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Analysis of Unbalanced Snow Loads 1997
ryrmrayryryrmrmmeerrmrmrtryrTrTryryrT"ryANALYSIS OF UNBALANCED SNOW LOADS on the ANCHORAGE-FATRBANKS INTERTIE Prepared for: INTERTIE OPERATING COMMITTEE c/o Alaska Energy Authority 480 West Tudor Road Anchorage,Alaska Prepared by: DRYDEN &LaRUE,INC. 6436 Homer Drive Anchorage,Alaska March 7,1997 C:\IC\REPORT3 Table of Contents I.INTRODUCTION ..ww.ee ee ees Il.HISTORY «2.1...ee es 1989 D&L dL ee ee ee eee ee ee ee 1990 D&L weeeeeeeeenae 1991 H.Brian White 2.2...0...ee ee ee ee 1992 D&L dL eeeeeeeeeas 1995 D&L LL eeeeeeeeeeeeeee 1996 D&L weeeeeeeeenes III.SUMMARY OF PROS &CONS OF SELECTED OPTIONS ............ Line Monitoring ....0....eeeeeeeeeee Ice/Snow Melting ........eeteeens Convert to Inverted V's wweeeens Inset Prop Structures 22...ee ee es Inset Towers 6.1 eeeeeee IV.PRESENT STATUS OF SNOW LOAD MONITORING SYSTEMS....... V.PRELIMINARY ALARM LEVELS FOR THE ANCHORAGE-FAIRBANKS INTERTIE SNOW LOAD MONITORING SYSTEM ................ Setting the Alarm Levels ........Doce e eee e eee eee eeeeee APPENDICES Excerpts from the NESC and Interpretations Alarm Levels Ice/Snow Melt Options Literature Review Correspondence CopiesPYNE REFERENCES I.INTRODUCTION The Anchorage-Fairbanks Intertie has had several outages during snow storms caused by phase- to-ground faults.Both the phase conductors and shield wires have been observed to sag well in excess of design sag due to these storms.The increased sags are due to several factors including the effects of span-to-span differences in the amount of snow on the wires.This can happen either by different amounts of snow accumulating in each span or by snow falling off some spans earlier than others or by a combination of the two.When the line is unevenly loaded from span to span the insulators swing towards the loaded spans reducing the conductor tension in the loaded spans and increasing the sag over what would be expected with the same snow loading evenly applied to all of the spans (Figure 1). This is the latest report in a series of letter and draft reports starting in 1989 describing the Unbalanced Snow Loading phenomena on the Anchorage/Fairbanks Intertie.The previous reports contain analysis and detailed descriptions of various options for solving the problem. The reader should refer to these previous reports as needed,this report is intended to be a supplement to those reports. As with many projects,the response to unbalanced snow loadings is an "on-going"process and any report can only represent a moment within this continuum.Following is a brief description of the history of this project with summaries and excerpts from the previous draft reports and a current status. Sag if Towers and Insulators are Locked Against Movement Sag with Tower and Insulator Movement _/S 21 SPANS INVOLVED MIDDLE SPAN LOADED TO 3.3297 Ib/ft. OTHER SPANS LOADED TO 1.0760 Ib/ft. 10 SPANS INVOLVED END SPAN LOADED TO 3.3297 Ib/ft. OTHER SPANS LOADED TO 1.0760 Ib/ft. Figure 1 . Multiple Spans with Unbalanced Snow Load in One Span II.HISTORY 1989 D&L On October 19,1989 Dryden &LaRue (D&L)performed a field survey of the Anchorage/ Fairbanks Intertie at Caswell Lakes Road.The line had suffered an outage due to contact with trees in the right-of-way at the road crossing.The initial concern was that the wire had been overloaded.It was determined the wire had not been overloaded and stretched "...wire is at about the tension one would expect for its age ...the line appears to be designed as a normal 345 kV line and is functioning per the design".It was suggested the 12 feet of ground clearance experienced at Caswell Lakes road could have happened if this span alone was loaded "...wet snow was dropped from the adjacent spans and the insulators were assumed to swing several feet into the span ...".In essence the field survey determined there was no evidence of excessive loadings and unbalanced load was a logical explanation for the experienced low clearance. 1990 D&L On January 8,1990 D&L submitted a letter report "Design Practice for Ground Clearances under Unbalanced Span Loads"which described discussions of these phenomena with other professionals.Transmission line experts,including;Brian White (Canadian Consultant),Frank Denbrock (Vice-Chairman of NESC committee),Bob Peters JEEE Working Group to NESC), Lee Belfore (Chief REA Transmission Branch),and several other engineers from utilities in Canada and the U.S.,were contacted for input.This group concluded:1)unbalanced span loadings do happen on other lines although fairly rarely;2)"...they would expect it (reduced 'ground clearance)to occur on the typical high voltage line under the same circumstances",and 3)"...The NESC does not address ground clearances when one span is loaded with ice or wet snow and the adjacent spans are not".This report also offered suggestions for data collection and guard structures at the two road crossings.In general,this report reviewed experiences of other engineers and determined this type of loading could and has happened on other lines with similar results and the NESC does not address it. 1991 H.Brian White Mr.H.Brian White of Quebec investigated a new outage and offered some explanations in his January 31,1991 report.He reviewed three basic problems --increased sag in the static and phase wires and flips in the phase subconductors.He concluded that simple elongation of a loaded conductor does not explain the clearance,"...It is evident that 'elastic deformation'will not bring the conductor down to where it was in the recent events."He also concluded unequal loading was the culprit,"...It has been found the flashovers between wires and the very low conductors are the result of system distortions whereby unequal span loadings of frozen snow have moved slack from one span to another..." In a letter dated February 18,1991 Mr.White offered some possible means to mitigate the problems including: -3- Remove the overhead ground wire Remove the 17-inch link in the ground wire Reverse the ground wire arms Shorten the insulator strings Resag the phase conductors Install inverted V-string insulators|iiaaad1992 D&L On July 7,1992 D&L produced a draft report titled,"Draft Investigation of Effects of Unbal- anced Snow Loads on the Anchorage-Fairbanks Intertie.".This was a more extensive study than the previous work and included: Outage review Determination of areas affected by unbalance Analysis of snow accretions and density Review of lightning performance Analysis of tower response to longitudinal loads Mechanics of unbalanced snow loads Analysis of how unbalance would affect sag and towers A list of mitigating options Preliminary cost estimates for optionseffeteOeOeOO This report quantified many of the previous assumptions with specific analysis of conductor and tower behavior.It also reviewed outage data to determine the areas affected. Snow density was a major component in this analysis and could only be assumed,"...we have assumed 4 inches of radial snow with a density of 5 lb/ft?»While there is circumstantial evidence that this assumption is reasonable,there is no hard evidence to prove it...".A review of snow literature,local weather data and discussions with service linemen led to the following table of approximate density values for fresh "new"snow (Table 1). Table 1 RANGE OF SNOW DENSITIES Description Density Ib/ft' Very Light Powder Snow 2 Powder Snow 3 6 Heavy Powder 7 9 "Snow Ball Snow"10 14 Wind compacted snow 15 45 Obviously the selection of density has many possibilities and our estimate is only a guess,the report states,"...To our knowledge,there have been no measurements made to provide reliable data on the weight of snow that has accumulated and the frequency at which it can be expected to occur.The snow load used in the comparisons is our best guess...". Based on previous work and this review,seven options to mitigate the problems were presented including: Removing the guy yokes Pretensioning the fore and aft guys Resagging conductors Removing the shield wires Shortening the insulator strings Installing inverted V-strings Combinations of the above optionsfeteeteo The report also included estimates of the performance of the options,the effects of the changes on tower structural loads,and cost estimates. 1995 D&L On June 5,1995,D&L produced another draft report "Initial Analysis of Unbalanced Snow Loading Options".The purpose of this study was to review previous options and to investigate any and all other possibilities.Some new options were added to the list: Snow melting Monitoring of unbalanced conditions Mid-span guard structures Inset structures Changing suspension insulators to posts5iiaiad Previous options from the 1992 study and the new ones were compared in a table of estimated ground clearances for each modification (Table 2). Table 2 GROUND CLEARANCE COMPARISON Est.Ground Proposed Modification Clearance (ft) Do nothing (wire laying on ground)0.0 Shorten I strings,remove yokes,pretension guys 7.6 Shorten I strings,remove yokes pretension guys,resag cond.13.8 Convert to Inverted V-strings,remove yokes,pretension guys 17.1 Guard structures (height set to maintain this clearance)17.0 Convert to inverted V-strings,remove yokes,pretension guys,resag 22.8 Convert to post insulators above crossarm 37.5 Inset 80-foot towers,345 kV insulation,not resagged 38.4 i)Several assumptions were made to produce the table."...It was assumed that as part of the modifications,the shield wire could be removed to eliminate conflicts with the phase conductors. The sags under unbalanced snow loads used to produce Table 2 were calculated using Dryden &LaRue's "Ice9"program and its predecessors.All calculations are based on an unbalanced snow load of 4 inches radial snow with a density of 5 Ib/ft®.One span is assumed to be loaded in the middle of a long tangent of bare spans.The towers before modification are assumed to have a conductor attachment height of 80 feet;spans are assumed to be 1,225 feet.Unless noted,the modifications are insulated for 230 kV..." Snow removal by melting was a new approach introduced in this report and "...It appears to be feasible to prevent or remove snow and ice by heating the conductor...”