FP_C.1_LEADER_HIGH TEMPERATURE LOW SAG (HTLS)
OVERHEAD TRANSMISSION LINE CONDUCTOR
Nabil Bin Ahmad Nasuruddin, Leader Cable Industry Berhad, Unit 8.2, Level 8 Building A, Dataran PHB,
Saujana Resort, Seksyen U2, 40150 Shah Alam, Selangor, Malaysia, 0127911828, nabil@leadercable.com.my
Azhar Bin Ariffin, Leader Cable Industry Berhad, Lot 1385, Tikam Batu Indutrial Estate, 08600 Sungai Petani,
Kedah, Malaysia, 0127905616, azhar@leadercable.com.my
Ryuta Ogoshi, Tokyo Rope International Inc., 3-6-2 Nihonbashi, Chuo-ku, Tokyo, 103-8306, Japan,+81363667731, ogoshi.ryuta@tokyorope.jp

ABSTRACT
Overhead conductor is the key component of power transmission to ensure efficient, reliable and sustainable
power network system. Brisk increase of electricity demand imply the need of more power to be generated andtransmitted. Building a new power transmission network is an obvious solution but it is also involves costly andlengthy processes. It takes in several major issues such as high construction cost, delay from right of way
matters and gloomy impact on natural environment. The best alternative solution is reconductoring the overhead
power transmission lines with High Temperature Low Sag (HTLS) conductor which able to cater double theAmpacity requirement. This initiative could accommodate the higher power requirement which in returnprovide a cheaper and faster solution to utilities by maintaining the usage of existing towers. The prevailingconventional Aluminium Conductor Steel Reinforced (ACSR) conductor has several weak points which include
large thermal expansion and heavy steel core with higher corrosion rate. On the contrary, the eccentric
conductor of HTLS could operates at higher temperature and double the Ampacity with lower Differential
Ohmic Loss operation cost. It offers a higher transmission capacity with low transmission loss due to its uniquetrapezoidal shaped aluminium conductor wires. HTLS conductor core is also made from a special strandedcarbon fibre composite cable which is lighter, low expansion, higher strength, non-magnetic, high flexibility,
high corrosion resistance, high tensile, low creep elongation and high modulus compared to the steel core ofstandard ACSR. In conclusion, the insistent needs to increase the transmission network Ampacity on theexisting power transmission line towers which also could offers lesser conductor sags made possible with theapplication of the exceptional attributes of HTLS overhead conductor.
KEYWORDS HTLS, ACSR, RECONDUCTORING, AMPACITY, SAG,

1. INTRODUCTION
High Temperature Low Sag (HTLS) conductor is the preferable latest technology conductor particularly forreconductoring transmission line to accommodate the rapid increase of demand to transmit more power. HTLS
helps to bring the best out of reconducturing transmission line activities through it exceptional technicalattributes. It offers double the Ampacity and lower sag at fundamentally similar weight of conventional
Aluminium Conductor Steel Reinforced (ACSR), hence it makes possible to do reconductoring on existingtransmission lines towers while having same conductor to earth clearance. Overtime, HTLS conductor also has
progressed with an improved core construction that eventually enhanced its mechanical characteristics. By using
stranded carbon fiber composite cable (CFCC) as the core, it has made HTLS becoming more advance under thedesign of Aluminium Conductor Fibre Reinforced (ACFR). HTLS conductor also offer an effective solution fortransmission line issues such as high construction cost, delay from right of way matters and gloomy impact onnatural environment.
2. MAIN CONTENTS
2.1 CONSTRUCTIONHTLS made of two components, trapezoidal shaped aluminum conductor wires and fiber core. ACFR offered
Carbon Fiber Composite Cable (CFCC) as the stranded shape core. Figure 1 shows the cross sectional drawingof ACFR HTLS conductor. Figure 2 shows the telescopic sample of ACFR HTLS conductor.

