1) A dc 2-wire distributor AB is 500m long and is fed at both the ends at 240V. The loads of 100 A and 60 A are tapped from C and D that are at the distance of 100m and 250m from point A respectively. The last 200m (near end B) is loaded uniformly at rate of 1 A/m. The resistance of (both go and return) the distributor is 0.001 ohm per metre. Determine the point of minimum potential and its value.
2) An electric train runs between the two substations 6 km. apart maintained at voltages 600 V and 590 V respectively and sketch a constant current of 300 A while in motion. The track resistance of go and return path is 0.04 ohm/km. Determine:
a) The point of minimum potential along the track.
b) Currents that are supplied by the two substations when the train is at the point of minimum potential
3) a) Deduce an expression for the critical disruptive voltage?
b) A 3-phase line has the conductors 2 cm. in diameter spaced equilaterally 1m apart. If dielectric strength of air is 30 kV (max) per cm, find out the disruptive critical voltage for the line. Consider the air density factor δ = 0.952 and the irregularity factor m0 = 0.9
4) A 3 phase, 50 Hz,, 132 kV overhead line has regularly transposed conductors equilaterally spaced 3 m. apart. Conductor diameter is 2 cm. If the line length is 100 km., determine the charging current per phase. Find the capacitance of the same line taking into account the effect of earth. The height of conductors above the ground is 7m.