Short Answer:

Line spacing refers to the distance between conductors in a transmission line. It plays a very important role in controlling corona discharge. When conductors are spaced too closely, the electric field between them becomes very strong, which increases the chances of corona formation. By increasing the line spacing, the electric field intensity is reduced, making it harder for the air around the conductor to get ionized.

Larger line spacing helps reduce corona loss, noise, and radio interference, especially in high-voltage transmission systems. Proper line spacing, along with smooth conductors and bundling, ensures better efficiency and longer life of electrical equipment by keeping corona discharge under control.

Detailed Explanation:

Role of Line Spacing in Minimizing Corona Discharge

Corona discharge occurs when the electric field around a high-voltage conductor becomes strong enough to ionize the surrounding air. This leads to a visible glow, hissing sound, and energy loss. One of the key factors that control the electric field intensity is the spacing between the conductors in a transmission line.

When conductors are placed too close to each other, their electric fields interact more strongly. This increases the electric field strength at the conductor surfaces, making it easier for the air to break down and form corona. On the other hand, wider spacing spreads out the electric field, reducing its intensity and helping to avoid corona formation. Therefore, proper line spacing is critical in high-voltage line design to ensure reliable and loss-free operation.

How Line Spacing Affects Corona Discharge

1. Electric Field Distribution
   • When two conductors are close, their electric fields overlap and reinforce each other.
   • This creates a higher electric field intensity between the conductors and around their surfaces.
   • As a result, the air in the gap gets ionized more easily, causing corona discharge.
2. Reduced Mutual Influence
   • Increasing the distance between conductors reduces their mutual electrical influence.
   • This weakens the electric field at any single point, especially at the outer surface of the conductor.
   • With reduced field intensity, the air remains stable, and ionization is prevented.
3. Effect on Disruptive Critical Voltage
   • Wider line spacing increases the disruptive critical voltage, the voltage at which corona starts.
   • A higher critical voltage means that the transmission line can operate at a higher voltage without corona loss.
4. Better Performance in Bad Weather
   • In wet or humid conditions, corona is more likely to occur.
   • Wider spacing offers an extra safety margin, helping to minimize corona even in unfavorable weather.

Benefits of Proper Line Spacing

1. Reduction in Corona Loss
   • Less electric field intensity means less ionization and lower energy loss through corona.
2. Minimized Audible Noise and Radio Interference
   • Corona creates a hissing sound and high-frequency noise.
   • Proper spacing keeps these effects under control, improving the quality of nearby communication systems.
3. Improved Transmission Efficiency
   • By avoiding corona loss, more electrical energy is delivered to the load without wastage.
4. Increased Safety and Equipment Life
   • Corona can cause insulation damage and corrosion.
   • Reducing corona through proper line spacing protects insulators and conductors, ensuring longer service life.

Practical Considerations in Transmission Line Design

• For extra high voltage (EHV) and ultra-high voltage (UHV) lines, spacing is carefully calculated during the design phase.
• Factors like voltage level, tower design, geographical conditions, and clearance requirements all influence the chosen line spacing.
• Too small spacing increases corona risk and too large spacing increases tower size and cost, so optimal spacing must be maintained.

Engineers often combine proper line spacing with other corona-reducing methods like bundled conductors, smooth conductor surfaces, and corona rings to ensure efficient and safe operation.

Conclusion

Line spacing has a direct and significant role in minimizing corona discharge in transmission systems. By increasing the distance between conductors, the electric field intensity is reduced, preventing air ionization and avoiding corona effects such as power loss, noise, and insulation damage. Correct line spacing ensures better transmission efficiency, longer equipment life, and improved safety. It is a fundamental design element in modern high-voltage transmission networks.