Max Fault Current -Generator

Max Fault Level of Generator

Diesel Diesel Generating Generating set comprises comprises of diesel diesel engine as the prime mover. mover. When a short circuit circuit occurs on the system powered by a generator, the generator continues to produce voltage at the generator terminals as the field excitation is maintained and the prime mover drives the generator at normal speed. The generated voltage causes a large magnitude fault current flow from the generator to the short circuit. The flow of fault current is limited only by the generator  impedance and the impedance of circuit between the generator and short circuit. In case of a short circuit at the generator terminals, the fault current is limited by generator impedance only

Objective – To calculate the fault current of the generator

Generator Rating – 2000KVA Rated Voltage -415V Sub Transient Reactance Reactance Xd “ - 0.11 ( Reference Technical Data Sheet of Alternator Alternator ) Fault Current If = Fault MVA MVA / √3 x kV Fault MVA = MVA / Xd” Fault MVA = 2/0.11 = 18.1818 Fault Current = 18.1818/ √3 x 0.415 = 25.295 kA Full Load Current of the Generator = MVA / √3 x kV =2.782kA or 2782 A This means that the fault fault current is (25.295/2782 ) times times i.e approximately 9times 9times the full load current .