.A review of literature on the subject found several examples of successful applications. Monitoring of the snow accretion and insulator swing angle was another new concept introduced in this report.Based on a single tower installation in 1993 on the Tyee line,we believed it was possible to predict line conditions with this monitoring equipment.Power supplies for remote locations are a difficult problem and several options were discussed. Guard structures had been introduced as a solution to the first low clearance problem in 1990. This concept was considered for the entire 52-mile-line section with two configurations.Wire movement after contact with a guard structure and cost made this option unattractive. Inset structures offer a solution to the sag problems,but this is a very expensive option. Replacement of suspension insulators with posts on the top of the crossarms created considerably more ground clearance and essentially stopped the movement of conductor from span to span. A review with the IOC selected the more promising of the modifications.Cost estimates and comparisons of the advantages and disadvantages were the next step. -6- 1996 D&L In February 1996 D&L produced a "Preliminary Cost Estimates”letter which outlined estimated construction costs for the various options to mitigate the effects of unbalanced snow loading. They include: ¢Converting the insulators to inverted V-strings @ Insetting prop or guard structures @ Insetting new structures In addition,cost estimates were made for installing two different types of monitoring systems and for installing equipment to melt ice and snow from the conductors.Conversion of the insulator strings is described in Dryden &LaRue (1992). In March 1966 a revised budget cost estimate for snow/ice melting equipment was transmitted. This estimate was based on actual quotes from manufacturers of DC snow melting equipment and showed snow/ice melting to be a more feasible alternative. Table 3 shows the final list of alternatives and their estimated costs. Table 3 CONSTRUCTION COST ESTIMATES Line Monitoring (4 locations)$440,000 Line Monitoring (SLMS)1,300,000 Ice/Snow Melting 2,830,000 Convert Insulators to Inverted V's 3,300,000 Inset Prop Structures 7,100,000 Inset H-frames 17,000,000 Il.SUMMARY OF PROS &CONS OF SELECTED OPTIONS There have been several options studied and comparisons made between each option's estimated ground clearance under unbalanced snow loading and its installation cost.A recap from previous reports and some new discussion is presented here as to each option's advantages and disadvantages. Line Monitoring Two levels of monitoring were considered.The first included four sites situated as recom- mended by the meteorologist,M.C.Richmond,to capture the occurrence of snow storms which could cause accumulations of snow on the southern end of the line.Monitoring suspension insulator tensions and inclinations at four sites would give a positive indication of when snow is building up to significant level.The four locations are: Near Douglas Substation Near Caswell Lakes Near Sunshine (Note that this is near Stevens Substation) Near Susitna River CrossingSiaad For this alternative,a load cell and longitudinal inclinometer would be provided in all three insulator assemblies and a transverse inclinometer would be added to one outside phase.The additional load cells would provide more information about the weight of snow without increas- ing the number of sites.The transverse inclinometer would provide some information about transverse wind on snow loads.Determining when the snow begins to fall off and cause increased sags would require either more towers to be instrumented or to have identified the conditions that cause the snow to begin to fall off. The other monitoring system consists of instrumenting sufficient towers to try and "see"snow load and the movement of slack between spans.This system was selected as the best option. The snow load monitoring system consists of 24 instrumented transmission towers,2 weather stations and a communications base station.The instrumented towers are spaced approximately every 10 towers (2 miles)between Douglas Substation and Clear Creek (Chunilna Creek),see Drawing I-2.The weather stations are at Douglas and Stevens Substations.The base station is located in Anchorage Municipal Light and Power's dispatch center in Anchorage.The system is described in more detail in the next section of the report. During investigations of the ways to instrument the towers,it was suggested that the angle between the yoke and the guys could be monitored to determine when unbalanced snow loads are occurring.The advantage of this is that the instruments could be installed and maintained from the ground. Measuring the angle of the yoke could be done using bell cranks and either an LVDT (linear voltage differential transformer --a standard sensor for accurate linear measurements)or potentiometer.The angle of the yoke compared with a vertical reference could be measured -8- with an inclinometer.Measuring the yoke angle would only see unbalances on the outside phases.The yoke would not change angle for unbalanced loads on the center phase.Unbal- anced forces could be detected with load cells in the lower guys.Instruments in these locations give indirect measurements that are subject to a good deal more interpretation to provide meaningful data than measurements made in the insulator strings. The increase in weight due to snow and ice accumulation could also be detected and an alarm sounded using a simple electro mechanical device that includes a spring and a limit switch.Goia (1994)describes such a mechanism and its use.This option was not chosen due to the lack of a commercial model and the advantages in the information gathered by using a standard,readily- available commercial load cell. In both instances,the instruments would communicate via cellular phone.The instruments could be interrogated to look at conditions during certain windows when the phone is powered up. They would also call in to sound an alarm when the insulator swing exceeds a preset level. Regardless of the monitoring selection,power for remote sites is a major problem in design. The Snow Load Monitoring System uses a battery bank sized to last through the winter for its power supply.Other options considered for powering the tower sites included the following (note that all of these options would still require battery backup): Solar panels Wind generators Power PTs Energizing the shield wire Insulating the grounded tower leg of a segment of shield wire "eeeSolar Panels -Solar panels have the advantage of being readily available sources of power for remote locations.The problem in this area of Alaska is that there is little sun light during November,December and January.There is also great variability from year to year.The sunniest December has about six times the potential solar power as the cloudiest (see data for Talkeetna in Marion &Wilcox 1984).This is compounded by the fact that the panels them- selves can be occluded by snow.They can also be easily damaged by gunshots from vandals requiring replacement.A large battery capacity must be provided to carry the system through the middle of the winter.Solar panels were installed at two sites,towers 69 and 150 to gain experience. Wind Generators -We did not investigate wind generators in great detail due to our belief that wind speeds are generally low in the area where the tower instruments are installed;however an appropriate generator,controls,and battery storage system may be feasible.Wind generation would not be affected by lack of daylight in the winter,however operation could be affected by buildups of snow and ice. Power PTs -PT's were investigated as a power source and rejected due to their high cost and weight.PTs have the advantage of providing large amounts of power compared to the needs of an instrument package.PTs are standard power system components and can be expected to have good reliability.They also must be attached to a phase of the line which may have some -9- effect on overall line reliability.It would be possible to mount a PT on a bracket attached to the tower. Shield Wire -The shield wire is insulated,segmented and grounded at the center of each segment.A shield wire could be energized as a primary to provide power to an instrument site. Disadvantages include additional switching to deenergize and ground the shield wire before work is performed on towers and increased hazard of lightning damage to the instruments. Shield Wire -It may also be possible to obtain sufficient power by using a segment of the existing shield wire to drive a power supply either with the circulating currents or by connecting the power supply between the shield wire and ground at the grounded tower.We were not able to find a source of either a commercially available power supply or a tested design for a power supply using this source of power. Pros @ Least expensive ¢Provides information for future designs @ Uses standard hardware Cons ¢Does not increase ground clearance @ Requires an outage and line crew to remove snow and ice from low spans Ice/Snow Melting Heating the conductors with larger current flows to melt snow and ice has been used in the past by utilities in the U.S.and is still used by many utilities in other countries around the world (see literature review in the Appendix 3).Our conclusions about the feasibility of ice/snow melting are:SdRemoving snow and ice by heating the conductor is feasible. @ The power required to ensure snow and ice melting is approximately 26 watts per foot of wire. @ Melting snow and ice from the Anchorage-Fairbanks Intertie using AC power is not feasible,a low voltage direct current melting system must be used. Manitoba Hydro,which has an extensive program of snow and ice melting,has published a manual "Ice Storm Management of Overhead Line"(Wilson 1993)containing guidelines for the current required to melt ice for various different size conductors.A 954 kcmil 54/19 cardinal has an estimated melting current of 1230 amps which corresponds to 27 watts per foot based on the DC resistance @ 20°C of .09452 ohms/mile.Sporn (1939)reports currents of 500 to 750 amps being needed to melt ice from 397.5 kcmil ACSR conductors on the American Gas and Electric System.He also reports that it took forty minutes to remover 3/4-inch of ice with a short circuit current of 650 amps.Assuming 397.5 ACSR 30/7 Lark conductor with a DC -10- resistance of .2243 ohms/mile,melting ice requires on the order of 11 to 24 watts per foot. A system to melt ice and snow from the two bundle 954 ACSR 45/7 Rail used on the Anchorage-Fairbanks Intertie will need the ability to furnish currents on the order of 2500 amps per phase (1250 amps per subconductor)which produces heating of 26 watts per foot. Calculations made by Golden Valley Electrical Association (Ritter 1996)determined that there is not sufficient short-circuit current available at Douglas substation to melt the snow by shorting the phases together either at 138 kV or after stepping the voltage down using a transformer.It is,however,feasible to melt the snow and ice using a direct current system. Cost estimates are based on installing the ice melting system at Stevens substation.DC melting would be performed from Stevens to Clear Creek and from Stevens to Douglas Substation. Using two of the three phases switched together at Clear Creek or Douglas in an out and back DC circuit from Stevens would require two melting operations in each direction.The DC resistance of Rail conductor at 0°C is .08759 ohms per mile per subconductor.It is approxi- mately 26 miles each direction from Stevens.At 2500 amps per phase (1250 amps per sub- conductor),the power required is 26 watts/ft and just over 14 MW total.DC voltage required is 5700 volts. ABB was approached to determine availability and cost of equipment.They proposed a system consisting of two 138/5.2 kV rectifier transformers and two thyristor controlled rectifier units of 8 MW capacity each at 7000 volts DC (Reed 1996,see Appendix 4). It would be of interest to add monitors to the Willow Line just south of Douglas Substation.It is our understanding that the Willow line has not had any unbalanced snow problems.This could be due to the difference in Joule heating between the Intertie's 2-bundle 954 Rail and the Willow line's single 556.5 Dove.Instrumenting the Willow line would answer the question of whether the Joule heating in that line is sufficient to prevent the accumulation of snow. Pros +Relatively inexpensive +The entire section of line can be cleared of snow and ice Cons +Ground clearance may be temporarily impaired during the snow removal due to differences in when spans are cleared.This would depend on how much snow built up before the melting