3386 IEEE Transaction on Power Apparatus and Systems, Vol. PAS-103, No. 11, November 1984 ECCNIVICS OF EHV HIGH PHASE ORDER TRANSNISSION J. R. Stewart, Senior merber E. Kallaur, Mester I. S. Grant, Senior bnerber Power Technologies, Inc. Schenectady, New York Abstract - The economics of high phase order LINE OPTIMIZATION transmission (six or twelve phase lines) are compared to UHV three phase. The comparisons are developed from Many interactive variables affect the final cost optimized line designs, based on realistic lifetime of a transmission line, e.g. voltage, conductor type, costs. Detailed structure designs were used in the size, bundling, structure types, heights, electrical study, with terminal equipment costs included to de- loading criteria, insulators (configuration, electrical velop a breakeven distance beyond which savings in the performance, length, load capability, type), air gap HPO transmission line offset any increased substation clearances, foundation types, soil conditions, and lo- costs. This breakeven distance is typically only a few cal labor and material costs. Optimization is the miles, i.e. much shorter than projected UHV lines. A identification of the least cost combination of these sensitivity analysis allows the general conclusion to variables. For these analyses, an economic optimiza- be drawn that high phase order is econcmically competi- tion program, developed for other line design studies tive with UHV. Additional advantages are that the HPO and including methods of calculating present worth of structures are significantly smaller, and the ROW revenue required (PC'RR), was used [10,11j. probably significantly narrower. Electrical Loading INTRODUCTION Two levels of loading were considered for each order,, the use of more than three High phase phases for power transmission, has been extensively candidate line: studied in the last teh years. A number of papers and 1) 3000 MW. The initial load was assumed to reports [1-7] have presented technical characteristics be 1339 MW with a load growth of 6.5% per and benefits to be obtained by the use of more than year, reaching 3000 MW at year 13. three phases. Increasdd power transfer over existing rights of way and reduced electrical enviromnental im- 2) 6000 MW. The initial. load was assumed to pact are two of these benefits. However, for a tech- be 2679 MW with a load growth of 6.5% per nology to be applied, it must be economically as well year, reaching 6000 MW at year 13. as technically beneficial. Six phase has already been shown to be an economic uprating tool for double cir- Economic Analysis Criteria cuit lines [81. In this paper, 462 kV (phase-ground) six and twelve-phase -lines and 317 kV twelve-phase The PWRR analysis is based on the folilowing lines are compared for relative economics with a assumptions: 1200 kV three-phase design. The five high phase order schemes studied are: 1) All material and labor costs based upon 1982 U.S. dollars. Scheme 1 - Twelve-phase 462 kV, two conductor bundles, self-supporting (rigid) towers 2) Generation fixed charge rate = 16% Scheme 2 - Six-phase, 462 kV, four conductor 3) Transmission fixed charge rate = 16% bundles, self-supporting (rigid) towers 4) Discount rate = 12. 5% Scheme 3 - Twelve-phase, 317 kV, single con- ductor bundles, self-supporting (rigid) 5) Demand charge = $250/kW (assumes towers combustion turbines) Scheme 5 - Same as Scheme 3, except guyed 6) Energy charge = $20/MWH portal towers 7) Required generation reserve = 20 % Scheme 6 - Same as Scheme 3, except guyed Y towers 8) Economic life for payback of investment is 30 years. A Scheme 4 design was found to be structurally indeter- minate and was not considered further. Electrical and 9) Loss factor = 43% mechanical design of these lines are given in a com- panion paper . 10) Loading of lines as given above. 11) Escalation rate = 8.5% per year. 84 T&D 370-3 A paper recommended and approved by the IEEE Transmission and Distribution Committee Any utility contemplating high phase order transmission of the IEEE Power Engineering Society for presenta- will, of course, use its own economic parameters. tion at the IEEE/PES 1984 Transmission and However, a sensitivity analysis shown .later in this Distribution Conference, Kansas City, Missouri, paper demonstrates that the general conclusions of the April 29 - May 4, 1984. Manuscript submitted work presented here are unchanged for reasonable varia- October 28, 1983; made available for printing tions of economic parameters. March 2, 1984. 