A current differential protection method and device considering capacitive current

Abstract

The application provides a current differential protection method and device considering capacitor current, wherein the method comprises: when a power transmission line is faulty, taking a direction of a sampling current flowing from a bus to the power transmission line as a positive direction, continuously sampling line currents on both sides of the power transmission line to obtain current sampling values of R sampling points; inputting the current sampling value of the jth sampling point into a pre-established current differential protection criterion to generate a jth criterion result; counting a number of sampling points whose criterion results satisfy the criterion; and determining current differential protection action according to the number of sampling points and a pre-set sampling point number threshold. The method and device utilize the characteristics of the current when the power transmission line is faulty, and simultaneously consider the influence of the line capacitor current, thereby improving the reliability of an out-zone fault in a case where the current sampling value is small, and the sensitivity of an in-zone fault in a case where the current sampling value is large, and making up for the deficiencies of the existing current sampling value differential protection.

Description

Technical Field

[0001] This invention relates to the field of power grid simulation technology, and more specifically, to a current differential protection method and apparatus that takes into account capacitor current. Background Technology

[0002] With the development of intelligent electrical systems, especially the emergence of intelligent switches and electronic instrument transformers, substation automation technology has entered a new digital stage. Digital substations completely solve the problems of current transformer saturation and AC / DC crosstalk in secondary cables, offering advantages such as avoiding redundant construction and automated management, making them the development trend of substation automation. However, all AC data in a digital substation is transmitted through channels, inevitably encountering some interference during transmission, potentially generating abnormal data. While line protection in digital substations does not need to consider current transformer saturation, the identification of abnormal data must be considered. During the construction of digital substations, numerous interconnection lines between digital and traditional substations will inevitably emerge. These lines are characterized by: one side using traditional electromagnetic instrument transformers, requiring measures to prevent current transformer saturation; and the other side using new electronic instrument transformers, requiring measures to prevent abnormal data.

[0003] For line protection, current sampling differential protection is an ideal choice to simultaneously address the saturation problem of electromagnetic instrument transformers and the abnormal data problem of electronic instrument transformers. Sampling differential protection has significant application value in engineering. In existing technologies, ratio-controlled sampling differential protection is a commonly used sampling protection method; however, its operating characteristics have certain defects and it is susceptible to capacitive current. Summary of the Invention

[0004] To address the technical problem that current differential protection in the prior art is easily affected by capacitor current, the present invention provides a current differential protection method and device that takes capacitor current into account.

[0005] According to one aspect of the present invention, a current differential protection method considering capacitor current is provided, the method comprising:

[0006] When a fault occurs in a transmission line, the current in the line on both sides of the transmission line is continuously sampled, with the direction of the sampling current from the bus to the transmission line as the positive direction, to obtain the current sampling values ​​of R sampling points.

[0007] Input the current sampling value of the j-th sampling point into the pre-established current differential protection criterion to generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion;

[0008] The statistical result of the criterion is the number of sampling points that satisfy the criterion;

[0009] The current differential protection action is determined based on the number of sampling points and the preset sampling point threshold.

[0010] According to another aspect of the present invention, the present invention provides a current differential protection device that takes into account capacitive current, the device comprising:

[0011] The current sampling module is used to continuously sample the line current on both sides of the transmission line when a fault occurs, taking the direction of the sampling current from the bus to the transmission line as the positive direction, and obtain the current sampling values ​​of R sampling points.

[0012] The criterion result module is used to input the current sampling value of the j-th sampling point into the pre-established current differential protection criterion and generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion;

[0013] The data statistics module is used to count the number of sampling points whose criteria result satisfy the criteria;

[0014] The result output module determines the current differential protection action based on the number of sampling points and the preset sampling point threshold.

