EPRI Substation Grounding Project Summaries of Published Reports 1981–2011
1025440
EPRI Substation Grounding Project Summaries of Published Reports 1981–2011 1025440 Technical Update, September 2012
EPRI Project Manager G. Gela
ELECTRIC POWER RESEARCH INSTITUTE 3420 Hillview Avenue, Palo Alto, California 94304-1338 PO Box 10412, Palo Alto, California 94303-0813 USA 800.313.3774 650.855.2121
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DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR (B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT. REFERENCE HEREIN TO ANY SPECIFIC COMMERCIAL PRODUCT, PROCESS, OR SERVICE BY ITS TRADE NAME, TRADEMARK, MANUFACTURER, OR OTHERWISE, DOES NOT NECESSARILY CONSTITUTE OR IMPLY ITS ENDORSEMENT, RECOMMENDATION, OR FAVORING BY EPRI. THE FOLLOWING ORGANIZATION PREPARED THIS REPORT: Electric Power Research Institute (EPRI)
This is an EPRI Technical Update report. A Technical Update report is intended as an informal report of continuing research, a meeting, or a topical study. It is not a final EPRI technical report.
NOTE For further information about EPRI, call the EPRI Customer Assistance Center at 800.313.3774 or e-mail
[email protected]. Electric Power Research Institute, EPRI, and TOGETHER …SHAPING THE FUTURE OF ELECTRICITY are registered service marks of the Electric Power Research Institute, Inc. Copyright © 2012 Electric Power Research Institute, Inc. All rights reserved.
ACKNOWLEDGMENTS The following organization prepared this report: Electric Power Research Institute (EPRI) 115 East New Lenox Road Lenox, MA 01240 Principal Investigator G, Gela
This report describes research sponsored by EPRI.
This publication is a corporate document that should be cited in the literature in the following manner: EPRI Substation Grounding Project: Summaries of Published Reports 1981–2011. EPRI, Palo Alto, CA: 2012.1025440. iii
PRODUCT DESCRIPTION The Electric Power Research Institute (EPRI) has been cond ucting research in the area of substation grounding and fault current managemen t for several decades. This research has resulted in a large number of reports and other products. To help users locate the results of EPRI’s research in substation grounding and fault current mana gement, an annual update is prepared containing brief descriptions of the products.
Objective The objective of this report is to provide summaries of the various research studies that have been performed by the EPRI Substation Grounding and Fault Current Management Project between the 1980s and the end of 2011. Approach The summaries of reports and products are based on Abstracts and/or Product Descriptions that are available on the EPRI website (www.epri.com). Results This report contains summaries and descriptions of various research reports and product studies developed by the EPRI Substation Grounding and Fault Current Management Project between the 1980s and the end of 2011. It also includes brief descriptions of EPRI reports published by other EPRI projects that might be of interest to the Substation Grounding and Fault Current Management Project funders. Applications, Value, and Use In addition to providing some high-level findings from EPRI research, the summaries included in this report should help the reader locate information on a particular topic or theme within the body of EPRI products that has been generated. Keywords Fault current management Grounding cables Smart Ground Multimeter Soil resistivity Substation grounding
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ABSTRACT This report contains summaries and descriptions of various research reports and product studies developed by the Electric Power Research Institute (EPRI) Substation Grounding and Fault Current Management Project between the 1980s and the end of 2011. The summaries of reports are based on the Abstracts and/or Product Descriptions available on the EPRI website (www.epri.com). In addition to providing some high-level findings, the su mmaries should help the reader locate information on a particular topic or theme within the body of EPRI products that has been generated. This report also includes brief descriptions of EPRI reports published by ot her EPRI projects that might be of interest to the Substation Grounding and Fault Current Management Project funders.
