UNITED STATES DEPARTMENT OF AGRICULTURE RURAL UTILITIES SERVICE
SUMMARY OF ITEMS OF ENGINEERING INTEREST AUGUST 2000 THIS PAGE IS INTENTIONALLY BLANK Items of Engineering Interest August 2000 TABLE OF CONTENTS
ITEM ENGINEERING and OPERATIONS PAGE Revisiting Stray Voltage.....................................................................................1 New Trend in Distribution Generation for the 21st Century.................................2 DOE and Rural Electricity Providers: A Lesson in Economic Benefits...............3 Distributed Generation Standards .......................................................................6 Safety Signs .......................................................................................................8 New Guidelines for RUS Approval to Use Steel Distribution Poles ....................9 Update of Bulletin 50-3 (D-804) ­ 12.47/7.2 kV Construction Standards .........15 Bulletin 1728F-803, Specifications and Drawings for 24.9/14.4 kV Corrections.............................................................................................16 MATERIAL and PROCUREMENT
RUS Acceptance of Fiberglass Crossarms ........................................................18 RUS Bulletin 1724E-216, Guide Specification for Standard Class Spun Prestressed Concrete Poles.....................................................................18 ICEA Issues New Standards for Power Cables.................................................26 Coop Supply Professionals? ............................................................................29 Close the Loop On Recycling: Buy Recycled ..................................................30 ENVIRONMENTAL
Environmental Report Preparation....................................................................31 Environmental Review of Minor Projects .........................................................34 Summary: The State of the Art in Raptor Protection - A Historical Perspective.............................................................................................36 Migratory Bird Treaty Act Enforcement ...........................................................37 Raptor Electrocution/Collision Workshops.......................................................38 Raptors at Risk Video ......................................................................................41 ADMINISTRATIVE and OTHER
The RUS Website ............................................................................................42 New Data Collection System............................................................................44 RUS Electric Engineering Seminar and NRECA's TechAdvantage ..................45 RUS Technical Publications .............................................................................46 Transmission and Distribution Engineering Committee.....................................51 Exhibit 1 ­ Maximum Line Angles ­ Table VII .....................................................53 Exhibit 2 - Selected Metric Conversion Factors .....................................................54 Appendix A ­ ESD Directory................................................................................55 Appendix B ­ NRECA T&D Committee ...............................................................57 i Items of Engineering Interest August 2000 ABBREVIATIONS
ACSR ARS ANSI APS ASCE ASTM BGEPA BIL CFR CNN CWP DCS DG DOE ER ESA ESD FERC G&T HSS ICBO ICEA IEEE IWO kip kV M&E MBTA MLEA MOU NAPM-REU NEHRP NEMA NESC NRECA OLF OHGW PG&E PSN PV RBS REA RTB RUS RUS List of Materials T&D UBC USDA USDI USFWS USGS Western Aluminum Conductor Steel Reinforced Agriculture Research Service American National Standards Institute Arizona Public Service Company American Society of Civil Engineers American Society for Testing and Materials Bald and Golden Eagle Protection Act Basic Impulse Insulation Level Code of Federal Regulations Cable News Network Construction Work Plan Data Collection System Distributed Generation Department of Energy Environmental Report Endangered Species Act Electric Staff Division Federal Energy Regulatory Commission Generation and Transmission High Strength Steel International Conference of Building Officials Insulated Cable Engineers Association Institute of Electrical and Electronics Engineers Inventory of Work Orders 1000 Pounds Kilovolt Mechanical and Electrical Migratory Bird Treaty Act Moon Lake Electrical Association Memorandum of Understanding National Association of Purchasing Management-Rural Electric Utilities National Earthquake Hazard Reduction Program National Electrical Manufacturers Association National Electrical Safety Code National Rural Electric Cooperative Association Overload Factor Overhead Groundwire Pacific Gas and Electric Photovoltaic Services Network Photovoltaic Rated Breaking Strength Rural Electrification Administration Rural Telephone Bank Rural Utilities Service RUS Informational Publication 202-1, "List of Materials Acceptable for Use on Systems of RUS Electrification Borrowers" Transmission & Distribution Uniform Building Code U. S. Department of Agriculture U. S. Department of the Interior U. S. Fish and Wildlife Service U. S. Geological Survey Western Area Power Administration ii Items of Engineering Interest August 2000 ENGINEERING and OPERATIONS
Revisiting Stray Voltage
