Background
With the steady advance of the strategy of 'west-east power transmission, south-north mutual supply and national networking' of a power system in China, high-voltage direct-current power transmission systems are increasingly applied to power grids. Compared with high-voltage alternating-current transmission, high-voltage direct-current transmission has the advantages of large transmission capacity, long distance, small loss and the like, and the problem of stability of synchronous operation does not exist, so that the high-voltage direct-current transmission is widely applied to large-capacity long-distance transmission.
The converter station is a junction of a high-voltage direct-current transmission project, plays a key role in the whole direct-current transmission project, alternating-current equipment and direct-current equipment in the station are expensive, overvoltage protection on main equipment cannot be achieved, the types of the lightning arresters used for the overvoltage protection in the converter station are more than those of an alternating-current system, and the converter station mainly comprises a converter valve lightning arrester, a direct-current bus lightning arrester, a neutral bus lightning arrester, a direct-current filter lightning arrester, an alternating-current filter lightning arrester, a smoothing reactor lightning arrester and the like. The most complicated operating condition is the neutral bus arrester on the rectifying side.
The neutral bus arrester is installed on a neutral bus of a converter station, the voltage is low when a direct current system operates normally, the voltage is zero when a bipolar ground is in balanced operation, and large overvoltage and huge energy are easily generated on the neutral bus when a line fails or certain operations occur. To protect the neutral bus-bar zone equipment from overvoltage damage, the arrester needs to have the capability of absorbing up to tens of MJ of energy. The arrester is generally composed of multiple columns of arresters connected in parallel, limited by the manufacturing technology of the arrester. Taking a stream luodian direct-current transmission project as an example, the number of single-loop neutral bus lightning arresters in the rectifying-side Anzhi converter station is as many as 23, each lightning arrester is in a 4-column valve plate parallel structure, and the designed energy tolerance capacity of each lightning arrester is 1.44 MJ.
The ideal operation condition of the lightning arrester with the multi-column parallel structure is the energy generated when each column sharing system is impacted, but if the current sharing characteristic of the lightning arrester is poor or the local performance is deteriorated, the individual lightning arrester unit absorbs the energy exceeding the tolerance level of the lightning arrester unit, so that the breakdown fault of the lightning arrester is caused, the direct current system is stopped, and the great economic loss is caused. In the 2014 process of converting an extra-high voltage Yibin convertor station into a metal return wire from the ground, a single lightning arrester of a metal return wire change-over switch is broken down (the whole group of 26 lightning arresters are connected in parallel), so that the switch is failed to be opened, and a direct-current system is stopped; in the process of converting the ground into the metal return wire, in 2014, a single lightning arrester of a metal return wire change-over switch is broken down (11 whole groups are connected in parallel), so that direct current locking is caused; in 2016, when a Lingzhou converter station is subjected to a short circuit test in a direct-current line near region, a single neutral bus arrester group breaks down (the whole group of 24 arrester groups is connected in parallel), so that direct-current blocking is caused.
The current shunt test and the uneven coefficient calculation of the multi-column parallel lightning arrester at home and abroad are mostly based on 2-column or 4-column parallel connection, and are matched based on the reference voltage values of the resistance cards, so that the reference voltages of the combined lightning arresters on the columns are as consistent as possible, and the uneven coefficient of the current meets the requirement that the standard is less than 1.1. And most lightning arrester products are in compliance with the requirement when being shipped out of the factory. However, according to accident case analysis in recent years, the requirement is not suitable for a large-scale multi-column parallel lightning arrester group.
