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The best material to avoid radio interference is
Aluminum
Galvanized steel
Bundled Conductors
Aluminum & bundled conductors
Aluminum
Aluminum is the preferred material for high-voltage transmission conductors primarily due to its high surface-to-weight ratio and ability to reduce the electric field gradient. By maintaining a large conductor surface area, aluminum minimizes the corona discharge effect, which is the primary source of radio interference in EHV transmission lines.
Aluminum is the preferred material for high-voltage transmission conductors primarily due to its high surface-to-weight ratio and ability to reduce the electric field gradient. By maintaining a large conductor surface area, aluminum minimizes the corona discharge effect, which is the primary source of radio interference in EHV transmission lines.
E=rln(d/r)VтАЛ тАФ Electric field intensity at the surface of a cylindrical conductor.
VcтАЛ=g0тАЛтЛЕmтЛЕrln(rdтАЛ) тАФ Critical disruptive voltage for corona inception.
Radio interference (RI) is primarily caused by corona discharge on the surface of conductors when the surface voltage gradient exceeds the disruptive critical voltage of air. Aluminum allows for the design of conductors with larger effective diameters, which decreases the electric field intensity E at the conductor surface, thereby suppressing corona discharge and subsequent electromagnetic noise.
Corona is the ionization of air around a conductor caused by high potential gradients.
Aluminum is light and cost-effective, allowing for larger cross-sections which lower the surface gradient.
Radio Interference (RI) is a direct manifestation of corona discharge high-frequency pulses.
Bundled conductors further reduce RI by increasing the effective radius of the phase.
High conductivity-to-weight ratio
Lower cost compared to copper
Effective in reducing corona-related losses
Higher thermal expansion coefficient than steel
Lower tensile strength requiring steel reinforcement (ACSR)
Extra High Voltage (EHV) transmission lines
High Voltage Direct Current (HVDC) transmission
Overhead distribution lines
In EHV lines, the bundle configuration is actually more effective than a single aluminum conductor, but aluminum is the base material used for these conductors.
Galvanized steel is used primarily for shielding (ground wires) rather than phase conductors because of its high resistance.
A is correct тАФ Aluminum's properties allow for larger effective conductor radii, which significantly reduce the surface electric field gradient and minimize corona-induced radio interference.
Always remember that corona loss is directly proportional to (f+25)/╬┤ and (VтИТVcтАЛ)2. Reducing the surface gradient through geometry or material choice is the standard engineering solution.