CN112865069A - Disconnection combination selection method for limiting short-circuit current of power grid - Google Patents

Disconnection combination selection method for limiting short-circuit current of power grid Download PDF

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CN112865069A
CN112865069A CN202010683400.2A CN202010683400A CN112865069A CN 112865069 A CN112865069 A CN 112865069A CN 202010683400 A CN202010683400 A CN 202010683400A CN 112865069 A CN112865069 A CN 112865069A
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circuit current
station
power grid
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CN112865069B (en
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张再驰
王卫
吴昊
王海云
董晋阳
宋方方
陈茜
张志坚
黄立华
张文朝
王腾飞
张雨璇
杨莉萍
汪伟
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Taiyuan University of Technology
Beijing Kedong Electric Power Control System Co Ltd
State Grid Beijing Electric Power Co Ltd
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Taiyuan University of Technology
Beijing Kedong Electric Power Control System Co Ltd
State Grid Beijing Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

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Abstract

The invention discloses a disconnection combination selection method for limiting short-circuit current of a power grid, which is used for calculating the short-circuit current I of each station in the power grid in an initial statej(ii) a Calculating a weight factor alpha according to the short-circuit current of the initial state of each stationj(ii) a Calculating the superposed value eta 'of the short-circuit current sensitivity coefficients under different broken line combinations in the power grid'sum(ii) a Eta 'is selected'sumThe maximum combination of broken lines is the recommended combination scheme of broken lines. The disconnection combination selection method for limiting the short-circuit current of the power grid improves the simplicity of practical application on the premise of ensuring the scientific and reasonable selection method, and can provide a technical support for the power grid operation staff to determine the power grid operation mode.

Description

Disconnection combination selection method for limiting short-circuit current of power grid
Technical Field
The invention relates to a disconnection combination selection method for limiting short-circuit current of a power grid, and belongs to the technical field of power grid control of power systems.
Background
With the gradual construction of extra-high voltage and direct current transmission projects and the continuous increase of loads, the scale of a power grid is continuously enlarged, the power grid is more and more closely connected, the electrical distance of a system is rapidly reduced, the phenomenon that the short-circuit current of the power grid exceeds the standard is increasingly prominent, and the safe and stable operation and planning construction of the power grid are severely restricted.
The current short circuit limiting measures mainly include reasonable adjustment of grid structure, additional arrangement of series reactors, optimization of power supply access mode, improvement of breaker breaking capacity and the like. The grid structure is reasonably adjusted, so that the fundamental problem that short-circuit current exceeds the standard due to the fact that the electrical distance of a system is too small is solved, and meanwhile, compared with other short-circuit current limiting measures, the grid structure has better economical efficiency, and is an economical and effective grid short-circuit current limiting measure which is preferentially recommended at present.
After the extra-high voltage power grid forms a strong grid frame, conditions are created for optimizing the structure and operating in a subarea mode of the low-voltage-level power grid. When the grid structure is adjusted, in order to guarantee the power supply reliability, a partition operation mode is formed by disconnecting a plurality of lines, the compactness degree of the grid structure of the power grid is reduced, and the effect of limiting the short-circuit current of the power grid is achieved. When the line is disconnected, the limiting effect of different line disconnection combinations on the short-circuit current is different, and how to select a proper line disconnection combination according to the actual situation of the power grid is a problem to be solved urgently.
Disclosure of Invention
The purpose is as follows: the invention provides a method for selecting a line breaking combination for limiting the short-circuit current of a power grid, aiming at solving the problems that when the power grid line is broken, the limiting effect of different line breaking combinations on the short-circuit current is different, and how to select the line breaking combination is provided.
The technical scheme is as follows: in order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a disconnection combination selection method for limiting short-circuit current of a power grid comprises the following steps:
calculating the short-circuit current I of each station in the power grid in the initial statej；
Calculating a weight factor alpha according to the short-circuit current of the initial state of each stationj；
Calculating the superposed value eta 'of the short-circuit current sensitivity coefficients under different broken line combinations in the power grid'sum；
Eta 'is selected'sumThe maximum combination of broken lines is the recommended combination scheme of broken lines.