1

Figure 1. Conductor Cross Sectional Area Structural Drawing of Aluminium Conductor Fibre Reinforced(ACFR) type of HTLS

Figure 2. Aluminium Conductor Fibre Reinforced (ACFR) type of HTLS

2.12 Trapezoidal Shaped Aluminium Conductor
The conductor is made of trapezoidal shaped of annealed aluminium wire by stranding pre-shaped annealed
aluminium wires into wedges-like to fit tightly to each other to reduce the interstice between strands and havesmaller conductor diameter but larger cross section area.
2.13 Carbon Fiber Composite Cable (CFCC) Core
The raw material carbon fiber and epoxy resin matrix are bunched together to form a composite wire and arestranded Carbon Fiber Composite Cable (CFCC coated with organic layer act as galvanic protection and thus
formed single carbon fiber composite wires are stranded together to form a). The single strand size can bechosen to match the final CFCC diameter suitable for ACFR conductor that replaces the existing conventional
ACSR conductor. CFCC has the same advantage as that of the single carbon fiber composite core like higher
strength, lower weight, lower thermal expansion and higher corrosion resistance. But the unique stranded carbon
fiber composite core CFCC accommodate the challenge of flexibility and handling issues in the single strand
carbon fiber composite core.
2

2.2 MANUFACTURING
Manufacturing of ACFR HTLS conductor starts with pulling of annealed aluminium rod through a series ofdrawing dies to obtain trapezoidal aluminium wires of desired dimension, this process is called wire Drawing.
The aluminium rod is pulled through a series of dies to reduce the cross section and to obtain a certain size. Thisdrawing of trapezoidal wires are precise and delicate in order to handle the aspects of draw down ratio, frictionand elongation. Hence proper control of payoff tension, correct sizing of guide rollers and precise sizing of dies
position in the correct sequence are needed. While it is being drawn, the wire continuously undergone natural
annealing process through the stages of shaping rollers and drawing dies. At the end of the wire drawing line,
there is a take up where output wire is rolled into a processing bobbin and would be ready for the next stage ofprocess called Stranding.
At a time, 20 bobbins containing drawn aluminium trapezoidal shape wires are prepared (first layer x 8wires +second layer x 12 wires). After that it goes to the main manufacturing process of Stranding by applying
trapezoidal aluminium wires concentrically around/over the CFCC core to form the complete ACFR conductor.
The stranding machine includes a core feeder, a first stranding cage, first two-set of shaping rollers, a first dieset, a second stranding cage, second two-set shaping rollers, a second die set, a length counter, a capstan and adrum take up. 8 bobbins are loaded in the first stranding cage representing the first layer of conductor. Whilerotating, the first stranding cage strands on top of the fiber core. It is highly crucial to set and control the payoff
tension of each bobbin of the first cage so that the first layer of wire conductor that stranded around the fed
carbon core has a firm contact and grip but just enough, without putting too much compression to avoid
crushing the fiber core. After first layer of trapezoidal stranded over the fiber core and gone through the first dieset, it fed to the second stranding cage. Second layer that consist of 12 trapezoidal wires stranded over the firstlayer of the conductor and fed through the second die set to produces a complete conductor. The length countermeasures the lengths of the completed conductor by a wheel form. The capstan pulls the completed conductor
with a certain tension and twisted at a predetermined angle to prevent the displacement of the conductor. Finallythe conductor pulled by the drum take up and rolled the complete conductor in to a drum. The drum take up isequipped with a traverse device to achieve winding alignment. In addition to the in-process inspection, electrical& non-electrical test are performed on the completed products before final packaging and delivery.

Figure 3. ACFR HTLS Conductor Manufacturing Process
2.3 CHARACTERISTIC ADVANTAGES
2.31 Larger Transmission Capacity - Double Ampacity:
The selection of materials for transmission conductor design depends on the combination of both conductor andits core electrical and mechanical attributes. ACSR conductor is made of aluminium alloy to achieve higher
tensile strength. For that, stranded galvanised steel wire core is sufficient for ACSR conductor to comply certain
limit of conductor sagging to maintain the clearance between the conductor and earth at certain hightemperature. Aluminium alloy conductor however has lower current carrying capacity due to high resistancecaused by impurities of aluminium. Operating at higher current will increase the conductor temperature.
Operating ACSR that having aluminium alloy as its conductor beyond its normal operating temperature of3

