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Surge impedance loading of a single circuit of 220 kV line is
120 MW
90 MW
220 MW
400 MW
120 MW
Surge Impedance Loading (SIL) is defined as the power delivered by a lossless transmission line to a load resistance equal to the surge impedance of the line. For a 220 kV transmission line, the SIL is approximately 120 MW, assuming typical overhead line parameters.
Surge Impedance Loading (SIL) is defined as the power delivered by a lossless transmission line to a load resistance equal to the surge impedance of the line. For a 220 kV transmission line, the SIL is approximately 120 MW, assuming typical overhead line parameters.
SIL=ZsтАЛVLтИТL2тАЛтАЛ тАФ Power delivery at unity power factor and flat voltage profile
ZsтАЛ=CLтАЛтАЛ тАФ Surge impedance of the transmission line
SIL occurs when the reactive power consumed by the line inductance (I2XLтАЛ) is exactly equal to the reactive power generated by the line capacitance (V2/XCтАЛ). At this loading point, the voltage profile along the line remains flat, and the line operates at unity power factor, minimizing reactive power losses.
SIL is independent of line length.
At SIL, the transmission line is neither a source nor a sink of reactive power.
For standard overhead lines, surge impedance (ZsтАЛ) is typically taken as 400╬й.
Calculation: (2202)/400=48400/400=121 MW, which aligns with 120 MW.
Minimizes voltage fluctuations along the line.
Optimizes the transmission capacity of the network.
If load > SIL, the line consumes reactive power, causing voltage drop.
If load < SIL, the line produces reactive power, causing Ferranti effect.
Planning and operation of EHV/UHV transmission systems.
Determining the compensation requirement for long-distance lines.
The value of ZsтАЛ varies slightly based on conductor configuration, typically ranging from 350╬й to 450╬й.
Options B, C, and D are incorrect as they represent power levels that do not correspond to the surge impedance loading criteria for a 220 kV nominal system.
A is correct тАФ The surge impedance loading is calculated as the ratio of the square of the line-to-line voltage to the surge impedance, yielding approximately 120 MW for a 220 kV line.
Always remember that SILтИЭV2; doubling the voltage increases the SIL by four times, which is a critical design factor in high-voltage engineering.