Q5Power System - I
Question
Q.5. Describe term corona. What are the factors which affect the corona losses?
Answer
Corona is the localized ionization of air around a high-voltage conductor when the surface voltage gradient exceeds the breakdown strength of air, producing a visible glow, hissing sound and power loss; it is affected by conductor size, spacing, surface condition, atmospheric conditions and system voltage.
Corona is the phenomenon of localized ionization/breakdown of the air surrounding a high-voltage transmission line conductor, occurring when the electric field intensity at the conductor surface exceeds the dielectric strength of air, producing a faint violet glow, a hissing/crackling sound, ozone formation, and a continuous power loss (corona loss). Factors affecting corona losses include: atmospheric conditions (humidity, rain and fog reduce the disruptive critical voltage, increasing corona); conductor surface condition (rough, dirty or damaged conductors corona more readily than smooth, clean ones); conductor size/radius (larger-diameter conductors have lower surface stress for the same voltage, reducing corona); spacing between conductors (wider spacing reduces surface stress, reducing corona); and system voltage (corona increases sharply once operating voltage exceeds the critical disruptive voltage of the line).