- Bundled Conductor Definition: A bundled conductor is defined as a conductor formed by grouping two or more stranded conductors to increase current carrying capacity.
- Use in High Voltage Systems: Bundled conductors are used in transmission lines above 220 KV to optimize current flow and are more economical than hollow conductors.
- Reduced Reactance and Voltage Gradient: Bundled conductors reduce the reactance and voltage gradient, which helps in lowering corona loss and radio interference.
- Geometric Mean Radius (GMR): Increasing the GMR decreases inductance, improving the efficiency of the transmission line.
- Surge Impedance Impact: Bundled conductors reduce surge impedance, thus increasing the surge impedance loading and the overall transmission capacity of the system.
A single stranded conductor is common on lines up to about 220 kV. Above that voltage a single solid or stranded wire has a high surface gradient. A hollow tube can carry the current with a larger radius, but it is awkward to string and maintain. Extra-high-voltage lines therefore use bundled conductors: two or more sub-conductors per phase, typically above about 220 kV.
What is Bundled Conductor?
A bundled conductor is two or more stranded conductors of one phase, held apart by spacers, sharing the phase current.
In a bundled conductor, two or more stranded conductors are used per phase. Besides increasing the current carrying capacity, bundled conductors reduce the reactance, voltage gradient, corona loss, radio interference, and surge impedance of the transmission line.
By making bundle conductor, the geometric mean radius (GMR) of the conductor increased. As the self GMR of the conductor increases, the inductance of the conductor decreases. Theoretically, there is an optimum sub-conductor spacing in bundle conductor that will give minimum voltage gradient on the surface of bundle conductor. The optimum spacing between sub-conductors for reducing voltage gradient is eight to ten times of the diameter of the conductor.
Since the voltage gradient gets reduced, the radio interference also gets reduced.
As the inductance of the bundled conductor is reduced, the surge impedance of the line is reduced became the formula of surge impedance is
Where L is the inductance per phase per unit length, and C is the capacitance per phase per unit length of the transmission line. As the surge impedance gets reduced due to bundling the conductor, the surge impedance loading, of the conductor gets increased. Increased surge impedance loading makes the transmission capacity of the system more.
