- 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.
Single stranded conductors are used in transmission system usually up to 220 KV. But it is not possible to use single-stranded conductor for the voltage above 220 KV systems. For very high voltage system, hollow conductor can be used to optimize the flow of current through it. But erection and maintenance of hollow conductors in the ∑HV system are not economical. The problem can be solved by using bundled conductors instead of hollow conductor in the electrical transmission system above 220 KV voltage level.
What is Bundled Conductor?
A bundled conductor is formed by grouping two or more stranded conductors together to increase current carrying capacity.
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.
