CN114221307B - Circuit differential protection braking coefficient adjusting method and device and electronic equipment - Google Patents
Circuit differential protection braking coefficient adjusting method and device and electronic equipment Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention discloses a method for adjusting a brake coefficient of line differential protection, which comprises the following steps: collecting synchronous voltage and synchronous current at the protection installation positions on two sides of the line; calculating voltage fault components and current fault components on two sides of the line based on the synchronous voltage and synchronous current on two sides of the line; calculating the phase difference between the voltage fault components and the current fault components on two sides of the line according to the voltage fault components and the current fault components; calculating the difference value of the phase differences of the two sides according to the phase differences of the voltage fault components and the current fault components of the two sides of the line; and calculating a braking coefficient according to the difference value of the phase differences of the two sides. The scheme of the invention is suitable for power transmission and distribution lines with power electronic power supply access, and can obviously improve the line differential protection sensitivity of the high-permeability power electronic equipment access power grid.
Description
Technical Field
The present invention relates to the field of power system relay protection, and in particular, to a method and an apparatus for adjusting a braking coefficient of differential protection of a circuit, and an electronic device.
Background
With the rapid development and engineering construction of technologies such as new energy power generation, flexible direct current transmission and the like, the structure of a traditional power system is gradually changed, the duty ratio of a traditional synchronous generator is continuously reduced, the duty ratio of a power electronic power supply is gradually increased, and because of the large difference between the fault characteristics of the power electronic power supply and the synchronous generator, the relay protection of the traditional power system based on the design of the synchronous generator also faces unprecedented challenges.
The differential protection is the most common main protection of the current power transmission line, and most faults in the areas are cut off by differential protection actions, so that the safe and stable operation of the power grid is effectively ensured. In a traditional power system, the differential protection has good sensitivity due to the constant equivalent potential before and after the synchronous generator faults. However, when the high-permeability power electronic power supply is connected to the power grid, the power grid fault form is very controllable, and the short-circuit current phases at two sides of the fault line in the area can swing a larger angle, so that differential current is reduced, braking current is increased, the sensitivity of differential protection is greatly reduced, great threat is brought to the safe operation of the power grid, and the differential protection sensitivity improvement technology of the high-permeability power electronic power supply connected to the power grid needs to be researched.
Disclosure of Invention
In order to solve the defects in the prior art, the invention discloses a method, a device and electronic equipment for adjusting a circuit differential protection braking coefficient, which dynamically adjust the differential protection braking coefficient by utilizing the difference value of the phase difference between voltage fault components and current fault components at two sides of a circuit, and realize the improvement of time-lapse protection sensitivity when a power electronic power supply is connected into a power grid.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
As a first aspect of the present invention, a method for adjusting a brake coefficient of line differential protection is provided, including:
Collecting synchronous voltage and synchronous current at the protection installation positions on two sides of the line;
Calculating voltage fault components and current fault components on two sides of the line based on the synchronous voltage and synchronous current on two sides of the line;
Calculating the phase difference between the voltage fault components and the current fault components on two sides of the line according to the voltage fault components and the current fault components;
calculating the difference value of the phase differences of the two sides according to the phase differences of the voltage fault components and the current fault components of the two sides of the line;
and calculating a braking coefficient according to the difference value of the phase differences of the two sides.
Further, the calculating the line side voltage fault component and the line side current fault component based on the synchronous voltage and the synchronous current on the line side includes:
calculating positive sequence components and negative sequence components of the voltages and the currents at two sides according to a symmetrical component method based on the synchronous voltages and the synchronous currents at two sides of the circuit;
the two-sided voltage fault component and the current fault component are calculated based on the positive sequence component and the negative sequence component of the two-sided voltage and current.
Further, the voltage fault components include a positive sequence voltage fault component and a negative sequence voltage fault component; the current fault components include a positive sequence current fault component and a negative sequence current fault component.
Further, the phase difference calculation formula of the voltage fault component and the current fault component at two sides of the line is as follows:
Wherein, The positive sequence voltage fault component and the negative sequence voltage fault component of the side are respectively; The current fault component is a positive sequence current fault component at the side and a negative sequence current fault component at the side respectively; θ m +、θm - is the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side, and the phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the current side;
The voltage fault components are respectively opposite positive sequence voltage fault components and opposite negative sequence voltage fault components; /(I) The fault components are opposite positive sequence current fault components and opposite negative sequence current fault components respectively; θ n +、θn - is the phase difference between the opposite positive sequence voltage fault component and the positive sequence current fault component, and the opposite negative sequence voltage fault component and the negative sequence current fault component, respectively.
