Consider the following statements regarding Corona:1.It causes radio interference.2.It attenuates lightning surges.3.It causes power loss.4.It is more prevalent in the middle conductor of a transmission line employing flat conductor configuration.Which of the above statements are correct?

Correct Answer: C - 1, 2, 3 and 4

Quick Concept Explanation

Corona is ionization of air around an overhead conductor when surface electric field exceeds the disruptive critical value. It causes power loss, audible noise and radio interference, but can attenuate steep lightning surges by dissipating energy. Key relation: Peek-type relation: corona loss rises strongly with (V−V_c)² once V>V_c.

Exam focus: Larger conductor diameter and spacing generally raise corona inception voltage. Common trap: Do not confuse corona with skin effect inside the conductor.

Statement-wise Verification

• Statement 1 - Correct.
  It causes radio interference.
  It causes power loss, audible noise and radio interference, but can attenuate steep lightning surges by dissipating energy.
• Statement 2 - Correct.
  It attenuates lightning surges.
  Can attenuate steep lightning surges by dissipating energy.
• Statement 3 - Correct.
  It causes power loss.
  It causes power loss, audible noise and radio interference, but can attenuate steep lightning surges by dissipating energy.
• Statement 4 - Correct.
  It is more prevalent in the middle conductor of a transmission line employing flat conductor configuration.
  Larger conductor diameter and spacing generally raise corona inception voltage.

Core Concept

Corona is ionization of air around an overhead conductor when surface electric field exceeds the disruptive critical value. It causes power loss, audible noise and radio interference, but can attenuate steep lightning surges by dissipating energy. Surface electric stress is influenced by conductor radius, spacing, surface condition, air density and weather.

Formula / Key Relationship

Peek-type relation: corona loss rises strongly with (V−V_c)² once V>V_c.

Why the Other Options Are Wrong

Option A is incorrect because it omits correct statement(s) 4. Option B is incorrect because it omits correct statement(s) 3. Option D is incorrect because it omits correct statement(s) 1, 2.

Exam Shortcut / Approach

Larger conductor diameter and spacing generally raise corona inception voltage.

Common Mistake

Do not confuse corona with skin effect inside the conductor.

Quick Revision

Corona Effects on Overhead Lines is linked with Corona, Transmission Lines and Power Systems. Larger conductor diameter and spacing generally raise corona inception voltage.