by on March 9, 2019
All transmission lines consist of structures mostly of the same material but of different sizes, insulator, line angle and loading configurations. These can be grouped into a “family’’ of structures specific for the project. Once the basic structure type (usually tangent) has been established, the “family’’ can be set up by adding systems of other configurations, specifically angle and deadend structures. In other words, the structure family basically contains tangent, angle (small, medium, larg...
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by on March 8, 2019
This section covers the structural and material properties of various elements that comprise a typical transmission structure. The three basic construction materials for transmission structures are wood, steel and concrete, although fiber glass (composite) poles and cross arms are being increasingly used for both transmission and distribution lines. Composite cross arms are also becoming popular for distribution under-build circuits on transmission poles given the ease of installation and struct...
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by on March 6, 2019
Transmission structures, whether wood, steel, lattice, concrete or composite, are one of the most visible elements of an electrical power transmission system. Regardless of material, they serve a single purpose: supporting the insulators, wires and equipment. The choice of a particular type of structure – material and configuration – for a transmission line, however, depends on several factors such as electrical, spatial, structural and economy. Electrical factors include voltage, number of c...
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by on March 2, 2019
Each structure must be securely embedded or anchored into the ground and facilitate safe transfer of structure loads to the ground strata below. To determine foundation requirements, the engineer must first evaluate the nature and condition of the soil in the vicinity of the structure. The choice of eventual foundation type will further depend on geotechnical characteristics of strata underneath, structure material, configuration, loads, constructability and economy. A majority of tangent poles ...
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by on February 26, 2019
3-) Shielding When lightning strikes a transmission line, it may hit either the overhead ground wire or a phase conductor. If a conductor is hit, there will certainly be a flashover of the insulation. To prevent and minimize such an occurrence, the overhead ground wire is used to intercept the lightning strike, “shielding’’ the conductors. To optimize this shielding, the shielding angle (see Figure 2.4) must be 30◦ or less. If a location is known to have an unusually high exposure to lightnin...
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by on February 25, 2019
2-) Electrical Design Overhead transmission lines are designed to satisfy a wide range of local and regulatory requirements. While the demands of these requirements vary from location to location and are often line-specific, the underlying principle is one of legality, safety and reliability.   2.a) Regulatory Codes These relate to the local and national standards pertaining to both electrical operations as well as other land use considerations. For example, in areas close to runways...
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