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CONTENTS 1 INTRODUCTION ..................................................................................................................1-1
Purpose and Scope of this Report......................................................................................1-1 Organization of this Report.................................................................................................1-1 2 SUBSTATION GROUNDING
REPORTS..............................................................................2-1 1024555 - Field Guide: Smart Ground Multimeter - 2011 ...................................................2-1 1021921 - Substation Grounding Grids: Corrosion of Connections - 2011..........................2-1 1020031 - Touch and Step Voltage Measurements on Field Installed Ground Grid Overlaid with Gravel and Asphalt Beds - 2010 ...................................................................2-2 1018976 - Touch and Step Voltage Measurements on Field Installed Ground Grid and Concrete Pads - 2009 ........................................................................................................2-2 1020400 - Field Guide: Smart Ground Meter - 2009...........................................................2-2 1015966 - Condition Assessment of Substation Ground Grids - 2008 ................................2-2 1013910 - Condition Assessment of Substation Ground Grids: Phase 1—Proof of Concept - 2008...................................................................................................................2-3 1013793 - Substation Ground Grid Impedance Measurement - 2007 .................................2-4 1013909 - Effects of Steel Reinforced Concrete on Grounding System Performance - 2007............................................................................................................2-5 1012386 - Improved Smart Ground Multimeter - 2006........................................................2-5 1010611 - Smart Ground Multimeter-Implementation of Enhancements - 2005 ..................2-5 1008683 - Enhancements, Validation, Testing, and Training: Smart Ground Multimeter 2004...................................................................................................................................2-5 TR-109272 - Study of Ground Currents in Proximity of Substations - 1997 ........................2-6 EL-5258 - Fusing Research on Personnel Grounding Cables, 1997...................................2-6 TR-101792 - Scoping Study: Substation Design Workstation, 1993 ...................................2-6 TR-100863 - Seasonal Variations of Grounding Parameters by Field Tests, 1992 .............2-6 TR-100622 V1-V5 - Substation Grounding Programs: Volumes 1-5, 1992 .........................2-7 EL-3983 - Soil Resistivity Tests Using Modeling Techniques, 1985....................................2-7 EL-2682-CCMV2 - Analysis Techniques for Power Substation Grounding Systems Volume 2: User's Manual, 1983..........................................................................................2-7 EL-2128 - Soil Thermal Resistivity and Thermal Stability Measuring Instrument, Volumes 1-5, 1981 .............................................................................................................2-8
3 OTHER REPORTS OF
INTEREST.......................................................................................3-1 1021856 - Environmental and Corrosion Effects on Reinforced Concrete Foundations ......3-1 1021954 - HVDC Reference Book: Interim Report .............................................................3-1 1023499 - Field Guide: Tier I, Above-and Below-Grade Corrosion Assessment of Weathering Steel Transmission Structures.........................................................................3-2 1017705 - Alternate Ground Electrode Materials - 2009 .....................................................3-2 1018203 - EGGS 2.1 - EPRI Grounding Guide Software, Version 2.1 - 2008 .....................3-2 1018198 - Guide for Transmission Line Grounding: A Roadmap for Design Testing and Remediation: Part II - Practical Guidelines - 2008 ..............................................................3-2
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1016933 - Grounding Electrode Corrosion: Overhead Transmission Line Grounding – 2008 ..............................................................................................................3-3 1013900 - Guide for Transmission Line Grounding - 2007 .................................................3-3 1001908 - Tower Grounding and Soil Ionization Report – 2002 .........................................3-3 1006866 - High Current Impulse Testing of Full-Scale Ground Electrodes - 2002 ..............3-3
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1 INTRODUCTION This document is a compilation of summaries of EPRI reports in the area of substation grounding, fault current management and ground grid evaluation, maintenance and refurbishment. It contains the report title, its PID, its year of publication, and brief descriptions of the contents.
Purpose and Scope of this Report The purpose of this report is to provide summaries of the various research studies that have been performed by the EPRI substation grounding project between 1980s and the end of 2011. The summaries of reports are based on Abstracts and/or Product Descriptions available in the EPRI page. In addition to providing some high-level findings and recommendations, the summaries should help the reader locate information on a particular topic or theme within the body of EPRI products that has been generated. This report also includes brief descriptions of EPRI reports published by ot her EPRI projects that may be of interest to the substation grounding project funders.
