BUNDLED CONDUCTORS

Bundled Conductors inTheory 

Extra high voltage lines corona causes a large problem if the conductor has only one conductor per phase. Corona occurs when the surface potential gradient of a conductor exceeds the dielectric strength of the surrounding air. This causes ionization of the area near the conductor. Corona produces power loss. It also causes interference with communication channels. Corona manifests itself with a hissing sound and ozone discharge. Since most long distance power lines in India are either 220 kV or 400 kV, avoidance of the occurrence of corona is desirable..continue..

Aerial Bundled Conductors 

Aerial bundled cables (also aerial bundled conductors) are overhead power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor. This contrasts with the traditional practice of using uninsulated conductors separated by air gaps. The main objections to the traditional design are that the multiple conductors are considered ugly, and external forces (such as high winds) can cause them to touch and short circuit. The resultant sparks were a cause of bushfires in drier climates. In moister climates, tree growth is a significant problem for overhead power lines. Aerial bundled cables will not arc over if touched by tree branches. Although persistent rubbing is still a problem, tree-trimming costs can be reduced.
Note that bundled cables are used only for low voltages (1000 V or less), in the distribution portion of the electrical grid, as the required insulation thickness would be impractical at higher voltages..continue..


Bundled Conductors in Transmission line 

A “bundle conductor” is a conductor made up of two or more ‘(sub-conductors”, and is used as one phase conductor. Bundle conductors are also called duplex, triplex, etc., conductors, referring to the number of sub-conductors and are sometimes referred to as grouped or multiple conductors. Considerable work on bundle conductors has been done by the engineers of Siemens Schuckertwerkez who concluded that bundle conductors were not economical at 220 kv, but for rated voltages of 400 kv or more, are the best solution for overhead transmission. Rusck and Rathsman state that the increase in transmitting capacity justifies economically the use of two conductor bundles on 220-kv lines..continue..


Bundled Conductors on Line Loss 

In support to this post regarding bundled conductors, we will discuss here how bundling of conductors can affect the losses in the transmission lines. Bundling of conductors in the transmission lines helps lessen the effect of the two major phenomena the exist especially in voltage levels of 220kV and up namely; the CORONA effect and the SKIN effect. Corona, also known as partial discharge, is a type of localized emission resulting from transient gaseous ionization in an insulation system when the voltage stress, i.e., voltage gradient, exceeds a critical value. .continue..


De-Rating Bundled Conductors 

De-rating Bundled Conductors (to account for inhibited heat dissipation): when multiple insulated conductors are bundled together, multiply the ampacity by 0.8 for 2-5 conductors; 0.7 for 6-15 conductors; or 0.5 for 16-30 conductors. .continue..


Spacer for Bundled Conductors 

Spacer dampers consist of clamps, a connecting frame and the damping elements. The damping elements, which are made of highly flexible macromolecular elastomere, guarantee a certain mobility of the damper clamp. Additionally the damping elements are designed in respect of temperature resistance, environmental conditions and to be free of corona. All types of spacers have passed strict type tests in order to guarantee suitability. .continue..