Impact of Directly-Connected Generator Design on Balanced Fault Behaviour

J.D.F. McDonald and T.K. Saha (Australia)


Power system faults, Short circuitcurrents, Overvoltages, PowerformerTM, Power systems planning.


This paper considers the impact that the design of a directly connected generator will have upon the behaviour of an entire power system under the influence of a balanced three-phase bolted (LLLG) fault. Initially a method for illustrating the effect of the connection of a single generator upon the entire network is demonstrated. This is utilized to derive algebraic comparisons between the fault currents, voltage disturbances and the generator fault in-feeds that are produced in a power system in which an existing generator and GSU (generator step-up) transformer is replaced by a directly connected generator. The qualitative relationships are verified with data obtained from simulation of a 17-bus test system and a 600-bus realistic power transmission network. The results highlight that the variation in design of a single generator may produce perceptible change to network fault behaviour in an appreciable portion of a power system.

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