During a power failure, a domestic household uninterruptible power supply (UPS) supplies AC power to a limited number of lights and fans in various rooms. As per a Newton-Raphson load-flow formulation, the UPS would be represented as a

The bus impedance matrix of a 3-bus system (in $pu$) is $Z{\text{bus}} = \begin{bmatrix} j0.059 & j0.061 & j0.038 \\ j0.061 & j0.093 & j0.066 \\ j0.038 & j0.066 & j0.110 \end{bmatrix}$ A symmetrical fault (through a fault impedance of $j0.007\ pu$) occurs at bus 2. Neglecting pre-fault loading conditions, the voltage at bus 1, during the fault is \\\\\\\\\\\ $pu$ (round off to three decimal places).