0018-9510/84/1 100-3386$01 .00© 1984 IEEE Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3387 Economic Choice of Conductor TABLE I Optim Line Design Based on 3000 MW Loading Variables in choosing a conductor are: .PWRR SCHEME VOLTAGE SPAN CONDUCTOR $ x 1000/mi 1) Diameter 1 462 kV 1800' 2167 kcmil Kiwi 1209.1 12-0 2 cond/phase 2) Conductor purchase price ($/lb.) 2 462 kV 1800' 2167 kcmil Kiwi 1177.6 3) Conductor stringing and clipping costs 6-0 4 cond/phase (based upon conductor weight). 3 317 kV 1600' 2515 kcmil Joree 1112.9 12-0 1 cond/phase 4) Strength-to-weight ratio of conductor. This implicitly includes material and 3A 317 kV 1600' 1590 kanil Lapwing 1065.8 stranding. (A conductor with a higher 12-0 2 cond/phase strength-to-weight ratio can be strung 5 317 kV 1600' 2515 kanil Joree 912.9 tighter and thus requires fewer 12-0 l cond/phase supporting structures per given distance than a conductor with a lower 6 317 kV 1600' 2515 kanil Joree 946.5 strength-to-weight ratio.) 12-0 1 cond/phase UHV 1200 kV 1120' 1780 kanil Chukar 1914.3 5) Electromagnetic interference criteria 3-0 8 cond/phase (EMI). (Conformance with local EUI restrictions could necessitate the use of a larger conductor than is optimum economically). TABLE II Opti= Line Design Based on 6000 MW Loading Ten different ACSR conductors were examined in PWRR this study for each HPO structure [12,13]. The base SCHEME VOLTAGE SPAN CONDUCTOR case conductor was 2156 kanil Bluebird ACSR; addi- $ x 1000/mi tional conductors range from 1431 koail Plover to 1 462 kV 1800' 2167 kanil Kiwi 2515 kaiil Joree. 1780 kanil Chukar ACSR (eight con- 1594.9 ductors per phase) was used for the UHV three-phase 12-0, 2 cond/phase line. (The base conductor size for the high phase or- 2 462 kV 1800' 2167 kanil Kiwi 1563.5 der alternatives and the conductor for the 1200 kV 6-0 4 cand/phase three-phase alternative are discussed in Reference .) AC resistance for all conductors was taken at an 3 317 kV 1600' 2515 kcmil Joree 2551.4 12-0 1 cond/phase operating temperature of 500C. 3A 317 kV 1600' 2515 kanil Joree 1854.3 Right-Of-Way (ROW) Requirements 12-0 2 cond/phase .The required width of ROW is based on electrical 5 317 kV 1600' 2515 kcmil Joree 2351.4 and mechanical system parameters (e.g. switching surge 12-0 1 cond/phase level, maximum conductor blowout, EMI, line voltage, 6 317 kV 1600' 2515 kanil Joree 2385.0 etc.). While there is a minimum required width for any 12-0 1 coed/phase transmission line, it would not be correct to assume that all utilities would use the minimum. Also, the UHV 1200 kV 1120' 1780 kanil Chukar 2115.1 cost of ROW varies widely for different locations and 3-0 8 cond/phase areas, making it difficult to assign a meaningful dollar-per-acre ROW cost. For these reasons, cost dif- SENSITIVITY ANALYSIS ferences for the candidate lines studied are presented only as a single illustration, and are not included in The optimum designs in Tables I and II are results the general case. The ROW requirements of EHV high of an analysis where span lengths and conductor sizes phase order lines are less than those of UHV are varied. Shorter spans.require shorter structures three-phase lines, and can result in a significant cost to maintain the specified midspan clearance but need advantage. more structures per mile. Conversely, longer spans re- quire fewer structures per mile but the individual Line Optimization structures are taller and stronger to support the addi- tional conductor weight. Likewise, smaller conductors The high phase order schemes were examined for a cost less, are lighter with resulting reduced struc- range of spans from 800 to 1800 feet. tural requirements, but have greater losses. Tables I and II list the optimum designs for the Cost Components schemes studied for 3000 MW and 6000 MW loadings respectively, considering the electrical and mechanical In addition to conductor, span and structure design constraints (e.g. radio and audible noise, max- technical parameters, various component costs may vary imum span length). from those assumed. The economic parameters used in this study (including material and