[0015] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0016] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0017] The present invention discloses a current differential protection method and apparatus that considers capacitive current. The method includes: when a fault occurs in a transmission line, continuously sampling the line current on both sides of the transmission line, taking the direction of the sampling current flowing from the busbar to the transmission line as the positive direction, to obtain current sampling values ​​at R sampling points; inputting the current sampling value of the j-th sampling point into a pre-established current differential protection criterion to generate the j-th criterion result; counting the number of sampling points that satisfy the criterion result; and determining the current differential protection action based on the number of sampling points and a pre-set sampling point threshold. The method and apparatus utilize the characteristics that the current on both sides of the transmission line is a through current when there is a fault outside the transmission line zone, and the current is a fault current when there is a fault inside the zone. It also considers the influence of line capacitive current, thereby improving the reliability of external faults when the current sampling value is small, and the sensitivity of internal faults when the current sampling value is large, thus overcoming the shortcomings of existing current sampling value differential protection. Attached Figure Description

[0018] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0019] Figure 1 A flowchart of a current differential protection method considering capacitor current according to a preferred embodiment of the present invention;

[0020] Figure 2 A schematic diagram illustrating the transmission of electrical energy from a renewable energy power plant to an AC system via transmission lines;

[0021] Figure 3 This is a schematic diagram showing the characteristics of the current sampling values ​​on both sides of the transmission line in the sampling value plane when a fault occurs within the transmission line's fault zone.

[0022] Figure 4 This is a schematic diagram showing the characteristics of the current sampling values ​​on both sides of the transmission line in the sampling value plane when an external fault occurs.

[0023] Figure 5 This is a schematic diagram of the protection characteristics of conventional differential protection and the method described in this preferred embodiment in the sampling value plane when a fault occurs within the transmission line's fault zone.

[0024] Figure 6 This is a schematic diagram of the structure of a current differential protection device considering capacitor current according to a preferred embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Detailed Implementation

[0026] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0027] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0028] Exemplary methods

[0029] Figure 1 This is a flowchart of a current differential protection method considering capacitor current according to a preferred embodiment of the present invention. Figure 1 As shown, the flowchart of the current differential protection method considering capacitor current according to this preferred embodiment starts from step 101.

[0030] In step 101, when a fault occurs in the transmission line, the line current on both sides of the transmission line is continuously sampled with the direction of the sampling current flowing from the bus to the transmission line as the positive direction, and the current sampling values ​​of R sampling points are obtained.

[0031] Preferably, when a fault occurs in the transmission line, before continuously sampling the line current on both sides of the transmission line with the sampling current flowing from the busbar to the transmission line as the positive direction, a current differential protection criterion is further established, wherein:

[0032] Obtain the rated voltage and capacitive reactance of the transmission line;

[0033] Calculate the maximum peak value of the capacitive current of the transmission line based on its rated voltage and capacitive reactance;

[0034] The current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient.

[0035] Preferably, the calculation of the maximum peak capacitive current of the transmission line based on its rated voltage and capacitive reactance is performed using the following formula:

[0036]

[0037] In the formula, i cmax U is the peak value of the maximum capacitive current of the transmission line.N and Z c These are the rated voltage and capacitive reactance of the transmission line, respectively.

[0038] Preferably, the current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient, wherein the expression of the current differential protection criterion is:

[0039] |i mj +i nj |>di Cmax

[0040] In the formula, i mj and i nj Let be the current sampling values ​​of the j-th line current on both sides of the transmission line, d be the sensitivity coefficient, and i be the current sampling values ​​of the j-th line current on both sides of the transmission line. cmax This represents the peak value of the maximum capacitive current of the transmission line.

[0041] Preferably, the sensitivity coefficient is between 1 and 1.2.

[0042] In this preferred embodiment, the larger the sensitivity coefficient, the higher the protection reliability and the lower the sensitivity. Therefore, in order to ensure good protection reliability and sensitivity, the sensitivity coefficient needs to be greater than 1, preferably 1 to 1.2.

[0043] In step 102, the current sampling value of the j-th sampling point is input into the pre-established current differential protection criterion to generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion.

[0044] In step 103, the number of sampling points that meet the criteria is counted.

[0045] In step 104, the current differential protection action is determined based on the number of sampling points and the preset sampling point threshold.

