CN110196377B - Power grid voltage sag rating method - Google Patents
Power grid voltage sag rating method Download PDFInfo
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- CN110196377B CN110196377B CN201910313708.5A CN201910313708A CN110196377B CN 110196377 B CN110196377 B CN 110196377B CN 201910313708 A CN201910313708 A CN 201910313708A CN 110196377 B CN110196377 B CN 110196377B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
Abstract
The invention discloses a power grid voltage sag rating method, which comprises the following steps: step one, acquiring a voltage sag monitoring point, three-phase voltage amplitude characteristics of voltage sag and voltage sag duration; step two, judging the type of each voltage sag, and classifying the voltage sag; step three, dividing the equipment into different types of voltage sag immunity grades, and calculating the fault frequency of each type of equipment; determining the weights of the failure times under different voltage sag immunity levels, and performing weighted calculation; step five, obtaining a voltage sag rating index through a voltage sag rating index model; and step six, carrying out voltage sag rating according to the voltage sag rating index. The voltage sag grading index calculated by the method is an index comprehensively measuring the number of voltage sags in a region and the severity degree of single voltage sag, and the larger the index value is, the more serious the voltage sag condition of the region is.
Description
Technical Field
The invention relates to the technical field of electric energy quality, in particular to a power grid voltage sag rating method.
Background
In recent years, the voltage sag brings huge economic loss to sensitive industrial users, and the voltage sag becomes the most serious problem of electric energy quality at present, thereby causing wide attention in the domestic and foreign electrical engineering fields. Besides the traditional power quality problems of harmonic waves, voltage deviation, frequency deviation, voltage fluctuation, flicker and the like, users have different requirements on the transient voltage quality problem. At present, the voltage sag problem is the voltage quality problem most complained by users abroad. The voltage sag is extremely harmful to some equipment, such as PC, ADS, PLC, tripper and other equipment, and great economic loss is brought.
Voltage sag is the instantaneous reduction of the effective value of voltage (RMS) at the system frequency to within 10% to 90% of the rated value, typically for a half power frequency cycle to several seconds. The sag amplitude, duration and phase jump are three major indicators of voltage sag. For the index of voltage sag, there is no unified standard definition internationally, and representative examples thereof include the International Electrotechnical Commission (IEC) standard and the Institute of Electrical and Electronics Engineers (IEEE) standard. IEC defines that voltage sag is 90% -1% of rated value, voltage sag is 1% of rated value and is power supply interruption, and short-time interruption is realized when duration is less than 3 min; IEEE defines voltage sags as 90% -10% of nominal, voltage drops to less than 10% of nominal as a power interruption, duration <1min, as a short interruption.
At present, various evaluation methods exist for the severity of the voltage sag, most of the methods only start from the residual voltage and the duration of the voltage sag, and influence on the equipment side is not considered; or the severity of a single voltage sag is evaluated, and the voltage sag of a regional power grid cannot be described. Since most power electronic devices are very sensitive to voltage sag and the requirements of some users on the quality of electric energy are more and more strict, it is desirable to realize differentiated power supply for users with different sensitivities, and ranking the voltage sag condition of a power grid is a technical problem to be solved urgently at present.
According to the method, the weight of a single voltage sag is determined through the influence of the single voltage sag on each voltage sag immunity level device, and the larger the weight is, the more serious the voltage sag is; then, all voltage sag weighted additions which occur in a regional power grid are added to realize the description of the voltage sag condition of the regional power grid; and dividing the number by the total number of the monitoring points in the region to obtain a rating index, wherein the rating index takes one monitoring point as a unit to ensure that the index is not influenced by the size of a data collection area. The rating index integrates the severity of single voltage sag and the number of regional voltage sags, and finally, the voltage sag rating index of the power grid is carried out according to the index, so that the rating index has certain reliability.
Disclosure of Invention
The invention aims to provide a power grid voltage sag rating method, which comprehensively evaluates the occurrence frequency, duration, residual voltage and influence on equipment of voltage sag in a region, so as to rate the voltage sag in the region, wherein the voltage sag rating index reflects the severity of the voltage sag of a power grid in the region.
