Study On The Property Of MOV

MOV has been used in many areas such as overvoltage restriction due to its excellent electric physical characteristics. This dissertation has studied on the changing law of static parameter, polar effect and nonlinear parameter during the MOV aging and degradation process, combining with the relative theoretical analysis and focusing on the structural characteristics and the electric properties of MOV; meanwhile, the test results has been analyzed and discussed.(1) Impact experiment on MOV. It has been discovered that varistor voltage ascends first and then descends under the influence of MOV impact experiment, and the descending rang surpasses the ascending range Meanwhile, leakage current appears to be linear ascending during this process. Analysis and discussions on the changing characteristics of MOV internal grain structure have been implemented(2) It has also been discovered in the MOV impact experiment that MOV has polar effect, and there is a higher degree of disintegration happened to V-I Characteristic curve when measuring negatively. The polar effect disappears gradually under the alternative impact of positive and negative polar; however, there is still some disintegration happened to V-I Characteristic curve. Combined with ionic migration theory, the data from the impact experiment has been analyzed on the base of double Schottky barrier model inside the MOV.(3) Choose one type of MOV, and it has been found that there is a delay when judging the aging level by varistor voltage and leakage current. It has been expressed in this dissertation that the variation of nonlinear parameter should be considered as the factor which could judge the aging level of MOV according to the physical structural characteristics and the electric properties, and through the analysis on the changing law of nonlinear parameters.