[0046] Preferably, determining the current differential protection action based on the number of sampling points and a pre-set sampling point threshold includes:

[0047] When the number of sampling points is less than the sampling point threshold, the current differential protection will not trip.

[0048] When the number of sampling points is not less than the sampling point threshold, the current differential protection output is activated.

[0049] To demonstrate the improvement of this invention over existing current sampling value differential protection, this invention first constructs a sampling value plane that can intuitively reflect the protection performance. Based on this, the distribution characteristics of sampling values ​​under fault conditions inside and outside the protection zone are analyzed. Secondly, the operating characteristics of traditional sampling value differential protection are analyzed on the sampling value plane. Finally, the operating characteristics of the improved protection are compared. Details are as follows:

[0050] Figure 2 This is a schematic diagram illustrating the transmission of electrical energy from a renewable energy power plant to an AC system via transmission lines. (For example...) Figure 2 As shown, the electrical energy from multiple renewable energy power plants is transmitted to the AC system via transmission lines after passing through converter transformers. The direction of the sampling current flowing from the busbar to the transmission line is taken as the positive direction; the side closer to the converter transformer is designated as side m, and the side farther from the converter transformer is designated as side n. Assume the expressions for the current phasors on sides m and n of the transmission line at any sampling point are as follows:

[0051]

[0052] In the formula, I m and I n The sampled values ​​are i m and i n , then i m and i n The connections are as follows:

[0053]

[0054] in,

[0055]

[0056] As can be seen from the above formula, i m and i n In i m and i n The lines connecting the sampled values ​​on the plane, representing the horizontal and vertical coordinates, can be either line segments or ellipses. The major axis 2a of the ellipse is only affected by the fault phase current amplitude ratio A, while the minor axis 2b is affected by both the fault phase current amplitude ratio A and the phase difference. The combined effects of these factors.

[0057] After establishing the above-mentioned sampling value plane model, the characteristics of the current sampling values ​​on both sides of the transmission line on the sampling value plane are discussed in the cases of faults within and outside the transmission line area.

[0058] 1) Fault within the area

[0059] Figure 3 This is a schematic diagram illustrating the characteristics of current sampling values ​​on both sides of a transmission line in the sampling plane when a fault occurs within the transmission line's fault zone. (Example:) Figure 3 As shown, when a fault occurs within the area, the current sampling values ​​(i) on both sides of the transmission line are... m i nWhen the amplitude and phase are exactly the same, the trajectory of the sampled value group on the sampling plane is a line segment on the angle bisector of the first and third quadrants; however, when there are differences in phase and amplitude, the line connecting the sampled value groups within a unit period is an ellipse. The major axis of this ellipse is only affected by the ratio A of the current amplitudes on both sides, while the minor axis is affected by the ratio A of the current amplitudes on both sides and the phase difference. The combined effect of these factors means that during a fault within the area, the current sampling values ​​(i) on both sides of the transmission line... m i n It is mainly located in the first and third quadrants.

[0060] 2) External fault

[0061] Figure 4 This is a schematic diagram illustrating the characteristics of the current sampling values ​​on both sides of a transmission line in the sampling plane when an external fault occurs. When a short-circuit fault occurs outside the transmission line's protection zone, the current flowing through the protection devices on both sides of the line is the through current, and the differential current is the line capacitive current. For fixed line parameters and voltage levels, the maximum value of the capacitive current can be calculated. Therefore, the current sampling values ​​(i) on both sides of the line... m i n The distribution range of the sampled values ​​on the plane can be determined. For example... Figure 4 As shown, the area enclosed by the two diagonal solid lines is the protective braking zone. The hollow circle and solid star in the figure represent the current sampling values ​​(i) when the capacitor current is at its maximum and when the capacitor current is at zero, respectively. m i n (Trajectory)

[0062] Therefore, it can be seen that during external faults, the distribution range of current sampling values ​​on both sides of the transmission line is related to the capacitive current: when there is no capacitive current, (i m i n The line segment connecting the points is a line segment passing through the origin with a slope of -1; when the capacitor current is not zero, the (i) per unit cycle m i n The line connecting (i) forms an ellipse, and (i) m i n ) distributed in i m =i n +i Cmax with i m =i n -i Cmax between.

