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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Natural impedance of line is represented by
Z=(L/C)1/2
Z=(L/R)1/2
Z=(R/C)1/2
Z=(R/L)1/2
Z=(L/C)1/2
Quick Summary: The natural impedance (also known as surge impedance) of a transmission line is defined as the square root of the ratio of its series inductance (L) to its shunt capacitance (C). It represents the characteristic impedance of a lossless line where the line is terminated to avoid reflections.
The natural impedance (also known as surge impedance) of a transmission line is defined as the square root of the ratio of its series inductance (L) to its shunt capacitance (C). It represents the characteristic impedance of a lossless line where the line is terminated to avoid reflections.
Z0=CL — Natural Impedance formula
PSIL=Z0V2 — Surge Impedance Loading (SIL)
For a lossless line, the propagation constant is purely imaginary, and the impedance is independent of frequency. It is derived from the transmission line equations Z=YZ=G+jωCR+jωL. By neglecting resistance (R) and conductance (G), the expression simplifies to CL.
Also referred to as Characteristic Impedance in lossless transmission lines.
The value typically ranges between 350-450 Ohms for overhead lines.
It is a purely resistive value when the transmission line is lossless.
SIL is the power delivered by a line when it is terminated by its surge impedance.
Helps in determining the loadability of transmission lines.
Useful in transient analysis and protection coordination.
Not constant in practical lines due to losses (R and G).
Assumes uniform line distribution.
Transmission line steady-state stability studies.
Protection of power systems against switching surges.
Designing compensating reactors for long lines.
Option B, C, and D are dimensionally incorrect and do not represent any standard line characteristic.
For cables, the capacitance (C) is much higher, leading to a much lower surge impedance compared to overhead lines.
A is correct — The natural impedance (surge impedance) of a line is defined by the formula Z=CL.
Remember that SIL (Surge Impedance Loading) is inversely proportional to Z0; therefore, increasing the line voltage or decreasing Z0 significantly increases the power carrying capacity.