In order to solve the technical problem, the invention provides a power grid voltage sag rating method, which comprises the following steps of:
step one, acquiring voltage sag monitoring points, three-phase voltage amplitude characteristics of each voltage sag, voltage sag duration and other characteristic quantities; acquiring voltage sag monitoring points in a power grid, wherein the default configuration conditions of the monitoring points are that the voltage sag of the whole power grid can be observed and the number of the monitoring points is minimum;
judging the type of each voltage sag according to the residual voltage amplitude characteristics, and classifying the voltage sags;
step three, dividing the equipment into voltage sag immunity grades of different types, determining the severity of single voltage sag according to the types of fault equipment caused by certain voltage sag, and calculating the fault frequency of each type of equipment; for each type of voltage sag, drawing a voltage sag immunity curve of the equipment to the type of voltage sag, and summarizing the immunity curves of all the equipment into voltage sag immunity curves of several grades according to the immunity degree because the voltage sag immunity degrees of different types of equipment have high and low scores;
determining the weights of the failure times under different voltage sag immunity levels, and performing weighted calculation; in each type of voltage sag, weighting the equipment failure times under each immunity curve to obtain a severity index of each type of voltage sag, and recording the severity index as a primary rating index;
dividing the preliminary rating index by the total number of the monitoring points of the region through a voltage sag rating index model to obtain a rating index taking one monitoring point as a unit, ensuring that the index is not influenced by the size of a voltage sag data collecting area and recording the rating index as a voltage sag rating index of a power grid of the region;
and step six, carrying out voltage sag rating according to the voltage sag rating index.
In summary, for a single voltage sag, if the duration is short and the residual voltage is high, only one type of device with low immunity to voltage sag fails, and the weighting result is small; if the duration is long and the residual voltage is low, the devices with the voltage sag immunity degrees of all levels may be in failure, and the weighting result is large. The voltage sag rating index calculated by the method is an index comprehensively measuring the number of voltage sags in a region and the severity degree of single voltage sag, and the larger the index value is, the more serious the voltage sag condition in the region is.
Preferably, the voltage sag in step two is of three types: voltage sags with the same amplitude as the three-phase voltage amplitude drop are classified into type three; voltage sag of a line voltage amplitude drop in the three-phase residual voltage is classified into type two; voltage dips in the three-phase residual voltage, which have predominantly a drop in amplitude with respect to the ground voltage, are classified as type one.
Preferably, the voltage sag immunity curve of the device is indicated in CIGRE/circuit/UIE Joint Working Group c4.110.voltage dip immunity of the apparatus and the apparatus can be divided into A, B, C and D voltage sag immunity grades according to the voltage sag immunity degree of the apparatus, and the severity of a single voltage sag is determined according to the type of the apparatus that can cause a certain voltage sag, wherein the type a apparatus has the highest voltage sag immunity grade, the number of failures is the least, the immunity of the type a to the type D apparatus is sequentially reduced, and the number of failures is sequentially increased.
Preferably, the number of failures of the device is calculated by a calculation method of a device immunity curve and a voltage sag height map.
The immunity curve of the device of the invention, the voltage sag contour map, is generally drawn in an X-Y coordinate system, the abscissa represents the duration of the voltage sag, the ordinate represents the residual voltage, the voltage sag characteristic and the voltage sag immunity curve in the power grid are plotted in the same graph, specifically, a two-dimensional matrix or a table of voltage sag residual voltage and duration is formed, a contour line form is used for representing the two-dimensional matrix or the table to obtain a voltage sag contour map, the lowest residual voltage which can be endured by the equipment in each voltage sag duration is obtained through simulation or measurement, a voltage sag immunity curve can be drawn, and the curve envelops an abnormal working area of the equipment, the voltage sag immunity curve of the device gives the range of voltage sag that the device can bear, and the curve can be provided by a device manufacturer or obtained through the test and simulation of the device.