begins.Limiting snow buildup before beginning melting should prevent this. +Ice melting is most likely to be required when snow and ice are also causing problems on distribution system that demand attention. +Access for switching at the North end at Chunilna (Clear)Creek is difficult. +The high currents may cause damage to the line if there are any high resistance connections;however,periodic infrared scans during melting could be used to locate and repair hot spots. -ll- +The switching sequence to connect the ice melting system is critical --a mistake could damage the ice melting system and/or cause problems on the AC system. Convert to Inverted V's The existing 345 kV insulator strings would be converted to inverted V-strings.The yokes would be removed and the guys would be attached directly to the anchor piles.The guys would be pretensioned to reduce tower movement under unbalanced longitudinal loads.Shield wire peaks would be reversed to increase clearance between the phase conductors and the shield wires. Pros +Increases ground clearance under unbalanced loads +Relatively inexpensive Cons +May not eliminate outages and ground clearance problems +Increases longitudinal loads on crossarm Inset Prop Structures Preliminary designs of two configurations of guard structures were made.The guard structures would be installed at the center of the existing spans.They are intended to support the conduc- tor when unbalanced snow loads cause the sag to increase. Three single pole wood structures with insulated sections of bus would be inset at approximately mid span to catch the wire when it sags below normal clearances.One difficulty with this concept is that the height of the prop is limited by maintaining some clearance to the line under normal operation but having it high enough to do some good when unbalanced loads occur. Pros +Increases ground clearance under unbalanced loads Cons May not completely eliminate outages and ground clearance problems Unproven concept Looks strange Abrasion damage to wire must be addressed Permitting and environmental issues may need to be addressedeft¢@-12- Inset Towers An H-frame inset structure was designed to cut the spans approximately in half.For this study, the insets'conductor-attachment heights were assumed to be approximately the same height as those of the existing towers. New tubular steel H-frame structures would be inset in every span.The towers would use the same insulators and hardware as the existing structures (i.e.would be insulated at 345 kV).The H-frames would be set in sections in between the existing phase and shield wires. Pros +Increases ground clearance the most under unbalanced loads,should "cure the problem"except in the most unusual circumstances +No operational intervention required Cons +Most expensive +Increased maintenance cost +Permitting and environmental issues may need to be addressed -13- IV.PRESENT STATUS OF THE SNOW LOAD MONITORING SYSTEM After reviewing the cost estimates and advantages and disadvantages of the various alternatives. The Railbelt Utility Group elected at their February 13,1996 meeting to proceed with installa- tion of the Snow Load Monitoring system for approximately 23 towers.The system as installed includes instruments at 24 towers,weather stations at Stevens and Douglas Substations and a base station computer for communications and alarms at ML&P's dispatch center in Anchorage. The instrumented towers are spaced approximately every ten towers (2 miles)between Douglas Substation and Clear Creek (Chunilna Creek),see Drawing I-2. At each instrumented tower the following are measured (see Drawing I-1): East insulator tension Longitudinal inclination of the East,Center and West insulators Air temperature Battery temperature Power supply voltageeeeeo¢At the Douglas and Stevens weather stations the following are measured: Wind speed Wind direction Barometric pressure Air temperature Relative humidity Precipitation5iAdiaa The base station communicates with the instrumented towers and weather stations using cellular telephones.Drawing I-2 shows the cellular telephone sites in the vicinity of the line,the telephone numbers and the specific cell site used by each tower. The monitoring system includes the ability to preset alarm levels.When a tower's insulator tension exceeds a programmable alarm level,the data logger at the tower calls the base station and uploads the data,the base station then sets an alarm condition for that tower and sounds an alarm which remains active until the alarm is acknowledged by the dispatcher.Similarly there are positive and negative inclination alarm levels that trigger a call from the tower to the base station. In order to save power at the instrumented towers,the cellular transceivers are only powered up for five minutes every two hours.Each of the twenty-four towers has a separate window in which to make and receive calls.Power for the tower sites is provided by a battery bank designed to last for six months without recharging. -14- 18'-0 _INCLINOMETER| SEE DETAIL 2|&3 a CROSSARM .<0 1'-8"0.D.PIPE fo)Ty71 ---+LOAD CELL AND oO}+P 2 H NCLINOMETER (BY _EQUIP.SUPPLIER) !5 |14 BELLS AFTER ===LOAD CELL"i INSTALLATION 0 SEE DETAIL 1 18 BELLS 9 UPPER LEGS 2'-0”O.D.PIPE PHOTOVOLTAIC MODULES (BY EQUIP.SUPPLIER) ele Lt Ld 55 | O}O LOWER LEGS olin oo -0”O.D.PIPENSse olo wy!ANTENNA AND |60 ENCLOSURE FOR DATA AQUISITION SYSTEM (BY EQUIP.SUPPLIER) Oo | IN ©-@ ENCLOSURE .+H]ON FAR SIDE >oO -| . Nee ° 5|AP eee ENCLOSURE (BY EQUIP.SUPPLIER) 45'-7 3/4”(80°TOWER) 48'-11 7/16”(85'TOWER) ELEVATION LOOKING NORTH 200 100 0 200 SCALE:1°=200” aoe +Joy,NORTH i EXISTING SouTH (REPLACES(4)EXISTINGBELLS)\\FURNISHEDBY"EQUIPMENTSUPPLIERINCLINOMETERiANDMOUNTING BRACKET (BYehpstEQUIP.SUPPLIER)ALD,AONmeae EXISTING LOT--55-12 EXISTING LOCK 20S580 DETAIL 1 (LOOKING SOUTH)10 IN. SCALE:1”=10” EXISTINGveBETHEA ASH-66A 12”EXISTINGee LOT-55-1287 INCLINOMETER AND MOUNTING BRACKET (BY EQUIP.SUPPLIER) NX EXISTING LOCK 208580 DETAIL 2 (LOOKING SOUTH)10 IN. BETHEA ASH--66A 53"SOUTH NORTH SWING |SWING AEEBE (LOOKING WEST)A HeerelTTTTebielelsleIs3 :7 Bells 2 «EXISTING a ee Bee &g ollOLBETHEAASH-66A No Z oi1ATA\tt - {''<an z:oO =7 INCLINOMETER O25AND.MOUNTING nS SuBRACKET(BY SESS SN EQUIP.SUPPLIER)26h 1 @ptaac :Gaz. ia tad <C 97;wmizs77/8 > SaAe =tu ==*E 34-EXISTING < BETHEA LOT-55-53 J =wl,HL EXISTING WaLOCK20S580os Soe -_Ss ae z i(a)DETAIL 3 >(LOOKING SOUTH)Eu105010IN.ms-oo TWO SCALE:1"=10 I=1 oO a)/Cor jane aaa Bane_-DéeL Ae Z Ascott take Parks Highway Ss -BYERS |dHEdH|a:AT,-ch.(aad ||"Nae a 7 =MACTEY 4 © <Douglas Sybststi en..SERRE6)a-oreenenen--<=-}A A Seaece D a"{lelalss Willow g----69° 79 1 g Tol-[dnlela e iv 90 t»wittow ta 109 !zaake”5 BI OCK 2 ------eem Neen ;!30 mi ot 3 EG >;ye :{BLOCK _3 See J Rs Stevens Substation tLBLULK Oe O2%e2w 9 22359xisof=5oO3.1.0 5 8 e298xceeMACTELoot” SCALE IN MILES Hoe ogSodLu"SAack<<3 98S BLOCK TOWER POWER-UP_TIME TOWER CELLULAR PHONE No.SUBSTATION CELLULAR PHONE No.<Sue 1 5 12:00 -12:05 am 5 230-3669 us --«DOUGLAS 230-2257 mre 23 2 59 12:05 -12:10 am 14 230-3670 <STEVENS 230-6075 r=az= 3 120 12:10 -12:15 am 23 230-3671 i =ome418112:15 -12:20 am 32 230-3672 Bu N © 1 14 12:20 --12:25 am 41 (907)232-5532 <S 7 2 69 12:25 -12:30 am 50 230-6074 Cy312912:30 --12:35 am 59 230-3673 - 4 191 12:35 -12:40 am 69 440-1359 1 23 12:40 -12:45 am 79 440-6451 2 79 12:45 -12:50 am 90 440-6452 3 140 12:50 -12:55 am 98 440-6453 NOTES:4 203 12:55 -1:00 am 109 440-6454 aA 1 39 1:00 -1:05 am 120 440-6455 Z T.A=CELL SITE LOCATION :2 90 1:05 -1:10 129 440-645 = 5 150 110 -1-15 om 10 wae a2 2.AT&T MONTANA CREEK CELL SITE = A 213 1:15 -1:20 am 150 440-6458 og WAS NOT IN SERVICE WHEN THE SNOW ee 1 4]1:20 -1:25 am 159 440-6459 Es LOAD MONITORING SYSTEM WAS INSTALLED.Ss 2 98 1:25 -1:30 am 168 440-6460 a _ 3 159 1:30 --1:35 am 181 440-6461 s 2; 4 222 1:35 -1:40 am 191 440-6462 a3! 1 50 1:40 -1:45 am 203 440-6463 Eis21091:45 --1:50 am 213 440-6464 =e 3 168 1:50 -1:55 am 222 440-6465 oanBRhae 4 231 1:55 --2:00 am 231 440-6466 DRAWING NOT 1 of1 V.PRELIMINARY ALARM LEVELS FOR THE ANCHORAGE -FAIRBANKS INTERTIE SNOW LOAD MONITORING SYSTEM The snow load monitoring system's purpose is to detect and sound alarms when the effects of unbalanced snow loads may have impaired ground clearances under the line.Insulator inclina- tion and insulator tension are monitored.The insulator tension indicates whether enough snow has accumulated on the conductors to potentially cause a ground clearance problem.The insulator inclinations indicate when unbalances have occurred that cause the insulators to move towards more heavily loaded spans making reduced ground clearances likely. An electronic load cell placed in the insulator string of one outside phase per tower measures the tension in the insulator string.When the insulator string is hanging vertically,subtracting the bare weight of the insulator string and conductor from the tension gives a direct measure of the weight of snow buildup.For small inclinations,the error in using the tension of the insulator string as a measure of the weight is small (with a swing of 10°the error is about 1.5%).The first question for alarm status is:Is there enough snow accumulated on the wires for the ground clearances to be impaired? By monitoring the insulator tensions,we can determine when sufficient snow has accumulated on the wires that a problem may be developing.This is based on the records from a similarly instrumented tower on the Tyee 138 kV line near Petersburg,Alaska which indicate the unbalance problems are caused more by the snow unloading unevenly either during or after a storm than by an uneven span-to-span buildup without unloading.If insulator tensions are increasing,a snow event is in progress.Unbalanced snow loads should be expected as the snow begins to fall off.If enough snow has not accumulated anywhere on the line,then even if one span is left loaded while the others around it are bare,there will not be a problem with ground clearances.An alarm level has been set for each tower based on the insulator tension.When this alarm level has been exceeded,it does not mean there are low ground clearances,just that there is a possibility there will be low ground clearances as snow falls off some spans either during the storm or after it has finished. All three insulator assemblies have inclinometers to measure their longitudinal swing.Longitudi- nal swings outside the narrow bounds caused by temperature differences are a direct indication of unbalanced loads on the wires (the unbalance could be from causes other than snow loads, for example a tree laying on the wires).In the worst case of one span heavily loaded with snow with all of the spans on either side bare,the swing of the insulators at the ends of the loaded span will be largest with swings decreasing from tower to tower as the distance from the loaded span increases.When the tower is enough spans away from the loaded span,the swing due to the unbalanced load is so small as to be indistinguishable from other causes of small insulator movements. Setting the Alarm Levels Use of the land underneath the line affects what ground clearance is needed.Two winter land uses have been identified:roads and areas where there is cross country skiing and snowmobile -17- traffic. There are a limited number of road crossings --the plan-profile sheets show road crossings at the Hatcher Pass Road,Hidden Hills Access Road,Caswell Lakes Road,a cat trail between structures 92 and 93,and Yoder Road.In addition there are roads and trails not