Fedoseienko O. The Determination of electrical characteristics of grounding connections of electrical installations on the basis of volumetric grounds full modeling

The thesis is devoted to the important scientific and applied problem solution in improving the electrical installations grounding devices by optimizing the design parameters of complex combined grounding systems of projected or existing electrical installations by using manufactured high conductivity ground electrodes, as well as by taking into account natural concentrated grounds. Have been applied induced potential method and methods for computing branched electrical circuits with distributed parameters, a technique of solving a point electrical current source electric potential problem, so as to create a mathematical model for a non-equipotential. In addition, methods of matrix theory, linear system solving, and programming for mathematical model realization have been employed along with physical testing methods for theoretical conclusions verification. The method of natural concentrated grounds substitution by the set of electrodes taking natural current spreading conductivity of concrete pole armature into account for complicated grounding connections calculation is offered. An equivalent model as a set of linear electrodes in accordance with equivalent electric characteristics such as the resistance approximation and the approach of the points potential on the earth surface in two-layer ground is chosen. The optimization method of ground grid structural parameters with the use of grounding electrodes of increased current spreading conductivity has been invented. The new engineering solution is got is the grounding electrode of increased current spreading conductivity, which will be realized as a vertical electrode with current installing antirust coating, placed in the limited volume of fine-dyspersated technical carbon. The task of its substitution by the set of electrodes for calculation of complicated unequipotential grounding connections has been solved. The mathematical model of non-potential grounding device of electrical installations has been built, which differs from the existing taking into account of volumetric grounding, located in a conducting two-layer semi-space. The developed model allows the introduction of natural grounding, namely racks and soles, as well as a vertical electrode of high conductivity, in grounding device normalized parameters computation, by the set of rectilinear electrodes. The introduced model makes it possible to get the grounding device specified parameters. Based on the solution to the electric potential problem for a point electrical current source, a mathematical model of the induced potential calculation for electrode, located in the lower layer of a two-layered model of land, as well as at an arbitrary distance from the surface of the earth in a two-layered soil, has been built. Expressions of mutual and own resistances of vertical and horizontal electrodes for calculation of complicated grounding connections as it applies to the location of horizontal electrodes in the understratum of two-layer electric structure of earth are got. On the basis of the created mathematical models, the software tools that were used in calculating the electric field were developed. The technique for determining the short-circuit currents distribution along the electrodes and potentials in the nodes of the electrical installation grounding device has been developed. It is shown that the developed solution use of the given problem makes it possible to reveal the most safe in terms of electromagnetic compatibility of the electrical installation area for laying information and control circles on them. The algorithm for calculating complex nonequipotential grounding grids in view of volumetric grounders electrical conductivity has been Improved. The method of natural concentrated grounders substitution by the set of electrodes taking them into account in the algorithm of electric characteristics calculation for complicated grounding connections of electric installation is offered. The using of the proposed calculation algorithm in the electric grids of JSC "Kharkivoblenergo" made it possible to determine the values of the potential distribution at short circuit in an electrical substation taking into account the influence of the conductivity of natural concentrated grounds. Developed electrodes of increased current spreading conductivity are mounted as experimental and industrial samples at Substation Ordzhonikidze-110 kV, JSC "Kharkivoblenergo". Their application ensured reduction of the design values of the contact voltage in those places on the GRP-110 kV substation, where they exceeded the permissible ones, to values significantly lower than the permissible ones.