labor costs) were Scheme 5 is the economic choice for the 3000 MW load chosen to be typical, but obviously there will be con- ($912,900/mile), and Scheme 2 for the 6000 M load siderable variations throughout the United States. To ($1,563,500/mile). The effect of terminal equipuent assess the sensitivity of the PWRR to changes, a costs on the optimum choice is given below in Tables IX 50 percent adder was applied to the following to ex- and X. amine their effects on the overall MWRR: Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3388 1. Conductor cost Different Conductor Bundles (Schemes 3 and 3A) 2. Stringing and sagging cost 3. Tower steel cost The analysis shown in Tables I through III is 4. Tower erection cost based on a single conductor per phase for Scheme 3 to 5. Generation demand charge provide an extreme comparison of lower phase-ground 6. Generation demand escalation factor voltage and small conductors, so losses have the maxi- 7. Generation energy charge mum effect. Scheme 3A in Tables I and II uses the same 8. Generation energy escalation factor self-supporting steel tower as Scheme 3 except that the optimization process is conducted over a range of con- A summary of the sensitivity analysis appears in ductors with two conductors per phase. Double conduc- Table III. tor bundles result in savings of 4 percent for 3000 MW loading and 27 percent for 6000 MW over the single con- TRABLE III ductor bundle case. The economic choice of Scheme 5 Sensitivity of 8R, Based Upon 50 Percent Cost Gradient for a 3000 MW load and Scheme 2 for 6000 MW remains unchanged. However, double conductor bundles do result in 317 kV twelve-phase having lower cost than UHV for 3000 MW LINE LQADING 6000 MW LIE LOADING WEIITGE WEICR1'E 6000 MW, and the possibility of overall superiority SENSITIVITE SCNEME VARIABLE * PER8EiT IREASE SFRR $ x 100' 0/rni. PEt4ENT INCREASE PWRR $ x 1000/li. when terminal equipment costs are considered. 1 Design Assumptions: Maximum Ground Level E Field 1 14.14 1380.1 10.72 1765.9 2 7.12 1294.9 5.40 1681.0 3 5.95 1281.6 4.51 1666.8 Other sensitivity analyses are possible by varying 4 8.60 1313.1 6.52 1698.9 the initial design assumptions, although these were not 5 2.07 1234.5 6.28 1695.1 6 3.62 1252.6 9.56 1766.7 included in the cost values above. Spacing and clear- 7 3.25 1249.0 9.25 1749.7 ance configurations of the high phase order schemes 8 5.68 1278.0 15.01 1854.5 were designed to permit a maximum ground level electric 2 field strength of 8 ky/meter . If this restriction 1 14.52 1348.4 10.94 1734.5 were relaxed to allow a higher ground level field 2 7.31 1263.6 5.51 1649.6 3 5.32 1240.0 4.00 1626.0 strength (e.g., 11 ky/meter), the result would be 4 7.69 1268.3 5.79 1654.0 shorter towers with lower overall costs. For example, 5 2.13 1202.3 6.02 1663.5 -6 3.72 1221.2 9.77 1732.7 if the Scheme 1 tower height were decreased by 5 feet, 7 3.34 1216.5 8.77 1716.9 the tower would weigh 1250 pounds less and cost $625 8 5.83 1245.9 15.33 1820.5 less. For 1800' ruling spans, this would decrease the 1 9.11 1214.2 3.97 2652.7 line installed cost by $1833 per mile. 2 8.32 1205.3 3.63 2644.0 3 2.90 4.19 1145.2 1.26 2583.5 Insulators and Foundations 4 1159.6 1.83 2598.1 5 8.38 1206.4 14.63 2924.7 6 14.66 1276.5 25.59 3204.3 One set of mechanical loading criteria was used 7 13.16 1259.8 22.96 3137.2 for the insulator system designs for the high phase or- 8 23.02 1368.9 40.16 3576.0 der structures. To Lnore accurately model the overall 1 9.11 996.0 3.97 2444.8 scheme costs, a series of detailed insulator designs 2 8.32 988.7 3.63 2436.8 should have been used. The outcome might influence the 3 4 2.90 4.19 939.4 951.2 1.26 1.83 2381.0 2394.4 actual PWRR costs, but the economic ranking of line de- 5 8.38 989.6 14.63 2695.4 signs is not expected to change, particularly since the 6 14.66 13.16 1046.7 25.59 2953.1 optimized solution is very close to the base case 7 1033.0 22.96 2891.3 8 23.02 1123.0 40.16 3295.7 design. As for the insulator loadings, the foundations 1 9.11 1032.7 3.97 2479.7 used in the high phase order structures were not 2 8.32 1025.2 3.63 2471.6 3 2.90 973.9 1.26 2415.1 examined for sensitivities due to loading changes. 