CN102222903A - Method for determining and segmenting grounding pole field domain of direct current (DC) transmission system - Google Patents
Method for determining and segmenting grounding pole field domain of direct current (DC) transmission system Download PDFInfo
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- CN102222903A CN102222903A CN2011101905820A CN201110190582A CN102222903A CN 102222903 A CN102222903 A CN 102222903A CN 2011101905820 A CN2011101905820 A CN 2011101905820A CN 201110190582 A CN201110190582 A CN 201110190582A CN 102222903 A CN102222903 A CN 102222903A
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Abstract
The invention discloses a method for determining and segmenting a grounding pole field domain of a direct current (DC) transmission system. The method comprises the following steps of: (1) determining a field domain of a grounding pole according to the shape of the grounding pole; and (2) performing three-dimensional segmentation on the field domain of the grounding pole by using a fan segmentation method or a rectangle segmentation method according to the shape of the grounding pole so as to obtain a plurality of unit blocks. In the method for determining and segmenting the grounding pole field domain, the range of the grounding pole field domain is determined according to the shape of the grounding pole, a current field calculating area is defined in a certain range, the analysis of an open field in an actual system is avoided, and a computation model is simplified on the premise of guaranteeing the precision; meanwhile, non-uniform segmentation is adopted under the conditions of different depths and ranges, the segmentation is denser close to an electrode and is sparse away from the electrode, the computational accuracy and speed are considered, the field domain is finely determined and segmented, and the method is simple and high in university; therefore, the computed result of the grounding pole current meets the high-precision requirement.
Description
Technical field
The invention belongs to electric power system technology of transmission of electricity field, be specifically related to determining and dividing method of a kind of DC transmission system earth electrode field domain.
Background technology
The typical shape of direct current transportation earth electrode mainly is divided into: linear pattern, star-like, circular ring type and racetrack.Using at present is circular ring type and racetrack earth electrode comparatively widely, wherein can be subdivided into shapes such as monocycle, dicyclo, three rings again according to the number of rings difference.Figure 1 shows that the arrangement and the schematic cross-section of single circular ring type earth electrode, the earth electrode global shape is an annulus, it is spliced by some feed rod, horizontal shallow embedding is in soil, feed rod is filled with coke layer outward to reduce the galvano-cautery effect, can reduce the current density between electrode and the soil contact simultaneously.
Calculate the grounding electrode electric current field is the important content of design of DC transmission system earth electrode and construction, also is simultaneously the basis that calculate in the earth electrode temperature field.The computational methods of grounding electrode electric current field mainly contain boundary element method, Finite Element, traveling wave method and resistor network method etc. at present.
Wherein, based on the direct current transportation grounding electrode electric current field computational methods of resistance network model, algorithm thought is simple, and versatility is stronger.Its basic thought is whole earth electrode to be calculated field domain be divided into some junior units on three-dimensional, according to the shape and the soil resistivity thereof of piecemeal, calculates the equivalent resistance of each unit on three-dimensional.For each unit, with 6 equivalent resistances, be connected with adjacent on every side unit respectively, so just constituted a basic circuit network that only contains resistive element.So far, the computational problem of earth electrode current field is converted into the calculating to simple circuit network and has found the solution problem.
Below this type of algorithm relates to determining and segmentation problem of earth electrode field domain scope as can be known, and present existing field domain scope determines that mode is comparatively general, and its dividing method is rough relatively, is not very good calculating on the effect, and precision is not high; Thereby cause grounding electrode electric current field result calculated confidence level not high, and then relevant design and the construction of influence, and follow and have corresponding potential safety hazard.
Summary of the invention
What the invention provides a kind of DC transmission system earth electrode field domain determines and dividing method that field domain is determined to cut apart meticulous, and method is simple, and highly versatile makes grounding electrode electric current field result of calculation satisfy high-precision requirement.
Determining and dividing method of a kind of DC transmission system earth electrode field domain comprises the steps:
(1), determines the field domain of earth electrode according to the shape of earth electrode; Described earth electrode is included in the field domain, and described field domain is a straight cylinder, and the end face of straight cylinder is a ground level, and the axis of earth electrode overlaps with the axis of straight cylinder;
(2) according to the shape of earth electrode, employing fan-segmentation method or rectangle split plot design are carried out three-dimensional segmentation to the field domain of earth electrode, obtain several cell blocks.