shown on the plan-profile sheets including the road into Stevens Substation (note that the P&P's also do not show Stevens Substation)and a private driveway between towers 98 and 109.There are probably also some other trails used by four wheel drive vehicles,four wheelers,and similar all terrain vehicles. In all other areas we have assumed that the primary winter use of the right-of-way is cross country skiing and snow machining. The NESC does not address the question of ground clearances that must be maintained under unbalanced snow conditions except through the general requirements in Sections 10,12 and 200 (Appendix 1). Ground clearances in the 1990 to 1997 editions of the NESC are composed of three parts (Appendix A of the 1997 NESC):a reference component,a mechanical component,and an electrical component.The reference component is based on the height of the objects expected under the line.The reference component for highways is 14 feet which is the maximum over- the-road truck height allowed by highway regulations.The reference component for pedestrians is either 8 feet or 10 feet.Eight feet is used for clearances based on mechanical interference, for example;for insulated communications conductors.Ten feet is used for bare overhead lines. Ten feet appears to be based on a pedestrian holding an umbrella over the head,a person carrying a ladder or a worker using hand tools (see excerpts from Clapp in Appendix 1).In the 1981 code,which was in effect when the line was constructed,a pedestrian was assumed to be 9 feet high rather than 10 feet.The mechanical component for overhead lines is made up of 1.5 feet for a non-rigid part and .5 foot for bare conductors which totals 2.0 feet.The electrical component of clearance depends on the voltage.For 138 kV it is 4.6 feet.This is based on the clearance required for a switching surge with an additional 20%added for intangibles.The clearance required for normal power frequency voltage without a surge is about 1 foot'. The comfortable high reach of the 99"percentile man wearing normal shoes is 89.6 inches or about 7.5 ft?.Adding 6 inches for thicker shoes and open fingers results in an assumed 8 feet tall skier that agrees with the NESC's height for a pedestrian without tools or an umbrella.We have assumed that snow machiners will also be within eight feet of the snow surface.Eight feet has been used as the reference component in the clearance calculations.Note that a skier waving his poles above his head could be as tall as 12 to 13 feet (assuming 4 to 5-foot poles). 1 Electric Staff Division of Rural Electrification Administration,REA Bulletin 1724E-200,Design Manual for High Voltage Transmission Lines,U.S.Government Printing Office,Washington,D.C.1992, Section 7.2.3 page 7-3 and Table 7-1 page 7-4. 2 Calculated from Data in :John H.Calendar,Ed.Time Saver Standards for Architectural Design Data,5"Edition,McGraw Hill,New York,1974,pp17-18. -18- It should be born in mind that a transmission line will meet the intent of the NESC if the clearance is maintained just above the code value every day and hour of the year in situations where large volumes of traffic pass under the line every day (for example,a distribution line crossing a busy downtown street or an interstate highway). There are some additional factors that affect the clearance desired that are not addressed in the NESC.They are the accuracy of the installation (profile survey,structure location,structure heights,and sagging)and the height of the travel surface above the surveyed ground surface. The line was spotted using structure heights measured from the centerline of the hinge pin at the base of the X-tower to the conductor attachment point.In reality,the towers were installed with the hinge pin higher above the ground.The additional height is typically 6 inches for towers with rock foundations.Most of the towers in this section have pile foundations where the additional clearance is typically 2.75 feet or more.We have assumed that variations in the accuracy of the installation are covered by this additional clearance. Skiers and snow machiners travel on trails with surfaces that are near the top of the snow pack. Table 4 shows the largest snow depths that have been recorded at various locations in the vicinity of the line.Talkeetna has the longest period of record.A depth of 98 inches was recorded in February of 1951 and 97 inches in January of 1949.We have used 8 feet (96 inches)as the height of the travel surface for areas other than roads (a snow machine,skier or snow shoer will compress the snow a few inches).For roads,we have assumed that they are kept plowed and that the depth of ice and snow is a maximum of 1 foot. Tables 5 and 6 show that a ground clearance of 22.6 feet is desired for a skier in off-road areas and that 21.6 feet is desired over a road for a 14-foot-high truck. Another approach to determining the desired ground clearance is to assume that 60 hz clearance is maintained above the head of the 99"percentile man skiing on a typical snowpack (Table 7). Using the NESC adders for bare wire and cable,and assuming a snow depth of 5.0 feet,the desired clearance is 14.5 feet (a statistical analysis of snow depths could be done to determine the probability of a given depth). Assuming the desired ground clearance is 22.6 feet,the next step is to determine what snow load would be required to bring the wires within 22.6 feet of the ground if only one span in the middle of a long tangent is loaded.To do this,we assumed that a long tangent of 80-foot towers was spotted at the maximum span controlled by ground clearance.The line was originally spotted using a hot curve with a conductor temperature of 143.6°F (62°C)and a ground clearance of 30 feet.The maximum level span with an 80-foot tower that will maintain this ground clearance is 1260 feet.The design ruling spans between towers 1 and 237 are all either 1200 feet,1250 feet or 1275 feet. The ICE9 computer program,which calculates equilibrium sags with unbalanced snow and ice loads,was run for different snow thicknesses using a snow density of 5 lb/ft?(based on our analysis of ground snow densities during outages)a temperature of 32°F and a span of 1260 feet.With 1.75 inches of snow,the sag in the loaded span is 57.5 feet giving a ground clearance of 22.5 feet which matches well with the 22.6 feet desired (Appendix 2). -19- Table 4 HISTORIC SNOW DEPTHS' IN THE VICINITY OF THE SNOW LOAD MONITORING SYSTEM Record Snow Period Rec Depth™ Station Name Latitude”Longitude Elev of Record Length inches Caswell 6158 N 149 54 W 290 1948-1958 10 72 Chulitna Hwy Camp 6224N 15015 W 500 1973-1980 7 64 Chulitna River Ldge 6253 N 14950W 1250 1971-1987 16 77 Skwenta 6158N 15112 W 153 1939-1959 1971-1975 1979-1987 32 68 Talkeetna 5W 6219N 15015 W 430 1960-1962 1 75 Talkeetna 6218 N 15006 W 345 1922-1987 64 98 Tolovamkorga 6219N 15027 W 470 1963-1965 2 72 Trappers Creek 6219N 15014 W 360 1968-1970 2 26 Trappers Creek Camp 6224N 15015 W 500 1970-1972 2 86 Willow 6145N 15003 W 600 1960-1971 11 61 "Alaska Climate Summaries,Second Edition,Alaska Climate Center Technical Note Number 5, Arctic Environmental Information and Data Center (now Environment and Natural Resources Institute), Anchorage,Alaska,1989. "Record Lengths are conservatively taken as the difference in the years of the period of record,they could be 1 year longer. kee The section of line between Willow and Clear Creek lies in the range of 61 45 N to 62 30 N and 149 50 W and 150 05 W. -20- Table 5 SKIER GROUND CLEARANCE 138 kV Design Conditions: Unbalanced Snow Alarm Level. 32°F,1.75"Radial Snow @ 5 lb/ft',one span loaded in center of tangent. Line Section: Structures 1 to 240 Height Description (ft)Comments Allowance for Survey Errors”0.0 Height of travel surface above surveyed ground surface 8.0 Assumed snow depth Height of object under line (reference height)8.0 Skier™ Adder for non-rigid part 1.5 NESC Adder for bare conductor 0.5 NESC Electrical Clearance 230 kV 4.6 NESC 2.5 +Voltage Adder Allowance for template and sagging errors!0.0 Additional Clearance _0.0 22.6 "The structures were spotted with no consideration given for the distance from the ground to the point the base of the tower is attached to the foundation.This has an approximate minimum of 0.5 ft for rock foundations,most of the towers have pile foundations where the approximate minimum additional clearance is 2.75 ft. **8.0 ft corresponds to the comfortable high reach with open fingers for the 99"percentile man.It is also the reference height used for a pedestrian in the NESC for calculating clearances for mechanical interference. -21- Table 6 ROAD GROUND CLEARANCE 138 kV Design Conditions: Unbalanced Snow Alarm Level. 32°F,1.75"Radial Snow @ 5 Ib/ft?,one span loaded in center of tangent. Line Section: Structures 1 to 240 Height Description (ft)Comments Allowance for Survey Errors”0.0 Height of travel surface above surveyed ground surface 1.0 Assumed snow and ice depth Height of object under line (reference height)14.0 Truck from NESC Adder for non-rigid part 1.5 NESC Adder for bare conductor 0.5 NESC Electrical Clearance 230 kV 4.6 NESC 2.5 +Voltage Adder Allowance for template and sagging errors!0.0 Additional Clearance 0.0 21.6 "The structures were spotted with no consideration given for the distance from the ground to the point the base of the tower is attached to the foundation.This has an approximate minimum of 0.5 feet for rock foundations,most of the towers have pile foundations where the approximate minimum additional clearance is 2.75 feet. -22- Table 7 SKIER GROUND CLEARANCE 138 kV (60 Hz) Design Conditions: Alternate Unbalanced Snow Alarm Level Line Section: Structures 1 to 240 Height Description (ft)Comments Allowance for Survey Errors”0.0 Height of travel surface above surveyed ground surface 5.0 Assumed snow depth Height of object under line (reference height)6.5 Skier™ Adder for non-rigid part 1.5 NESC Adder for bare conductor 0.5 NESC Electrical Clearance 230 kV 1.0 REA High Wind Clearance Allowance for template and sagging errors!0.0 Additional Clearance 0.0 14.5 *The structures were spotted with no consideration given for the distance from the ground to the point the base of the tower is attached to the foundation.This has an approximate minimum of 0.5 feet for rock foundations,most of the towers have pile foundations where the approximate minimum additional clearance is 2.75 feet. nt 6.5 feet is the height of the 99"percentile man with normal shoes. -23- A tension alarm level was then calculated for each tower.This was done using a computer program that took the horizontal tension with 1.75 inches of snow at 5 lb/ft?and calculated the length of the wire supported by each instrumented tower based on the plan-profile sheet stations and elevations.To the weight of this length of wire was added the weight of the insulators, hardware,dampers,and 1/2 the weight of the load cell.A normal load was also calculated in the same manner using the weight and horizontal tension for the bare wire (Figure 3). When an alarm occurs at these levels,it indicates that sufficient snow has accumulated on the wires that ground clearances may be impaired as the snow falls from some spans.It does not indicate that there is a problem.One caution:if during the storm,snow has fallen off the spans adjacent to an instrumented tower (a sudden reduction in load)and snow continues to accumu- late,the total accumulation may be greater in some spans than indicated by the insulator tensions.Figure 2 shows the load