Surge Impedance Loading (SIL)

SIL refers to the maximum power that can be transmitted through a transmission line without causing excessive voltage fluctuations or damage to the line. It is typically expressed in megawatts (MW) and is influenced by factors such as line length, voltage level, and line parameters.

Given Information
- Voltage level: 400 kV
- Frequency: 50 Hz
- Line type: Overhead single circuit transmission line

Calculating Surge Impedance

The surge impedance of a transmission line can be calculated using the formula:

SIL = (V^2) / Zs

Where:
- SIL is the surge impedance loading
- V is the line voltage
- Zs is the surge impedance of the line

The surge impedance of a transmission line can be calculated using the formula:

Zs = (V^2) / S

Where:
- Zs is the surge impedance
- V is the line voltage
- S is the line charging capacity

Calculating Surge Impedance Loading

To calculate the surge impedance loading, we need to determine the surge impedance first. The line charging capacity, S, is typically given in pico-farads per kilometer (pF/km) and can be approximated using empirical formulas.

Since the line is a 400 kV, 3-phase transmission line, we can assume an approximate value for S. For a 400 kV line, the typical value of S is around 0.1 pF/km.

Considering the line length can be assumed to be 100 km (for simplicity), we can calculate the surge impedance using the formula:

Zs = (V^2) / S
= (400,000^2) / (0.1 x 100)
= 160,000,000 / 10
= 16,000,000 ohms

Now that we have the surge impedance, we can calculate the surge impedance loading using the formula:

SIL = (V^2) / Zs
= (400,000^2) / 16,000,000
= 160,000,000,000 / 16,000,000
= 10,000 MW

Therefore, the approximate value of the surge impedance loading for a 400 kV, 3-phase 50 Hz overhead single circuit transmission line is 10,000 MW.

Conclusion

The correct answer is option B, 400 MW, which is incorrect. The correct answer is 10,000 MW.