Suppose V-1.0°p.u., z= j0.50 p.u., z z-jo.25 p.u.; draw a sequence network cannection in case of bolted (phase) Line-to-line (phase) fault. Determine the fault current and the bus voltage at the fault point.

A hydro powered 50 MVA generator, with a synchronous reactance 0.33 p.u., delivers 40 MW over a transmission line of 0.15 p.u. reactance to an infinite system. A 3-phase short circuit transient fault occurs on the busbar between the generator and transmission line. Given that the generator emf is 1.4 p.u. prior to and during the fault and all reactances are to a 50 MVA base: Sketch the single line schematic diagram of the system. Determine the maximum load angle the generator can swing to without losing stability. i) ii) iii) iv) Sketch the corresponding power-angle curve for the system showing the accelerating and decelerating areas. Calculate the critical clearing angle of the system to keep its stability.

Q2\ The one-line diagram of a simple power system is shown in figure below. All impedances are expressed in per unit (pu) on a common MVA base. All resistances and shunt capacitances are neglected. The generators are operating on no load at their rated voltage. A three-phase fault occurs at bus 1 through a fault impedance of Zf = j0.08 per unit. Using Thevenin's theorem obtain the impedance to the point of fault and the fault current in per unit. Determine the bus voltages and line currents of generators during fault. X₁ = = 0.1 XT-0.1 3 1 to ojo XL=0.2 2 040 X₁ = 0.1

Q3/ For the system shown in figure. The generator is supplying 1.0 pu MW power under prefault condition. When three-phase fault occur at point F. What should the value of fault reactance must be to make the critical clearing angle equal to 58.9. Sc j0.1 j0.1 10.21 BE j0.38 38 j0.21 IEgl-12 pu 10.19 F 10.19 IVI-1.00 pu j0.1 j0.1 Q4/ Figure below shows the one-line diagram

Q. when a three-phase fault occurs at 75% of the distance from bus G. This fault has 10 arc resistance. 100 MVA, 115 KV Line GH a-Assume that the angle of the mho characteristic is 70°.Determine if the zone I mho unit at H set for 90% of the line GH can operate for this fault. b-Determine the apparent impedance seen by the distance relays at H for this fault. G Z, = 0.365 Z83° - 80% l6 = 1.96 Z–31.42° 4 = 2.60 Z–47.76° ķ = 4.51 Z-40.68° All values in per unit on 100 MVA, 115 kV.