A method and device for evaluating the performance of a relay protection action

Abstract

The application discloses a kind of relay protection action performance evaluation method and device.Therein, method includes: the action equation of differential current and braking current is constructed by cosine theorem, and protection action boundary function is constructed based on the action equation constructed;The scene of control strategy change is classified, according to the result of classification and the time variation factor of control strategy, construct the evaluation function for evaluating the performance of protection action;Based on protection action boundary function and evaluation function, the variation range of the phase angle difference on the both sides of fault phase current is determined;Based on the variation range of phase angle difference, the action boundary of relay protection is determined.

Description

Technical Field

[0001] This invention relates to the field of protection technology for new energy transmission systems, and more specifically, to a method and apparatus for evaluating the performance of relay protection actions. Background Technology

[0002] With the increasing proportion of new energy sources such as wind power and photovoltaics, and the continuous expansion of the power grid, my country's new power system faces severe challenges to security. It is projected that by 2025, my country's total installed power capacity will reach 2.95 billion kilowatts, with wind and solar power accounting for 540 million and 560 million kilowatts respectively; by 2030, the total installed power capacity will reach 3.8 billion kilowatts, with wind and solar power accounting for 800 million and 1.025 billion kilowatts respectively. By 2050, the total installed capacity will reach 7.5 billion kilowatts, with wind and solar power becoming the main drivers of increased power capacity, accounting for over 75% of installed capacity and over 65% of power generation. By 2060, the total installed capacity will reach 8 billion kilowatts, with wind and solar power accounting for nearly 80% of installed capacity and over 70% of power generation. A high proportion of new energy sources has become a key characteristic of the new power system.

[0003] From the power supply side, renewable energy sources have become the main source of fault current. The transient process of short-circuit current provided by renewable energy is no longer simply constrained by electromagnetic physics, but rather by a dual constraint of electromagnetic physics and nonlinear control. The fault transient process is closely related to the control strategy and parameters of renewable energy converters, resulting in limited short-circuit current amplitude, controlled phase angle, and significantly increased non-characteristic harmonic content. Furthermore, the different types of renewable energy units, their varying control and fault ride-through strategies, the different distances of each type of unit from the collection bus, and the different grid connection locations of renewable energy units further exacerbate the phase angle-controlled characteristics of the fault. This poses a threat to the reliability and sensitivity of traditional relay protection based on power frequency quantities, leading to risks of false tripping and failure to trip. Therefore, it is necessary to propose a relay protection performance evaluation method to clearly define the boundary that ensures the correct operation of the main protection sent from renewable energy power plants, and to assess the renewable energy access capacity range that can guarantee the correct operation of relay protection and safe grid operation. This has significant engineering implications for high-proportion renewable energy consumption and safe grid operation.

[0004] The short-circuit current transient process provided by new energy sources is no longer simply constrained by electromagnetic physics. The fault transient process is closely related to the control strategy and parameters of the new energy converter, causing changes in the characteristic quantities used in traditional protection, and consequently leading to a decline in the operating performance of traditional protection. Therefore, there is currently a lack of a relay protection operating performance evaluation method that can clearly identify whether there is a risk of failure or false tripping of line protection in the new energy transmission system, provide protection evaluation schemes for the field, and provide technical support for engineering recommendations and commissioning. Summary of the Invention

[0005] To address the technical problem of the lack of a relay protection performance evaluation method in the existing technology that can clearly determine whether there is a risk of failure or maloperation of line protection in the new energy transmission system, the present invention provides a relay protection performance evaluation method and device.

[0006] According to one aspect of the present invention, a method for evaluating the operating performance of relay protection is provided, comprising:

[0007] The operating equations for differential current and braking current are constructed using the law of cosines, and the boundary functions for protection operation are constructed based on these equations.

[0008] The scenarios in which control strategies change are classified, and an evaluation function for assessing the performance of protective actions is constructed based on the classification results and the time-varying factors of control strategies.

[0009] Based on the protection action boundary function and evaluation function, the range of variation of the phase angle difference on both sides of the fault phase current is determined;

[0010] The operating boundary of the relay protection is determined based on the range of phase angle difference.

[0011] Optionally, the operating equations for the differential current and braking current are constructed using the cosine theorem, including:

[0012] The protection action equation for the ratio-restrained current differential protection is determined as follows:

[0013]

[0014] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the phase currents of the same name at the protection installation points on the outgoing line substation side and the system side, respectively, with the positive direction pointing from the busbar to the line; I op0 is the starting value; k is the braking coefficient;

[0015] Based on the parallelogram law, the differential current I is expressed using the cosine theorem. d and braking current I r ,Right now:

[0016] I d 2 =I W 2 +I S 2 -2IW I S cos(π-θ C )

[0017] I r 2 =I W 2 +I S 2 -2I W I S cosθ C (2)

[0018] In the formula, θc represents I W with I S The angle between the two currents, i.e., the time-varying phase angle difference between the two currents; I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line;

[0019] Substituting formula (2) into the protection action equation Id>kIr in formula (1), and setting the short-circuit capacity ratio of the currents on both sides to 1:x, i.e., the formula IS=xIW holds true, then the action equations for the differential current and the braking current are:

[0020]

[0021] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line.

