Study On Relationship Of Breakdown Strength And Electrical Trees Characteristics Of Polyethylen Nanocomposites

Breakdown strength,initiation voltage of electrical tree and growth length are important indicators to characterize the electrical resistance of polymer insulating materials.Electrodendrization in polymer materials is essentially a kind of local damage.It may not cause the breakdown behavior immediately,but the long development of the electric branch will lead to the breakdown of the material,which is a kind of long time breakdown behavior,which is different from the short time breakdown.At present,many studies have been done on the electrical dendritic properties and breakdown characteristics of polyethylene nanocomposites,but there are few studies on the relationship between the breakdown strength and the electrical tree properties of polyethylene nanocomposites.The relationship between the breakdown strength and electrodendrization of low density polyethylene(LDPE)filled with inorganic nanoparticles is of great significance to the electrical resistance of polymer insulating materials.According to the above reasons,in this paper,the distance of needle plate is 2.50 mm ? 2.50 ± 0.01 mm ? 2.50 ± 0.02 mm ? 3.00 mm ? 3.00 ± 0.01 mm ? 3.00 ±0.02 mm ? 4.00 mm ? 4.00 ± 0.01 mm ? 4.00 ± 0.02 mm respectively and several experiments have been carried out in the sample.It is found that the distance of needle plate has a great influence on the initial voltage of electrical tree,and the larger the distance of needle plate,the higher the initial voltage of electrical tree,so as to ensure the accuracy of experimental data.In the whole experiment,the distance of the control needle plate is 2.50±0.01 mm,and the curvature radius of the needle tip is calculated by MATLAB programming.The statistical experimental data show that the curvature radius of the needle should be controlled within 2.35?m,that is,the control precision is between 1 and 2.35?m.When the radius of curvature exceeds this range,the experimental data will deviate greatly.the electric tree initiation,growth and breakdown experiments of Si O2/LDPE and Mg O/LDPE composites were carried out.The results showed that the breakdown strength and the electric tree initial voltage of the two materials were both higher than that of pure LDPE after the addition of nanometers,and the Si O2/LDPE increased more than that of pure LDPE.The nanocomposites increased the most when the content of nano was 1%,and the growth of electric dendrites was inhibited by the addition of nanocomposites,and the content of 2% was the most significant.The tensile strength and the characteristic breakdown strength of the two composite materials were compared and analyzed,and the initial voltage of the characteristic electric tree was also analyzed.It is found that the electrical strength and mechanical strength of Si O2/LDPE and Mg O/LDPE composites are not consistent with each other,and the correlation coefficients of Pearson's electric tree initial voltage,growth length and breakdown field strength of the two composites are obtained by SPSS software.The results show that the initial voltage of Si O2/LDPE and Mg O/LDPE composites with different nano content is positively correlated with the breakdown strength,but there is no correlation between the growth length of the tree and the breakdown strength.