Q5. A 50 Hz generation station is connected to an infinite bus through two lines as shown in Fig. 5. The system data in Fig. Q5 is given in per-unit on a common base. Machine inertia constant: H = 4 s. The power transfer from the generator to the infinite bus (busbar B3) is 0.9 pu. The fault on transmission line (either on Line-1 or Line-2) is cleared by opening line breakers at the same time. B3 B2 CB1 X's=20.3 B1 Line-1 (X1 = j0.6) CB2 j0.15 SM CB3 Line-2 (X2 =j0.4) CB4 E'] = 1.15 pu Inf. Bus | Vinf (= 1 pu Fig. Q5 Single machine - infinite bus system (a) Draw the power-angle curve and show the operating point. (2 marks) (b) Determine the frequency of machine rotor oscillations when it is subjected to a small temporary electrical disturbance. (4 marks) (c) Consider three phase metallic faults on transmission lines (either Line-1 or Line-2). For which fault location (or locations), the critical clearing time will be the smallest? Write down the reason briefly (do NOT use the equation of critical clearing angle and/or time in your explanation). (4 marks) (d) Calculate the critical clearing angle for the fault location specified in (c). (3 marks) (e) For the fault location specified in (c), plot approximately the power-angle curves of the generator. Indicate the pre-fault, critical clearing and maximum angles, and the acceleration and deceleration areas. (4 marks) (f) Suppose that the fault clearing time (te) is 100 ms. What will be the rotor angular displacement (from synchronously rotating reference axis)? Is the system stable for the 100 ms fault clearing time? (3 marks) _(8m-8) sin(8.) r, cos(8)+r, cos(8m) cos(8)= (rz-r) do, Ocr, and Om are the pre-fault, critical clearing and maximum angles, respectively. Pmaxi/Pmax and r2 = Pmax2/Pmax. ri = Q5. A 50 Hz generation station is connected to an infinite bus through two lines as shown in Fig. 5. The system data in Fig. Q5 is given in per-unit on a common base. Machine inertia constant: H = 4 s. The power transfer from the generator to the infinite bus (busbar B3) is 0.9 pu. The fault on transmission line (either on Line-1 or Line-2) is cleared by opening line breakers at the same time. B3 B2 CB1 X's=20.3 B1 Line-1 (X1 = j0.6) CB2 j0.15 SM CB3 Line-2 (X2 =j0.4) CB4 E'] = 1.15 pu Inf. Bus | Vinf (= 1 pu Fig. Q5 Single machine - infinite bus system (a) Draw the power-angle curve and show the operating point. (2 marks) (b) Determine the frequency of machine rotor oscillations when it is subjected to a small temporary electrical disturbance. (4 marks) (c) Consider three phase metallic faults on transmission lines (either Line-1 or Line-2). For which fault location (or locations), the critical clearing time will be the smallest? Write down the reason briefly (do NOT use the equation of critical clearing angle and/or time in your explanation). (4 marks) (d) Calculate the critical clearing angle for the fault location specified in (c). (3 marks) (e) For the fault location specified in (c), plot approximately the power-angle curves of the generator. Indicate the pre-fault, critical clearing and maximum angles, and the acceleration and deceleration areas. (4 marks) (f) Suppose that the fault clearing time (te) is 100 ms. What will be the rotor angular displacement (from synchronously rotating reference axis)? Is the system stable for the 100 ms fault clearing time? (3 marks) _(8m-8) sin(8.) r, cos(8)+r, cos(8m) cos(8)= (rz-r) do, Ocr, and Om are the pre-fault, critical clearing and maximum angles, respectively. Pmaxi/Pmax and r2 = Pmax2/Pmax. ri =
