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 presence of corona, electrostatic coupling and electromagnetic coupling
Decreases, increases
Increases, decreases
Increases, remains same
Remains same, decreases
Increases, remains same
Corona discharge effectively increases the diameter of the transmission conductor due to the formation of a conducting ionized sheath, which increases the capacitance to ground and hence electrostatic coupling. Electromagnetic (inductive) coupling, which depends on the permeability of the medium and the geometry of the current path, remains largely unaffected by the local ionization of air near the conductor surface.
Corona discharge effectively increases the diameter of the transmission conductor due to the formation of a conducting ionized sheath, which increases the capacitance to ground and hence electrostatic coupling. Electromagnetic (inductive) coupling, which depends on the permeability of the medium and the geometry of the current path, remains largely unaffected by the local ionization of air near the conductor surface.
C=ln(D/reffтАЛ)2╧А╧╡0тАЛтАЛ тАФ Capacitance increases as effective radius reffтАЛ increases
M=2╧А╬╝0тАЛтАЛln(D/d) тАФ Mutual inductance remains independent of corona ionization
When the electric field intensity at the surface of a conductor exceeds the dielectric strength of air (тЙИ30kV/cm peak), ionization occurs, creating a space charge region. This ionized sheath increases the effective radius of the conductor (reffтАЛ>ractualтАЛ), modifying the electric field distribution and increasing the line-to-ground capacitance. Since electromagnetic coupling depends primarily on mutual inductance M, which is a function of the path geometry and the permeability mu0тАЛ, the minor change in electrical radius does not significantly alter the magnetic coupling.
Corona causes air ionization, creating a virtual increase in conductor radius.
Electrostatic coupling is capacitive; it is highly dependent on the geometry and effective conductor diameter.
Electromagnetic coupling is inductive; it is determined by the magnetic field distribution linked to the current.
Corona loss is a non-linear phenomenon that increases with applied voltage.
Increased effective radius reduces peak surface electric field gradient.
Acts as a protective mechanism by dissipating surges in some contexts.
Causes significant power loss on transmission lines.
Generates radio frequency interference (RFI) and audible noise.
High Voltage AC (HVAC) transmission line design.
Design of bundled conductors to mitigate corona effects.
Corona occurs when the voltage gradient exceeds the critical disruptive voltage of the dielectric medium.
Option B is incorrect because electromagnetic coupling is insensitive to electrostatic changes like corona.
C is correct тАФ In the presence of corona, the effective conductor radius increases, leading to an increase in electrostatic coupling while electromagnetic coupling remains unaffected.
Always distinguish between capacitive coupling (voltage/field dependent) and inductive coupling (current/field dependent) when analyzing transmission line transients.