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Determination of Synchronous Generator Armature Leakage Reactance Based on Air Gap Flux Density Signal

A new procedure for the armature leakage reactance of the synchronous generator determination is proposed. The procedure is based on measurement of the phase displacement between the fundamental harmonics of the armature voltage and the generator air gap flux density. The accuracy of the algorithm for the phase displacement determination, which is based on Discrete Fourier Transform (DFT), is proved by the laboratory measurement first. After that, measurements on the synchronous generator in HEPP Peruća on Cetina River in Croatia are performed. Two sensors are used for the air gap flux density measurement: the Hall sensor and the measuring coil. To prove the proposed procedure, on the same generator the applied voltage test with rotor removed is performed, too. It is proved that a measuring coil can not be used as the flux density sensor because of the system error due to the air gap field harmonics. On the other hand, when the Hall sensor is used one should pay attention to the voltage noise due to the armature reaction fundamental harmonic. This voltage noise can be minimized by performing measurement at a particular operating point of the generator. The theoretical criterion for determination of this particular operating point is defined in this paper.

synchronous generator; armature leakage reactance; on-line parameter identification

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