Power Systems Homework Help

2. Faults at bus 1 in the previous problem are of interest. Prefault voltage is 1.0 per unit. Prefault load currents and transformer phase shifts are neglected. Determine the Thevenin equivalent of onch soquence actwork as viewed from the fault bus.

3. The generator in Problem 1 is now operating at a new steady-state equilibrium point with PG=1.0 at 0.90 power factor lagging delivered at the infinite bus. Suddenly, circuit breaker B12 inadvertently opens. Determine: (a) the pre-disturbance generator internal voltage, and (b) the maximum value of the generator power angle δ. Hint: use the equal-area criterion to balance the accelerating and decelerating areas.

5. In the previous problem, if breakers B13 and B22 open later than 3 cycles after the fault commences, determine the critical clearing time.

Question-1 Draw the per phase, per unit equivalent circuit for the system shown in Figure. 1. The system MVA base is 100 MVA and the voltage base is 220 kV on the high voltage transmission line section. The equipment nameplate data is given below: G1: 50 MVA, 13.8 kV, X = 15% G2: 25 MVA, 14.4 kV, X = 15% T1: 60 MVA, 13.8: 230 kV, X = 10% T2: 30 MVA, 230: 13.8 kV, X = 10% Line 1: 10+j100 Ohm Line 2: 5+j50 Ohm Line 3: 5+j50 Ohm Load: 75 MVA, 0.9pf lagging

Question-2 Three 5 MVA single-phase transformers, each rated 8:1.39 kV, have a leakage impedance of 5%. These can be connected in a number of different ways to supply three identical 5 Q resistive loads. Various transformer and load connections are outlined in the Table shown below. Complete the table columns. Use a three-phase base of 15 MVA. Clearly show the calculations for each case.

Question-3 Consider the three single-phase two-winding transformers shown in Figure. 2. The high-voltage windings are connected in Y. (a) For the low-voltage side, connect the windings in A, and label the terminals a, b, and c in accordance with the American standard. (b) Relabel the terminals as a', b', and c' such that VAN is 90 out of phase with Va'n for positive sequence.

For the three-phase overhead line shown in the figure below, determine the phase admittance matrix [yabc] and sequence admittance matrix [y012] in µS/mile Phase conductors: 556,500 26/7 ACSR Neutral conductor: 4/0 ACSR

Question An AC source at 60 Hz is supplying 25 kW to a load at a lagging power factor of 0.5. If the rms voltage of the supply is 4 kV what capacitance is required to be hooked up in parallel to the load so that the power factor is raised to 0.8 lagging?

Question 4 An ideal transformer is rated to deliver 430 kVA at 220 V (rms) to a customer, as shown in the figure. How much current, in kA, can the transformer supply to the customer? Question 5 An ideal transformer is rated to deliver 422 kVA at 220 V (rms) to a customer, as shown in the figure. If the customer's load is purely resistive, what is the maximum power, in kW, that the customer can receive? Question 6 An ideal transformer is rated to deliver 421 kVA at 220 V (rms) to a customer, as shown in the figure. If the customer's power factor is 0.9 lagging, what is the maximum usable power the customer can receive? Question 7 An ideal transformer is rated to deliver 438 kVA at 220 V (rms) to a customer, as shown in the figure. If the customer requires 341 kW to operate, what is the minimum power factor with the given size transformer?

Question 1 For the circuit shown in the figure, assume that V = 67 20 Vrms, Rg = 2 , N = 5, and R₁ = 16. Assume an ideal transformer. Find the amplitude of equivalent load resistance seen by the voltage source. Round off your answer to two decimal places. Note: Z = a + jb then the amplitude of Z is √a² +6² Question 2 For the circuit shown in the figure, assume that V = 68 20 V rms, Rg = 22, N = 5, and R₁ = 19. Assume an ideal transformer. Find the power Psource (KW) supplied by the voltage source. Round off your answer to two decimal places and provide your answer in Kilowatts. Question 3 For the circuit shown in the figure, assume that V₂ = 63 20 V rms, R = 12, N= 3, and Ro = 172. Assume an ideal transformer. Find the power Pload (kW) consumed by Ro Round off your answer to two decimal places and provide your answer in Kilowatts.