CN114167723A - Method for establishing unified model of grounding grids of multiple transformer substations - Google Patents
Method for establishing unified model of grounding grids of multiple transformer substations Download PDFInfo
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- 239000002689 soil Substances 0.000 claims abstract description 25
- 239000002344 surface layer Substances 0.000 claims description 4
- 239000004576 sand Substances 0.000 claims description 3
- 238000009933 burial Methods 0.000 abstract 1
- 230000001932 seasonal effect Effects 0.000 description 15
- 238000004364 calculation method Methods 0.000 description 6
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Abstract
The method includes the steps that the area of a grounding grid of each transformer substation is obtained based on input soil resistivity and grounding resistance, a grid-shaped grounding grid model is set up without exceeding six conductors, and the burial depth and the area of the grounding grid model are corrected based on the safety characteristics of the grounding grid to form the grounding grid unified model.
Description
Technical Field
The invention relates to the technical field of transformer substations, in particular to a method for establishing a unified grounding grid model of a plurality of transformer substations.
Background
With continuous progress of science and technology and rapid development of economy, the demand of society on power development is rapidly increased, and the construction of power grid infrastructures such as transformer substations and power transmission lines is continuously increased. The power industry is an industry ahead of social development, and the capacity increasing speed of a power system must be ahead of the economic development speed. As a hub for energy intersection in an electric power system, the safe and stable operation of a transformer substation must be ensured, and a grounding system of the transformer substation is used as a first household for ensuring the safe and stable operation of the transformer substation, and naturally becomes an important measure for ensuring the safety of personnel, a power grid and equipment. In order to ensure the safety of the grounding grid after the transformer substation is put into operation, the procedures of design, laying and the like of the grounding grid need to be strictly controlled, and the design of the grounding grid of the transformer substation is used as an initial source of a grounding system, and the quality of the grounding grid is directly related to the hidden danger handling condition after the grounding grid fails.
At present, the grounding grid model of the transformer substation is built and stays more under the condition of few transformer substations, the grounding grid model of a single transformer substation is complex, the number of conductors is large, and when a plurality of transformer substations are involved, the complex grounding grid model can lead to complex calculation and low calculation efficiency. Therefore, on the premise of meeting the requirement of engineering calculation, the method is gradually simplified, a unified model is built, and the calculation efficiency of the grounding network under the condition of the multi-substation is improved.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is well known to those of ordinary skill in the art.
Disclosure of Invention
The method for establishing the grounding network unified model of the multiple substations is provided for solving the problem that the existing grounding network model of the substation is insufficient in computational efficiency under the condition of a multi-substation and can be applied to aspects such as different seasonal factors.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention discloses a method for establishing a unified grounding grid model of a plurality of substations, which comprises the following steps:
the grounding grid area of each substation is obtained based on the soil resistivity and the grounding resistance of the area where the substation is located,
six conductors build a grid-shaped grounding net model,
and modifying the buried depth of the grounding grid model and the area of the grounding grid based on the safety characteristic of the grounding grid to form a uniform grounding grid model.
In the method for establishing the unified grounding grid model of the multiple substations, the safety characteristics of the grounding grid comprise step voltage and contact voltage.
In the method for establishing the unified model of the grounding grid of the plurality of transformer substations, the step voltage safety limit value UsAnd contact voltage safety limit UtAre respectively as
Where ρ issThe resistivity of the surface layer of the place where the human feet stand is represented by omega m, and t is the duration time of the grounding short-circuit current and is represented by s.
In the method for establishing the unified model of the grounding grid of the multiple substations, the outline of the shape like the Chinese character tian is square, the two middle lines of the shape like the Chinese character tian are two middle lines of the square, and the six conductors comprise four sides and two middle lines of the square.
In the technical scheme, the method for establishing the grounding grid unified model of the plurality of substations provided by the invention has the following beneficial effects: according to the method for building the unified grounding grid model of the multiple substations, a small number (less than or equal to six conductors, such as five or four conductors, described in detail later) of conductors are used for building the grounding grid of the substation in a large area into a full-grid loop model, and the calculation is convenient. The method is suitable for adjusting the buried depth and the area of the grounding grid by different seasonal factors, and has universality.
Drawings
In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic diagram of a grounding network model building process according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a single horizontal line according to an embodiment of the present invention;
fig. 4 is a diagram of a grounding grid model according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the equipment or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
In order to make the technical solutions of the present invention better understood, those skilled in the art will now describe the present invention in further detail with reference to the accompanying drawings.
