Research On Large Size Rogowski Coil Current Sensor For Online Monitoring Of Transformer Winding Deformation

At present,One of the most important problems in online monitoring of transformer winding deformation is how to inject an excitation signal into online transformer and measure the response signal.In recent years,it has been feasible to solve this problem using large-diameter current sensors through the way of electromagnetic coupling.However,the problem of electromagnetic shielding failure of the current sensor has a great impact on it in the field test.In this paper,the electromagnetic shielding problem of current sensor in online monitoring of winding deformation is studied.Firstly,the effect of the shielding shell of the current sensor is simulated and analyzed based on the finite element simulation software Comsol Multiphysics,and verify the simulation results through experiments.Then simulate the influence of external interference signals on different sensors,the causes of the current sensor shielding failure applied in the online monitoring of winding deformation are analyzed.Finally,the feasibility of using current sensor to measure transformer bushing current is simulated,and the experiment is carried out on the true transformer bushing to verify the simulation results.The research results show that the shielding effectiveness of the shielding shell to the external interference signal decreases as the main air gap of current sensor shielding increases,and it presents a linear relationship,The range of the scale factor k is obtained by curve fitting.Shielded shells have different shielding effectiveness for external interference signals in different directions,the main air gap of Shielded shell is closer to the direction of the magnetic field and the shielding effect is better.The shielding effect of the ferromagnetic shielding shell is lower than that of the non-ferromagnetic shell under low frequency,and the shielding effectiveness is similar for interference signals above the frequency of 1kHz.In the application of the current sensor in the deformation of the winding,the excitation sensor will generate a leakage magnetic field around it,the measurement sensor will be affected,This phenomenon is more obvious when the sensor has a gap.Excitation sensor's leakage magnetic field acts on the measuring sensor in a circular shape,so its influence is difficult to eliminate.The riser and flange of the transformer bushing do not affect the magnetic field generated by the current flowing through the bushing,which verifies the feasibility of using the current sensor to measure the current flowing through.transformer bushing...