Some features of the electro-physical processes that arise in solid dielectric media with the presence of water under the action of strong electric fields are determined. On the example of cross-linked polyethylene insulation of superhigh-voltage cables, the amplifications of the electric field, the increase in current densities and the rise of surface forces in the local regions of the insulation with increasing density of close located water micro-inclusions are calculated. Using the developed mathematical model on the basis of the finite element method, the dependences of the abovementioned values on the number and mutual distances between