More than two-thirds of interruptions in medium voltage cable lines are related to installation of accessories. The growing problem has activated many distribution network operators to undertake or request systematic installation training.
The construction of medium voltage cable networks is at a higher level than ever. There are several trends behind this, such as urbanization and the need to weatherproof existing fault-sensitive overhead lines.
Increasing number of installers are needed to do the job and utilities are typically outsourcing that work. Contractors usually provide a wide variety of services, and the professional background and experience of installers may differ. Traditional craftmanship of installing medium voltage cable accessories, built over the years, is in danger of disappearing in future.
Interruptions due to defects in joints and terminations are too frequent, which raises questions. How is that possible, even though the accessories are better than ever? Is it possible to improve the quality of installation to prevent interruptions and costs? Let’s ask Senior Vice President of R&D and Technology of Ensto, Markku Wederhorn.
“We have developed and produced medium voltage accessories for almost 20 years. Experience shows that over two-thirds of failures are caused by errors in installation. Accessories themselves are industrial products with thoroughly tested materials and construction. Also, they are produced under certified and audited quality system. A failure caused by accessory itself is very unlikely.”
"As a result of training and certification,
installation errors no longer occur"
One of the studies showed that all failures which could be analysed were somehow due to installation. Typically, there is not just one single reason, but several minor mistakes or inaccuracies during one installation. When those small things accumulate, interruption may occur in coming five or ten years.
Installation of a medium voltage joint, for example, has very high requirements what comes to purity and exact measures. In practise, work is often done in harsh environments with water, sand and wind. Many times, a complete tent would be needed for protection. Also, the measures for cutting and peeling are product-specific and should follow the installation instructions.
Even the small things are important and should be done properly even under pressure. Understanding of that is essential and requires installation training of that product.
“Quality of installation is a growing problem in Europe and concerns all manufacturers”, says Wederhorn, who is also a board member of Europacable Accessories Group. “The common interest for all is to raise attention to this trend and its solution: training and certification of installers.”
Ensto has been organized product training for years and has seen how utilities have started to request trained installers to build on their lines. For some it is even a regular routine every four or five years. According to Wederhorn, the next step of utilities is to demand contractors undergo product training or alternatively present a fresh certificate before starting the work.
Some customers of Ensto do that already. Network and accessories are designed to last forty or fifty years, but the responsibility of a contractor lasts normally just a few years. Those utilities know that training is one of the most effective ways to increase network reliability and reduce the total cost of ownership. Practice has shown that as a result of training and certification, installation errors no longer occur and, consequently, the resulting defects have completely disappeared.