Underwater cable laying

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 2. Sewerage of electricity

Cable lines up to 220 kV. Underwater cable laying

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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2.3.136. When cable lines cross rivers, canals, etc., cables should be laid mainly in areas with a bottom and banks that are little prone to erosion (crossing streams - see 2.3.46). When laying cables through rivers with an unstable channel and banks subject to erosion, the burial of cables into the bottom should be done taking into account local conditions. The cable laying depth is determined by the project. Laying cables in the areas of piers, berths, harbors, ferry crossings, as well as regular winter moorings of ships and barges is not recommended.

2.3.137. When laying cable lines in the sea, data on the depth, speed and style of water movement at the crossing point, prevailing winds, the profile and chemical composition of the bottom, and the chemical composition of water should be taken into account.

2.3.138. Cable lines should be laid along the bottom in such a way that they are not suspended in uneven places; sharp protrusions must be removed. Shoals, stone ridges and other underwater obstacles on the route should be bypassed or trenches or passages should be provided in them.

2.3.139. When cable lines cross rivers, canals, etc., cables, as a rule, must be buried in the bottom to a depth of at least 1 m in coastal and shallow water areas, as well as on shipping and rafting routes; 2 m when crossing oil-filled cable lines.

In reservoirs where dredging works are periodically carried out, cables are buried in the bottom to a mark determined in agreement with water transport organizations.

When laying oil-filled cable lines 110-220 kV on navigable rivers and canals, in order to protect them from mechanical damage, it is recommended to fill trenches with sandbags, followed by throwing stones.

2.3.140. The distance between cables buried in the bottom of rivers, canals, etc. with a reservoir width of up to 100 m, is recommended to be at least 0,25 m. Newly constructed underwater cable lines should be laid at a distance of at least 1,25 depth from existing cable lines reservoir, calculated for the long-term average water level.

When laying low-pressure cables in water at a depth of 5-15 m and at a flow velocity not exceeding 1 m/s, it is recommended to take the distances between the individual phases (without special fastenings of the phases to each other) at least 0,5 m, and the distances between the extreme cables of parallel lines - at least 5 m.

With underwater laying at a depth of more than 15 m, as well as at flow rates of more than 1 m/s, the distances between individual phases and lines are taken in accordance with the project.

When oil-filled cable lines and lines up to 35 kV are laid in parallel under water, the horizontal distance between them in the light must be at least 1,25 times the depth calculated for the long-term average water level, but not less than 20 m.

The horizontal distance from cables buried in the bottom of rivers, canals and other water bodies to pipelines (oil pipelines, gas pipelines, etc.) should be determined by the project depending on the type of dredging performed when laying pipelines and cables, and be at least 50 m. It is allowed to reduce this distance to 15 m in agreement with the organizations in charge of cable lines and pipelines.

2.3.141. On shores without improved embankments, at the place of the underwater cable crossing, a reserve of at least 10 m in length for river and 30 m for sea laying, which is laid in a figure of eight, should be provided. On improved embankments, cables should be laid in pipes. In the place where the cables exit, as a rule, cable wells should be arranged. The upper end of the pipe must enter the coastal well, and the lower end must be at a depth of at least 1 m from the lowest water level. Onshore sections of the pipe must be firmly sealed.

2.3.142. In places where the channel and banks are subject to erosion, it is necessary to take measures against the exposure of cables during ice drifts and floods by strengthening the banks (paving, dams, piles, sheet piles, slabs, etc.).

2.3.143. Crossing of cables under water is prohibited.

2.3.144. Underwater cable crossings must be marked on the shores with signal signs in accordance with the current rules for navigation along inland navigation routes and sea straits.

2.3.145. When laying three or more cables up to 35 kV in water, one reserve cable should be provided for every three working ones. When laying oil-filled cable lines and single-phase cables in water, a reserve must be provided: for one line - one phase, for two. lines - two phases, for three or more - according to the project; but at least two phases. Reserve phases must be laid in such a way that they can be used to replace any of the active working phases.

See other articles Section Rules for the installation of electrical installations (PUE).

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