[0022] Optionally, a protection action boundary function is constructed based on the constructed action equation, including:

[0023] Substituting formula (2) into formula (3), and simplifying it to a function with multiple variables, we get:

[0024] f(x,θC ,k)=(1-k 2 )x 2 +(2+2k 2 cosθ C x+(1-k 2 (4)

[0025] According to formula (4), when the function f(x,θc,k) is greater than 0, it represents protection action; when f(x,θc,k) is less than zero, it represents protection failure.

[0026] Take the partial derivative of the function f(x,θc,k) with respect to k, and analyze the effect of the variable k on the function f(x,θc,k):

[0027]

[0028] Among them, it can be seen from formula (5) that the partial derivative of the function f(x,θc,k) is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable k increases;

[0029] Take the partial derivative of the function f(x,θc,k) with respect to θc, and analyze the effect of the variable θc on the function f(x,θc,k):

[0030]

[0031] Among them, it can be seen from formula (6) that the function f(x,θc,k) after partial derivative is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable θc increases;

[0032] Based on formula (4), it is determined that different failure-to-operate boundaries will be generated under different braking coefficients k. When the phase angle difference on both sides of the fault phase current satisfies the following formula (7), failure-to-operate is possible:

[0033]

[0034] The verification of whether the protection device will fail to operate is based on the short-circuit capacity ratio x of the protection device to be evaluated. It is found that the protection will fail to operate when the short-circuit capacity ratio satisfies the following formula (8):

[0035]

[0036] When the short-circuit capacity ratio satisfies the following formula (9), the protection can operate normally and will not fail to operate:

[0037]

[0038] In equations (7), (8) and (9), k is the braking coefficient of the protection device to be evaluated; x is the short-circuit capacity ratio x of the protection device to be evaluated; and θc is the phase angle difference between the two sides of the fault phase current.

[0039] Optionally, the scenarios of control strategy changes are categorized, and based on the categorization results and the time-varying factors of the control strategy, an evaluation function is constructed to assess the performance of protective actions, including:

[0040] Based on the different control response speeds of different converters in the new energy system, the change process of the phase angles on both sides is classified into two cases: same-direction operation and reverse-direction operation. V1 represents the average operating speed of the change of the current phase angle on the flexible DC side, and V2 represents the average operating speed of the change of the current phase angle on the wind farm side.

[0041] Based on the time it takes for the phase angle to reach the action boundary, the same-direction and opposite-direction cases are each further subdivided into two cases: the first and the second time the boundary is reached. The following four evaluation functions are constructed to assess the performance of the protection action:

[0042]

[0043]

[0044]

[0045]

[0046] Among them, formulas (10)-(13) are respectively the evaluation functions for the first arrival at the boundary in the same direction, the first arrival at the boundary in the opposite direction, the second arrival at the boundary in the same direction, and the second arrival at the boundary in the opposite direction; θ0 is the initial phase angle difference between the currents on both sides; θc is the time-varying phase angle difference between the currents on both sides; t represents the time for the phase angle to reach θc under different conditions.

[0047] Optionally, based on the protection action boundary function and evaluation function, the range of variation of the phase angle difference on both sides of the fault phase current is determined, including:

[0048] Using formulas (7), (8) and (9), calculate the short-circuit capacity ratio x of the protection device and the time-varying phase angle difference θc of the currents on both sides;

[0049] Substitute the protection's operating time t, the calculated short-circuit capacity ratio x, and the time-varying phase angle difference θc into formulas (10) to (13) to determine the range of variation of the phase angle difference on both sides of the fault phase current.

[0050] Optionally, the operating boundaries of the relay protection are determined based on the range of phase angle difference variation, including:

[0051] Based on the range of phase angle difference, it is determined that when the absolute value of the controller adjustment speed difference satisfies the following formula (14), the protection is at risk of failure to operate:

[0052]

[0053] That is, all corresponding situations have the risk of failure to operate within the range of formula (14);

[0054] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (15), the protection will operate normally:

[0055]

[0056] That is, all corresponding cases protect normal operation within the range of formula (15);

[0057] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (16), the protection system is at risk of failing to operate:

[0058]

[0059] That is, all corresponding cases are protected against the risk of non-operation within the range of formula (16).

[0060] According to another aspect of the present invention, a relay protection operation performance evaluation device is provided, comprising:

[0061] The first construction module is used to construct the action equations of differential current and braking current using the cosine theorem, and to construct the protection action boundary function based on the constructed action equations.

[0062] The second construction module is used to classify the scenarios of control strategy changes, and construct an evaluation function to evaluate the performance of protection actions based on the classification results and the time-varying factors of the control strategy.

[0063] The variation range determination module is used to determine the variation range of the phase angle difference on both sides of the fault phase current based on the protection action boundary function and the evaluation function.

[0064] The action boundary determination module is used to determine the action boundary of relay protection based on the range of phase angle difference variation.

[0065] 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.

[0066] 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.

