Weak feed side differential current voltage auxiliary starting method and device

Abstract

The application is suitable for the technical field of power system, and provides a weakly fed side differential current voltage auxiliary starting method and device, which comprises the following steps: obtaining a current amplitude parameter of a line local side and obtaining a current amplitude parameter of a line opposite side; calculating a differential current amplitude between the line local side and the line opposite side according to the current amplitude parameter of the line local side and the current amplitude parameter of the line opposite side; obtaining a composite voltage of the line; judging whether the line satisfies a preset weakly fed side starting condition according to the differential current amplitude and the composite voltage, and if yes, performing a weakly fed side starting operation. According to the differential current amplitude and the composite voltage, whether the line satisfies the preset weakly fed side starting condition is judged, and the problem that the differential protection refuses to act when the weakly fed side cannot start due to high resistance ground fault of the line is solved.

Description

Technical Field

[0001] This application belongs to the field of power system technology, and in particular relates to a method and device for differential voltage-assisted starting of weak feeder side. Background Technology

[0002] With the continuous development of power systems, power lines frequently change between tie lines and terminal lines. When a line is a terminal line, one end becomes the load side, which has no power supply or only a small, weak power supply. In this case, when a high-resistance ground fault occurs, the fault current increases slowly. The power supply side experiences a relatively obvious fault characteristic and can be activated by conventional current surge or zero-sequence current activation. However, the weak feeder side does not experience obvious fault characteristics, and the current remains basically unchanged. It cannot be activated by current surge or zero-sequence current activation, resulting in the weak feeder side failing to activate, and the differential protection on both sides failing to operate. Summary of the Invention

[0003] This application provides a differential voltage-assisted starting method and device for weak feeder side, which can solve the problem that when a high-resistance ground fault occurs on a terminal line, the fault current increases slowly, but the weak feeder side does not feel obvious fault characteristics, resulting in the differential protection failing to operate.

[0004] In a first aspect, embodiments of this application provide a weak feed-side differential current voltage-assisted startup method, including:

[0005] Obtain the current amplitude parameters on this side of the line and the current amplitude parameters on the opposite side of the line;

[0006] The differential current amplitude between the local and opposite sides of the line is calculated based on the current amplitude parameters on the local side and the current amplitude parameters on the opposite side of the line.

[0007] Obtain the composite voltage of the line; based on the differential current amplitude and the composite voltage, determine whether the line meets the preset weak feeder side start-up conditions; if it does, perform the weak feeder side start-up operation.

[0008] In one possible implementation of the first aspect, the preset weak feed-side activation condition includes:

[0009] The differential current amplitude is greater than the preset differential operating current setting; and the zero-sequence voltage in the composite voltage is greater than one voltage unit volt or the negative-sequence voltage in the composite voltage is greater than three voltage units volt.

[0010] For example, the current amplitude parameters include the fundamental amplitude, the second harmonic amplitude, and the third harmonic amplitude. The step of calculating the differential current amplitude between the local and opposite sides of the line based on the current amplitude parameters on the local side and the current amplitude parameters on the opposite side of the line includes:

[0011] The fundamental wave differential current amplitude of the line is calculated based on the fundamental wave amplitude on this side of the line and the fundamental wave amplitude on the opposite side of the line; the second harmonic differential current amplitude of the line is calculated based on the second harmonic amplitude on this side of the line and the second harmonic amplitude on the opposite side of the line; and the third harmonic differential current amplitude of the line is calculated based on the third harmonic amplitude on this side of the line and the third harmonic amplitude on the opposite side of the line.

[0012] Determine whether the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter. If so, the fundamental differential current amplitude is taken as the differential current amplitude between the local side and the opposite side of the line.

[0013] In another possible implementation of the first aspect, the preset weak feed-side start-up condition further includes the sampled differential current being greater than the preset differential operating current setting.

[0014] Secondly, embodiments of this application provide a weak-feed-side differential current voltage-assisted start-up device, comprising:

[0015] The acquisition module is used to acquire the phase currents of each phase at the beginning of the line and the phase currents of each phase at the end of the line, the secondary currents of the line and the opposite side, the composite voltage of the line, and to calculate the differential current amplitude and sampled differential current of each phase current on the current side and the phase current on the opposite side based on the acquired data.