4 5 4.19 8.38 986.2 1025.8 1.83 14.63 2428.6 2733.9 Obviously, an actual line design would require detalieo 6 14.66 1085.3 25.59 2995.3 foundation costs as a function of loading-changes, and 7 8 13.16 23.02 1071.1 1164.4 22.96 40.16 2932.6 the PWRR would change for each individual line, but the 3342.8 economic ranking would also probably remain the same. UHV 1 2 - - _ _ ECONOMICS OF LINE TER4INALS 3 - _ 4 - _ For this analysis, it is assumed that a new 5 0.7 1927.3 2.5 2167.2 6 - voltage level is being brought into a substation. 7 1.1 1934.8 3.9 2196.9 Transformation will be installed for the full line 8 - capacity to a lower voltage level presently existing in the station, assumed to be 345 kV (three-phase). For a * 1 - Conductor Cost 2 Stringing and Sagging Cost - 3 - Toer Steel Cost point-to-point application a terminal will be required 4 - Tower Erectic* Cost 5 Generaticn Denand Charge - at each end. 6 - Generation Demand Escalation Factor 7 - Generation Enrgy Charge 8 - Generation Energy Escalation Factor The economic analysis of substations is even more camplex than that of transmission lines. The variety of bus arrangements, protection schemes, other lines From Table III, the high phase order Scheme 3 that may terminate at the same substation, ground mat design is still the most economic for 3000 MW loading, requirements, and utility design specifications regard- while the 1200 kV UHV three-phase option remains the ing switching and reliability, make substation costing a difficult and highly variable process. However, in most expensive. The high phase order Scheme 2 is still the most economic for 6000 MW loading, while the high contrast to transmission lines, substation costs are phase order Scheme 3 remains the most expensive. Thus generally dominated by a few large units of a 50 percent increase in the individual cost components equipment--transformers and circuit breakers-- and er- leaves the ranking of options unchanged. rors in properly accounting for protective relaying and Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3389 other smaller items have a minor impact on the overall TABLE V cost of the station. Transformer Cost Per Terminal ($ Millions) Major Substation Cost Components LINE RATING (MVA) Only two major substation cost components are LINE DESCRIPTION -3000 6000 considered in this analysis--transformers and circuit 1200 kV 3-phase 14.4 28.8 breaker/protective equipment. Installed transformer cost is generally 60 to 80 percent of total substation 462 kV 6-phase 15.6 27.5 cost. The costs of transformers and circuit breakers 18.8 31.3 are derived from discussions with several equipment 462 kV 12-phase manufacturers. Accuracy of the costs is tempered by 317 kV 12-phase 16.3 28.8 lack of manufacturing experience with HPO and 1200 kV equipment. The costs of installation, engineering, and transportation are accounted for by multipliers or ad- Other Terminal Costs ders based upon the experience of several firms who have extensive EHV substation design experience. Costs associated with purchasing and installing the circuit breakers, protective relaying equipment, Transformer Costs instrument transformers, surge arresters, buswork,and switches are determined in terms of the cost of pur- At EHV, transformer cost is a linear function of chasing circuit breakers because the circuit breaker kVA in each voltage class and can be estimated as: cost dominates the non-transformer terminal costs. It is assumed that standard circuit breakers can be used transformer cost ($) = K + S x kVA on both the six and twelve-phase high phase order lines. The high phase order cost penalty then is where: simply due to the requirement for additional circuit breakers to handle the additional phases. TChree-phase K = base cost (in dollars) SF6 circuit breakers for the 317 kV twelve-phase design are commercially available at a purchase price of S = rating proportionality constant (dollars/ $350,000 each. Similar breakers for the 462 kV high kVA) phase order tenninals are estimated to be $700,000 each. Extrapolating these costs to the 1200 kV three-phase case gives a cost of approximately $1,200,000 each. Since UHV circuit breakers are not The constants in the pricing equation are a yet commercially available, the initial cost would function of the transformer turns ratio, the trans- probably be somewhat higher due to engineering and former efficiency, and the high voltage winding BIL. manufacturing