A Holistic Method for Conductor Ampacity and Sag Computation on an OHL Structure

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‘A Holistic Method for Conductor Ampacity and Sag Computation on an OHL Structure’

K. Kopsidas, S. M. Rowland, B. Boumecid,

IEEE Trans Power Delivery, Volume: 27, pp. 1047-1054 (2012)

DOI: 10.1109/TPWRD.2012.2187464

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 27, NO. 3, JULY 2012 1047

A Holistic Method for Conductor Ampacityand Sag Computation on an OHL Structure

Konstantinos Kopsidas, Member, IEEE, Simon M. Rowland, Senior Member, IEEE, and Boud Boumecid

Abstract—The rating current (ampacity) of a conductor erectedon a particular overhead line (OHL) structure installed at a speci-fied location is influenced by the conductor, the OHL structure, aswell as weather and operational parameters. Many studies havebeen carried out regarding calculating an aerial bare conductor’sampacity at a steady-state conductor temperature, but withoutconsidering the OHL structure as part of the system. In this paper,a holistic methodology for calculating the conductor’s ampacityand sag at any temperature and power frequency, erected ontoa prespecified OHL structure is developed, considering togetherthe mechanical and electrical parameters of the overall system.This methodology incorporates the conductor’s basic materialproperties allowing the calculations to be applied to newly devel-oped high-temperature low-sag composite conductors. In this way,it becomes possible to identify, at the system level, the potentialbenefits that may result from the improved performance of theseconductors as well as to indicate new sizes that may better fit aprespecified system, optimizing its performance. The methodologyis also validated with a real system application, resulting in correctpredictions of the performance of a four-span double-line system.

Index Terms—Aging, ampacity, bare conductors, conductorcreep, high temperature, low sag, overhead line, reconductoring,re-tensioning, sag, tension, thermal rating, upgrating, uprating.

I. INTRODUCTION

T HE NEED TO increase the power transfer capacity ofexisting distribution and transmission lines has resulted

from the growth in demand for, and generation patterns of, elec-trical power. However, this is not always easy to achieve in aderegulated environment where competition forces utilities tooperate existing lines at maximum rated capacities due to en-vironmental and cost barriers. As a result, utilities may attemptto extract the most out of the installed lines by operating themcloser to the thermal limit, and even temporarily exceeding it,causing a loss of strength in the conductor and increased sags,leading to higher risk operation and occasional blackouts [1].

Manuscript received June 15, 2009; revised April 18, 2011; acceptedNovember 09, 2011. Date of publication June 14, 2012; date of currentversion June 20, 2012. This work was supported by the EPSRC Supergen V,U.K. Energy Infrastructure (AMPerES) Grant in collaboration with the U.K.electricity network operators working under Ofgem’s Innovation FundingIncentive scheme. Paper no. TPWRD-00449-2009.

K. Kopsidas and S. M. Rowland are with the School of Electrical and Elec-tronic Engineering, The University of Manchester, Manchester M13 9PL, U.K.(e-mail: [email protected]; [email protected]).

B. Boumecid is with the National Grid Electricity Network Invest-ment Department-Asset Policy, Warwick CV34 6DA, U.K. (e-mail:[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPWRD.2012.2187464

An economical method to increase the capacity of an existingsystem can be achieved by enabling existing lines to operateat higher temperatures. This may infringe ground-clearancerequirements, but can be accomplished by re-tensioning theconductor, a technique mainly based on the increase of the con-ductor’s clearance to the ground by increasing its tension on thepower line. This, therefore, will increase the thermal limit of theline since more thermal expansion can be allowed, permittingmore current to flow through it. Another way to achieve powercapacity increase is to replace conductors (reconductoring)with larger all aluminum alloy conductors (AAAC) or alu-minum conductor steel reinforced (ACSR) wire or conductorswith new materials which permit higher temperature operationand developing lower sags. The latter are usually referred toas high-temperature low-sag (HTLS) conductors. Either way,the computations for the new maximum current capacity andconductor sag have to be performed for the new conductorwhich will become part of the existing OHL system.