When the voltage sag immunity curve is a rectangle, the rectangular part represents a voltage sag range causing equipment failure, and the intersection point of the equipment voltage sag immunity curve and the power supply voltage sag contour map determines the number of times of voltage sag causing equipment failure; when the voltage sag immunity curve is not a rectangle, the abnormal working area of the equipment can be approximately divided according to the rectangle, so that the voltage sag frequency causing the equipment fault is estimated.
Preferably, the voltage sag immunity curve is plotted according to a voltage sag type.
When the frequency of equipment faults under the voltage sag immunity curves of all levels is calculated for each type of voltage sag, the frequency of the faults of certain equipment caused by certain voltage sag is determined by adopting a calculation method for drawing a device immunity curve-voltage sag equal height graph.
Preferably, for a voltage sag within the immunity of various devices, the devices connected to the power grid cannot be influenced and cannot be included in the rating index; one serious voltage sag which causes faults to various devices is weighted by the weights of the various devices, the sum of the weights is 1, namely the preliminary rating index is added with 1; voltage sags with a severity between the two, the contribution to the preliminary rating index being greater than 0 and less than 1.
Preferably, the calculation process of step four is: respectively taking the failure times weights of the equipment from the class A to the class D as 0.4, 0.3, 0.2 and 0.1, and meeting the following conditions:
in the formula (1), mijWeighting weights representing the number of times of faults of the j-th class of equipment under the ith class of voltage sag, wherein the sum of the weights of all classes of equipment is 1;
in the formula (2), θiRepresenting the weighting result of the failure times of various devices caused in the ith class voltage sag of the power grid, wherein j represents the device type, i is 1-3, and m isijWeight, N, corresponding to the number of times that the class j device fails during the class i voltage sagijIndicating the number of times in the class i voltage sag that causes the class j device to fail.
For a single voltage sag, the contribution of the primary rating measure satisfies:
wherein m isjWeights, N, representing the number of failures of class A, B, C, D devices, respectivelyjIndicating whether the voltage sag is outside the immunity range of the corresponding equipment, if so, causing a fault, and then NjIs 1, otherwise is 0.
Preferably, the voltage sag rating evaluation index model is obtained by performing the weighted summation calculation on each type of voltage sag, adding the weighted summation results of each type of voltage sag, and dividing the sum by the total number of monitoring points in the region, and the model is as follows:
in the formula (4), xi is a voltage sag rating index, the larger the xi value is, the more serious the voltage sag condition in the area is, i represents a voltage sag type, j represents a device type, namely a device type with different immunity grades, mijWeights corresponding to the number of times of leading to j-th equipment failure in i-th class voltage sag are represented, the sum of the weights is 1, NijIndicating the number of times in the class i voltage sag that causes the class j device to fail. n is the number of monitoring points, r represents the type number of voltage sag, the invention divides the voltage sag into 3 classes, k represents the voltage sag immunity grade number of the equipment, and the invention divides the equipment immunity grade into 4 grades.
The voltage sag rating index xi comprehensively evaluates the frequency, duration and characteristic amplitude of the voltage sag of the power grid: the more the number of dips, NijThe larger the voltage sag rating index ξ is, the larger; when the duration of a single voltage sag is longer or the residual voltage is lower, more types of equipment faults can be caused, and the corresponding weight m is larger, the contribution to the voltage sag rating index xi is larger; for a single voltage sag, the maximum contribution to ξ is 1 and the minimum 0.
Preferably, the voltage sag rating index in step five includes the severity of each voltage sag, i.e. the number of voltage sags occurring in the power grid for each type of equipment.
Preferably, the voltage sag rating is performed according to the voltage sag rating index, the rating standard of the voltage sag rating in the sixth step is divided into a first level, a second level, a third level and a fourth level, the power quality gradually decreases in the rating standard from the first level to the fourth level, and the voltage sag may cause the number of equipment failures to increase, specifically as follows:
the first level represents that the power quality in the power grid is good, and the voltage sag hardly causes equipment failure;
the secondary level represents that the quality of electric energy in the power grid is good, partial equipment faults can be caused by voltage sag, but the number of faults is small and is within an acceptable range;
the third level represents that the quality of electric energy in the power grid is general, and voltage sag easily causes equipment with low voltage sag immunity to break down;
the four levels represent that the quality of electric energy in the power grid is poor, voltage sag can cause more faults of equipment, and a power supply protection device needs to be additionally arranged on the equipment or the voltage sag condition of the power grid is improved.
