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Earth wires are made of
Copper
Aluminum
Iron
Galvanized stranded steel
Galvanized stranded steel
Earth wires, particularly in overhead transmission lines, are primarily made of galvanized stranded steel because of the requirement for high mechanical strength and corrosion resistance. They are designed to provide a low-impedance path to ground for lightning surges and fault currents, rather than to carry high-current loads continuously.
Earth wires, particularly in overhead transmission lines, are primarily made of galvanized stranded steel because of the requirement for high mechanical strength and corrosion resistance. They are designed to provide a low-impedance path to ground for lightning surges and fault currents, rather than to carry high-current loads continuously.
ZgтАЛ=RgтАЛ+j╧ЙLgтАЛ тАФ representing the ground impedance path provided by the earth wire system
T=╧Г├ЧA тАФ where T is the required tensile strength for mechanical stability
The earth wire acts as a shield above the phase conductors. When a lightning stroke occurs near the line, the earth wire intercepts the strike, providing a path to the tower and grounding system. Its stranded steel construction ensures it can withstand high tensile stress during environmental factors like wind loading and ice accumulation.
Galvanizing provides a zinc coating that prevents the steel from rusting.
Stranded construction offers better mechanical flexibility compared to solid steel conductors.
Earth wires are usually placed at the top of transmission towers to provide the best shielding angle.
Steel provides the necessary mechanical strength while the galvanization ensures longevity.
High mechanical strength to withstand extreme weather
Excellent resistance to corrosion due to zinc coating
Cost-effective material for long transmission spans
Lower electrical conductivity compared to copper or aluminum
Heavy weight compared to aluminum alloys
Overhead transmission line shielding against lightning
Grounding overhead line support structures
Used as static wires in HVDC and HVAC systems
The resistivity of steel is much higher than that of copper; however, the primary purpose of an earth wire is surge protection, not steady-state current conduction.
Copper is not used for overhead earth wires because it is expensive, heavy, and has lower tensile strength than steel, making it prone to sagging.
D is correct тАФ Galvanized stranded steel is used due to its superior mechanical strength and corrosion resistance necessary for overhead line shielding.
Always remember that the selection of earth wire material is dictated by mechanical endurance requirements (tensile strength) rather than electrical conductivity, which is the primary criterion for phase conductors.