Identify Fault Current Relationship

In a Single Line to Ground (SLG) fault, the neutral current ($I_n$) is the sum of the sequence currents of the three phases ($I_a, I_b, I_c$). By symmetrical component theory, $I_a = I_0 + I_1 + I_2$.

$I_n = I_a + I_b + I_c = 3I_0$

Substitute Given Values

We are given the zero sequence current $I_0 = j3$ pu. Substituting this into the formula for neutral current:

$I_n = 3 \times (j3) = j9 \text{ pu}$

Final Calculation

Multiplying the scalar 3 by the imaginary value $j3$ results in $j9$ pu.

$I_n = j9 \text{ pu}$