Research On Vibration And Noise Characteristics And Shielding Measures Of 500kV Autotransformer Under DC Bias

As the key equipment of the power grid,the safe and reliable operation of the transformer is directly related to the normal operation of the entire power grid.However,in actual operation,it is possible that the geomagnetie indueed current generated in the transformer due to the geomagnetic field disturbance,the direct current caused by the potential difference generated by the direct current transmission at dififerent neutral points,and the stray current generated by the subway power supply system are possible.When the transformer is affected by DC bias,the magnetomotive force on the iron core has a DC component,which causes the vibration displacement of the core and winding to increase,the noise increases,the excitation current is distorted,the transformer has local overheating,insulation aging and other problems,and the transformer is damaged.In order to ensure the stable operation of the transformer,it is necessary to study the vibration and noise laws of the iron core and winding under DC bias and the influence on the voltage and current waveforms,and analyze the shielding effect of the transformer after the shielding measures are adopted.In this paper,the autotransformer of model 0DPFS-250000/500 is taken as the research object.A three-dimensional transient coupling simulation model of multiphysics is established for the hazard of DC bias to transformer.The vibration and noise laws of the iron core and the winding and the changes of the voltage and current waveforms under DC bias are studied.The effects of the shielding effect on the vibration noise and the voltage and current waveforms after the capacitive blocking device are analyzed are analyzed.The stable operation of the coupling transformer provides a viable reference.First,the high and medium windings eontain DC components based on DC bias,so the equivalent DC current equivalent to the high voltage side is calculated;Secondly,according to the 500kV autotransformer data provided by the manufacturer,the equivalent parameters of the high,medium and low three winding resistances and reactances are calculated,and the equivalent autotransformer circuit diagram is obtained;Then,using the Comsol simulation software,a three-dimensional transient multiphysics coupling model of the electromagnetic-vibration-sound field of the transformer is built;Finally,the vibration and noise laws of the iron core and winding under DC bias and the influence of voltage and current waveform are obtained.The reduction of vibration displacement on the core and winding and the reduction of transformer noise after the shielding measures of the capacitive blocking device are analyzed.Degree,as well as changes in voltage and current waveforms.Based on this,it provides data support for engineering applications.Research indicates:Under DC bias,the magnetic flux density on the core increases in the positive half cycle,decreases in the negative half cycle,and the core vibration also increases in the positive half cycle and decreases in the negative half cycle;The vibration displacement of the winding increases with the increase of DC,and the growth rate is fast to slow;Core noise is higher than winding noise;As the amount of DC increases,the high-side current waveform shifts upward,the low-voltage side current waveform,the positive half-cycle head shifts to the left,and the negative half-cycle head shifts to the right;After the capacitor is used,the vibration displacement on the iron core and the winding is reduced,and the noise on the transformer is effectively reduced;The current waveform no longer shifts upward,but within 0.005s,a oscillating wave with a magnitude slightly larger than Umax(Imax)is generated.After 0.005,the waveform returns to normal.The above research results have important practical significance for preventing the adverse effects of DC bias on 500kV autotransformers.