Everything you need to know about ACAR Conductors
Though being in the market for several years now, ACAR conductors still confuse many about their application and what exactly the ACAR conductors are. This article comprises everything that you need to know about ACAR conductors, starting from their definitions of their productions to their applications.
What is ACAR Conductor?
The use of Aluminum for making electrical conductors is now universally established. With the rapid growth in power-efficient conductors, industrialization, and electrification, the demand is met by aluminum conductors along with other conventional conductors. The previous two major types of Aluminum conductors were ACC (All Aluminum conductors) and ACSR (Aluminum Conductors Steel Reinforced). The new and much more efficient player in the aluminum conductor market is the ACAR conductor. ACAR is an acronym Aluminum Conductor Alloy Reinforced. For a given length, these conductors require less quantity of Electric Conductor (EC) Aluminum, and the requirement of galvanized steel is completely eliminated. These ACAR conductors are most likely to substitute almost all types of ACSE and ACC conductors in the near future.
ACAR conductor is a type of high-strength and high capacity stranded conductor that is commonly used in overhead powerlines. In the ACAR conductor configuration, the center strand of the cable is made of Aluminum alloys whereas, the outer strands are manufactured with high-quality aluminum. ACAR conductors have various industrial applications and benefits, which will be discussed further in this article.
Construction of ACAR conductors
ACAR conductors are manufactured with concentric-lay-stranded conductors that are made from round aluminum 1350-H19 extra hard wires and round aluminum alloy 6201-T81 wires. Typically, the ACAR conductors are available in multi-layer and single constructions. The temper of the aluminum core is defined by the materials version’s suffix, which in the case of ACAR H19, is extra hard. To extend the life of the aluminum cores used in ACAR conductors, the cores are normally galvanized or in some wires, coated with other materials to prevent corrosion or damage. The strands of both the aluminum and its cores are different for different ACAR conductors.
Since ACAR conductors do not have any steel components in them, their strength can be controlled by selecting the right number of alloy strands in the cable. By carefully selecting the right alloy for the ACAR conductor, the manufacturers can lower the weight of the cables by as much as 25%. Statistical reports have shown that ACAR conductors tend to be lighter and better than the ACSR (Aluminum conductor Steel Reinforced) conductors. The design consideration of ACAR cables such as the span, sag, and tower size can be calculated via;
|W = Weight of the conductor (kg/m)
|S = Sag of the conductor (m)
|H = Horizontal tension in conductor (kg)
|L = Length of span (m)
The ACAR conductors can be manufactured in many different setups, and it is up to the customer on what type of configuration they are looking for. The following image shows the different configurations for the ACAR conductors.
Different configuration for ACAR conductors
Features of ACAR conductors
ACAR conductors offer many different features that allow them to be used in a variety of different applications. The features of ACAR conductors includes;
- Better mechanical properties
- Superior resistance to corrosion
- Can deliver high current-carrying strength and capacity
- Have a significantly lower conductor weight
- ACAR conductors have convenient installations
- ACAR conductors are cost-effective and have very low maintenance
- Enhanced strength to weight ratio
- Improved electrical characteristics
Conducting properties of ACAR conductors
Under three-phase electrical power distribution, the electric conductors are designed to have as low electrical impedance as possible. The low impedance in the conductor ensures that there is a minimal loss to the power during distribution. The resistance of the ACAR cables differs from one section to another due to the hysteresis loss, skin effect, and proximity effect. Depending on the size of the wire, type of operation, and life of the cable, these factors directly affect the ACAR conductor resistance.
The skin effect of the ACAR cables decreases the cross-sectional area in which the current travels via the conductor with the increase in the AC frequency. For the AC current, around 60% of the electric current flows between the skin depth and the surface. These factors are directly dependent on the electrical conductivity, the frequency of the current, and the magnetic properties of the alloy conductor in the ACAR conductor. This reduced area results in an increase of resistance due to the inverse relationship between the cross-sectional area of the conductor and the resistance of the conductor. The skin effect in the ACAR conductors benefits the designs, as it results in the current to be concentrated towards the low-resistivity aluminum on the outside of its alloy.
In a conductor (ACAR or other types) currying AC current, if the current flows through one or more nearby conductors, then the distribution of the current will be automatically concentrated to smaller regions. This resulting current in the ACAR conductors is termed as the proximity effect current. The crowding of the current gives an increase in the effective AC resistance of the current. The proximity effect of the ACAR conductors also results in the changing magnetic field, which directly influences the distribution of the current within the conductor due to the electromagnetic induction. Thus, the proximity effect in the ACAR conductors results in the current to be concentrated in the areas of the conductors that are furthest away from the nearby conductors carrying the conductors in the same direction.