The invention is established on the basis of voltage sag monitoring data of a power grid and a voltage sag immunity curve of a device side, comprehensively considers the quantity, duration, residual voltage and other characteristic values of voltage sag, and gives a voltage sag rating of the power grid of a region according to the severity of the voltage sag of the region.
Compared with the prior art, the invention has the beneficial effects that: the two regions with different dimensions can be compared without the limitation of the length of a sag data monitoring interval and the area size of the region, and the voltage sag occurrence frequency and the severity of each voltage sag of the regions are comprehensively considered to obtain visual and visible comprehensive evaluation indexes.
Drawings
FIG. 1a is a graph of voltage sag immunity for class A devices of type one and type two in this example;
FIG. 1b is a graph of the voltage sag immunity of class A devices to class three in this example;
FIG. 2a is a graph of voltage sag immunity for class B versus class one and class two in this example;
FIG. 2B is a graph of the voltage sag immunity of class B devices for class three in this example;
FIG. 3a is a graph of voltage sag immunity for class C devices of type one and type two in this example;
FIG. 3b is a graph of the voltage sag immunity of class C devices for class three in this example;
FIG. 4a is a graph of voltage sag immunity for class D versus class one and class two in this example;
FIG. 4b is a graph of the voltage sag immunity of the class D device of this example for class three;
FIG. 5 is a graph of immunity of class A devices to type one and type two voltage devices in area a of this embodiment, i.e., voltage sag, etc.;
fig. 6 is a flowchart of a method for rating a voltage sag of a power grid in the present embodiment.
Detailed Description
The invention is described in further detail below with reference to the attached drawing. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 6, the method for rating the voltage sag of the power grid provided by the present invention mainly includes the following steps:
s101, acquiring a certain city monitoring point configuration model, three-phase voltage amplitude characteristics of voltage sag from 1 month in 2017 to 12 months in 2017 and voltage sag duration from a power grid;
in this embodiment, 9 monitoring points installed in an area a of a certain city are obtained, and a voltage sag 485 occurs in total, and 10 monitoring points are installed in an area b, and a voltage sag 533 occurs in total.
S102, judging the type of each voltage sag according to the residual voltage amplitude characteristics, and classifying the voltage sags;
voltage sags are divided into three basic types: the three-phase voltage amplitude drops by the same amplitude and is type three, the three-phase residual voltage mainly has a line voltage amplitude drop by type two, and the three-phase residual voltage mainly has a phase-to-ground voltage amplitude drop by type one.
The type criterion of the voltage sag is as follows:
arranging the three-phase voltage effective values in the order V from small to largex＜Vy＜Vz；
Vz-Vy＜Vy-Vx (3)
1/2(Vz+Vy)＜(0.3+0.7×Vx) (4)
1/2(Vz+Vy)≥(0.3+0.7×Vx) (5)
Vz-Vy≥Vy-Vx (6)
Vz＜(0.3+0.35×(Vx+Vy)) (7)
Vz≥(0.3+0.35×(Vx+Vy)) (8)
If formula (3) formula (4) or formula (6) formula (7) is satisfied simultaneously, it is determined as type three, if formula (3) formula (5) is satisfied simultaneously, it is determined as type one, and if formula (6) formula (8) is satisfied simultaneously, it is determined as type two.
Through the above determination method, in the voltage sag of the area a, 332 starts for the type one, 120 starts for the type two, 33 starts for the type three, and in the voltage sag of the area b, 430 starts for the type one, 82 starts for the type two, and 21 starts for the type three.
