Question

b) An 80MVA, 11kV synchronous generator with a sub transient reactance j0.125pu is connected to each of three busbars labelled A, B and C in Figure 2. Three equal current limiting reactors (100MVA, 11kV) feeders. The main busbars supply secondary busbars (E, F and G) through a line of reactance j2.7 and 100MVA, 11kV/33kV j0.06pu transformers at both ends connected in series with the are Busbar D is connected at the 33kV side of the transformer at G to facilitate the connection of distributed generation. A 5MVA, 6.6kV biomass generator with a sub transient reactance j0.02pu is introduced on the network It is connected through a 10MVA, 6.6kV/33kV j0.05pu transformer and a line of reactance j0.12 to busbar D Draw the equivalent circuit in pu, assuming a base of 100MVA i) (8 marks) ) Detemine the minimum value (in pu) of current limiting reactors required to limit the current for a symmetrical fault at D to 2.0pu when the biomass generator is disconnected (6 marks) i) Calculate the symmetrical fault current at D when the biomass generator is connected. Consider the same value of current limiting reactor obtained in () (5 marks) B G F Figure 2

Answer 1

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