history for three insulators on the same tower of the Tyee line during a storm.This illustrates that snow falls off each phase conductor at different times during a storm and affects the total weight of snow accumulated. The second set of alarms is for insulator inclination.They were initially set at +5°to allow room for the insulators being clipped out of plumb and for the center inclinometer to be installed out of plumb.Some data was then recorded and the alarm values are currently set at +2° either side of the normal everyday inclination (Figure 4).This indicates a possibility of a single span loaded with 1.75 inches of snow four spans away or lesser amounts of snow closer to the instrumented tower. With 1.75 inches of snow in the span immediately adjacent to the tower,an angle of more than 6°would be expected.Thus if the angle is more than 2°and less than 6°,the clearances may be impaired and should be investigated.If the angle is greater than 6°,there is a high likelihood that clearances have been impaired. -24- 2000Ib1500Ib1000Ib0.50 in Ice - Road Phase Center Phase 0.25 in Ice 4 Field Phase r Bare = ||| 12/10/94 12/15/94 Tyee Structure 70-1 Vertical Load 2000Ib1500Ib1000IbFigure 2 InsulatorTension-IbsAlarm Load Calculated Normal Load [i seee eee een eeeeeneene ee eee ne eesOctoberNovemberDecember Tower 69 East Insulator Tension Figure 3 LongitudinalSwing-degfs)10|0|--10High Alarm Normal Angle | Low alarm AAAI AAAs MeeeOctoberNovember December Tower 69 West Insulator Inclination Figure 4 ieEs0ERco,REeeEEEcone,DESson,DEoe,MEREco,EEScomEScncDEoeEEceon,EEcnEEcreeEEoea|APPENDIX 1 EXCERPTS FROM THE NESC AND INTERPRETATIONS Appendix 1 EXCERPTS FROM THE NESC AND INTERPRETATIONS The National Electrical Safety Code establishes requirements for ground clearances.The following are excerpts from the Code and published interpretations of the code. The conditions under which the code clearances apply were clarified in an interpretation made February 18,1982 ([R304). "The basic clearances in Table 232-1 for the basic span lengths of Rule 232A apply only under the stated conditions.They are specifically stated in terms of 60°F and final sag conditions to aid in measurement.The values shown are large enough to allow for increased sag beyond the measurement conditions due to ice loading or 120°F conductor temperature operation.Whether the ice loading condition,or the 120°F conductor temperature loading condition determines the maximum sag will depend upon the individ- ual case.Where spans are longer than the basic lengths or maximum conductor operation temperature is higher than 120°F,other rules require additions to the basic clearances measured at the 60°F,final sag condition." The following code interpretation IR 270 indicates that the code leaves some situations to the discretion of the Owner of the facility.' "Request (June 25,80)IR 270 ',..currently designing a 345 kV line in the high mountain country where the snow cover can reach a depth of almost 15 feet.Since the National Electrical Safety Code,77th Edition,Rule 232,does not specify any special requirements for this condition,we would appreciate any recommendations on this clearance problem.' Interpretation (Sept 30,80) The code does not specifically address the question of clearances where snow accumulation in the vicinity of supply lines may be significant.Rules 200,210 and 211 do,however, provide some general requirements." 1 National Electrical Safety Code Committee,ANSI C2 National Electrical Safety Code Interpreta- tions,1978-1980 inclusive and interpretations prior to the 6th Edition,1961.Institute of Electrical and Electronics Engineers,Inc.,New York (1981),Page 77. 1-1 The following are excerpts from the 1977 Edition of the NESC'which was in effect at the time the above interpretation was made. "200.Purpose of Rules The purpose of these rules is the practical safeguarding of persons from hazards arising from the installation,operation or maintenance of overhead supply and communication lines and their associated equipment.They contain provisions considered necessary for the safety of employees and the public.They are not intended as a design specification or an instruction manual.Construction should be made in accordance with accepted good practice for the given local conditions in all particulars not specified in the rules. 210.Design and Construction All electric supply and communication lines and equipment shall be of suitable design and construction for the service and conditions under which they are to be operated. 211.Installation and Maintenance All electric supply and communications lines and equipment shall be installed and maintained so as to reduce hazards to life as far as is practical." The following are excerpts from the 1997 edition of the NESC?covering the same topics.Part 210 has been changed to "Referenced Sections"and Part 211 is no longer used. 010.Purpose The purpose of these rules is the practical safeguarding of persons during the installation, operation,or maintenance of overhead supply and communication lines and associated equipment. These rules contain the basic provisions that are considered necessary for the safety of employees and the public under the specified conditions.This code is not intended as a design specification or as an instruction manual. 012.Application C.For all particulars not specified in these rules,construction and maintenance should be done in accordance with accepted good practice for the given local conditions known at the time by those responsible for the construction or maintenance of the communication or supply lines and equipment. 200.Purpose The purpose of Part 2 of this code is the practical safeguarding of persons during the 1 Secretariat,Institute of Electrical and Electronics Engineers,Inc.and National Bureau of Standards.National Electrical Safety Code,1977 Edition.Institute of Electrical and Electronics Engineers,New York (1977)Pages 105 &106. 2 Secretariat,Institute of Electrical and Electronics Engineers,Inc.and American National Standards Institute.National Electrical Safety Code,1997 Edition,Institute of Electrical and Electronics Engineers,New York (1996)Pages 1 &59. 1-2 installation,operation,or maintenance of overhead supply and communication lines and associated equipment. The following quotations from Allen L.Clapp'indicate that the pedestrian reference heights, particularly 10 feet are based on the height of a person holding or carrying a common object in their hand. "For conductors of all types less than 300 volts to ground the height above pedestrian thoroughfares was increased from 10 feet to 12 feet in the 3rd Edition because an average person could,with an umbrella,reach wires having only a 10-foot clearance,as when a person raises his umbrella at arm's length above his head to avoid hitting that of another person when passing.This clearance applied only where footways or spaces were provided for pedestrians as a thoroughfare.An exception was made to the rule in case of signal wires of less than 150 volts to ground,where a 10-foot clearance was permitted." "...A Reference Height of 2.45 m (8 feet)was used with the applicable electrical and mechanical components to determine the clearance required of items that essentially produce a mechanical interference problem.A Reference Height of 3 m (10 feet)was used with the applicable mechanical and electrical components for open-supply conductors. This recognizes the expected relative differences in safety issues presented by someone carrying a ladder across a yard. "_,.A truck height of 4.3 m (14 feet)is the reference for vehicle areas.The height of a worker with hand tools was used for pedestrian areas." 1 Clapp,Allen L.,NESC Handbook,Fourth Edition.Institute of Electrical and Electronics Engineers, Inc.,The IEEE Standards Press New York (1996)Pages 191,218,&245. 1-3 APPENDIX 2 ALARM LEVELSSeesOepmseeperme>peesOeeresWeesOPpeneWOeseeeOPeeOeGPpeesOYeesOeeeOFpeesWOpeesOOesOSeeO ICE9.BAS Version 1,5-12-92 9-22-1996 15:26:27 lden Valley Electric Association »kV Istring oaded Span in Center of Tangent "ce or Wet Snow,density:5.00 1lb/ft*3 aadial Ice or Wet Snow:1.75 in Number of Subconductors:2 Area:0.8010 in*2 liameter:1.1650 in are Wt:1.0760 lb/ft Iced Wt:1.6325 lb/ft 'TS:25,900.lb fodulus of Elasticity of Wire: Insulator Length Multiplyer for Iteration Limit: msulator Type:I String Length:11.00 ft,weight:2 ipan Effective Elev No Span Span Diff 1 1,260 1,260.00 0 2 1,260 1,260.00 0 3 1,260 1,260.00 0 _4 1,260 1,260.00 0ys1,260 1,260.00 0 S)1,260 1,260.00 0 7 1,260 1,260.00 0 8 1,260 1,260.00 0 9 1,260 1,260.00 0 10 1,260 1,260.00 0 tesults for 3 Spans Tower Insulator Total jpan Movement Movement Movement No (£t)(fc)(ft) 1 0.1927 0.8983 1.0910 2 0.0000 0.0000 0.0003 Results for 5 Spans Tower Insulator Total Span Movement Movement Movement No (ft)(ft)(ft) 1 0.2451 1.1404 1.3855 2 0.0947 0.5522 0.6469 3 0.0000 0.0000 0.0002 J sults for 7 Spans Tower Insulator Total Span Movement Movement MovementNo(ft)(ft)(ft) 9,307,448 psi 30 1b Unstressed Unit Length Weight 1,262.8961 1.6325 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 1,262.8961 1.0760 Horizontal Sag Tension (ft)(ft) 53.745 6,021.50 36.437 5,876.98 Horizontal Sag Tension (ft)(ft) 56.092 5,765.39 38.349 5,581.54 38.839 5,510.51 Horizontal Sag Tension (ft)(ft) 2.00 )rn,|i! Sag w/out Movement 44 42 -287 42. 42. 42. 42. 42. 42. 42. -180 42. 180 180 180 180 180 180 180 180 Tower Stiffness H 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 7,327 5,070 5,070 5,070 5,070 5,070 5,070 5,070 5,070 5,070 Tension Diff (1b) 0 145 Tension Diff (1b) 0 184 71 Tension Diff (lb) 1 2 ¥& .esults for No 0.2643 1.2285 0.1297 0.7554 0.0600 0.3503 0.0000 0.0000 9 Spans Tower Insulator pan Movement Movement (ft)(ft) 0.2720 1.2640 0.1439 0.8379 0.0846 0.4936 0.0391 0.2280 0.0000 0.0000WPWNHe "esults for 11 Spans No Tower Insulator Span Movement Movement (ft)(ft) 0.2753 1.2789 0.1499 0.8724 0.0950 0.5538 0.0556 0.3246 0.0256 0.1493 0.0000 0.0000 "AUPWeResults for 13 Spans No NSNUPWNPRResults for 1.4927 0.8851 0.4103 -0.0008 Total Movement (ft) -5361 -9818 -5782 .2671 0005joexoweok.Total Movement (ft) -5542 .0223 -6488 .3803 -1749 -0.0008oOoOOrRF Total Movement (ft) 1.5620 1.0398 0.6792 0.4292 0.2511 0.1159 0.0007 Insulator Total Span Movement Movement Movement No Tower Insulator Span Movement Movement (ft)(ft) 0.2767 1.2853 0.1525 0.8873 0.0995 0.5798 0.0628 0.3664 0.0367 0.2144 0.0169 0.0989 0.0000 0.0000 15 Spans Tower (ft)(ft) 0.2773 1.2880 0.1536 0.8935 0.1013 0.5907 0.0658 0.3840 0.0414 0.2418 0.0242 0.1411 0.0111 0.0649 0.0000 0.0000 (ft) -5652 -0471 -6921 -4499 2833 .1652 .0760 0001OOOO0O0COFRF 56. 39. 39. 40. 927 046 745 077 Sag (ft) 57. -328 40. 40. 40. 39 263 116 594 819 Sag (ft) 57. 39. 40. 40. 41. 41. 402 445 272 814 138 290 Sag (£t) 57. 39. 40. 40. 41. 41. 41. 462 496 339 909 278 496 597 Sag (ft) 57 39. 40. 40. 41. 4l. 41. 41. -487 517 368 949 336 583 729 796 5,679.27 5,481.05 5,383.77 5,338.74 Horizontal Tension (ft) 5,645.45 5,441.41 5,333.45 5,269.97 5,240.67 Horizontal Tension (ft) 5,631.49 5,425.02 5,312.59 5,241.34 5,199.62 5,180.43 -Horizontal Tension (ft) 5,625.50 5,417.98 5,303.61 5,229.02 5,181.91 5,154.37 5,141.66 Horizontal Tension (ft) 5,623.01 5,415.05 5,299.87 5,223.87 5,174.50 5,143.42 5,125.30 5,116.96 Tension Diff (1b) 0 206 112 71 42 19 Tension Diff (1b) .0 208 114 75 47 28 13 Tension Diff (1b) 0 208 115 76 49 31 18 8 Results for Fd WOWDTINMPWDbPTower (ft) -2775 .1540 -1021 -0671 -0435 .0273 .0159 .0073 -0000ooo0o00000 'esults for jpan Movement Movement Movement No SNOWPWNBP3=oOo.Tower (ft) 0.2776 0.1543 0.1025 -0677 -0444 -0287 -0180 -0105 -0049 0.0000ooo0o00 17 Spans Insulator Total (ft) 1.2891 0.8962 0.5954 0.3916 0.2537 0.1594 0.0929 0.0427 0.0000 19 Spans n Movement Movement Movement (ft) -5667 -0503 -6976 -4587 -2971 -1867 -1088 -0500 -0001OOO0000FRF Insulator Total (£t) 1.2897 0.8975 0.5975 0.3950 0.2590 0.1674 0.1052 0.0614 0.0286 0.0000 (ft) 1.5673 1.0517 0.7000 0.4627 0.3034 0.1961 0.1232 0.0720 0.0335 0.0009 Sag (ft) 57. 