Preferably, the weighting factor α isjThe acquisition steps are as follows:
2.1 construction of the decision matrix Xn×nThe formula is as follows:
Figure BDA0002585146060000021
wherein site i is scaled by x relative to site jijThen the scale of site j relative to site i is 1/xijN represents the number of power grid stations, i and j are respectively 1, 2 and 3 … n; the criteria for the scale are as follows:
criterion one is as follows: the scale of the first-level site relative to the other sites of the same level is the highest scale value, and the scale of the first-level site relative to the other sites of the same level is 1;
criterion two: the second-level station is a third high scale value relative to the scale of the third-level station, is a second high scale value relative to the scale of the fourth-level station, and is also two stations of the second level, if the short-circuit current difference is greater than or equal to the first difference, the station with large short-circuit current is a fourth high scale value relative to the scale of the station with small short-circuit current, and if the short-circuit current difference is smaller than the first difference, the scale is 1;
criterion three: the third-level station is scaled to a third-high scale value relative to the fourth-level station, and is also scaled to two stations of a third level, if the difference value of the short-circuit current is greater than or equal to the first difference value, the station with the large short-circuit current is scaled to a fourth-high scale value relative to the station with the small short-circuit current, and if the difference value of the short-circuit current is less than the first difference value, the scale is 1;
criterion four: if the difference value of the short-circuit current is larger than or equal to the first difference value, the scale of the station with large short-circuit current is a fourth high scale value relative to the station with small short-circuit current, and if the difference value of the short-circuit current is smaller than the first difference value, the scale is 1;
the numerical values of the highest scale value, the second highest scale value, the third highest scale value and the fourth highest scale value are reduced in sequence;
the first-level station is a station with the short-circuit current larger than a first threshold value; the second-level station is a station with the station short-circuit current larger than or equal to a second threshold and smaller than the first threshold; the third-level station is a station with the short-circuit current larger than or equal to a third threshold and smaller than a second threshold; the fourth-level station is a station with the short-circuit current smaller than a third threshold value;
2.2 solving the decision matrix Xn×nMaximum characteristic root λ ofmaxAnd its corresponding feature vector β ═ b1,b2,…,bi,…,bn) When the consistency ratio CR is<When the fourth threshold value is reached, the consistency test is passed;
Figure BDA0002585146060000031
in the formula, RI is a random consistency coefficient;
Figure BDA0002585146060000032
in the formula, n represents the number of power grid sites;
2.3 normalizing each element in the characteristic vector beta to obtain the corresponding weight factor alphaj
Figure BDA0002585146060000033
Preferably, when the consistency ratio CR is larger than or equal to the fourth threshold, the consistency check is not passed, and the judgment matrix X is adjusted by modifying the assigned numbers of each scale value in the judgment criterionn×n。
Preferably, the sum η 'of the short-circuit current sensitivity coefficients'sumThe calculation formula is as follows:
Figure BDA0002585146060000034
in the formula, N is the total number of sites;
Figure BDA0002585146060000035
in the formula Ij、I′jRespectively, short-circuit currents of sites j before and after the open circuit.
Preferably, the numerical values of the highest scale value, the second highest scale value, the third highest scale value and the fourth highest scale value are 7, 5, 3 and 2 in sequence.
Preferably, the first threshold is a site rated breaking capacity of SNThe second threshold is SN-4, the third threshold being SN-10。
Preferably, the first difference is 2 kA.
Has the advantages that: according to the method for selecting the broken line combination for limiting the short-circuit current of the power grid, provided by the invention, the weight factors of the sensitivity coefficients of the short-circuit currents of different stations are calculated based on the judgment matrix, different broken line combinations for limiting the short-circuit current in the power grid are quantitatively sequenced, and then the broken line combination with the best short-circuit current limiting effect is determined, so that the simplicity of practical application is improved on the premise of ensuring the scientific and reasonable selection method, and a technical support can be provided for power grid operation workers to determine the power grid operation mode.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a schematic diagram of a grid structure in an embodiment.
Detailed Description
The present invention will be further described with reference to the following examples.
