SU881921A1 - Earthing grid - Google Patents

Description

(54) GROUNDING GRID.

I

The invention relates to electric power industry, in particular, to grounding devices, and can be used for grounding transformer substations and opening switchgears that occupy a large area.

With the development of electric power engineering, when switching to 220, 500, 750, 1150 kV voltage classes, the size of transformer substations increased significantly and almost always exceeded an area of 100x100 m. For large electrical installations, as a device for leveling touch coefficients, grounding grid. The alignment of priko coefficients (noveny by grounding grids is achieved by placing grounding electrodes with a certain tag.

The closest to the proposed technical solution is a grounding grid containing horizontal 11dog1 and transverse grounding electrodes arranged with a variable tag, increasing

To the center of the protected area by exponential law 1.

A disadvantage of the known grid is that the exponential law of placement of horizontal electrodes, which causes a grid thickening to the periphery, does not ensure alignment of touch coefficients at the electrical installation site if the resistivity of the soil is lower than 400 Ω m. the ground resistance Rd 400 ohmM along with the peripheral areas of the grid an essential role in the processes of current flowing into the ground is played by the areas of the grid adjacent to the current injection site, in connection with

Claims (1)

15 with significant longitudinal resistance of the horizontal grid electrodes. Therefore, at ER 7,400 Ohm-m, to level the contact coefficients olnp, it is necessary to thicken the grounding electrodes at the current injection points, which is not provided for in the known. the grid. This means that the known mesh is efficient only in high-resistivity soils (Re 7,400 ohm-m). 3 The purpose of the invention is to equalize the electrical safety conditions in a protected area with a soil resistivity of 10-400 OmM. The goal is achieved by the fact that the grounding grid, containing horizontal longitudinal and transverse grounding electrodes with variable pitch, is made in increments between the transverse grounding conductors. electrodes, the smallest at the current injection site and at the maximum distance from it, determined by the formula Vi-stio-r-explB), where 41 o is the distance between the transverse horizontal grounding electrodes of the current input site, m; g is the distance from the point of current input, m А 0, llPnfs S is the area occupied by the grid; B - 1.34 - 0.048G + 0.01R8riT - OflOSSrfnff is an exponential function index; f - equivalent resistivity of the soil. The mathematical description of the change in the grid pitch was carried out using a regression analysis of the calculated and experimental results of determining the coefficient of contact on large-area grounding devices embedded in soils with a specific resistance of 10-400 ohm-m. The drawing shows the grid grounding Grid contains longitudinal horizontal grounding electrodes 1 and transverse electrons 2 located at the same depth in the ground and interconnected electrically at the intersections, J is the place where the current is introduced into the grid. The device works as follows. During short circuits in the system, the current is introduced into the grid at the point L and flows down into the earth from the transverse 2 and the longitudinal horizontal grounding electrodes unevenly. The step size of the fir grid is functionally related to 3} 1fences fj i S, r, which causes the grid to thicken in areas maximally loaded with current flowing into the ground. At the same time, the densities of the currents flowing down from the unit length of the electrode are kept constant, which ensures alignment of the contact coefficients in the protected area. The proposed grounding grid flattens the values of touch coefficients in the protected area with a ground resistivity of up to 400 Ohm-m. Claims Ground grid comprising horizontal longitudinal and transverse grounding electrodes arranged with variable pitch, characterized in that, in order to equalize electrical safety conditions in the protected area with a specific soil resistance of 10-400 ohm, the grid is made with a gap between the transverse ground the smallest at the current injection site and at the maximum distance from it, defined by the formula iio. (6), where tiQ is the distance between the transverse horizontal grounding electrodes at the site current input, m; D is the distance from the point of current input, m; A 0.11 P5; S is the area occupied by the grid; , 34 - 0.048 g + 0, 0.0055renf5 is an exponential function indicator; Yar - equivalent resistivity of the soil. Sources of information taken into account in the examination of 1, USSR Author's certificate N 412648, cl. H 02 B 1/16, 1970 (prototype). g 1