In the article we consider the calculation of electrostatic field being formed by a number of charged electrodes which have to be represented as unclosed surfaces in R3. The effective algorithms for this problem solving in the essential -pace case can be obtained by integral equations method. The main object of our investigations is the construction of approximate schemes for solving some of two-dimensional integral equations of the first kind with weak singularities in kernels. Singular behaviour of desired "charge distribution density" in the neighborhood of some isolated points on boundary surfaces was taken into account by various ways.