Max Fault Current -generator

Max Fault Level of Generator Diesel Generating set comprises of diesel engine as the prime mover. When a short 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 Xd “ - 0.11 ( Reference Technical Data Sheet of Alternator ) Fault Current If = Fault 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 current is (25.295/2782 ) times i.e approximately 9times the full load current .