Types of Overhead Conductors

OVERHEAD CONDUCTORS

TYPES OF OVERHEAD CONDUCTORS

PROPERTIES OF OVERHEAD BARE CONDUCTORS:

Current Carrying Capacity

Strength * Weight * Diameter * Corrosion Resistance * Creep Rate * Thermal Coefficient of Expansion * Fatigue Strength * Operating Temperature * Short Circuit Current/Temperature * Thermal Stability * Cost

CATEGORIES OF OVERHEAD CONDUCTORS:

Homogeneous Conductors:

Copper * AAC( All Aluminum Conductor) * AAAC (All Aluminum Alloy Conductor) * The core consists of a single strand identical to the outer strands. Since all the strands are the same diameter, one can show that the innermost layer always consists of 6 strands, the second layer of 12 strands, etc., making conductors having 1, 7, 19, 37, 61, 91, or 128 strands.

Non Homogeneous Conductors:

ACAR (Aluminum Conductor Alloy Reinforced) * ACSR (Aluminum Conductor Steel Reinforced) * ACSS (Aluminum Conductor Steel Supported) * AACSR (Aluminum Alloy Conductor Steel Reinforced. * the strands in the core may or may not be of the same diameter. In a 30/7 * ACSR conductor the aluminum and steel strands are of the same diameter. In a 30/19 * ACSR they are not. Within the core or within the outer layers, however, the number of strands always increases by 6 in each succeeding layer. Thus, in 26/7 ACSR, the number of layers in the inner layer of aluminum is 10 and in the outer layer 16

CATEGORIES OF OVERHEAD CONDUCTORS

CHOICES OF OVERHEAD DEPEND UPON:

Power Delivery Requirements

Line Design Requirements

Environmental Considerations

(1) AAC (ALL ALUMINUM CONDUCTORS)

AAC is made up of one or more strands of hard drawn 1350 Aluminum Alloy. * AAC has had limited use in transmission lines and rural distribution because of the long spans utilized. * Good Conductivity -61.2% IACS * Good Corrosion Resistance * High Conductivity to Weight Ratio. * Moderate Strength

Typical Application

Short spans where maximum current transfer is required. * The excellent corrosion resistance of aluminum has made AAC a conductor of choice in coastal areas. * Because of its relatively poor strength-to-weight ratio, AAC has seen extensive use in urban areas where spans are usually short but high conductivity is required. * These conductors are used in low, medium and high voltage overhead lines.

(2) AAAC (ALL ALUMINUM ALLOY CONDUCTORS)

AAAC are made out of high strength Aluminum-Magnesium-Silicon alloy. * AAAC with different variants of electrical grade Alloys type 6101 and 6201. * These conductors are designed to get better strength to weight ratio and offers improved electrical characteristics, excellent sag-tension characteristics and superior corrosion resistance when compared with ACSR. * Equivalent aluminum alloy conductors have approximately the same ampacity and strength as their ACSR counterparts with a much improved strength-to-weight ratio, and also exhibit substantially better electrical loss characteristics than their equivalent single layer ACSR constructions. The thermal coefficient of expansion is greater than that of ACSR. * As compared to conventional ACSR, lighter weight, comparable strength & current carrying capacity, lower electrical losses and superior corrosion resistance have given AAAC a wide acceptance in the distribution and transmission lines.

Features

High strength to weight ratio * Better sag characteristics * Improved electrical properties * Excellent resistance to corrosion * Specifications * Higher Tensile Strength * Excellent Corrosion Resistance * Good Strength to Weight Ratio * Lower Electrical Losses * Moderate Conductivity –52.5% IACS

Typical Application

Transmission and Distribution applications in corrosive environments, ACSR replacement.

(3) ACAR (ALUMINUM CONDUCTOR AL. ALLOY REINFORCED)

Aluminum Conductor Alloy Reinforced (ACAR) is formed by concentrically stranded Wires of Aluminum 1350 on high strength Aluminum-Magnesium-Silicon (AlMgSi) Alloy core. * The number of wires of Aluminum 1350 & AlMgSi alloy depends on the cable design. * Even though the general design comprises a stranded core of AlMgSi alloy strands, in certain cable constructions the wires of AlMgSi Alloy strands can be distributed in layers throughout the Aluminum 1350 strands. * ACAR has got a better mechanical and electrical properties as compared to an equivalent conductors of ACSR,AAC or AAAC. * A very good balance between the mechanical and electrical properties therefore makes ACAR the best choice where the ampacity , strength , and light weig…