Hushui et al propose a method for measuring the uneven current distribution coefficient of a multi-column parallel resistance card column, which is limited by the capability of current impact test equipment, and cannot simultaneously measure the uneven current distribution coefficient of dozens of columns or even hundreds of columns of resistance card columns, so that the arrester columns need to be tested in groups. And provides a large-scale resistor sheet matching method based on reference voltage arrangement and exchange. Zhang et al developed a 7-column parallel experiment for the lightning arrester in actual operation on site, and simulated aging of single-column characteristics by reducing the resistance card. The result shows that the larger the variation of the reference voltage of the single column is, the closer the overall reference voltage is to the variation value of the reference voltage of the single column, and the phenomenon that the number of the parallel columns is smaller is more obvious. Therefore, the voltage-current characteristic change of a part of columns in a large-scale multi-column parallel lightning arrester group can be estimated to be difficult to detect.
Disclosure of Invention
The invention provides a multi-column parallel arrester group matching method and device, which can solve the technical problem of low reliability of the existing resistor disc matching method.
In order to achieve the purpose, the invention adopts the following technical scheme:
a multi-column parallel connection lightning arrester group homoenergetic matching method comprises the following steps:
s100, selecting parameter requirements of the lightning arrester group and resistance cards, and determining the number of each column of the lightning arrester and the number of parallel columns;
s200, determining current waveforms of all columns of the lightning arrester group at the position, calculating the energy absorption of each resistance card under the current waveforms through fitting, and rejecting the resistance cards with large energy absorption deviation;
s300, arranging the resistance cards into a column, generating a serial number matrix, and directly adding volt-ampere characteristic points of the resistance cards in one column to obtain the volt-ampere characteristic of the whole column;
s400, performing exponential function fitting on the volt-ampere characteristics of each column, and calculating the current flowing through each column according to the integral residual voltage waveform of the lightning arrester group;
and S500, calculating voltage waveform born by each resistance card according to the current-voltage characteristic fitting function of the resistance card, and then calculating the energy absorbed by the resistance card.
S600, iteratively adjusting the positions of the resistance cards according to the energy absorption matrix, and exchanging the positions of the resistance card with the minimum energy absorbed by the column with the maximum current and the position of the resistance card with the maximum energy absorbed by the column with the minimum current, so that the static volt-ampere characteristic curves of the columns with the maximum current are closer, namely the current values flowing under the same voltage are closer. The more iterations, the more uniform the energy distribution.
Further, the S400 includes:
by the function U-A × Iα+ B, performing volt-ampere characteristic fitting calculation on the resistance card to obtain a current waveform flowing through each column lightning arrester;
wherein U is the voltage value of the arrester, I is the current value of the arrester, alpha is the nonlinear coefficient, A, B is the coefficient.
Further, in S500, the absorbed energy of the resistive sheet is calculated, and the calculation formula is as follows:
W=∫U(t)×I(t)dt;
wherein W is the absorbed energy of the resistive sheet, U is the voltage value of the resistive sheet, I is the current value of the resistive sheet, and t is time.
On the other hand, the invention also discloses a device for matching the multi-column parallel arrester group, which comprises the following units:
the lightning arrester determining unit is used for selecting the parameter requirements of the lightning arrester group and the resistance cards and determining the number of each column and the number of parallel columns of the lightning arrester;
the resistance card screening unit is used for determining current waveforms of all columns of the lightning arrester group, calculating the energy absorption of each resistance card under the current waveforms through fitting, and rejecting the resistance cards with large energy absorption deviation;
the voltage-current characteristic generating unit is used for arranging the residual resistor pieces into a column and generating a serial number matrix, and directly adding voltage-current characteristic points of the resistor pieces in one column to obtain the voltage-current characteristic of the whole column;
the lightning arrester current calculation unit is used for performing exponential function fitting on the volt-ampere characteristics of each column and calculating the current flowing through each column according to the integral residual voltage waveform of the lightning arrester group;
the resistance card absorbed energy calculation unit is used for calculating voltage waveforms born by the resistance cards according to the resistance sub-self volt-ampere characteristic fitting function and then calculating the absorbed energy of the resistance cards;
and the resistance sheet adjusting unit is used for iteratively adjusting the position of the resistance sheet according to the energy absorption matrix, exchanging the resistance sheet with the minimum absorption energy of the current maximum column with the resistance sheet with the maximum absorption energy of the current minimum column, iteratively calculating and repeating the steps.
