Читать книгу Practical Power Plant Engineering - Zark Bedalov - Страница 73

The major part of the power distribution between the main substation and the remote areas and the main process plant will be by overhead distribution lines. The lines will follow the most direct routes or along the roads to facilitate ease of construction and maintenance. The 13.8 kV feeders will be laid out either as radial feeders or ring main loop feeders to connect several unit substations and other major loads in a loop fed from two different sources.

The MV distribution lines will use wood poles and wood cross‐arms (see Figure 2.12). In tropics, use concrete poles and steel cross‐arms (see Chapter 9). The distribution lines will use Hawk ACSR 466 kcmil (660 A), or Partridge ACSR 266 kcmil bare conductor having more than 470 A capacity in free air and high pulling strength. High capacity conductors are used not only to maintain low voltage drops but also for their tensile strength for pulling and to be able to implement longer spans between poles.

The lines will be protected from lightning by an overhead shield wire on the top. The shield wire, popularly called overhead power ground wire (OPGW), will also contain fiber optic single mode, multicore cable inside it. All the metallic pole hardware will be grounded to a pole ground wire, which will then be led to the pole grounding rods. Depending on the soil conditions, the grounding rods will be installed at every pole in the dry areas and every several poles in the moist, low soil resistive areas.

Figure 2.12 Distribution line.