This paper presents a holistic methodology that enablesevaluation of the maximum sag and ampacity of a conductorconsidering its structure and the electromechanical propertiesof its basic materials as well as OHL structure constraints.This methodology provides the flexibility to evaluate the per-formance of nonstandard conductors on a prespecified OHLsystem. The validation of this methodology with a real systemapplication is also presented.

II. OVERVIEW OF EXISTING LITERATURE

ON SAG-TENSION METHODS

Many studies have dealt with calculating an aerial bare con-ductor’s sag and ampacity at a steady-state conductor tempera-ture. Most of this paper makes use of the widely accepted “rulingspan” method of sag-tension calculation for multiple suspensionspans. The method provides solutions to the parabolic and hy-perbolic equations which define the relationship between span,sag, and tension.

Considerable work on the topic took place during the 1950sand 1960s, mainly focusing on graphical and analytical methodsfor sag-tension calculations [2]–[4] and methods for the estima-tion of the current-carrying capacity of ACSR conductors [5],[6]. A method for sag-tension calculation based on stress-strainand temperature elongation data obtained on ACSR conductorswas presented in [7] and had been further extended and de-veloped to a computer program (STESS) for use in transmis-sion line and operation [8]. A similar stress-strain approach isalso followed by [9] in an attempt to deal with the limitationsof existing methods and software concerning gap-type conduc-tors. Other recent modifications to the methods include a hy-

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1048 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 27, NO. 3, JULY 2012

brid numerical method to calculate the sag of composite con-ductors [10] and an “aluminum stress method” which allows vi-bration constraints to be based on specified values of static ten-sile aluminum stress [11]. There are also commercially availablesag-tension programs which give good results for most practicalapplications [12], [13].

These methods were initially developed to evaluate the per-formance of conventional (AAAC and ACSR) conductors byalso incorporating experimental measurements of existing con-ductors. Recent research in this area has been extended to in-clude novel (HTLS) conductors in these evaluations [14]–[17].A comparison of the performance of ACSS with ACSR and alu-minum conductors aluminum reinforced (ACAR) is presentedin [15] assuming the system is under specific extreme heavyloading conditions. With this specific comparison, the ACSSconductor appears to perform better because of the differentmaximum tension at the heavy load condition [15]. In [16],ACSS, ZTACIR, and CTACSR conductors are also comparedwith ACSRs due to their bimetallic similarities.

Most of the sag-tension methods and packages, even thoughproducing acceptable predictions, are limited to estimatingconductors’ performance based on data provided by conduc-tors’ manufacturers. Hence, they are not flexible to investigatehow nonstandard conductors will perform. Furthermore, lim-ited work has been done to examine conductor performanceincorporating the properties of the structure (wood pole orlattice towers) to evaluate the real benefit of different HTLSconductors when compared with ACSRs and AAACs.

In order to progress efficiently to these investigations, a moreholistic approach should incorporate, along with the weatherloading and conductor properties, the system limitations toallow nonconventional conductors (in size and materials) to beevaluated on prespecified systems. These considerations aretaken into account in the methodology introduced in this paper.This allows the overall performance evaluation of lighter con-ductor technologies with different sag performance, instead oflimiting the comparisons only to conductors’ sag performance.Furthermore, reconductoring scenarios can be investigatedconsidering new technologies and conductors of compositematerials and nonstandard sizes.

III. COMPUTATIONAL FRAMEWORK

A. Outline of the Computations

The current rating of a conductor erected on a particularOHL structure at a specified location is controlled by theweather, the conductor, the OHL structure, and operationalconditions. This current rating specifies the maximum powertransfer capability of the OHL system. The overall performanceof the system is affected by properties that can be dividedinto three distinct groups: 1) mechanical; 2) electrical; and 3)aging. Consequently, the computations are performed in threelevels: 1) mechanical; 2) electrical; and 3) aging. Every level isinfluenced by the weather, conductor structure, and operationalconditions. These three distinct computational levels are linkedtogether as shown in Fig. 1 in order to compute the conductormaximum current capacity and maximum sag. The input dataare divided into four groups: 1) the OHL support structure

Fig. 1. Flowchart of the computations.

data; 2) the weather data; 3) the conductor data; and 4) theoperational data.