[0016] The judgment module is used to determine whether the differential current amplitude and the sampled differential current meet the differential current criterion, whether the composite voltage meets the voltage criterion, whether the line meets the opposite side start criterion, and send the judgment result of starting the weak feeder side protection.

[0017] The action module receives the judgment result and activates the weak feed-side protection based on the judgment result.

[0018] Thirdly, embodiments of this application provide a terminal device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the weak feed-side differential current voltage-assisted startup method as described in any of the first aspects above.

[0019] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the weak feed-side differential current voltage-assisted startup method as described in any one of the first aspects above.

[0020] Fifthly, embodiments of this application provide a computer program product that, when run on a terminal device, causes the terminal device to execute the weak feed-side differential current voltage-assisted startup method described in any of the first aspects above.

[0021] It is understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0022] The beneficial effects of the embodiments in this application compared with the prior art are:

[0023] In this embodiment, the circuit is judged to meet the preset weak feeder start-up conditions based on the differential current amplitude and composite voltage, thus solving the problem that the weak feeder cannot start when a high-resistance ground fault occurs in the line, causing the differential protection to fail to operate.

[0024] In this embodiment of the application, the differential current of the secondary current is obtained by sampling, and the line is judged to meet the preset weak feeder side start-up conditions based on the differential current of the sampling value, thereby improving the accuracy of the judgment and preventing false start-up.

[0025] Of course, any product implementing this application does not necessarily need to achieve all of the advantages described above at the same time.

[0026] The above description is merely an overview of the technical solution of this application. In order to better understand the technical means of this invention, it can be implemented according to the contents of the specification. Furthermore, in order to make the purpose, features and advantages of this application more obvious and understandable, specific embodiments of this application are described below. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of a line protection device provided in an embodiment of this application;

[0029] Figure 2 This is a schematic flowchart of a weak feed-side differential current voltage-assisted startup method provided in an embodiment of this application;

[0030] Figure 3 This is a flowchart illustrating a method for calculating the differential current amplitude between the local and opposite sides of a line according to an embodiment of this application.

[0031] Figure 4This is a structural block diagram of a weak feed-side differential voltage-assisted starting device provided in an embodiment of this application. Detailed Implementation

[0032] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0033] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0034] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0036] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0038] When the line is a terminal line, one end becomes the load side. The load side has no power supply or a small, weak power supply. When a high-resistance ground fault occurs, the fault current increases slowly. The weak feeder side does not perceive obvious fault characteristics, and the current remains basically unchanged. It cannot be started by current surge or zero-sequence current, resulting in the weak feeder side failing to start. Consequently, the differential protection on both the weak feeder side and the power supply side fails to operate. This application aims to provide a weak feeder side differential current voltage-assisted starting method that enables the weak feeder side to start normally when a high-resistance ground fault occurs, thereby realizing differential protection.

[0039] The differential current voltage-assisted starting method for weak feeder side provided in this application embodiment can be applied to terminal equipment such as line protection devices. When the terminal equipment is a line protection device, the line protection device can also be a general term for equipment used in protection and measurement and control at interval units of various voltage levels, possessing functions such as protection, control, measurement, communication, and monitoring.

[0040] Taking the terminal device as an example, which is a line protection device. Figure 1 The diagram shown is a block diagram of a portion of the structure of the line protection device provided in the embodiments of this application. (Reference) Figure 1 The line protection device includes components such as a measuring element 100, a logic element 200, and an execution element 300. The measuring element 100, the logic element 200, and the execution element 300 transmit data signals via wired or wireless means.

[0041] Specifically, the measuring element 100 includes a set of logic signals with properties of "0" or "1", such as "yes", "no", "greater than", and "not greater than", input from the protected object to measure relevant physical quantities (such as current, voltage, impedance, power direction, etc.) and compare them with given settings. Based on the comparison results, it determines whether the protection should be activated.

[0042] Specifically, logic element 200, based on the magnitude, nature, logical state, order of occurrence, or combination thereof of the output quantity from the measurement section, causes the protection device to operate according to certain Boolean logic and timing logic, ultimately determining whether to trip or send a signal, and transmitting the relevant command to the execution element. Logic circuits include OR, AND, NOT, delayed start, delayed return, and memory, etc.

