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GENERALThis training document covers the general technical information on “Earthing System” inresidential, commercial and industrial installations, especially for Oil and Gas plants.Detailed and more specialized data and specifications on earthing systems shall beprovided to electrical and instrument trainees later during the period of specific course.Sections and paragraphs which are marked with asterisk (*) are more or less specializedand therefore shall be skipped to be offered during the specific course.١.١. Concept of Earthing SystemsAll the people living or working in residential, commercial and industrial installations,particularly the operators and personnel who are in close operation and contact withelectrical systems and machineries, should essentially be protected against possibleelectrification. To achieve this protection, earthing system of an installation is defined,designed and installed according to the standard requirements. Also, earthing system in anoil gas complex shall provide the best protection system against sparking, which could leadto disastrous explosions.١.١.١. Under earthing system measures, the metal covering body and enclosure of allthe equipments are connected to each other as a grid by means of appropriateconductors to establish an equal zero level potential among all the points which maycome in contact with the operators. Zero potential, which is built-up and applied to theearthing conductor grid, is produced by special earth wells and their associatedaccessories.١.١.٢. Further to protection against the risks of electrification, earthing system isparticularly installed in industrial areas where equipments are in possible exposure toexplosive material and gas such as oil and gas plants. Difference of electrical potentialbetween the equipment, and machinery is inevitably a source of spark, which definitelyleads to an explosion in presence of explosive gases. Therefore a properly installedearthing systems can provide an equal zero electrical potential throughout the plantequipment, thus eliminating the risks of sparks and explosions.١.١.٣. Lightning, with its high electrical potential, is one of the most serious anddangerous environmental threats, which could cause sever damages to both humanlife and the installations. Lightning arresters, as part of the earthing system in aninstallation, are the protective devices, which avert the risks of lightnings.٢. EARTHING SYSTEM COMPONENTSEarthing system in an installation is normally comprised of these components:٢.١. Earth wells and accessories٢.٢. Earthing grid conductors٢.٣. Marshalling earth buses (earthing distribution buses)٢.٤. Earthing wires and cables.٢.٥. Lightning arresters and accessories٣. EARTH WELLS AND ACCESSORIESEarth wells for an specific building or installation are actually the location, where the purezero potential is provided and practically act as drain pits for any rush current whichaccidentally appears in the earthing system grid in the event of an earth fault (connection ofelectrical live parts to the earthing system).٣.١. Earth Well ComponentsDepending on the soil conductivity of the location in which the earth wells are installed andalso depending on the required technical specifications of the earthing system, differenttypes of components can be used to set up an earth well. Followings are the primecomponents and accessories of an earth well.٣.١.١. Earth rod٣.١.٢. Earth plate٣.١٣. Earthing clamp٣.١.٤. Earthing rod coupling٣.١.٥. Earthing rod tip
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