Vasilevsky V. Predicting the lifetime of the power transformer using a complex model of technical condition of cellulose insulation

The thesis is dedicated to the improvement of mathematical models for forecasting the residual lifetime of a power transformer and the feasibility study of its maintenance strategy by developing a complex model of cellulose insulation technical condition. The complex model of the cellulose insulation technical condition, which consists of a mathematical model of the transformer's real resource formation at the stage of its production and a model of the resource consumption of the power transformer's cellulose insulation during the exploitation phase, is proposed. The mathematical model of water exchange in the system of cellulose insulation - transformer oil in the interrelation with other mathematical models, describing the condition of the transformer in exploitation is developed. The analysis of the effect of maintenance of power transformer (in particular, drying of the active part) on the characteristics of cellulose insulation is carried out. The transformer resource consumption modeling for different maintenance strategies is executed. The simulation justified the need to take into account the maintenance in the calculations of the residual resource and the modeling of the insulation resource consumption in operation. The calculation method for determining the reduction of insulation's lifetime was further developed by adjusting the known formula of the integral of aging by more accu-rate interpolation of the original data used to construct the dependence of the rate of aging on the moisture content of the insulation. For the first time, mathematical models for assessing the influence of the production stage on the assigned resource, which differ by the imperfection of control and stochasticity of the process of resource change during the technological process, are proposed.