[0043] Optionally, logic element 200 includes a processor and memory. The processor may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0044] Optionally, in some embodiments, the memory may be an internal storage unit, such as a hard disk or RAM. In other embodiments, the memory may be an external storage device, such as a plug-in hard disk, a smart media card (SMC), a secure digital card (SD), a flash card, etc. Furthermore, the memory may include both internal storage units and external storage devices. The memory is used to store the operating system, program code of computer programs, etc. The memory can also be used to temporarily store data that has been output or will be output.

[0045] Specifically, the actuator 300 completes the task assigned to the protection device based on the signals transmitted by the logic element. For example, it trips the circuit breaker during a fault; sends a signal during abnormal operation; and does not operate during normal operation.

[0046] Optionally, the actuator 300 may include an electromagnet, an electromagnetic clutch, a relay, etc.

[0047] Those skilled in the art will understand that Figure 1 The line protection device structure shown does not constitute a limitation on the line protection device, and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0048] The weak feed side differential current voltage-assisted start-up method provided in this application will be described exemplarily below with reference to specific embodiments. Figure 2 A flowchart illustrating a weak feeder side differential voltage-assisted start-up method according to an embodiment of this application is provided. This is an example and not a limitation, and the method can be applied to the above-mentioned line protection device.

[0049] Step S201: Obtain the current amplitude parameters on this side of the line and obtain the current amplitude parameters on the opposite side of the line.

[0050] In this embodiment, the current amplitude parameters include the fundamental amplitude, the second harmonic amplitude, and the third harmonic amplitude; using a relay protection device installed on the line side, the current of each phase on the line side and the current of each phase on the opposite side of the line are collected at a frequency of 24 points per cycle.

[0051] Understandably, the full-cycle Fourier transform algorithm can be used to calculate the amplitude and phase angle of each harmonic component, and it also has a certain filtering effect, effectively filtering out constant DC components and integer harmonic components. The full-cycle Fourier transform algorithm is used to calculate the fundamental current amplitude I of each phase on this side. m Second harmonic amplitude I 2m Third harmonic amplitude I 3m The fundamental amplitude I of each phase current on the opposite side n Second harmonic amplitude I 2n Third harmonic amplitude I 3n .

[0052] Step S202: Calculate the differential current amplitude between the line side and the opposite side based on the current amplitude parameters of the line side and the current amplitude parameters of the opposite side.

[0053] In one embodiment, to prevent false starts due to hardware failure, the differential current harmonic content is judged by a criterion. If the differential current harmonic content criterion is met, the differential current amplitude between the local side and the opposite side of the line is determined. If the differential current harmonic content criterion is not met, the weak feeder side is not started. Figure 3 The method flow for calculating the differential current amplitude between the local and opposite sides of the line in this application embodiment is given as an example and not a limitation. The specific steps are as follows:

[0054] S301: Based on the fundamental amplitude I on this side of the line m The fundamental amplitude I on the opposite side of the line n Calculate the fundamental differential current amplitude I of the line. d According to the second harmonic amplitude I on this side of the line 2m And the second harmonic amplitude I on the opposite side of the line 2n Calculate the second harmonic differential current amplitude I of the line. 2d And based on the third harmonic amplitude I on this side of the line 3m The amplitude of the third harmonic on the opposite side of the line I 3n Calculate the third harmonic differential current amplitude I of the line. 3d The specific calculation process can be performed using the following formula:

[0055] I d =I m +I n

[0056] I 2d =I 2m +I2n

[0057] I 3d =I 3m +I 3n

[0058] S302: Determine whether the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter. If so, the fundamental differential current amplitude is used as the differential current amplitude between this side and the opposite side of the line.

[0059] It is understandable that if the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is not less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter, then the line does not meet the preset weak feeder side start-up conditions and the weak feeder side start-up operation is not performed.

[0060] Specifically, a differential current harmonic content judgment element is used to determine whether the sum of the second and third harmonic differential current amplitudes is less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter. To ensure startup under weak feed conditions, the preset differential current harmonic parameter can be 0.15, that is, the differential current harmonic content criterion is: I 2d +I 3d <0.15I d .

[0061] As an example and not a limitation, the differential current harmonic content determination element uses a system-on-chip (SOC) processor, and the criteria are edited using the corresponding software development kit (SDK) compilation tools.

