<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><title>Comment Summary</title><link media="all" href="css/Export.css" type="text/css" rel="stylesheet" charset="utf-8" /><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><meta http-equiv="Content-Language" content="en" /></head><body style="margin-left: 15px; margin-right: 15px; margin-top: 15px;"><br /><div style="margin-top: 15px;"><table class="rsltsmry" border="0" cellpadding="0" cellspacing="1"><thead><tr><th class="hdr" colspan="8">Please tell us what can be added to the Std 80 that would complement your efforts.</th></tr><tr><th class="hdr dflt">#</th><th class="hdr dflt">Response&nbsp;Date</th><th class="hdr dflt" style="width: 80%;">Response Text</th></tr></thead><tbody id="xtrows"><tr><td>1</td><td style="white-space: nowrap;">Jun 8, 2009 10:29 PM</td><td>Increased focus on copper clad materials due to theft.</td></tr><tr><td>2</td><td style="white-space: nowrap;">Jun 9, 2009 5:32 AM</td><td>Man made ground well/lectrode for sandy soil</td></tr><tr><td>3</td><td style="white-space: nowrap;">Jun 9, 2009 12:51 PM</td><td>Add the following: 1. Complete example of generation grounding 2. Complete example of substation grounding 3. Complete example of distribution grounding 4. Complete example of industrial grounding</td></tr><tr><td>4</td><td style="white-space: nowrap;">Jun 9, 2009 12:55 PM</td><td>Step by Step design process recommendations. A "practical" methodology frequently followed at our utility is offered for your consideration: November 2001 Substation Ground Grid Design Procedure Background Information These substation ground grid design guidelines are based mostly upon the recently updated IEEE 80-2000 Standard entitled,  IEEE Guide for Safety in AC Substation Grounding. Extensive review of this Standard should be the first step in the design or modification of an electric substation ground grid. Particular attention should be given to at least the following portions of the IEEE 80-2000 Standard: Section 9.4 - Basic Aspects of Grid Design, Section 9.5 - Design in Difficult Conditions, Section 16.1 - Design Criteria, Section 16.2 - Critical Parameters, Section 16.3 and Table 12 - Index of Design Parameters, Section 16.4 - Design Procedure, Section 16.5 - Calculation of Maximum Step and Mesh Voltages, Figure 33 - Design procedure block diagram, and Section 16.6 - Refinement of Preliminary Design. The Commonwealth Associates Excel spreadsheet, located on the J:\Review/IEEE drive, provides a good template for the substation ground grid design process and should be used for this exercise. Further technical information regarding grounding conductors can be referenced in  Technical Data  A Reference for The Electrical Power Industry by Anderson Electrical Connectors. Confirm the following: ground conductor size, burial depth, length of grid conductor, grid spacing, crushed rock requirement, resistance to remote earth, and voltage rise of grid to remote earth. To a lessor degree, other references that might be consulted include the CU course notebook entitled,  Integrated Grounding System Design and Testing and the background reference book  Power System Grounding and Transients, both authored by Dr. A. P. Sakis Meliopoulos Soil resistivity can sometimes be a difficult number to exactly define. A contractor can be engaged to perform soil resistivity testing. Anderson Engineering (866-2741), and Palmerton and Parrish (831-3056), are two contractors currently under blanket CU contracts for these services. Typical values used at other CU substations may be a reasonable starting point too. Substation site specific factors can sometimes point the design in unusual directions. If a site has extensive rock or a high soil resistivity (above 1,000 ohm-meters), then other design options might need to be considered, like a grounding well or the use of ground enhancement material. If a substation site is physically small, like 100 x 100 , it may not be possible, even with close ground grid spacing, to achieve the desirable amount of copper in the ground. Some of the suggestions and preferences noted in the step-by-step guidelines are reflective of years of design and operational experience with substations. Once the overall design parameters are addressed, the practical design is to be based upon IEEE 80-2000. The method in IEEE 80 is an iterative  trial and error method but an acceptable solution can usually be achieved with just a couple of iterations. It should be noted that this design approach leads to a somewhat conservative design (more copper in the ground than may be necessary). The reasonable trade-off seems to be possibly spend a little more for copper in the ground (and purposely accept the improved ground grid design safety factor), rather than spending more money for expensive design software and test equipment (that soon will be outdated anyway). Procedure 1. Review the IEEE 80-2000 Standard entitled,  IEEE Guide for Safety in AC Substation Grounding. 2. Define the following design parameters: " Substation soil resistivity. Hire one of the current CU blanket contractors, Anderson Engineering (866-2741) or Palmerton and Parrish (831-3056), to perform soil resistivity testing if recent, site specific, soil resistivity information does not exist. " Substation area and geometry " Available fault current at substation  to be obtained from Planning Engineer " Expected duration of fault 3. Confirm the use of certain design parameters and preferences including: " Presumption of the use of buried 4/0 bare copper ground conductor at 18 depth " Presumption of the use of 5/8 x 10 copperclad ground rods " Presumption of the use of exothermic welds for all underground conductor connections " Presumption of the use of a 6 layer of coarse crushed rock surfacing (washed, with no fines) over the entire substation, and 3 outside of the substation fence. " Typical spacing for the underground copper conductors should be on an approximate 20 x 20 grid pattern. " Ground rods should be installed periodically but particularly near major pieces of substation equipment like transformers, switchgear, and breakers. " A safety rule-of-thumb is to install a 4/0 ground conductor about 3 outside of the substation perimeter fence and do a careful ground design at all gates and fence corners. " Another safety rule-of-thumb is to ground the fence posts, fence fabric, and strands of top barbed wire at every other post  so typically about every 20 . A rigorous approach to galvanic corrosion indicates that tinned 2/0 copper conductor and tinned connectors be used for galvanized chain link fence grounding 4. Prepare an AutoCad drawing with the proposed substation ground grid drawn to scale. Reference a previously designed, modern, CU substation, like Summit substation, for an example substation ground grid layout. 