Definitions & References
(click for references)
AAAC - All Aluminium Alloy Conductor.
ACAR - Aluminium Conductor Alloy Reinforced.
ACSR - Aluminium Conductor Steel Reinforced.
ACSS - Aluminium Conductor Steel Supported - A stranded conductor made up of fully annealed aluminium strands over a core of steel strands.
Ampacity - The ampacity of a conductor is that maximum constant current which will meet the design, security and safety criteria of a particular line on which the conductor is used. In this brochure, ampacity has the same meaning as “steady-state thermal rating.”
Annealing - The process wherein the tensile strength of copper or aluminium wires is reduced at sustained high temperatures.
ASTM - American Society for Testing and Materials.
Electrical Clearance - The distance between energised conductors and other conductors, buildings, and earth. Minimum clearances are usually specified by regulations.
EC (grade aluminium) - Electrical Conductor grade aluminium also called 1350-H19 alloy or A1.
EHS Steel - Also designated S3. Extra High Strength steel wires for ACSR.
GTACSR - Gap- type TAL aluminium alloy Conductor, Steel Reinforced.
HS Steel - Also designated S2. High Strength steel core wires for ACSR.
I.A.C.S. or IACS - International Annealed Copper Standard.
IEC - International Electrotechnical Commission.
Invar Steel - A steel core wire made with high Nickel content to reduce the thermal elongation coefficient.
Knee-point Temperature - The conductor temperature above which the aluminium strands of an ACSR conductor have no tension or go into compression.
Maximum Allowable Conductor Temperature - The highest conductor temperature at which an overhead power line can be safely operated.
RBS - Rated Breaking Strength of conductor. A calculated value of composite tensile strength, which indicates the minimum test value for stranded bare conductor. Similar terms include Ultimate Tensile Strength (UTS) and Calculated Breaking Load (CBL).
Ruling (Effective) Span - This is a hypothetical level span length wherein the variation of tension with conductor temperature is the same as in a series of suspension spans.
SDC - Self-Damping Conductor is an ACSR conductor wherein the aluminium strands are trapezoidally shaped and sized such that there is a small gap between layers to allow impact damping of aeolian vibration.
T2 - Twisted Pair conductor wherein two ordinary round stranded conductors are twisted around each other to enhance mechanical stability in wind.
TACIR - TAL Aluminium Alloy Conductor reinforced with an Invar steel core.
TACSR - TAL Aluminium Alloy Conductor reinforced by a conventional stranded steel core.
TAL – (“Thermal-resistant aluminium”) An aluminium zirconium alloy that has stable mechanical and electrical properties after continuous operation at temperatures of up to 150oC.
Thermal Rating - The maximum electrical current, which can be safely carried in overhead transmission line (same meaning as ampacity).
TW conductor - A bare overhead stranded conductor wherein the aluminium strands are trapezoidal in cross-section.
Uprating - The process by which the thermal rating of an overhead power line is increased.
Weight - This brochure generally uses conductor in weight per unit length. Mass per unit length can be obtained by dividing by the acceleration of gravity (approximately 9.81 m/sec2).
“Worst-case” weather conditions for line rating calculation - Weather conditions which yield the maximum or near maximum value of conductor temperature for a given line current.
ZTAL – (“Super Thermal-resistant aluminium”) An aluminium zirconium alloy that has stable mechanical and electrical properties after continuous operation at temperatures of up to 210oC.
ZTACIR - ZTAL aluminium alloy conductor reinforced by an Invar steel core.
[1] “Probabilistic determination of conductor current ratings.” SC22-12 Electra number 164 February 1996 page 103-119.
[2] “The Use of Weather Predictions for Transmission Line Thermal Ratings”, WG22.12 Electra No. 186, October 1999.
[3] C.F. Price & R.R. Gibbon “Statistical Approach to Thermal Rating of Overhead Lines for Power Transmission and Distribution”, IEE Proceedings, Vol 130, Pt C, No 5, September 1983.
[4] V.T. Morgan, “Probability Methods for Calculating the Current Capacity of Overhead Transmission Lines”, Proc. Inter. Symp. on Probabilistic Methods Applied to Electric Power Systems,
[5] “Methods for real-time thermal monitoring of conductor temperature” Electra N° 197 – August 2001.
[6] Y. Motlis, D.A. Douglass, & T.O. Seppa: “IEEE’s Approach for Increasing Transmission Line Ratings in
[7] D.A. Douglass & A. Edris: “Field Studies of Dynamic Thermal Rating Methods for Overhead Lines”, IEEE T&D Conference Report,
[8] T.O. Seppa & al: “Use of On-Line Tension Monitoring for Real-time Thermal Ratings, Ice Loads, and Other Environmental Effects”, CIGRE 22-102,
[9] Electra Article, “Thermal Behaviour of overhead conductors” – Working Group 22.12, number 203, August 2002, pp. 70-73 [also Brochure 207].
[10] "Safe design tensions with respect to aeolian vibrations. – Part I – single unprotected conductors" Electra Vol 186, Oct 1999.
[11] "Safe design tensions with respect to aeolian vibrations. – Part II – Damped single conductors with dampers" Electra Vol 198, Oct 2001.
[12] T. Varney, “ACSR Graphic Method for Sag-Tension Calculations”, 1927.
[13] Aluminium Association handbook, 2nd Edition, 1981.
[14] J.S. Barrett, S. Dutta, O. Nigol, “A New Computer Model of ACSR Conductors”, IEEE Trans., vol.PAS-102, no.3, March 1983, pp.614-621.