[0067] Therefore, this invention proposes a method for evaluating the action performance of relay protection. It constructs the action equations for differential current and braking current using the cosine theorem, thereby clarifying the boundary function of protection action. Then, it classifies scenarios of control strategy changes and introduces the time-varying process of the control strategy to establish a function for evaluating protection action performance. Using this new function, it calculates the rate of change of phase angle difference, revealing the range of phase angle difference variation. Finally, based on the range of phase angle difference variation, it clarifies the protection action boundary, achieving the evaluation of protection action performance. This invention ultimately clarifies whether there are problems with the protection of transmission lines from new energy power plants, providing on-site protection evaluation schemes and technical support for engineering recommendations and commissioning. This invention provides a quantitative calculation formula for engineering applications, thereby evaluating protection action performance. The formula proposed in this invention can calculate the action boundary, thus evaluating the protection action performance. This invention can evaluate whether there are problems with the protection of flexible DC transmission lines from new energy power plants, clarifying the requirements for reliable protection action. The principle of this invention is clear, and the computational load is small, making it particularly suitable for systems where short-circuit current is controlled by power electronic equipment on both sides. Attached Figure Description

[0068] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0069] Figure 1 This is a flowchart illustrating a relay protection action performance evaluation method provided in an exemplary embodiment of the present invention;

[0070] Figure 2 This is a schematic diagram illustrating the relationship between differential current and braking current provided in an exemplary embodiment of the present invention;

[0071] Figure 3 This is a schematic diagram illustrating the range of phase angle difference provided in an exemplary embodiment of the present invention;

[0072] Figure 4(a) is a schematic diagram of the protection operation when there is an intra-zone fault and the short-circuit capacity ratio boundary is 1:1.28, according to an exemplary embodiment of the present invention.

[0073] Figure 4(b) is a schematic diagram of the phase angle situation after an external fault and when the short-circuit capacity ratio boundary is 1:1.28, provided by an exemplary embodiment of the present invention;

[0074] Figure 5(a) is a schematic diagram of the protection operation when there is an intra-zone fault and the short-circuit capacity ratio boundary is 1:1.45, according to an exemplary embodiment of the present invention.

[0075] Figure 5(b) is a schematic diagram of the phase angle situation after an external fault and when the short-circuit capacity ratio boundary is 1:1.45, provided by an exemplary embodiment of the present invention.

[0076] Figure 6(a) is a schematic diagram of the protection operation after an external fault provided in an exemplary embodiment of the present invention;

[0077] Figure 6(b) is a schematic diagram of the phase angle situation after an external fault provided by an exemplary embodiment of the present invention;

[0078] Figure 7 This is a schematic diagram of the structure of a relay protection operation performance evaluation device provided in an exemplary embodiment of the present invention;

[0079] Figure 8 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0080] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0081] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0082] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0083] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0084] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0085] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0086] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0087] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0088] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0089] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0090] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0091] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0092] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0093] Exemplary methods

[0094] Figure 1 This is a flowchart illustrating a relay protection operation performance evaluation method provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as... Figure 1 As shown, the relay protection operation performance evaluation method 100 includes the following steps:

[0095] Step 101: Construct the operating equations for differential current and braking current using the cosine theorem, and construct the protection action boundary function based on the constructed operating equations;

[0096] Optionally, the operating equations for the differential current and braking current are constructed using the cosine theorem, including:

[0097] The protection action equation for the ratio-restrained current differential protection is determined as follows:

[0098]

[0099] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the phase currents of the same name at the protection installation points on the outgoing line substation side and the system side, respectively, with the positive direction pointing from the busbar to the line; I op0 is the starting value; k is the braking coefficient;

[0100] in, Figure 2 An example diagram showing the relationship between differential current and braking current is provided.

[0101] It is worth noting that I op0 =kI set I set This is a "start-up" threshold for the main protection, and this value can be set manually. According to the regulations, in zero-sequence differential protection, I... op0 The sensitivity to clearing high-resistance grounding faults should be no less than 1.5; if there is no zero-sequence differential protection, the low-value section I of the phase-current differential protection should be used. op0 The sensitivity to clearing high-resistance grounding faults should be no less than 1.3. If zero-sequence differential protection is present, the low-value segment I of the phase-current differential protection should be provided. op0 The sensitivity for clearing high-resistance grounding faults is not less than 1; simultaneously, the high-value section I of the phase-separated current differential protection... op0 It should reliably avoid the steady-state capacitive current of the line (reliability factor not less than 4).

[0102] After the main protection "start" threshold is met, i.e., I d >I op0 If the equation holds true and satisfies the sensitivity requirement, according to the parallelogram law, the sum of two phasors with an included angle greater than 90 degrees is less than their difference, meaning the differential current is less than the braking current, which may lead to a failure to operate. Therefore, based on the parallelogram law, the differential current I is expressed using the cosine theorem. dand braking current I r ,Right now:

[0103] I d 2 =I W 2 +I S 2 -2I W I S cos(π-θ C )

[0104] I r 2 =I W 2 +I S 2 -2I W I S cosθ C (2)

[0105] In the formula, θc represents I W with I S The angle between the two currents, i.e., the time-varying phase angle difference between the two currents; I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line;

[0106] Substituting formula (2) into the protection action equation Id>kIr in formula (1), and setting the short-circuit capacity ratio of the currents on both sides to 1:x, i.e., the formula IS=xIW holds true, then the action equations for the differential current and the braking current are:

[0107]

[0108] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line.

