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Bundled conductors in EHV transmission system provide
Reduced capacitance
Increased capacitance
Increased inductance
Increased voltage gradient
Increased capacitance
Bundled conductors are used in Extra High Voltage (EHV) transmission lines to reduce the voltage gradient at the conductor surface, thereby minimizing corona loss and radio interference ┬╖ Physically, this arrangement increases the Geometric Mean Radius (GMR) of the conductor bundle, which effectively increases the shunt capacitance to ground.
Bundled conductors are used in Extra High Voltage (EHV) transmission lines to reduce the voltage gradient at the conductor surface, thereby minimizing corona loss and radio interference ┬╖ Physically, this arrangement increases the Geometric Mean Radius (GMR) of the conductor bundle, which effectively increases the shunt capacitance to ground.
C=ln(D/DeqтАЛ)2╧А╧╡0тАЛтАЛ тАФ Capacitance of a transmission line
DeqтАЛ=nrтЛЕd1тАЛтЛЕd2тАЛ...тАЛ тАФ Geometric Mean Radius of a bundle of n conductors
The capacitance of a transmission line is inversely proportional to the logarithm of the ratio of the spacing between conductors to the GMR ┬╖ By bundling multiple conductors per phase, the equivalent GMR (DeqтАЛ) increases significantly ┬╖ Since the capacitance C is proportional to 1/ln(D/DeqтАЛ), an increase in DeqтАЛ results in an increase in the total capacitance of the line.
Bundled conductors reduce corona discharge by decreasing the maximum surface voltage gradient.
The overall effective diameter of the phase conductor increases.
Increased capacitance leads to higher charging currents in long transmission lines.
Bundling reduces the overall line inductance due to the increase in the effective radius (GMR).
Reduced corona loss
Reduced radio interference
Decreased line inductance
Increased power transmission capability
Increased capacitance leads to higher Ferranti effect
Higher wind and ice loading on towers
Increased cost due to more hardware and spacers
400 kV and 765 kV transmission networks
Long-distance UHVAC power lines
The reduction in inductance and increase in capacitance improves the Surge Impedance Loading (SIL) of the line.
Option A is incorrect because bundling always increases capacitance ┬╖ Option C is incorrect because bundling reduces inductance ┬╖ Option D is incorrect because the primary purpose is to lower the surface voltage gradient.
B is correct тАФ Bundled conductors increase the effective radius of the phase, which directly increases the line capacitance.
Always remember that bundling increases capacitance and decreases inductance; this shifts the surge impedance Z0тАЛ=L/CтАЛ lower, increasing the power transfer capacity of the line.