Simulation Study On The Effect Of Internal Electric Field Distribution Of Transformer Insulation On Dielectric Response

As the real beginning of the21st century, normal operation of the electrical equipment force the manager to pay more attention on maintenance of the critical equipment as high-voltage transformers, because of the explosive development of the power system and railway system, where a large number of electrical equipment has been settled down. The main task of the operating departments is c conventional control, maintenance and condition assessment of the equipment. With improvement of detection technology and the detailed investigation of cross-disciplinary, the detection method of insulation state which is valuable for research the insulation assessment of transformers combined ordinary off-line detection and on-line monitoring.The dielectric spectroscopy method based on the dielectric frequency response is a kind of nondestructive off-line test. The application of this method is still in the initial stage in China, and the measurement device of dielectric frequency response for transformer insulation state test is under research. Capturing the signal of dielectric spectrum of insulation system is the core of evaluation method, which could give an accurate condition assessment of the insulation.In this contribution, the finite element analysis model is established by a oil-immersed three-phases transformer size parameters which rated voltage is220kV/35kV and rated capacity is120MVA. The model account for two cases including A, B phase is well insulated and containing insulating defects and the influence of the inner electric field for the dielectric spectroscopy. The paper studied the frequency response curve of reference point in phase insulation by simulation in rated power-frequency condition, simulating the electric field intensity, the electric displacement current density in the A-phase low voltage winding which is well isolated and the condition of with defects.Learned by comparing the electric field intensity, the electric displacement, and current density frequency response curve to the curve of reference point that the electric field strength increasing with the real part of the complex capacitance spectrum curve decrease, the imaginary part of the frequency spectrum amplitude and dielectric loss increase. By analyzing two cases which concluded that inner relationship of the dielectric response and electric field distribution of the high voltage winding A, B phase insulation. The electric field intensity, electric displacement and current density frequency response curve of reference point was simulated, and the spectrum of complex capacitance and the loss factor can be obtained we compared the loss factor of dielectric spectrum. we contain the amplitude of the spectrum curve of the loss factor with defects is greater than the good one.In summary, when the insulation of transformer is performance degradation, the polarization effect of oil paper will be stronger which Lead to increase of the distribution of electric field strength amplitude. Thus, it is positive that the impact on the complex capacitance dielectric response spectrum curve by measured. In turn, it is also proved corresponding relations between them that the frequency domain dielectric response method of dielectric spectroscopy can be a reliable assessment of transformer insulation state.