OHL data describe the structure at the time of installationof the wires. These include the design installation tensile stressof the electrically unloaded conductor, the ambient temperatureduring the installation, the span length, the type of insulationsets, and the difference between the insulation set attachmentlevels as well as their heights from the ground. The last threeare determined by the support structure (i.e., the lattice tower orwood pole) of the OHL system.

The weather data include the ice thickness, ice density, andthe wind speed at a given ambient temperature which definethe designed maximum weather loading. These data are usu-ally described by weather maps [18]–[20] or can be derivedfrom historical data. These determine the absolute maximumworking tension (AMWT) that the conductors may experienceand, therefore, the maximum sag value developed at low tem-peratures. This group also includes weather data that are usedfor the current-temperature calculations as described in [21].

The conductor data involve a conductor’s electrical and me-chanical properties as well as its physical design. The most basicproperties are the density, modulus of elasticity, coefficient ofthermal expansion, tensile strength, conductivity, stranding pat-tern, grease pattern and density, and type of strands (trapezoidalor cylindrical), as well as their diameter. These are usually pro-vided by conductor manufacturers and are included in relevantstandards [22]–[29] for the most standard conductor types.

The last group, operational data, includes the maximum oper-ating temperature of the conductor, system frequency, method-ology used for mitigation of the conductor creep (if any), pre-dicted duration of the maximum conductor operating tempera-ture, designed emergency loading, and duration of operation atthe elevated temperature.

KOPSIDAS et al.: HOLISTIC METHOD FOR CONDUCTOR AMPACITY AND SAG COMPUTATION 1049

Some of the variables that describe the overall structure haveto be predefined in order to initiate the computations. These vari-ables are the ones that define the weather loading, the maximumoperating loading, and the OHL structure.

The methodology summarized in Fig. 1 and detailed in sub-sequent sections can then be used to calculate and comparethe electrical and mechanical performance of different conduc-tors for the same OHL structure and identify the most suit-able for the particular structure. Changes in the OHL structurecause changes in the performance of the same conductor, asdo weather changes (e.g., maximum ambient temperature, max-imum wind speed, ice loading, etc.).

Fig. 1 also shows that the computations at the aging level areperformed at the end in order to calculate the final conductorsag. This computation level can also be used to evaluate the in-crease of initial conductor tension that is needed to balance theplastic strain of the conductor. Furthermore, if pretensioning ofthe conductor is considered in the initial input data (affecting theOHL and conductor data groups), this part may be omitted, forsimplification, and the final system condition would be the con-ductor sag calculated at the mechanical level with the same con-ductor ampacity. However, conductor pre-tensioning may not bepermitted by the strength of the support structure.

B. Mechanical Computations

The mechanical part of the computations is performed to cal-culate the conductor sag and tension at the designed maximumoperating temperature of the conductor . In order toachieve this, the maximum conductor tension (MCT) of thespecified OHL system is required.

The MCT (i.e., the maximum working tension of the con-ductor on a particular OHL system) is controlled by the fol-lowing limitations that are generally applied in any structure:

• the maximum permitted tension allowed by the weakestsystem component which may be the insulator pin, the in-sulator, or the tower/pole structure; this tension limit is de-fined in the calculations as the structure maximum workingtension (SMWT);

• the self-damping vibration limit tension of the conductoreffectively defines the everyday tension (EDT) at a speci-fied conductor temperature; this limit is usually employedto reduce the aeolian vibrations to an acceptable level[20] and determines the conductor’s vibration limitedmaximum working tension (VLMWT);

• the absolute conductor working tension (ACWT) for thespecified weather loading, for example, 50% of the con-ductor rated breaking strength (RBS) at 5.6 C with com-bined wind and ice [20], [29]; the weather (ice and wind)loading and the minimum temperature of the conductor in-fluence the MCT since they affect the elastic (weight) andthermal (temperature) elongation of the cable.

