The thesis is based on the process of Weibull probability distribution to determine a lifetime expectancy of a varistor. Necessary information about nonlinear elements which are used in the field of surge protection is provided. Further we also have a description of a varistor and a more detailed overview of the type of varistor manufactured by the company Varsi, which was used for our measurements. It describes the procedure on how we determined the standard for the measurements and the whole process of measurements. Results were interpreted using two-parameter Weibull distribution and we were looking for parameters α and β. Lifetime expectancy wasn't measured in full product lifetime, but considering the number of strikes that varistor can take when exposed to different current loads, which we produced with a strike generator. Data was processed in three ways: with grapf method, linear regression – least squares estimation and with use of the program EasyFit, which is available as a free program on the internet. As a result we got an equasion, based on which we can informatively assume after how many strikes will varistor degrade when exposed to a particular current load.