Organization of this Report Section 2 provides a brief abstract or summary of each of the reports in reverse-chronological sequence (from most recent back to early 1980s) in which they were completed. Section 3 presents brief summaries of recent publications by oth er EPRI projects that may be of interest to the Funders of the substation grounding project.
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2 SUBSTATION GROUNDING REPORTS 1024555 - Field Guide: Smart Ground Multimeter - 2011 December 2011, Final Report This Smart Ground Multimeter (SGM) field guide is intended to serve as a handy reference for technicians while they are in the field tasked with performing a ground grid audit. It is not meant as a substitute for the SGM Operating Manual but rather as a supplement that includes the basic “how-to” and practical considerations. The SGM underwent three major redesigns since its original development in the early 1980s and has evolved into a sophisticated and powerful testing device. The true value of the SGM is its capability of performing a ground audit of an electric power installation while the installation remains fully energized. A ground audit can identify problems with the grounding system and yields a validated model of an electrical installation. The validated model can then be utilized to determine whether the grounding system meets safety standards, and if it does not to define and assess remedial measures for bringing the design into compliance with standards. In practical field measurements, however, many unexpected measurement problems can occur, including errors introduced by unknown underground metallic objects, interference from other energized installations, and unintentional connection errors. The objectives of this guide are to help sensitize the user to a large range of practical problems, to provide guidance in identifying them, and to discuss methods for correcting or working around unavoidable problematic situations. The methodologies described in this field guide should be considered by engineers engaged in the design of substations and other electrical installations. The field guide also targets test engineers who are involved in testing of electrical installations. The SGM is already used by the electric power industry, the petroleum indu stry, the chemical industry, and other industries that have electrical installations with grounding s ystems.
1021921 - Substation Grounding Grids: Corrosion of Connections - 2011 Dec. 2011, Technical Update This report is an account of research performed by the Electric Power Research Institute (EPRI) in 2011 on the subject of degradation of buried grounding grids in electric power substations. Substation ground grids are usually made of copper conductors, which are placed below grade and are joined together and to the above-grade structures with various t ypes of connectors. While above-grade connections are visible and may be inspected, below-grade connections are not visible or readily accessible for inspection or testing. Several surve ys, conducted by EPRI and other organizations, show that some utilities experience degradation o f the substation ground grid and/or connections between grid elements and /or connections to substation structures. In response to this recognized problem, EPRI launched a project to study corrosion of substation 2-1
ground grids and connections. This report summarizes the results of utility surveys aimed at assessing the extent of the grid/connector/connections degradation probl em, and proposes a multi-year research plan for a systematic study of corrosion mechanisms, co nditions that induce or facilitate corrosion, and corrosion rates. The proposed research will include locating substations with potential or known maintenance issues and quantifying the factors governing the ki netics of the corrosion severity. This will be completed through a desk and paper study to identify any knowledge gaps. EPRI plans to follow this phase of research with a series of field surveys and laboratory exposure tests to characterize the corrosion morphology and initiation mechanisms. This will establish a roadmap for assessing inspection technologies and providing guidance in the selection of mitigation techniques for grounding system corrosion. The expected outcome of this research includes estimates of corrosion likelihood and rates in various types of environments, and eventually, recommendations for corrosion mitigation strategies that could be applied to substation ground grids and connections.
1020031 - Touch and Step Voltage Measurements on Field Installed Ground Grid Overlaid with Gravel and Asphalt Beds - 2010 Dec. 2010, Technical Update Gravel and asphalt are commonly used as surfacing materials in and around substations. Both the electrical characteristics of the surfacing material and its moisture condition substantially affect the exposure (step, touch) voltage and the resulting current. This project evaluates the e ffects of various types of surfacing materials (three gravel types and asphalt) and conditions (dry and wet) on step and touch voltages in and around substations.
1018976 - Touch and Step Voltage Measurements on Field Installed Ground Grid and Concrete Pads - 2009 Dec. 2009, Technical Update Concrete is commonly used as building material in substations (within the substation fence) and around substations (outside the fence) for driveways, foundations, walkwa ys, oil containment, sidewalks, walls, and other structures. This project evaluates the effects of v arious types (reinforced, non-reinforced) and conditions (dry, wet) of concrete structures on step, touch, and transfer touch voltages in and around substations.
