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The square root of the ratio of line impedance and shunt admittance is known as the line
A) Surge impedance
B) Conductance
C) Susceptance
D) Admittance
Surge impedance
The surge impedance (or characteristic impedance) of a transmission line is defined as the square root of the ratio of its series impedance (Z) to its shunt admittance (Y). For a lossless line, it is given by ZcтАЛ=CLтАЛтАЛ, representing the impedance offered to traveling waves.
The surge impedance (or characteristic impedance) of a transmission line is defined as the square root of the ratio of its series impedance (Z) to its shunt admittance (Y). For a lossless line, it is given by ZcтАЛ=CLтАЛтАЛ, representing the impedance offered to traveling waves.
ZcтАЛ=yzтАЛтАЛ=G+j╧ЙCR+j╧ЙLтАЛтАЛ тАФ General form
ZcтАЛ=CLтАЛтАЛ тАФ Lossless transmission line approximation
When a voltage surge propagates along a transmission line, it encounters the distributed parameters of the line. The surge impedance determines the relationship between the voltage and current waves during the propagation of a traveling wave. If a line is terminated with an impedance equal to its surge impedance, all the energy of the traveling wave is absorbed, preventing reflections.
Surge impedance is independent of line length.
For overhead lines, the typical value of surge impedance is approximately 400 ╬й.
For underground cables, the surge impedance is significantly lower, typically 40-60 ╬йdue to higher shunt capacitance.
It is also known as the Characteristic Impedance of the line.
Useful in calculating the reflection and refraction coefficients of surges.
Helps in determining the surge impedance loading (SIL) of the line.
It is not an ohmic resistance; it dissipates no real power in a perfectly lossless line.
Values vary based on line geometry and conductor configuration.
Coordination of insulation levels in power systems.
Analysis of transient overvoltages and switching surges.
Design of line terminations to minimize wave reflection.
SIL (Surge Impedance Loading) is defined as P=ZcтАЛV2тАЛ, which is the power delivered to a load equal to the surge impedance.
Option B (Conductance) represents the leakage current path; Option C (Susceptance) is the reactive part of admittance; Option D (Admittance) is the reciprocal of impedance.
A is correct тАФ Surge impedance is the characteristic impedance of a transmission line, calculated as Z/YтАЛ.
Remember that ZcтАЛ decreases as capacitance increases; this is why underground cables have much lower surge impedance than overhead lines.