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The transmission capacity of a line at 50 Hz as compared to that at 60 Hz is
Lower
Higher
Same
Insufficient data
Higher
The transmission capacity of a line is inversely proportional to the frequency due to the surge impedance loading (SIL) and reactance characteristics. Since reactance XLтАЛ=2╧АfL increases with frequency, a lower frequency leads to lower inductive reactance, allowing higher power transfer capability for a given voltage level.
The transmission capacity of a line is inversely proportional to the frequency due to the surge impedance loading (SIL) and reactance characteristics. Since reactance XLтАЛ=2╧АfL increases with frequency, a lower frequency leads to lower inductive reactance, allowing higher power transfer capability for a given voltage level.
XLтАЛ=2╧АfL тАФ Inductive reactance increases linearly with frequency
PSILтАЛ=ZcтАЛV2тАЛ тАФ Surge impedance loading formula
Transmission lines are limited by the surge impedance ZcтАЛ=CLтАЛтАЛ. The Surge Impedance Loading (SIL) is defined as PSILтАЛ=ZcтАЛV2тАЛ. While V is usually constant, the line's stability and thermal limits are influenced by the inductive reactance XLтАЛ=2╧АfL. As f decreases, the line becomes electrically shorter, reducing the voltage drop across the line for a fixed current, thereby increasing the effective power transfer capacity.
Transmission line reactance XLтАЛ is directly proportional to frequency f.
Lower frequency reduces the reactive voltage drop across the transmission line.
Higher capacity at 50 Hz compared to 60 Hz is a theoretical consequence of reduced series reactance.
Power systems in India operate at 50 Hz, whereas North America operates at 60 Hz.
Reduced reactive losses at lower frequencies
Improved voltage regulation for long-distance lines
Requires larger transformer core sizes (more material)
Increased physical size of electrical machines
Long-distance EHV and UHV transmission lines
Grid stability analysis in power system planning
| Feature | Standard A | Standard B |
|---|---|---|
Frequency | 50 Hz | 60 Hz |
Reactance (XLтАЛ) | Lower | Higher |
In power systems, the term 'transmission capacity' is often associated with the stability limit, which improves as the line's series reactance decreases.
Option A is incorrect because lower frequency does not decrease capacity; Option C is incorrect as frequency directly affects reactance.
B is correct тАФ The transmission capacity is higher at 50 Hz because the inductive reactance of the line is lower compared to 60 Hz.
Always remember that XLтАЛтИЭf and XCтАЛтИЭf1тАЛ; these relations are fundamental for solving questions regarding frequency sensitivity in AC circuits.