Phasor differential protection adaptability quantitative evaluation method and system

Abstract

The invention discloses a phasor differential protection adaptability quantitative evaluation method and system, and the method comprises the steps: obtaining the current data of a fault line, and constructing a fault current mathematical model based on the current data at two sides of a fault position; the differential current and the braking current are defined based on a fault mathematical model and used for detecting the fault condition and preventing the protection device from malfunctioning under the non-fault condition; and a differential protection action criterion is preset based on the differential current and the braking current, a differential protection action boundary is obtained through calculation, and the differential protection adaptability is quantitatively evaluated through the differential protection action boundary. According to the method, the differential current and the braking current are redefined based on short-circuit comparison, and a quantitative expression of a differential protection action boundary is further given, so that a worker can conveniently evaluate the adaptability of differential protection in different scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection, and in particular to a phasor differential protection adaptability quantitative evaluation method and system. Background Art

[0002] Differential protection is based on Kirchhoff's current theorem. It uses the relationship between the current directions on both sides when there are faults inside and outside the zone to construct differential quantity and braking quantity. It is widely used in the system as the main protection of line protection, transformer protection, busbar protection and other devices. In the traditional synchronous machine system, the fault currents on both sides are in the same direction when there is a fault inside the zone, and the differential protection can act sensitively. However, with the extensive application of power electronic equipment such as new energy and flexible direct current converter stations in the system, the phase of the fault current shows obvious controlled characteristics, causing the currents on both sides to show through characteristics when there is a fault inside the zone, which seriously affects the sensitivity of the differential protection and even has the risk of refusal to act. However, the existing technology lacks effective quantitative evaluation indicators for this risk, and it is impossible to give the differential protection adaptation boundary in a targeted manner, which brings troubles to the application of differential protection in engineering implementation. Therefore, it is urgent to propose a quantitative evaluation method for the adaptability of differential protection that can guide engineering applications and is easy to implement. Summary of the invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a phasor differential protection adaptability quantitative evaluation method and system to solve the problem that the adaptability boundary cannot be quantified when the sensitivity of the existing new energy access line is insufficient and the phasor differential protection is insufficient.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a method for quantitatively evaluating adaptability of a phasor differential protection, comprising: acquiring current data of a fault line, and constructing a fault current mathematical model based on current data on both sides of the fault location;

[0008] Defining a differential current and a restraining current based on the fault mathematical model for detecting fault conditions and preventing malfunction of protection devices under non-fault conditions;

[0009] A differential protection action criterion is preset based on the differential current and the braking current, and a differential protection action boundary is calculated. The differential protection adaptability is quantitatively evaluated through the differential protection action boundary.

[0010] As a preferred solution of the quantitative evaluation method for adaptability of phasor differential protection described in the present invention, wherein: constructing a fault current mathematical model through current data on both sides of the fault location includes: the phasor value of the phase current measured at the location of the protection device on this side is recorded as The phase current of the same name measured by the opposite side protection device is expressed as:

[0011]

[0012] Where λ is the ratio of the short-circuit capacity on the opposite side to the short-circuit capacity on the local side, i.e., the short-circuit ratio and λ≥0, θ I is the phase angle difference between the currents on both sides.

[0013] As a preferred scheme of the quantitative evaluation method of the adaptability of the phasor differential protection described in the present invention, wherein: defining the differential current and the braking current based on the fault mathematical model includes: based on the currents on both sides of the protection device, the short-circuit ratio and the phase angle difference between the currents on both sides, defining the differential current as the modulus length of the sum of the phasors of the currents on both sides, and defining the braking current as the modulus length of the phasor difference of the currents on both sides.

[0014] As a preferred solution of the phasor differential protection adaptability quantitative evaluation method described in the present invention, it also includes:

[0015] The differential current is expressed as:

[0016]

[0017] The braking current is expressed as:

[0018]

[0019] As a preferred solution of the phasor differential protection adaptability quantitative evaluation method described in the present invention, wherein: the differential protection action criterion preset based on the differential current and the braking current includes: when the current on both sides of the protection device is abnormal and the differential current is greater than the product of the braking current and the ratio braking coefficient, the protection action is triggered; if the differential current is not greater than the product of the braking current and the ratio braking coefficient, no action protection is performed;

[0020] The differential protection action criterion is:

[0021] I d >K r I r

[0022] Among them, K ris the ratio braking coefficient.

