Implementation Of CMTL Model For Transformer Winding Deformation Diagnosis Based On FRA

Radial deformation is a common type of power transformer failure in recent years,which requires a timely and accurate diagnosis to avoid causing transformer insulation breakdown accidents.Frequency response analysis is the most common and sensitive method for winding deformation detection.It is used to diagnosis whether the winding is deformed by extracting the change of winding frequency response curve caused by the change of distributed capacitance and distributed inductance after winding deformation.However,at present,there is a lack of correspondence between the degree of change of the frequency response curve and the mechanical deformation of the winding,which makes it difficult to give a clear amount of mechanical deformation of the winding when the frequency response method diagnoses the winding deformation.In this paper,multi-conductor transmission line theory(MTL)and Maxwell electromagnetic field simulation software are used to simulate the frequency response curve of a 110kV winding for the actual winding structure of a 220/110/35kV power transformer.The frequency response deviation of the different deformation of the winding is studied.Firstly,the difference between the frequency response curves established by MTL and the circular coordinate multi-conductor transmission line theory(CMTL)is compared and analyzed.It is pointed out that the difference between CMTL and MTL is higher in the high-frequency band and the CMTL effect is better.Secondly,the normal winding is obtained through simulation and the frequency response curve of the deformed winding with buckling radius.The correlation coefficient,resonance frequency-based amplitude deviation index and frequency deviation index,Chinese standard relative factor,unit amplitude deviation index(AD)of the frequency response curve are extracted and comparative diagnosis sensitivity is analyzed.The relation between the degree of deformation of the windings indicates that the sensitivity of AD is higher,and the more sensitive new diagnostic index of the sum of absolute deviations(SAD)and its corresponding relationship with the degree of deformation of the windings are further proposed.