The procedure to determine the MCT of the power-linedesign is illustrated in Fig. 2. Initially, the weather-loadingconditions of a power line (for example, load cases 1 to 6 in[29] and [30]) are identified by its location and the help ofweather maps [20], [29] or historical data. The weather-loadingconditions also define the corresponding safety factors (SF)[29]–[31]. These safety factors are applied to the conductor

Fig. 2. Flowchart of the procedure for MCT calculation of an OHL system.

and the structure (insulator/insulator pin), and the smallestmaximum allowable tension of these is set as the absolutemaximum working tension (AMWT) of the conductor appliedon the specified system (Fig. 2).

The Newton–Raphson iteration method is employed on thechange of state (1), derived from the catenary curve. In (1), theelastic and thermal elongations of the conductor are includedwith the plastic elongation computed separately since the latteris affected by the operating conditions [32]

(1)

with

Thermal elongation

Elastic elongation

where subscripts and define the final and initial conditions,respectively, and

horizontal conductor tensile force;

resulting conductor weight per-unit length;

span length;

conductor temperature;

conductor’s coefficient of thermal expansion;

conductors modulus of elasticity;

conductor cross-sectional area.

The everyday tension (i.e., the design stress in the unloadedconductor that is applied to minimize the aeolian vibrationsof the conductor at a designed temperature) and the conductorweight are set as initial conditions while the final conditions arethe conductor resulting weight (i.e., the vectorian sum of the


conductor, wind, and ice weight) and the VLMWT at the max-imum-designed weather loading.

The output VLMWT of this iteration is then compared withthe AMWT and the smallest one defines the MCT of the OHLsystem at the specified weather loading.

Once the MCT is known, then a second Newton–Raphson it-eration of (1) takes place having as initial conditions the MCTof the OHL system and the conductor resulting weight (i.e., thesum of the conductor, wind, and ice weight) at the maximumdesigned weather loading temperature, in order to identify theconductor tension at any operating temperature(Fig. 1). Once the conductor tension at the operating tempera-ture is calculated, the sag is computed by using the catenarycurve. The output is then linked with the other two computa-tional parts.

The MCT computation (described in Fig. 2) is performedbased on the conductor design and material properties as illus-trated in Fig. 3. This condition is set as a reference point andthen using (1), the final tension and sag can be evaluated at dif-ferent temperatures with an iteration process using small (1 C)temperature steps. The aluminum and steel tensions are com-puted from the conductor tension incorporating the conductorcreep. The iteration continues up to the knee point, which de-fines the temperature at which the aluminum contributes zeroforce to the conductor. The tension and sag at this point arethen set as initial conditions to perform calculations for tem-peratures above the knee point. A new iteration takes place toevaluate the final tension and sag conditions above this point.This is performed using a modified version of (1), where theconductor properties that affect the thermal andelastic elongations are replaced with the values that correspondto the conductor’s core , since the core de-fines the elastic and thermal elongations of the equation abovethe knee-point temperatures.

C. Electrical Computations

The electrical part of the computation is used to calculate theac resistance of any conductor at any temperature de-fined in the previous part of the computations instead of usingthe linear interpolation and the tabulated data of [33] for thestandard conductor sizes described in [21]. This increases theflexibility in the type and size of conductors that can be exam-ined, since this method is not limited to the conductors includedin [33]. It also improves accuracy.