[0023] As a preferred solution of the phasor differential protection adaptability quantitative evaluation method of the present invention, wherein: calculating the differential protection action boundary includes: based on the differential protection action criterion, the differential protection action boundary is expressed by the ratio relationship between the short-circuit capacity on the opposite side and the short-circuit capacity on the local side as:

[0024]

[0025] Among them, λ TH is the short circuit ratio threshold.

[0026] As a preferred solution of the method for quantitatively evaluating the adaptability of phasor differential protection described in the present invention, wherein: through the differential protection action boundary, quantitatively evaluating the adaptability of differential protection includes:

[0027] If the short-circuit ratio on both sides is greater than the short-circuit ratio threshold, the differential protection can operate reliably;

[0028] If the short-circuit ratio on both sides is less than the short-circuit ratio threshold, there is a risk of differential protection failure.

[0029] In a second aspect, the present invention provides a phasor differential protection adaptability quantitative evaluation system, comprising:

[0030] A mathematical model building module is used to obtain the current data of the fault line and construct a fault current mathematical model based on the current data on both sides of the fault location;

[0031] A fault detection and protection module, used to define a differential current and a braking current based on the fault mathematical model, for detecting fault conditions and preventing malfunction of the protection device under non-fault conditions;

[0032] The quantitative evaluation module is used to preset the differential protection action criterion based on the differential current and the braking current, and calculate the differential protection action boundary, and quantitatively evaluate the adaptability of the differential protection through the differential protection action boundary.

[0033] In a third aspect, the present invention provides a computing device, comprising:

[0034] Memory and processor;

[0035] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the phasor differential protection adaptability quantitative evaluation method are implemented.

[0036] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for quantitatively evaluating the adaptability of phasor differential protection.

[0037] Compared with the prior art, the present invention has the following beneficial effects: the present invention redefines the differential current and the braking current based on the short-circuit ratio, and further provides a quantitative expression for the action boundary of the differential protection, which facilitates the staff to evaluate the adaptability of the differential protection in different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0039] Figure 1 The present invention is a flowchart of a method and system for quantitatively evaluating the adaptability of a phasor differential protection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0043] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0044] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0045] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Example 1

[0047] Reference Figure 1 , is an embodiment of the present invention, which provides a phasor differential protection adaptability quantitative evaluation method, including:

[0048] S100: Acquire current data of the fault line, and construct a fault current mathematical model based on the current data on both sides of the fault location;

[0049] In the embodiment of the present application, the fault current mathematical model is constructed by using the current data on both sides of the fault position, including: the phasor value of the phase current measured at the location of the protection device on this side is recorded as The phase current of the same name measured by the opposite side protection device is expressed as:

[0050]

[0051] Where λ is the ratio of the short-circuit capacity on the opposite side to the short-circuit capacity on the local side, i.e., the short-circuit ratio and λ≥0, θ I is the phase angle difference between the currents on both sides.

[0052] It should be noted that the fault type in the embodiment of the present application may be a short circuit fault.

[0053] S200: defining a differential current and a braking current based on a fault mathematical model, for detecting a fault condition and preventing a protection device from malfunctioning under a non-fault condition;

[0054] In an embodiment of the present application, defining the differential current and the braking current based on the fault mathematical model includes: based on the currents on both sides of the protection device, the short-circuit ratio and the phase difference between the currents on both sides, defining the differential current as the modulus of the sum of the current phasors on both sides, and defining the braking current as the modulus of the difference between the current phasors on both sides.