In one embodiment, the invention discloses a method for establishing a unified grounding grid model of a plurality of substations, which comprises the following steps:
acquiring the area of a grounding grid of each transformer substation based on the soil resistivity and the grounding resistance of the area where the transformer substation is located;
constructing a field-shaped grounding network model by six conductors;
and modifying the buried depth of the grounding grid model and the area of the grounding grid based on the safety characteristic of the grounding grid to form a uniform grounding grid model.
In another embodiment of the present invention, the substrate is,
the grounding grid safety characteristics include a step voltage and a contact voltage.
In another embodiment of the present invention, the substrate is,
step voltage safety limit UsAnd contact voltage safety limit UtAre respectively as
Where ρ issThe resistivity of the surface layer of the place where the human feet stand is represented by omega m, and t is the duration time of the grounding short-circuit current and is represented by s.
In another embodiment of the present invention, the substrate is,
the outline of the Chinese character tian is square, the two middle lines of the Chinese character tian are two middle lines of the square, and the six conductors comprise four sides and two middle lines of the square.
In another embodiment of the present invention, the substrate is,
five conductors can also replace a grid-shaped grounding grid model; the five conductors comprise four sides of a square and a middle line of the square.
In another embodiment of the present invention, the substrate is,
the four conductors can also replace a grid-shaped grounding grid model; wherein the four conductors include four sides of a square.
Referring to fig. 1-4, in another embodiment, in order to be more accurate and more consistent with the field, the method for establishing the unified model of the multiple substation grounding grids comprises the following steps:
(1) combining the required soil resistance coefficient and the grounding resistance of the transformer substation, and constructing an abstract power grid network frame of the grounding network through a grounding system estimation program;
wherein, the construction of electric wire netting rack includes:
1. generating a grounding grid, namely acquiring the area of the grounding grid of each station by inputting the resistivity of soil and the grounding resistance; illustratively, the side length of a square grounding network can be obtained by inputting the numerical values of the resistivity and the grounding resistance of soil in cdegs software, so that the area of the grounding network of each station is calculated;
2. the influence of seasonal factors on the soil resistivity is considered, and the soil resistivity is influenced under different soil environment temperatures and humidity, so that the normal work of a grounding system is influenced. Because the soil resistivity is an important factor directly influencing current distribution in the ground, ground surface potential and step voltage, the influence of temperature factors is considered, and the accurate construction of a grounding grid model is facilitated;
(2) through the safety characteristic standards of the grounding grid of the step voltage and the contact voltage of the grounding grid of the transformer substation, an accurate basis is provided for setting the buried depth and the area of the grounding grid, the simulation accuracy is verified, the simulation model is corrected, and the grounding grid model is optimized to obtain a unified model of the grounding grid of the transformer substation, as shown in fig. 1.
As shown in fig. 1, the area of the grounding grid of each substation is obtained through calculation in cdegs software based on the soil resistivity and the grounding resistance of the region where the substation is located, a grid-shaped grounding grid model is built by six conductors, and the buried depth of the grounding grid model and the area of the grounding grid are corrected based on the safety characteristics of the grounding grid to form a unified grounding grid model. After the model building of the multi-substation grounding grid is completed, judging the safety characteristics of the grounding grid of the step voltage and the contact voltage of the grounding grid, and if the safety characteristics of the grounding grid are met, completing the model building if the judgment result is yes; otherwise, returning to correct the model area and the buried depth of the grounding grid, and rebuilding the model and judging.
As shown in fig. 2, for a power generation station that is already operating, the main factor affecting the safety performance of the grounding system is the seasonal factor. The two most obvious seasonal factors affecting soil resistivity are rainfall and freezing. Measurements on clay samples show an electrical resistivity of 1400 Ω · m at a water content of 2.5%, and the electrical resistivity drops to around 15 Ω · m when the water content is increased to 25%. The resistivity to the surface soil of saline-alkali areas will become very small in rainy seasons. The resistivity of the hydrous rock soil is obviously increased along with the reduction of the temperature when the temperature of the frozen ground is below 0 ℃. When the temperature drops to nearly-20 ℃, the resistivity is as high as 106 Ω · m. Under the condition of considering seasonal factors, parameters such as the depth, the length and the diameter of the horizontal lead conductor are determined, and a field-shaped grounding network model with six (less) conductors is built.
In one embodiment, the grounding system software CDEGS is used for inputting the soil resistivity of the region where the transformer substation is located and the actual grounding resistance of the transformer substation to estimate the area of the transformer substation grounding grid.