[0062] Step S203: Obtain the composite voltage of the line.

[0063] Specifically, the composite voltage of a line includes any one or both of zero-sequence voltage and negative-sequence voltage.

[0064] In this embodiment, the line is a three-phase line. Therefore, when there is an asymmetry in the line voltage and current, the asymmetric components of the three phases are decomposed into symmetrical components (positive and negative sequence) and zero-sequence components in the same direction. As an example and not a limitation, zero-sequence / negative-sequence voltage can be obtained by using a zero-sequence current / negative-sequence current filter.

[0065] Step S204: Based on the differential current amplitude and composite voltage, determine whether the line meets the preset weak feeder start-up conditions. If it does, then perform the weak feeder start-up operation.

[0066] In this embodiment, the preset weak feed-side start-up conditions include:

[0067] The differential current amplitude is greater than the preset differential operating current setting I. set ;as well as

[0068] In a composite voltage, the negative sequence voltage U2 is greater than one voltage unit volt, or the zero sequence voltage 3U0 is greater than three voltage units volt.

[0069] Specifically, a differential current detection element is used to determine whether the differential current amplitude is greater than the preset differential operating current setting I. set That is, the differential current criterion is: I d >I set .

[0070] It should be noted that, to ensure startup under weak feedback conditions, the differential current criterion is set to: I d >0.9I set .

[0071] Specifically, a composite voltage judgment element is used to determine whether the composite voltage meets the preset weak feed-side start-up conditions. The composite voltage criterion is: U2>1V; or 3U0>3V.

[0072] As an example and not a limitation, the differential current judgment element and the composite voltage judgment element mentioned above both use a SOC processor and the corresponding SDK compilation tools are used to edit the criteria.

[0073] In another embodiment, to improve the accuracy of the judgment and prevent false starts, the preset weak feed-side start condition further includes:

[0074] Sampling value differential current i d Greater than the preset differential operating current setting I set .

[0075] Specifically, the sampled differential current i d The calculation method is as follows:

[0076] (1) Obtain the secondary current on this side of the line and the secondary current on the opposite side of the line;

[0077] (2) The secondary current on this side of the line and the secondary current on the opposite side of the line are sampled at the same time, and the first current sample value i at each sampling point is obtained after analog-to-digital conversion. mp Second current sampling value i np (p = 0, 1, 2, ..., N-1); where p represents the current sampling point and N is the number of samples in one cycle, for example, N is 24.

[0078] Specifically, the secondary current on this side of the line is sampled to obtain the first current sampling value i. mp The second current sampling value i is obtained by sampling the secondary current on the opposite side of the line. np Each first current sample value has a corresponding second current sample value sampled at the same time.

[0079] (3) Calculate the sampled differential current i using the following formula. d :

[0080] i d =i mp +i np .

[0081] Correspondingly, the weak feed side differential current voltage-assisted start-up method also includes:

[0082] The sampled differential current i d With respect to the preset differential operating current setting I set If the sampled differential current is greater than the preset differential operating current setting I, then... set If the circuit meets the preset weak feed-side start-up conditions, then the circuit is determined to be in good condition.

[0083] Specifically, a differential current detection element is used to determine whether the sampled differential current is greater than the preset differential operating current setting I. set That is, the differential current criterion is: i d >I set .

[0084] It should be noted that, to ensure startup under weak feed conditions, the differential current criterion for the sampled value is set as follows: i d >0.9I set .

[0085] As an example and not a limitation, the above-mentioned differential current judgment element for sampled values ​​uses a SOC processor and the judgment criteria are edited using the corresponding SDK compilation tools.

[0086] In another embodiment, since the line is a three-phase line, each phase has a corresponding differential current amplitude and a sampled differential current. If only one phase in the three-phase circuit has a corresponding differential current amplitude and a sampled differential current that are both greater than the preset differential operating current setting, then the preset weak feeder start-up condition is determined to be met. When two or three phases meet the detection criteria, the differential current criterion and the sampled differential current criterion are not met, and the weak feeder does not start.

[0087] In another embodiment, the weak feed-side differential current voltage-assisted startup method further includes:

[0088] Detect whether the sudden change in current or the zero-sequence current is activated on the opposite side of the line;

[0089] If there is a sudden change in current or zero-sequence current on the opposite side of the line, it is determined that the preset weak feeder side start-up condition is met.