[0055] In the embodiment of the present application, it also includes:

[0056] The differential current is expressed as:

[0057]

[0058] The braking current is expressed as:

[0059]

[0060] S300: Presetting a differential protection action criterion based on the differential current and the braking current, and calculating the differential protection action boundary, and quantitatively evaluating the adaptability of the differential protection through the differential protection action boundary;

[0061] In the embodiment of the present application, the differential protection action criterion preset based on the differential current and the braking current includes: when the current on both sides of the protection device is abnormal and the differential current is greater than the product of the braking current and the ratio braking coefficient, the protection action is triggered; if the differential current is not greater than the product of the braking current and the ratio braking coefficient, no action protection is performed;

[0062] The differential protection action criterion is:

[0063] I d >K r I r

[0064] Among them, K r is the ratio braking coefficient.

[0065] It should be noted that the embodiment of the present application adjusts the sensitivity and safety of the differential protection by setting the ratio braking coefficient, and the ratio braking coefficient can be selected to be 0.6.

[0066] It should be noted that the differential protection action boundary is based on the differential protection action criterion and is calculated in combination with the differential current and the braking current. This inequality is expressed as:

[0067]

[0068] In the embodiment of the present application, calculating the differential protection action boundary includes: based on the differential protection action criterion, expressing the differential protection action boundary by the ratio of the opposite side short-circuit capacity to the local side short-circuit capacity as:

[0069]

[0070] Among them, λ TH is the short circuit ratio threshold.

[0071] In the embodiment of the present application, quantitatively evaluating the adaptability of the differential protection through the differential protection action boundary includes:

[0072] If the short-circuit ratio on both sides is greater than the short-circuit ratio threshold, the differential protection can operate reliably;

[0073] If the short-circuit ratio on both sides is less than the short-circuit ratio threshold, there is a risk of differential protection failure.

[0074] It should be noted that the present invention redefines the differential current and the braking current based on the short-circuit ratio, and further provides a quantitative expression for the action boundary of the differential protection, which is convenient for the staff to evaluate the adaptability of the differential protection in different scenarios.

[0075] The above is a schematic scheme of a phasor differential protection adaptability quantitative evaluation method of this embodiment. It should be noted that the technical scheme of this phasor differential protection adaptability quantitative evaluation system and the technical scheme of the phasor differential protection adaptability quantitative evaluation method mentioned above belong to the same concept, and the details of the technical scheme of the phasor differential protection adaptability quantitative evaluation system not described in detail in this embodiment can be referred to the description of the technical scheme of the phasor differential protection adaptability quantitative evaluation method mentioned above.

[0076] In this embodiment, a phasor differential protection adaptability quantitative evaluation system includes:

[0077] A mathematical model building module is used to obtain the current data of the fault line and construct a fault current mathematical model based on the current data on both sides of the fault location;

[0078] A fault detection protection module, which is used to define the differential current and the braking current based on the fault mathematical model, and is used to detect the fault condition and prevent the protection device from malfunctioning under non-fault conditions;

[0079] The quantitative evaluation module is used to preset the differential protection action criterion based on the differential current and the braking current, and calculate the differential protection action boundary. Through the differential protection action boundary, the adaptability of the differential protection is quantitatively evaluated.

[0080] This embodiment further provides a computing device, which is applicable to the case of the phasor differential protection adaptability quantitative evaluation method, including:

[0081] Memory and processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the quantitative evaluation method for adaptability of phasor differential protection proposed in the above embodiment.

[0082] This embodiment further provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for quantitatively evaluating the adaptability of phasor differential protection proposed in the above embodiment is implemented.

[0083] The storage medium proposed in this embodiment and the method for realizing quantitative evaluation of adaptability of phasor differential protection proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0084] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0085] Example 2

[0086] Referring to Table 1, it is an embodiment of the present invention. This embodiment is different from the first embodiment in that this embodiment takes the AC line of the new energy station access system as an example to verify the feasibility of the quantitative evaluation of the adaptability of the differential protection of the present invention.