In the optimized technical scheme, the height of described field domain is 100km; Described earth electrode be shaped as circular ring type or star-like, the cross section of its field domain is circular, radius is 20km; Described earth electrode be shaped as linear pattern, the cross section of its field domain is a square, the length of side is 40km; Described earth electrode be shaped as racetrack, the cross section of its field domain is a runway shape, the radius of runway shape two ends semicircle is 20km, the straight way length of runway shape is the straight way length of racetrack earth electrode.
In the optimized technical scheme, described earth electrode be shaped as circular ring type or star-like, adopt the fan-segmentation method that its field domain is carried out three-dimensional segmentation; Described earth electrode be shaped as linear pattern, adopt the rectangle split plot design that its field domain is carried out three-dimensional segmentation; Described earth electrode be shaped as racetrack, adopt fan-segmentation method and rectangle split plot design that its field domain is carried out three-dimensional segmentation.
Described fan-segmentation method comprises the steps:
(1) setting up with the cylinder or the semicylinder end face center of circle is initial point, and the vertical ground direction is the cylindrical-coordinate system of z direction;
(2) height and the radius with cylinder or semicylinder is divided into several height segment and radius segments respectively; Obtain θ to the z of division coefficient, each height segment to the r of division coefficient, each radius segment to division coefficient;
(3) according to θ to division coefficient, along the θ direction cylinder or semicylinder are averaged and to cut apart; In each height segment according to the z of correspondence to division coefficient, along the z direction cylinder or semicylinder are averaged and to cut apart; In each radius segment according to the r of correspondence to division coefficient, along the r direction cylinder or semicylinder are averaged and to cut apart, obtain the plurality of sector cell block.
Described rectangle split plot design comprises the steps:
(1) setting up with cuboid end face center is initial point, and cuboid end face long side direction is the x direction, and the vertical ground direction is the three-dimensional system of coordinate of z direction;
(2) with length, the width of cuboid be divided into several length of interval sections, width segment and height segment highly respectively; The x that obtains each length of interval section to the y of division coefficient, each width segment to the z of division coefficient, each height segment to division coefficient;
(3) in each length of interval section according to the x of correspondence to division coefficient, along the x direction cuboid is averaged and to cut apart; In each width segment according to the y of correspondence to division coefficient, along the y direction cuboid is averaged and to cut apart; In each height segment according to the z of correspondence to division coefficient, along the z direction cuboid is averaged and to cut apart, obtain several rectangular element pieces.
Useful technique effect of the present invention is:
(1) earth electrode field domain of the present invention determines and dividing method, determine earth electrode field domain scope according to the earth electrode shape, the current field zoning is limited within the specific limits, avoided analysis, under the prerequisite that guarantees precision, make computation model obtain simplifying the open field domain of real system.
(2) determining and dividing method of earth electrode field domain of the present invention, to the field domain scope determine comparatively flexibly, make convenient to the cutting of earth electrode field domain.
(3) earth electrode field domain of the present invention determines and dividing method, adopted inhomogeneous cutting at different depth and length, closeer near the cutting of electrode place, more sparse away from the cutting of electrode place, computational accuracy and speed have been taken into account, compare traditional even cutting mode and have great advantage, under equal computational speed, the computational accuracy of grounding electrode electric current field is compared traditional cutting mode obvious lifting.
(4) earth electrode field domain of the present invention determines and dividing method, allow soil resistivity on three dimensions, to change arbitrarily, thereby being particularly suitable for that soil resistivity is all inhomogeneous in the horizontal and vertical directions, the calculating of the grounding electrode electric current field that presents the undulating topography geologic feature, applicability is stronger.
Description of drawings
Fig. 1 (a) is the structural representation of single circular ring type earth electrode.
Fig. 1 (b) is the layout plan of single circular ring type earth electrode.
Fig. 2 is the flow chart of steps of the definite and dividing method of earth electrode field domain of the present invention.
Fig. 3 is the structural representation of two circular ring type earth electrodes.
Fig. 4 is the cell block structural representation after the earth electrode field domain of the present invention fan-segmentation.
Fig. 5 is the substitutional resistance schematic network structure of sector element piece.
Embodiment
In order more specifically to describe the present invention, the definite of earth electrode field domain of the present invention is elaborated with dividing method below in conjunction with the drawings and the specific embodiments.
With certain ± the 800kV DC transmission engineering is an example, adopts the inventive method to determine and cuts apart the earth electrode field domain, form resistor network, and then the earth electrode current field calculated, and compare with the simulation result of electromagnetic finite element analysis software ANSYS.