As shown in fig. 1, a disconnection combination selection method for limiting a short-circuit current of a power grid includes the following steps:
(1) calculating the short-circuit current sensitivity coefficient of each station
For a certain station j in the power grid, the short-circuit current sensitivity coefficient calculation formula is as follows:
Figure BDA0002585146060000041
in the formula Ij、I′jShort-circuit currents of a station j before and after the circuit is disconnected respectively; etajShort-circuit current sensitivity coefficient, η, for site jjThe larger the value of (b) is, the more effective the short-circuit current limitation of the station j is in the case of opening the line.
Due to the close electrical connection of the system, the short-circuit current of a plurality of stations of a regional power grid exceeds the standard or is close to the rated breaking capacity of a breaker. Different grid structure structures can be formed by different combination of the open and the broken lines, so that the influence degree on the short-circuit current of each station is different. When the combination of the open circuit and the closed circuit is selected, the sought qualitative goal is to make the overall short circuit current limiting effect more ideal, the goal can be quantitatively characterized by the superposed value of the sensitivity coefficients of the short circuit currents of all stations, of which the short circuit currents are greater than the threshold value, corresponding to each combination of the open circuit and the closed circuit in the researched area, and the calculation formula is as follows:
Figure BDA0002585146060000042
in the formula etasumAdding the sensitivity coefficient of the short-circuit current to obtain a superposition value; n is the total number of sites; etajThe short-circuit current sensitivity coefficient of the jth station. Each broken line combination has a corresponding short-circuit current sensitivity coefficient superposition value, and theoretically, the larger the superposition value is, the better the short-circuit current limiting effect is. However, in the actually-operated power grid, the short-circuit current of each station exceeds the standard in different degrees, and the short-circuit current exceeds the rated value of the breakerThe on-off capacity and the short-circuit current are close to the rated on-off capacity of the circuit breaker but still have certain safety margin and the like. The short-circuit current of a station is limited to be lower than the rated breaking capacity of the breaker by priority, and the short-circuit current of other stations is reduced to the maximum extent by priority, so that the safety margin is improved. In contrast, the short-circuit current limiting effect of different broken line combinations under different conditions is reflected by introducing a weighting factor to weight the sensitivity coefficient of the short-circuit current, and the calculation formula is as follows:
Figure BDA0002585146060000051
eta 'of'sumFor the superimposed value of the short-circuit current sensitivity coefficient after considering the weighting factor, alphajIs a weighting factor of the short-circuit current sensitivity coefficient of the jth station. According to the previous analysis, the site short-circuit current exceeding the rated breaking capacity of the breaker needs to be limited by priority, so that the higher the relative importance degree is, a larger weight factor should be set; the relative importance degree of the station short-circuit current which is lower than the rated breaking capacity of the breaker and has a certain safety margin is reduced in sequence, and the set weight factors are reduced in sequence. Finally, η'sumThe larger the line disconnection combination, the better the whole effect of limiting the short-circuit current, so the method is a recommended line disconnection combination scheme.
(2) Calculating a short circuit current sensitivity coefficient weight factor
In the invention, the target to be achieved is that the short-circuit current limiting effect is best, namely the superposition value of the sensitivity coefficient of the short-circuit current in the formula (3) is minimum. The site short-circuit current sensitivity coefficient in the formula (3) can be obtained by the formula (1); weighting factor alpha of short-circuit current sensitivity coefficient of jth stationjIt needs to be calculated by constructing a decision matrix. The specific calculation steps are as follows:
1) constructing a decision matrix
When the judgment matrix is constructed, all factors are not put together for comparison, but a method of comparing every two factors is adopted, so that the difficulty of comparing the factors with different properties is reduced as much as possible, and the accuracy of the final result is improved. When the relative importance degree of the two stations is judged according to the short-circuit current of the stations, the scale value is adopted to quantify the relative importance degree, and the larger the scale value is, the higher the relative importance degree is.
