Analysis Of Generator Stator End Short-circuit Faults Based On Ansoft

Generator is one of the most critical electrical equipments in power system, and its stable operation plays an important role in the safe operation of the entire power grid. When the stator end winding occurs short-circuit fault, the stator currents will reach large values and cause overheating of the damp bars, thus endanger the safety of the generator. Therefore, the study of generator running under stator end short-circuit fault has theoretical and practical value.First, this paper qualitatively analyzed the synchronous generator short-circuit fault. Based on the theory of synchronous generator, stator and rotor currents after short-circuit fault were derived, the changes of currents under different short-circuit faults were discussed. Meanwhile, generator running under single-phase to ground fault, two-phase short circuit fault and three-phase short circuit fault operations were calculated respectively.Then, based on electromagnetic field theory, the electromagnetic field boundary value problem of hydro generator was given, the problem took the magnetic vector potential A as variable and considered all types of boundary conditions. With triangular element mesh and linear interpolation, this paper used Galerkin method to establish the finite element discretization equations. For the problem of electromagnetic movement, this paper derived interface conditions which the static field and rotated field should meet, and proposed the combination method of time step and space step to solve the motion problem. All of the above provided theoretical foundation for the application of time-step element method.Finally, a field-circuit-motion directly coupled time-stepping finite-element analysis model was established, thought the model of a 225 MW hydro-generator running under short-circuit fault operation was calculated. By changing external stator circuits, all the short circuit calculations of hydro-generator stator can be implemented. According to the calculation model of damper bars'current and loss, the current waveform and the loss distribution under different stator faults were obtained. It was found that under asymmetric stator faults the losses of damper bars are larger and the damper bar with the largest losses is close to the leeward side.The research results above are expected to supply the important basic theories and methods to realize generator stator end short-circuit faults forecast and real-time diagnosis.