S103, dividing the equipment into different types of voltage sag immunity levels, determining the severity of single voltage sag according to the types of fault equipment caused by certain voltage sag, and calculating the fault frequency of each type of equipment;
dividing the devices into A, B, C and D four types of voltage sag immunity levels, determining the severity of a single voltage sag according to the types of fault devices caused by a certain voltage sag, wherein the A-D types of devices have sequentially reduced immunity and sequentially increased fault times, the voltage sag immunity curves of the voltage sag types corresponding to the A type of devices are shown in FIG. 1a and FIG. 1B, the voltage sag immunity curves of the voltage sag types corresponding to the B type of devices are shown in FIG. 2a and FIG. 2B, the voltage sag immunity curves of the voltage sag types corresponding to the C type of devices are shown in FIG. 3a and FIG. 3B, and the voltage sag immunity curves of the voltage sag types corresponding to the D four types of devices are shown in FIG. 4a and FIG. 4B, FIGS. 1a to 4b are all from CIGRE/CIRED/UIE Joint Working Group C4.110.Voltage diode immunity of apparatuses and apparatuses.
The failure times are calculated by a voltage sag immunity curve-voltage sag altitude graph, the device immunity curve-voltage sag altitude graph of the present embodiment is shown in fig. 5, the abscissa is the voltage sag duration(s), the ordinate is the voltage sag residual voltage (%), the label of each curve represents the number of voltage sags in one year, and fig. 5 graphically shows the characteristics of voltage sag in the area a in the type one and the type two by using a contour diagram, and the type one and the type two voltage sag immunity curves of the type a device are added.
In fig. 5, each point on the curve represents the number of voltage dips of the monitoring point in the year, and in the contour diagram of the voltage dips, the voltage dip immunity curve of the device is added, and the portion of the envelope at the lower right of the voltage dip immunity curve in the diagram indicates that the voltage dips in the area can cause device failure; the frequency of equipment faults is determined by the intersection point of a voltage sag immunity curve and a voltage sag contour line of the equipment, and the specific calculation mode is as follows:
the voltage sag immunity curve of the class A device has three inflection points P, Q and R, and the voltage sag immunity curve of the class A device can be divided into three rectangular areas of A, B and C, wherein the inflection point P comprises two rectangles of A and B, the inflection point Q comprises one rectangle of B, and the R comprises two rectangles of B and C. The inflection point P falls on a 35-time voltage dip contour line, which shows that the failure times contained by the A and B rectangles are 35 times; the inflection point Q is located in the region between the 20 voltage sag contours and the 25 voltage sag contours, and an estimate can be made by linear interpolation: the inflection point Q is about to fall on a contour line of voltage sag for 23 times, which shows that the number of faults contained in the second rectangle is 23 times; the inflection point R is located in the region between the 20 voltage sag contours and the 25 voltage sag contours, and an estimate can be made by linear interpolation: the inflection point R is about to fall on the contour line of 23 voltage sags, which shows that the number of faults contained by the rectangles B and C is 23.
Written in equation form is: the voltage sag immunity curve of the whole class a device comprises 35 times of device failures, 23 times of device failures and 35 times of device failures. According to the calculation of the method, the failure times of the A-type equipment in various voltage sags in the area a are 35 times, the failure times of the B-type equipment in 45 times, the failure times of the C-type equipment in 67 times and the failure times of the D-type equipment in 87 times can be obtained in the same way, and the failure times of the A-type equipment in various voltage sags in the area B are 78 times, the failure times of the B-type equipment in 89 times, the failure times of the C-type equipment in 102 times and the failure times of the D-type equipment in 134 times.
S104, determining the weights of the failure times under different voltage sag immunity levels, and performing weighted calculation;
as shown in fig. 1a to 4b, the voltage sag duration time of the class a device having a fault is the longest and the residual voltage is the lowest, and the voltage sag duration time of the class D device having a fault is the shortest and the residual voltage is the highest, so that if a certain voltage sag causes the class a device to have a fault, the voltage sag severity is the highest.
Therefore, when the failure times of various types of equipment are weighted, the voltage sag causing the failure of the type A equipment represents the most serious type of voltage sag in the power grid, the contribution to the severity degree of the voltage sag is the largest, the contribution to the rating index is also the largest, and the weight is the largest;
class B, class C;
the class D device is most prone to failure, so the voltage sag that causes the class D device failure is overall less severe, so the weight of the class D failure voltage sag is the smallest in the evaluation index.
