Simulation of three-phase short-circuit at the terminals of synchronous machine
Three-phase sudden short-circuit at the terminals of a synchronous machine under open circuit condition is simulated. The standard parameters are calculated by using the known parameters, and substituted into the analytical expression for computing short-circuit current. The curve of the relationship between the maximal armature momentary current and the rotor angle is plot. It is concluded that the armature momentary current is maximal when short-circuit occurring at the time of the terminal voltage wave is going through zero. Furthermore, a simulation model in SIMULINK environment is constructed, thus the oscillograms of the armature short-circuit currents in the three phases and the field short-circuit current are plot.
Phase shift of the current under a single-phase short-circuit in the stator winding of a turbogenerator with double winding per phase
An equivalent model of a faulty turbogenerator under a single-phase short-circuit in the stator winding is presented. The model is based on modified voltage–current equations for the positive-sequence component of the short-circuit current that takes into account the mutual spatial displacement of particular part of the faulty stator winding, the rotor magnetic asymmetry and the impact of the resultant reactance value of the unit transformer and the power network. The developed model also represents the effect of the mutual phase shift of the short-circuit current flowing in the relevant sections of the damaged stator winding. The mutual phase shift value of the short-circuit current (periodic component of basic frequency) is found to be dependent on the number of shorted turns in the stator winding. Also found is the influence of the load current value on the displacement angles between currents flowing in the particular part of the faulty stator winding. This phenomenon of phase shift of the short-circuit current could be used as an additional criterion of operation for turbogenerator protection systems.
Ground Fault Protection for Electric Utility Generating Station Medium Voltage Auxiliary Power Systems
Most generating station designs have medium voltage auxiliary power systems with low resistance grounded neutrals.1 In order to provide even higher reliability, the auxiliary power distribution system configurations supply increasingly redundant process equipment.