In February and March 2000, the U. S. Department of Agriculture (USDA) received several letters and telephone calls from a number of dairy farmers in Wisconsin and Minnesota. The farmers advised that their dairy herds are experiencing distress that is affecting the health of cows and their milk production. These farmers attribute the problem to stray voltage that they believe is originating from the power lines serving their farms. The farmers indicated there is an alarming loss of communications and trust between the farmers, the electric utilities that serve their farms, and others in the state and local governments. These complaints brought to mind RUS past history with stray voltage concerns. In a September 24, 1981, letter to all electric borrowers, the Rural Electrification Administration (REA) advised of a large increase in complaints related to stray voltage on farms. This REA letter briefly discussed some of the causes and remedies of stray voltage, and recommended that REA borrowers share the information with the farmers that they serve. A follow-up letter of April 27, 1983, to all electric borrowers contained additional reference sources for information on the subject and included some suggested information on stray voltage which could be provided in "bill stuffers" to customers. At that time, borrowers and farmers were working together to identify and alleviate stray voltage problems at farms. In December of 1991, the Department of Agriculture's Agriculture Research Service (ARS) published a most complete 140 page reference and source of help on the subject of stray voltage at farms...Agriculture Handbook 696, "Effects of Electrical Voltage/Current on Farm Animals." The Department published this handbook because of concerns about the way stray voltage research results were being misinterpreted and misconstrued, and because of the general lack of understanding of the causes and effects of stray voltage on farms. This handbook has been used widely and is generally considered to be a prime reference on the subject. Subject matter includes such information as: 1. The history of stray voltage/current on farms, 2. The physical and electrical sources of this phenomena, 3. The physiological and behavior bases for losses in production, 4. Method for identifying and detecting problems 5. Methods for mitigating stray voltage/current problems, and 6. Areas where further research may be required. The primary emphasis was on cattle and dairy farms, but the theories and procedures discussed were relevant for all types of livestock and the associated housing facilities. Recommendations 1 Items of Engineering Interest August 2000 were made to address action levels and mitigation techniques. The fundamental conclusion of this handbook was that stray voltages/currents could be reduced to acceptable levels. The handbook can be purchased from the National Technical Information Service, Technology Administration, U. S. Department of Commerce, Springfield, VA 22161, phone (703) 605-6000. Please advise that you wish to purchase NTIS Order No. PB92-172873. The recent year 2000 problems described by dairy farmers appear to be multifaceted and involve: 1. Misunderstanding or lack of knowledge about electrical properties and phenomenon, 2. Misunderstanding or lack of knowledge about animal health, physiology and behavior, and, 3. Poor or lack of communications between all parties involved. In an effort to help resolve these problems, the Electric Staff Division (ESD) is currently soliciting involvement and assistance from other USDA agencies. One agency, the Agriculture Research Service, has experts in animal husbandry and behavior and knowledge of the reaction of animals to electrical voltages and currents. Another agency, Cooperative State Research, Education and Extension Service and its various Extension Service offices throughout the U. S., could provide help by visiting farmers and farmer organizations to educate farmers about the cause and cures of stray voltage problems. This education effort could help alleviate the misunderstandings and lack of knowledge about stray voltage and open the pathway to better communications with all involved parties. If you would like more information or have any questions, please call John Pavek, Chief, Distribution Branch, at (202) 720-5082. New Trend in Distribution Generation for the 21st Century
Perhaps you have read articles, seen reports, or may have attended power generation seminars on the new technology called "Fuel Cells" that promises to revolutionize the power distribution industry as we know it. In the not too distant future, some rural electric customers will have the opportunity to supply a portion of their own power needs using on-site generators. These highly efficient and reliable fuel cells will be available in five to ten years with a reasonable per kilowatt installation cost. This new technology promises almost flawless reliability and emission-free (the only by products are water, carbon dioxide, and heat...and the heat can be used for hot water or home heating as well). Fuel cells behave like batteries, but unlike batteries, they are endlessly charged. The fuel cells use fuel from a natural gas line or a propane cylinder; the fuel is cleaned, then converted into a hydrogen-rich product, gas, which is then fed to the fuel cell module. In the module, the supplied hydrogen and oxygen from the air are electrochemically combined to produce DC 2 Items of Engineering Interest August 2000 electric power. The DC power is fed to a power converter, where it is converted to AC power, which is then available to meet the business or residential power requirements. A growing number of electric customers nationwide believe that fuel cells are a model energy source for the 21st century. This customer belief should make rural electric distribution managers more aware and cause them to get involved in this new trend. The U. S. Department of Energy has also been involved, and has invested in this area and recently announced that the first 100 kW fuel cells experiment has completed a record of 8700 hours of generation supplying 110 kW of electricity to a local power grid. Additional tests and applications for the units up to 250 kW are underway. Tri-County EMC of Reynolds, Georgia, for example, is planning to market home generation system to its customers by the year 2001. The potential value of fuel cell technology is already recognized, and in the very near future, the cost of fuel cells should be comparable with other types of power production. The expected retail price per unit is about $8500 and should drop by half within a few years. The estimated unit cost will run between 12 and 16 cents per kilowatt-hour for average household usage. In addition to the positive benefits surrounding fuel cells, customers are expected to be willing to pay the initial installation cost for the benefit of having their own independent generator. If you would like more information or have any questions, please call Ted V. Pejman, Electrical Engineer, Transmission Branch, at (202) 720-0999. DOE and Rural Electricity Providers: A Lesson in Economic Benefits
