Standard Deviation Of Conductivity Research Articles

An Optimization Algorithm H-GVSPM for Electrical Impedance Tomography

Electrical impedance tomography (EIT) is a novel industrial monitoring technology with the characteristics of safety, inexpensiveness, and real-time monitoring. Its imaging results are easily to generate artifacts due to the influence of various factors. Therefore, the image quality is low, and the contour of measured objects has a distortion phenomenon. An optimization algorithm H-GVSPM based on the Hadamard product is proposed for EIT to reduce the artifacts, and to improve the image quality. The relative conductivity difference between the measured object and the background becomes more distinguishable with the action of the Hadamard product. Simulation and experimental results show that H-GVSPM effectively reduces the influence of artifacts in the reconstructed images. The maximum increase of the correlation coefficient approximately is 15.56% and 22.80% respectively compared with GVSPM and TV method. The maximum reduction of the voltage relative residual is 22.12% in the simulation, and it is 8.12% in the experiment. The standard deviation of conductivity is about 1/10 of the original. This study provides a reference method for improving image quality, and it contributes to the application of EIT in industry, biomedicine, and other fields in the future.

Electric field distribution based on radial nonuniform conductivity in HVDC XLPE cable insulation

The steady-state electric field distribution in a polymeric insulated HVDC cable is determined by the electrical conductivity, which is dependent upon the temperature and electric field in homogeneous cable insulation. In practice, the radial inhomogeneity of the morphological structure and crosslinking byproducts in XLPE insulation will lead to a radial nonuniformity of the conductivity, which may further result in the change of electric field distribution in the insulation. In this paper, the conductivity distribution characteristics in XLPE insulation of HVDC cable are investigated at various temperatures and electric stresses. It is found that the difference of conductivity across the insulation is from several times to two orders in magnitude at given temperature and electric stress. Besides, the standard deviation of conductivity indicates that the difference in magnitude is generally larger at lower temperature. Then, the electric field distribution is analyzed at operating and at test voltages with or without load based on above results. A nonuniformity coefficient C E is introduced to characterize the degree of deviation of the actual electric field distribution from the mean electric stress; a distortion rate δ E characterizes the difference of the field distribution based on the radial nonuniform conductivity from the uniform conductivity. It shows that C E and δ E are larger at no load than at full load. Under zero load at 1.85 U 0 , C E and δ E can reach 2.26 and 92.25 %, respectively. The results show that the radial nonuniform conductivity has a significant impact on the electric field distribution in the application of HVDC XLPE cable especially with thick insulation. The effect of conductivity with radial nonuniformity on the modification of field distribution should be considered in the development and the qualification tests for HVDC cables.

Investigation of the dielectric response of binary disordered systems modelled as random resistor–capacitor networks

In this paper, we investigate the dielectric response of binary disordered systems, which are widely modelled by random resistor–capacitor networks (RRCN). Our results show the existence of a scaling law connecting the standard deviation of conductivity to the network size and capacitors proportion. In addition, we have studied the effect of using lossy capacitors on the dielectric response of RRCN. We found that lossy capacitors may introduce substantial effects of the dielectric loss, especially at low frequencies.