39. 498 527 40..380 40. 41. 41. 41. 41. 41. 967 362 622 786 883 928 Sag (ft) 57. 39. 40. 40. 41. 41. 41. 41. 41. 42. 503 530 386 974 373 638 812 922 986 016 Horizontal Tension (ft) 5,621. 5,413. -235,298 5,221. .275,171 5,138. 5,118. 5,106. 5,100. Horizontal 90 76 62 67 19 26 78 Tension (ft) 5,621. 5,413. 5,297. 5,220. 5,169. 5,136. 5,115. 5,101. 5,093. 5,089. 43 20 Sl 63 85 57 05 53 64 96 Tension Diff (1b) 0 208 116 77 51 33 22 14 8 4 rNrt|an|ryrytrTryrvrNryryryryrTrTrTrrAPPENDIX 3 ICE/SNOW MELT OPTION LITERATURE REVIEW Appendix 3 ICE/SNOW MELT OPTION LITERATURE REVIEW Asai and Wakaham (1990)report using rings and antirotation devices to prevent the buildup of snow.They also mention in passing shorting lines to ground to melt the snow or prevent the buildup of snow. Clem (1930)discusses early tests on small conductors of the current required to prevent the accumulation of ice and to melt ice.He then gives formulas for the current required. Corey et al.(1952)This 1952 paper indicates that the New England Electric System had problems with ice accumulation since 1916.At the time the paper was written,New England Electric System had provision for applying melting currents to 450 miles of 69-kV line,and 50 miles of lower voltage line.A heating current providing resistive heating of 11 watts per foot is used.Equipment and scheduling of melting is also discussed. DeSieno et al.(1956),Bartlett et al.(1952),Langdon &Marquis (1939)and Sporn (1939) all discuss the experience of American Gas and Electric with detecting and melting ice from their system.AG&E developed a method of detecting ice buildup using the attenuation of powerline carrier.In these papers several examples of ice melting at full line voltages of 132 kV are given.Tests were performed by AG&E in conjunction with Alcoa at Massena New York to find the current needed to melt ice from 1,269 kcmil conductor.The tests showed that 1200 amps would remove 1/2 inch of ice in 100 minutes and 1600 amps would remove it in 55 minutes. This conductor was to be used on planned 330 kV lines which would have ice melted at 132 kV. Dumas and Sakamoto (1986)report that Hokkaido Electric in Japan has successfully prevented wet snow accumulations by increasing the load flow in a line.For example,one circuit of a double circuit line is switched out,doubling the load in the remaining circuit.The switched out line is then energized at a lower voltage and short circuited. They report an instance in which loads of up to 8.4 lb/ft (12.6 kg/m)occurred.They also report that the accumulation would have been prevented with a "Joule effect"of 40 w/m.This translates to approximately 1720 amps in the intertie's two bundle rail conductor and 660 amps in the Willow Lines single Dove Conductor.(Rail's catalog current rating is 980 amps per wire or 1960 amps for the Intertie's two conductor bundle and Dove's is 710 amps).The power transfer required for this heating is 410 megawatts for the 2 bundle rail and 158 MW for the Dove. Hokkaido electric is reported to be setting up a program for predicting the occurrence of severe snow events so that preventative line heating can be performed. Table 3-1 shows Dumas and Sakamoto's theoretical relationship between snowfall intensity, Joule heating of the line and the amount of snow accumulating on a line (the translation to English units is ours).Note that the snowfall takes place above freezing and occurs during very 3-1 high winds.At present,we believe the snow problems on the Intertie have been due to lighter, dryer snows falling at temperatures below freezing with very low wind speeds. Table 3-1 SNOWFALL INTENSITY AND JOULE EFFECT (After Dumas and Sakamoto) Meteorological Conditions Local Wind Air Snowfall Snow Overloads (1b/ft) Time Speed Temp _Intensity Joule Effect (watts/ft) hr mi/hr °F in/hr 0.0 3.0 6.1 12.2 24 33.6 33.8 0.1 10.2 0.0 0.0 0.0 3 31.3 33.8 0.2 0.7 0.0 0.0 0.0 6 24.6 33.8 0.2 1.7 0.5 0.0 0.0 9 28.0 32.9 0.4 4.2 2.1 0.8 0.0 12 41.4 32.9 0.6 8.4 5.5 3.3 0.0 15 47.0 32.9 0.6 13.9 9.9 7.0 0.0 18 52.6 32.9 0.4 19.2 14.6 10.9 0.0 21 52.6 33.8 0.3 23.2 18.1 13.9 0.0 24 47.4 33.8 0.1 25.3 19.9 16.0 0.0 3 35.8 32.9 0.1 26.2 20.7 16.2 0.0 Electrical World (1917)this is short piece about currents required to prevent ice accumulation being in the range of 1 amp per 1,000 cmil with substantially more required to melt already accumulated ice. Gayet (1986)reports on wind tunnel studies on the use of Joule heating to prevent in-cloud ice formation.The wind tunnel results are compared to calculations of the heat balance required to keep the conductor surface at a temperature greater than freezing which will in turn keep impinging water droplets from freezing on the wire. The currents necessary to keep a 0.62-inch (1.57 cm)conductor and a 1.22-inch (3.10 cm) conductor from icing are plotted as a function of wind speed and air temperature.For low wind speeds they are on the order of 250 to 350 amps for the smaller conductor and 600 to 800 amps for the larger conductor.The currents rise to 600 to 1000 and 1400 to 2100 amps respectively with wind speeds of 45 mph. Goia (1993)reports that in Romania icing detectors are used to determine when to apply preventative heating of the lines.This is done by circulating VARS or by short circuiting.He gives some formulas for the current required for prevention and for melting but we can not get consistent and reasonable results using them. 3-2 Kalinin and Soldatov (1990)discuss the theoretical aspects of using phase shifting transformers to cause circulating currents to heat the wires while allowing continued use of lines to serve loads. Larcombe et al.(1986)discuss a theoretical analytical solution to ice shedding induced by Joule heating of the conductor.This paper is a very dense mathematical exercise taking into account the heat flow through the ice layer and the latent heat of fusion of water.It appears to have similarities to the solution of freeze and thaw depths in soil.(It may be possible to take a similar approach using a two dimensional finite element heat transfer program,for example the University of Fairbank's Koxgrid.) Oehlwein (1953)discusses circulating VARs to increase the line current of operating lines to prevent or remove ice. Seevers (1983)gives an example of calculation of current and time required to melt ice from a distribution line based on melting through the section of ice directly above the wire using the heat of fusion of ice.He provides a table based on this method showing that 644 amps is required for ice melting of 795 kcmil ACSR. Sener (1922)reports the results of tests to determine the current required to prevent ice accumulation on small conductors used for electric trolley lines. Shealy et al.(1952)and Thomas (1917).These two papers discuss Pennsylvania Water and Power Company's experience with ice accumulations on their transmission lines from when the first line was built in 1910 up until 1952.In 1952 they employed melting on 400 miles of 66, 132 and 220 kV lines including dedicated busses in substations for ice melting.At the time of writing,PP&W used "sleet"forecasting,line patrols to determine when melting was needed and applying melting currents to maintain reliable service during ice storms.Shealy also gives examples of the effects of various ways that PW&P prevented ice and melted ice from lines over the years and the influence of their experience on the configuration of new towers.Thomas indicates that utilities have had problems with unbalanced ice and snow loads since early in this century. Shenglin,Xingliang and Qifa (1990)report heavy vertical snow loads,galloping problems and problems with ice covered insulators flashing in China.Their paper also has factors relating to the amount of buildup.A description of ice melting using a low curie point magnetic material (an alloy of iron,nickel,chromium,silicon and manganese sheathed in a copper aluminum alloy)is also included. Shenglin and Zhendou (1990)discuss methods of connecting an auto transformer into the subconductors of a phase which are insulated from one another to produce circulating currents that melt the ice while normal power flow is maintained.Their system also includes provision for melting the ice on the shield wires.An icing detector is used to monitor when ice is present and when it has been melted off. The Chinese have also built ACSR with the core wire insulated from the aluminum wires.The aluminum wires are used in normal circumstances for carrying the current.During icing,the 3-3 load is automatically switched to the core wire which has a much higher resistance and increases the heating to melt the ice.The durability of the insulating layer between the core and the aluminum is;however,a big concern. Wilson (1993)&Tymofichuk (1986)These two references discuss Manitoba Hydro's experi- ence dealing with ice and snow loads on their transmission and distribution lines.Wilson's manual "Ice Storm Management of Overhead Lines"is the most comprehensive source we found for methods of dealing with snow and ice loads.Tymofichucks 1986 paper discusses the April 27,1984 ice storm that caused extensive problems on Manitoba Hydro's system.It also has a sections discussing "Ice melting by short circuit current"and using ice rolling as an ice removal technique.Ice rolling places a roller over the conductor that is pulled along by a man or a vehicle. Manitoba Hydro started developing ice melting techniques in the mid 1960's.Ice melting is also mentioned as having been used in North Dakota.Manitoba Hydro developed charts relating conductor size,ice loading,wind,ambient temperature and the required short circuit current to melt ice.Ice melting busses were installed at several locations on their system.Tymofichuk includes a one line diagram of an ice melting bus at Manitoba Hydro's Brandon station.He indicates that they have made theoretical studies of a low voltage direct current ice melter.For subtransmission lines,a DC current of 500 amps is reported adequate.With a line resistance of .22 ohms/km (this is close to Partridge 266.8 kcmil ACSR 26/7)a DC voltage of 20 kV will melt ice from 96 km of conductor (out and back using two phases).This works out to 15.9 watts/ft (52 w/m)compared to the snow prevention power of 12.2 watts per foot reported by the Japanese.He also reports Manitoba Hydro has 7,000 kM of line that can have ice melting applied to it. Wyss (1933)gives the results of tests to determine the time and current required to melt ice on small conductors,No.0 aluminum and No.3 to No.0 copper. Yamamoto,Naito,Ando and Samajima (1990)report on wrapping the conductor with a low curie point wire to perform ice melting.The wire generates heat by hysteresis loss and eddy current loss driven by the alternating magnetic field around the conductor.The material has a low curie point,meaning that its magnetic properties are dependent on temperature.As the temperature of the wire rises,the heating is reduced.The low curie point wire can be machine wound on the conductors.Outdoor