GENERAL
This training document covers the general technical information on “Earthing System” in
residential, commercial and industrial installations, especially for Oil and Gas plants.
Detailed and more specialized data and specifications on earthing systems shall be
provided to electrical and instrument trainees later during the period of specific course.
Sections and paragraphs which are marked with asterisk (*) are more or less specialized
and therefore shall be skipped to be offered during the specific course.
١.١. Concept of Earthing Systems
All the people living or working in residential, commercial and industrial installations,
particularly the operators and personnel who are in close operation and contact with
electrical systems and machineries, should essentially be protected against possible
electrification. To achieve this protection, earthing system of an installation is defined,
designed and installed according to the standard requirements. Also, earthing system in an
oil gas complex shall provide the best protection system against sparking, which could lead
to disastrous explosions.
١.١.١. Under earthing system measures, the metal covering body and enclosure of all
the equipments are connected to each other as a grid by means of appropriate
conductors to establish an equal zero level potential among all the points which may
come in contact with the operators. Zero potential, which is built-up and applied to the
earthing conductor grid, is produced by special earth wells and their associated
accessories.
١.١.٢. Further to protection against the risks of electrification, earthing system is
particularly installed in industrial areas where equipments are in possible exposure to
explosive material and gas such as oil and gas plants. Difference of electrical potential
between the equipment, and machinery is inevitably a source of spark, which definitely
leads to an explosion in presence of explosive gases. Therefore a properly installed
earthing systems can provide an equal zero electrical potential throughout the plant
equipment, thus eliminating the risks of sparks and explosions.
١.١.٣. Lightning, with its high electrical potential, is one of the most serious and
dangerous environmental threats, which could cause sever damages to both human
life and the installations. Lightning arresters, as part of the earthing system in an
installation, are the protective devices, which avert the risks of lightnings.
٢. EARTHING SYSTEM COMPONENTS
Earthing system in an installation is normally comprised of these components:
٢.١. Earth wells and accessories
٢.٢. Earthing grid conductors
٢.٣. Marshalling earth buses (earthing distribution buses)
٢.٤. Earthing wires and cables.
٢.٥. Lightning arresters and accessories
٣. EARTH WELLS AND ACCESSORIES
Earth wells for an specific building or installation are actually the location, where the pure
zero potential is provided and practically act as drain pits for any rush current which
accidentally appears in the earthing system grid in the event of an earth fault (connection of
electrical live parts to the earthing system).
٣.١. Earth Well Components
Depending on the soil conductivity of the location in which the earth wells are installed and
also depending on the required technical specifications of the earthing system, different
types of components can be used to set up an earth well. Followings are the prime
components and accessories of an earth well.
٣.١.١. Earth rod
٣.١.٢. Earth plate
٣.١٣. Earthing clamp
٣.١.٤. Earthing rod coupling
٣.١.٥. Earthing rod tip