A particularly grizzly winter on the Rocky Mountain Plains provided the impetus for a successful partnership between the U.S. Department of Energy's Sandia National Laboratories and several rural electric cooperatives ­ a partnership that demonstrated that rural electric utilities will be the first domestic electric utilities to have an economically viable use for photovoltaics. During the winter of 1988, K. C. Electric Association, Hugo, Colorado, lost more than 600 utility poles to ice and snow. The buildup on lines snapped poles like toothpicks ­ at a cost of about $10,000 for each mile of line that K. C. Electric had to rebuild. K. C. Electric, like many rural electric cooperatives, is responsible for operating and maintaining a distribution system serving many remote ranching and farming loads. Many of the downed lines served only a small load ­ often just one livestock water pump. To be sure, one small pump is a critical load when cattle need water. K. C. Electric owns miles and miles of distribution lines across the eastern Colorado plains. And they are not unique. Rural coop-owned loads are often characterized by their relatively small power requirements, remote locations, and high cost of service. Enter DOE's National Photovoltaics Program (via Sandia). Could a photovoltaic (PV) array power a water pump in isolated instances such as those served by K. C. Electric? Matching a proven technology to this specific application was the key. A partnership that included not only 3 Items of Engineering Interest August 2000 Sandia, but also the Western Area Power Administration and the Electric Power Research Institute, focused on examining and assessing the relative economic benefits of PV power versus conventional power for small water pumping systems. As part of the cooperative cost-shared agreement, which included the NEOS Corporation, a contract was let for $10,000 to purchase a water pumping system as a demonstration project at one of K. C. Electric's remote customer sites. The installation would give the rural utility a chance to see the technology at work and assess the costs - and cost savings - while familiarizing its personnel and customers with PV power. And DOE's National PV Program would benefit too. Quoting from a letter that Sandia engineer, John Stevens, who led DOE's role in the project, wrote to K. C. Electric: "...the U.S. DOE National Photovoltaic Program would gain substantially...from an electric utility documenting their costs, both installation and maintenance, of photovoltaic systems installed to meet customer loads." In short, the DOE Program wanted the coops to look very closely at the cost of PV versus the cost of line extensions. The project successfully demonstrated PV for rural co-ops and provided some excellent preliminary information. A direct outgrowth of this was a survey by NEOS of some 25 electric cooperatives in Colorado, Nebraska, and Wyoming to determine the potential market for this PV application. It wasn't long before more than 6,800 remote water pumping installations for cattle grazing were identified, all of which were possible candidates for being powered by PV. Taken together, they represented nearly 3.5 megawatts of electric service capacity for utilities, or over $20 million in equipment sales for PV suppliers. Yet another spin-off activity was NEOS' work with five host utilities in Wyoming to install and monitor water pumping systems across their service territory. Again, the project would serve the dual purpose of demonstrating performance and reliability of the pumping application and familiarizing rural utilities with PV power. DOE's participation in these efforts took the form of numerous technical consultations by Sandia engineers, and assistance with a document called PV Products List, through Photovoltaic Services Network (PSN), a non-profit organization formed by a coalition of some of these same rural electric services providers. PV Products List provided a single point of contact ­ PSN ­ for purchasing appropriately sized PV systems. The PV Products List still stands as a valuable service where a future investment makes sense. It is one of the most tangible ways that the rural electric cooperatives could be helped in their day-to-day activities in purchasing, installing, and maintaining remote PV water pumping systems. During this period of time ­ the late Eighties ­ the use of PV power by electric utilities was being talked about everywhere. One particular concept, developed by Pacific Gas and Electric (PG&E), for introducing PV into the utility industry, suggested that PV cost-effectiveness for particular utility niches would be the driving force behind its introduction. The concept clearly suggested how PV-powered application might diffuse into the utility market. Specifically, utility involvement with PV likely would begin with installations that allowed the utility to postpone expensive construction projects by supplying increasing load demand with PV. 4 Items of Engineering Interest August 2000 The program contracted with four electric utilities to study the economic benefit of PV systems for support of distribution feeders. This study was performed because of the PG&E Kerman Feeder study. The Kerman study produced the rather startling result that a PV system, when installed at a carefully selected location, could have benefits that would allow an installed cost of as high as $6.50 per watt. This was in contrast to the prevalent theory that PV must be installed for $2.00 per watt to be competitive in the utility environment. DOE's effort intended to investigate the range and reality of the PG&E values for other utilities. The results of the four contracts clearly indicated that the greatest benefit comes when PV can be installed at a location where