b) A fault occurs at bus 4 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 + j0 p.u, and the impedance of the electric arc is neglected (Zf = 0 + j0 p.u.). The positive, negative and zero sequence impedance parameters of the generator, transmission lines and transformer are given in Figure Q3.   (i) Determine the positive sequence fault current for the case when a three-phase-to-ground fault occurs at bus 4 of the network   (ii) Determine the short-circuit fault current for the case when a one-phase- to-ground fault occurs at bus 4. Recall that phasors can be expressed in terms of their symmetrical components as shown in the picture attached. where F stands for any three-phase quantity (e.g., current, voltage)   (iii) Determine the short-circuit fault current for the case when a phase-to-phase fault occurs at bus 4

1. Consider a single-phase 11 KV/0.11 kV 1.1 MVA transformer protected by percentage differential protection. CTs with 5 A secondaries are used. It is known that the magnetizing currents of the two CTs, for maximum external fault current, differ by 0.5 A. Assuming no other source of error and a minimum pick-up of 0.01 A, find the minimum percentage bias setting so that the scheme remains stable on maximum external fault current.

The single line diagram of a power system is shown in Figure Q2.1 includinggenerator and transformer winding connection and earthing details. The parametersfor this system have been calculated on a common 100 MVA base and are given inTable Q2.1. All resistances and shunt susceptances are neglected. This systemexperiences a single line to ground fault at a point F on line L1. The point F is at adistance d from Bus 4 along the line L1. The total length l of the line L1 is 50 km.Note that the location of d is not drawn to scale in Figure Q2.1. The fault current atthe fault point F is measured to be 6.106 kA. i) Determine the zero, positive, and negative sequence Thevenin equivalentimpedances as seen at the fault point F. These should be evaluated in per unitand shown as a function of d.ii) Use the sequence impedances calculated in part (i) to determine the distance dof the fault (in km) from Bus 4.  It's different from the answer, please don't send it

Figure 2 shows the circuit of a simple power system. The ratings of the generators, transformers and the motors are as shown in the figure. The reactance of lines 1 and 2 are 40 ohms and 50 ohms respectively. Assume that system is unloaded, and the generators are generating their rated voltage. Select the generator G₁ ratings as base values. Choose the fault location in bus 3. And give the bellow answer For a symmetrical three phase fault on the bus 3 1. Calculate the fault current in ampere and fault power in MVA and the fault current contribution from the generator connected to the bus 3.