1020400 - Field Guide: Smart Ground Meter - 2009 Nov. 2009, Technical Report This Smart Ground Multimeter (SGM) field guide is intended to serve as a handy reference for technicians while they are in the field tasked with performing a ground grid audit. It is not meant as a substitute for the SGM Operating Manual but rather as a supplement that includes the basic "how-to" and practical considerations.
1015966 - Condition Assessment of Substation Ground Grids - 2008 Dec. 2008, Technical Report
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This report describes the second stage of a research project to develop a simple and inexpensive method and device to assess the integrity of substation grounding grids. The problem has b een studied before but a reliable and inexpensive method or device to make a reliable diagnosis of grid condition is still lacking. While the EPRI-developed Ground Grid Evaluator (commercially known as the Smart Ground Multimeter) can be used to provide valuable information, the equipment is expensive and requires extensive high-level training and experience to collect reliable data and interpret the results. The first phase of this project (EPRI report 1013910) determined that low frequency radiation could be used as a viable investigative technique for evaluating the integrity of ground grid structures in substations. This method was further developed and tested in this phase of the project.
1013910 - Condition Assessment of Substation Ground Grids: Phase 1—Proof of Concept - 2008 Mar. 2008, Technical Update This report describes the first stage of research to develop a simple and inexpensive method and device to assess the integrity of substation grounding grids. The problem has been studied before but there is not, to our knowledge, a reliable and inexpensive method or device to make a reliable diagnosis. While the EPRI-developed Ground Grid Evaluator (commercially knows as the Smart Ground Multimeter or SGM) can be used to provide valuable information, the equipment is considered to be expensive and requires extensive high-level training and experience to collect reliable data and interpret the results. Hence, the objective of this research is not to develop a device that reproduces all functions of the SGM, but to develop new reliable and inexpensive method(s) and instrumentation that can be easily d eployed in the field and operated by technician-level personnel. The report is divided into seven sections. Section 1 briefly describes the technical problem and situations that are likely to be encountered in substations. Section 2 describes an initial literature search that will be completed in the near term. There has been good work done on the subject, and we have found on the order of 100 relevant published papers and reports. Section 3 presents results of a brief survey of utilities to sample the industry's experience with vintage ground grids and methods of detecting defects. The survey consisted of seven questions with sub-questions and was sent to approximately 80 members of EPRI TF 37H "Fault Current Management and Substation Grounding" who are funders of the EPRI Project Set 37H by the same name. Seven responses received by the time of publication of this Technical Update report are summarized in this section. All responses are treated in a confidential manner and are "sanitized" to remove the identity of the responder and the responding utility. Some responders answered all questions, some did not. One responder provided additional documents; these documents are not included in this report. Section 4 describes some potential approaches that appear to be promising in detecting and locating defects in substation ground grids. A number of methods were considered, including those used for underground (for example, water, oil, and sewer pipes) or inaccessible (nuclear
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plants) pipe systems, and overhead transmission lines (for example, conductors, anchor rods, and foundations). The methods considered include the following: •
Current injection
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Acoustic guided waves
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Eddy current detection
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Resistance analog method for detecting defects in substation grounding
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Electro-mechanical acoustic transducer (EMAT)
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Electromagnetic technique
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Ground penetrating radar
Section 5 contains a number of examples of magnetic field profiles for grids with different current injection/collection scenarios and different faults or breaks in the grid. Th e analysis was done with a code developed at RPI specifically for this project, and with the commercial package INCA from Magsoft Corporation. The "proof of principle" is condu cted in three logical steps. First, assuming an ideal square symmetric grid (all elements have th e same resistance/impedance), current distributions are calculated for a square grid without defects and for a grid with selected defects. The dc current excitation is used, and grid inductance and capacitance are neglected. Although dc excitation is not considered the preferred approach since dc in a ground grid may cause problems with large substation equipment and with control instrumentations, these calculations provide valuable guidance regarding the expected range of changes to the current distribution and to the locations of greatest changes within the grid when defects are introduced. In the second step, the same grid is used to calculate magnetic field signatures at a height of 200 mm above the grid. This step in the process demonstrates magnetic field signatures of grids containing defects. In the third step, a rectangular grid is considered, ac current excitation is used, and grid impedance is included. This step provides guidance regarding sensitivity of the magnetic field to grid defects. Section 6 summarizes the findings of this research to date and outlines general plans for future work. Section 7 contains references cited in the report and additional relevant papers.
