In thermal equilibrium the electrical neutrality of the charge dislocation is assured by a cloud of oppositely charged point defects around it. Here, from the view point of thermodynamics of line vacancies, we propose a possibility of constructing a model of transient electric current generation in an earthquake source zone which combines polarization processes and motion of charged dislocations under the influence of evolving field of stresses. This transient electric current differs essentially from the piezo-electric current in which the electric field is proportional to the stress itself. Then we review briefly the elements of stress evolution theory. Some examples of the stress evolution pattern with the electromagnetic field radiation are shown.