Preferably, the failure times weights of the A-D equipment are respectively taken as 0.4, 0.3, 0.2 and 0.1 by adopting an empirical method, and the following conditions are met:
in the formula (9), mijAnd weighting weights representing the number of times of faults of the j-th class device under the ith class voltage sag, wherein the sum of the weights is 1.
In the formula (10), θiRepresenting the weighting result of the number of the faults of various devices caused in the ith class voltage sag of the power grid, wherein j represents the type of the devices, and m isijWeight N corresponding to the number of times of the j-th type of equipment failure in the voltage sagijIndicating the number of times in the class i voltage sag that causes the class j device to fail. The finally obtained voltage sag rating index xi is to make each type of voltage sagCorresponding to thetaiAnd (4) summing.
S105, establishing a voltage sag rating evaluation index model as shown in a formula (11)
In the formula (11), xi is a voltage sag rating index, and the bigger xi is, the more serious the voltage sag condition in the area is; i represents the type of voltage sag; j represents a device type; m isijWeight, N, corresponding to the number of times that the class i voltage sag causes the class j device to failijRepresenting the number of times of the i-th class voltage sag that causes the j-th class device to fail; n is the number of monitoring points.
The voltage sag rating index xi comprehensively evaluates the frequency, duration and characteristic amplitude of the voltage sag of the power grid: the more the number of dips, NijThe larger, the larger ξ; when the single sag is longer in duration or the residual voltage is lower, more types of equipment faults can be caused, and the corresponding weight m is larger, so that the zeta is more greatly contributed; for a single dip, the maximum contribution to ξ is 1 and the minimum 0.
According to the formula (11), obtaining the voltage sag rating indexes of areas a and b respectively: xia＝5.51，ξb＝9.17。
And S106, carrying out voltage sag rating according to the voltage sag rating index.
The rating index xi is less than 5, and is judged as the first grade, which represents that the power quality in the power grid is good, and the voltage sag hardly causes equipment failure;
the grade index xi is greater than or equal to 5 and less than 10, and is judged as a second grade, which represents that the power quality in the power grid is better, and the voltage sag can cause partial equipment faults, but the number of the faults is less and is within an acceptable range;
the grade index xi is more than or equal to 10 and less than 15, and is judged to be three-level, which represents that the quality of electric energy in the power grid is general, and voltage sag easily causes the equipment with low voltage sag immunity to break down;
and the rating index xi is more than or equal to 15, and is judged as four levels, which represents that the quality of electric energy in the power grid is poor, and the voltage sag can cause more faults of equipment, so that a power supply protection device needs to be additionally arranged on the equipment or the voltage sag condition of the power grid is improved.
And determining the corresponding rating index range of each voltage sag grade according to the above rating standards and according to the actual conditions of the region, such as the load quantity, the area of the region, the economic development condition and the like.
The method for rating the voltage sag of the power grid provided by the invention is described in detail above, and the above description is only used for helping to understand the method and the core idea of the invention. If the invention is applied to the related technical field indirectly or directly, the invention is included in the protection scope of the patent of the invention.
