Measurement Technology Of Response Characteristics For Non-linear Insulating Dielectrics Under Lower Frequency Voltage

Non-linear dielectrics are those materials, for which the electric conductivity or/and relative dielectric constant is a function of electric field. Taking the study of lower frequency response characteristic for non-linear composite dielectrics as background, some problems about the measurement method of non-linear dielectrics under lower frequency exciting voltage and the design of the measurement system are discussed, and a measurement system based on the virtual instrument technology is developed.At first, a non-linear AC equivalent circuit model with voltage-controlled resistance and capacitance connected in parallel is built up for common non-linear dielectrics, to deduce the response current function of the exciting voltage. For the hardware part of the response current measurement system for non-linear dielectrics under lower frequency voltage, the AC excitation voltage source system is designed by assembling a programmable signal generator and linear HV amplifier modeled as Trek20/20C. Afterwards, electron tube typed as DC-2 and integrated operation amplifier named as ZF310K are separately used to design micro-current amplifiers. By contrast and analysis between the two micro-current amplifiers, it is find out that the capability of micro-current amplifier based on ZF310K is better than that based on DC-2. And then, the main measuring circuit and the PC+DAQ type signal acquisition system are also designed. In the software of the measurement system, a software combined functions of signal generate, synchronous signal acquisition, register, filtering, signal shape generate is developed based on the LabVIEW platform. The measurement system is developed through combining the hardware and software. And the measurement system developed in this paper can be used for the response characteristic measurement of non-linear dielectrics under the excitation voltages with trapezoidal wave, triangle wave, sine wave. Finally, proving trials and real measurement are completed for the whole measuring system.Experimental results illustrate that the measuring system meets the needs of lower frequency exciting voltage response current characteristic measurement for non-linear dielectrics. At the same time, the response current measurements of LLDPE/SiC composite and the plate of controlling electric field stress under the excitement of trapezoidal wave are carried out using this measurement system, and the results are discussed.