Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
In context of corona which statement is not true
Corona is voltage effect
Corona takes place on short transmission line
Corona is accompanied with power loss
Corona attenuates lightening surges
Corona takes place on short transmission line
Corona is a phenomenon of electrical discharge occurring when the voltage gradient at the conductor surface exceeds the dielectric strength of air, typically at approximately $30 kV/cm$ (peak) ┬╖ It occurs primarily on high and extra-high voltage transmission lines, whereas short transmission lines operate at lower voltages where corona effects are negligible.
Corona is a phenomenon of electrical discharge occurring when the voltage gradient at the conductor surface exceeds the dielectric strength of air, typically at approximately $30 kV/cm$ (peak) ┬╖ It occurs primarily on high and extra-high voltage transmission lines, whereas short transmission lines operate at lower voltages where corona effects are negligible.
VcтАЛ=moтАЛgoтАЛ╬┤rln(rdтАЛ) тАФ Disruptive critical voltage formula
PcтАЛ=k(f+25)drтАЛтАЛ(VтИТVcтАЛ)2 тАФ Corona loss power formula
Corona is caused by the ionization of air surrounding the conductor due to a high electric field ┬╖ This ionization produces a glow, hissing sound, and the generation of ozone gas ┬╖ The power loss due to corona is given by Peek's formula, which shows that power loss is significantly dependent on the operating voltage and frequency.
Corona is more prominent on lines operating at $132 kV$ and above.
Air acts as a dielectric; when stress exceeds $30 kV/cm$ (peak), air ionizes.
Corona causes radio interference and audible noise.
Corona reduces the steepness of incoming lightning surges.
Reduces the steepness of incoming surges protecting insulation
Acts as an unintentional safety valve for voltage spikes
Significant power loss on EHV lines
Radio and television interference
Ozone production causes corrosion of hardware
Electrostatic precipitators
Ozone generators
Xerography (Photocopying)
Option B is false because corona is primarily an EHV (Extra High Voltage) phenomenon, not relevant for short distribution/transmission lines.
Corona loss is proportional to (f+25) and thus increases with frequency.
Corona is a voltage effect; it does not occur if the voltage is below the critical disruptive value.
B is correct тАФ Corona is essentially a high-voltage phenomenon observed in long EHV lines and is negligible for short transmission lines due to lower operating voltages.
Always remember that corona power loss (PcтАЛ) is directly proportional to (VтИТVcтАЛ)2. If operating voltage V<VcтАЛ, corona loss is theoretically zero.