[0109] Optionally, a protection action boundary function is constructed based on the constructed action equation, including:

[0110] Substituting formula (2) into formula (3), and simplifying it to a function with multiple variables, we get:

[0111] f(x,θ C ,k)=(1-k 2 )x 2 +(2+2k 2 cosθ C x+(1-k 2 (4)

[0112] According to formula (4), when the function f(x,θc,k) is greater than 0, it represents protection action; when f(x,θc,k) is less than zero, it represents protection failure.

[0113] Since the short-circuit capacity ratio x is always greater than 0, k∈[0.6,0.8] is always greater than 0, and θc∈(90,180) results in cosθc∈(0,-1), we can take the partial derivative of the function f(x,θc,k) with respect to k and analyze the effect of the variable k on the function f(x,θc,k):

[0114]

[0115] Among them, it can be seen from formula (5) that the partial derivative of the function f(x,θc,k) is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable k increases;

[0116] Take the partial derivative of the function f(x,θc,k) with respect to θc, and analyze the effect of the variable θc on the function f(x,θc,k):

[0117]

[0118] Among them, it can be seen from formula (6) that the function f(x,θc,k) after partial derivative is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable θc increases;

[0119] To maximize the area of ​​protection failure to operate, the braking coefficient k is set to 0.8. Substituting θc = 180 degrees into the function, we can obtain the maximum area where f(x,θc,k) < 0, which is the maximum area of ​​protection failure. At this time, x = 9, that is, the short-circuit capacity ratio is 1:9. Therefore, it can be known that when the short-circuit capacity ratio is greater than 1:9, the function f(x,θc,k) > 0, that is, the protection will definitely operate correctly.

[0120] During application, the braking coefficient k of different protection devices may vary. Therefore, to evaluate the operating performance of the protection device, it is necessary to substitute the actual k value of the device to be estimated into formula (4). At this time, formula (4) is the relationship between the short-circuit capacity ratio and the phase angle difference. Then, substitute the actual short-circuit capacity ratio into the formula to obtain the value of the phase angle difference. Finally, determine whether the protection will fail to operate. The details are as follows:

[0121] Based on formula (4), it is determined that different failure-to-operate boundaries will be generated under different braking coefficients k. When the phase angle difference on both sides of the fault phase current satisfies the following formula (7), failure-to-operate is possible:

[0122]

[0123] The verification of whether the protection device will fail to operate is based on the short-circuit capacity ratio x of the protection device to be evaluated. It is found that the protection will fail to operate when the short-circuit capacity ratio satisfies the following formula (8):

[0124]

[0125] When the short-circuit capacity ratio satisfies the following formula (9), the protection can operate normally and will not fail to operate:

[0126]

[0127] In equations (7), (8) and (9), k is the braking coefficient of the protection device to be evaluated; x is the short-circuit capacity ratio x of the protection device to be evaluated; and θc is the phase angle difference between the two sides of the fault phase current.

[0128] Step 102: Classify the scenarios of control strategy changes, and construct an evaluation function to assess the performance of protective actions based on the classification results and the time-varying factors of the control strategy.

[0129] Optionally, the scenarios of control strategy changes are categorized, and based on the categorization results and the time-varying factors of the control strategy, an evaluation function is constructed to assess the performance of protective actions, including:

[0130] Based on the different control response speeds of different converters in the new energy system, the change process of the phase angles on both sides is classified into two cases: same-direction operation and reverse-direction operation. V1 represents the average operating speed (control adjustment speed) of the change of the current phase angle on the flexible DC side, and V2 represents the average operating speed (control adjustment speed) of the change of the current phase angle on the wind farm side.

[0131] Based on the time it takes for the phase angle to reach the action boundary, the same-direction and opposite-direction cases are each further subdivided into two cases: the first and the second time the boundary is reached. The following four evaluation functions are constructed to assess the performance of the protection action:

[0132]

[0133]

[0134]

[0135]

[0136] Among them, formulas (10)-(13) are respectively the evaluation functions for the first arrival at the boundary in the same direction, the first arrival at the boundary in the opposite direction, the second arrival at the boundary in the same direction, and the second arrival at the boundary in the opposite direction; θ0 is the initial phase angle difference between the currents on both sides; θc is the time-varying phase angle difference between the currents on both sides; t represents the time for the phase angle to reach θc under different conditions.

[0137] Step 103: Based on the protection action boundary function and evaluation function, determine the range of variation of the phase angle difference on both sides of the fault phase current;

[0138] Optionally, based on the protection action boundary function and evaluation function, the range of variation of the phase angle difference on both sides of the fault phase current is determined, including:

[0139] Using formulas (7), (8) and (9), calculate the short-circuit capacity ratio x of the protection device and the time-varying phase angle difference θc of the currents on both sides;

[0140] Substituting the protection's expected operating time t, the calculated short-circuit capacity ratio x, and the time-varying phase angle difference θc into formulas (10) to (13), the range of variation of the phase angle difference on both sides of the fault phase current is determined (e.g., Figure 3 (As shown).

