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Considering the following statement about ground wires
Ground wire helps to increase the effective capacitance between the line conductor and ground
It shields the main conductor against direct stroke
It is placed higher than the main conductors and supported on the same tower
It helps to reduce the risk of back flash over in case of direct strokes
1 and 2 are correct
2 and 3 are correct
1, 2 and 4 are correct
1, 2, 3 and 4 are correct
1, 2, 3 and 4 are correct
A ground wire (or shield wire) is a non-current carrying conductor installed at the highest point of a transmission line tower to protect the power system from direct lightning strokes. By providing a low-impedance path to the ground, it intercepts lightning strikes before they can hit the phase conductors.
A ground wire (or shield wire) is a non-current carrying conductor installed at the highest point of a transmission line tower to protect the power system from direct lightning strokes. By providing a low-impedance path to the ground, it intercepts lightning strikes before they can hit the phase conductors.
VbackтАЛ=IsтАЛ├ЧRtтАЛ+LdtdiтАЛ тАФ voltage developed across tower causing back flashover
CeffтАЛ=CgтАЛ+CmтАЛ тАФ effective capacitance increase due to shield wire
The ground wire works through two primary mechanisms: shielding and capacitance modification. By being placed above phase conductors, it creates a 'shielding angle' that directs lightning to the tower structure. It also increases the system's effective capacitance to ground, which helps in reducing the surge impedance and controlling the transient recovery voltage distribution across the insulators, thereby minimizing the probability of back flashovers.
Ground wire is always connected to the tower body to ensure a path to earth.
It acts as a surge diverter by intercepting the lightning stroke.
The shielding angle is critical; smaller angles offer better protection.
It helps in reducing the steepness of the traveling wave reaching the station equipment.
Prevents direct lightning strikes on phase conductors
Reduces the magnitude of overvoltage surges
Improves reliability in high lightning-prone areas
Adds weight to the transmission towers
Increases initial capital cost of the line installation
High voltage transmission lines (above 66kV)
Substation lightning protection
Tower shielding in rugged terrain
Back flashover occurs when the voltage across the insulator exceeds its impulse flashover strength due to high tower footing resistance.
Ground wire material is typically high-strength galvanized steel or ACSR (Aluminum Conductor Steel Reinforced).
D is correct тАФ All listed points correctly describe the functions and physical arrangement of ground wires in power system protection.
Always remember that the ground wire protects against direct strikes, while surge arresters protect against surges entering from the lines.