development. However, the dependence of the K and S values on these parameters is different. From a review of the pricing The costs of shipping, installation, protective policies of two major manufacturers, over a range of relaying, etc., are considered as a multiplier of the three-phase unit ratings from 750 to 3000 MVA (FOA) S circuit breaker cost. This multiplier is taken as 3.0 is a constant equal to $3.00/kVA. The base cost of the . The different continuous and short circuit cur- transformer, K, depends on the MVA and the voltage rent levels associated with the three different line class (specifically the BIL of the high voltage ratings will affect the circuit breaker cost in a winding) as shown in Table IV. secondary way, but are ignored in this study. Costs for this terminal equipment are given in Table VI. TABLE IV TABLE VI Transformer Base Cost, K ($ Millions) Other Terminal Equipment Costs FOA RATING PHASE-TO-GRCUND VOLTAGE RATING (MVA) (kV) 1200 kV 3-phase installed C.B. etc. = $3.6 million 317 462 693 462 kV 6-phase " = $4.2 million 462 kV 12-phase " = $8.4 million 750-1250 1.0 1.5 2.0 317 kV 12-phase t= $4.2 million 1500-2250 1.25 1.75 2.25 2500-3000 1.5 2.0 2.5 Total Substation Cost Comparison The total installed substation cost per terminal The costs of transporting, installing, building a for 3000 and 6000 MVA capacities is the sun of the foundation, and filling the transformer with oil are costs in Tables V and VI, and is given in Table VII. accounted for by increasing the cost in Table IV by 25 percent. TABLE VII Installed Transformer Costs Tbtal Installed Cost Per Terminal ($ Million) LINE RATING (MVA) Transformer costs are given in Table V for four transmission line terminals-two twelve-phase (317 and LINE DESCRIPTICN 3000 6000 462 kV phase-ground), one six-phase(462 kV 1200 kV 3-phase 18.0 32.4 phase-ground), and one three-phase (1200 kV phase-phase) -for 3000 and 6000 MVA ratings. 462 kV 6-phase 19.8 31.7 462 kV 12-phase 27.4 39.7 317 kV 12-phase 20.5 33.0 Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3390 Discussion of Terminal Costs class, which means that new terminal equipnent is re- quired at both ends of the line to carry the full an- Table VII shows that the terminal costs for the ticipated line loading for each alternative. This is a high phase order lines are generally slightly higher reasonable approach since the first application of UWV (about 10%) than the terminal costs associated with the will probably be of this nature. One example is a high 1200 kV UHV 3-phase line. capacity connection across the Cascade Mountains where right of way is environmentally limited, but a high ca- The two major reasons for the higher high phase pacity link may be needed in the future. Following the order terminal costs are: installation of the first line of a new voltage class or phase order, a system will develop where lines are interconnected, and it is no longer necessary to in- 1) At low MVA ratings, more transformer clude full transformation at both ends of each line. units are assumed for the phase and volt- It is reasonable to use the point-to-point scenario for age transformation than for the voltage this analysis since both UHV and high phase order will transformation required by the 3-phase be first applied in this manner. This gives full 1200 kV line. That is, only one 3-phase weight to any terminal cost penalty which may be transformer is required to terminate a charged against high phase order designs and thus gives 3000 MVA 3-phase line whereas four 750 a conservative comparison. MVA 3-phase transformers are required for the 12-phase alternative. In both cases Table IX presents the breakeven distance for the voltage is transfonmed to 345/ 1.732 3000 MW loading for the UHV line and high phase order kV to ground, but additional transformers Schemes 1, 2, 3, and 5 using the line PWRR from are required to convert the 12 phases to Tables I and II. A "Scheme 3A" is added to include the 3. The cost difference is due to the optimum double conductor Scheme 3. This provides a base cost of the single 3-phase 1200 kV comparison of the three self supporting structures for versus the base cost of the four 462 kV different voltage/phase order combinations and the most or 317 kV units. In reality, it is economical guyed structure. likely that special 3 to 6 or 