it offsets load growth that is forcing the utility to spend money on capital-equipment upgrades, such as increasing line or substation capacity. In addition, the greatest benefit is realized when the load that is growing is relatively small, and the cost of the upgrade is relatively large. This situation is most often seen in the service area of rural co-ops, where the co-op typically has long lines serving small loads. In fact, the best result of the four utility studies was a situation with a co-op that had a 36-mile long 25 kV line serving a small town. Load growth in that town was forcing the utility to consider upgrading the line to 69 kV. The study showed that installation of a 50kW PV system would allow postponing the line upgrade for 5 years. The economic benefit to the utility of postponing the line upgrade would allow the expenditure of $10.50 per watt to build a 50 kW PV system. An important factor in the high benefit value for this co-op was that the specific problem on this line was voltage support, rather than capacity support. Thus, a relatively small amount of local generation could cure a problem that otherwise would require line reconstruction. This set of studies illustrated the important lesson that long, lightly loaded lines that are approaching a need for upgrading are the places where PV can first see economic break-even conditions. Since the nation's rural co-ops' very nature means they are rife with long, lightly loaded lines, then the rural co-ops are the utilities that are in a position to first take advantage of the modular, distributed, low maintenance aspects of grid-support PV systems. Photovoltaic Systems for Utility Companies (published in 1990 with DOE PV Program funding) encouraged electric cooperatives and utilities to consider PV for their remote customer loads. The installation by K. C. Electric was cited as a demonstration of what could be done in lieu of rebuilding downed lines. The PG&E concept did not offer (nor was it intended to offer) suggested methods for initiating this utility market penetration within any particular market niche. But by then, several utilities in the western United States had begun testing PV service programs. To transfer information from those utilities to others that might be interested, DOE collaboratively focused on: (1) identifying utilities that then offered PV as a service option for isolated utility loads, such as livestock water pumping; (2) gathering information on program implementation procedures and constraints; (3) assessing utility and customer attitudes toward PV-powered systems; (4) documenting the cost, performance, and reliability of any PV-powered systems installed by these utilities; and (5) compiling all "lessons learned" into a document describing PV as a utility service option for 5 Items of Engineering Interest August 2000 livestock water pumping. Photovoltaic Power as a Utility Service: Guidelines for Livestock Water Pumping (published in 1993 at Sandia) was the result. Presentations on this successful model were given at the 1992 Rural Electric Power Conference, at SOLTECH's 1990 meeting, and in 1993 at the IEEE Summer PES meeting. As a result of the successful partnership, two electric utility cooperatives in the western United States soon offered PV-powered electric service options for remote water pumping applications to their rural customers. Others would follow. The DOE/rural co-op project was important because livestock water pumping occurs frequently in the western and mid-western U.S. and the cost of serving this load using traditional utility methods can be excessive. The lessons learned from utility PV-powered water pumping services are applicable to other off-grid PV service applications as well. The bottom line experience of this early DOE partnership with rural electric service providers is the same as the bottom line for all utilities: Long lines with small loads represent extraordinary cost savings to rural electric cooperatives. They are, in fact, where PV first makes sense for utilities. If you would like further information or have any questions, please call Jim Rannels, Director, Office of Solar Energy Technologies of DOE at (202) 586-1720, E-mail JAMES.RANNELS@hq.doe.gov, or Georg Shultz, Chief, Energy Forecasting Branch, at (202) 720-1920. Distributed Generation Standards
Distributed Generation (DG) is defined as any generating resource other than central station generation placed close to the load being served, usually meaning customer site. DG may be connected to the supply side or demand side of the meter. DG technologies may range from gas turbines of 50 megawatts or more, to 25 kW micro-turbines, to photovoltaic systems of less than 1 kW. Other technologies such as wind turbines, internal combustion engines, small hydros, flywheels, fuel cells, and batteries also exist among these size ranges. DG technologies can provide energy, ancillary services, reliability and power quality to electric service providers, irrigation districts, municipal utility districts and end users. According to National Rural Electric Cooperative Association (NRECA) surveys, DG is taking hold in many parts of the country. For example, these surveys reported that "there are more than 125 MW of local generation sets at cooperative consumer sites in Florida. Ten of 31 G&Ts reported that either they or some of their customers are using local equipment for distributed generation applications..." Even modest adoption of DG technologies could have a significant impact on cooperatives. Therefore there is a clear need for good useful standards for interconnecting DG units with 6 Items of Engineering Interest August 2000 electric distribution systems. There are already some interconnection standards recently issued and some under development. The completed standards include: Institute of Electrical and Electronics Engineers (IEEE) Standard 929-2000, entitled "Recommended Practice for Utility Interface of Photovoltaic (PV) Systems." This document provides a straightforward, understandable interconnection standard for PV systems and utilities. This standard is expected to influence other interconnection standards for distributed generation as well. The California Public Utilities Commission has published a comprehensive document describing the minimum operating, metering, and interconnection requirements for any generating source or sources paralleled with any electric utility system within the State of California. This document is entitled, "RULE 21 - NONUTILITY-OWNED PARALLEL GENERATION". Rule 21 can be downloaded from the following Internet address: http://www.pge.com/customer_services/business/tariffs/#ER