The invention also provides a computer-readable storage medium, in which a computer program is stored, which computer program, when being executed by a processor, is adapted to carry out the above-mentioned method steps.
According to the technical scheme, the method comprises the steps of calculating the distribution of the absorbed energy of the resistance card in the overvoltage limiting process of the arrester group, and carrying out iterative calculation at the positions of the screened and exchanged resistance cards to obtain the result of the most uniform distribution of the absorbed energy of the resistance card; then, describing a matching position in a resistor disc matching process by using a resistor disc position matrix, generating an initial random matrix before matching, outputting a resistor disc matching matrix after an optimal solution is achieved through multiple iterative calculations, and assembling resistor discs according to matrix serial numbers; obtaining a volt-ampere characteristic equation through static volt-ampere characteristic fitting of the resistance cards, and calculating the energy absorbed by each resistance card in the process of limiting overvoltage; the lightning arresters at different positions face different overvoltage working conditions, the method can calculate and match groups aiming at the most severe working conditions of the lightning arrester groups at different positions, and can achieve the theoretically optimal matching group; the situation of the energy absorption values of all the resistance cards in the arrester group is described through the resistance card absorbed energy distribution color block matrix, so that the current shunting situation and the energy absorption difference of the resistance cards can be visually seen. The group matching algorithm provided by the invention is an effective way for improving the reliability of the multi-column parallel arrester group, and has very important research value.
Therefore, the method for matching the multi-column parallel arrester group has the following beneficial effects:
1. the resistor disc matching algorithm based on the absorbed energy balance is put forward for the first time, and is suitable for large-scale multi-column parallel connection lightning arrester matching design.
2. Different positions of the lightning arrester groups face different working conditions, the algorithm can be used for matching the overvoltage waveforms of different lightning arrester groups, and the operation reliability of the lightning arrester groups is effectively improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.
As shown in fig. 1, the method for matching groups of multi-column parallel lightning arresters in this embodiment includes the following steps:
s100, selecting parameter requirements of the lightning arrester group and resistance cards, and determining the number of lightning arresters per column and the number of parallel columns;
s200, determining current waveforms of columns of the lightning arrester group at a set position, calculating the energy absorption of each resistance card under the current waveforms through fitting, and rejecting the resistance cards with large energy absorption deviation;
s300, arranging the resistance cards into a column, generating a serial number matrix, and directly adding volt-ampere characteristic points of the resistance cards in one column to obtain the volt-ampere characteristic of the whole column;
s400, performing exponential function fitting on the volt-ampere characteristics of each column, and calculating the current flowing through each column according to the integral residual voltage waveform of the lightning arrester group;
s500, calculating voltage waveforms borne by the resistance cards according to the current-voltage characteristic fitting functions of the resistance cards, and then calculating the energy absorbed by the resistance cards;
s600, iteratively adjusting the positions of the resistance cards according to the energy absorption matrix, and exchanging the positions of the resistance cards with the minimum absorption energy of the current maximum column with the positions of the resistance cards with the maximum absorption energy of the current minimum column.
Wherein S100 can be interpreted as:
the lightning arrester reference voltage V1 and the withstand energy requirement W1 are determined, the specification of a proper resistance sheet is selected, the resistance sheet reference voltage V2 and the single-chip withstand energy W2 are determined, the number n of the single-column series resistance sheets is V1/V2, and the number m of the parallel columns is W2/(W1 n).
In S400, the pass function U is a × Iα+ B, performing volt-ampere characteristic fitting calculation on the resistance card to obtain a current waveform flowing through each column lightning arrester;
wherein, U is the voltage value of arrester, I is the current value of arrester, and alpha is the nonlinear coefficient, and A, B is the coefficient.
Calculating the absorbed energy of the resistor disc in S500, wherein the calculation formula is W ═ U (t) multiplied by I (t) dt;
wherein W is the absorbed energy of the resistive sheet, U is the voltage value of the resistive sheet, I is the current value of the resistive sheet, and t is time.