Properties for ACAR conductors
The properties of ACAR conductors made them the conductor of choice for several different reasons. The key properties of ACAR conductors are as follows;
The ACAR conductors have high resistance to corrosion due to the absence of any galvanic action between dissimilar metals. In ACAR cables, both the conductor and the reinforcement is of Aluminum and its alloys. In all the other types of similar conductors, a coating of Zinc was supposed to be done in order to avoid corrosion. Zinc was both expensive and heavy and thus resulted in poor overall performance. Being highly resistant to corrosion, the ACAR conductors can be also be used in damp conditions.
ACAR conductor coating
When the ACAR conductor is new, the aluminum has a shiny surface. The shiny surface has low emissivity for heat radiation combined with low absorption of sunlight. As the conductor and the reinforcement ages, the color of the wire become dull gray due to the oxidation reaction of the aluminum strands. When the ACAR conductors are used in high pollution regions, it is common for them to turn black after several years due to their exposure to the pollutants and other elements. For foraged conductors, it is important that to have an external heat reflective coating as if left as it is, the aged ACAR conductor might develop high heat radiation and sunlight absorption.
Specification data for ACAR conductors
There exist many different combinations of ACAR conductors, and each cable has its own set of specifications. The common specifications for ACAR conductors include;
- ASTM B-230 – it is an aluminum wire having a configuration of 1350-H19.
- ASTM B-398 – Aluminum-Alloy wire having a configuration of 6201-T81. This wire is used for general electrical purposes
- ASTM B-524 – Concentric-lay-stranded aluminum conductor with an aluminum alloy reinforced ACAR 1350/6201
Selecting the right ACAR conductor for your project
The best way to select the right ACAR conductor for your project is to select your conductor based on its ampacity ratings. The ampacity ratings are based directly on the guidelines related to voltage, ambient temperature testing, voltage, and how sensitive they are to the sun. Along with this, they will also measure the maximum conductor temperature, which is called the emissivity. All these factors directly affect the factors that lead to the ampacity ratings of the ACAR conductors. Thus, by selecting the right ampacity for your wire, you select the right ACAR wire for your purpose. The prices of the wire are dependent on their diameter and length.
Demand drivers for ACAR conductors
It is important for the ACAR conductors’ manufacturers and buyers to understand better what drives the demands of the conductors in the market. The following are the demand drivers that are common all over the world;
Demand by the user
The demand for electricity to different parts of the country, combined with the grid interconnection, the demand for the ACAR conductors has been rising steadily in the previous years.
The customer segment comprises of different EPC contractors and electric utility companies. Whenever a new tender for an overhead cable is floated in the market; the EPC contractor is likely to approach the overhead conductor manufacture. The ACAR conductors being the popular choice of conductors in the market tends to be sold as soon as the customer segment initiates the demand in the market.
In the market of ACAR and other similar conductors, the influencers in the market play a vital role in the sales of their conductors. The key influencers, in this case, are the engineering consultants. This consultant helps in deciding which ACAR conductor is best for your needs and other specifications.
Economics of ACAR conductors
It is important to know that apart from the technical advantages that the ACAR conductors have over other cables, these conductors are also far better than other cables in terms of its economics. The ACAR conductors and its installation requires several costs which are as follows;
Cost of production
The newer types of ACAR conductors can have a higher cost than the older ACAR conductors. Reports show that newer cables can cost as much as 20% higher as compared to the older models. The reason for this added cost is due to the added cost of alloying combined with the slower speed wire drawing and the artificial aging of the conductors to maximize the life span and have optimum properties.
The higher cost of the ACAR conductors can be compensated with the many advantages of the ACAR conductors over other types of conductors. The ACAR conductors are lighter, have better corrosion and electrical properties along with lower freight and handling costs as well as easy installation. Therefore, the initial higher costs of the ACAR conductors can be recovered, eventually owing to its superior performance and characteristics.
Cost of transmission towers, fittings, accessories
For any conductor, the cost of transmission towers, accessories, and fittings roughly amount to 40% of the capital cost. Since the ACAR cables have better strength to weight ratio, it is possible for the engineers to increase the length of the cable while maintaining sufficient ground clearance. With longer cables and less sag, the number of towers can decrease by 10%, which further reduces the cost of extra fittings and accessories.
It is important to ensure that the fitting and the hardware that is suitable for the ACAR conductors installed are of the correct rating and are installed correctly. There are many different dead-end accessories for installation and overhead conductor splice that are available in the market. Therefore, it is necessary that proper consultation is being taken when purchasing the fittings and accessories for your cable. At SSGcable, we employ proactive employees and consultants who are ever ready to assist you and guide you to the best fittings and accessories for your product.
