POWER CONDUCTORS: 101 COMPREHENSIVE GUIDE

POWER CONDUCTORS

Power Conductors are the most essential part of the transmission and distribution of electricity. It is the medium via which the current flows. Normally it is made of copper or aluminium alloy as these metals have proven good service and have less resistivity and cost.

TYPES OF CONDUCTORS

SOLID POWER CONDUCTORS

The solid conductors used in the industry are basically for all DC supply purposes. These are simple and single-piece wires which can conduct electricity. However, in high-voltage AC applications, these conductors are prone to skin effects and proximity effects. Because of the skin effect the solid conductor becomes prone to localised induction heating and therefore the ampacity of these reduces. Also, these conductors are less flexible, though they are highly non-corrosive, and still these breaks often because of less tensile strength.

HOLLOW POWER CONDUCTORS

The skin effect of the solid power conducts is nullified by the use of a hollow cross-section tubular type power conductor. They are made of copper and aluminium alloy and are often utilized in bus bar sections of high-voltage substations. As the surface area per unit volume of this conductor is less therefore the electric field surrounding the power conductor is also less. It, therefore, decreases the corona effect to a larger extent.

STRANDED POWER CONDUCTORS

These types of power conductor are widely used in the industry because of their greater flexibility, mechanical stability, and thermal superiority. These types of power conductors have multiple strands of smaller diameter which are laid in layers one over the other in a twisted manner. This laying of the strands is known as stranding. Stranding can be of many types such as concentric, unidirectional concentric, equi-lay concentric, bunched stranding, and rope stranding.

Mostly the stranding follows the geometric numbers in laying are 1-6-12-18-…

That means 1 strand centrally placed, in the 2^nd layer 6 nos of strands, 12 in the third and …

The types of stranded power conductors, mostly used in the transmission sector are:

AAAC

AAAC conductors are all aluminium alloy conductors and are extensively used in high-voltage transmission lines. They are made of aluminium silicon and magnesium alloy. These conductors are lighter in weight and are superior in corrosion resistance. These conductors have a minimum resistance of 52.5% of IACS. The maximum continuous operating temperature is around 90 degrees Celsius. Its current carrying capacity is 15-20% higher than conventional ACSR conductors. Its weight per km is also less and therefore it helps reduce the vertical loading in transmission towers.

The vertical sag of this conductor is more compared to ACSR at maximum continuous operating temperature. Therefore, the ruling span of the transmission line has to be reduced or tower extension has to be used.

ACSR

These conductors are conventional types and have been in use in the industry for quite a long now. They are made of a stranded core of galvanised steel, helically surrounded by one or more layers of aluminium strands. These conductors have low sag in the operating temperature range. The steel core provides the conductor with mechanical strength. However, the operating temperature range of these conductors is limited to 75 degrees Celsius. These conductors are prone to corrosion and are not advised to be used in coastal areas. Since the conductor is a bimetallic one and hence there are chances of galvanic reaction between the steel and EC-graded aluminium.

TYPICAL DATASHEET OF ACSR CONDUCTOR

AAC

All Aluminium conductors are the ones where all strands of these conductors are of Aluminium. As such these conductors have very good conductivity and are very light but have very little tensile strength. Thus, these conductors are mainly used for jumper drops in substations for connectivity with equipment.

AACSR

Aluminium Alloy conductor steel reinforced are used for high-strength applications such as river crossings or large valley crossings. These consist of a stranded steel core surrounded by one or more layers of Aluminium alloy. The higher tensile strength of these conductors enables them to be strung at higher tensions, thereby reducing sag & thus reducing the height of towers.