The valid positive, negative and zero sequence impedance (in p.u.), respectively, for a 220 kV, fully transposed three-phase transmission line, from the given choices are

The correct option is 0.15, 0.15 and 0.35.

To understand why this is the correct set of sequence impedances, let us analyze the characteristics of a fully transposed three-phase transmission line:

1. Positive and Negative Sequence Impedances:
For static, symmetrical, and fully transposed transmission lines, the magnetic coupling and electric field symmetry are identical regardless of the phase sequence of the currents. Therefore, the impedance offered to positive sequence currents is equal to the impedance offered to negative sequence currents.
Thus, we have:
$Z_1=Z_2$

2. Zero Sequence Impedance:
Zero sequence currents are in phase in all three conductors. Because they flow in the same direction at any given instant, they must return through the earth or ground wires. This ground return path has a significantly higher impedance due to the larger loop area of the return path and the resistivity of the earth. In addition, the mutual magnetic coupling between the phases reinforces the impedance for zero-sequence currents.
Consequently, the zero sequence impedance is always much larger than the positive and negative sequence impedances for a transmission line. Typically:
$Z_0\approx 2to3.5\times Z_1$

3. Analyzing the Choices:
Let us evaluate each of the given options based on these rules:
- Option 1 (0.15, 0.15 and 0.35): Here, $Z_1=Z_2=0.15$ p.u., and $Z_0=0.35$ p.u., which satisfies $Z_1=Z_2$ and $Z_0>Z_1$. This is physically valid.
- Option 2 (0.2, 0.2 and 0.2): Here, $Z_0=Z_1=Z_2$. This is only true for purely static balanced loads without ground paths, not for transmission lines.
- Option 3 (1.1, 0.15 and 0.08): Here, $Z_1\ne Z_2$ and $Z_0$ is smaller than $Z_1$, which is incorrect.
- Option 4 (0.1, 0.3 and 0.1): Here, $Z_1\ne Z_2$, which violates the transposition condition.

Therefore, the only valid set of positive, negative, and zero sequence impedances is 0.15, 0.15 and 0.35.