Air, earth and water - three media for a power line

Specialists from Sverdlovenergo branch have accomplished assembly works on the cable crossings of 110 kV aerial line Degtyarka – Verkhnie Sergi with a branch line to 110/6 kV substation Mariinskaya and 110 kV line Degtyarka – Polevskaya with a branch line to 110/35/6 kV substation Verkhnie Sergi across the bed of the Mariinsk reservoir.

The constructing technology has earlier been used only in Irkutsk (line crossing across Lake Baikal) and St. Petersburg (line crossing across the Gulf of Finland). It was the first time when a similar line was installed in the Urals federal district.

The project is unique due to unconventional technologies and short construction terms

The uniqueness involved both unconventional technologies and short construction period. As often happens, many factors of the project – construction period, conditions and prerequisites - were dictated by the nature.

The ice has broken up...

A 110 kV line Degtyarka – Verkhnie Sergi with a branch line to 110/6 kV substation Mariinskaya and a 110 kV line Degtyarka – Polevskaya with a branch line to 110/35/6 kV substation Verkhnie Sergi were constructed in 1980-s. The lines play an important role in energy supply of Verkhnie Sergi, Mariinsk and Krasnyi Yar settlements. Moreover, Mariinsk and Kransyi Yar had no backup power sources. The lines were jointly suspended and were carried by two-circuit towers (mainly UMT, PB 110-6, PB 110-2). The crossing over the Mariinsk reservoir was mounted on 3 two-circuit metal towers. Two towers dominated over the banks of the reservoir, the third one resided in the middle of the reservoir. The overall crossing length was approx. 1.2 km.

At the end of April, flood and stormy wind triggered the ice to dislodge the transmission-tower footing. The tower has submerged. The line tripping has lead to blackout of 110 kV substation Mariinskaya and consumers located in Mariinsk and Krasnyi Yar (approx. 13 440 inhabitants, several social objects and vital infrastructure).

...and the work began

The primary task for our Sverdlovenergo specialists was to restore energy supply.

Factoring in weather conditions, materials availability and possible future repeat of the situation, we agreed that a quick reconstruction of the crossing in its original form was out of the question. Accordingly, during the first stage the Company strained every nerve to provide temporary power supply to consumers via 10 kV lines from other settlements - within 3 days we built 10 kilometers of a 10 kV line from 35 kV substation Petrovskaya to Ledyanka settlement. Networks in two settlements were coupled via a 10/6 KV tie-in transformer installed on substation Mariinskaya. Within the same days we prepared a technical solution regarding the crossing. The solution was based on our background experience and made similar future failures impossible.

Submarine cable

To arrange the crossing we decided to use a 1.4 km-long one-piece connector-free cable. 1.3 km of the cable ran in a protected plastic pipe resting on the bed of the reservoir at a depth of 18 m. To complete the project Sverdlovenergo specialists used cutting-edge equipment and technologies that were never used earlier in the Urals federal district. We mounted 12 pilot sealed-in OF fixed cable coupling MKV 126 (produced by Arkasil SK) and 12 new-generation surge suppressors on metal long-span angle-tension two-circuit towers located on the banks. Besides, we used modern ecology-friendly technologies: submarine pipe and cable (PvPu2g 1х300 (gzh/150-64/110 by Estralin ZVK) were fabricated according to the special order from environment-friendly materials that do not deteriorate the quality of water in the Mariinsk reservoir.

We also involved technical solutions that may help us quickly restore energy supply to consumers in case one of the cables fails: during the construction we installed a reserve pipe for a quick draw-in of a new cable while the existing cable is being restored. We also installed separate off-size ducts for fiber optic cables to lay substation communication buses in perspective. Over 100 specialists (both our personnel and workers from other companies) were involved in the project. Due to the uniqueness and high complexity of the project the directors of ZES production unit and Sverdlovenergo personally supervised the installation.

The construction of a crossing took 4 months

The installation was difficult both due to landscape and tight schedule. The construction of a crossing across the Mariinsk reservoir took 4 months from the dismantling of damaged towers to putting the new cable into operation. We spent RUR 190 mln. on the project.

Igor Chikrizov
Deputy Minister for Energy Sector,
Housing and Utilities Infrastructure
in the Sverdlovsk region

The agility shown by the colleagues from Sverdlovenergo during the liquidation of the spring incident and their work pace deserve a very high praise. Now it is safe to say that the measures will make energy supply to residents of Revda and Nizhnie Sergi urban districts more reliable both during this heating season and for years ahead.