tests indicate that this method can prevent accumulation of snow on the line,depending on the snowfall rate,the current carried in the line and the density of the windings. Yamaoka,Ohtake and Wakahama (1986)report observations of rime icing with some glaze on Hokkaido Island (near Sapporo).Approximately 6 kVA at 6 kV is required to melt snow on a 66 kV line between Tishikaga and Akubetsu. They also report wind tunnel experiments to reproduce icing in the laboratory using a 651.3 kcmil (330 mm?)conductor with current flow and a 315.8 kcmil (160 mm?)conductor and a 5 mm diameter copper wire without current flow to measure ice accumulation.Ice accumulated to a smaller thickness on the 651.3 kcmil conductor loaded at 900 amps than on the other two wires with all of them exposed to a 5 meter/sec wind at -5°C.With a current of 1020 amps, 3-4 no icing occurred.They concluded the temperature on the windward side of the wire has to be above -2.5°C to prevent icing. Yamaoka et al.are developing a patented system wherein the subconductors of a multiple conductor bundle are insulated from one another with dielectric spacers and direct current is passed through the subconductors of the conductor bundle to prevent or melt ice while the line remains in operation. iIIee,Ine,DEceREIStee,EEEce,ESre,ESee,ESoeDEcoe,EEcooeoecoeom|APPENDIX 4 CORRESPONDENCE COPIES /; IDRYDEN ¢LaRue IINc. CONSULTING ENGINEERS 6436 Homer Orive,Anchorage,AK 99518 Mailing Address:P.O.BOX 111008,ANCHORAGE,AK 99511-1008 (907)349-6653 *FAX 522-2534 March 21,1996 Mr.Jim Hall MATANUSKA ELECTRIC ASSN.,INC. P.O.Box 2929 Palmer,Alaska 99645 Reference:Anchorage -Fairbanks Intertie Options for Mitigating the Effects of Unbalanced Snew Loads Revised Budget Cost Estimate for Snow/Ice Melting In our letter of February 9,1996 we gave you ballpark cost esti- mates for the different options for mitigating the effects of unbalanced snow loads.At that time,we did not have sufficient information to estimate the cost of snow/ice melting to the same accuracy as the other estimates.ABB has provided us with a budgetary quote for the equipment for a DC ice melting system (see attached).Based on that equipment,we estimate the total installed cost at $2,830,000 (see attached breakdown).Table 1 shows a comparison of the alternatives with the revised ice/snow melting estimate. Table 1 Ball Park Cost Estimates (construction only) Line Monitoring (4 locations)$440,000 Line Monitoring (23 locations)1,300,000 Ice Melting 2,830,000 Convert to Inverted V's 3,300,000 Inset Prop Structures 7,100,000 Inset H-frames 17,000,000 ABB's equipment is based on a requirement to supply 2,500 amps at5,700 to 6,200 volts DC through a resistance of 52 miles (26milesoutandback)of conductor at 0.04379 ohms/mile (.08759 per subconductor,2 subconductors in parallel @ 00°C,higher at higher temperatures).The power requirement is 14.4 MW for 30 minutestolhour.This would have to be done twice each direction from Stevens substation to melt all three phases.It is about $2,300 in power costs for 1 hour melts at $.04/kW-hr. The system includes thyristor controlled rectifier units whichallowtheicemeltingloadtobebroughtontothesystemgradual- ly. Transmission,Distribution,Substations,System Planning Matanuska Elect.ic Assn.,Inc.March 21,1996 Mr.Jim Hall Page 2 Pros and Cons Some advantages are: ¢Relatively inexpensive @ The entire section of line can be cleared of snow and ice Some disadvantages are: #Ground clearance may be temporarily impaired during the snow removal due to differences in when spans are cleared.This would depend on how much snow built up before the melting begins.Beginning melting before too much snow builds up should prevent this. #Ice melting is most likely to be required when snow and ice are also causing problems on distribution system that demand attention. @¢Access for switching at the North end of Chunilna (Clear) Creek is difficult. @ The high currents may cause damage to the line if there are any high resistance connections;however,periodic infrared scans during melting could be used to locate and repair hot spots. ¢Switching sequence to connect the ice melting system is critical --a mistake could damage the ice melting system and/or cause problems on the AC system. This information and the information in our letter of February 9 will be incorporated into our June 1995 report to produce a final report about the options for mitigating unbalanced snow loads. If you have any questions,please give me a call. DRYDEN &LaRUE, ABP:jf\ic\estimate.sno cc:Steve Haagenson/GVEAVincentMottola/FMUS Larry Hembree/ML&PJimWilson/CEA Sam Matthews/HEA Stan Sieczkowski/AEA Devben ¢LARUE Inc.CONSULTING /ENGINEERS 6436 Homer Drive,Anchorage,AK 99518 Mailing Address:P.O.BOX 111008,ANCHORAGE,AK 99511-1008 Feb ruary 9,1996 (907)349-6653 ¢FAX 522-2534 Mr.Jim Hall INTERTIE OPERATING COMMITTEE c/o Matanuska Electric Assn.,Inc. P.O.Box 2929 Palmer,Alaska 99645 Reference:Anchorage -Fairbanks Intertie Options for Mitigating the Effects of Unbalanced Snow Loads Preliminary Cost Estimates This letter is to update you and the committee on our progresswiththecostestimatesformitigatingtheeffectsofunbalanced snow loads.We have completed,but still neéd to review and check the estimates.The estimate for ice/snow melting is our bestguessoftherangeatthispoint(see the discussion below). Ball Park Cost Estimates Table 1 shows our ball park estimated costs for construction of the different alternatives.The costs are for construction onlyanddonotincludethecostsofengineering,permitting,construc-tion management,inspection,owners overhead and administrative costs,etc.The cost for improvements is for the line section from Douglas Substation near Willow to Chunilna Creek,a distance of about 52 miles. Table 1 Ball Park Cost Estimates (Construction Only) Line Monitoring (4 locations)$§$440,000 Line Monitoring (23 locations)1,300,000 Convert to Inverted V's 3,300,000 Inset Prop Structures 7,100,000IceMelting5,000,000 to 10,000,000+? Inset H-frames 17,000,000 Pros and Cons Line Monitoring -inclinometers and load cells would be installed on the insulator strings of either 4 or 23 towers to monitor the weight of snow buildup and insulator swing.The instruments would communicate via cellular phone.The instruments could be interro- gated to look at conditions during certain windows when the phone is powered up.They would also call in to sound an alarm when the insulator swing exceeds a preset level. Transmission,Distribution,Substations,System Planning Intertie Operating Committee February 9,1996Mr.Jim Hall Page 3 line at distribution voltages into bolted faults 26 miles away(the distance from Douglas to Stevens and Stevens to Chunilna Creek).There is not sufficient fault current available at Doug- las without capacitive compensation.Shunt capacitors were inves- tigated and also did not work.Series capacitors provide enough compensation to get the required currents,however disturbances during energization are far outside the bounds that the low side equipment can withstand.Disturbances on the 138 kV system at Douglas and Teeland are also outside reasonable bounds.We have concluded that ice/snow melting using conventional AC equipment is probably not feasible.We are discussing the possibility of using DC with ABB,but do not yet have any detailed information. Inset Towers -New tubular steel H-frame structures would be inset in every span.The towers would use the same insulators and hard- ware as the existing structures (i.e.,would be insulated at 345- kV).The H-frames would be set in sections in between the exist- ing phase and shield wires. Pros 'Cons Increases ground clearance Most expensive the most under unbal-Some increased maintenance anced loads,should cost "cure the problem"Permitting and environmen- except in the most tal issues may need to unusual circumstances be addressed No operational interven- tion required In summary,the solutions to the problem range from essentiallyoperationalinnature(load monitoring)through insetting towersthatareveryexpensivebutwouldnormallynotrequireanyopera- tional action. We expect to finalize the cost estimates and schedules by the endofnextweek.If you have any questions,please give us a call. DRYDEN &LaRUE,INC. Lebie. Alan B.Peabody,lP.E. ABP:jf£\icsnoi\estimate.icn cc:Steve Haagenson\GVEA Vincent Mottola\FMUS Larry Hembree\ML&P Jim Wilson\CEA Sam Matthews\HEA Stan Sieczkowski\AEA Intertie Operatiny Committee February 9,1996Mr.Jim Hall Page 2 Pros Cons Least Expensive Does not increase groundProvidesInformationforclearancebyitselffuturedesignsRequiresanoutageand Uses standard hardware line crew to remove snow &ice from low spans Convert to Inverted V's -the existing 345 kV insulator strings would be converted to inverted V-strings.The yokes would be removed and the guys would be attached directly to the anchor piles.The guys would be pretensioned to reduce tower movement under unbalanced longitudinal loads.Shield wire peaks would be reversed to increase clearance between the phase conductors and the shield wires. Pros Cons Increases ground clearance May not eliminate outages under unbalanced loads and ground clearance Relatively inexpensive problems Increases longitudinal loads on crossarm Inset Prop Structures -Three single pole wood structures with insulated sections of bus would be inset at approximately mid span to catch the wire when it sags below normal clearances.A diffi- culty with this concept is that the height of the prop is limited by maintaining some clearance to the line under normal operation but having it high enough to do some good when unbalanced loads occur. Pros Cons Increases ground clearance May not completely elimi- under unbalanced loads nate outages &ground clearance problems Unproven concept Looks strange Abrasion damage to wire must be addressed Permitting and environmen- tal issues may need to be addressed Ice Melting -Equipment would be installed at Stevens SubstationnearTalkeetnatoenergizethelineatlowvoltageandhighcur- rent to generate enough heat to melt the snow/ice off the wires.Manitoba Hydro's manual "Ice Storm Management of Overhead Lines"indicates currents on the order of 2500 amps per phase for 30 minutes to an hour are needed to melt glaze ice. With the help of Steve Haagenson and Doug Ritter at GVEA we lookedatinstallingatransformeratStevenstoallowenergizingthe ABB FAX MESSAGE SERIAL SNC960319.0 TO:Al Peabody,Civil Engineer DATE:Mar.19,1996 Cc: Cc: FAX:907-522-2534 PAGES:2 +1 FROM:Richard Reed ABB Power T&D Company,Inc ADDRESS:1460 Livingston Ave. North Brunswick,N.J.08902 PHONE:908-932-6339 FAX:908-932-6321 SUBJECT:Douglas Substation Willow Alaska FILE:4 Id Requcst......cccscrsroccssssersersrcassrareerstsrerossncses DC Power Supply for Transmission Lines In reference to our February,96 telephone discussion about the icing of various transmission lines in your cold climate.We recieved your March 9 fax of engineering data needed to define the DC supply components and have prepared a bill of material for this small substation addition.We offer:. A.1 ea Circuit switcher,138KV,1200 amperes per your fax 2ea Rectifier Transformers,ANSI standard circuit no.25/26, 138K V/5.2KV ,60 HZ,Approximately 9 MVA each one. 2ea Thyristor controlled rectifier units,water cooled,8 MW each one with output of 7,000 volts DC. lea Disconnect Switch,1OK V-DC,3000a continuous,motor operated,non-load break operation.lea Prefabricated control house for the rectifiers,disconnect switch,and aux power.lea Lot of steel for circuit switcher and PT and line termination. MAR 19 °96 08:35 988 422 2006 PAGE.