[15] Nigol & J.S. Barrett: “Characteristics of ACSR Conductors at High Temperatures and Stresses” IEEE Transcat. Vol. PAS 10, No. 2, February 1981, pp. 485-493.
[16] C.B. Rawlins: “Some Effects of Mill Practice on the Stress-Strain Behaviour of ACSR”, IEEE WPM 1998,
[17] Douglass, D.A., “Field Studies of dynamic Thermal Rating Methods for Overhead Lines”, Proceedings of the IEEE T&D Conference, New Orleans, LA, April, 1999.
[18] V.T. Morgan & G.K. Geddey: “Temperature Distribution within ACSR Conductors” CIGRE 22-101,
[19] D.A. Douglass: “Radial and Axial Temperature Gradients in bare Stranded Conductors.” IEEE Trans. On Power Delivery, Vol. PWRD-1, No. 2, April 1986, pp 7-15.
[20] A.R. Rosenfield & B.L. Averbach. “Effects of Stress on the Expansion Coefficient”, Journal of Applied Physics, Vol. 27, No. 2, February 1956.
[21] J.R. Harvey & R.E. Larson: “Creep Equations of Conductors for Sag – Tension Calculations” IEEE CP 72 190-2,
[22] CIGRE WG 22.05 (12), "Permanent Elongation of Conductors. Predictor Equations and Evaluation Methods", Electra, No. 75, pp. 63-98, March 1981.
[23] Electra Article “Loss in Strength of Overhead Electrical Conductors Caused by Elevated Temperature Operation”, number 162 October 1995 page 115-117.”
[24] IEEE WG on Thermal Aspects of Overhead Conductors: “Limitations of the Ruling Span Method for Overhead Line Conductors at High Operating Temperatures”, IEEE PE-197-PWRD –0-12-1997.
[25] M.J. Tunstall et al: “Maximising the Ratings of National Grid’s Existing Transmission Lines Using High Temperature, Low Sag Conductor”, CIGRE 22-202,
[26] D.O. Ash et al “Conductor systems for overhead lines: some considerations in their selection”, Proceedings IEE, Vol. 126, no.4, April 1979, pp. 333-341.
[27] P.G. Malburg “Structural selection of ACSR for Transmission Lines”, AIEE Transactions, Volume 76, Part III, pp. 910-918, December, 1957.
[28] “IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors”, IEEE Std 738-1993,
[29] V.T. Morgan, “Effect of Elevated Temperature Operation on the Tensile Strength of Overhead Conductors”, IEEE Trans. on Power Delivery, Vol. 11, No. 1, pp. 345-352, January 1996.
[31] M.J. Tunstall, “Increasing the Ratings of NGC’s Lines in the
[32] A.E. Livingston, “Aluminium Alloy Conductors for Overhead Transmission and Distribution Lines”, CEA Paper, presented
[33] T. Saito et al, “Spiral-Elliptic Conductor with Low Drag Coefficient”, IEEE Power Engineering Society Winter Meeting,
[34] M. Gaudry, F. Chore, C. Hardy, E. Ghannoum, “Increasing the Ampacity of Overhead Lines Using Homogeneous Compact Conductors”, Paper 22-201, CIGRE Session Paris 1998.
[35] P. Couneson et al, “Improving the Performance of Existing High-Voltage Overhead Lines by Using Compact Phase and Ground Conductors”, Paper 22-209, CIGRE Session Paris 1998
[36] A.E. Livingston, “Self-damping conductors for the control of aeolian vibration of transmission lines”, CEA Paper 70-TR-225, presented October 1969,
[37] A.R. McCulloch, et al, “Ten Years of Progress with Self-Damping Conductor”, IEEE Transactions on Power Apparatus and Systems, Vol.PAS-99, no.3, May/June, 1980, pp.998-1011.
[38] J.B.Roche, D.A.Douglass, “T2 Wind Motion Resistant Conductor," IEEE Paper No. 84 WM 203-5, T-PAS, Vol. PAS-104, No. 10, October, 1985, pp. 2879-2887.
[39] Kotaka, S., et al, “Applications of Gap-Type Small-Sag Conductors for Overhead Transmission Lines”, SEI Technical Review, Number 50, June, 2000.
[40] Sasaki, S. et al, “ZTACIR-New Extra-Heat Resistant Galvanized Invar-Reinforced aluminium alloy conductor”, Sumitomo Electric Technical Review, Number 24, January, 1985.
[41] ASTM B856-95, “Standard Specification for Concentric-Lay-Stranded Aluminium Conductors”, Coated Steel Supported (ACSS).
[42] ASTM B857-95, “Standard Specification for Shaped Wire Compact Concentric-Lay-Stranded Aluminium Conductors”, Coated Steel Supported (ACSS/TW).
[43]
[44] Thrash, F.R., “ACSS/TW – An Improved Conductor for Upgrading Existing Lines or New Construction”, 1999 IEEE T&D Conference, New Orleans, LA, April 11-16, 1999.
[45] Hoffmann, S.P., Tunstall, M.J., et al, “Maximizing the Ratings of National Grid’s Existing Transmission Lines Using High Temperature, Low Sag Conductor”, Paper 22-202, CIGRE Session
[46] F. Jakl, A. Jakl: Effect of Elevated Temperatures on Mechanical Properties of Overhead Conductors under Steady State and Short-Circuit Conditions, IEEE Transactions on Power Delivery, 2000, Vol. 15, No. 1, pp. 242-246.
[47] V. T. Morgan: Effect of Alternating and Direct Current Power Frequency, Temperature, and Tension on the Electrical Parameters of ACSR Conductors, IEEE Transactions on Power Delivery, 2003, Vol. 18, No. 3, pp. 859-866.