The earth electrode of this DC transmission engineering adopts two circular ring type structures, and embedding manner is horizontal shallow embedding (interior ring is embedded in 3m place under the ground level, and outer shroud is embedded in 3.5m place under the ground level), and the earth electrode structure as shown in Figure 3.
As shown in Figure 2, determining and dividing method of a kind of DC transmission system earth electrode field domain comprises the steps:
(1), determines the field domain of earth electrode according to the circular ring type structure of earth electrode; Earth electrode is included in the field domain, and field domain is a cylinder, and cylindrical height and radius are respectively 100km and 20km, and cylindrical end face is a ground level, and the axis of earth electrode overlaps with cylindrical axis;
On the whole, calculating the field domain scope should be corresponding with electrode shape.When determining to calculate the scope of field domain, generally with horizontal direction at a distance, depth direction is considered as zero potential than the current potential of depths, is the field domain bounds herein.The field domain of determining is a right cylinder shape zone, and the cylinder shape of cross section should be identical with electrode shape.Specifically, be example with the circular ring type electrode, can consider to calculate field domain and be set at upright cylindric zone, its shape of cross section and electrode shape are circle, and the center of circle, cylinder cross section overlaps with the center of circle of round loop electrode.Consider that calculating field domain wants enough far away in the horizontal direction, want enough dark in vertical direction, could make the field domain edge, be close to zero current potential away from electrode.So for the cylindric calculating field domain of circular ring type electrode, desirable radius 20km, calculate in the zone of degree of depth 100km.
(2) according to the circular ring type structure of earth electrode, employing fan-segmentation method is carried out three-dimensional segmentation to the field domain of earth electrode, and concrete steps are as follows:
1) setting up with the cylinder end face center of circle is initial point, and the vertical ground direction is the cylindrical-coordinate system of z direction;
2) cylindrical height and radius are divided into 13 height segments and nine radius segments respectively; Obtain θ to the z of division coefficient, each height segment to the r of division coefficient, each radius segment to division coefficient;
3) according to θ to division coefficient, along the θ direction cylinder average mark is slit into four parts; In each height segment according to the z of correspondence to division coefficient, along the z direction cylinder is averaged and to cut apart; In each radius segment according to the r of correspondence to division coefficient, along the r direction cylinder is averaged and to cut apart, obtain the plurality of sector cell block.
Specifically determining with partitioning parameters of present embodiment earth electrode field domain is as shown in table 1:
Table 1: the definite and partitioning parameters of earth electrode field domain
As from the foregoing, when the earth electrode field domain is cut apart, also should consider the earth electrode shape.The partition principle of generally taking is to adopt fan-segmentation at the circular arc borderline region, adopts rectangle to cut apart in the straight border zone.The ring-like earth electrode of the concrete corresponding circle of present embodiment, its field domain scope are a upright cylinder, cylindric calculating field domain need be divided into some unit in three dimensions.Be the center with centre point on the ground level now, ground vertical depth direction is set up three-dimensional cylindrical-coordinate system for the z direction, and wherein ground level is r, the θ plane of circular cylindrical coordinate, in conjunction with the field domain shape, adopts fan-segmentation comparatively suitable.Cut apart direction and be respectively r direction, θ direction and z direction.Sector element piece after cutting apart as shown in Figure 4.
Calculate the substitutional resistance of sector element respectively from these three directions.Computing formula according to conductor resistance
(ρ is the conductor resistance rate, and l is a conductor length, and S is that cross-sectional area of conductor is long-pending) can derive to fan-shaped piecemeal substitutional resistance, obtains:
Wherein, ρ is soil resistivity (as shown in table 3), r
1And r
2Be respectively the interior outer radius of sector element, θ is the fan angle of sector element, and D is the thickness of sector element.
So far, tried to achieve the substitutional resistance of sector element in r direction, θ direction and z direction, then the resistance that is connected of this sector element and adjacent cells is counterparty's 1/2 of substitutional resistance that makes progress, as shown in Figure 5.
And then, calculate grounding electrode electric current field correlated results (as shown in table 4) according to earth electrode field domain relevant parameter (as shown in table 2).