According to the method, the influence of different seasonal factors on the resistivity of the soil is considered, the building of the grounding grid model is further influenced, the safety verification of the step voltage and the contact voltage of the grounding grid is carried out, and the accuracy of building the grounding grid model under the multi-substation is guaranteed by a small number of conductors.
The present invention will be further described with reference to table 1, fig. 3 and 4.
Table 1 is a soil dry season coefficient table, which is corrected as follows, taking into account that the seasonal weather change factor is often multiplied by a seasonal coefficient.
TABLE 1 soil dry season coefficient table
ρmax＝ψρ
Where rhomaxThe maximum resistivity of soil (omega. m); ρ is the measured resistivity (Ω · m); psi is a seasonal coefficient which is divided into a horizontal grounding seasonal coefficient and a vertical grounding seasonal coefficient.
A single horizontal conductor is shown in fig. 3. Fig. 3 is a single horizontal straight conductor laid horizontally under the earth's surface or buried deep in the soil, the buried depth, length and diameter of the conductor in fig. 3 being determined by the SESGSE module in cdegs software according to the influence of seasonal factors on the soil resistivity and the value of the ground resistance.
The grounding grid model composed of six horizontal conductors is shown in fig. 4, and the length and width of the grounding grid and the buried depth can be determined by the parameters of a single horizontal conductor.
Regarding the safety characteristics of the grounding grid, mainly considering whether the step voltage and the contact voltage meet the specifications, for the grounding network model of the multi-substation concerned by the patent, according to the provisions of item 3.4 of DL/T621-
Where ρ issThe resistivity (omega. m) of the surface layer of the place where the human foot stands, and t is the duration(s) of the grounding short (fault) current. According to the relation between resistance and voltage in ohm's law, the smaller the grounding resistance value is, the lower the contact voltage and the step voltage are, the safer the human body is, if the obtained model step voltage and the contact voltage are greater than the safety limit value, the grounding resistance value needs to be reduced, and the field-shaped grounding network model and the buried depth are redesigned. Specifically, if the step voltage and the contact voltage do not meet the specification, the grounding resistance is modified to further modify and optimize the area of the grounding grid model, that is, the step of building the model is re-executed and whether the specification is met is judged again; as far as the buried depth is concernedI.e. the depth of the conductor, the buried depth of the conductor in fig. 3 is determined by the SESGSE module in cdegs software again according to the influence of seasonal factors on the soil resistivity and the value of the ground resistance after the ground resistance is also modified.
In another embodiment of the present invention, the substrate is,
acquiring the area of a grounding grid of each transformer substation based on the soil resistivity and the grounding resistance of the area where the transformer substation is located; illustratively, where the soil resistivity is selected, seasonal factors are taken into account; the selection of the grounding resistance can be set according to the requirements of the transformer substation, the transformer substations with different specifications have different requirements, and the two parameters can be determined according to the historical values of the local transformer substations with the same specification and can be measured again on site; after obtaining the two parameters, the two parameters are led into cdegs software to be calculated to obtain the buried depth, the length and the diameter of the six conductors, and the grounding grid area of each transformer substation is obtained.
Finally, it should be noted that: the embodiments described are only a part of the embodiments of the present application, and not all embodiments, and all other embodiments obtained by those skilled in the art without making creative efforts based on the embodiments in the present application belong to the protection scope of the present application.
While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that the described embodiments may be modified in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are illustrative in nature and should not be construed as limiting the scope of the invention.
Claims (4)
1. A method for establishing a unified grounding grid model of a plurality of transformer substations is characterized by comprising the following steps:
acquiring the area of a grounding grid of each transformer substation based on the soil resistivity and the grounding resistance of the area where the transformer substation is located;
constructing a field-shaped grounding network model by six conductors;
and modifying the buried depth of the grounding grid model and the area of the grounding grid based on the safety characteristic of the grounding grid to form a uniform grounding grid model.
2. The method for unified modeling of grounding grid of multiple substations according to claim 1, characterized in that, preferably, the grounding grid safety characteristics include step voltage and contact voltage.
3. The method for unified modeling of grounding grids of multiple substations according to claim 2, characterized by a step voltage safety limit UsAnd contact voltage safety limit UtAre respectively as
Where ρ issThe resistivity of the surface layer of the place where the human feet stand is represented by omega m, and t is the duration time of the grounding short-circuit current and is represented by s.
4. The method of claim 1, wherein the grounding grid unified modeling method for a plurality of substations,
the outline of the Chinese character tian is square, the two middle lines of the Chinese character tian are two middle lines of the square, and the six conductors comprise four sides and two middle lines of the square.
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