Electricity distribution protection systems applications

The available short-circuit current at any point in an electrical system is the worst-case or maximum short-circuit current that can flow under fault conditions. To safely apply overcurrent devices within their interrupting ratings, it is necessary to calculate the available short circuit currents at various points of application in an electrical distribution system.The procedure to calculate the magnitude of the fault current is described in various publications available from circuit protective device manufacturers. 

For the application of cathodic protection to structures to be protected, the initial considerations are best made at the early design and preconstruction phase of the structure. For underground structures, it may be necessary to visit the proposed site, or for pipelines the proposed route, to obtain additional information on low-resistivity areas, availability of electric power, and the existence of stray dc current or other possible interactions. Other considerations will include fundamental design decisions to select the type of system and the most suitable type of anode appropriate to that system. In addition, it will be a requirement to determine the size and number of the power sources or sacrificial anodes and their distribution on the structure. Other factors that must be considered to ensure that cathodic protection is applied in the most economic and reliable manner are given as follows. 

In an industrial setting, fuel cells are mostly used for combined heat and power (CHP)— partly also for combined cooling, heat and power (CCHP). If the latter is also used for fire protection, the fuel ceU system combines four applications in a single unit. The system as a whole, named QuattroGeneration, is already sold and distributed commercially (Fig. 8.4). The name QuattroGeneration stands for its four products electricity, heating, cooling, fire protection. 

Zinc spraying of plastics or phenolic-impregnated asbestos is used to provide reflecting surfaces, and the large open-air dishes used in electronic applications are so coated. In impressed current protection of rebar in concrete, the exterior of the concrete is sometimes zinc sprayed (Morrow, 1991) to give a uniform current distribution (see subsection on impressed current systems in Section II. E) in such cases, it is often policy to avoid direct electrical connection between zinc and rebar, since the consequent use of zinc as a sacrificial anode could be counterproductive if only a limited amount of zinc is present to protect large areas of steel. 

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