Further, the difference calculation formula of the two-side phase difference is:
wherein delta theta is the difference value of the phase difference of the two sides; the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side and the opposite side is respectively; /(I) The phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the side and the opposite side respectively; k +、K- is a positive sequence weight coefficient and a negative sequence weight coefficient, respectively, satisfying 0.ltoreq.k +≤1,0≤K-≤1,K++K- =1.
Further, the calculation formula of the braking coefficient is as follows:
Wherein K r is a brake coefficient; k rmin、Krmax is a minimum limit value and a maximum limit value of a brake coefficient respectively, wherein K rmin＜Krmax is more than 0 and less than 1; delta theta is the difference of the phase difference of the two sides; Δθ set1、Δθset2 is a first difference threshold and a second difference threshold, Δθ set1＜Δθset2; the function K r =f (|Δθ|) satisfies that when Δθ set1≤|Δθ|≤Δθset2, K r increases with an increase in |Δθ|.
Further, the function K r =f (|Δθ|) is a linear function or a nonlinear function.
Further, the brake coefficient and the differential current together form a line differential protection criterion,
The differential current is the sum of synchronous current phasors at two sides, the braking current is the difference of the synchronous current phasors at two sides,
The braking characteristic equation of the line differential protection criterion is:
Wherein, K r is the braking coefficient, Is differential current,/>For braking current, I set is a differential threshold;
and judging that the vehicle is in the zone fault when the braking characteristic equation is satisfied, and judging that the vehicle is out of the zone fault otherwise.
As a second aspect of the present invention, there is provided a line differential protection device including a data acquisition unit, a fault component calculation unit, a voltage-current phase difference calculation unit, a brake coefficient calculation unit, and a fault determination unit, wherein:
The data acquisition unit is used for acquiring synchronous voltage and synchronous current at the protection installation positions on two sides of the line;
A fault component calculation unit for calculating a voltage fault component and a current fault component on both sides of the line based on the synchronous voltage and the synchronous current on both sides of the line;
The voltage-current phase difference calculation unit is used for calculating the phase difference between the voltage fault component and the current fault component at two sides of the line according to the voltage fault component and the current fault component;
the difference value calculation unit is used for calculating the difference value of the phase differences at two sides according to the phase differences of the voltage fault components and the current fault components at two sides of the line;
A brake coefficient calculating unit for calculating a brake coefficient according to the difference value of the phase differences of the two sides;
And the fault judging unit is used for judging faults according to the line differential protection criterion formed by the brake coefficients.
As a third aspect of the present invention, an electronic device is provided, including a processor and a storage medium; the storage medium is used for storing instructions; the processor is configured to operate in accordance with the instructions to perform the steps of any of the methods described above.
The beneficial effects of the invention are as follows: compared with the prior art, the scheme that the original differential protection braking coefficient is fixed is abandoned, the phase difference between the voltage fault component and the current fault component is adopted to represent the fault characteristic of the power supply, and the differential protection braking coefficient is dynamically adjusted according to the difference of the fault characteristics of the power supplies at two sides. For a circuit with a power electronic power supply connected in, when an in-zone fault occurs, the differential protection braking coefficient can be adaptively adjusted along with the phase swing degree of the short-circuit current at two sides, so that the sensitivity of differential protection is remarkably improved.
Drawings
FIG. 1 is a schematic diagram of a two-node system according to an exemplary embodiment;
FIG. 2 is a flow chart of a method for adjusting a brake coefficient of line differential protection according to an embodiment of the present invention;
FIG. 3 is a graph showing the preferred adjustment of the differential protection brake coefficient of the present invention;
FIG. 4 is a schematic illustration of the differential protection braking feature of the present invention;
FIG. 5 is a schematic diagram of a differential protection device for a circuit according to an exemplary embodiment of the present invention;
Fig. 6 is a block diagram of an electronic device in accordance with an exemplary embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples, so that those skilled in the art can better understand the present invention and implement it, but the examples are not limited thereto.
