Investigation On Joint Measurement Device Of Space Charge And Conduction Current In Polymer

The HVDC cable is the physical basis and core equipment for the construction of DC power grid.The accumulation and migration of space charge in polyethylene insulation under DC high field is the key technical problem that restricts its direct application to VSC-HVDC cables.It is important to study the space charge distribution,the conduction current characteristics and their correlation in polymer for revealing the formation mechanism of space charge and the design of DC cable insulation.Based on the theory of Pulsed Electro-acoustic(PEA)space charge measurement,this paper has designed the hardware and software of the combined measurement device for space charge and conductance current.The hardware design of the device mainly includes the design of high voltage nanosecond pulse power with a pulse width of 10 ns and an amplitude of 1 kV through the debugging of the transmission line and matching impedance,the design of measuring electrodes with shielding by using SolidWorks software,the design of signal acquisition and processing module by selecting the PVDF piezoelectric sensor with thickness of 28 ?m and the amplifier with gain of 63 dB,and the design of Joint measurement of conductance current and space charge through solving the grounding problem when inserting 6485 electrometer into electrodes.The software design of the device mainly includes the compiling the program block diagram of the joint measurement device based on LabVIEW,realizing the functions of real-time acquisition,display and storage,analysis and processing of the measurement data.This paper has focused on the algorithm implementation of waveform recovery based on deconvolution,data processing in front and back period of waveform recovery and dimension correction.This paper finally has measured and analyzed the polyethylene nanocomposite insulation material by using the device.The validity of the measuring device has been verified,and the influence of different parameter settings on the measuring results also has been studied.The research has showed that the joint measurement device of space charge and conduction current can measure the space charge distribution and conduction current characteristics of polymer insulating material simultaneously and accurately.This paper has obtained that the spatial resolution of measurement device is about 35 ?m and the measurement accuracy of space charge is about 0.1 C/m3 through data measurement and analysis of 0.5%LDPE/BN with a thickness of about 200 ?m.In addition,we can get the electric field distribution and potential of distribution the insulating material through data analysis and postprocessing of space charge.