When the scale value is determined, firstly, the site is divided into four grades according to the short-circuit current of the site: the first grade is a station with over-standard short-circuit current, and the rated breaking capacity of the station of the power grid is SN(unit: kA, the same applies hereinafter) so that the short-circuit current is greater than a first threshold value, e.g., SNThe station(s) of (1) is marked as a first-level station; the second level is that the site short-circuit current is greater than or equal to a second threshold, e.g., (S)N-4), less than a first threshold, such as SNAlthough the short-circuit current of the station at the same level does not exceed the standard, the short-circuit current of the station at the same level is close to the rated cut-off capacity, and the hidden danger of exceeding the standard exists in the expansion of a power grid; the third level is that the site short-circuit current is greater than or equal to a third threshold, e.g., (S)N-10), less than a second threshold, such as (S)N4), the station short-circuit current under the level has a certain safety margin and is low in overproof possibility; the fourth level is that the site short-circuit current is less than the third threshold, e.g., (S)N10), the station short circuit current at that level has a large safety margin, which can be considered as having no possibility of exceeding the standard. The specific judgment criteria are as follows:
criterion one is as follows: the first level site is scaled to 7 relative to other levels of sites, and the first level site is scaled to 1 relative to other levels of sites of the same level;
criterion two: the scale of the second-level station is 3 relative to the third-level station, the scale of the fourth-level station is 5, and the second-level station is also two stations of the second level, if the short-circuit current difference is greater than or equal to the first difference, such as 2kA, the scale of the station with large short-circuit current is 2 relative to the scale of the station with small short-circuit current, and if the short-circuit current difference is less than the first difference, such as 2kA, the scale is 1;
criterion three: the scale of the third-level station is 3 relative to the scale of the fourth-level station, and is also two stations of the third level, if the difference value of the short-circuit current is greater than or equal to the first difference value, such as 2kA, the scale of the station with large short-circuit current is 2 relative to the scale of the station with small short-circuit current, and if the difference value of the short-circuit current is less than the first difference value, such as 2kA, the scale is 1;
criterion four: similarly, for two stations in the fourth level, if the short-circuit current difference is greater than or equal to the first difference, for example, 2kA, the scale of the station with the large short-circuit current is 2 relative to the scale of the station with the small short-circuit current, and if the short-circuit current difference is smaller than the first difference, for example, 2kA, the scale is 1.
Based on the above judgment criteria, a judgment matrix X can be obtainedn×n：
Figure BDA0002585146060000061
Wherein site i is scaled by x relative to site jijThen the scale of site j relative to site i is 1/xijN represents the number of grid sites, i and j are 1, 2 and 3 … n respectively.
2) Consistency check
Determining a decision matrix Xn×nMaximum characteristic root λ ofmaxAnd its corresponding feature vector β ═ b1,b2,…,bi,…,bn) And carrying out consistency check, and calculating a consistency index CI as follows:
Figure BDA0002585146060000062
where n represents the number of grid sites.
If CI is 0, then there is complete consistency; the larger the CI, the more serious the inconsistency. To quantify the degree of characterization consistency, a consistency ratio CR is introduced:
Figure BDA0002585146060000071
in the formula, RI is a random consistency coefficient, and is generally regarded as a consistency ratio CR<And a fourth threshold, such as 0.1, judging that the inconsistency degree of the matrix is within an allowable range and has satisfactory consistency,pass the consistency check. Otherwise, adjusting the scale in the judgment criterion, and reconstructing the judgment matrix Xn×n. The adjusted judgment criteria are as follows:
criterion one is as follows: the first-level site is rated 5 relative to other sites of the same level, and the first-level site is rated 1 relative to other sites of the same level;
criterion two: the scale of the second-level station is 3 relative to the third-level station, the scale of the fourth-level station is 4, and the second-level station is also two stations of the second level, if the short-circuit current difference is greater than or equal to the first difference, such as 2kA, the scale of the station with large short-circuit current is 2 relative to the scale of the station with small short-circuit current, and if the short-circuit current difference is less than the first difference, such as 2kA, the scale is 1;
criterion three and criterion four are unchanged.
