by on February 27, 2019
1-) Structure spotting Prior to any design, the engineer must establish the alignment of the transmission line taking into consideration the various criteria. These criteria include property boundary issues, soil conditions, road and other clearances, regulatory issues, environmental concerns, costs, impact on public property, aesthetics and construction access. Potential structure locations are identified along the chosen alignment using structure spotting process. Structure spotting is the ...
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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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by on February 22, 2019
The process of designing an overhead transmission line involves various phases or sub-processes. From a Project Management (PM) perspective, there are five (5) main sequential phases as shown in Figure 1.9. This blog is concerned with Detailed Engineering Design, which includes structures and foundations. The basic contents of each of the sub-processes are shown in Figures 1.10, 1.11 and 1.12. The other sub-processes will be discussed in the companion volume. For small projects, a PM-base...
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by on February 22, 2019
Historically, the term “transmission structures’’ usually implied iron or steel latticed towers. The early “pylons’’ dating back to 1829 were iron structures; the basic shape of later pylons was mostly inspired by the famous Eiffel Tower. Figure 1.1 shows some of the early shapes and forms of transmission structures. Single wood poles directly-embedded into the ground formed the bulk of the transmission structures family for a greater part of the 20th century. France in the late 1900s and...
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by on February 21, 2019
   Count Alessandro Volta (1745−1827), the Italian physicist and inventor of the battery, was the first person to suggest the idea of a transmission line by writing in 1777 “… the igniting spark could be transported from Como to Milan with barbed wire supported by wooden poles planted here and there …’’ The structures in use those days for telegraph poles were wooden poles with zinc iron barbed wire supported by porcelain insulators fixed to the pole with screws and bolt hooks (TERNA, 2013). The...
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