[0063] After determining the sampling value plane characteristics for faults within and outside the transmission line zone, this invention takes faults within the zone as an example to compare the characteristics of traditional ratio braking differential protection and the current differential protection described in this invention in the sampling value plane.

[0064] The operating criteria for traditional ratio-controlled differential protection are generally as follows:

[0065] |im +i n |>k|i m -i n |

[0066] In the formula, i m i n These are the current sampling values ​​on both sides of the line, and k is the braking coefficient. To ensure the accuracy of the criterion, a method of repeated judgment must be adopted, that is, judgment is performed on R consecutive sampling values. When the number of sampling points that meet the protection criterion is greater than S, the protection trips; when the number of sampling points that meet the protection criterion is less than S, the protection does not trip; when the number of sampling points that meet the protection criterion is equal to S, it is defined as the ambiguous zone of the sampled value differential protection operation. This judgment method is called the R / S criterion of sampled value differential protection.

[0067] From the R / S criterion of the above sampled value differential, we can obtain i m and i n The relationship with the braking coefficient k is shown in the following formula:

[0068]

[0069] The protection characteristics obtained by using the R / S criterion with differential sampling values ​​and the protection criterion using the method described in this invention are placed on the same sampling value plane.

[0070] Figure 5 This is a schematic diagram of the protection characteristics of conventional differential protection and the method described in this preferred embodiment in the sampling plane when a fault occurs within the transmission line's fault zone. Figure 5 As shown, traditional sampled-value differential protection criteria have two problems: 1) The ability of the braking zone to include the origin is weak. That is, when an external fault occurs on the line, the probability of falling into the operating zone increases when the sampled values ​​on both sides of the line are small, reducing the reliability of external faults; 2) As the sampled value increases, the braking zone range increases significantly. In fact, for external faults, the current on both sides of the line exhibits a through-current characteristic, which does not change with the size of the sampled value: the trajectory of the through-current in the sampled value plane is on the angle bisector of the second and fourth quadrants. Therefore, when the sampled value is large, there is no need to increase the braking zone. Increasing the braking zone will lead to a reduction in the operating zone, reducing the sensitivity to faults within the zone. However, the protection braking zone obtained by the method of this preferred embodiment is completely consistent with the distribution range of the sampled value group when there is an external fault, and it makes up for the problems of the braking zone not including the origin and the braking range increasing with the increase of the sampled value in traditional sampled-value protection criteria. Furthermore, for the case of external faults, the braking zone of the traditional sampled-value protection criteria is not consistent with the distribution range of the sampled value group. Figure 2Taking the B-C phase-to-phase short-circuit fault in the transmission line shown as an example, the non-faulty phase A is distributed in the second and fourth quadrants on the sampling value plane, and almost all of it is distributed within the restraint zone, so the protection does not operate. Due to the phase difference between the currents on both sides of the line, some sampling value groups of the faulty phases B and C fall into the restraint zone of the protection before the improvement, which leads to a decrease in the adaptability of the sampling value current differential protection under this condition. However, only a very small number of sampling points of the faulty phases B and C fall into the restraint zone of the improved protection, so the improved protection still has high sensitivity and can operate reliably.

[0071] The current differential protection method considering capacitive current described in this preferred embodiment, when a fault occurs in the transmission line, continuously samples the line current on both sides of the transmission line, taking the direction of the sampling current from the busbar to the transmission line as the positive direction, to obtain the current sampling values ​​of R sampling points; the current sampling value of the j-th sampling point is input into a pre-established current differential protection criterion to generate the j-th criterion result; the number of sampling points that satisfy the criterion result is counted; and the current differential protection action is determined based on the number of sampling points and a pre-set sampling point threshold. Compared with the traditional ratio-controlled sampling value differential protection, this method utilizes the characteristics that the current on both sides of the line is a through current when there is an external fault and the current is a fault current when there is an internal fault, while considering the influence of the line capacitive current. This improves the reliability of external faults when the sampling value is small and the sensitivity of internal faults when the sampling value is large, thus making up for the shortcomings of existing sampling value differential protection.