The following are exemplified:
(1) according to the reference voltage value of the EM lightning arrester and the reference voltage of the resistance cards, the EM lightning arrester is drawn up, 54 resistance cards are connected in series with each column of the EM lightning arrester, and calculation is carried out on 64 columns and 3456 resistance cards which are connected in parallel according to current estimation and redundancy design.
(2) Arranging the volt-ampere characteristics of the residual 3456 resistive sheets at random according to numbers 0001-3456, and establishing a sequence serial number grouping matrix; as shown in fig. 2, the selected EM type lightning arrester group adopts 64 columns connected in parallel, each column is connected with 54 resistance sheets in series, and the resistance sheets are randomly arranged and endowed with position serial numbers during initial grouping.
(3) Importing static volt-ampere characteristic data of the resistance card according to the grouping and corresponding to the serial number; calculating static volt-ampere characteristics of each column;
(4) leading in an overvoltage waveform of the lightning arrester group obtained by system simulation calculation when the system fails, and calculating current flowing through each column; as shown in fig. 3, the overvoltage waveform of the arrester group is obtained through system simulation or actual waveform recording, and the current flowing through each column is calculated after the volt-ampere characteristic of each column is obtained through calculation;
(5) and calculating the voltage waveform born by each resistance card according to the volt-ampere characteristic fitting result of each resistance card and the current waveform flowing through the resistance card. The energy absorbed by the resistance card can be calculated, the result of the energy absorbed by each resistance card is calculated for the first time is shown in fig. 4, each color block in the graph represents one resistance card, each column represents one lightning arrester, the color represents the value of the energy absorbed by the resistance card, and the calculation result in the graph is as follows: the average value of the current flowing through each column at this time was 116.18A, the maximum value was 129.9A (m ═ 2) in the 2 nd column, the minimum value was 98.8A (m ═ 50) in the 50 th column, and the current non-uniformity coefficient was 0.315; the average value of the energy absorbed by the resistor slice is 9.023kJ, the maximum value is 10.57kJ (n is 54, m is 2), the minimum value is 7.32kJ (n is 2, m is 50), the energy nonuniformity coefficient is 0.3607, and the lightning arrester absorbs 31.184MJ integrally.
(6) The resistor sheets are adjusted so that the resistor sheet with the largest current column absorbing energy is exchanged with the resistor sheet with the smallest current column absorbing energy, and as shown in the above figure, the resistor sheet with the largest current column absorbing energy is at the position (m is 2, n is 25) and the resistor sheet with the smallest current column absorbing energy is at the position (m is 50, n is 40), so that the quiescent current characteristic curves of the columns in which the two columns are located can be closer, that is, the current value flowing under the same voltage is closer. The more iterations, the more uniform the energy distribution.
(7) When the above steps are iteratively calculated for 10 times, the average value of the current flowing through each column is 116.09A, the maximum value is 122.9A (m is 32) of the 32 th column, the minimum value is 107.4A (m is 35) of the 35 th column, and the current unevenness coefficient is 0.13558; the average value of the absorbed energy of each resistor sheet is 9.0153kJ, the maximum value is 10.02kJ (m is 20, n is 8), the minimum value is 7.86kJ (m is 18, n is 51), and the energy nonuniformity factor is 0.2752.
(8) The current average uniformity factor reached 0.0957<0.1 at 18 iterations, where the current average through each column was 116.06A, the maximum was 121.2A (m 33), the minimum was 110.6A (m 16), and the current uniformity factor was 0.0957; the average absorbed energy of each resistor sheet is 9.0153kJ, the maximum value is 9.96kJ (n is 6, m is 21), the minimum value is 8.13kJ (n is 34, m is 19), and the energy nonuniformity factor is 0.2249.
