The single line diagram shows a synchronous generator G connected to a large 50 Hz grid via its unit transformer T and a network of three...

length

60

100

80

(a)   Draw the full sequence networks interconnected for a SLG fault at bus 3.

(b)   Find the fault phase currents in p.u. and the phase current contributions in p.u. from the grid as measured at bus 1 and the generator as measured at bus 4. Find also the post fault phase voltages in p.u. at bus 1 and bus 4.

(c)    Repeat (a) and (b) for a single line to ground fault at bus 4.

Work in p.u. throughout using the transformer rating as the common base power. 

Assume prefault internal voltages of the generator and the grid equivalent are 1p.u. at zero phase angle.