3 to 12-phase transformers will be built that TABLE IX would somewhat reduce this cost Breakeven Distance, 3000 MW Loading difference. (Cost in Millions $, Distance in Miles) 2) High phase order needs additional circuit SCHEME breakers and associated hardware. For SCHEME SCBE SCHEME 3A SaHEME example, a single 3-phase circuit breaker 1 2 3 120 5 is required for the 3-phase line whereas 120 60 120 2-burnd 120 four 3-phase breakers are required for a WHV 462 kV 462 kV 317 kV 317 kV 317 kV 12-phase line. The cost of each of the four breakers is less than the cost of PWRR 44.8 68.2 49.2 51.0 51.0 the single breaker because those for the 51.0 For 2 12-phase line are rated for a lower Stations phase-to-ground voltage, but the total cost is greater. Line 1.914 1.209 1.178 1.113 1.066 .9129 Despite these differences, as shown in Table VII, Mile in most cases the terminal costs for HPO are comparable to those for UHV. Break- 33 6 8 7 6 Table VIII gives PWRR installed costs for the line Even terminals to be integrated with the line PWRR. Distance TABIE VIII Table IX shows that all the high phase order schemes are more econamical than the UHV line for Total PWRR Per Terminal ($ millions) 3000 M loading and lines longer than 33 miles. Since it is unlikely that applications would be for a dis- LINE RATING (MVA) tance as short as 33 miles, it is reasonable to con- LNE DESCRI 3ON 3000 6000 clude that at this loading high phase order designs 1200 kV 3-phase 22.4 40.3 will at least be equivalent to and may often have an economic advantage over the UHV three-phase option. 462 kV 6-phase 24.6 39.4 462 kV 12-phase 34.1 49.4 Table X gives tne breakeven distance for the same lines for 6000 MW loading. 317 kV 12-phase 25.5 41.0 From Table X, it can been seen that the 462 kV COMBINED ECONOMICS OF LINES AND STATIONS six-phase schene is always the economic choice for 6000 MW loading, while the 462 kV twelve-phase scheme is less costly than UHV for distances greater than 35 Breakeven Distance miles. Since the six and twelve-phase 462 kV lines both have approximately the same AMRR per mile, the A method commonly used for comparison of HVDC with difference in breakeven distance is due to terminal AC alternatives is to calculate a breakeven distance costs. The two conductor bundle 317 kV scheme is less where the savings fram the DC transmission line balance costly than UHV for distances greater than 5 miles. It the additional cost of the DC terminals. The same has greater losses than the 462 kV twelve-phase scheme technique is useful for a comparison of high phase or- but lower terminal costs result in a shorter breakeven der with three-phase UHV. For this analysis, a new distance. transmission line connecting two points of an existing system is assumed as the first of its type/voltage Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3391 The purpose of this analysis was to demonstrate Breakeven Distance, 6000 MW Loading general, rather than specific, economic relationships (Cost in Millions $, Distance in Miles) between HPO and three-phase. The sensitivity analysis proves the generality of the conclusions developed. SCHEME These general conclusions are: SCHEME SCHEME SCHEME 3A SCHEME 1 2 3 120 5 1) Terminal equipment costs for HPO are 120 60 120 2-bund 120 generally slightly higher than those for UHV 462 kV 462 kV 317 kV 317 kV 317 kV UHV, although in certain instances they may be lower. PWRR for 2 80.6 98.8 78.8 82.0 82.0 82.0 Stations 2) Transmission line PWRR is generally less Line PWRR/ 2.115 1.595 1.564 2.551 1.854 2.351 for HPO than for UHV, for the same power mile capacity. Breakeven _ 35 0 * 5 * 3) For lines longer than a few miles, Distance savings in the line offset the terminal equipment costs, making HPO the economic Notes: (detailed discussion belcw) alternative. 