How covered conductors save both lives and money
The bare lines of the medium voltage electricity network are open to accidental touching and wildlife, which often causes delivery failures. Choosing a covered conductor (CC) system with Ensto accessories is guaranteed to pay for itself in the form of fewer faults, lower maintenance costs, and higher-quality electricity.
Someone always has to pay for the consequences of delivery failures and problems with electricity quality. For utilities a failure means immediately searching for the fault location, many times in bad weather, difficult terrain, and the dark of night. That requires well-trained professionals using off-road vehicles or, in the case of a blackout, even helicopters, which makes the operation very costly.
Even so, it isn’t optional, because a lengthy interruption in delivery can even put human lives in danger. The damage at least creates vast expenses, not only for utilities but also to their customers, such as grocery stores, warehouses, production sites, and hospitals. In many countries, utilities are responsible for paying compensation to their customers, sharing that cost.
Is this the only way to operate? How can the cost of delivery failures be minimized? Easily: by reducing the number and duration of failures. That can be achieved by choosing covered conductors with appropriate Ensto accessories instead of bare lines. The CC line construction costs are moderate in view of the advantages offered over traditional bare-line structures. In construction of parallel lines, the costs of bare and CC lines are the same. So don’t let faults take your money.
Fewer faults and more time for repairs
Covered conductors are plastic-covered overhead conductors without metal sheaths, which prevent interruptions due to collisions or momentary contact with a foreign object. According to Petteri Pulkkinen, a product manager with Ensto Utility Networks, these were developed to improve the reliability of distribution and transfer of electricity. “They typically decrease the failure rate significantly, from 4.5 faults / 100 km per year with bare conductors to only 0.9 faults / 100 km,” he says.
With covered conductors, contact with a crane boom, for example, is not always fatal. Most accidents that would cause damage, injury, or death in the case of bare lines can be avoided by means of covered conductors. They can sustain even a bending tree without delivery failure, which gives more time to fix the problem. This can be done in normal daytime work without emergency mode or the added labor costs of nighttime or weekend operations.
“Also, using the CC system offers considerable space savings: the space required is about 40% less than that for a standard bare line. This means, for instance, narrow line corridors and space savings with substations. The parallel line structure enables even more space savings,” Pulkkinen says.
He continues, “That assists in establishing long network lines in forests and opens more opportu¬nities to build lines along roadsides or upgrade existing bare lines to double circuits. Also, lines in urban environments benefit when conductors can be installed closer to buildings and other structures.”
Greater safety for birds and people
Overhead lines are open to birds for a rest or even nesting. The largest species are in danger of touching another wire when spreading their wings. This can be fatal. Regrettably, in some areas it is quite common to find evidence of this. With CC lines, birds and other animals are effectively prevented from being injured if accidentally touching the wires.
In nature, harsh winds and accumulating ice can cause phase-to-phase touching. Heavy snow may bend trees over the lines, and furious storms can fell trees. These usually affect wide areas at once, many times in remote areas where lines are long and fault locations difficult to locate. In the tropics, everything grows rapidly and a line corridor can become covered by tall bamboo rising to reach the wires. In these cases too, CC systems prevent failures and give plenty of time to maintain corridors.
When medium voltage lines enter urban areas, the risk of accidental touching or vandalism increases. Normally that means serious danger, and loss of life is likely. Covered conductors provide protection, preventing or reducing the damage in these cases also.
Proven accessories and solid training
Ensto’s accessories to CC lines are electrically and mechanically designed for the best performance and safety. Accessories for medium voltage CC lines include insulators, tension and suspension clamps, arc protection devices, current limiters, connectors, bird protectors, crossarms, and tools.
All Ensto accessories are tested for compliance with the EN 50397-2 standard at fully equipped and calibrated in-house testing labs. Testing ensures that the products meet the strictest national and international standards – in fact, the testing goes beyond standards’ requirements. Ensto works with many international test laboratories and uses well-known external labs for certification testing.
“For customers, the Ensto Pro training program provides on-site support in the form of installation courses, advice in network design, and consulting. Covered conductor wires are not to be installed directly to replace bare wires. That is why we speak instead of CC systems,” Pulkkinen says.
“The accessories and also training are specially designed and tested to fulfil the requirements and to gain all the benefits of CC lines. That does not mean increased overall cost. Instead, the added investment is marginal in comparison to the advantages gained and the rapid return. I can say this because our customers around the world have been telling it to us since the 1990s,” he concludes.
For further information, please contact:
Petteri Pulkkinen, Manager, Overhead line solutions, Ensto Utility Networks, petteri.pulkkinen@ensto.com
Ensto has 45 years of experience in working with medium voltage CC systems. Over the years, we have delivered approx. 3 million MV CC tension sets, 6 million suspension sets, 3 million arc protection devices, 4 million insulation piercing connectors for MV CC, 5 million end caps, and 2 million mid-span joints.