CN110889225B - Method for calculating grounding resistance of artificial grounding body - Google Patents
Method for calculating grounding resistance of artificial grounding body Download PDFInfo
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- CN110889225B CN110889225B CN201911187565.4A CN201911187565A CN110889225B CN 110889225 B CN110889225 B CN 110889225B CN 201911187565 A CN201911187565 A CN 201911187565A CN 110889225 B CN110889225 B CN 110889225B
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Abstract
The invention discloses a method for calculating the grounding resistance of an artificial grounding body, which comprises the following steps: regarding the soil particles as soil particle spheres; an electric field formed by the vertical grounding body and surrounding soil is regarded as a cylindrical hemisphere; making one radius of a soil particle sphere be rkiThe hemispheroid is transversely cut into n equal parts, and the height of each part is h; the hemisphere is transversely cut into n equal parts to be viewed as n cylinders, and the radius of the cylinder is rzj(ii) a The bottom area and the radius of the jth cylinder from the bottom to the top of the cylinder are respectively SjAnd rzj(ii) a Resistance calculation model R for constructing spheres with different soil particle resistivityki(ii) a Respectively calculating the volume V of the soil particle sphereQiVolume V of cylindrical hemisphere soil in electric fieldTiAnd the number of soil particles Ni(ii) a Constructing soil resistance calculation model R with different soil resistivityti(ii) a According to model RtiAnd a ground body resistance RTConstructing calculation model R of ground resistance with different soil resistivityJi(ii) a The problem of prior art calculate ground body ground resistance have calculation error big etc. is solved.
Description
Technical Field
The invention belongs to the technical field of artificial grounding, and particularly relates to a method for calculating grounding resistance of an artificial grounding body.
Background
In a low-voltage distribution network, the neutral point grounding resistance of the low-voltage side of a distribution transformer directly influences the power quality of electricity consumption of an electricity user, the contact voltage of human bodies of operation maintainers and other personnel, the insulation degree of electrical equipment, the three-phase balance of operation and the like. The current method for calculating the grounding resistance of the artificial grounding body mainly comprises the following steps: formula empirical method.
If the formula for calculating the grounding resistance of the vertical grounding body is as follows:
wherein rho is the resistivity of the soil, l is the buried depth of the grounding body, and d is the diameter of the tubular grounding body. The formula shows that the resistivity rho of the soil is unchanged, but the actual soil layers are possibly different, the resistivity of the soil is also different, and the calculation error of the formula is large; l in the formula is the buried depth of the grounding body, and the larger l is, the smaller the grounding resistance is, but the depth relation with the buried depth of the grounding body is not large; therefore, the problems of large calculation error and the like exist in the prior art for calculating the ground resistance of the ground body.
The invention content is as follows:
the technical problem to be solved by the invention is as follows: the method for calculating the grounding resistance of the artificial grounding body is provided, and the problems that the calculation error is large and the like in the prior art for calculating the grounding resistance of the grounding body are solved.
The technical scheme of the invention is as follows:
a method for calculating the grounding resistance of an artificial grounding body comprises the following steps:
Step 8, constructing soil resistance R with different soil resistivity according to the steps 6 and 7tiCalculating a formula;
step 9, soil resistance R according to different soil resistivity in step 8tiAnd a ground body resistance RTConstruction of ground resistance R with different soil resistivityJAnd (4) calculating a formula.
In step 3, the equal height h values are:
radius r of the cylindrical circle of the particle spherezjBottom area S of the cylinderjThe calculation method comprises the following steps:
Sj＝π·rzj 2。
resistance value RkiThe calculation formula is as follows:
volume value V of soil particle sphereQiVolume value V of electric field cylindrical hemisphere soilTiAnd a soil particle number value NiThe calculation method comprises the following steps:
rcto ground the radius of the cylindrical hemisphere electric field, generally rcH is the height of the vertical grounding body, wherein the height is 15-20 m.
Soil resistance R of different soil resistivitytiThe calculation expression is:
ground resistance R with different soil resistivityJThe calculation formula is as follows:
where ρ isJIs the resistivity of the material of the grounding body, SJThe cross-sectional area of the cylindrical grounding body.
The invention has the beneficial effects that:
the model and calculation designed by the invention can be used for calculating the grounding resistance more accurately and has smaller error aiming at the soil layers with various soil resistivities; the problem of prior art calculate ground body ground resistance have calculation error big etc. is solved.
Drawings
FIG. 1 is a schematic diagram of a grounding system with a soil particle sphere fused with a grounding body;
FIG. 2 is a schematic diagram of a cylindrical hemisphere electric field of a grounded system;
FIG. 3 is an equivalent schematic diagram of a hemisphere resistance of a soil particle;
FIG. 4 is a flow chart of a model and a calculation method for deriving the ground resistance of soil particle resistance.
The specific implementation mode is as follows:
the invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
As shown in fig. 1, in the distribution transformer neutral grounding system, the soil particles are regarded as countless soil globules contacting with the grounding body to form an integral grounding electric "body".
