CASE STUDY: Russian Utility Invests in Cable Undergrounding

Sevkabel Group and DOW ENDURANCE Compounds joined forces to support Lenenergo.

By Robert Tarimo, Dow Electrical & Telecommunications

Lenenergo is one the largest electric power distribution and network companies in Russia. Its mission is to supply reliable, continuous, high-quality and clean electricity to consumers in Saint Petersburg and the Leningrad region. It also is tasked with meeting the growing demand for electric power and capacity. Lenenergo must meet these requirements without contaminating the city and the water of the Neva River which flows through St. Petersburg on its way to the Gulf of Finland.

Challenge

The utility did not invest adequately in the power grid from the late 1980s to the early 2000s and, therefore, found that within a few years it was operating with an outdated and inadequate infrastructure that was likely to lead to unreliable electricity supply.

Critical facilities, such as government agencies, military units, residential areas, and the major industrial enterprises spread across the territory, were at risk of intermittent electricity supply and increased outages. Lenenergo was spending more and more on ongoing repairs and grid updates just to maintain system reliability. Even with the extra investment, the quality of the overall network and the service to consumers was declining.

The utility needed to upgrade the system, but it was not going to be an easy or inexpensive task. The substructure of the St. Petersburg underground cable network posed a number of technical challenges. The depth of cable laid by horizontal directional drilling (HDD) varied from 2 meters to 15 meters and more below surface level. A large number of water hazards at a depth of around 10 meters also existed, making it difficult to envision a solution.

The depth of cable laid by horizontal directional drilling (HDD) can vary from 2 meters to 15 meters and more below surface level.

 

The 110 kV cable was encased in a concrete stall, helping to ensure that the cable is well protected from potential ground motion and mechanical damage.

Lenenergo conducted an in-depth study that led to the development of a three-year program (covering 2010 to 2014) to upgrade the existing 35-110 kV cable lines and reconstruct cable lines in St. Petersburg.

Sevkabel Group, one of the leading wire and cable producers in the Russian Federation, with support of Dow Electrical & Telecommunications, a business unit of The Dow Chemical Co., worked with Lenenergo to implement the program.

The DOW ENDURANCEà¢â€ž- family of semiconductive and insulation materials won the public tender to supply cables to this important and complex project.

Together, Lenenergo and Sevkabel agreed to lay a new 110 kV cable using HDD under the Neva River, at a depth of 23 meters.

Lenenergo and Sevkabel agreed that priority should be given to replacing the power grid equipment showing the greatest degree of wear. That meant the project started with laying a new 110 kV cable using HDD under the Neva River, at a depth of 23 meters. Lenenergo deployed for the first time DOW ENDURANCE crosslinked polyethylene compound (XLPE) in the place of the usual oil-filled cable with paper insulation.

DOW ENDURANCE materials have a 40 year predicted life and, therefore, offer a lower life-cycle cost cable solution. The XLPE insulation enhances power supply reliability, leading to fewer maintenance requests and less time devoted to repair work.

In addition, the products result in less soil and groundwater contamination following the dismantling of existing oil-filled cable. They also are less likely to create a man-made environmental disaster in the event of an accidental electrical oil spill.

Because the under soil in St. Petersburg moves, the 110 kV cable was encased in a concrete stall to help ensure the cable is well protected from potential ground motion and mechanical damage.

Sevkabel’s manufacturing know-how and expertise was credited with the on time delivery of the high voltage cables, which enabled new customers, notably in the city center, to access the grid. Four cable lines were completed and commissioned in 2011, and work began immediately on 25 to 30 more 35 kV lines to further increase capacity.

To date, Sevkabel has delivered 80 km of 110 kV cable to Lenenergo.

Robert Tarimo is associate marketing director for Dow Electrical & Telecommunications.

 
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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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