Line differential protection identifies faults by comparing differential current, which is made up of current on both sides of the line, with brake current. When the fault occurs in the area, short-circuit currents on two sides flow to the circuit from the bus, the differential current is large, the braking current is small, and the differential element acts. When the fault occurs outside the area, one side current flows to the line from the bus, the other side current flows to the bus from the line, and the two currents have the same magnitude and opposite directions, so that the differential current is zero, and the differential element does not act. In a traditional power system, the differential protection has good sensitivity due to the constant equivalent potential before and after the synchronous generator faults. However, when the high-permeability power electronic power supply is connected to the power grid, the power grid fault form is very controllable, and the short-circuit current phases at two sides of the fault line in the area can swing by a large angle, so that the differential current is reduced, the braking current is increased, and the sensitivity of differential protection is greatly reduced. The application dynamically adjusts the differential protection braking coefficient by utilizing the difference value of the phase difference between the voltage fault component and the current fault component at two sides of the line, thereby realizing the improvement of the differential protection sensitivity when the power electronic power supply is connected into the power grid.
Fig. 1 shows a schematic diagram of a two-node system according to an exemplary embodiment. As shown in fig. 1, a schematic diagram of a two-node system is shown, for convenience of description, the M side is referred to as the home side, the N side is referred to as the opposite side, and the protection device M, N is used for receiving current, voltage and electric quantity data to perform line fault identification.
As shown in fig. 2, the method for adjusting the brake coefficient of the differential protection of the line provided by the embodiment of the invention includes the following steps:
S10: and collecting synchronous voltage and synchronous current at the protection installation positions on two sides of the line.
The protection devices arranged on two sides of the circuit acquire synchronous voltage and synchronous current at the protection installation part through a voltage transformer and a current transformer, and the synchronous voltage and the synchronous current on the side are recorded asThe contralateral synchronization voltage and synchronization current are noted/>Wherein/>Representing different phases.
S20: and calculating voltage fault components and current fault components on two sides of the line based on the synchronous voltage and the synchronous current on the two sides of the line. Wherein the voltage fault components include a positive sequence voltage fault component and a negative sequence voltage fault component; the current fault components include a positive sequence current fault component and a negative sequence current fault component.
In some embodiments, the specific implementation steps of S20 include:
S21: calculating positive sequence components and negative sequence components of the voltages and the currents at two sides according to a symmetrical component method based on the synchronous voltages and the synchronous currents at two sides of the circuit;
Wherein, The positive sequence component and the negative sequence component of the synchronous voltage of the local side are respectively,/>Synchronous current positive sequence component and negative sequence component of the local side respectively,/>Positive and negative sequence components of the synchronous voltage on opposite sides,/>, respectivelyThe positive sequence component and the negative sequence component of the synchronous current at opposite sides are respectively calculated as follows, alpha represents an operator of the phasor phase relation:
S22: the two-sided voltage fault component and the current fault component are calculated based on the positive sequence component and the negative sequence component of the two-sided voltage and current. The voltage fault components and the current fault components on two sides are obtained by subtracting the voltage and the current phase values of k (k is more than or equal to 1) times before the current time.
S30: and calculating the phase difference between the voltage fault component and the current fault component at two sides of the line according to the voltage fault component and the current fault component.
The phase difference calculation formula of the voltage fault components and the current fault components at two sides of the line is as follows:
Wherein, The positive sequence voltage fault component and the negative sequence voltage fault component of the side are respectively; The current fault component is a positive sequence current fault component at the side and a negative sequence current fault component at the side respectively; θ m +、θm - is the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side, and the phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the current side;
The voltage fault components are respectively opposite positive sequence voltage fault components and opposite negative sequence voltage fault components; /(I) The fault components are opposite positive sequence current fault components and opposite negative sequence current fault components respectively; θ n +、θn - is the phase difference between the opposite positive sequence voltage fault component and the positive sequence current fault component, and the opposite negative sequence voltage fault component and the negative sequence current fault component, respectively.
S40: and calculating the difference value of the phase differences of the two sides according to the phase differences of the voltage fault components and the current fault components of the two sides of the line.
The difference value calculation formula of the phase difference at two sides is as follows:
wherein delta theta is the difference value of the phase difference of the two sides; the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side and the opposite side is respectively; /(I) The phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the side and the opposite side respectively; k +、K- is a positive sequence weight coefficient and a negative sequence weight coefficient, respectively, satisfying 0.ltoreq.k +≤1,0≤K-≤1,K++K- =1.
S50: and calculating a braking coefficient according to the difference value of the phase differences of the two sides.
