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Proximity effect is more in case of
Overhead line
Power cable
DC transmission
None of the above
Power cable
The proximity effect is the tendency of current to distribute non-uniformly in a conductor due to the magnetic fields generated by nearby conductors. In power cables, conductors are placed much closer together than in overhead lines, leading to higher magnetic flux linkage interaction and a significantly more pronounced proximity effect.
The proximity effect is the tendency of current to distribute non-uniformly in a conductor due to the magnetic fields generated by nearby conductors. In power cables, conductors are placed much closer together than in overhead lines, leading to higher magnetic flux linkage interaction and a significantly more pronounced proximity effect.
RacтАЛ=RdcтАЛ(1+ksтАЛ+kpтАЛ) тАФ where kpтАЛ represents the proximity effect coefficient, RacтАЛ is effective AC resistance, and RdcтАЛ is DC resistance.
When alternating current flows through conductors placed in close proximity, the magnetic field produced by one conductor induces eddy currents in the adjacent conductors. This magnetic interaction restricts the current flow to specific sides of the conductors, effectively increasing the internal resistance of the cable. As the spacing between conductors decreases, the magnetic field interaction intensity increases inversely with the distance between them, thus maximizing the effect in tightly bundled power cables.
The proximity effect is negligible in DC systems because magnetic fields produced by DC are constant, resulting in zero eddy current induction.
Higher frequency currents intensify both skin effect and proximity effect due to faster magnetic flux variations.
Proximity effect reduces the effective cross-sectional area available for current flow, thereby increasing the electrical resistance.
It is more severe in cables where insulation keeps conductors in close contact compared to overhead lines where phase spacing is typically meters apart.
Understanding proximity effect helps in accurate cable ampacity (current-carrying capacity) calculation.
Promotes optimal design of cable geometry to minimize power loss.
Increases I2R power losses in conductors.
Causes non-uniform temperature distribution within the cable insulation.
Submarine power cable design
Underground distribution systems
High-voltage transmission cabling
Overhead lines have significant inter-phase spacing (often 1-5 meters), which minimizes the magnetic field interaction between conductors.
Power cables are typically enclosed within a single sheath, forcing a very small distance between phases, which is the primary reason for the high proximity effect.
Option C is incorrect because proximity effect relies on time-varying magnetic fields; constant DC fields do not induce eddy currents.
B is correct тАФ Power cables exhibit a stronger proximity effect due to the very small spacing between conductors compared to overhead transmission lines.
Always remember that the proximity effect and skin effect both increase with frequency and conductor proximity, making them critical considerations for AC power cable design but generally ignored in long-distance overhead transmission.