Single line diagram of a $$4$$-bus single source distribution system is shown below. Branches $${e_1},\,\,$$ $${e_2},\,\,$$ $${e_3}\,\,$$ and $${e_4}\,\,$$ have equal impedences. The load current values indicated in the figure are in per unit.

Distribution Company's policy requires radial system operation with minimum loss. This can be achieved by opening of the branch

The $$A, B, C, D$$ constant of a $$220$$ $$kV$$ line are:
$$A = D = 0.94\,\angle \,10,\,\,\,B = 130\,\angle \,730,\,\,\,C = 0.001\,\angle \,900.\,\,$$ If the sending end voltage of the line for a given load delivered at nominal voltage is $$240$$ $$kV$$, the % voltage regulation of the line is

At an industrial sub-station with a $$4$$ $$MW$$ load, a capacitor of $$2$$ MVAR is installed to maintain the load power factor at $$0.97$$ lagging. If the capacitor goes out of service, the load power factor becomes

A lightning stroke discharges impulse current of $$10$$ kA (peak) on a $$400$$ kV transmission line having surge impedance of $$250\,\Omega $$. The magnitude of transient over-voltage traveling waves in either direction assuming equal distribution form the point of lightning strike will be