Question

Figure 1 Single line diagram b2 b3 b1 b4 grid Τι 13 A power system single line diagram is shown in Figure 1. The single line diagram shows a synchronous generator G connected to a large 50 Hz grid via its unit transformer T and a network of three transmission lines. Relevant details of the grid, transformer, generator and overhead lines are provided in Tables I,II,II & IV respectively. A double line to ground fault occurs at bus 3 Questions. (a) Draw and label the full sequence networks interconnected for a DLG fault at bus 3. b) Find the fault phase currents in p.u (c) Find the fault phase current contribution in p.u. from the grid as measured at bus 1 (d) Find the fault phase current contribution from the generator as measured at bus 4. 131 (e) Find the post fault phase voltages in p.u. at bus 1 (f) Find the post fault phase voltage in p.u. at bus 4 Work in p.u. throughout using the transformer rating as the common power base Assume prefault internal voltages of the generator and the grid equivalent are 1 p.u at zero phase angle. Write a short report showing details of the calculation method, sequence network diagrams and incorporating answers to the above questions together with comments on your results by the deadline of Thursday 2nd May 12 noon to the school office (room 236). The report should be signed to indicate it is your own work and may be hand written provided it is clearly legible. System data TableI Grid lUI kv400 IS"kI MVA 5000 Table II Trafo T Table III Generator G ul kv 20 IS,I MVA 500 UHI kV 400 2 X/R infinite IS,I MVA 500 IUvI kV 20 x1 % 专% x,96 connection XN Ohms 15 12 10 YN_? ukr &ukro % 10 Vector group YNd1 2 TL12 TL13 TL23 Table IV Transmission lines lUn] kv x1 ohms/km Xo ohms/km length 0.01 400 0.4 1.2 60 400 0.40.4 1.2 400 2 1.2 100 80

Answer 1

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! (levo) (2elu广 Transmi ssien Lins SOD leve) TL 13 po = 0.0014- In

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218 73 Sev づ set

EPI Rake 2 2- + IR

c) Frem Zec Seyrnca that No Cuss Contributedy enctd