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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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As compared to sending end voltage, the receiving end voltage of a short line under no load condition is
Higher
Lower
Remains same
Insufficient data
Remains same
Quick Summary: In a short transmission line, the effect of capacitance is neglected. Under no-load conditions, no current flows through the series impedance (resistance and inductance), meaning there is no voltage drop across the line; thus, the receiving end voltage equals the sending end voltage.
In a short transmission line, the effect of capacitance is neglected. Under no-load conditions, no current flows through the series impedance (resistance and inductance), meaning there is no voltage drop across the line; thus, the receiving end voltage equals the sending end voltage.
VS=VR+I(R+jXL) — Voltage relation for a short transmission line
I=0 — Current condition at no-load
The short transmission line is modeled as a series combination of resistance (R) and inductance (L). According to Ohm's law, the voltage drop across the line is Vdrop=Iload×Zline, where Zline=R+jXL. At no-load, Iload=0, leading to Vdrop=0. Consequently, VR=VS−0=VS.
Short lines are defined as having a length less than 80 km or voltage below 20 kV.
Capacitance is neglected in short lines due to its small effect compared to series impedance.
The Ferranti effect, which causes VR>VS, is only observed in long transmission lines due to the charging current flowing through the line capacitance.
Under no-load, the voltage regulation of a short transmission line is theoretically zero.
Distribution network modeling
Rural electrification studies
Long lines experience the Ferranti Effect due to shunt capacitance, where the receiving end voltage at no-load is higher than the sending end voltage.
Option A is incorrect because it describes the Ferranti effect, which is negligible in short lines.
C is correct — Since there is no current flowing through the series impedance of a short line at no-load, the voltage drop is zero, resulting in VR=VS.
Always differentiate between line lengths; Ferranti effect (VR>VS) is a signature characteristic of long lines under light load or no-load, not short lines.