The tower bodies are produced from roll-formed steel parts with height-variable cross-sections. This tower is also significantly lighter than concrete supports. The tower body is made in three sections; two of the sections are manufactured from solid steel plate and the remaining section is a lattice design. These features make it possible to climb the tower with ease and eliminate closed corrosion-danger cavities.

Figure 4 shows a schematic diagram of the PS10P-18 tangent support, and Fig. 5 shows a section of an overhead line constructed around such supports. The S10P steel supports offer the following advantages over concrete supports previously used as the standard for MV overhead lines:

• Increased service life, estimated at more than 50 years

• Increased span lengths

• Increased inter-phase conductor separation, 230 cm (7.5 ft) compared to the 130 cm (4 ft) for concrete towers, diminishes inter-phase conductor clashing risk on longer spans

• Suspension insulation eliminates insulator fracture and conductor bundle failure

• Lightweight supports, 300 kg (660 lb) compared to 1150 kg (2535 lb) for concrete towers, makes it possible to reduce traffic volume and facilitates handling and installation

• Reduced probability of damage during transportation and erection

• Quality control of handling and installation is not required

• Steel supports facilitate easy climbing and do not require special equipment or lifting mechanisms

• The supports suffer no leakage-current corrosion

• Increased span lengths coupled with the use of lightweight supports simplify the line assembly.

Overall, the major advantage of the S10P steel supports compared to the 6-kV to 10-kV concrete towers is reliable performance and prolonged service life.

The improved reliability together with the economies identified in construction costs, use of resources and construction time period associated with the use of S10P steel supports for 6-kV to 10-kV overhead lines have resulted in the fast and wide-scale introduction of these supports on circuits supplying oil and gas enterprises in those regions with complex geological and severe climatic conditions.

In 2002, the GAZPROM Corp. (Moscow, Russia) adopted and selected as standard the construction of 6-kV to 10-kV overhead lines on S10P steel supports, for those circuits supplying gas production and transportation plants in Russia's northern regions. By December 2005, MV overhead lines totaling some 2500 km (1550 miles) constructed to the new standard were in commission, supplying GAZPROM plants, other oil-and-gas enterprises as well as circuits operated by RAO UES of Russia. To date, no fault outages attributable to support failure on the MV circuits constructed in accordance with the new standard have been recorded.

Line supports were the cause of the majority of supply interruptions on the 6-kV to 10-kV overhead lines in Russia. A new approach to these circuits has been deployed, including new steel supports from roll-formed steel parts of variable cross-section and the use of suspension-type polymeric insulation with enlarged inter-phase separations.

Dr. Yuri Hunger was awarded his electrical engineer qualifications by the Novosibirsk Electrotechnical Institute, where he held appointments as engineer researcher and associate researcher, and served as a member of the teaching staff in the power faculty. Hunger continued his research work at the Siberian Power Research Institute until 1991, when he was appointed the general director of J.S.C. ELSI Consulting Engineering. In 2000, he was appointed general director of ELSI Group. elsi@elsi.ru

Dr. Anatoly Zevin studied at the Dntpropetrovsk Construction Institute, where he received his construction engineering qualification. Zevin taught at the Bryarsk Technological Institute before joining the Sevzapenergoset project, where he held the positions of senior staff scientist and group chief. Zevin now holds the post of scientific adviser for J.S.C. ELSI Consulting Engineering.

Dr. Garry Schwarz was awarded his electrical engineering qualifications by the Toliatty Polytechnical Institute and then joined GAZPROM. During his long career with the company, Schwarz has served as head of the power department in Urengoygazenergo, as deputy general director of J.S.C. Electrogaz and as deputy head of the power department in GAZPROM. Schwarz now heads the power department at GAZPROM.

Sergey Golubev received his electrical engineering qualifications from the Gorkiy Polytechnical Institute before joining GAZPROM. To date, he has held the positions of main power-supply engineer in the Sredaztransgaz Gas Pumping Station, and chief engineer and deputy general director of the Yamburg Regional Power Department of Yamburggazdobicha. Golubev now serves as group chief of the power department in GAZPROM.