Question

Problem 2 (50 points): The generator in the figure generates and delivers 150 MW to the power system below. At steady state the generator regulates the generating station voltage (bus 1) to pu. The system voltage at bus 3 is 1.05 pu. 1. Compute the internal voltage and rotor angle of the generator under the above conditions. 2. The fault sequence for a solid three-phase fault on any of the line circuits consists of a delayed tripping of both circuit breakers protecting the faulted circuit. The circuit breakers subsequently remain open, which results in a permanent outage of the faulted circuit. The time to clear the fault and open the circuit breakers is 0.25 s. Apply the equal area criterion to determine the transient stability of the system for a solid three-phase fault on circuit 1-2a near bus 1. Use the same criterion to determine the critical clearing time of the fault in question 2. 3. (infinite bus) G1 T1 13.8 kV 345 kV Data: G1: 200 MVA, 13.8 kv Yg, 60 Hz, 4 poles, X-0.25 pu, H-3.5s. TI: 200 MVA, l 3.8Yg-345 kV, 60 Hz, X-0.15 pu. TL (all segments are identical). Each segment: X- 150 2. Problem 3 (20 points): In a 138 kV distribution substation, MOV lightning arresters are used at the substation entry. The operating voltage of the arrester for impulse waves is 150 kV. The distance between the arrester and the bushings (terminals) of the substation transformer is 3 m The surge impedance of the incoming power line is 250 Ohms. Apply the lattice diagram technique to compute the crest of the voltage across the transformer, if a 5-kA 8/20-us impulse enters the substation. Assume that the travel time of waves of the line is the same as the speed of light in vacuum. (For this problem show the lattice diagram for a few reflections.)

Answer 1

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