The detailed computations within this step of the process areillustrated in the flowchart of Fig. 4. The basic electrical andphysical properties of the materials used for the conductor, aswell as the conductor itself are used to calculate the dc resistance

at 20 C based on the conductivity, thermal coefficients,diameter and number of strands, and spiraling factors speci-fied by ASTM for cylindrical and trapezoidal strands [22]–[29].For wires of distinct strength (core) and conductive (aluminum)members, the is calculated separately and every part isthen corrected to the operational temperature by using the ap-propriate temperature coefficients [22]. The overall of theconductor is then computed by considering core and outer con-ductive member resistances in parallel configuration. When the

Fig. 3. Flowchart of mechanical computations for the conductor tension andsag at final system conditions.

conductor’s core is of the same material and shape of strands,then the is calculated by omitting the core’s calculations.

To compute conductor , the skin factor is calculatedbased on the physical structure of the conductor. The skinfactor calculation is based on the work of Dwight [34]–[36]and Lewis and Tuttle [37] which is further simplified with theuse of [38] in the code presented in this paper. The skin factorcalculation is performed on cylindrical and tubular conductorshapes, in order to evaluate the effect of non-conductive corematerials on conductors.

A second correction factor for the calculations is thenapplied for cases when steel material is used for the core designof the conductor, in order to address the magnetization effectof the core on the conductor’s . This effect is negligibleon ACSR conductors with even numbers of aluminum layers[21], [33], [37], [39] and so, it is not considered in these cases.For the ACSR conductors with an odd number of aluminumlayers, however, the magnetization factor is used to accuratelycalculate the (Fig. 4). In the case of single-layer ACSR,the correction method described in [21] is used, while for thethree-layer conductors, the approach of [39] is employed.

Since the magnetization factor is influenced by current flowthrough the conductor, an iteration with the use of [21] takesplace to correct the calculation as illustrated in Fig. 4. Thismakes the resistance of steel core conductor technologies de-pendent on conductor temperature and current flow, unlike otherconductor technologies whose resistance is dependent on theconductor temperature.


Fig. 4. Synopsis of the ac resistance calculation methodology used.

The method described here is employed for calculatingthe of any aluminum alloy conductors (AAC), ACAR,AAAC, and ACSR or any other bimetallic and “bimaterial”conductor technology, type, and size. It can, furthermore, beused for “tubular stranded” conductors or more practicallyfor non-conductive composite core stranded conductors. Thedifference in the final result of the computation betweendifferent types of conductors is determined by the of theoverall cross-section area of the conductor, the skin factor, andthe magnetization factor differences.

D. Aging Computations

Within this part of the computation, the nonelastic elongation(i.e., conductor creep) of the conductors under the permanenttensile load is calculated for the operating conditions and con-ductor temperature defined during the mechanical computationpart.

Aging computations are divided into two clusters dependingon the type of conductor. The first one regards the well-estab-lished conductor types AAC, AAAC, ACAR, and ACSR and thesecond is in reference to the recently developed aluminum con-ductor composite reinforced (ACCR) and aluminum conductorcomposite core (ACCC) composite conductors [14], [40]. In thefirst cluster of computations, the predictor equations of Table Iare used under the prespecified designed operating conditions ofthe system [41]–[43]. These conditions are defined as follows.

• EDT and the ambient temperature at which this tensionoccurs as well as its predicted duration.

• Maximum operating conductor temperature, conductortension at that temperature, and its predicted duration.

TABLE ICREEP PREDICTOR EQUATIONS FOR DIFFERENT CONDUCTOR TYPES AT

NORMAL AND ELEVATED TEMPERATURES

• Conductor’s MCT at the designed ambient temperature atwhich this tension occurs and its predicted duration.

The computations include the prediction of elevated temper-ature creep (Table I) which occurs above 75 C for aluminumconductors and 100 C for the steel-reinforced conductors [42].

The second cluster of the aging computation is very similar tothe first one but instead of using the well-established predictorequations (Table I) adapted from [41], the stress-strain curvesproduced by testing the conductors are used in the absence ofstandard data. It should also be noted that the aging computa-tions use an iteration process, since the stress is reduced withtime as the creep strain gradually increases.

