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Naum Lukin
Naum Lukin

IEEE Guide For Safety In AC Substation Grounding



Outdoor ac substations, either conventional or gas-insulated, are covered in this guide. Distribution, transmission, and generating plant substations are also included. With proper caution,the methods described herein are also applicable to indoor portions of such substations, or to sub-stations that are wholly indoors. No attempt is made to cover the grounding problems peculiar to dc substations. A quantitative analysis of the effects of lightning surges is also beyond the scope of this guide.




IEEE Guide for Safety in AC Substation Grounding



Learn More 1246-2020 IEEE Guide for Temporary Protective Grounding Systems Used in Substations The design, performance, use, testing, and installation of temporary protective grounding systems, including the connection points, as used in permanent and mobile substations, are covered in this guide.


Learn More 1268-2016 IEEE Guide for Safety in the Installation of Mobile Substation Equipment Information pertaining to the installation of mobile substation equipment up to 245 kV is provided in this guide.


Learn More 1246-2002 IEEE Guide for Temporary Protective Grounding Systems Used in Substations The design, performance, use, testing, and installation of temporary protectivegrounding systems, including the connection points, as used in permanent and mobile substations,are covered in this guide.


Learn More 1246-2011 IEEE Guide for Temporary Protective Grounding Systems Used in Substations The design, performance, use, testing, and installation of temporary protective grounding systems, including the connection points, as used in permanent and mobile substations, are covered in this guide.


Learn More 1268-2005 IEEE Guide for Safety in the Installation of Mobile Substation Equipment Information pertaining to the installation of mobile substation equipment up to 245 kV is provided in this guide.


This guide is primarily concerned with outdoor ac substations, either air-insulated or gas-insulated. With proper caution, the methods described herein are applicable to indoor portions of such substations, or to substations that are wholly indoors. No attempt is made to cover the grounding problems peculiar to dc substations. A quantitative analysis of the effects of lightning surges is also beyond the scope of this guide.


Abstract: This guide is primarily concerned with outdoor ac substations, either conventional orgas-insulated. These include distribution, transmission, and generating plant substations. Withproper caution, the methods described herein are also applicable to indoor portions of suchsubstations, or to substations that are wholly indoors. No attempt is made to cover the groundingproblems peculiar to dc substations. A quantitative analysis of the effects of lightning surges isalso beyond the scope of this guide.


This guide is primarily concerned with outdoor ac substations, either conventional or gas-insulated.Distribution, transmission, and generating plant substations are included. With proper caution, the methodsdescribed herein are also applicable to indoor portions of such substations, or to substations that are whollyindoors.


The concept and use of safety criteria are described in Clause 1 through Clause 8, practical aspects ofdesigning a grounding system are covered in Clause 9 through Clause 13, and procedures and evaluationtechniques for the grounding system assessment (in terms of safety criteria) are described in Clause 14through Clause 20. Supporting material is organized in Annex A through Annex H.


This guide is primarily concerned with safe grounding practices for power frequencies in the range of50 Hz to 60 Hz. The problems peculiar to dc substations and the effects of lightning surges are beyond thescope of this guide. A grounding system designed as described herein will, nonetheless, provide somedegree of protection against steep wave front surges entering the substation and passing to earth through itsground.


decrement factor : An adjustment factor used in conjunction with the symmetrical ground fault currentparameter in safety-oriented grounding calculations. It determines the rms equivalent of the asymmetricalcurrent wave for a given fault duration, tf , accounting for the effect of initial dc offset and its attenuationduring the fault.


main ground bus : A conductor or system of conductors provided for connecting all designated metalliccomponents of the gas-insulated substation (GIS) to a substation grounding system.


Usually, a protective surface layer of high resistivity (e.g., gravel) is used (as represented in Figure 5), to minimise the current passing through the human body, providing a safety to individual inside the substation.