[0087] In this embodiment, under the worst working condition, the maximum phase angle difference of the fault phase current on both sides can reach 150°. Under this working condition, the ratio braking coefficient K r and differential protection action boundary λ TH The relationship is shown in Table 1:

[0088] Table 1 Ratio braking coefficient K r Differential protection action short circuit ratio limit λ TH Correspondence

[0089]

[0090]

[0091] Referring to Table 1, the ratio braking coefficient K of the conventional phasor differential protection in this embodiment is r It is generally 0.6, that is, when the ratio of the short-circuit capacity on the opposite side to the short-circuit capacity on this side λ is greater than 3.4, the differential protection can operate reliably and the protection can adapt; if λ is less than 3.4, the differential protection will refuse to operate and the protection will not adapt.

[0092] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A phasor differential protection adaptability quantitative evaluation method, characterized in that: include: Obtain the current data of the fault line, and construct a fault current mathematical model based on the current data on both sides of the fault location; Defining a differential current and a restraining current based on the fault mathematical model for detecting fault conditions and preventing malfunction of protection devices under non-fault conditions; A differential protection action criterion is preset based on the differential current and the braking current, and a differential protection action boundary is calculated. The differential protection adaptability is quantitatively evaluated through the differential protection action boundary.

2. The phasor differential protection adaptability quantitative evaluation method according to claim 1, characterized in that: The fault current mathematical model is constructed by using the current data on both sides of the fault location. The phasor value of the phase current measured at the location of the protection device on this side is recorded as The phase current of the same name measured by the opposite side protection device is expressed as: Where λ is the ratio of the short-circuit capacity on the opposite side to the short-circuit capacity on the local side, i.e., the short-circuit ratio and λ≥0, θ I is the phase angle difference between the currents on both sides.

3. The phasor differential protection adaptability quantitative evaluation method according to claim 2, characterized in that: Defining the differential current and the braking current based on the fault mathematical model includes: based on the currents on both sides of the protection device, the short-circuit ratio and the phase angle difference of the currents on both sides, defining the differential current as the module length of the sum of the current phasors on both sides, and defining the braking current as the module length of the difference between the current phasors on both sides.

4. The phasor differential protection adaptability quantitative evaluation method according to claim 3, characterized in that: Also includes: The differential current is expressed as: The braking current is expressed as:

5. The phasor differential protection adaptability quantitative evaluation method according to claim 4, characterized in that: The differential protection action criterion preset based on the differential current and the braking current includes: when the current on both sides of the protection device is abnormal and the differential current is greater than the product of the braking current and the ratio braking coefficient, the protection action is triggered; if the differential current is not greater than the product of the braking current and the ratio braking coefficient, no action protection is performed; The differential protection action criterion is: I d >K r I r Among them, K r is the ratio braking coefficient.

6. The phasor differential protection adaptability quantitative evaluation method according to claim 5, characterized in that: Calculating the differential protection action boundary includes: based on the differential protection action criterion, expressing the differential protection action boundary by the ratio of the opposite side short-circuit capacity to the local side short-circuit capacity as: Among them, λ TH is the short circuit ratio threshold.

7. The phasor differential protection adaptability quantitative evaluation method according to claim 6, characterized in that: Through the differential protection action boundary, quantitative evaluation of differential protection adaptability includes: If the short-circuit ratio on both sides is greater than the short-circuit ratio threshold, the differential protection can operate reliably; If the short-circuit ratio on both sides is less than the short-circuit ratio threshold, the differential protection will be at risk of failure to operate.

8. A phasor differential protection adaptability quantitative evaluation system, characterized in that: include: A mathematical model building module is used to obtain the current data of the fault line and construct a fault current mathematical model based on the current data on both sides of the fault location; A fault detection and protection module, used to define a differential current and a braking current based on the fault mathematical model, for detecting fault conditions and preventing malfunction of the protection device under non-fault conditions; The quantitative evaluation module is used to preset the differential protection action criterion based on the differential current and the braking current, and calculate the differential protection action boundary, and quantitatively evaluate the adaptability of the differential protection through the differential protection action boundary.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the phasor differential protection adaptability quantitative evaluation method described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for quantitatively evaluating the adaptability of phasor differential protection as described in any one of claims 1 to 7.

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