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Transmission lines are transposed to
Reduce copper loss
Reduce skin effect
Prevent interference with neighbouring telephone lines
Prevent short-circuit between any two lines.
Prevent interference with neighbouring telephone lines
Transposition of transmission lines involves exchanging the physical positions of conductors at regular intervals along the length of the line ┬╖ This practice is primarily employed to balance the line parameters, specifically the series inductance and shunt capacitance of each phase, thereby ensuring the line remains electrically symmetrical over its entire length.
Transposition of transmission lines involves exchanging the physical positions of conductors at regular intervals along the length of the line ┬╖ This practice is primarily employed to balance the line parameters, specifically the series inductance and shunt capacitance of each phase, thereby ensuring the line remains electrically symmetrical over its entire length.
LavgтАЛ=2├Ч10тИТ7ln(GMRGMDтАЛ) тАФ Formula for average inductance per phase
CavgтАЛ=ln(GMD/reqтАЛ)2╧А╧╡тАЛ тАФ Formula for average capacitance per phase
In an untransposed three-phase line, the unequal distances between conductors result in unequal mutual inductances and capacitances, leading to unbalanced line voltage drops ┬╖ By transposing the conductors, each phase conductor occupies all three physical positions (e.g., top, middle, bottom) for equal distances ┬╖ This averaging effect ensures that the total inductive and capacitive coupling to nearby parallel circuits, such as telephone lines, is minimized, preventing electromagnetic and electrostatic interference (crosstalk).
Transposition balances line parameters to ensure voltage drops are equal across phases.
It helps in reducing negative and zero sequence current components in the system.
It eliminates the communication interference caused by unbalance in power lines.
Required primarily for long high-voltage transmission lines.
Reduced electromagnetic/electrostatic interference with communication circuits.
Balanced voltage and current distribution across phases.
Minimal zero-sequence impedance impact.
Increased tower complexity at transposition points.
Higher maintenance requirements at transposition towers.
Additional insulation requirements at the switching point.
High-voltage (HV) and Extra High Voltage (EHV) overhead transmission lines.
Long-distance power transmission systems.
Lines running parallel to communication or signaling circuits.
Option A is incorrect because copper loss depends on resistance (I2R), which is a material property, not a geometric arrangement issue.
Option B is incorrect because skin effect is controlled by conductor diameter and frequency, not physical transposition.
Option D is incorrect because short-circuit protection is achieved via insulators and clearance standards, not transposition.
C is correct тАФ Transposition balances the line parameters, effectively canceling out the induced voltages in neighboring communication circuits to prevent interference.
Remember that transposition is essentially a spatial averaging technique to restore symmetry in an asymmetrical three-phase geometric configuration.