Open Circuit Breaker B52. Using per unit and symmetrical component analysis, calculate the power system fault currents at Bus 2 (Line 2 out of service) for the Ø-G faults 400 MVA 15 kV B1 T1 T2 Ak 400 MVA 15/345 kV LV Δ Δ 851 0- HV Y Y 04 852 345 KV 100 mi 821 2 Line 2 Gen Xd" (per unit) X2 (per unit) 1 0.225 0.225 2 0.20 0.20 Transformer Data: Line 3 345 kV 50 mi 280 Mvar o Xpu (+/-/0) 0.06 0.05 Line 1 841 0 842 345 KV 200 mi 822 800 MW T2 800 MVA 345/15 kV XO (per unit) 0.0625 0.045 83 40 Mvar 80 MW 800 MVA 15 kV Sbase=100MVA Vbase Bus1 = 15kV Vbase Bus 3 = 15kV Vbase Lines = 345kV Neutral Reactance (pu) Xd' (per unit) Solidly grounded 0.45 0.20 0.40

The subject is: Smart Grid Applications and Technologies

Figure below shows the single-line diagram of three-bus power system with generation at bus 1 and bus 3. The voltage at bus 1 is V₁ = 1.025/0° per unit. The voltage magnitude at bus 3 is fixed at 1.05 per unit with a real power generation of 250 MW. The scheduled load on bus 2 is marked on the diagram. Line impedances are marked in per unit on a 100 MVA base. Line resistances and line charging susceptances are neglected. By using Gauss-Seidel method and initial estimates of V₂(0) = 1.020° and V3(0) = 1.0520°, determine V₂ and V3. Perform calculation for one iteration. V₁ = 1.025/0° j0.1 Slack Bus j0.2 j0.4 j0.2 3 j0.1 250 MW 150 Mvar |V3|=1.05 P3 = 250 MW

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.