The terms earth and earthing have been used in this code irrespective of reliance being placed on the earth itself as a low impedance return path of the fault current. A total area enclosed by earth grid h depth of earth grid conductor for calculation of grid current, equation 5 is used n number of parallel conductor in one direction where i g maximum grid current 3i o symmetrical fault current in substation for conductor sizing in a s f current diversity factor. Earthing mat design for a power substation ms excel. The sizing of earthing conductors should always be performed, but touch and step potential calculations per ieee std 80 for earth faults with a. Earthing mat design for substation spreadsheet photo by input fields as per ansiieee std 801986 code.
For instance a retaining wall can be used to retain fill along a slope or it can be used to. How to determine correct number of earthing electrodes. However, it is relatively easy to calculate epr if the impedance of the earth mat is known. That part of the earthing system which interconnects the overall metallic parts of electrical installation e. If the mat is being installed in a rocky soil strata, it is advised to pour 600 mm virgin soil below the mat and a 200 mm dia hole for installation of electrodes filled. Earthing is a fastgrowing movement based upon the discovery that connecting to the earths natural energy is essential for vibrant health.
The functions of grounding systems or earth mat in include. Scribd is the worlds largest social reading and publishing site. An introduction to grounding calculations and why they are. Substation earthing system grounding system earthing mat. Calculation of important design parameters for grounding systems in. Pdf earth mat design for 233kv substation in rivers state. B102407 designing for a low resistance earth interface grounding roy b. Earth pressure and retaining wall basics for nongeotechnical. They are often used for potential grading and are a preferred option on installations such as telecommunications towers where touch and.
Earth pressure and retaining wall basics for nongeotechnical engineers richard p. Earth electrode conductive part, which may be embedded in the soil or in a specific conductive medium, e. For example, when all electricity is generated onsite and the hvmvlv earthing systems are interconnected, then there is no need to do a touch and step potential calculation. Grounding design calculations part seventeen electrical. Earthing mat is made by joining the number of rods through copper conductors.
Earth mat design for a 66kv substation international journal of. Abstractthispaper describes the design ofan earthing calculation is a good, software tools ensure a detailed design system for agas insulated switchgear gis substation using so that the earth mat is neither underdesigned hence safe nor cymgrd software. Pdf guideline for earthing of buildings and industrial. Earthing systems fundamentals of calculation and design figure 2 earth resistivity. The copper earth mat should be surrounded by at least 300 mm virgin soil at every point i. Specific resistance is calculated on the basis of measured values of soil resistivity. The earthing mat has to be designed for the site conditions to have a low overall impedance and a current carrying capacity consistent with the fault current magnitude. Nov 27, 2011 earth resistance value is directly proportional to soil resistivity value.
Components of electrical earthing system earth continuity conductor or earth wire. How to determine correct number of earthing electrodes strips, plates and pipes part 1 there is no general rule to calculate the exact number of earth pits and size of earthing strip, but discharging of leakage current is certainly dependent on the cross section area of the material so for any equipment the earth strip size is calculated. Guidelines on earthinggroundingbonding in the oil and gas. The grounding system in substation is very important. Basic grounding concepts and calculation inputs will be introduced, and. Measurement of earth resistance three point method. Etap model for earth mat design etap model for earth mat design. One way of limiting the gpr in high fault current substations is by adding more copper in the earth mat, thus reducing the earth impedance. Earthing mat is mostly used in a placed where the large fault current is to be experienced.
Provide the ground connection for connecting the neutrals. Ieee guide for safety in ac substation grounding ieee std 802000. Earth mat design for 233kv substation in rivers state. Read about design of substation earthing system here. Etap model for earth mat design etap model for earth mat.
Design of earthing grounding system in a substation grid. Earth mat calculations electrical resistivity and conductivity. Transmission and distribution earth current considerations. The earthing system is designed so that the allowable touch and step voltages. In such a case, all earth faults would return to the source via the earthing system notwithstanding some small leakage through earth. Use of emix, a conductive earthing compound, with earth mats, will always improve the earth resistance. Weber course content content section 1 retaining walls are structures that support backfill and allow for a change of grade. B main earthing busbar and fixed earthing terminal. The electrical earthing is done by connecting the noncurrent carrying part of the equipment or neutral of supply system to the ground. The buried earth grid design is based on the overdesigned hence cost effective. A commonly used practice to determine the zerosequence impedance is by using carsons equation and using a typical value of 100 m as earth resistivity 6,8. An earth electrode and earth electrode resistance are defined in bs 7671 as.