4) HPO is an alternative to UHV, at similar *up to 20% more expensive than UHV for typical line or possibly less cost. In addition, HPO lengths, iqnoring RiW costs lines will be smaller than UHV, and will probably require less ROW. The single conductor bundle 317 kV schemes are always more costly than UHV for 6000 MW lQading. These qualitative conclusions are unchanged by the Terminal costs are comparable between 317 kV sensitivity analysis or by other variables, such as twelve-phase and UHV; the difference is due to the-in- slight differences in structure design conditions  creased cost of losses at the lower phase-ground volt- and the possibility of refinements to both HPO and UHV age with only one conductor per phase. designs as these technologies mature. Example Effect of ROW Cost ACKNOWLEDGEMENTS The analysis of the data in Tables IX and X does The work reported in this paper was sponsored by not include right of way cost, because right of way the Division of Electric Energy Systems, costs vary widely, and any attempt to introduce them on U. S. Department of Energy under contract other than a specific basis is open to criticism. As DEAC-01-78-ET-29297, Kenneth Klein Program Manager. an illustrative example, however, if right of way width Mechanical structure design was developed by SAE and were dictated by an edge of right of way ground level H. Brian White. electric field of 1.5 kV/m, the 317 kV twelve-phase schemes would require 145 feet less width than the UHV REFERENCES line, or 17.6 less acres per mile. At $5,000 per acre, this is an installed cost saving of $88,000 per mile or 1. J. R. Stewart and D. D. Wilson, "High Phase Order a PWRR saving of $110,000 per mile for the 317 KV Transmission--A Feasibility Analysis Part twelve-phase lines (Schemes 3, 3A, 5, and 6) compared I-Steady State Considerations," IEEE Transactions to the UHV design. on Power Apparatus and Systems, Vol. PAS-97, No. 6 , Nov.A/Dec., 1978, p2300 Sensitivity to Terminal Cost 2. J. R. Stewart and D. D. Wilson, "High Phase Order Table IX gives the breakeven distance for the Transmission--A Feasibility Analysis Part 462 kV six-phase scheme as 6 miles. If the PWRR of the II-Overvoltages and Insulation Requirements," UHV and high phase order terminals were both increased Ibid., p2308 50 percent, the breakeven distance increases 50 percent to 9 miles. If the PWRR of only the high phase order 3. Switching Surge Characteristics of High Phase terminal were increased 50 percent, the breakeven dis- Order Lines, U. S. Department of Energy Report tance becomes 39 miles. If the PWRR of only the UHV DOE/ET/29297-1, March, 1982 terminal were increased 50 percent, the six-phase line would be less expensive for any length. Thus, terminal 4. Technical and Economic Characteristics of High cost variations do not change the general conclusions Phase Order Transmission, U.S. Department of regarding the economic feasibility of EHV high phase Energy report DOE/ET/29297-2, 1983 order. 5. EHV High Phase Order Power Transmission, CONCLUSIONS U. S. Department of Energy report DOE/ET/29297-3, 1983 An economic optimization study was made to compare HPO alternatives to UHV transmission. To ensure 6. I. S. Grant et al, "Higher Phase Order realism, specific technical and economic parameters Transmission Line Research,," CIGRE 220-02, CIGRE were assumed and the analysis completed as for an ac- Symposium on Transmission Lines and the tual line design. A sensitivity analysis was used to Environment, Stockholm, June, 1981 assess the effect of assumptions inherent in this type study. Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply. 3392 7. I. S. Grant and J. R. Stewart, "High Phase 10. I. S. Grant and V. J. Longo, "Ecolnomic Incentives Order-Ready for Application," IEEE Transactions on for Larger Transmission Conductors," IEEE Power Apparatus and Systems, Vol. PAS-101, No. 6, Transactions on Power Apparatus and Systems, June, 1982, p1757 Vol. PAS-100, No. 9, Sept., 1981, p 4291. 8. E. Kallaur and J. R. Stewart, "Uprating Without 11. R. E. Clayton, "Transmission Line Econonics and Reconductoring, the Potential of Six-Phase," Optimization,," PTI Newsletter, No. 25, April, Canadian Comnunications and Energy Conference, 1981. Montreal, Oct., 1982, IEEE 82CH1825-9 p120 12. Transmission Line Reference Book 345 kV and Above, 9. I. S. Grant and J. R. Stewart, "Mechanical and Electric Power Research Institute, Palo Alto, Electrical Charatteristics of EHV High Phase Order Cal., 1975. Overhead Transmission,," IEEE 1984 Transmission and Distribution Conference and Exposition, Kansas 13. Aluminum Electrical Conductor Handbook, The City, Mo., April 29-May 4, 1984. Alxuminun Association, Washington, D.C., 1982. Authorized licensed use limited to: UNIVERSIDADE DE SAO PAULO. Downloaded on March 18,2010 at 09:17:39 EDT from IEEE Xplore. Restrictions apply.