(under Electric Rules Click on item No. 21 Nonutility-Owned Parallel Generation) IEEE Standard under development: IEEE SCC21 P1547 Working Group is currently working to produce a standard document for interconnection of all types of distributed generation resources with electric power systems by the end of this year. A published standard is planned in 2002. The draft entitled "IEEE P1547 Standard Draft 04 - Distributed Resources Interconnected with Electric Power Systems." The draft is available for viewing at: http://technet.nreca.org/distribgen.html
To help IEEE produce a consensus document for the interconnection of all types of distributed generation with investor owned urban and rural utility grids, it is essential for cooperative engineers to work in unison and to agree on practical, meaningful provisions. Therefore input from rural electric cooperatives is deemed essential to avoid development of overly complex standards and to focus on meaningful grid interconnection standards especially pertinent to rural areas. Rural Utilities Service (RUS) highly recommends that RUS borrowers get involved in the development of this standard. We encourage rural electric cooperative engineers and managers to review the referenced standards and use them as tools to become familiar with the issues involved. Knowledge from these readings should then be used to evaluate and provide comments to IEEE SCC21 P1547 Working Group. Provide comments to IEEE through Dr. Paul Dolloff, technology consultant at East Kentucky Power Cooperative to influence this rapidly evolving IEEE standard. Dr. Dolloff is the NRECA Transmission and Distribution Engineering Committee representative on the IEEE 7 Items of Engineering Interest August 2000 SCC21 P1547 standards working group. He may be reached by phone at 606-744-4812 and by e-mail at pauld@ekpc.com. If you would like more information or have any questions, please call Mike Eskandary, Electrical Engineer, Transmission Branch, at (202) 720-9098. Safety Signs
We have previously discussed and would like to reiterate the ANSI standards for environmental and facility safety signs. These standards are intended to promote uniform national practice, and include considerable changes from some past safety sign practices. As a result of these new safety sign standards and other needed changes, RUS has revised Bulletin 1728F-806, Specifications & Drawings for Underground Electric Distribution. We deleted the formerly used standards for safety signs and now refer to the following ANSI standards: ANSI Z535.1 Safety Color Code ANSI Z535.2 Environmental and Facility Safety Signs ANSI Z535.3 Criteria for Safety Symbols ANSI Z535.4 Product Safety Signs and Labels ANSI Z535.5 Accident Prevention Tags (for Temporary Hazards) These consensus generated and coordinated standards are intended to apply to every permanent or temporary safety sign or tag used on a utility system. These standards prescribe details for colors, shapes, and panel layout for the three panel types: (1) the signal word panel, (2) the message panel, and (3) the pictorial panel. For dead-front pad-mounted equipment, we recommend that the "Warning" sign be placed on the exterior and the "Danger" sign be placed inside the enclosure. In the past, most borrowers have used the "Danger" sign for substation fences with no additional safety signs inside the substations. We recommend that the "Warning" signs be placed on the surrounding fence and "Danger" signs be installed inside the substations on structures that support live parts. State regulatory agencies or insurance companies may also have recommendations on this topic that should be considered. If you would like more information or have any questions, please call Trung Hiu, Electrical Engineer, Distribution Branch, at (202) 720-1877. 8 Items of Engineering Interest August 2000 New Guidelines for RUS Approval to Use Steel Distribution Poles
In January, 2000, RUS again updated its guidelines of things that borrowers should consider when requesting RUS approval to use steel distribution poles. These new guidelines, now identified as "Version 5," are included below. These new guidelines provide borrowers much more information regarding the proper use and selection of steel distribution poles and associated pole-top assemblies. The new guidelines also provide more information on who and how to contact certain individuals at RUS to answer specific questions regarding steel poles. Now, RUS asks that a borrower address (in writing) only the nine issues listed on the last page of the guidelines (as applicable) when submitting a request to RUS. RUS Guidelines and Approval for the Use of Steel Distribution Poles Version 5 The Rural Utilities Service (RUS) will consider a borrower's written request to use steel distribution poles for site specific projects on a case-by-case trial basis to gain experience. Before granting approval, RUS needs sufficient information to assure that the application of steel poles will result in safe and reliable construction and meet RUS requirements. Borrowers requesting RUS approval to use steel distribution poles are asked to read the following guidelines and design information and to furnish RUS with the information requested in Part II. Part I: RUS Guidelines and Design Information for Using Steel Distribution Poles A: MATERIALS Except for various miscellaneous material items, RUS regulations require that borrowers use materials that RUS has fully, conditionally or technically accepted. A compilation