Design Of In-situ Test System For Thermal Conductivity Of Solid Insulation Under Electric Field

The thermal conductivity of solid insulation materials has always been a research hotspot in electrical engineering and related disciplines.The thermal conductivity of solid insulation materials under electric field is usually described by the thermal conductivity measured in conventional environment.It is not clear whether the electric field has an effect on the thermal conductivity of solid insulation materials.At present,there is no perfect and reliable in-situ test system for thermal conductivity of solid insulation materials under electric field.Aiming at the problems existing in the in-situ test system of thermal conductivity of solid insulating materials under electric field proposed by the previous research of the research group,this thesis improves the structure of the electrode system,and uses the non-contact temperature sensor to obtain the cold surface temperature of the sample,so as to avoid the influence of contact temperature measurement on the conductivity current test of the sample.The feasibility of the test principle is verified by simulation,and a new in-situ test system for thermal conductivity of solid insulating materials under electric field is designed.The internal heating of the material under the electrothermal coupling field is simulated and analyzed.The results show that the Joule heat density of the cold surface is large,and the heating problem of the cold surface is more serious than that of the hot surface.The electric field will reduce the temperature difference between the cold and hot surfaces,and the temperature difference decreases with the increase of the material conductivity.The hardware part uses high thermal conductivity brass to make electrode physical module.The isolation transformer is designed by using the geometric constant method of magnetic core,and its insulation performance is verified by voltage test.The fuzzy PID algorithm was used to realize the temperature tracking outside the main heating electrode and inside the auxiliary heating electrode.The temperature measurement in different areas of the contact surface between the highvoltage electrode and the sample showed that the temperature of the contact surface was uniform,the temperature consistency was high on both sides of the contact surface,the radial heat shielding effect of the auxiliary heating electrode was good,and the axial symmetrical one-dimensional heat transfer effect of the high-voltage electrode met the design requirements.In terms of data acquisition,based on SPI protocol,STM32 single-chip microcomputer is used to realize 14-channel hot surface temperature data acquisition on the high-voltage side;the cold surface temperature of the low pressure side sample was obtained by infrared thermometer.The conductivity current of the sample was collected by an electrostatic meter.The Bluetooth module is used to transmit the hot surface temperature data wirelessly,and the cold surface temperature data is transmitted directly to the computer through the serial port.The weighted residual method is used to identify the bad temperature data,and the Kalman filter serial and parallel multi-channel temperature data fusion algorithm is written to obtain the thermal surface fusion temperature and calculate the thermal conductivity of the sample.An in-situ test system for thermal conductivity of solid insulating materials under electric field was built.The system was used to measure the thermal conductivity of LDPE and PI films in conventional environment and electric field.After correction by the axial heating power correction model,the test results of the two in conventional environment were consistent with the change trend of the 3ωmethod test results,and the test results of the two in electric field were the same as the thermal conductivity test results in conventional environment.