After passing consistency check, the maximum characteristic root lambda is determinedmaxThe corresponding feature vector β ═ b1,b2,…,bi,…,bn) And (3) carrying out normalization treatment:
Figure BDA0002585146060000072
respectively obtaining weight factors alpha corresponding to the short-circuit current sensitivity coefficients of the n stationsjI and j are 1, 2 and 3 … n respectively.
3) Comparison selection
And calculating the short-circuit current sensitivity coefficient of each station according to a formula (1), calculating the superposition value of the short-circuit current sensitivity coefficients of different disconnection combination modes according to the obtained weighting factor and a formula (3), and obtaining the disconnection combination with the minimum superposition value and the best short-circuit current limiting effect, thereby completing the selection of different disconnection combinations.
Example 1:
taking a 220kV power grid in a certain area as an example, a grid structure of the power grid is shown in fig. 2, wherein a thick solid line represents a 220kV station, and a thin dotted line represents a double-circuit power transmission line. Under the condition of full wiring of a power grid, the short-circuit current of three stations B, C, E exceeds the standard, the short-circuit current of A, F, G, H four stations is close to 50kA, and the level of the short-circuit current in the area is higher as a whole. The grid short circuit current was calculated using the short circuit current calculation program in the PSD power system software kit, with the results shown in table 1:
TABLE 1 calculation of the total grid short-circuit current
Site Short-circuit current (kA)
A 47.797
B 53.499
C 51.978
D 42.517
E 50.529
F 49.873
G 47.518
H 47.862
I 43.194
Through simulation analysis of a power flow program and a short-circuit current calculation program, on the premise of ensuring no equipment overload, two broken line combinations of a broken site C-site E double-circuit line and a broken site A-site B double-circuit line can both play a role in limiting short-circuit current, and the broken line combination selection method provided by the invention is adopted for sequencing:
1) constructing a decision matrix
According to the judgment criterion and the simulation calculation result of the short circuit, a judgment matrix X of the mutual importance degree of the short circuit current sensitivity coefficients of 9 sites is constructed9×9：
Figure BDA0002585146060000091
2) Consistency check
Calculating the judgment matrix X9×9And the corresponding feature vector: lambda [ alpha ]max9.456, the corresponding eigenvector β is (0.0950.56280.56280.0510.56280.13210.0950.0950.051).
In this embodiment, the number of stations is 9, the random uniformity coefficient RI is 1.45, and a table of values of uniformity coefficients for the number of stations from 5 to 9 is shown in table 2.
TABLE 2 table for taking values of random consistency coefficients
n 5 6 7 8 9
RI 1.12 1.24 1.32 1.41 1.45
In the table, n represents the number of sites.
Substituting formula (4) to calculate the consistency index CI:
Figure BDA0002585146060000092
the consistency ratio CR is calculated by substituting equation (5):
Figure BDA0002585146060000093
CR <0.1, by consistency test.
Normalizing each element in the feature vector beta by a formula (6) to obtain a corresponding weight factor alphajIn b with1For example, the following steps are carried out:
Figure BDA0002585146060000101
after normalization
αj＝(0.043 0.255 0.255 0.023 0.255 0.060 0.043 0.043 0.023)。
3) Comparison selection
Short-circuit current of each station for cutting off the C-E double circuit lines and the A-B double circuit lines is respectively calculated by using a short-circuit current calculation program, and the short-circuit current sensitivity coefficient of each station is calculated by substituting a formula (1) by combining the short-circuit current calculation results in the table 1, wherein the calculation results are shown in the table 3:
TABLE 3 results of calculation of site short-circuit current sensitivity coefficients
Figure BDA0002585146060000102
Then the weighting factor alpha is calculatedj) Substituting the calculation result of the site short-circuit current sensitivity coefficient into a formula (3), and respectively calculating the superposition value of the short-circuit current sensitivity coefficients of two broken line combinations:
Figure BDA0002585146060000111
Figure BDA0002585146060000112
η′sum(C-E)＞η′sum(A-B)therefore, the effect of limiting the short-circuit current when the C-E double-circuit line is disconnected is better than that when the A-B double-circuit line is disconnected, and the recommended disconnection combination scheme is to disconnect the C-site E double-circuit line.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (7)

1. A disconnection combination selection method for limiting short-circuit current of a power grid is characterized by comprising the following steps: the method comprises the following steps:
calculating the short-circuit current I of each station in the power grid in the initial statej；
Calculating a weight factor alpha according to the short-circuit current of the initial state of each stationj；
Calculating the superposed value eta 'of the short-circuit current sensitivity coefficients under different broken line combinations in the power grid'sum；
Eta 'is selected'sumThe maximum combination of broken lines is the recommended combination scheme of broken lines.
2. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 1, wherein: the weight factor alphajThe acquisition steps are as follows:
2.1 construction of the decision matrix Xn×nThe formula is as follows:
Figure FDA0002585146050000011
wherein site i is scaled by x relative to site jijThen the scale of site j relative to site i is 1/xijN represents the number of power grid stations, i and j are respectively 1, 2 and 3 … n; the criteria for the scale are as follows:
criterion one is as follows: the scale of the first-level site relative to the other sites of the same level is the highest scale value, and the scale of the first-level site relative to the other sites of the same level is 1;
criterion two: the second-level station is a third high scale value relative to the scale of the third-level station, is a second high scale value relative to the scale of the fourth-level station, and is also two stations of the second level, if the short-circuit current difference is greater than or equal to the first difference, the station with large short-circuit current is a fourth high scale value relative to the scale of the station with small short-circuit current, and if the short-circuit current difference is smaller than the first difference, the scale is 1;
criterion three: the third-level station is scaled to a third-high scale value relative to the fourth-level station, and is also scaled to two stations of a third level, if the difference value of the short-circuit current is greater than or equal to the first difference value, the station with the large short-circuit current is scaled to a fourth-high scale value relative to the station with the small short-circuit current, and if the difference value of the short-circuit current is less than the first difference value, the scale is 1;
criterion four: if the difference value of the short-circuit current is larger than or equal to the first difference value, the scale of the station with large short-circuit current is a fourth high scale value relative to the station with small short-circuit current, and if the difference value of the short-circuit current is smaller than the first difference value, the scale is 1;
the numerical values of the highest scale value, the second highest scale value, the third highest scale value and the fourth highest scale value are reduced in sequence;
the first-level station is a station with the short-circuit current larger than a first threshold value; the second-level station is a station with the station short-circuit current larger than or equal to a second threshold and smaller than the first threshold; the third-level station is a station with the short-circuit current larger than or equal to a third threshold and smaller than a second threshold; the fourth-level station is a station with the short-circuit current smaller than a third threshold value;
2.2 solving the decision matrix Xn×nMaximum characteristic root λ ofmaxAnd its corresponding feature vector β ═ b1,b2,…,bi,…,bn) When the consistency ratio CR is<When the fourth threshold value is reached, the consistency test is passed;
Figure FDA0002585146050000021
in the formula, RI is a random consistency coefficient;
Figure FDA0002585146050000022
in the formula, n represents the number of power grid sites;
2.3 normalizing each element in the characteristic vector beta to obtain the corresponding weight factor alphaj
Figure FDA0002585146050000023
3. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 2, wherein: when the consistency ratio CR is larger than or equal to the fourth threshold value, the consistency check is not passed, and the scales in the judgment criterion are modifiedAdjusting the decision matrix X by assigning values to the valuesn×n。
4. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 2, wherein: the superposition value eta of the short-circuit current sensitivity coefficient'sumThe calculation formula is as follows:
Figure FDA0002585146050000024
in the formula, N is the total number of sites;
Figure FDA0002585146050000025
in the formula Ij、I′jRespectively, short-circuit currents of sites j before and after the open circuit.
5. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 2, wherein: and the numerical values of the highest scale value, the second highest scale value, the third highest scale value and the fourth highest scale value are 7, 5, 3 and 2 in sequence.
6. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 2, wherein: the first threshold value is S of rated cut-off capacity of a stationNThe second threshold is SN-4, the third threshold being SN-10。
7. The method for selecting the disconnection combination for limiting the short-circuit current of the power grid according to claim 2, wherein: the first difference is 2 kA.
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