them in joints and the other half manifested as cable damage.

Network companies have become more active in Finland

At the moment, network companies are looking for detailed information about the prevalence of installation-based defects. At the same time, Europacable ACC, a cooperative organization of cable manufacturers, is preparing training concept at the European level to improve the situation. Petri Hyvönenhead of a research group on high-voltage engineering at Aalto University, is familiar with the problem because installation errors are being discussed in the industry in Finland too.

“Network companies are ever more interested in the management and condition of their assets. Some of them have a clear desire to perform commissioning tests during the construction of new cable connections. Likewise, failure rates are monitored more closely than before, and companies strive to identify the underlying causes of cable defects more precisely,” Hyvönen says.

No research-based material is publicly available, but some electric utilities in Finland have conducted their own studies, examining items that are in use now or that were disassembled during renovation projects. Some disassembled items have been opened up, and their installation has been compared with the relevant instructions. Hyvönen says that, in the worst cases, as many as 50% of all items showed deviations from the installation instructions.

Plans are in progress for European accreditation

Europacable ACC is in the process of drafting content for electricians’ training and accreditation in work with medium voltage cable joints. The construction of networks usually involves working on cables with plastic insulation, but many electricians also install cable joints with oil-paper insulation. Therefore, the draft covers two accreditation categories, with one of them requiring competence in jointing a cable with oil-paper insulation to a plastic-insulation cable.

With these specifications, Europacable ACC strives to create a foundation for training provided by manufacturers, educational institutions, and various other organizations that is based on best practices in the sector. At the same time, it wishes to provide a clear way of indicating the status of a qualified electrician who has been trained in error-free installation of cable supplies. This should enable network companies to ensure that all installation is performed by qualified professionals and that the end result is free of errors. The work has only just begun, but the industry deems it very important to move the process along quickly, all the way to training events in line with regionally specified quality criteria.

Training beats repairing

Hyvönen sees no obstacles to the implementation of training and certification requirements in Finland. Mutual collaboration to promote them would benefit everyone from network owners and contractors to suppliers and manufacturers.

He explains, “Training and certification should be seen as an element that is of use to all parties, not merely as cost items. After all, any problems with installation quality are not due to only one party; there may be many causes for errors.”

“Improving the quality of installation work would increase the reliability of the electrical network, thereby reducing costs in the long term. If these training requirements are not put in place, financial pressure may bring operators with insufficient professional skills into the field. That would lead to more installation errors down the line. This scenario would be much more expensive for network companies than installation done by a trained and accredited professional,” Hyvönen says.

Ensto Pro blends theory and installation exercises

The Ensto Pro product training, customized for those constructing networks, covers subjects from underground networks to network automation and charging of electric vehicles. Participants can select the desired modules, which can be tailored to the needs of those taking part.

When it comes to training events, excellent planning and high quality are of paramount importance to Ensto. Every training event includes both theory-based lessons and practical installation exercises carried out in collaboration with Ensto employees. The main goal is for the products to be installed correctly. This will ensure a long service life and reliable operation.

Contact for further information: Kaisa Kaikkonen, Marketing Communications Manager, Ensto Finland Oy,