The calculation formula of the braking coefficient is as follows:
Wherein K r is a brake coefficient; k rmin、Krmax is a minimum limit value and a maximum limit value of a brake coefficient respectively, wherein K rmin＜Krmax is more than 0 and less than 1; delta theta is the difference of the phase difference of the two sides; Δθ set1、Δθset2 is a first difference threshold and a second difference threshold, Δθ set1＜Δθset2; the function K r =f (|Δθ|) satisfies that when Δθ set1≤|Δθ|≤Δθset2, K r increases with an increase in |Δθ|.
In some embodiments, the function K r =f (|Δθ|) is a linear function, such as K r =f (|Δθ|) =a·|Δθ|+b, where a and b are constants, a+.0.
In some embodiments, the function K r =f (|Δθ|) is a nonlinear function, such as K r＝f(|Δθ|)＝c(|Δθ|)2 +d, where c and d are constants, c+.0. Such asWhere g and h are constants, g.noteq.0.
Such as K r =f (|Δθ|) = xarctan (y (|Δθ| -90 °)) +z, where x, y, and z are constants, x+.0, y+.0.
Fig. 3 shows an adjustment curve with a better differential protection braking coefficient, when |Δθ| is smaller, the probability of occurrence of an intra-area fault is higher, and a smaller braking coefficient can be set to obtain higher sensitivity, and as |Δθ| is continuously increased, the probability of occurrence of an intra-area fault is continuously reduced, and the probability of occurrence of an extra-area fault is continuously increased, so that the braking coefficient is increased, and differential protection misoperation caused by transformer saturation and the like during the extra-area fault is prevented.
Some embodiments further comprise: and forming a line differential protection criterion by the brake coefficient, the differential current and the brake current.
Differential currentBraking current/>, which is the sum of synchronous current phasors on both sidesIs the difference between synchronous current phasors at two sides.
Wherein,Is the current of the primary side phase; /(I)Is the opposite side current; /(I)Is a differential current; /(I)Is the braking current.
The braking characteristic equation of the line differential protection criterion is:
Wherein, K r is the braking coefficient, Is differential current,/>For braking current, I set is a differential threshold;
and judging that the vehicle is in the zone fault when the braking characteristic equation is satisfied, and judging that the vehicle is out of the zone fault otherwise.
Fig. 4 is a schematic diagram of a differential protection braking characteristic, in which a differential action threshold I set is set in order to prevent differential protection malfunction caused by an out-of-zone fault or an unbalanced current during normal operation, and a braking coefficient of the braking characteristic can adaptively change between K rmin and K rmax according to a difference between a voltage fault component and a current fault component phase difference on both sides of a line, and an in-zone fault is determined when the differential current and the braking current fall in a shaded portion in the figure, and an out-of-zone fault is determined otherwise.
As shown in fig. 5, a line differential protection device 600 includes: a data acquisition unit 610, a fault component calculation unit 620, a voltage-current phase difference calculation unit 630, a difference calculation unit 640, a brake coefficient calculation unit 650, and a fault determination unit 660, wherein:
the data acquisition unit 610 is used for acquiring synchronous voltage and synchronous current at the protection installation place at two sides of the line;
A fault component calculating unit 620 for calculating a voltage fault component and a current fault component on both sides of the line based on the synchronous voltage and the synchronous current on both sides of the line;
a voltage-current phase difference calculating unit 630, configured to calculate a phase difference between the voltage fault component and the current fault component on two sides of the line according to the voltage fault component and the current fault component;
A difference calculating unit 640 for calculating a difference of the phase differences of the two sides according to the phase differences of the voltage fault components and the current fault components of the two sides of the line;
A brake coefficient calculating unit 650 for calculating a brake coefficient according to the difference value of the phase differences of the both sides;
the fault determination unit 660 is configured to perform fault determination according to the brake coefficient and the line differential protection criterion.
The apparatus performs the same functions as the methods provided above, and other functions may be found in the foregoing description and will not be repeated here.
Fig. 6 shows a block diagram of an electronic device according to an example embodiment.
An electronic device 700 according to this embodiment of the application is described below with reference to fig. 6. The electronic device 700 shown in fig. 6 is merely an example, and should not be construed as limiting the functionality and scope of use of embodiments of the present application.
As shown in fig. 6, the electronic device 700 is embodied in the form of a general purpose computing device. Components of electronic device 700 may include, but are not limited to: at least one processing unit 710, at least one memory unit 720, a bus 730 connecting the different system components (including the memory unit 720 and the processing unit 710), a display unit 740, and the like.
In which a storage unit stores program codes that can be executed by the processing unit 710, so that the processing unit 710 performs the methods according to various exemplary embodiments of the present application described in the present specification.