American National Standard National Electrical Safety Code, ANSI/IEEE C2-2012 contains guidelines for the dimensions of access and working space about electric equipment in substations. Installations meeting the ANSI provisions comply with paragraph (b) of this section. The Occupational Safety and Health Administration will determine whether an installation that does not conform to this ANSI standard complies with paragraph (b) of this section based on the following criteria:


American National Standard National Electrical Safety Code, ANSI/IEEE C2-2002 contains guidelines for the dimensions of clearance distances about electric equipment in substations. Installations meeting the ANSI provisions comply with paragraph (f)(1) of this section. The Occupational Safety and Health Administration will determine whether an installation that does not conform to this ANSI standard complies with paragraph (f)(1) of this section based on the following criteria:


Understandhow to calculate step and touch potentials for a reliable and efficientgrounding grid for outdoor substations using the formulas contained inIEEE Std80-2000. The SKM Ground Mat software will be used to provide a hands-onexercise designing an outdoor substation grounding grid and solve agrounding grid challenge.


To confirm reliability of permanent grounding connections, IEEE 837 is the most rigorous and highly regarded grounding connection testing standard in the world. Specifically developed for substation grounding, this standard is considered state of the art for all who are concerned about safety and reliability of grounding.


One of the fundamental parts of the electrical substation is a ground grid which provides proper grounding of all apparatus in substations (including transformers, circuit breakers, capacitor banks, steel tower structures, etc.). The grounding grid is placed underneath the entire electrical substation which has a dual purpose: operating grounding, carrying faulty currents into the earth without affecting the operation of any protective equipment, and safety for personnel in the vicinity assuring that they are not exposed to an electric shock which could result from the excessive step or touch potentials.


Over time, this grid can deteriorate due to corrosion, ground movements, grid fatigue, high energy conductance (lightning), and construction damage. All this can cause various safety problems. Since the grounding grid is buried underground, it is difficult to inspect and verify if there are corrosion and connection issues present. For this reason, it is beneficial to have a non-destructive testing method capable of verifying the integrity of the grounding grid.


There are several available test methods for inspection and condition assessment of substation ground grid. It is important to mention that different methods can be combined and used together to provide more reliable information about ground grid conditions. Commonly used test methods for grounding grid condition assessment are:


The DV Power GGT device is specially designed for this test. GGT is a powerful DC current source that provides DC test currents up to 300 A. High output voltage (9 V DC) enables testing with long cables (e.g. 70 m) and measurement of a wide range of resistance values [3]. Long test cables are very important for this application because they simplify the test procedure. The test device can be placed in one place during the measurement of all grounding points in the substation. Since substation contains hundreds of grounding points features that save time and simplify work are crucial.


The integrity test is used to detect any bad connection, open circuit, or isolated structure or equipment in a substation grounding system. According to the standard IEEE Std 80-2000, a typical test set should contain the current source up to 300 A, voltage and current measurement channels, and two test leads. One of the two test leads is connected to a reference ground point and the other test lead is connected to a ground point to be tested. The test device generates the current between the connection points and measures the voltage drop across the ground circuit. The current that flows down to the ground grid should be measured with a proper current clamp. Keeping the reference point connected, the second test lead is moved to grounding points of other equipment and structures until the entire substation ground grid is tested.


Conclusions about the substation grounding can also be made by comparing the obtained resistances with the results from the previous testing. In case the previous results do not exist then they should be compared with other relative resistances within the same substation. The resistance values can be taken directly and easily from the GGT-M module.


In this case study, the integrity of a complete ground grid in a 110/35/10 kV substation was tested, where the interruptions of the several connections to the mutual grounding were detected (metal reflector towers and substation gantry towers), exposing the personnel to the possible dangerous touch potentials (electrical shock).


The purpose of this test is to verify that a new part of a ground grid in the mentioned substation has been properly installed and at the same time to check the integrity of the existing part of a ground grid. Whenever safety is a concern, particularly in older substations, the ground integrity test for verifying the continuity of the grid at any point should be performed before any other tests. 041b061a72


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