IV. IMPLEMENTATION OF THE METHODOLOGY

ON A REAL OHL SYSTEM

The methodology described in this paper is used to predictthe sag and identify the ampacity of a 400-kV L2-type latticetower OHL system after 29 years from the initial installationof the conductor. The system was strung with a twin-bundleRubus AL5 aluminum alloy conductor. The conductor’s elec-trical and mechanical properties are computed using the de-scribed methodology.

Table II shows the conditions relevant to the conductor’s in-stallation along with the surveyed and predicted sag values after29 years of the OHL’s operation. As can be observed, the sagprediction is very good and the calculated creep for the 29 yearsis 597.2 microstrains . The differences in span lengths be-tween the left and right circuits in the first and fourth spansare due to the use of angle towers at the tension points. Thisdifference in tower type results in nonparallelism of the con-tiguous tower cross-arms and, therefore, in different conductorspan lengths for the right and left circuits.


TABLE IISURVEYED DATA VALUES OF THE 400-kV OHL SYSTEM AND PREDICTED SAG

� Difference between the measured sag and the calculated predicted values.

TABLE IIIINPUT SURVEYED DATA FOR THE CURRENT FLOW CALCULATIONS

The ampacity calculations at the surveyed operating con-ductor temperatures resulted in similar values as those given bythe survey data for both circuits as illustrated in Table III. Thesag at 75 C (maximum electrical loading) is also calculated(Table II) and the catenary curve of the most critical span of thisOHL system is fitted on the conductor (surveyed) sag profile.This is illustrated in Fig. 5 and as can be seen, the conductorpreserves the 7.6 m of phase-to-ground required clearance [30],[44]. This, therefore, allows for higher operating conductortemperatures without the requirement of re-tensioning the con-ductor. Consequently, it enables increasing the line’s thermalrating, but with an increase in conductor creep that will becaused by the elevated operating temperature according to [41].In order to compute the new maximum operating temperature(and, therefore, the system’s ampacity), the calculations shouldbe performed again from the beginning and the estimatedamount of hours that the line would operate above 75 C shouldalso be specified. This step is important since the elevatedconductor temperature could affect the conductor aging and,thus, the ground clearance after a long period of the conductorin service.

V. GENERAL APPLICATION OF THE METHODOLOGY

The methodology discussed here links the conductor prop-erties with the properties defining the OHL structure in a way

Fig. 5. Surveyed profile of the critical span complemented with calculated cate-nary curves at surveyed and maximum electrical loading temperatures.

Fig. 6. Flowchart for choosing the appropriate technique for uprating thethermal limit of an aerial power system.

that enables investigating the benefits afforded by uprating tech-niques, such as re-tensioning and reconductoring, as illustratedin the flowchart in Fig. 6. It can also be used to evaluate the im-provement in performance that different conductor sizes and/ortypes may result in, and compares this with different conductorsand system operating conditions on a prespecified OHL system(Fig. 6). Hence, it enables the overall performance evaluationof lighter conductor technologies on a specified system, ratherthan comparing only their sag performances.

The methodology can then be used to compare the electricaland mechanical performance of different conductors for thesame OHL structure and identify the one that allows more elec-trical power to be transferred through the specified structureand evaluate the losses. Changes in the OHL structure causechanges in the system and, thus, the performance of the sameconductor would be different. Weather changes (e.g., ambienttemperature, maximum wind speed, etc.) also influence theperformance of the overall system.


This methodology can be used to identify the effect of in-crease in operating temperature as well as the impact of vibra-tion dampers on the conductor or the effect of increases in am-bient temperature (due to global warming) [45]. Furthermore, itcan be used to identify the effect of changes on the OHL design(i.e., increasing the height of the conductor attaching points ortheir maximum tensile strength). It can also compute the addi-tional creep effect caused by the initial overtension applied tonegate the conductor’s plastic deformation.