[0141] Step 104: Determine the operating boundary of the relay protection based on the range of phase angle difference variation.

[0142] Optionally, the operating boundaries of the relay protection are determined based on the range of phase angle difference variation, including:

[0143] Based on the range of phase angle difference, it is determined that when the absolute value of the controller adjustment speed difference satisfies the following formula (14), the protection is at risk of failure to operate:

[0144]

[0145] That is, all corresponding situations have the risk of failure to operate within the range of formula (14);

[0146] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (15), the protection will operate normally:

[0147]

[0148] That is, all corresponding cases protect normal operation within the range of formula (15);

[0149] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (16), the protection system is at risk of failing to operate:

[0150]

[0151] That is, all corresponding cases are protected against the risk of non-operation within the range of formula (16).

[0152] In this embodiment of the invention, x and θc calculated by formulas (7)-(9) are substituted into formulas (10)-(13) respectively, and the protection should be substituted according to the action time t. Finally, four boundary ranges can be obtained, that is, the boundary where the protection may have the risk of not acting can be divided into three intervals.

[0153] The following analysis, using a new energy power transmission system via a flexible DC converter as an example and in conjunction with Figures 4(a) to 6(b), focuses on the AC lines during the process of connecting new energy power sources to the flexible DC converter, to verify the relay protection action performance evaluation method proposed in this invention.

[0154] Figures 4(a) and 4(b) show the operation and phase angle of the protection when there is a fault within the zone, the short-circuit capacity ratio is 1:1.28, and k = 0.8. Through theoretical calculation, substituting the short-circuit capacity ratio boundary of 1:1.28 and k = 0.8 into the proposed function yields an angle of 103 degrees. Then, substituting 103 degrees and the protection's required operation time (t = 30 ms) into the proposed function, the absolute value of the speed difference within 30 ms is calculated to be 8.64 degrees / ms. Based on the phase angle change being clockwise downwards and counterclockwise upwards, and the failure-to-operate boundary being between 2.56 degrees / ms and 9.43 degrees / ms, 8.64 degrees / ms falls within this range. Therefore, the protection can operate correctly. Assuming the protection needs to activate within 6ms, the failure-to-activate boundary is between 12.83 degrees / ms and 47.17 degrees / ms. The calculated absolute value of the velocity difference within 30ms is 8.64 degrees / ms, which means it is not within the correct activation range. At this point, there is a risk of failure to activate within 6ms, thus verifying the correctness of the theory.

[0155] Figures 5(a) and 5(b) show the operation and phase angle of the protection during an in-zone fault with a short-circuit capacity ratio of 1:1.45 and k = 0.8. Through theoretical calculation, substituting the short-circuit capacity ratio boundary of 1:1.45 and k = 0.8 into the proposed function yields an angle of 103.5 degrees. Then, substituting 103.5 degrees and the protection's required operation time (t = 30 ms) into the proposed function, the absolute value of the speed difference within 30 ms is calculated to be 8.49 degrees / ms. Based on the fact that the phase angle changes are sequential and the correct operation boundary is between 2.56 degrees / ms and 9.43 degrees / ms, 8.64 degrees / ms falls within this range. Therefore, the protection operates correctly within 30 ms, thus verifying the correctness of the theory.

[0156] Figures 6(a) and 6(b) show the operation and phase angle situations when there is an external fault, the short-circuit capacity ratio is 1, and k = 0.8. Through theoretical calculation, substituting the short-circuit capacity ratio boundary of 1 and k = 0.8 into the proposed function, the operating boundary angle is obtained as 102.68 degrees. Then, substituting 102.68 degrees and the protection's required operating time (t = 30 ms) into the proposed function, the absolute value of the speed difference within 30 ms is calculated to be 0.018 degrees / ms. Based on the phase angle change and the fact that the protection operates in the same direction, and the failure-to-operate boundary is between 2.58 degrees / ms and 9.42 degrees / ms, meaning 0.018 degrees / ms is outside this range, there is a risk of the protection failing to operate. As can be seen from the figures, the protection consistently fails to operate within 30 ms, thus verifying the correctness of the theory.

[0157] Therefore, the relay protection action performance evaluation method proposed in this invention constructs the action equations for differential current and braking current using the cosine theorem, thereby clarifying the protection action boundary function. Then, it classifies the scenarios of control strategy changes and introduces the time-varying process of the control strategy to establish a function for evaluating protection action performance. Using this newly established function, it calculates the rate of change of phase angle difference, revealing the range of phase angle difference variation. Finally, based on the range of phase angle difference variation, it clarifies the protection action boundary, achieving the evaluation of protection action performance. This invention ultimately clarifies whether there are problems with the protection of the transmission lines from new energy power plants, providing on-site protection evaluation schemes and technical support for engineering recommendations and commissioning. This invention provides a quantitative calculation formula for engineering applications, thereby evaluating protection action performance. The formula proposed in this invention can calculate the action boundary, thus evaluating the protection action performance. This invention can evaluate whether there are problems with the protection of new energy power plants via flexible DC transmission lines, clarifying the requirements for reliable protection action. The principle of this invention is clear, the calculation is small, and it is particularly suitable for systems where the short-circuit current is controlled by power electronic equipment on both sides.