Table 2: earth electrode field domain relevant parameter
Table 3: earth electrode field domain soil resistivity data
Table 4: grounding electrode electric current field result of calculation
By table 4 result as seen, adopt present embodiment to determine earth electrode field domain scope and partitioning scheme, form and the earth electrode current field to be carried out result calculated behind the resistor network and ANSYS simulation result deviation is less, in 3%, verified the correctness of present embodiment field domain method of determining range and field domain partitioning scheme thus; Compare by grounding electrode electric current field result definite with traditional earth electrode field domain scope and that dividing method calculates, can find than conventional method, the computational accuracy of present embodiment has obtained obvious lifting, and, step voltage maximum and face overflow density calculation value all in the limits of engineering discipline, meet the engineering design requirement.Therefore, the field domain scope of present embodiment determines that method and field domain partitioning scheme are a kind of high accuracy, and is simple to operate, and the direct current transportation earth electrode field domain with broad applicability determines method and field domain partitioning scheme, in actual engineering using value arranged.
Claims (5)
1. determining and dividing method of a DC transmission system earth electrode field domain comprises the steps:
(1), determines the field domain of earth electrode according to the shape of earth electrode; Described earth electrode is included in the field domain, and described field domain is a straight cylinder, and the end face of straight cylinder is a ground level, and the axis of earth electrode overlaps with the axis of straight cylinder;
(2) according to the shape of earth electrode, employing fan-segmentation method or rectangle split plot design are carried out three-dimensional segmentation to the field domain of earth electrode, obtain several cell blocks.
2. the definite and dividing method of DC transmission system earth electrode field domain according to claim 1, it is characterized in that: the height of described field domain is 100km; Described earth electrode be shaped as circular ring type or star-like, the cross section of its field domain is circular, radius is 20km; Described earth electrode be shaped as linear pattern, the cross section of its field domain is a square, the length of side is 40km; Described earth electrode be shaped as racetrack, the cross section of its field domain is a runway shape, the radius of runway shape two ends semicircle is 20km, the straight way length of runway shape is the straight way length of racetrack earth electrode.
3. determining and dividing method of DC transmission system earth electrode field domain according to claim 1 is characterized in that: described earth electrode be shaped as circular ring type or star-like, adopt the fan-segmentation method that its field domain is carried out three-dimensional segmentation; Described earth electrode be shaped as linear pattern, adopt the rectangle split plot design that its field domain is carried out three-dimensional segmentation; Described earth electrode be shaped as racetrack, adopt fan-segmentation method and rectangle split plot design that its field domain is carried out three-dimensional segmentation.
4. the definite and dividing method of DC transmission system earth electrode field domain according to claim 1, it is characterized in that: described fan-segmentation method comprises the steps:
(1) setting up with the cylinder or the semicylinder end face center of circle is initial point, and the vertical ground direction is the cylindrical-coordinate system of z direction;
(2) height and the radius with cylinder or semicylinder is divided into several height segment and radius segments respectively; Obtain θ to the z of division coefficient, each height segment to the r of division coefficient, each radius segment to division coefficient;
(3) according to θ to division coefficient, along the θ direction cylinder or semicylinder are averaged and to cut apart; In each height segment according to the z of correspondence to division coefficient, along the z direction cylinder or semicylinder are averaged and to cut apart; In each radius segment according to the r of correspondence to division coefficient, along the r direction cylinder or semicylinder are averaged and to cut apart, obtain the plurality of sector cell block.
5. the definite and dividing method of DC transmission system earth electrode field domain according to claim 1, it is characterized in that: described rectangle split plot design comprises the steps:
(1) setting up with cuboid end face center is initial point, and cuboid end face long side direction is the x direction, and the vertical ground direction is the three-dimensional system of coordinate of z direction;
(2) with length, the width of cuboid be divided into several length of interval sections, width segment and height segment highly respectively; The x that obtains each length of interval section to the y of division coefficient, each width segment to the z of division coefficient, each height segment to division coefficient;
(3) in each length of interval section according to the x of correspondence to division coefficient, along the x direction cuboid is averaged and to cut apart; In each width segment according to the y of correspondence to division coefficient, along the y direction cuboid is averaged and to cut apart; In each height segment according to the z of correspondence to division coefficient, along the z direction cuboid is averaged and to cut apart, obtain several rectangular element pieces.
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| CN103593523A (en) * | 2013-11-12 | 2014-02-19 | 国网上海市电力公司 | Finite element theory based direct current magnetic bias suppression method under condition of multiple direct-current falling points |
| CN104201664A (en) * | 2014-09-17 | 2014-12-10 | 国家电网公司 | Distributed grounding electrode design method for high-voltage direct-current transmission system |
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Application publication date: 20111019 |