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The capacitance of a cable depends upon
The length of the cable
Relative permittivity of dielectric used in cable
Ratio of sheath diameter and core diameter
All of above
All of above
The capacitance of an underground cable is defined by its physical geometry and the properties of the insulating material. Since it follows the principle of a cylindrical capacitor, it is directly proportional to the length and relative permittivity, and inversely proportional to the logarithmic ratio of the sheath-to-core radii.
The capacitance of an underground cable is defined by its physical geometry and the properties of the insulating material. Since it follows the principle of a cylindrical capacitor, it is directly proportional to the length and relative permittivity, and inversely proportional to the logarithmic ratio of the sheath-to-core radii.
C=ln(dDтАЛ)2╧А╧╡0тАЛ╧╡rтАЛlтАЛ тАФ Capacitance of a single-core cable
╧╡=╧╡0тАЛ╧╡rтАЛ тАФ Permittivity of the dielectric medium
A cable acts as a cylindrical capacitor where the core is the inner electrode and the metallic sheath is the outer electrode. The capacitance C is determined by the formula C=ln(D/d)2╧А╧╡0тАЛ╧╡rтАЛlтАЛ, where ╧╡rтАЛ is the relative permittivity, l is the length, D is the sheath diameter, and d is the core diameter.
Capacitance increases linearly with the length (l) of the cable.
Higher relative permittivity (╧╡rтАЛ) of the insulation leads to higher charging currents.
The ratio of diameters (D/d) dictates the geometric factor of the capacitor.
Underground cables have much higher capacitance than overhead lines due to the proximity of the sheath and the dielectric medium.
Used for transmitting power in congested urban areas.
Provides reliable operation without environmental interference.
High charging current due to significant capacitance.
Complex thermal management required compared to overhead lines.
Underground power distribution
Submarine power cables
The charging current IcтАЛ=j╧ЙCV becomes significant in long HV cables, requiring shunt reactor compensation.
Option A, B, and C are all individual variables in the capacitance equation, thus D is the only complete answer.
D is correct тАФ The capacitance of a cable depends on its length, the dielectric material used, and the geometric configuration of the core and sheath.
Always remember that in power systems, cable charging current is a major factor in determining the maximum transmission distance for underground AC cables.