Influence Of Short Circuit Factors On Winding Load Under Air-gap Eccentricity And Stator Short Circuit Composite Faults

Air-gap eccentricity and stator inter-turn short circuit(SISC)are common faults of generator,which have an important impact on the normal operation of generators.The purpose of this paper is to study the effect of two kinds of short-circuit factors,such as short-circuit degrees and short-circuit positions,on the load of winding when static air-gap eccentricity(SAE)and the SISC occurs.Analytical derivation,computer simulation and dynamic test on generator are three main research methods of the paper.Firstly,theoretical derivation is carried out to obtain the relationship between short-circuit and the air-gap permeance and magnetic motive force.On the basis of this,the law of Ohm and electromagnetic induction are applied to obtain the expression of electromagnetic force of winding,and the influence of corresponding short-circuit factors on electromagnetic force is obtained.The variation of the frequency component and amplitude of the electromagnetic force under different faults is qualitatively analyzed.Secondly,the three-dimensional finite element simulation models of MJF-30-6 generator with SAE and SISC composit fault(CF)are established in Ansoft-AnsysWorkbench platform to obtain the electromagnetic force and mechanical response data of stator winding under different short-circuit degrees and different short-circuit positions.The influence of short-circuit degrees and short-circuit positions on the electromagnetic force and mechanical response of winding is quantitatively analyzed.The MJF-30-6 generator is tested to acquire vibration response data under different short-circuit degrees and different short-circuit positions,which verifies electromagnetic force characteristics obtained from the analytical derivation and the computer simulation.The anslysis shows that the DC and even harmonic amplitudes of electromagnetic force of short circuit winding increase sharply under SAE and SISC composit fault as well as the characteristics and response of electromagnetic force are related to the short circuit degree and relative positon.For the SISC degrees,SISC increase amplitudes of the DC and even harmonic and peak values of total deformation,elastic train and stress.For the relative fault location,due to the smaller circumferential angle between the SISC winding situation and the minimum air-gap location,amplitudes of the DC and even harmonic and peak values of total deformation,elastic train and stress are increased.Moreover,the windings with SISC are most likely to be damaged under composite fault.And the nose-top,middle of the involute part and the joint part of the end winding and the line winding are the most dangerous places.The research results in this paper reveal the corresponding relationship between electromagnetic force and its vibration response of the stator winding and the composing factorc under faults,laying a foundation for the improvement of the preventive insulation manufacturing process of generator windings in actual production,and the monitoring and diagnosis of air gap static eccentricity and stator short circuit composite fault during operation.