[0072] Exemplary device

[0073] Figure 6 This is a schematic diagram of a current differential protection device considering capacitive current according to a preferred embodiment of the present invention. Figure 6 As shown, the current differential protection device 600 considering capacitor current according to this preferred embodiment includes:

[0074] The current sampling module 601 is used to continuously sample the line current on both sides of the transmission line when a fault occurs, taking the direction of the sampling current from the bus to the transmission line as the positive direction, and obtain the current sampling values ​​of R sampling points.

[0075] The criterion result module 602 is used to input the current sampling value of the j-th sampling point into the pre-established current differential protection criterion to generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion;

[0076] The data statistics module 603 is used to count the number of sampling points whose criteria result satisfies the criteria.

[0077] The result output module 604 determines the current differential protection action based on the number of sampling points and the preset sampling point threshold.

[0078] Preferably, the device further includes a protection criterion module for establishing current differential protection criteria, wherein:

[0079] Obtain the rated voltage and capacitive reactance of the transmission line;

[0080] Calculate the maximum peak value of the capacitive current of the transmission line based on its rated voltage and capacitive reactance;

[0081] The current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient.

[0082] Preferably, the protection criterion module calculates the maximum peak value of the transmission line's capacitive current based on the transmission line's rated voltage and capacitive reactance, wherein the formula for calculating the maximum peak value of the capacitive current is:

[0083]

[0084] In the formula, i cmax U is the peak value of the maximum capacitive current of the transmission line. N and Z c These are the rated voltage and capacitive reactance of the transmission line, respectively.

[0085] Preferably, the protection criterion module establishes a current differential protection criterion based on the maximum peak value of the capacitive current and the set sensitivity coefficient, wherein the expression of the current differential protection criterion is:

[0086] |i mj +i nj |>di Cmax

[0087] In the formula, i mj and i nj Let be the current sampling values ​​of the j-th line current on both sides of the transmission line, d be the sensitivity coefficient, and i be the current sampling values ​​of the j-th line current on both sides of the transmission line. cmax This represents the peak value of the maximum capacitive current of the transmission line.

[0088] Preferably, the sensitivity coefficient in the protection criterion module is between 1 and 1.2.

[0089] Preferably, the result output module 604 determines the current differential protection action based on the number of sampling points and a preset sampling point threshold, including:

[0090] When the number of sampling points is less than the sampling point threshold, the current differential protection will not trip.

[0091] When the number of sampling points is not less than the sampling point threshold, the current differential protection output is activated.

[0092] The steps of the current differential protection device considering capacitive current described in this preferred embodiment, which acquires the current sampling values ​​on both sides of the line when a line fault occurs, and determines the current differential protection action based on the current sampling values ​​and the set current differential protection criteria, are the same as the steps taken in the current differential protection method considering capacitive current described in this invention, and the technical effects achieved are also the same, so they will not be repeated here.

[0093] Exemplary electronic devices

[0094] Figure 7 This is a schematic diagram of an electronic device according to a preferred embodiment of the present invention. The electronic device may be either or both of a first device and a second device, or a standalone device independent of them. The standalone device may communicate with the first device and the second device to receive the collected input signals from them. Figure 7 A block diagram of an electronic device according to an embodiment of the present disclosure is illustrated. For example... Figure 7 As shown, the electronic device includes one or more processors 401 and memory 402.

[0095] The processor 701 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0096] The memory 702 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 301 may execute the program instructions to implement the energy consumption anomaly diagnosis method based on enterprise energy consumption space of the various embodiments disclosed above, and / or other desired functions. In one example, the electronic device may also include an input device 703 and an output device 704, which are interconnected via a bus system and / or other forms of connection mechanism (not shown).

[0097] In addition, the input device 703 may also include, for example, a keyboard, a mouse, etc.

