The Study On Transformer Winding Fault Determination Based On Lightning Impulse And Damping Oscillation

Power transformer is one of the most important and essential core equipment,of which safe and stable operation has significant effects on the reliability and safety of power system.The transformer diagnose on the field requires high quality equipment and the test time by using current method is too long.Common lightning impulse test rely on the experiment of testers to diagnosis fault while common damping oscillation test results can only be used to detect winding partial discharge.As to these,based on the transfer function method of which excitation is lightning impulse and damping oscillation for transformer winding fault determination is presented in this paper.The main contents are as follows:?1?Based on a 10 kVA,2.4 kV/0.22 kV,50 Hz,single-phase tapped transformer,a test platform for the fault determination of transformer windings is established to simulate winding short circuit faults.The result of transformer winding using lightning impulse,damping oscillation and SFRA method are compared.Also the statistical indicators for transfer functions for three method are compared.?2?To extend the result to three-phases transformer,based on a 400 kVA,10 kV/0.4 kV,50 Hz,Y_ny_n0,ONAN,three-phases reduced-scale transformer,a test platform for the fault diagnosis of transformer windings is established to simulate winding short circuit faults.The voltage responses of lightning impulse and damping oscillation under winding different position and different layer winding short-circuit fault are measured,and voltage transfer functions are calculated.The fault determination results of three-phases transformer and single-phase transformer under lightning impulse are compared.?3?Based on the three-phases transformer test platform,winding deformation fault under lightning impulse and damping oscillation are simulated.The voltage responses of lightning impulse and damping oscillation under winding deformation are measured.The fault determination results are compared.Also the transfer functions between high voltage to high voltage and high voltage and low voltage are compared to analyze the differences of these transfer functions detecting winding short-circuit and deformation fault.To be concluded:the result of single-phase transformer winding short circuit fault under lightning impulse and damping oscillation is similar to the result under SFRA method.The sensitivities of both impulses are similar to SFRA for detecting winding–ground and winding–interlayer short circuits faults.In the experiments of three-phases transformer,the lightning impulse and the damping oscillation can detect winding short-circuit faults.The damping oscillation can detect winding short circuit fault better while the lightning impulse can detect winding deformation fault better.The result of winding short circuit fault under damping oscillation show negative correlation of the transfer function of normal phases at high voltage side and of same phases under normal condition.That can help to locate the fault and evaluate the severity immediately when winding short circuit fault occurs.The transfer function between high voltage phases can detect winding short circuit fault better while the transfer function between high and low voltage phases can detect winding deformation fault better.