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Unformatted text preview: Power Systems I Fault Analysis l Analysis types u power flow  evaluate normal operating conditions u fault analysis  evaluate abnormal operating conditions l Fault types: u balanced faults n threephase u unbalanced faults n singleline to ground and doubleline to ground n linetoline faults l Results used for: u specifying ratings for circuit breakers and fuses u protective relay settings u specifying the impedance of transformers and generators Power Systems I Fault Analysis l Magnitude of fault currents depend on: u the impedance of the network u the internal impedances of the generators u the resistance of the fault (arc resistance) l Network impedances are governed by u transmission line impedances u transformer connections and impedances u grounding connections and resistances l Generator behavior is divided into three periods u subtransient period, lasting for the first few cycles u transient period, covering a relatively longer time u steady state period Power Systems I Fault Studies l Subtransient period, X G = X d " u determine the interrupting capacity of HV circuit breakers u determine the operation timing of the protective relay system for highvoltage networks l Transient period, X G = X d ’ u determine the interrupting capacity of MV circuit breakers u determine the operation timing of the protective relay system for mediumvoltage networks u transient stability studies Power Systems I Fault Representation l A fault represents a structural network change u equivalent to the addition of an impedance at the place of the fault u if the fault impedance is zero, the fault is referred to as a bolted fault or solid fault l First order method u the faulted network can be solved conveniently by...
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 Spring '11
 THOMASBALDWIN
 Electrical Engineering, Trigraph, Electrical resistance

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