Aerial bundled cable
Encyclopedia
Aerial bundled cables are overhead power line
s 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 voltage
s (1000 V or less), in the distribution
portion of the electrical grid, as the required insulation thickness would be impractical at higher voltages.
Overhead power line
An overhead power line is an electric power transmission line suspended by towers or utility poles. Since most of the insulation is provided by air, overhead power lines are generally the lowest-cost method of transmission for large quantities of electric energy...
s using several insulated phase conductors
Polyphase system
A polyphase system is a means of distributing alternating current electrical power. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a definite time offset between the voltage waves in each conductor. Polyphase systems are particularly useful...
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
Short circuit
A short circuit in an electrical circuit that allows a current to travel along an unintended path, often where essentially no electrical impedance is encountered....
. 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 voltage
Low voltage
Low voltage when used as an electrical engineering term concerning an electricity supply grid or industrial use, broadly identifies safety considerations of the system based on the voltage used. The meaning of the term "low voltage" is somewhat different when used with regard to a more typical end...
s (1000 V or less), in the distribution
Electricity distribution
File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...
portion of the electrical grid, as the required insulation thickness would be impractical at higher voltages.
Advantages
- Relative immunity to short circuits caused by external forces (wind, fallen branches), unless they abrade the insulation.
- Can stand in close proximity to trees and will not generate sparks if touched.
- Simpler installation, as crossbars and insulators are not required.
- Less cluttered appearance.
- Can be installed in a narrower right-of-way.
- At junction poles, insulating bridging wires are needed to connect non-insulated wires at either side. ABC can dispense with one of these splices.
Disadvantages
- Additional cost for the cable itself.
- Insulation degrades due to sun exposure, though the critical insulation between the wires is somewhat shielded from the sun.
- Insulation thickness makes this economical only for low voltage power lines.