Going Underground

Ensto is the main promoter of the mechanical cable laying method in Poland at the moment.

There are approximately 77,000 kilometers of medium voltage (MV) cable lines in Poland – this represents about 26 percent of MV lines. Building underground power lines instead of overhead lines has many advantages.

Autumn- and spring storms can of course bring down power lines, and the superior performance of underground lines is indisputable. "The need for gradual replacement of overhead power lines with cable lines results from the constant pressure of the regulatory authority to improve reliability indicators of the consumers' power supply,” says Grzegorz Widelski, Vice-director of Power Networks Property Management Department at Energa Operator.

Widelski says this applies in particular to the MV network, which holds the largest share in the SAIDI and SAIFI indicators. "All distribution system operators in Poland have taken steps towards changes in construction of cable MV networks,” he says. “In the draft of Polish Energy Policy by 2040, it’s been proposed to develop a national program for MV network cabling, and the details of the program will be known as soon as the government adopts the final version of the policy."

"The traditional cables and methods of laying the cables have resulted in a higher cost of construction compared to overhead lines,” says Widelski, "Therefore we’re looking for cost-effective methods to reduce the cost of underground cabling."

Ploughing: old tech reimagined

Throughout Poland, one is starting to see ploughs with the specific purpose of laying underground cables. The ploughs can be especially seen in rural areas, where they operate roadside under existing overhead lines.

Contractor Piotr Jaśkiewicz, of Global Jaśkiewicz i Pluta, says three-core cable laid with a vibration plough has many advantages: "It reduces employees and equipment required. The operator can load the cable drum and deliver it to the construction site himself reducing transport time. Three-core cable also lets us use a smaller plough. The plough replaces the ground as it ploughs, causing less interference with the forest cover and reduced environmental impact.”

Ploughing is four times faster than installing overhead lines. This makes ploughing attractive in a market, where projections estimate there’ll be two million fewer Poles during next ten years. Residents can also see benefits of ploughing as they face less machines on work site and project proceeds faster.

Ensto leads

"Our experience with three-core universal cable systems enabled us to develop a complete solution for ploughing AXAL-TT PRO. Thanks to our cooperation with partners in other markets like Sweden, Austria, and the Czech Republic, we were able to gain know-how and adapt the solution to the Polish market," explains Lesław Kwidziński, Sales Director of Ensto Utility Networks in Poland. 

Recently, in a pilot project, 1,800 meters of cable were ploughed in Barkoczyn in northern Poland (1,500 meters in forested areas). Cable ploughing speed in forested areas ranged from 150 to 200 meters per hour. The cable was tested, commissioned, and is currently being used to deliver electricity. There were no problems with the ploughing method.

“The AXAL-TT PRO three-core cable has proven its value in ploughing,” says Grzegorz Widelski. “The cost shows that this method deserves the interest of operators. We were also surprised by the speed of laying line."

The local utility in Barkoczyn has approved ploughing method, and it may now be used on a larger scale. The future of ploughing looks bright in Poland as other pilot projects have already been approved or ongoing.


Read more about underground cable networks