of fully and conditionally accepted materials may be found in Informational Publication 202-1, "List of Materials Acceptable for Use on Systems of RUS Electrification Borrowers" (List of Materials). This List of Materials can be accessed through the internet at: http://www.usda.gov/rus/electric/listof.htm 9 Items of Engineering Interest August 2000 For information on technically accepted items and other questions regarding materials, please contact: Mr. Harvey Bowles, Chair Technical Standards Committee "A" (Electric) Rural Utilities Service, Stop 1569 1400 Independence Avenue SW Washington DC 20250-1569 Phone: (202) 720-0980 Fax: (202) 720-7491 Email: hbowles@rus.usda.gov Borrowers requesting RUS approval of materials not presently accepted, for use with steel poles or any other application, are asked to provide: a description of the material, catalog sheets, test results, and the name and address of the manufacturer. Such requests should be sent to the appropriate regional Engineering Branch Chief. (See Section G) B: LIGHTNING IMPULSE WITHSTAND STRENGTH and SURGE PROTECTION A lightning impulse withstand strength, often called Basic Impulse Insulation Level or BIL, of less than 300 kV on distribution pole top assemblies will usually facilitate flashovers of lightning strikes to or near distribution lines. A recloser operation, which will cause lights to flicker, is usually required to clear the resulting arc. RUS advocates that the withstand strength (dry flashover, phase-to-phase and phase-to-ground) be no less than 300 kV to minimize recloser operations and thus improve the quality of service. This level is especially important on deadends where voltage doubling can occur. A withstand strength of 300 kV (dry flashover) can be achieved on steel poles by using many of the standard RUS pole-top assemblies and installing a fiberglass-reinforced plastic pole-top pin (item "b (2)" in the List of Materials) on the phase conductor attached to the very top of the pole. A 300 kV lightning impulse withstand strength (dry flashover) can be attained on a steel pole deadend structure by installing a 24 inch (minimum length) insulated extension link (item "eu" in the List of Materials) between the primary deadend suspension insulators and the steel pole. Borrowers do not need additional RUS approval to use the above two material items or the resulting modified standard pole top assemblies. The designated maximum transverse load on fiberglass-reinforced plastic pole-top pins is 500 pounds. The maximum line angles for this loading limitation can be found in Table I of RUS Bulletin 1728F-803, "Specifications and Drawings for 24.9/14.4 kV Line Construction." RUS recommends the installation of surge arresters at 800 foot to 1,200 foot intervals and at deadends on all distribution lines which are exposed to frequent lightning strikes. This recommendation is especially applicable to distribution lines built with steel poles because of 10 Items of Engineering Interest August 2000 their generally lower lightning impulse withstand strengths. An adequate number of installed surge arresters minimizes the number of lightning flashovers and the resulting momentary outages and damaged insulators. C. GROUNDS, GROUNDING The National Electrical Safety Code (NESC) requires that all non current-carrying metallic members on a line support structure be effectively grounded. Thus, each steel pole needs to be effectively bonded to all primary and secondary neutrals, down guys, messengers, and all other metallic attachments to the pole. Other NESC grounding requirements may also apply. A steel pole may be used as a grounding conductor if the pole meets the sufficient conductivity and low impedance requirements of the NESC. Since a directly embedded steel pole is not recognized in the NESC as a grounding electrode, separate driven ground rods or grounding electrodes need to be used for all equipment, surge arresters and other required system grounds. The use of stainless steel or galvanized steel ground rods and non-copper ground wires in the soil near steel pole distribution lines will help to mitigate the corrosive effects of dissimilar metals buried in close proximity. D: COSTS AND ECONOMIC STUDIES RUS does not require borrowers to provide any economic studies or cost comparisons to justify the use of steel distribution poles in lieu of wood poles. However, borrowers are encouraged to compare the initial and long-term estimated installed cost of equivalent distribution structures or lines constructed with steel poles versus wood poles. Borrowers may, at their discretion, furnish the results of their cost estimates to RUS. Questions or comments regarding Sections B through D above are welcomed by and should be sent to: John Pavek, Chief Distribution Branch Electric Staff Division Rural Utilities Service, Stop 1569 1400 Independence Avenue SW Washington DC 20250-1569 Phone: (202) 720-5082 Fax: (202) 720-7491 Email: jpavek@rus.usda.gov E: RAPTOR PROTECTION USING STEEL POLES RUS advocates that distribution lines be designed and constructed in a way that will minimize the electrocution of raptors and other animals. Distribution construction with steel poles need 11 Items of Engineering Interest August 2000 extraordinary consideration because of the short distances between the bare energized phase conductors and the grounded steel pole. On single-phase lines, the installation of 24 inch long fiberglass-reinforced plastic pole-top pins ("item b (2)" in the List of Materials) will minimize the electrocution of small raptors. On threephase lines, some raptor protection can be achieved in an economical manner by installing fiberglass-reinforced pole-top pins and perch guards on the crossarms as shown on assembly VP3.3G in Bulletin 1728F-803. Good raptor protection can be achieved on both single-phase and three-phase structures by: · · Installing 24 inch long fiberglass-reinforced plastic pole-top pins; Using non-metallic crossarms and covering the pole, from the neutral up to and including the top of the pole, with an insulating coating that has a dielectric