Consider a power system shown below:
Given that:
${V}_{s1}={V}_{s2}=1.0+j0.0\mathrm{pu}$;
The positive sequence impedences are ${Z}_{s1}={Z}_{s2}=0.001+j0.01\mathrm{pu}$ and ${Z}_{L}=0.006+j0.06\mathrm{pu}$.
3-phase Base MVA=100
Voltage base=400kV (Line to Line)
Nominal system frequency = 50Hz
The reference coltage for phase 'a' is defined as $v\left(\mathrm{t}\right)\mathit{=}{V}_{\mathit{m}}\mathrm{cos}\left(\mathit{\omega}\mathit{t}\right)$.
A symmetrical three phase fault occurs at centre of the line., i.e. point 'F' at time t_{0}. The positive sequence impedance from source S_{1} to point 'F' equals $\mathit{0}\mathit{.}\mathit{004}\mathit{+}j\mathit{0}\mathit{.}\mathit{04}\mathit{}\mathrm{pu}$. The waveform corresponding to phase 'a' fault current from bus X reveals that decayinf dc offset current is negative and in magnitude at its maximum initial value. Assume that the negative sequence impedances are equal to positive sequence impedances, and the zero sequence impedances are three times positive sequence impedances.
Instead of the three phase fault, if a single line to ground fault occurs on phase ‘a’ at point ‘F’ with zero fault impedance, then the rms of the ac component of fault current (Ix) for phase ‘a’ will be