The memory unit 720 may include readable media in the form of volatile memory units, such as Random Access Memory (RAM) 7201 and/or cache memory 7202, and may further include Read Only Memory (ROM) 7203.
The storage unit 720 may also include a program/utility 7204 having a set (at least one) of program modules 7205, such program modules 7205 including, but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of which may include an implementation of a network environment.
Bus 730 may be a bus representing one or more of several types of bus structures including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.
The electronic device 700 may also communicate with one or more external devices 700' (e.g., keyboard, pointing device, bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 700, and/or any device (e.g., router, modem, etc.) that enables the electronic device 700 to communicate with one or more other computing devices. Such communication may occur through an input/output (I/O) interface 750. Also, electronic device 700 may communicate with one or more networks such as a Local Area Network (LAN), a Wide Area Network (WAN) and/or a public network, such as the Internet, through network adapter 760. Network adapter 760 may communicate with other modules of electronic device 700 via bus 730. It should be appreciated that although not shown, other hardware and/or software modules may be used in connection with electronic device 700, including, but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, data backup storage systems, and the like.
From the above description of embodiments, those skilled in the art will readily appreciate that the example embodiments described herein may be implemented in software, or may be implemented in software in combination with the necessary hardware. The technical solution according to the embodiment of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (may be a CD-ROM, a usb disk, a mobile hard disk, etc.) or on a network, and includes several instructions to cause a computing device (may be a personal computer, a server, or a network device, etc.) to perform the above-described method according to the embodiment of the present application.
The software product may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The computer readable storage medium may include a data signal propagated in baseband or as part of a carrier wave, with readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A readable storage medium may also be any readable medium that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a readable storage medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Program code for carrying out operations of the present application may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server. In the case of remote computing devices, the remote computing device may be connected to the user computing device through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computing device (e.g., connected via the Internet using an Internet service provider).
Those skilled in the art will appreciate that the modules may be distributed throughout several devices as described in the embodiments, and that corresponding variations may be implemented in one or more devices that are unique to the embodiments. The units of the above embodiments may be combined into one unit or may be further split into a plurality of sub-units.
The present invention is not limited by the above embodiments, the description of the above embodiments is only for helping to understand the core idea of the present invention, and any modification made in the specific embodiments and application scope should be included in the scope of protection of the present invention, where the modification or equivalent substitution is made according to the idea of the present invention.
Claims (7)
1. A method for adjusting a brake coefficient of differential protection of a line, comprising:
Collecting synchronous voltage and synchronous current at the protection installation positions on two sides of the line;
Calculating voltage fault components and current fault components on two sides of the line based on the synchronous voltage and synchronous current on two sides of the line;
calculating the phase difference between the voltage fault components and the current fault components on two sides of the line according to the voltage fault components and the current fault components; the phase difference calculation formula of the voltage fault components and the current fault components at two sides of the line is as follows:
Wherein, The positive sequence voltage fault component and the negative sequence voltage fault component of the side are respectively; The current fault component is a positive sequence current fault component at the side and a negative sequence current fault component at the side respectively; θ m +、θm - is the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side, and the phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the current side; /(I) The voltage fault components are respectively opposite positive sequence voltage fault components and opposite negative sequence voltage fault components; /(I)The fault components are opposite positive sequence current fault components and opposite negative sequence current fault components respectively; θ n +、θn - is the phase difference between the opposite side positive sequence voltage fault component and the positive sequence current fault component, and the opposite side negative sequence voltage fault component and the negative sequence current fault component, respectively;
Calculating the difference value of the phase differences of the two sides according to the phase differences of the voltage fault components and the current fault components of the two sides of the line; the difference value calculation formula of the phase difference of the two sides is as follows:
Wherein delta theta is the difference value of the phase difference of the two sides; k +、K- is a positive sequence weight coefficient and a negative sequence weight coefficient respectively, and 0-K +≤1,0≤K-≤1,K++K- =1 is satisfied;
Calculating a braking coefficient according to the difference value of the phase differences of the two sides; the calculation formula of the braking coefficient is as follows:
Wherein K r is a brake coefficient; k rmin、Krmax is a minimum limit value and a maximum limit value of the braking coefficient respectively, K rmin＜Krmax＜1;Δθset1、Δθset2 is a first difference value threshold value and a second difference value threshold value, and delta theta set1＜Δθset2 is more than 0; the function K r =f (|Δθ|) satisfies that when Δθ set1≤|Δθ|≤Δθset2, K r increases with an increase in |Δθ|;
And constructing a line differential protection criterion according to the brake coefficient to carry out fault judgment.