1013793 - Substation Ground Grid Impedance Measurement - 2007 Dec. 2007, Technical Report Because safety impacts all segments of the electric p ower industry, the integrity and conformance to standards of substation grounding systems is of paramount importance. This report summarizes field demonstrations of commercially available meters for performance evaluation of large grounding systems, including the EPRI Ground Grid Evaluator (commercially known as the “Smart Ground Multimeter” or SGM). This hands-on demonstration session provided an opportunity for participants to work with several instruments for assessing the condition of substation grounding systems. While a complete ground grid audit was not performed and only a limited number of measurements were taken, the time was well spent on discussions among participants on various theoretical topics and field-related issues while performing the measurements.
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1013909 - Effects of Steel Reinforced Concrete on Grounding System Performance - 2007 Dec. 2007, Technical Update The study showed that the presence of concrete blocks in the vicinity of a substation might generate increased touch and step voltages, especially in cases where concrete blocks are outside the substation fence but close to it and are not bonded to the substation grounding system. However, in cases where the concrete blocks are bonded to the substation grounding system, the effect was beneficial in most cases considered in this parametric study. In any case, only a small amount of fault current usually goes through th e steel rebar. The performed parametric study was limited in scope and therefore does not capture all possibilities that may occur. For ex ample, the study has not addressed the issue of lightning cu rrents and what percentage of lightning current may flow in steel rebar bonded to the grounding system.
1012386 - Improved Smart Ground Multimeter - 2006 Dec. 2006, Technical Report The SGM has evolved into a sophisticated and powerful testing device. The true value of the SGM is its capability to perform a ground audit of electric power installations while the installation remains fully energized. The ground audit can identify problems with the grounding system and yields a validated model of an electrical installation. The validated model can be then used to determine whether the grounding s ystem meets safety standards, and if it does not to define and assess remedial measures to bring the design into compliance with standards. The test and analysis procedures can be applied to a new system during the commissioning period or to an old system while the system is operating. The device has been tested successfully on systems operating at 13 kV to 500 kV.
1010611 - Smart Ground Multimeter-Implementation of Enhancements - 2005 Sept. 2005, Technical Report A design has been made for an enhanced SGM and details were presented in report 1008683. This interim report describes the implementation of enhancements. All hardware enhancements have been implemented except for communications hardware since there was immediate need to alter the existing design. The software enhancements have been implemented partially. It is expected that all remaining enhancements will be implemented fully in 2006. This report records the second step towards successfully making the S MG more user-friendly and accurate and useful under more field conditions. The final report will deal with full findings that we expect will report an improved tool to help utilities assess their existing assets. The final report will also include examples of results obtained with the enhanced tool and will illustrate the benefits of the implemented enhancements.
1008683 - Enhancements, Validation, Testing, and Training: Smart Ground Multimeter - 2004 Dec. 2004, Technical Update
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A design has been made for an enhanced SGM and details are presented in this report. This is an interim report so the several evaluation phases will be covered in the final report.
TR-109272 - Study of Ground Currents in Proximity of Substations - 1997 Dec. 1997, Technical Report Using real utility systems, instrumentation was developed, and mapping techniques perfected and tested. Instrument accuracy was verified on the Rochester Gas and Electric Company's system using equipment left in place from the EP RI Power Quality Study completed several years ago by the Customer Systems Group. Results show that net currents are significantly larger in proximity to substations. Heavy flows of ground current were found in the vicinity of distribution substations. The significance of this discovery has yet to b e determined.
