A DC ring main ABCDA is fed from point A from a $300$ V supply, as shown in Figure $Q4.a,$ and the resistances $($including both lead and return$)$ of various sections are as follows:

$AB=0\mathrm{.}025,BC=0\mathrm{.}025,CD=0\mathrm{.}025$ and $DA=0\mathrm{.}025.$

The main supplies loads of $300$ A at $B,300A$ at C and $200$ A at D $.$

Determine the voltage at each load point.

If the points A and C are linked through an interconnector of resistance $0\mathrm{.}02$ as shown in Figure Q$4.$b$,$ determine the new voltage at each load point.

$($b$)$

Figure O$4$