strength of at least 15,000 volts; and, Using 36 inch (minimum length) fiberglass-reinforced plastic guy strain insulators (item "w") and extension links (item "eu") for all connections to the pole above the neutral position. (See Bulletin 1728F-803, assemblies VA5.4 and E5.1G) · Any questions or comments regarding raptor protection can be directed to: Dennis Rankin Rural Utilities Service, Stop 1571 1400 Independence Avenue SW Washington DC 20250-1571 Phone: (202) 720-1953 Fax: (202) 720-1820 Email: drankin@rus.usda.gov F: SELECTION OF STEEL DISTRIBUTION POLES Generally, a wood pole cannot be replaced with a steel distribution pole of the same class because of NESC strength requirements. After the selection of the NESC grade of construction, certain "design load" calculations are required to determine the minimum class of a steel distribution pole that can be used in lieu of a wood pole for standard RUS pole-top assemblies. The calculations involve the overload factors and strength factors, for both wood and steel poles, as found in Tables 253-1 and 261-1A of the 1997 edition of the NESC. (Note that some of these values will probably be changed in the next edition of the NESC.) RUS has performed the calculations for steel pole "design loads" for various poles and the results are shown in the tables below. 12 Items of Engineering Interest August 2000 Required Steel Pole Design Loads
(Columns 1 and 2 from American National Standards Institute (ANSI) 0.51) (Design loads 2 feet from top of pole) TABLE 1 - NESC GRADE C STRUCTURES
(RUS Tangent and Small Angle Assemblies) (Not at a Crossing) (For New and Replaced Grade C Structures) ANSI 0.51 Wood Pole Class H1 1 2 3 4 5 6 7 Wood Pole Design Load (lbs.) 5400 4500 3700 3000 2400 1900 1500 1200 Steel Pole Design Load (lbs.) 5800 4800 4000 3200 2600 2000 1600 1300 TABLE 2 - NESC GRADE B STRUCTURES
(RUS Deadend and Large Angle Assemblies) (Not at a Crossing) (For New and Replaced Grade B Structures) ANSI 0.51 Wood Pole Class H1 1 2 3 4 5 Wood Pole Design Load (lbs.) 5400 4500 3700 3000 2400 1900 Steel Pole Design Load (lbs.) 3500 2900 2400 2000 1600 1200 TABLE 3 - NESC GRADE B STRUCTURES
(RUS Deadend and Large Angle Assemblies) (Not at a Crossing) (For Existing Grade C Wood Structures to be Replaced with Grade B Steel Structures) ANSI 0.51 Wood Pole Class H1 1 2 3 4 5 Wood Pole Design Load (lbs.) 5400 4500 3700 3000 2400 1900 Steel Pole Design Load (lbs.) 6600 5500 4500 3600 2900 2300 13 Items of Engineering Interest August 2000 RUS regulations require a minimum of NESC Grade C construction in the design and construction of distribution lines and structures. NESC Section 24, Grades of Construction, and RUS may require higher grades of construction for certain structures, locations, and conditions. For example, deadend structures and line angle structures where the transverse loads are more than 500 pounds per conductor involve additional calculations (such as loading trees) to determine the required minimum steel pole strength and pole class. Thus, RUS advocates that these types of structures (and steel pole selection) be designed (1) under the direction of a registered professional engineer, and (2) meet NESC Grade B strength requirements. The design of unguyed angle and dead-end steel pole structures should consider pole deflection and greater embedment depths. Extreme ice conditions and appropriate high winds should be considered in the design loads. Questions or comments regarding proper selection and installation of steel poles should be sent to: Robert Lash, Chief, Transmission Branch Rural Utilities Service, Stop 1569 1400 Independence Avenue SW Washington DC 20250-1569 Phone: (202) 720-0486 Fax: (202) 720-7491 Email: blash@rus.usda.gov OR Donald Heald, Engineer Rural Utilities Service, Stop 1569 1400 Independence Avenue SW Washington DC 20250-1569 Phone: (202) 720-9102 Fax: (202) 720-7491 Email: dheald@rus.usda.gov G: REQUEST FOR RUS APPROVAL TO USE STEEL DISTRIBUTION POLES Borrowers requesting RUS approval to use steel distribution poles should send their written request and supporting information to the appropriate regional Engineering Branch Chief at the address given below. Charles M. Philpott Chief, Engineering Branch Northern Regional Division Rural Utilities Service, Stop 1566 1400 Independence Avenue SW Washington DC 20250-1566 Phone: (202) 720-1432 Fax: (202) 720-1411 Email: cphilpot@rus.usda.gov OR Louis Riggs Chief, Engineering Branch Southern Regional Division Rural Utilities Service, Stop 1567 1400 Independence Avenue SW Washington DC 20250-1567 Phone: (202) 720-0848 Fax: (202) 720-0097 Email: lriggs@rdmail.rural.usda.gov 14 Items of Engineering Interest August 2000 Part II: Information Needed by RUS for Case-by-Case Approval of Steel Distribution Poles Before granting approval, RUS needs all of the information requested below to determine if the steel pole application will result in safe and reliable construction and meets all of RUS' requirements. 1. Indicate the maximum number of steel poles to be used. 2. Indicate the name of the steel pole manufacturer. 3. Define the project or location(s) where the steel poles will be installed. 4. In addition to "experimental purposes to obtain experience," furnish sound reason(s) for using steel poles. 5. Indicate that only RUS accepted materials are to be used. Otherwise, see Section A of steel pole guidelines regarding the need to request material approval. 6. Indicate that only RUS standard construction is to be used. Otherwise, please furnish sufficient dimensioned drawings and other technical information for RUS' evaluation of the design. See Sections A and B of steel pole guidelines. 7. (If, and only if, the design has less than a 300 kV withstand strength [see guidelines, Section B], then briefly describe assemblies and materials to be used and anticipated impact [if any] on system power quality and reliability and materials.) 8. Describe raptor protection measures, if any, that are to be incorporated into the design. Note that RUS recommends that raptor protection be considered in distribution line designs. Lines using steel poles may require additional consideration. See guidelines, Section D. 9. Indicate that the determination of the class of the steel poles for each application is based on the proper engineering calculations performed by a competent person. (See guidelines, Section F.) If you have any questions or need additional information regarding RUS approval or the use of steel distribution poles, please feel free to contact any of the persons identified in the above guidelines. Update of Bulletin 50-3 (D-804) ­ 12.47/7.2 kV Construction Standards