[0098] The output device 704 can output various information to the outside. The output device 704 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0099] Of course, for the sake of simplicity, Figure 7 Only some of the components of the electronic device relevant to this disclosure are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0100] Exemplary computer program products and computer-readable storage media

[0101] In addition to the methods and apparatus described above, embodiments of this disclosure may also be computer program products comprising computer program instructions that, when executed by a processor, cause the processor to perform the steps in the current differential protection method taking into account capacitive current according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0102] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this disclosure. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on a user's computing device, partially on a user's computing device, as a standalone software package, partially on a user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0103] Furthermore, embodiments of this disclosure may also be computer-readable storage media having computer program instructions stored thereon, which, when executed by a processor, cause the processor to perform the steps in the current differential protection method considering capacitive current according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0104] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may, for example, include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0105] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0106] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0107] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0108] The methods and apparatus of this disclosure may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of this disclosure are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, this disclosure may also be implemented as a program recorded on a recording medium, the program including machine-readable instructions for implementing the methods according to this disclosure. Thus, this disclosure also covers recording media storing programs for performing the methods according to this disclosure.

[0109] It should also be noted that in the apparatus, devices, and methods of this disclosure, the components or steps are decomposable and / or recombinable. Such decomposition and / or recombination should be considered equivalent to the present disclosure. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0110] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A current differential protection method considering capacitor current, characterized in that, The method includes: Establish current differential protection criteria, where: Obtain the rated voltage and capacitive reactance of the transmission line; Calculate the maximum peak value of the capacitive current of the transmission line based on its rated voltage and capacitive reactance; A current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient. When a fault occurs in a transmission line, the current in the line on both sides of the transmission line is continuously sampled, with the direction of the sampling current from the bus to the transmission line as the positive direction, to obtain the current sampling values ​​of R sampling points. The current sampling value of the j-th sampling point is input into the current differential protection criterion to generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion; The statistical result of the criterion is the number of sampling points that satisfy the criterion; The current differential protection action is determined based on the number of sampling points and the preset sampling point threshold.

2. The method according to claim 1, characterized in that, The maximum peak capacitive current of the transmission line is calculated based on its rated voltage and capacitive reactance, wherein the formula for calculating the maximum peak capacitive current is: In the formula, This represents the peak value of the maximum capacitive current of the transmission line. and These are the rated voltage and capacitive reactance of the transmission line, respectively.

3. The method according to claim 1, characterized in that, The current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient, wherein the expression of the current differential protection criterion is: In the formula, and These are the current sampling values ​​of the j-th line current on both sides of the transmission line. The sensitivity coefficient, This represents the peak value of the maximum capacitive current of the transmission line.

4. The method according to claim 3, characterized in that, The sensitivity coefficient ranges from 1 to 1.

2.

5. The method according to claim 1, characterized in that, The step of determining the current differential protection action based on the number of sampling points and a preset sampling point threshold includes: When the number of sampling points is less than the sampling point threshold, the current differential protection will not trip. When the number of sampling points is not less than the sampling point threshold, the current differential protection output is activated.

6. A current differential protection device that takes into account capacitive current, characterized in that, The device includes: The protection criterion module is used to establish current differential protection criteria, including: Obtain the rated voltage and capacitive reactance of the transmission line; Calculate the maximum peak value of the capacitive current of the transmission line based on its rated voltage and capacitive reactance; A current differential protection criterion is established based on the maximum peak value of the capacitive current and the set sensitivity coefficient. The current sampling module is used to continuously sample the line current on both sides of the transmission line when a fault occurs, taking the direction of the sampling current from the bus to the transmission line as the positive direction, and obtain the current sampling values ​​of R sampling points. The criterion result module is used to input the current sampling value of the j-th sampling point into the pre-established current differential protection criterion and generate the j-th criterion result, where 1≤j≤R, and the criterion result includes satisfying the criterion and not satisfying the criterion; The data statistics module is used to count the number of sampling points whose criteria result satisfy the criteria; The result output module determines the current differential protection action based on the number of sampling points and the preset sampling point threshold.

7. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1 to 5.

8. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method as described in any one of claims 1 to 5.

Images