As shown in FIG. 2, in the neutral point grounding system of the distribution transformer, the grounding body forms a cylindrical and hemispherical electric field in the soil and is perpendicular to the periphery r of the grounding bodycThe total number of televisions except 15-20 m is zero, namely the sum of the soil particle resistances in the cylinder and the hemisphere is regarded as the soil resistance R of the grounding bodyti。
As shown in fig. 3, the resistivity is taken as ρkiThe upper hemisphere of the soil particle is cut into n equal parts, each equal part is equal in height, each part is regarded as a cylinder, and the resistance value R of the upper hemisphere of the soil particle can be calculatedki。
As shown in fig. 4, a calculation flow chart can be detailed as follows:
(1) regarding the soil particles as soil particle spheres;
(2) an electric field formed by the vertical grounding body and surrounding soil is regarded as a cylindrical hemisphere;
(3) according to the step (1), one radius of the soil particle sphere is rkiThe hemispheroid is transversely cut into n equal parts, and the height of each part is h;
(4) according to the step (3), the hemisphere is transversely cut into n equal parts to be viewed as n cylinders, and the radius of the cylinders is rzj；
(5) The bottom area and the radius of the jth cylinder from the bottom to the top of the cylinder are respectively S according to the step (4)jAnd rzj；
(6) Constructing a resistance calculation model R of spheres with different soil particle resistivity according to the step (5)ki；
(7) Respectively calculating the volume V of the soil particle sphere according to the steps (1) and (2)QiVolume V of electric field cylinder soilTiAnd the number of soil particles Ni；
(8) Constructing soil resistance values R with different soil resistivities according to the steps (6) and (7)tiCalculating a formula;
(9) according to step (8) RtiAnd a ground body resistance RTObtaining grounding resistance R with different soil resistivityJ；
In the step (3), the equal height h value is as follows:
in the steps (4) and (5), the radius r of the cylindrical circle of the particle spherezThe base area value of the cylinder is Sj：
Sj＝π·rzj 2；
In the step (6), the resistance values R of the spheres with different soil particle resistivitykiComprises the following steps:
the hemisphere is transversely cut into n equal parts, which are considered as n cylinders.
In the step (7), the volume value V of the sphere of the soil particlesQiVolume value V of electric field cylindrical hemisphere soilTiAnd a soil particle number value NiRespectively as follows:
wherein r iscFor electric fields of cylindrical hemispheres of earthed bodiesRadius, general case rcH is the height of the vertical grounding body, wherein the height is 15-20 m;
in the step (8), the soil resistance values R of different soil resistivitiestiComprises the following steps:
In the step (9), the grounding resistance values R of different soil resistivitiesJComprises the following steps:
Where ρ isJIs the resistivity of the material of the grounding body, SJThe cross-sectional area of the cylindrical grounding body.
Claims (6)
1. A method for calculating the grounding resistance of an artificial grounding body comprises the following steps:
step 1, regarding soil particles as soil particle spheres;
step 2, regarding an electric field formed by the vertical grounding body and surrounding soil as a cylindrical hemisphere;
step 3, setting one radius of the soil particle sphere as rkiThe hemispheroid is transversely cut into n equal parts, and the height of each part is h;
step 4, transversely cutting the hemispheroid into n equal parts to be viewed as n cylinders, wherein the radius of the cylinders is rzj；
Step 5, respectively setting the bottom area and the radius of the jth cylinder from the bottom to the top of the cylinder to be S according to the result of the step 4jAnd rzj；
Step 6, constructing resistance calculation models R of spheres with different soil particle resistivityki；
Step 7, respectively calculating the volume V of the soil particle sphereQiCylindrical hemisphere soil of electric fieldVolume of soil VTiAnd the number of soil particles Ni；
The volume value V of the soil particle sphereQiVolume value V of electric field cylindrical hemisphere soilTiAnd a soil particle number value NiThe calculation method comprises the following steps:
rcto ground the radius of the cylindrical hemisphere electric field, generally rcH is the height of the vertical grounding body, wherein the height is 15-20 m;
step 8, constructing soil resistance R with different soil resistivity according to the steps 6 and 7tiCalculating a formula;
step 9, soil resistance R according to different soil resistivity in step 8tiAnd a ground body resistance RTConstruction of ground resistance R with different soil resistivityJAnd (4) calculating a formula.
2. The method for calculating the grounding resistance of the artificial grounding body according to claim 1, characterized in that: in step 3, the equal height h values are:
3. the method for calculating the grounding resistance of the artificial grounding body according to claim 1, characterized in that: radius r of the cylindrical circle of the particle spherezjBottom area S of the cylinderjThe calculation method comprises the following steps:
Sj＝π·rzj 2。
4. the method for calculating the grounding resistance of the artificial grounding body according to claim 1, characterized in that: resistance value RkiThe calculation formula is as follows:
where rhokiResistivity of soil particles.
5. The method for calculating the grounding resistance of the artificial grounding body according to claim 1, characterized in that: soil resistance R of different soil resistivitytiThe calculation expression is:
where rhokiResistivity of soil particles.
6. The method for calculating the grounding resistance of the artificial grounding body according to claim 1, characterized in that: ground resistance R with different soil resistivityJThe calculation formula is as follows:
where ρ isJIs the resistivity of the material of the grounding body, SJThe cross-sectional area of the cylindrical grounding body.
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