EL-5258 - Fusing Research on Personnel Grounding Cables, 1997 July 1997 Technical Report In general, computer program predictions compared well with the shortcircuit test results. • •
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Effects of conductor stranding and type of jacket proved negligible. Cable current ratings are strongly dependent on actual cable cross-section area as specified by ASTM standard B 263-58. Some of the commercial cables tested did not comply with these cross-section area requirements, resulting in lower fusing currents. Tests simulating breaker reclosure operations showed that no derating factor is necessary for typical reclosure times of 7-10 s. Especially for larger cable sizes, the rating of comp lete grounding assemblies is usually significantly below the rating of the cable itself-probably because of mechanical forces concentrated at the point the cable enters the terminating hardware.
TR-101792 - Scoping Study: Substation Design Workstation, 1993 April 1993, Technical Report The capabilities recommended for inclusion in the version 1.0 release of the workstation emphasize a database manager and graphical interface based on system one-line diagrams as well as station plot plan formats. The study also prop oses three categories of design functions: initial planning activities (site evaluation, station reliability, and related areas); physical plant design (grounding, bus design, lighting, and site preparation); and analytic functions (insulation coordination, shunt/series compensation design, loss-of-life evaluation, and other advanced concepts). Overall, it is important that this workstation correlate with related workstations involving substations, particularly in areas of insulation coordination, substation grounding, an d magnetic fields.
TR-100863 - Seasonal Variations of Grounding Parameters by Field Tests, 1992 Aug. 1992, Technical Report Although the overall ground impedance and resulting ground voltage rise did not change significantly from one season to another, the resistance to the ground grid itself reduced
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significantly during summer weather. This resulted in increased current through the ground grid and lower fault current through transmission line shield wires. Large increases in body currents for both step and touch were found during rainy weather. All types of gravel surfaces significantly reduced body currents in any weather, but washed gravel was more effective than crusher-run gravel (gravel with dust) in lowering accidental currents. An as phalt bed yielded lower body currents than concrete.
TR-100622 V1-V5 - Substation Grounding Programs: Volumes 1-5, 1992 May 1992, Technical Report Volume 1 of this report is a manual for SOMIP (soil measurement interpretation program), a computer program that calculates the best estimate of the parameters of a two-layer soil model from the usual soil resistivity measurements. Volume 2 is a manual for SM ECC (substation maximum earth current computation program), a computer program that determines the maximum ground potential rise of a substation ground mat. Volume 3 is a manual for SGSYS (substation grounding system analysis program), a computer program that determines maximum touch and step voltages that can be compared with the maximums recommended by safety standards. Volume 4 is a manual for TGRND (transient grounding system analysis program), a computer program that supplements the others by computing transient ground voltage, an important factor in high-voltage direct-current (HVDC) converter stations and in large substations where ac impedance may be significant. Volume 5 is an application manual that uses four example substation grounding systems to illustrate the applications of the SOMIP, SMECC, and SGSYS programs for designing safe substation grounding systems. Results of the design programs have been confirmed by measurements made in several substations.
EL-3983 - Soil Resistivity Tests Using Modeling Techniques, 1985 May 1985, Technical Report Good agreement occurred between the calculated and measured values of soil resistivity. These results show that either the Wenner method or the driven-rod method can provide the information needed to develop an accurate two-layer soil model. The conductivity and depth of the top layer are easiest to obtain by using the driven-rod method and plotting the apparent conductivity. Both methods are valid for finding the conductivity of the bottom layer. To control the step and touch potentials near the substation perimeter fence, ground rods driven at an angle are effective and may reduce substation grounding costs.
EL-2682-CCMV2 - Analysis Techniques for Power Substation Grounding Systems Volume 2: User's Manual, 1983 Aug. 1983, Technical Report This user's manual presents new computer-based techniques for an alyzing complex substation grounding systems in nonuniform soil. The substation grounding analysis (SGA) program comprises two subprograms: substation grounding systems (SGSYS) and substation maximum earth current computation (SMECC). Subprogram SGSYS outputs computed grid resistances to remote earth and step, touch, and transfer potentials at user-selected locations in and around the substation. An optional procedure that is more app roximate and less costly is included.