The electrical computation section addresses all of thebimetallic conductors and with small modifications in thespiraling factors, skin effect, and magnetization factor, it canalso be used for composite core conductors with or withoutconductive cores (i.e., the conductors in [40] and [14]). Con-sequently, it increases the flexibility of the calculations at anytemperature for any conductor technology and design (evenfor those for which the properties are known but still not fullydeveloped), and allows the direct comparison of the perfor-mance of different conductor sizes and technologies on thesame OHL structure. For example, modeling the performanceof the different nonexisting ACCC/TW core to aluminumratio conductors can be performed to find the optimal fit for aparticular OHL system at a given location.

This methodology has already been used to show how dif-ferent conductor technologies behave in standard U.K. OHLstructures [45]–[49], highlighting the potential of reconduc-toring with novel HTLS conductors.

VI. CONCLUSION

The current rating and sagging performance of a conductorerected on an OHL structure are influenced by the weather,the conductor, and its installation method, the OHL structure,and operational conditions. The methodology presented in thispaper links all of these parameters together in order to evaluatethe actual performance of a conductor on a prespecified struc-ture. It enables performance comparison of different conductortypes and sizes on the same structure. This is important since,in some cases, the structure limits the conductor’s performance.The accuracy of this methodology in predicting conductor sagand current flow is also evaluated. The validation process with afour-span double-line system resulted in correct predictions forthe 29-years operation time.

The main contribution of this methodology is the flexibilityon calculating the conductor properties rather than obtainingthem from a database as well as incorporating OHL structureconstraints (weight and tension). It can be used to evaluate po-tential uprating by reconductoring, and increased temperatureof operation by retensioning on a given line. Furthermore, itcan help with the choice of the most suitable conductor fora given system and, thus, identify the best option in terms ofconductor size and technology type, suggesting new conductordesigns/sizes.

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Konstantinos Kopsidas (M’06) was born in Lefkas,Greece. He received the B.Eng. degree in electricaland electronic engineering from The University ofManchester Institute of Science and Technology(UMIST), Manchester, U.K., in 2004, and theM.Sc. (Hons.) degree in electrical power systemengineering, and the Ph.D. degree in electrical powerengineering from The University of Manchester,Manchester, U.K., in 2005 and 2009, respectively.

He was a Research Assistant/Associate with theSuperGen V (AMPerES) and is now a Lecturer with

the School of Electrical and Electronic Engineering, The University of Man-chester, also collaborating with Arago Technology Ltd., Manchester, U.K.

Dr. Kopsidas received the Scottish Power “Power Learning Award” and theUMIST course prize twice.

Simon M. Rowland (SM’07) was born in London,U.K. He received the B.Sc. degree in physics fromthe University of East Anglia and the Ph.D. degreefrom London University, London, U.K.

He has worked for many years on dielectricsand their applications. He has also been Operationsand Technical Director within multinational man-ufacturing companies. He joined The School ofElectrical and Electronic Engineering, The Univer-sity of Manchester, Manchester, U.K., as a SeniorLecturer in 2003. He was appointed Professor of

Electrical Materials in 2009.Dr. Rowland received the IEE Duddell Premium Award in 1994 and became a

Fellow of the Institute of Electrical Engineers in 2000. Currently, he is Presidentof the IEEE Dielectric and Electrical Insulation Society.

Boud Boumecid received the M.Sc. degree incivil engineering from the University of Salford,Manchester, U.K., in 1994.

He previously worked with consultants andcontractors, where he was involved in the civil andstructural design of power stations, substations, andoverhead lines. He is a Design Engineer (OverheadLines) with the Electricity Network InvestmentDepartment—Asset Policy, National Grid, U.K.

Mr. Boumecid is an active member of CIGREStudy Committee SC B2 (Working Group 23 on

Foundations) and of the BSI-PEL/011 Committee.

A Holistic Method for Conductor Ampacity and Sag Computation on an OHL Structure

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