(9) When the algorithm is iterated for 38 times, the optimal solution is achieved, the position of the resistance card cannot be changed any more, the average value of the current flowing through each column is 116.028A, the maximum value is 17.99A (m is 6), the minimum value is 113.99A (m is 29), and the current unevenness coefficient is 0.0351; the average value of the absorbed energy of the single resistor sheets is 9.0088kJ, the maximum value is 9.6734kJ (n is 19, m is 40), the minimum value is 8.3196kJ (n is 54, m is 44), and the energy distribution is shown in fig. 5;
the current non-uniformity coefficient and the absorbed energy variance during the whole calculation process are shown in fig. 6 and 7.
According to the technical scheme, the method comprises the steps of calculating the distribution of the absorbed energy of the resistance card in the overvoltage limiting process of the arrester group, and carrying out iterative calculation at the positions of the screened and exchanged resistance cards to obtain the result of the most uniform distribution of the absorbed energy of the resistance card; then, describing a matching position in a resistor disc matching process by using a resistor disc position matrix, generating an initial random matrix before matching, outputting a resistor disc matching matrix after an optimal solution is achieved through multiple iterative calculations, and assembling resistor discs according to matrix serial numbers; obtaining a volt-ampere characteristic equation through static volt-ampere characteristic fitting of the resistance cards, and calculating the energy absorbed by each resistance card in the process of limiting overvoltage; the lightning arresters at different positions face different overvoltage working conditions, the method can calculate and match groups aiming at the most severe working conditions of the lightning arrester groups at different positions, and can achieve the theoretically optimal matching group; the situation of the energy absorption values of all the resistance cards in the arrester group is described through the resistance card absorbed energy distribution color block matrix, so that the current shunting situation and the energy absorption difference of the resistance cards can be visually seen. The algorithm of the invention can be used for matching groups according to overvoltage waveforms of different arrester groups, thereby effectively improving the operation reliability of the arrester groups.
The above is the basic logic of the algorithm of the present invention, and the optimization and adjustment can be performed on the basis of the basic logic: the method has the advantages that the change rule that the characteristics of the resistance card are affected by factors such as temperature rise, power frequency aging, impact aging, radial electric field caused by dirt, leakage current heating caused by dampness and the like is considered, the algorithm step is added, and the equivalence of simulation calculation is improved.
On the other hand, the invention also discloses a device for matching the multi-column parallel arrester group, which comprises the following units:
the lightning arrester determining unit is used for selecting the parameter requirements of the lightning arrester group and the resistance cards and determining the number of each column and the number of parallel columns of the lightning arrester;
the resistance card screening unit is used for determining current waveforms of all columns of the lightning arrester group, calculating the energy absorption of each resistance card under the current waveforms through fitting, and rejecting the resistance cards with large energy absorption deviation;
the voltage-current characteristic generating unit is used for arranging the residual resistor pieces into a column and generating a serial number matrix, and directly adding voltage-current characteristic points of the resistor pieces in one column to obtain the voltage-current characteristic of the whole column;
the lightning arrester current calculation unit is used for performing exponential function fitting on the volt-ampere characteristics of each column and calculating the current flowing through each column according to the integral residual voltage waveform of the lightning arrester group;
the resistance card absorbed energy calculation unit is used for calculating voltage waveforms born by the resistance cards according to the resistance sub-self volt-ampere characteristic fitting function and then calculating the absorbed energy of the resistance cards;
and the resistance sheet adjusting unit is used for iteratively adjusting the position of the resistance sheet according to the energy absorption matrix, exchanging the resistance sheet with the minimum absorption energy of the current maximum column with the resistance sheet with the maximum absorption energy of the current minimum column, iteratively calculating and repeating the steps.
It is understood that the system provided by the embodiment of the present invention corresponds to the method provided by the embodiment of the present invention, and the explanation, the example and the beneficial effects of the related contents can refer to the corresponding parts in the method.
The invention also provides a computer-readable storage medium, in which a computer program is stored, which computer program, when being executed by a processor, is adapted to carry out the above-mentioned method steps.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.