@1 Price:Budget $1,834,300.to purchase this equipment and engineer a complete set of drawings and documentation.Time needed to complete delivery to Alaska is 18 months after receipt of order.ABB Company Conditions of Sale,50-000,dated January 1,1990 apply here. I am looking foreward to our continued definition of the equipment for this transmission line as you finalize the design and your budget.Please call me as needed and realise that we are most pleased to supply the equipment. As always,please call if we can be of further assistance. Rich Reed,Project Manager MAR 19 °96 @8:35 988 422 2006 PAGE.82 FADDODASEABROWNBOVERI January 1,1990 New Information Mailed to:E,D,C/50-000 ABB Power T&D Company inc. 630 Sentry Park Blue Bell,PA 19422 Reler to specilic product line supplementary documenis for exceplions !o or variations from conditlons herein. Condition:of Sale Form 50-000 Paye } ABB Power T&D Company Inc.Conditions of Sale )1.Applicable Terms and Conditions Unless differant or additional larms and condi- tions are staled or relarred to in Ihe ABB Power T&D Company Inc.(hereinafter relarred to a¢ABB)proposal,in which event such dif-ferent or additonal terms and conditions shall be exclusive as to the particular subject cov- ered,the terms and conditions sialed below apply,and such terms and conditions supersede any prior or contemporaneous agreements or correspondence between the parties, ABB hereby gives nolice of its objeclion to anydierentofadditionaltermsandcondilions. This cale is expressty conditional on Pur- chasers'assent lo the lerms and condilions stated below,If not previously given,Pur- chasers'acceptance of product ls conclusive as to thig assent. 2.Quotations Each quolalion Is valid for 30 days from its date unless otherwise slaled In the quotation. 3.Prices Prices are subject to change withoul nolice.Unless otherwise specified prices will be the prices In effect al the time of shipment by ABB and will Include freight prepaid and allowed fothefirstdestinationinthecontinental!Uniled States.In the event of a price ,the ettective date of the change will be ihe daleshownonthenewpriceordiscountsheets. However,where a price change Is made by let-ter of telegram,the effective date may be given as part of the announcement. Reler to individual user discount sheels for specifics. 4.Taxes The price does not include any Federal,stale or local property,license,privilege,sales,use.©Xcise,gross receipts or other like laxes whichMaynoworhereatterbeapplicable.PaymentbyABBofanysuchtaxesshallbefor!account of the Purchaser. 5.Terma of Payment 5.4.Payment terms are net 30 days from dale of invoice, 5.B.If,in the judgment of ABB the financial condition of Purchaser at any ume prier to delivery does not justily the lerms of pay- ment specified,hen ABB may require payment in advance or cancel any oul-Standing order,whereupon ABE shall be MAR 19 °96 88:36 entiled lo receive reasonable cancellation charges.If delivery is delayed by Pur- chaser,payment shall become due on the date ABB Ie prapared to make delivary.Dalays in delivery or non-contormities in any installments shalt nol retieve Pur- chaser of Its obligation lo accept and payforramaininginslallments. 6.C.If Payments are not made when due,Pur- chaser chall pay,in addition to the over- due payment,a late charge equal to the lesser of 1'4%per month or the highest!applicable rale allowed by law on all such overdue amounts. 6.Dollvery Unless otherwise specilied,all products are shipped F.O.B.point of shipment,regardiess oftransporlationcostsbeing"allowed,”"prepaxi”or "collect.” 6.A.F.0.B.+Destination -Fri/Ppd.and Allowed:When the ABB quotation calls for delivery F.0.8.destination,ABS will deliver F.O.B.acceasible common carrier poini near- oat first Gestinalion,freight prepaid and included in the price and 2%will be added to the net price. 6.8.Carlage (Store Door Dellvery):Trans- portation charges incurred from the nearest!accessible common carrier point to final desti-nation or to shipside (in case of shipment to U.S.Possessions)are the responsibility of the Purchaser unlogs the common carrer furnishes store door delivery al no exva chargo. 6.C.Method of Shipment:Shipping dates are approximate and are based on receipt of com- plete information with the order.If drawing approval ls requwed,drawings must be felurned on schedule fo maintain shipping dale. ABS will delermine the point of origin of ship-ment,the method of tranzportalion,and the rouling of shipment.Purchasers requiring ship- mant by @ method or routing other than that of ABB selection will be billed any excess or pre-nmwum In transportation charges.For example,in the event the Purchaser requests air chip- ment,ABB will absord an amount equal to the charges of the normaily selacted cormmon car- fer.It lhe actual transportation charges on these shipments are less than such common carrier charges,then no allowance will be made lor the difference.In no event will ABB 988 42>SAAR be responsible for demurrage or detention charges. Any charges for special services,including,but not limiled to,special Irain,lighierage.or con- siruction,or repair of transportation lacilllies will be paid or reimbursed by the Purchaser. 6.D,Purchaser Pick-Up:No allowance will be made in heu of transportation if the Purchaser accepls Shipment at the factory,or the ware- house or freight slation. 6.E.Shipment Damage:Excep!in the eventofF.0.B.destination shipments,ASB will not participate in any seitlement of claims for con- cealad of other shipmen!damage.When ship-Tent has been made on an F.O.B.destination basis,the Purchaser must unpack Immediately and,if damage is discovered,must: 1.Not move the product from ihe point of examination. 2.Retain shipping conlainer and packing material. 3.Notify the carrier of any apparent damage inwritingoncarrier's delivery receipt andrequesithecarriertomakeaninspection. 4.Nolily the ABB location trom which ship- ment originated wilhin 72 hours of delivery. 5.Send ABB a copy of the carrier's inspection report. 6.F.inspection and Acceptance:Purchaserhasareasonabletimeafterreceiptoflheprod- uct fo Inspect and reject or accept the product. in any event acceptance will be deemed fo have occurred no later than 30 days after shipment. 7.Force MajeureABBshailnolbeliable for failure to perform or lor delay in performance due to,any causebeyonditsreasonablecontrol,or fire,Nood,stnke of other labor diflioulty,act of God,act of governmentia)authorily or of the Purchaser, fot,embargo,fuel or energy shoriage,carshoriage,faulty castings of forgings,wrecks ordelayinWaneportalion,or inability to oblainnecessarylabor,materials of manulacturingfacilitiestromusualsources.In the event of delay in performance due to any such cause.ihe dale of delivery or time for completion willbeoxlendedbyaperiodoftimereasonablynecessarytoovercometheelfectofsuchdelay. PARE Az REFERENCES ul ASpeeOepoepermspesOOpesGPresepeeOOeerWOeesOepesWOeseeeeeeSSDeesOeeeae bu REFERENCES General Clapp,Allen L.(1996)NESC Handbook,Fourth Edition.Institute of Electrical and Electronics Engineers,Inc.,The IEEE Standards Press,New York Dryden &LaRue (1992).Draft Investigation of Effects of Unbalanced Snow Loads _on the Anchorage-Fairbanks Intertie.Dryden &LaRue,Anchorage,AK. LaRue,D.S.(1990).Letter to Remy Williams re:"Design Practice for Ground Clearances under Unbalanced Span Loads."Dryden and LaRue,Anchorage,AK.January 8,1990. National Electrical Safety Code Committee,ANSI C2 (1981)National Electrical Safety Code Interpretations,1978-1980 inclusive and interpretations prior to the 6th Edition,1961.Institute of Electrical and Electronics Engineers,Inc.,New York Peabody,A.B.(1996a).Letter to Jim Hall re:"Preliminary Cost Estimates."Dryden &LaRue, Anchorage,AK.February 9,1996. Peabody,A.B.(1996b).Letter to Jim Hall re:"Revised Budget Cost:Estimate for Snow/IceMelting".Dryden &LaRue,Anchorage,AK.March 21,1996. Peabody,A.B.(1989).Letter to Remy Williams re:"Ground Clearances at Caswell Lakes Road and Hidden Hills Road."Dryden and LaRue,Anchorage,AK.November 1,1989. Marion,W &Wilcox,S.(1994)Solar Radiation Data Manual for Flat Plate and Concentrating Collectors.National Renewable Energy Laboratory,Golden,Colorado. Reed,R.(1996).Fax to Al Peabody re:"DC Power Supply for Transmission Lines",Dryden and LaRue,Anchorage,AK.March 19,1996. Ritter,D.(1996).Letter to Al Peabody re:"Anchorage to Fairbanks Electrical Deicing Feasibility"Dryden and LaRue,Anchorage,AK.February 2,1996. Richmond,M.C.(1995).Letter to Alan B.Peabody re:"Anchorage -Fairbanks Intertie Ice/Snow Load Investigation"Dryden and LaRue,Anchorage,AK.May 12,1995. Secretariat,Institute of Electrical and Electronics Engineers,Inc.and National Bureau of Standards.(1977)National Electrical Safety Code,1977 Edition.Institute of Electrical and Electronics Engineers,New York Secretariat,Institute of Electrical and Electronics Engineers,Inc.and American National Standards Institute.(1996)National Electrical Safety Code,1997 Edition.Institute of Electrical and Electronics Engineers,New York. White,H.B.(1991a).Letter to Stanley E.Sieczkowski re:"Wet Snow Problems on the Anchorage to Fairbanks Intertie."January 31,1991. White,H.B.(1991b).Letter to Stanley E.Sieczkowski re:"Second Report on Problems on A/F Intertie."Hudson,Quebec.February 18,1991. Snow Removal and Snow Prevention References (Cited or Reviewed) Asai,S.,Mayumi,A.and Wakaham,G.(1990)."Improvement of Countermeasures for Snow Accretion,”Proceedings,Fifth International Workshop on the Atmospheric Icing of Structures, Tokyo,Japan,pp B7-2-(1 to 5). Bartlett,S.C.,Imburgia,C.A.and McDaniel,G.H.(1952)."Sleet Melting on the American Gas and Electric System,"Transactions of the AIEE Vol.71 Pt 3,August 1952 pp 704-709. Clem,J.E.(1930).Currents Required to Remove Conductor "Sleet,"'Electrical World December 6,1930 p1053-1056. Corey,C.P.,Selfirdge,H.R.and Tomlinson,H.R.(1952)"Sleet-Thawing Practices of the New England Electric System,"Transactions of the AJEE,Vol.71 pt.3 August 1952 pp 649-657. DeSieno,C.F.,Imburgia,C.A.,and McDaniel,G.H.(1956)."Sleet Melting on 330-kV Lines of the American Gas and Electric Company and Ohio Valley Electric Corporation Systemes,” Transactions of the ATEE Vol 75 Pt 3,August 1956 pp 625-632. Dumas,G.and Sakamoto,Y.(1986)."Wet Snow Management,"Proceedings,Third International Workshop on the Atmospheric Icing of Structures,Vancouver,British Columbia, pp 417-421. Electrical World (1917)."Prevention of Sleet Accumulation on Lines"Electrical World Vol 71 No 17 April 27,1917.p 879. Gayet,J.(1986)."Prevention of Wire Icing by Joule Heating,"Proceedings,Third International Workshop on the Atmospheric Icing of Structures,Vancouver,British Columbia,pp 429-433. Goia,L.(1993)."Protection of Overhead Line conductors Against Mechanical Overloads," Proceedings,Sixth International Workshop on the Atmospheric Icing of Structures,Budapest, Hungary,pp 171-173. Langdon,G.G.and Marquis,V.M.(1939)"Carrier Attenuation Discloses Glaze Formation" Electrical World,August 12,1939 pp 38-40,100-101. Larcombe,P.,Kunda,W.,Poots,G.and Elliot,J.(1986)."Accretion and Shedding of Ice on Cables Incorporating Free Streamline Theory and the Joule Effect,"Proceedings,Third Interna- tional Workshop on the Atmospheric Icing of Structures,Vancouver,British Columbia,pp 389- -2- 394 Oehlwein,O.L.(1953)"A System Operator's View of Ice Melting on a Power Line While in Service,"Transactions of the AIEE Vol 72 pt 3,December 1953 pp 1200-1207. 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