Cost of installation and transportations
The lower handing and freight costs combined with the easier installation of lighter ACAR conductors are of significant advantage for many. Many operators prefer these conductors because of the long-term benefits that these conductors have. Due to such properties, these conductors the preferred choice for distant and hilly areas.
The power losses in the ACAR conductors are far lesser as compared to most of the conductors. The economic advantage in favor of the ACAR conductors as great as the ratio of AC/DC resistance is the same throughout the conductor practically at all load currents. In cases of other similar conductors such as ACSR conductors, this ratio may become high as the load current increases. The voltage drops using the ACAR conductors are also quite low.
Other economic consideration of ACAR conductors
While considering the overall economics of ACAR conductors, the salvage value of the aluminum cannot be overlooked. The aluminum once scrapped can be used for various other purposes and also offers good salvage value to its users.
Different types of reinforced conductors commonly used today
Sagging in ACAR conductors
ACAR conductors do not sag over short lengths and can be easily extended to longer spans without the need for additional support towers. However, there is still a line of tension or sag that occurs in these conductors over long distances. The sag or the line tension in the ACAR conductors can be set using;
- Transit method
- Dynamometer which directly measures the tension of the conductor
- Using the “Stop-Watch” method. This method is usually used to measure the tension in the conductor at multiple locations. The formulation for determining the sag or the line tension is as follows;
T = time for Nth return wave (s)
N = number of return waves
Adjusting the sag
When carrying out the sagging of the ACAR conductors, it is important that the tension adjustment is carried out within one hour. When sagging the ACAR conductors, it is advised to check the sag at more than one location to make sure that the procedure was done right. Once the sagging tension has been set, it is advised not to adjust the conductors again. Adjusting the sagging tension after it has been set may result in permanent damage to the conductor along with the operator.
Ideally, the conductors should be clipped within 24 hours after the ACAR conductor sags. The line tension must never be adjusted again after the initial adjustment has been made as by this point, the creep has already started to take place. Changing the line tension at this point may cause permanent damage to the conductor. IEEE standard 524 states that for any type of conductor that is sitting on shelves, the time from initial installation to clipping should never be more than 72 hours. Exceeding this time frame is highly likely to cause damage to the conductor.
Ice and Wind loads on ACAR conductors
When the overhead ACAR conductors are covered with ice or are exposed to strong winds, the effective weight per unit length of the conductor increases. With an increase in load, the tension in the cables tends to increase significantly. Under such instances, both the conductor, as well as its supports, can abruptly fail unless these cases of extreme tension are considered in the conductor line design.
Different countries have different regulations on how much tension must be present in the cables when they are installed. In the United States, for example, the country is divided into three main categories, which signifies how much extra tension allowance must be kept into the conductor while installing the overhead cables. Places with high wind and ice are required to have high extra tension whereas, places with low ice and wind are required to have low extra tension in the cable.
ACAR conductor sidewall bearing pressure
Another factor that should be considered when installing ACAR overhead conductors is the pressure between the stringing block lining material and the conductor itself. Extreme pressure over the conductor can greatly damage the conductor by either loosening the aluminum strands or by deforming the conductor. Excessive pressure on the conductor can also greatly degrade the stringing sheave-groove lining material faster. This excessive force exerted on the cable is termed as the ACAR conductor bearing pressure or sidewall bearing pressure. The sidewall pressure in any type of conductor can be calculated by;
|P = Sidewall bearing pressure [MPa]
|DS = diameter of sheave to bottom of groove [mm]
|DC =diameter of conductor [mm]
|T = tension of the conductor [N]
Due to their design and superior strength, the ACAR conductors are suited for many different industrial applications. Common applications include;
- ACAR conductors are a preferred choice of conductors for power distribution and transmission projects
- Overhead power distributions that require aluminum conductors along with high strength and longer life spans
- Bus bars in high voltage substations
One of the major uses of ACAR conductors is the overhead power transmission
From a discussion of different economic and technical factors, the ACAR conductors offer a remarkable range of flexibility to meet the different design requirements. We at SSGcables are manufacturers and suppliers of high-quality ACAR conductors. We have decades of experience in ACAR conductor research, development, and manufacturing. Therefore, from conductor selection to sheathing to complete cabling, we execute a full set of strict control over the quality of our components at each stage of manufacturing. At SSGcables, we have excellent sourcing and supply chain at each production stage, which ensures cost-savings, excellence, and value-adding solution so that we can deliver what we promise to our customers.
We would love to work closely with you to offer the best ACAR conductor or any other conductor to fit your requirements and deliver you the best in class product.