Design And Experimental Study Of Internal Pressure Monitoring Sensing Device For Power Transformer Based On Multi-wall Carbon Nanotubes

Under the background of achieving carbon peak and carbon neutrality,the continuous development of industrial electrification and the increasing demand for electricity have gradually increased the operating pressure of power networks.The normal operation of electrical equipment in power network is the premise to ensure the quality of high-level power supply.As a key equipment for voltage level conversion,the importance of power transformer is self-evident.Oil-immersed power transformers are widely used in distribution networks due to their good overload capacity and low manufacturing and maintenance costs.With the increase of load,the operating environment of oil-immersed transformers gradually deteriorates,and the reduction of internal insulation performance leads to frequent partial discharge.Severe partial discharge causes the pressure and oil temperature in the transformer tank to increase sharply,which makes the transformer in danger of explosion and poses a great threat to the safe operation of the power network.Therefore,it is of great practical significance to realize the real-time online monitoring of the internal pressure of the oilimmersed power transformer,and to timely disconnect and warn when the internal pressure of the oil tank exceeds the safety threshold,so as to improve the operation safety of the power network and avoid major social and economic losses.In order to realize the real-time online monitoring of the internal pressure of oilimmersed transformers,this paper proposes a flexible porous pressure sensing material based on polydimethylsiloxane(PDMS),nanofiber(FIBER)and multi-walled carbon nanotubes(MWCNTs)composites.Based on the physical properties of the sensing material,this paper establishes the deformation model of the pressure sensitive film with different shapes under the same stress condition,and obtains the sensing design shape that can make the pressure sensing material have the best mechanical response,which lays a theoretical foundation for the design and manufacture of flexible pressure sensors.According to the study of the optimal mechanical response model of PDMS/FIBER@MWCNTs pressure sensing material and the exploration of the physical and chemical properties of materials such as nanofibers(FIBER)and multi-walled carbon nanotubes(MWCNTs),the fabrication and packaging process of PDMS/FIBER@MWCNTs pressure sensing material was obtained.A flexible porous pressure sensor with high sensitivity,wide strain range and good stability was prepared,which can meet the timely and effective monitoring of the internal pressure surge in the transformer tank.Finally,in order to verify the actual performance of PDMS/FIBER@MWCNTs pressure sensor,an oil-immersed transformer pressure test platform and a pressure online monitoring system were designed and built.By designing the resistance signal acquisition circuit of the pressure sensor,the resistance value collected in real time is corresponding to the actual pressure value in the pressure monitoring system.Finally,through the joint test of the test platform and the pressure online monitoring system,during the test,the pressure sensor can accurately reflect the pressure change inside the fuel tank in real time,and trigger the pressure alarm prompt in time when the internal pressure exceeds the set threshold.On the test surface,the pressure sensor designed and fabricated based on PDMS/FIBER@MWCNTs pressure sensitive material can accurately and effectively monitor the pressure surge caused by oil-immersed power transformers during sudden faults,and realize real-time monitoring of the internal pressure of the oil tank.