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Subprogram SMECC determines the types and locations of faults that can result in maximum earth current, the distribution of fault currents in the system, and grid-potential rise resulting from the faults. The procedure is sufficiently general to ac commodate most practical systems.
EL-2128 - Soil Thermal Resistivity and Thermal Stability Measuring Instrument, Volumes 1-5, 1981 Dec. 1981, Technical Report This report describes work to fully characterize soil thermal parameters and their effect on underground cable design. This effort included the development of improved apparatus and methods for measuring soil thermal properties and methods for incorporating historical weather data into thermal design. Volume 1 discusses the determination of soil thermal stability and other soil thermal properties. Volume 2 is a detailed ope rating manual for the hardware developed for analyzing soils in situ, called the thermal property analyzer (TPA). Volume 3 contains additional information describing the problems with soil measurements and possible solutions useful to utilities. Volume 4 is a brief TPA operating manua l designed to stand alone. Volume 5 is an abridged Manual for Use of the Statistical Weather Analysis Program.
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3 OTHER REPORTS OF INTEREST 1021856 - Environmental and Corrosion Effects on Reinforced Concrete Foundations December 2011, Technical Update The large number of transmission structures with concrete foundations that the electric industry maintains makes it important to develop efficient wa ys to monitor their condition and remediate damage, especially since the largest population o f concrete foundations is 20-40 years old; and almost 40% of foundations are more than 40 years old. This report discusses the environmental and corrosion effects that affect steel-reinforced concrete foundations, includ ing problems caused by poor construction, freezing and thawing, erosion, chemical attack, and oxide formation on the metal-concrete interface. The report describes field and laboratory inspection technologies available to evaluate the condition of existing structures and presents a four tiered inspection process that utilities can use to organize and implement their monitoring activities. Methods for remediating or preventing damage are described, including coating systems, electrochemical methods, and the use of various additives. The report lists areas where further research into concrete inspection, assessment, and remediation are needed.
1021954 - HVDC Reference Book: Interim Report December 2011, Technical Update The EPRI High-Voltage Direct Current (HVDC) Transmission Reference Book is a state-of-theart guidebook that provides transmission companies with a compreh ensive, single source of technical information and guidance for designing, building, operating, and extending the life of HVDC transmission systems. The book joins the landmark series of EPR I power delivery reference books. These comprehensive guidebooks—each printed with a distinctive colored cover—document and distill the knowledge and experience of the world's leading power delivery experts. In this tradition, the EPRI HVDC Transmission Reference Book will be printed with a dark green cover and be referred to as the "Olive Book." The Olive Book will have 24 chapters, covering all aspects of the theory and practice of HVDC transmission, including planning, system studies, AC-DC interactions, design of converter equipment, overhead lines and cables, project implementation and operation and maintenance. This edition of the Olive Book compiles 20 chapters, based on EPRI technical updates published during the last five years. Subjects covered in clude: an analysis of HVDC transmission, analysis of converter operation, configurations of HVDC transmission systems, converter station equipment, DC transmission with voltage source converters, DC transmission with series capacitors compensated converters, overhead lines with HVDC transmission, HVDC cables, simulation of HVDC systems, commissioning of HVDC systems, HVDC project implementation, and operation and maintenance of HVDC systems.
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1023499 - Field Guide: Tier I, Above-and Below-Grade Corrosion Assessment of Weathering Steel Transmission Structures December 2011, Technical Update Although weathering steel forms a protective oxide la yer on its surface after atmospheric exposure and generally does not require the coatings that protect standard carbon steels, it is vulnerable to above and below grade corrosion in some circumstances. This inspection guide is designed to help field crews quickly screen circuits for corrosion issues that present potential risks. Weathering steel structures may be flagged for additional work b y understanding oxide types, potential damage locations, and conditions that promote corrosion. The guide concisel y presents a four-step inspection process comprising right-of-way and general site surveying, atmospheric structural inspection, characterization of weathering steel coatings, and inspection of below grade structures. Once problems are identified, corrective actions can be undertaken including coating repairs, structural modifications, member replacement, or the application of cathodic protection.