Presently RUS is updating Bulletin 50-3, "Specifications and Drawings for 12.47/7.2 kV Line Construction." This bulletin was last updated in 1983. A first draft of the bulletin with proposed changes has been completed and is being circulated within RUS for comments. 15 Items of Engineering Interest August 2000 RUS is proposing some major changes in the update of this bulletin. All of the construction assembly numbers will be changed to conform to RUS' updated standard format numbering scheme as explained in Bulletin 1728F-800, "Assembly Unit Numbers and Standard Format". This is the same standard numbering format used in Bulletin 1728F-803, "Specifications and Drawings for 24.9/14.4 kV Line Construction" which was published in the Federal Register in December, 1998. RUS realizes that it will take time for borrowers to become familiar with the new numbers and also that most borrowers will need to make changes in their computer software. Thus, RUS will allow adequate time between the date that the future new 12.47/7.2 kV construction standards is published and the date it will be made effective. Also to help borrowers, the new standards book will contain an appendix which shows the conversion of the old assembly numbers to new ones when applicable. Just like new Bulletin 1728F-803, the new 12.47/7.2 kV construction standards book will be divided into 19 sections wherein each section pertains to a different type of assembly unit. Nearly all of "M" (miscellaneous) assemblies will either be eliminated or renumbered for ease in locating in the book. The future new bulletin will also contain "design parameters" on most drawings and tables showing the maximum line angle allowed on pole-top assemblies. Also, just as in Bulletin 1728F-803, stirrups will be allowed for certain construction conditions, a 3 inch square, curved washer will be required for all primary and neutral deadends, and a 2 ¼ inch washer will be required under the shoulder of all 7.2 kV crossarm pins. The last two items are needed to provide greater strength for assemblies and allow greater line angles, respectively. Please note that the above changes in the new 12.47/7.2 kV construction standards book are proposed changes and will not be required or finalized until the new book is published as a proposed rule, all comments are addressed by RUS and then published as a final rule. Your questions, comments and suggested are welcomed by RUS. If you would like more information or have any questions, please call Jim Bohlk, Electrical Engineer, Distribution Branch, at (202) 720-1967. Bulletin 1728F-803, Specifications and Drawings for 24.9/14.4 kV - Corrections
In December, 1998, RUS published Bulletin 1728F-803, "Specifications and Drawings for 24.9/14.4 kV Line Construction." We have identified the following errors since the first printing of this bulletin. Please make the following changes in all of your copies of Bulletin 1728F-803. TABLE VII, Maximum Line Angles on Spool Insulator Assemblies, at the beginning of Section "N", has the wrong value (1,500 lbs./conductor) entered for the designated maximum transverse load for ANSI Class 53-4 spool insulators. The correct value is 2,250 lbs./conductor, which is fifty percent of the mechanical and electrical (M&E) strength for this class of insulator. Thus, all of the line angles are incorrect; they are smaller than they need to be. The attached table (Exhibit 1) has the correct designated maximum transverse load value entered and the subsequent, calculated line angles (which 16 Items of Engineering Interest August 2000 are greater) and are now correct. Please make copies of the attached table and replace TABLE VII in each copy of Bulletin 1728F-803. The drawings of Assembly "VD1.81L" should show the outside clamp type crossarm pins (item "f") 8 inches from the end of the arm and on Assembly "VD1.83L" the clamp type crossarm pins should be arranged the same as shown on the "VD2.91L" assembly drawing. On Assembly "VA5.21,VA5.31" the neutral tying guide should be "L2-2G" and not "LG.2G." Change the quantity (QTY) of material items on the following assemblies: Assembly VC2.51 VB3.1 Item "a" "d" "o" "ek" Description Insulators, white 3" square, curved, washer Bolts, eye Locknuts 3" square, curved, washer 2 ¼" square washer Bolts, eye Locknuts 3" square, curved, washer 2 ¼" square washer 3" square, curved, washer 2 ¼" square washer 3" square, curved, washer 2 ¼" square washer Change From 1 2 2 2 Change to 2 3 3 3 add 2 VB6.21 "d" "d" 12 12 12 10 8 8 add 1 VC4.2L "o" "ek" VC5.21, 31 "d" "d" 11 10 add 2 VC6.21, 31 "d" "d" 12 10 add 1 E1.1, E1.01 "d" "d" 1 0 If you would like more information or have any questions, please call Jim Bohlk, Electrical Engineer, Distribution Branch, at (202) 720-1967. 17 Items of Engineering Interest August 2000 MATERIAL and PROCUREMENT
RUS Acceptance of Fiberglass Crossarms
RUS is now including fiberglass crossarms in RUS Informational Publication (IP) 202-1, "List of Materials Acceptable for Use on Systems of RUS Electrification Borrowers." RUS has developed a requirements sheet for the acceptance of fiberglass crossarms and has invited a number of manufacturers to submit applications for acceptance. Fiberglass arms have to comply with the following requirements to be considered for acceptance by RUS for inclusion in the RUS List of Materials: · · · · Meet the same load capacity as the standard wood crossarms (unbraced); Meet the same cross section as the wood crossarm; Meet the same environmental requirements as the wood crossarms