engleski

Detection of inter-coil short circuits in wind generator windings

This paper presents two new methods of inter-coil short circuits detection in synchronous generator armature and excitation windings, based on the analysis of the machine magnetic field in the generator. Methods are applicable for the machines that have windings with coils, what is the case in most wind generators. The basis for the short circuit detection is a good model of the influence that short circuit has on the air gap magnetic field. Such a model was derived by applying FEM (finite element method) to the generator model. By this approach magnetic field wave forms in the machine have been calculated for every point of interest, under correct and faulty conditions. The points of interest were chosen at spots that are accessible for measurement on an actual machine. The derived model was validated by comparison with the measurements taken on real machines in correct and faulty condition. The generator model in the correct conditions was proven correct by comparison with measurements taken on a real 1MW wind generator. The faulty generator model was validated by comparison with the measurements on a real 16 kVA generator. This generator was altered for this testing in a way that it was possible to short-circuit one or more coil turns of the armature phase winding and the excitation coil windings of one rotor pole. The results obtained by numerical analysis (that was confirmed by real life measurements) offered a valuable insight into generator's physics. This knowledge was used to derive models of how particular generator condition manifests itself through measurable variables. The numerical results were also used as a guideline in choosing proper sensors and variables processing methods. In this way two methods for inter-coil short circuit detection were developed and implemented as fault detection systems.

synchronous generator; magnetic field; flux density; measuring coil; Hall sensor; and generator diagnostics

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