1017705 - Alternate Ground Electrode Materials - 2009 December 2009, Technical Update Theft, material cost, and structural corrosion caused by a galvanic couple are concerns for utilities maintaining a grounding system within their service area.
1018203 - EGGS 2.1 - EPRI Grounding Guide Software, Version 2.1 - 2008 December 2008, Assembled Package The EPRI Grounding Guide Software (EGGS), Version 2.1, is calculation/modeling software for transmission line grounding. EGGS Version 2.1, is a set of applets to assist technical staff in the design and implementation of effective grounding of transmission lines and is intended for users who ne ed simple methods to evaluate new or existing transmission line grounding electrode designs. When ordering EGGS 2.1, included will be product 1018973, EPRI's Overhead Transmission Line Lightning and Grounding Reference Book 2009. This guide may also be downloaded separately.
1018198 - Guide for Transmission Line Grounding: A Roadmap for Design Testing and Remediation: Part II - Practical Guidelines - 2008 December 2008, Technical Report Electric utilities have a duty to provide reliable an d safe transmission line facilities. An important part of this is the provision of adequate grounding. For transmission lines, this imperative is usually met with an investment in overhead ground wires and grounding electrodes. The overhead ground wires intercept lightning strokes, thereb y shielding the transmission line, and provide additional ground paths for ac fault current to other transmission line structures. Ground electrodes at each structure improve reliability by providing a low-impedance path to discharge lightning strokes into the earth, thereby avoiding i nsulator flashovers and subsequent line outages. When necessary, grounding designs can be made to improve safety at transmission structures by controlling step and touch potentials resulting from stead y-state induction or fault
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currents. However, the adequacy of the grounding can vary significantly because of climate and location (that is, soil conditions). Consequently, grounding electrode designs may require structure-by-structure testing and validation.
1016933 - Grounding Electrode Corrosion: Overhead Transmission Line Grounding – 2008 August 2008, Technical Update Many utilities generally specify maximum grounding system resistance thresholds for system reliability and power quality reasons. At some point in time, grounding electrodes become ineffective because corrosion reduces the surface area or completely eliminates the connection to the structure. This corrosion can appear to be a random event and is often diagnosed only after a circuit experiences a ground fault or a lightning strike.
1013900 - Guide for Transmission Line Grounding - 2007 Dec. 2007, Technical Report Electrical utilities have a duty to provide effective grounding for managing steady-state and fault currents, whether near a large generating station or at a remote distribution pole ground. For transmission lines, this imperative is usually met with investment in overhead ground wires and grounding electrodes. Effective grounding at each tower improves reliability—by providing low path impedance to lightning strokes—and contributes to safety. However, the fundamental physical parameters in ground electrode engineering vary with climate and location, so tower-bytower testing and validation are needed. Existing standards for successful testing are better suited to substations or concentrated electrodes than to transmission towers, which can have several large, effective foundation grounding electrodes in parallel. This leads to a wide discrepancy in treatment and testing options from one utility to another.
1001908 - Tower Grounding and Soil Ionization Report – 2002 February 2002, Technical Report Deregulation of the power industry has increased t he need for greater reliability of the transmission system. Unplanned outages can have significant financial implications, and lightning activity is often cited as one of th e main reasons. To address this issue, EPR I is conducting research to increase understanding o f the lightning performance of transmission lines. This report details the results of one such study.
1006866 - High Current Impulse Testing of Full-Scale Ground Electrodes - 2002 April 2002, Technical Update The historical challenge of providing reliable electrical service is growing in importance. With electronic equipment in almost all facets of life, ev en momentary outages and power quality problems can adversely affect customers at home and work. Lightning causes many such momentary customer outages, and EPRI's TFlash program can help utility engineers evaluate the lightning performance of power systems.
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