Earth mat ground mat lattice copper earth mat lattice. The earthing system is an essential part of power networks at both high and lowvoltage levels. Earthing mat design for a power substation ms excel spreadsheet. While designing an earth mat, the following step is taken into.
To minimize the danger of high step or touch voltages in critical operating area or places that are frequently used by people 3. This can be found from the power systems studies or from manual calculation. Omeje, department of electricalelectronic engineering university of port harcourt, port harcourt, nigeria. As a matter of fact, the earth now rarely serves as a part of the return circuit but is being used mainly for fixing the voltage of system neutrals. Leon markwell, senior engineer at the iet, discusses the inspection and testing of earth electrodes. Space saving on the ground level due to substantial reduction of earth pits which. The sizing of earthing conductors should always be performed, but touch and step potential calculations. An important aspect of substation grounding system design is the calculation of the ground resistance offered by the grounding grid, and the values of the mesh. The cross section of the buried cable should calculated in accordance with the value of the phaseto earth short. This paper mentions the calculation of the desired parameters for. International journal of engineering trends and technology.
Lanzoni october 2007 introduction grounding or earthing is the art of making an electrical connection to the earth. Lattice copper earth mat ground mat these earth plates are renowned for high durability, tensile strength, corrosion resistance and high performance. The mathematical modelling of an earth mat for touch and step voltages inside and outside the confines of the earth mat is indeed a complex subject. What is the tolarable value of gprepr for earthing grid calculation. Substation earthing system design underground horizontal earth mesh matgrid the mesh is formed by placing mild steel bars placed in x and y directions in mesh formation in the soil at a depth of about 0. This is needed so that individuals who are walking in the area are not exposed to excessive voltages across the length of a stride step potential or when they touch a metallic structure reach potential.
Earthing is an important aspect of every substation construction. Substation absd equipotential earth mat application guide. Such type of system helps in limiting the ground potential. The substation earthing system comprises of a grid earth mat formed by a horizontal buried conductors. An introduction to grounding calculations and why they are necessary. A solid metallic plate or a system of closely spaced bare conductors that are. Standard crowfoot earth 25mm x 3mm copper tape x 5m long joined to a 70mm2 bcew tail 2m long. Earthing, earth electrodes, ground grid, 66 kv substations. Jan 07, 2009 an earthing system has two objectives. Guidelines on earthinggroundingbonding in the oil and gas industry first edition september 2016 published by energy institute, london the energy institute is a professional membership body incorporated by royal charter 2003. A company has to pay mat or tax as per normal provisions, whichever is higher.
Stay flexible by providing fixed earthing terminals for the external lightning protection system at the initial phase of construction. Earth mat design for 233kv substation in rivers state using etap c. The sizing of earthing conductors should always be. Research indicates that grounding the body affects physiological functioning in a variety of ways. Ensure safety to personnel in substations against electrical shocks.
Lattice copper which is available in various standards and is manufactured using high quality of copper which is of excellent tensile strength. Earthing system is made of a mesh of buried bare copper cable, with additional earth rods, and shall be calculated, being recommended to use ieee std. Because of this, we strongly recommend that any individual taking medication to thin the blood, regulate blood sugar, control blood pressure, or to supplement thyroid activity should consult with their doctor before beginning to. Important formulas for designing a substation grid earthing system. The effective solution generally requires computer modelling. Earth mat design calculation for 33 kv sstn for ms sukhbir agro energy ltd, shahjahanpur, u.
May 31, 2008 03 june 2008 the calculation is as per the provisions of sec. C connections to the external lightning protection system tip. The process of transferring the immediate discharge of the electrical energy directly to the earth by the help of the low resistance wire is known as the electrical earthing. Installation of copper earth mat in under ground metro staions. Pdf earth mat design for 233kv substation in rivers. The diamond shapes based on their logical answer yes or no will change the calculations sequence i. Connecting to the earth is easy and can be done outdoors by walking barefoot on the earths natural surfaces or indoors with one of our earthing products. The earthing system, sometimes simply called earthing, is the total set of measures used to connect an electrically conductive part to earth. An overstated fault current can result in an uneconomical substation earth mat design.
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