[0158] Exemplary System

[0159] Figure 7 This is a schematic diagram of the structure of a relay protection operation performance evaluation device provided in an exemplary embodiment of the present invention. Figure 7 As shown, the device 700 includes:

[0160] The first construction module 710 is used to construct the action equations of differential current and braking current through the cosine theorem, and to construct the protection action boundary function based on the constructed action equations;

[0161] The second construction module 720 is used to classify the scenarios of control strategy changes, and construct an evaluation function to evaluate the performance of protection actions based on the classification results and the time-varying factors of the control strategy.

[0162] The variation range determination module 730 is used to determine the variation range of the phase angle difference on both sides of the fault phase current based on the protection action boundary function and the evaluation function.

[0163] The action boundary determination module 740 is used to determine the action boundary of the relay protection based on the range of phase angle difference.

[0164] Optionally, the first building module 710 is specifically used for:

[0165] The protection action equation for the ratio-restrained current differential protection is determined as follows:

[0166]

[0167] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the phase currents of the same name at the protection installation points on the outgoing line substation side and the system side, respectively, with the positive direction pointing from the busbar to the line; I op0 is the starting value; k is the braking coefficient;

[0168] Based on the parallelogram law, the differential current I is expressed using the cosine theorem. d and braking current I r ,Right now:

[0169] I d 2 =I W 2 +I S 2 -2I W I S cos(π-θ C )

[0170] I r 2 =I W 2 +I S 2 -2I W I S cosθ C (2)

[0171] In the formula, θc represents I W with I S The angle between the two currents, i.e., the time-varying phase angle difference between the two currents; I dFor differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line;

[0172] Substituting formula (2) into the protection action equation Id>kIr in formula (1), and setting the short-circuit capacity ratio of the currents on both sides to 1:x, i.e., the formula IS=xIW holds true, then the action equations for the differential current and the braking current are:

[0173]

[0174] In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line.

[0175] Optionally, the first building module 710 is also specifically used for:

[0176] Substituting formula (2) into formula (3), and simplifying it to a function with multiple variables, we get:

[0177] f(x,θ C ,k)=(1-k 2 )x 2 +(2+2k 2 cosθ C x+(1-k 2 (4)

[0178] According to formula (4), when the function f(x,θc,k) is greater than 0, it represents protection action; when f(x,θc,k) is less than zero, it represents protection failure.

[0179] Take the partial derivative of the function f(x,θc,k) with respect to k, and analyze the effect of the variable k on the function f(x,θc,k):

[0180]

[0181] Among them, it can be seen from formula (5) that the partial derivative of the function f(x,θc,k) is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable k increases;

[0182] Take the partial derivative of the function f(x,θc,k) with respect to θc, and analyze the effect of the variable θc on the function f(x,θc,k):

[0183]

[0184] Among them, it can be seen from formula (6) that the function f(x,θc,k) after partial derivative is less than 0, that is, the function f(x,θc,k) decreases monotonically as the variable θc increases;

[0185] Based on formula (4), it is determined that different failure-to-operate boundaries will be generated under different braking coefficients k. When the phase angle difference on both sides of the fault phase current satisfies the following formula (7), failure-to-operate is possible:

[0186]

[0187] The verification of whether the protection device will fail to operate is based on the short-circuit capacity ratio x of the protection device to be evaluated. It is found that the protection will fail to operate when the short-circuit capacity ratio satisfies the following formula (8):

[0188]

[0189] When the short-circuit capacity ratio satisfies the following formula (9), the protection can operate normally and will not fail to operate:

[0190]

[0191] In equations (7), (8) and (9), k is the braking coefficient of the protection device to be evaluated; x is the short-circuit capacity ratio x of the protection device to be evaluated; and θc is the phase angle difference between the two sides of the fault phase current.

[0192] Optionally, the second building module 720 is specifically used for:

[0193] Based on the different control response speeds of different converters in the new energy system, the change process of the phase angles on both sides is classified into two cases: same-direction operation and reverse-direction operation. V1 represents the average operating speed of the change of the current phase angle on the flexible DC side, and V2 represents the average operating speed of the change of the current phase angle on the wind farm side.

[0194] Based on the time it takes for the phase angle to reach the action boundary, the same-direction and opposite-direction cases are each further subdivided into two cases: the first and the second time the boundary is reached. The following four evaluation functions are constructed to assess the performance of the protection action:

[0195]

[0196]

[0197]

[0198]

[0199] Among them, formulas (10)-(13) are respectively the evaluation functions for the first arrival at the boundary in the same direction, the first arrival at the boundary in the opposite direction, the second arrival at the boundary in the same direction, and the second arrival at the boundary in the opposite direction; θ0 is the initial phase angle difference between the currents on both sides; θc is the time-varying phase angle difference between the currents on both sides; t represents the time for the phase angle to reach θc under different conditions.

