Question

The surge impedance value of overhead lines is
1. 50 to 100 ohms
2. 400 to 600 ohms
3. 800 to 1000 ohms
4. 10 to 50 ohms

Answer 1

Correct Answer - Option 2 : 400 to 600 ohms

The equation for surge impedance is given by

\({Z_s} = \sqrt {\frac{L}{C}} \)

Where L = inductance in henry

C = capacitance in farad

An impedance which renders the line as the infinite line is known as surge impedance. It has a value of about 400 ohms and phase angle varying from 0 to -15 degrees for overhead lines and around 40 ohms for underground cables.

For overhead line surge impedance is given by 400-600 Ω

For underground cable surge impedance is given by 40-60 Ω