5. The ground grid design shall then used to develop a detailed ground grid layout drawing and bill-of-material list complete with item numbers, descriptions, manufacturer and catalog number. Reference the following Standards in the City Utilities Substation Standards Manual: A-GRD-1, Fence and Switch Platform, Grounding Details, A-GRD-2, Grounding Legend and Notes, and A-GRD-3, Grounding Plan and Sections, Bill of Material List. An example from Summit Substation may also be referenced in the master files. 6. Using the Excel spreadsheet software tool from Commonwealth Associates, Exhibit 1, located on the J:\Review/IEEE drive, confirm the proposed substation ground grid design. Several  trial and error iterations, with differing substation ground grid geometry, may be needed to achieve an acceptable solution. See example printout attached. 7. The completed documents should be placed in the corresponding substation correspondence file for future reference. The AutoCad substation ground grid drawing file should reside in the J: directory under the proper substation name. End of Procedure Attachment: Exhibit 1, Ground Grid Calculations</td></tr><tr><td>5</td><td style="white-space: nowrap;">Jun 9, 2009 3:22 PM</td><td>The main disadvantage of IEEE 80 is, calculation performs for entire site but using of software gives us this opportunity to localize our design and we can save $$$$ dollars in this way. Formula in Std 80 also is based on 2 layer soil that is not adequate for big sites. I believe that we need major review on whole standard to be able to cover recent and future very high fault current values and also optimize our design</td></tr><tr><td>6</td><td style="white-space: nowrap;">Jun 9, 2009 5:57 PM</td><td>More information on methodology for stone testing. More information on use of deep wells to reduce grid resistance. The guys who worked on the latest revision did an outstanding job !</td></tr><tr><td>7</td><td style="white-space: nowrap;">Jun 10, 2009 1:25 PM</td><td>We're OK with the standard as written.</td></tr><tr><td>8</td><td style="white-space: nowrap;">Jun 10, 2009 2:33 PM</td><td>More practical case studies</td></tr><tr><td>9</td><td style="white-space: nowrap;">Jun 16, 2009 12:20 AM</td><td>Unsure</td></tr><tr><td>10</td><td style="white-space: nowrap;">Jun 17, 2009 1:57 PM</td><td>Perhaps better Split factor Curves or recommendation for other analysis which takes into account circulating currents for auto-transformers; currently am using CDEGS FCDIST to determine Split Factor but is very time consuming and requires information from utilities regarding 3I0 fault current analysis, line geometry, phase and neutral/shield wire data, line distances, and typical structure separation. Also need a specified test procedure for determining resistivity of wetted crushed rock; IEEE Transaction Paper in Vol. 7 No. 1, Jan. 1992 regarding "Measurement of Substation Rock Resistivity" presents a possible method but ASTM G 187, ASTM G 57, and AASHTO T 288-91 (2004) do not provide specific testing procedures for determining wetted crushed rock resistivity with egard to actual installed conditions; do not want to test the crushed rock after it has been pulverized for labratory testing methods.</td></tr><tr><td>11</td><td style="white-space: nowrap;">Jun 17, 2009 3:56 PM</td><td>There should have one section introduce the routine test approaches of the substation grounding.</td></tr><tr><td>12</td><td style="white-space: nowrap;">Jun 18, 2009 12:26 PM</td><td>shorten it or provide a supplement that is more "cook book" approach with more difinitive guidance</td></tr><tr><td>13</td><td style="white-space: nowrap;">Jun 19, 2009 1:41 PM</td><td>More discussion on probabilistic methods for earthing design rather than determinisitic. Clarification on why IEC curves differ so much from IEEE curves and hence drive some standardization across the industry. More clarification on re-enforced concrete mesh bonding - i.e. the benfits and drawbacks. Lots of other things that i can't think of now!</td></tr><tr><td>14</td><td style="white-space: nowrap;">Jun 23, 2009 9:30 AM</td><td>adding examples explanding on Transfer voltage Elaborating in mitigation methods Specifically metioned primary protection time as a recommended fault clearing time Include the risk based earthing design</td></tr><tr><td>15</td><td style="white-space: nowrap;">Jun 29, 2009 6:55 PM</td><td>The application and selection of commercial programs for station ground grid design.</td></tr><tr><td>16</td><td style="white-space: nowrap;">Jun 30, 2009 1:03 AM</td><td>allowable step voltage calculation fomular is to be modified to allow the body resisitance reduction of person standing on the ground with two feet</td></tr><tr><td>17</td><td style="white-space: nowrap;">Jul 2, 2009 9:06 PM</td><td>Cannot think of anything.</td></tr><tr><td>18</td><td style="white-space: nowrap;">Jul 10, 2009 2:14 PM</td><td>Clause for conductor sizing factors, please clarify temperatures for selection of joints (exothermic, brazing compression etc). Please clarify the sections on how to choose Shock duration time and fault duration time. Add an Index, like the version of IEEE 80-1986.</td></tr><tr><td>19</td><td style="white-space: nowrap;">Jul 13, 2009 6:38 PM</td><td>Additional discussion of grounding rebar in concrete.</td></tr><tr><td>20</td><td style="white-space: nowrap;">Aug 10, 2009 8:01 PM</td><td>Info about typical resistivities for more materials that could be used in calculations. It's often hard to find values for different types of rock. A treatment of concrete and how to treat it as a surface layer.</td></tr></tbody></table></div></body></html>