[0200] Optionally, the variation range determination module 730 is specifically used for:

[0201] Using formulas (7), (8) and (9), calculate the short-circuit capacity ratio x of the protection device and the time-varying phase angle difference θc of the currents on both sides;

[0202] Substitute the protection's operating time t, the calculated short-circuit capacity ratio x, and the time-varying phase angle difference θc into formulas (10) to (13) to determine the range of variation of the phase angle difference on both sides of the fault phase current.

[0203] Optionally, the action boundary determination module 740 is specifically used for:

[0204] Based on the range of phase angle difference, it is determined that when the absolute value of the controller adjustment speed difference satisfies the following formula (14), the protection is at risk of failure to operate:

[0205]

[0206] That is, all corresponding situations have the risk of failure to operate within the range of formula (14);

[0207] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (15), the protection will operate normally:

[0208]

[0209] That is, all corresponding cases protect normal operation within the range of formula (15);

[0210] When the absolute value of the speed difference adjusted by the controller satisfies the following formula (16), the protection system is at risk of failing to operate:

[0211]

[0212] That is, all corresponding cases are protected against the risk of non-operation within the range of formula (16).

[0213] The relay protection operation performance evaluation device 700 of this invention corresponds to the relay protection operation performance evaluation method 100 of another embodiment of this invention, and will not be described again here.

[0214] Exemplary electronic devices

[0215] Figure 8 This is the structure of an electronic device provided in an exemplary 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, which may communicate with the first device and the second device to receive acquired input signals from them. Figure 8 A block diagram of an electronic device according to an embodiment of the present invention is illustrated. Figure 8 As shown, the electronic device 80 includes one or more processors 81 and memory 82.

[0216] The processor 81 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.

[0217] The memory 82 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 81 may execute the program instructions to implement the methods for information mining of historical change records and / or other desired functions of the software programs of the various embodiments of the present invention described above. In one example, the electronic device may also include an input system 83 and an output system 84, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0218] In addition, the input system 83 may also include, for example, a keyboard, a mouse, etc.

[0219] The output system 84 can output various types of information to the outside. The output device 84 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0220] Of course, for the sake of simplicity, Figure 8Only some of the components of the electronic device relevant to the present invention 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.

[0221] Exemplary computer program products and computer-readable storage media

[0222] In addition to the methods and devices described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods for information mining of historical change records according to various embodiments of the present invention as described in the "Exemplary Methods" section of this specification.

[0223] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. 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 the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0224] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods for information mining of historical change records according to various embodiments of the present invention as described in the "Exemplary Methods" section above.

[0225] 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 be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: 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), optical storage device, magnetic storage device, or any suitable combination thereof.

[0226] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0227] 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.

[0228] The block diagrams of devices, systems, devices, and systems involved in this invention 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, systems, 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.

[0229] The methods and systems of the present invention 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 the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0230] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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.

[0231] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention 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 therein.

Claims

1. A method for evaluating the operating performance of relay protection, characterized in that, include: The operating equations for differential current and braking current are constructed using the law of cosines, and the boundary functions for protection operation are constructed based on these equations. The equations of action for differential current and braking current are constructed using the law of cosines, including: The protection action equation for the ratio-restrained current differential protection is determined as follows: (1) In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the phase currents of the same name at the protection installation points on the outgoing line substation side and the system side, respectively, with the positive direction pointing from the busbar to the line; I op0 is the starting value; k is the braking coefficient; Based on the parallelogram law, the differential current I is expressed using the cosine theorem. d and braking current I r ,Right now: (2) In the formula, θ c represents I W with I S The angle between the two currents, i.e., the time-varying phase angle difference between the two currents; I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line; Substituting formula (2) into the protection action equation Id > kIr in formula (1), and setting the short-circuit capacity ratio of the currents on both sides to 1:x, i.e., the formula IS=xIW holds true, then the action equations for the differential current and the braking current are: (3) In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line; Substituting formula (2) into formula (3), and simplifying it to a function with multiple variables, we get: (4) According to formula (4), it can be clearly seen that when the function f(x) ,θ When c,k) is greater than 0, it represents a protective action, f(x) ,θ When c,k) is less than zero, it indicates that the protection fails to activate; The scenarios in which control strategies change are classified, and an evaluation function for assessing the performance of protective actions is constructed based on the classification results and the time-varying factors of control strategies. Based on the protection action boundary function and evaluation function, the range of variation of the phase angle difference on both sides of the fault phase current is determined; The operating boundary of the relay protection is determined based on the range of phase angle difference.

2. The method according to claim 1, characterized in that, Based on the constructed action equations, the protection action boundary function is constructed, including: The function f(x) ,θ Take the partial derivative of c,k with respect to k, and analyze the variable k with respect to the function f(x). ,θ The role of c,k): (5) Among them, the partial derivative function f(x) is obtained from formula (5). ,θ c,k) is less than 0, that is, the function f(x) ,θ c,k) decreases monotonically as the variable k increases; The function f(x) ,θ c,k) for θ Find the partial derivative of c and analyze the variables. θ c for the function f(x) ,θ The role of c,k): (6) Among them, the partial derivative function f(x) is obtained from formula (6). ,θ c,k) is less than 0, that is, the function f(x) ,θ c, k) with the variables θ The increase of c is monotonically decreasing; Based on formula (4), it is determined that different failure-to-operate boundaries will be generated under different braking coefficients k. When the phase angle difference on both sides of the fault phase current satisfies the following formula (7), failure-to-operate is possible: （7） The verification of whether the protection device will fail to operate is based on the short-circuit capacity ratio x of the protection device to be evaluated. It is found that the protection will fail to operate when the short-circuit capacity ratio satisfies the following formula (8): （8） When the short-circuit capacity ratio satisfies the following formula (9), the protection can operate normally and will not fail to operate: （9） In equations (7), (8), and (9), k is the braking coefficient of the protection device to be evaluated; x is the short-circuit capacity ratio x of the protection device to be evaluated. θ c represents the phase angle difference between the two sides of the fault phase current.

