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If the effect of earth is taken into account, then the capacitance of line to ground
Decreases
Increases
Remains unaltered
Becomes infinite
Increases
When the earth is taken into account for a transmission line, the capacitance to ground increases because the earth acts as an equipotential surface, providing an additional path for flux lines ┬╖ According to the method of images, a virtual conductor (image conductor) is assumed below the earth's surface, which effectively reduces the potential difference for the same amount of charge.
When the earth is taken into account for a transmission line, the capacitance to ground increases because the earth acts as an equipotential surface, providing an additional path for flux lines ┬╖ According to the method of images, a virtual conductor (image conductor) is assumed below the earth's surface, which effectively reduces the potential difference for the same amount of charge.
C=ln(r2hтАЛ)2╧А╧╡тАЛ тАФ Capacitance without earth effect
CeffтАЛ=ln(r2hтАЛ)тИТln(1+(D2hтАЛ)2тАЛ)2╧А╧╡тАЛ тАФ Capacitance considering earth effect
The earth is considered a perfectly conducting plane ┬╖ By the method of images, a charge on the conductor induces an opposite charge on the earth ┬╖ This is modeled by placing an 'image' conductor at an equal distance below the ground surface ┬╖ The presence of this image increases the flux linkages between the line and the ground, thereby increasing the effective capacitance CgтАЛ.
The earth is treated as an infinite conducting sheet at zero potential.
The proximity of the ground effectively reduces the distance between the conductor and the return path, thus increasing capacitance.
The increase in capacitance is usually small (around 1-5%) for overhead lines but becomes significant for cables or very low-height lines.
Higher capacitance results in increased charging current, which influences the power factor and voltage regulation of the line.
More accurate modeling of power system transients.
Better estimation of shunt charging currents in long transmission lines.
Complexity in mathematical calculations involving image charges.
Requires knowledge of ground resistivity for precise modeling.
Design of high-voltage transmission lines.
Analysis of ground fault currents.
Calculation of line parameters for power system stability studies.
The effect of earth is represented by an image conductor located at a distance 'h' below the surface.
Option B is correct because the proximity of the grounded surface enhances the electrical storage capacity (capacitance) between the conductor and earth.
B is correct тАФ Taking the earth into account increases the capacitance of a line to ground due to the electrostatic influence of the earth behaving as an equipotential plane.
Always remember that capacitance is inversely proportional to the log of the distance; the 'image' method effectively shortens the path, thereby increasing capacitance.