between 70oc to 90oc will start to anneal the aluminium to become soften. The annealing will deteriorates thetensile strength and potentially could cause the conductor to break especially under high wind condition. Thus,
the normal operating temperature for ACSR is usually limited to 75oc to avoid the problem which eventually
will also limit the current carrying capacity. It is vice versa to limit the current carrying capacity to avoid theincrease of conductor temperature beyond its normal operating temperature that could cause conductor
breakage. The objective of reconductoring is to increase up to double the transmission line ampacity using thesame existing towers while complying the conductor sagging limitation. This could be achieved by replacing theconventional ACSR conductor with ACFR HTLS conductor. HTLS uses trapezoidal shape conductor of soften
aluminium also known as annealed or ‘O’ temper aluminium. The conductivity of annealed aluminium is higher
than aluminium alloy conductor. It is clearly more efficient in transmitting power. On top of that, operating
HTLS conductor that uses annealed aluminium at higher temperature virtually resulted no further effect on thealuminium’s tensile strength. As HTLS conductor depends on the CFCC as the tensile strength member wouldable to sustain higher operating temperature, eventually it increase its capability to transmit more current. Unlike
ACSR, predictable installation parameters could be determined for HTLS when taking into account of sagging
and tension performance at higher temperature. On the other hand, though it is known that the tensile strength of
ACSR’s aluminium alloy conductor is approximately three times more compared to HTLS’s annealed
aluminium conductor, ACFR HTLS annealed aluminium conductor is supported by higher tensile and strength
core of stranded Carbon Fiber Composite Cable (CFCC). Table 1 shows the comparison between ACSR Batangand ACFR HTLS Hen conductor construction and capabilities.
Table 1. Comparison between ACSR Batang and ACFR Hen of Construction and Capabilities
ACFR HEN
Item
Characteristic
Unit
ACSR Batang
7.8φ core Annealed
Material
Hard-drawn Aluminum Annealed Aluminum
Aluminium
Construction
No./mm
18/4.78
8/(4.6), 12/(4.6)
Shape of Aluminum
Round
Trapezoid
Area
mm2
323.0
332.4
Weight
kg/m
0.889
0.916
Material
Galvanised steel wire
CFCC
Core
Construction
No./mm
7/1.68
7/2.6
Area
mm2
338.5
369.6
Overall
Diameter
mm
24.16
22.42
Weight
kg/m
1.014
0.977
*Rated Breaking Load
kN
69.7
93.7
0.08920.0836
Calculated DC resistant at 20℃ Ohm/km** Current
A
617
1235
Continuous
Capacity(at 75℃)(at 180℃)
A
N/A
1308
Emergency(at 200℃)(at 200℃)***Sagging @ span of 300m
m
7.19
6.96
- 32 degC Still Air (Sag)
kN
15.49
15.49
(Tension)(at 32℃)(at 32℃)- 75 degC Still Air (Sag)- 90 degC Still Air (Sag)

m
m

8.89
(at 75℃)
9.43(at 90℃)

8.45(at 75℃)
8.78(at 90℃)

2.311 Higher Maximum Operating Temperature
The maximum operating temperature for conventional ACSR is 70oc to 90oc. On the other hand, HTLS
conductor uses high thermal resistance EC grade annealed aluminium wires that could withstand temperature up
to 180oc. If compare to ACSR, HTLS could endure double the maximum operating temperature. Hence, HTLS
4

conductor could transmit virtually double the ampacity having this higher thermal limit of conductor on top of
another two following factors of lower conductor resistance and larger conductor cross sectional area that
contributes to higher current carrying capacity.
2.312 Large Conductor Cross Sectional Area
HTLS with its trapezoidal conductor shape has a larger area compared to stranded round wires of ACSR
conductor. HTLS’s trapezoidal-shaped annealed aluminium conductor made by stranding pre-shaped annealed
aluminium wires into wedges-like to fit tightly to each other and reduce the gap between strands and maximised
the conductor cross sectional area. Unlike ASCR conductor that uses aluminium alloy round wires that stranded
in typical round shape, the conductor left with significant interstice between aluminium wires. This reflect tohigher conductivity for HTLS conductor and contributes to higher current carrying capacity.
2.313 Lower Transmission Loss
The transmission loss expected from HTLS is 27% less than that of similarly sized ACSR because of theincreased content of pure aluminium, effectively zero magnetic loss and high electrical conductivity.
2.32 Low Sag:
2.321 Light Weight, High Strength & High Tensile Fatigue
The second important characteristic for HTLS conductor is its low sag attribute. Sagging is a very importantparameter to be considered in network design as it is related to safety concerns. Sagging aspect is the clearanceof the conductor to the ground is an intrinsic property requirement of the overhead conductor. Hence, correct
selection of material and design to be used as the tensile member in the conductor would be the ultimate
requirement. ACSR has a stranded steel wire material for its core but HTLS uses lighter and higher strengthcarbon fiber composite instead. This advantages enhance in ACFR HTLS conductor as the core uses Carbon
Fiber Composite Cable (CFCC) which consist of 7 stranded carbon fiber composite wires instead of one single
solid carbon fiber for its core. Table 1 shows the comparison of conductor sagging between ACSR Batang and
ACFR HTLS Hen at 32oC, 75oC and 90oC where ACFR HTLS Hen sagging reading are the lowest for all set
temperature. Table 2 shows the properties comparison between CFCC core and Galvanised Steel Wire core.
Table 2 shows the comparison between CFCC core for ACFR HTLS and Galvanised Steel Wire Core for ACSR
construction and performance.
Table 2. Comparison between CFCC core for ACFR HTLS and Galvanised Steel Wire Core for ACSR

