Space Charge Measurement System Based On LIPP

In the external electric field,space charge will be produced within the medium.In today’s DC electric field,as a common polymer insulation material,the accumulation of space charge in insulating materials has been the focus of research.Because the accumulation of space charge affects the insulation performance of the material,including breakdown performance.And the defects and traps existed in the insulation materials,under the influence of the DC electric field,the insulation polymer will lead to the accumulation of charge in the polymer material,resulting in the increase of local field strength and damage the insulation performance.Moreover,the injection,transmission and dissipation of the space charge in the insulating material can destroy the material and even lead to a decrease in the service life of the insulating material.Based on the laser induced pressure wave method(LIPP)method,the measurement signal is strong,the signal-to-noise ratio is high,and the measurement is not limited by temperature.Therefore,this thesis is based on the important premise of space charge research.The research work carried out in this thesisas follows:LIPP space charge measurement system has been set up and the spatial resolution of the measurement system has been studied.According to the principle of LIPP,a space charge measurement system for insulation materials is designed and fabricated,which includes sample room,electrode system,protection circuit,signal acquisition unit,signal recovery software and so on.Metallic aluminium and Semiconductive material are chosen as target materials,The influence of the thickness of aluminum plate on the experiment was studied,and the aluminum target and semi conducting target were compared.The experimental results show that the aluminum plate as the target material prolongs the service life of the target material and improves the resolution of the system.The experimental results show that the aluminum plate as the target material prolongs the service life of the target material and improves the resolution of the system.Finally,the measurement results of LIPP method are compared with those measured by pulsed electro-acoustic(PEA)method.In this thesis,we have studied the spatial resolution of 1.2mm LDPE plates by using LIPP system.The experimental results show that the signal reflection can be eliminated if there is a minimum thickness aluminum target in the sample.It is also revealed that the aluminum thickness determines the spatial resolution.