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Background. Timely diagnostics of synchronous generator (SG) performance reduces the damage to power plants from their failures. Electromagnetic processes in the elements of SG create external electromagnetic fields (EEMF) of SG. Therefore, damage to the SG will cause a change in EEMF. There are systems for registering EEMF of SG, their changes, but there are no mathematical models simulating EEMF changes when SG elements are damaged. The aim of the work is to find mathematically grounded interrelationships between SG defects and EEMF changes. Materials and methods. The finite element method is used. Model analysis of EEMF of 538 kW SG is done for idle mode, active, inductive and capacitive loads with defects in the field winding, armature winding, taking into account the damping action of the case at a synchronous rotor speed. Results. A method has been developed for diagnosing SG defects by analyzing the results of finite-element simulation of EEMF and their changes. The greatest change in EEMF when the field winding is damaged has been found to occur with active-inductive load: at a 25 % inter-winding fault of the field coil of one pole, the induction over the neighboring poles increases by 90 %; at a 50 % fault by 235,6 %; at a 75% fault – by 416 %. The break of the parallel branch of the armature winding leads to different amplitude EEMF induction distributions over time on the SG case. The measurements of the EEMF of a working healthy SG have confirmed EEMF presence. Defects of SG elements cause changes in EEMF. Damage to the pole field coil leads to an increase in the EEMF induction in the region of other poles. The defect of the armature winding can be detected by the difference between the amplitudes of the EEMF induction distributions over time at different points on the case. A method for diagnosing damage to the elements of SG by measuring changes in EEMF has been proposed. Conclusions. The proposed method of synchronous generator defect diagnostics allows determining the types and degree of synchronous generator stator and armature winding damage by changes in the external electromagnetic field.

Method for diagnostics of synchronous generator defects by changes of external electromagnetic field