2.322 Low Linear Expansion
Another ACFR HTLS attribute that contribute to its low sag characteristic is its lower density and low
coefficient of thermal expansion (CTE). Compared to galvanised steel wire core of ACSR, CFCC core for
ACFR HTLS has only one-tenth the thermal expansion coefficient with only one-fifth the weight but higher
tensile strength.
2.323 Low Creep Elongation
HTLS has a low tendency to deform though exposed to a long-term high levels of stress. Figure 2 shows theresult of Creep Test for Type Test on ACFR HTLS 320mm² Hen ACFR/TW HEN Conductor conducted at5

Kinectrics Lab, Canada, a log-log plot of conductor strain versus elapsed time. The long-term tensile creep of aconductor under constant tension is taken to be the permanent strain occurring between one (1) hour and thespecified test time. The specified test time for the Creep Test was 1,000 hours. This trend-line was thenextrapolated to ten(10) years (87,600 hours). The equation of the line is:
Strain= A x (Hours)B
where A = Y- Intercept = 1.2069E-02 %B = Slope = 0.19650
The initial creep value (defined at 1 hour) using the fitted line is:(Strain at 1 hr) = 1.207E-02 %The creep during the test using the fitted line is:(Strain at 1000 hr) - (Strain at 1 hr) = 4.690E-02 - 1.207E-02 = 3.483E-02 %The 10-year ( 87,600 hrs) creep using the fitted line is:(Strain at 87,600 hr) - (Strain at 1 hr) = 1.129E-01 - 1.207E-02 = 1.009E-01 %The calculated creep after ten (10) years (87,600 hours) is 0.1009 % or 1009 mm/km.

Figure3. Conductor Strain versus Time2.33 High Corrosion Resistance
HTLS Conductor core is made from carbon composite fiber that has high corrosion resistance compare togalvanised steel wire core for the conventional ACSR. Although the steel core is galvanized to prevent
corrosion, the conductor is subject to degradation. When the conductor is penetrated by a contaminant, it causes
corrosion of the galvanizing, and then exposes the steel strands to form a galvanic couple with the aluminum.
The aluminum begins to degrade rapidly, reducing its current carrying capability and eventually leading to themechanical failure of the conductor. Atmospheric conditions also affect corrosion on the steel strands and insevere cases, the deterioration in the steel core strands performance will lead to strand breakage and line failure.
Over time, the steel strands core that support the mechanical load of the transmission line also can cause
permanent elongation and reduce the mechanical performance of the lines. With stranded CFCC core for ACFRHTLS conductor, this potential failure could be highly reduced. Table 4 and 5 show the result of Tensile
Strength Test after Salt-Spray Exposure for Type Test on ACFR HTLS 320mm² Hen ACFR/TW HEN
Conductor conducted at Kinectrics Lab, Canada. The measured tensile strength of the stranded CFCC core andaluminum wire samples should not be less than 95% of RTS after completing the 1,000 hour salt spray
exposure.
6

Table 4. Mass of Samples during Salt Spray Test

Table 5. Tensile Strength Test Results after Salt-Spray Exposure

2.34 High Flexibility
ACFR HTLS conductor with a stranded carbon fibres core is highly flexible so that it can be wound around asmaller drum for easy packaging, transporting and handling. It has high bending angle with smaller diameter ofstringing sheave which contributes to less number of stringing works. Table 3 shows the result of Sheave Test
for Type Test on ACFR HTLS 320mm² Hen ACFR/TW HEN Conductor conducted at Kinectrics Lab, Canada.
Table 3. Diameter Measurements during Sheave Test