Claims (7)
1. A method for rating a voltage sag of a power grid, comprising the steps of:
step one, acquiring a voltage sag monitoring point, three-phase voltage amplitude characteristics of voltage sag and voltage sag duration;
step two, judging the type of each voltage sag, and classifying the voltage sag;
step three, dividing the equipment into different types according to the voltage sag immunity curve of the equipment,
step four, calculating the frequency of the faults of different types of equipment caused by different types of voltage sag;
step five, carrying out weighted calculation on the frequency of the faults of different types of equipment under the same type of voltage sag to obtain severity indexes of each type of voltage sag, and recording the severity indexes as preliminary rating indexes; the specific calculation process is as follows:
respectively taking the A-D equipment failure times weights as 0.4, 0.3, 0.2 and 0.1, and meeting the following conditions:
in the formula (1), mijWeighted weights representing the number of failures occurring in class j devices under class i voltage sagsThe sum of the weights is 1;
in the formula (2), θiRepresenting the weighting result of the number of times of faults of various devices caused in the ith class of voltage sag of the power grid, namely the preliminary rating index of the ith class of voltage sag, j represents the type of the devices, i is 1-3, mijWeight N corresponding to the number of times of the j-th type of equipment failure in the voltage sagijRepresenting the number of times of the i-th class voltage sag that causes the j-th class device to fail;
for a single voltage sag, the contribution of the preliminary rating index satisfies:
wherein m isjWeights, N, representing the number of failures of class A, B, C, D devices, respectivelyjIndicating whether the voltage sag is outside the immunity range of the corresponding equipment, if so, causing a fault, and then NjIs 1, otherwise is 0;
step six, carrying out weighted calculation on the preliminary rating indexes of different types of voltage sag to obtain voltage sag rating indexes;
the voltage sag rating index is obtained by summing the preliminary rating indexes of each type of voltage sag and finally dividing the sum by the total number of the monitoring points of the region, and the model is as follows:
in the formula (4), xi is a voltage sag rating index, the larger the xi value is, the more serious the voltage sag condition in the area is, i represents a voltage sag type, j represents a device type, namely a device type with different immunity grades, mijIndicating class i voltage sag leading to class jThe sum of the weights corresponding to the frequency of equipment failure is 1, NijRepresenting the number of times of failures of jth equipment caused in ith class of voltage sag, wherein n is the number of monitoring points, r is the number of types of voltage sag, the voltage sag is divided into 3 classes, k is the voltage sag immunity grade number of the equipment, and the equipment immunity grade is divided into 4 grades;
and step seven, evaluating the voltage sag grade of each power grid according to the voltage sag grade indexes of different power grids, thereby judging the condition of equipment failure caused by the power quality and the voltage sag in different power grids.
2. A rating method as claimed in claim 1, wherein the voltage sags in step two are divided into three types: voltage sags with the same amplitude as the three-phase voltage amplitude drop are classified into type three; voltage sag of one line voltage amplitude drop in the three-phase residual voltage is classified into type two; voltage dips in three-phase residual voltages with a voltage drop in magnitude relative to ground are classified as type one.
3. A rating method as claimed in claim 2, wherein the devices are classified into A, B, C, D types in the third step, the severity of a single voltage sag is determined by the type of faulty device caused by a voltage sag, the immunity of the devices in the a to D classes decreases in turn, and the number of faults increases in turn.
4. A rating method as claimed in claim 3, wherein the number of failures of step four is calculated by a voltage sag immunity curve-voltage sag contour map.
5. A rating method as claimed in claim 4, wherein for a voltage sag within the immunity of the classes of equipment, the equipment docked in the grid is not affected and not included in the rating scale; the voltage sag which causes faults to various equipment is weighted by the weights of the various equipment, the sum of the weights is 1, namely the preliminary rating index is added with 1; voltage sags with a severity between the two, the contribution to the preliminary rating index being greater than 0 and less than 1.
6. A rating method as claimed in claim 5, wherein the voltage sag immunity curve is plotted according to voltage sag type.
7. A rating method as claimed in claim 6, wherein the rating criteria of the voltage sag rating in step seven are divided into first, second, third and fourth levels; the quality of electric energy in the first-level to fourth-level power grids is reduced, and the frequency of equipment faults is increased due to voltage sag.
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| CN111242433B (en) * | 2020-01-02 | 2022-07-22 | 深圳供电局有限公司 | Power data identification method and device, computer equipment and storage medium |
| CN112116013B (en) * | 2020-09-24 | 2021-07-20 | 四川大学 | Voltage sag event normalization method based on waveform characteristics |
| CN112285410B (en) * | 2020-09-29 | 2022-07-01 | 国网宁夏电力有限公司中卫供电公司 | Method, medium and system for estimating severity of voltage sag |
| CN113656237A (en) * | 2021-07-16 | 2021-11-16 | 华南理工大学 | Load voltage sag immunity rating method, system, device and medium |
| CN113675842B (en) * | 2021-07-27 | 2024-04-12 | 华南理工大学 | Voltage sag compatibility evaluation method, system, device and medium |
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