3. The method according to claim 2, characterized in that, The scenarios involving changes in control strategies are categorized. Based on the categorization results and the time-varying factors of control strategies, an evaluation function is constructed to assess the performance of protective actions, including: Based on the different control response speeds of different converters in new energy systems, the change process of the phase angles on both sides is classified into two cases: same-direction operation and reverse-direction operation, where V... 1 V represents the average operating speed of the change in phase angle of the flexible DC side current. 2 This represents the average operating speed of the change in the phase angle of the current on the wind farm side; Based on the time it takes for the phase angle to reach the action boundary, the same-direction and opposite-direction cases are each further subdivided into two cases: the first and the second time the boundary is reached. The following four evaluation functions are constructed to assess the performance of the protection action: （10） （11） （12） （13） Among them, formulas (10) to (13) are respectively the evaluation functions for the first time reaching the boundary in the same direction, the first time reaching the boundary in the opposite direction, the second time reaching the boundary in the same direction, and the second time reaching the boundary in the opposite direction; θ 0 represents the initial phase angle difference between the currents on both sides; θ c represents the time-varying phase angle difference between the currents on both sides; t represents the phase angle reaching its maximum value under different conditions. θ The time of c.

4. The method according to claim 3, characterized in that, Based on the protection action boundary function and evaluation function, the range of variation of the phase angle difference on both sides of the fault phase current is determined, including: Using formulas (7), (8) and (9), calculate the short-circuit capacity ratio x of the protection device and the time-varying phase angle difference θc of the currents on both sides; Substitute the calculated short-circuit capacity ratio x and time-varying phase angle difference θc into formulas (10) to (13) to determine the range of phase angle difference on both sides of the fault phase current.

5. The method according to claim 4, characterized in that, Based on the range of phase angle difference, the operating boundaries of the relay protection are determined, including: Based on the range of phase angle difference, it is determined that when the absolute value of the controller adjustment speed difference satisfies the following formula (14), the protection is at risk of failure to operate: （14） That is, all corresponding situations have the risk of failure to operate within the range of formula (14); When the absolute value of the speed difference adjusted by the controller satisfies the following formula (15), the protection will operate normally: （15） That is, all corresponding cases protect normal operation within the range of formula (15); When the absolute value of the speed difference adjusted by the controller satisfies the following formula (16), the protection system is at risk of failing to operate: （16） That is, all corresponding cases are protected against the risk of non-operation within the range of formula (16).

6. A relay protection operation performance evaluation device, characterized in that, include: The first construction module is used to construct the action equations of differential current and braking current using the cosine theorem, and to construct the protection action boundary function based on the constructed action equations. The equations of action for differential current and braking current are constructed using the law of cosines, including: The protection action equation for the ratio-restrained current differential protection is determined as follows: (1) In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the phase currents of the same name at the protection installation points on the outgoing line substation side and the system side, respectively, with the positive direction pointing from the busbar to the line; I op0 is the starting value; k is the braking coefficient; Based on the parallelogram law, the differential current I is expressed using the cosine theorem. d and braking current I r ,Right now: (2) In the formula, θ c represents I W with I S The angle between the two currents, i.e., the time-varying phase angle difference between the two currents; I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line; Substituting formula (2) into the protection action equation Id > kIr in formula (1), and setting the short-circuit capacity ratio of the currents on both sides to 1:x, i.e., the formula IS=xIW holds true, then the action equations for the differential current and the braking current are: (3) In the formula, I d For differential current, I r For the braking current, respectively satisfy I d =|I W +I S |,I r =|I W –I S |;I W and I S These are the same phase currents at the protection installation points on the sending line station side and the system side, respectively, with the positive direction pointing from the busbar to the line; Substituting formula (2) into formula (3), and simplifying it to a function with multiple variables, we get: (4) According to formula (4), it can be clearly seen that when the function f(x) ,θ When c,k) is greater than 0, it represents a protective action, f(x) ,θ When c,k) is less than zero, it indicates that the protection fails to activate; The second construction module is used to classify the scenarios of control strategy changes, and construct an evaluation function to evaluate the performance of protection actions based on the classification results and the time-varying factors of the control strategy. The variation range determination module is used to determine the variation range of the phase angle difference on both sides of the fault phase current based on the protection action boundary function and the evaluation function. The action boundary determination module is used to determine the action boundary of relay protection based on the range of phase angle difference variation.

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 1-5.

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 described in any one of claims 1-5.

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