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The presence of earth in case of overhead lines
Increases the capacitance
Increases the inductance
Decreases the capacitance
Decreases the inductance
Increases the capacitance
The presence of earth provides a return path for electric flux lines, which acts as an additional equipotential surface below the conductor ┬╖ This configuration behaves like an image charge method, effectively increasing the system capacitance compared to an isolated conductor in free space.
The presence of earth provides a return path for electric flux lines, which acts as an additional equipotential surface below the conductor ┬╖ This configuration behaves like an image charge method, effectively increasing the system capacitance compared to an isolated conductor in free space.
C=ln(r2hтАЛ)2╧А╧╡0тАЛтАЛ тАФ Capacitance of a single conductor above earth
Q=CV тАФ Relationship between charge, capacitance, and potential
According to the principle of images, a conductor at height h above a conducting ground plane acts as if there were an equal and opposite 'image' conductor at depth h below the ground ┬╖ This creates a potential difference that accommodates more charge for the same voltage, thereby increasing the shunt capacitance (C=VQтАЛ).
The ground acts as an equipotential plane (V=0).
Increasing capacitance leads to an increase in charging current.
The closer the conductor is to the ground (smaller h), the higher the capacitance.
Inductance is primarily determined by flux linkages within and around the conductor, which is less affected by the earth plane compared to capacitance.
Provides a reference point for potential.
Allows for single-wire earth return (SWER) distribution systems.
Higher capacitance increases charging current, which can affect voltage regulation in long lines.
Increases capacitive losses in high-voltage transmission lines.
Design of overhead transmission line insulation.
Calculation of corona inception voltage.
Protection coordination and fault analysis.
The capacitance increases because the ground acts as an image charge, reducing the potential of the conductor for a given charge.
Option B and D are incorrect because earth presence has a negligible effect on the magnetic field distribution (inductance) unless the ground resistivity is extremely low and frequency is very high, but generally, it is considered an electrostatic effect.
A is correct тАФ The presence of the earth acts as an image plane, effectively increasing the capacitance of an overhead transmission line.
Always remember that capacitance is sensitive to the surrounding environment (earth/objects), whereas inductance is primarily determined by the internal and external magnetic flux geometry of the conductor itself.