2. The method for adjusting a brake coefficient for line differential protection according to claim 1, wherein,
The calculating the voltage fault component and the current fault component on the two sides of the line based on the synchronous voltage and the synchronous current on the two sides of the line comprises:
calculating positive sequence components and negative sequence components of the voltages and the currents at two sides according to a symmetrical component method based on the synchronous voltages and the synchronous currents at two sides of the circuit;
the two-sided voltage fault component and the current fault component are calculated based on the positive sequence component and the negative sequence component of the two-sided voltage and current.
3. The line differential protection brake coefficient adjustment method according to claim 1, wherein the voltage fault components include a positive sequence voltage fault component, a negative sequence voltage fault component; the current fault components include a positive sequence current fault component and a negative sequence current fault component.
4. The method for adjusting a brake coefficient for line differential protection according to claim 1, wherein,
The function K r =f (|Δθ|) is a linear function or a nonlinear function.
5. The method for adjusting a brake coefficient for line differential protection according to claim 1, wherein the brake coefficient, together with the differential current and the brake current, forms a line differential protection criterion,
The differential current is the sum of synchronous current phasors at two sides, the braking current is the difference of the synchronous current phasors at two sides,
The braking characteristic equation of the line differential protection criterion is:
Wherein, K r is the braking coefficient, Is differential current,/>For braking current, I set is a differential threshold;
and judging that the vehicle is in the zone fault when the braking characteristic equation is satisfied, and judging that the vehicle is out of the zone fault otherwise.
6. The utility model provides a circuit differential protection device which characterized in that includes data acquisition unit, trouble component calculation unit, voltage current phase difference calculation unit, brake coefficient calculation unit and trouble judgement unit, wherein:
The data acquisition unit is used for acquiring synchronous voltage and synchronous current at the protection installation positions on two sides of the line;
A fault component calculation unit for calculating a voltage fault component and a current fault component on both sides of the line based on the synchronous voltage and the synchronous current on both sides of the line;
the voltage-current phase difference calculation unit is used for calculating the phase difference between the voltage fault component and the current fault component at two sides of the line according to the voltage fault component and the current fault component; the phase difference calculation formula of the voltage fault components and the current fault components at two sides of the line is as follows:
Wherein, The positive sequence voltage fault component and the negative sequence voltage fault component of the side are respectively; The current fault component is a positive sequence current fault component at the side and a negative sequence current fault component at the side respectively; θ m +、θm - is the phase difference between the positive sequence voltage fault component and the positive sequence current fault component of the current side, and the phase difference between the negative sequence voltage fault component and the negative sequence current fault component of the current side; /(I) The voltage fault components are respectively opposite positive sequence voltage fault components and opposite negative sequence voltage fault components; /(I)The fault components are opposite positive sequence current fault components and opposite negative sequence current fault components respectively; θ n +、θn - is the phase difference between the opposite side positive sequence voltage fault component and the positive sequence current fault component, and the opposite side negative sequence voltage fault component and the negative sequence current fault component, respectively;
The difference value calculation unit is used for calculating the difference value of the phase differences at two sides according to the phase differences of the voltage fault components and the current fault components at two sides of the line; the difference value calculation formula of the phase difference of the two sides is as follows:
Wherein delta theta is the difference value of the phase difference of the two sides; k +、K- is a positive sequence weight coefficient and a negative sequence weight coefficient respectively, and 0-K +≤1,0≤K-≤1,K++K- =1 is satisfied;
a brake coefficient calculating unit for calculating a brake coefficient according to the difference value of the phase differences of the two sides; the calculation formula of the braking coefficient is as follows:
Wherein K r is a brake coefficient; k rmin、Krmax is a minimum limit value and a maximum limit value of the braking coefficient respectively, K rmin＜Krmax＜1;Δθset1、Δθset2 is a first difference value threshold value and a second difference value threshold value, and delta theta set1＜Δθset2 is more than 0; the function K r =f (|Δθ|) satisfies that when Δθ set1≤|Δθ|≤Δθset2, K r increases with an increase in |Δθ|;
And the fault judging unit is used for judging faults according to the line differential protection criterion formed by the brake coefficients.
7. An electronic device, comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor being operative according to the instructions to perform the steps of the method according to any one of claims 1 to 5.
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