2.35 Low Differential Ohmic Loss & Reduction of CostHTLS conductor has a low differential ohmic loss when in operation. This contributed by low resistance of theannealed aluminium conductor even at double the ampacity compare to ACSR. The usage of non-magnetic
stranded Carbon Fiber Composite Cable (CFCC) core in ACFR HTLS conductor instead of galvanised steel
wire core in the conventional ACSR also further reduce the differential ohmic loss. The reduction of differential
ohmic lost value could be added and justified as a cost saving projection in a long run to the total overall projectand operating cost. This is on top of cost saving on eliminating or reducing the requirement of new towers, rightof way process and manpower by using ACFR HTLS conductor for reconductoring.

7

3.CONCLUSIONHTLS conductor has many advantages and is the best choice for power transmission overhead lines be it on new
overhead system network or specially when involving reconductoring activities. HTLS offer double theampacity through it trapezoidal annealed aluminium conductor design that could sustain virtually double themaximum operating temperature of the same size of the conventional ACSR conductor. On top of that, HTLS ishaving larger conductor cross sectional area and eventually lower transmission loss. HTLS low sagcharacteristic enhance through the design of ACFR HTLS conductor that uses stranded Carbon Fiber Composite
Cable (CFCC) for its core. It is lighter, lower thermal expansion, high strength but in fact more flexible than the
single carbon composite core. Thus, by using ACFR HTLS conductor for reconductoring, the objective ofobtaining double ampacity in power transmission overhead lines by using existing power transmission line
towers while maintaining the same good ground clearance is achievable.
4. RECOMMENDATION
We highly recommend the usage of HTLS conductor especially the ACFR HTLS conductor with stranded
Carbon Fiber Composite Cable (CFCC) core that has more advance characteristics for reconductoring existingtransmission lines or even for erecting new grid projects. The high technology of stranded Carbon Fiber
Composite Cable (CFCC) core contributes for the ACFR HTLS conductor to have superior long term
performance, cost effective, durability and reliability to accommodate double ampacity for transmission lines
compare to conventional ACSR conductor. ACFR HTLS conductor also contributes to project cost reduction
and fast completion through its attributes that make the usage of existing towers possible. In due course, it
minimizes the cost from right of way matters and avoid the negative impact on natural environment. As forerecting new transmission lines, with the high ampacity and low sag capabilities, ACFR HTLS conductor isgreatly relevant for decades in term of current carrying capacity and mechanical reliability.
5. REFERENCE[1] Type Tests On ACFR/TW Condcutor and CFCC Core For Leader Cable Industry Berhad & Tokyo Rope
Manufacturing Company, Tests On 320 MM² ACFR/TW Hen Conductor, 2018-Apr-12.
[2] F. Sato and H. Ebiko, Development of a Low Sag Aluminum Conductor Carbon Fiber Reinforced forTransmission Lines. CIGRE 22-203, 2002.
[3] Y. Ohki, Development of a Low Sag Aluminum Conductor Carbon Fiber Reinforced for Transmission
Lines. IEEE Electrical Insulation Magazine, November/December — Vol. 33, No. 6.
[4] Ahmad Alawar, Eric J. Bosze, and Steven R. Nutt, A Composite Core Conductor for Low Sag at High
Temperatures. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 20, NO. 3, JULY 2005.
[5] Ogoshi Ryuta, Revamped High Ampacity Low Sag Stranded Carbon Fiber Composite Core – Aluminium
Conductor Fiber Reinforced Conductor (ACFR). CIGRE TR/01/18, 2018.
[6] Neal Murray, Fabien Besnard, Drew B. McGuire and Kuni J. Scissum, Conductor Corrosion Inspection of
Aluminum Conductor Steel Reinforced Transmission Lines. 978-1-5090-2157-4/16 ©2016 IEEE
[7] Somboon Nuchprayoon and Artitaya Chaichana, Cost Evaluation of Current Uprating of Overhead
Transmission Lines Using ACSR and HTLS Conductors. 978-1-5386-3917-7/17/ ©2017 IEEE

8