[0090] Specifically, a counter-start judgment element is used to determine whether the current surge or zero-sequence current on the opposite side of the circuit is started, and the criterion is the start of the current surge or zero-sequence current on the opposite side.

[0091] Optionally, the contralateral current surge or zero-sequence current initiation is transmitted via fiber optic channel.

[0092] As an example and not a limitation, the above-mentioned contralateral startup judgment element uses a SOC processor, and the judgment criteria are edited using the corresponding SDK compilation tools.

[0093] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution, nor does it limit the order of judgment of each criterion. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0094] Corresponding to the weak feed-side differential current voltage-assisted start-up method in the above embodiment, Figure 4 A structural block diagram of the weak feed-side differential voltage-assisted start-up device provided in an embodiment of this application is shown. For ease of explanation, only the parts related to the embodiment of this application are shown.

[0095] Reference Figure 4 The device includes:

[0096] The acquisition module is used to acquire the phase currents of each phase at the beginning of the line and the phase currents of each phase at the end of the line, the secondary currents of the line and the opposite side, the composite voltage of the line, and to calculate the differential current amplitude and sampled differential current of each phase current on the current side and the phase current on the opposite side based on the acquired data.

[0097] The judgment module is used to determine whether the differential current amplitude and the sampled differential current meet the differential current criterion, whether the composite voltage meets the voltage criterion, whether the line meets the opposite side start criterion, and to send the judgment result of starting the weak feeder protection.

[0098] The action module receives the judgment result and activates the weak feeder protection based on the judgment result.

[0099] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0100] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0101] This application also provides a terminal device, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor executes the computer program to implement the steps in any of the above method embodiments.

[0102] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps described in the various method embodiments above.

[0103] This application provides a computer program product that, when run on a mobile terminal, enables the mobile terminal to implement the steps described in the above-described method embodiments.

[0104] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of this application can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a photographing device / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals.

[0105] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0106] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] In the embodiments provided in this application, it should be understood that the disclosed apparatus / network devices and methods can be implemented in other ways. For example, the apparatus / network device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0108] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0109] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A weak feed-side differential current voltage-assisted start-up method, characterized in that, include: Obtain the current amplitude parameters on this side of the line and the current amplitude parameters on the opposite side of the line; The current amplitude parameters include the fundamental amplitude, the second harmonic amplitude, and the third harmonic amplitude; The differential current amplitude between the two sides of the line is calculated based on the current amplitude parameters on the local side and the current amplitude parameters on the opposite side of the line. This includes: calculating the fundamental differential current amplitude of the line based on the fundamental amplitude of the line on the local side and the fundamental amplitude of the line on the opposite side; calculating the second harmonic differential current amplitude of the line based on the second harmonic amplitude of the line on the local side and the second harmonic amplitude of the line on the opposite side; and calculating the third harmonic amplitude of the line on the local side and the third harmonic amplitude of the line on the opposite side. Calculate the third harmonic differential current amplitude of the line; determine whether the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter. If so, the fundamental differential current amplitude is used as the differential current amplitude between the line's local side and the opposite side; if the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is not less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter, the line does not meet the preset weak feeder side start-up conditions, and the weak feeder side start-up operation is not performed. Obtain the composite voltage of the line; based on the differential current amplitude and the composite voltage, determine whether the line meets the preset weak feeder side start-up conditions; if it does, perform the weak feeder side start-up operation. The preset weak feed-side start-up conditions include: The differential current amplitude is greater than the preset differential operating current setting; and The negative sequence voltage in the composite voltage is greater than one voltage unit volt, or the zero sequence voltage in the composite voltage is greater than three voltage units volt.

2. The weak feed-side differential current voltage-assisted start-up method as described in claim 1, characterized in that, The preset weak feed-side start-up conditions also include: The sampled differential current is greater than the preset differential operating current setting.

3. The weak feed-side differential current voltage-assisted start-up method as described in claim 2, characterized in that, The weak feed-side differential current voltage-assisted startup method further includes: The secondary current on the local side of the line and the secondary current on the opposite side of the line are obtained; the secondary current on the local side of the line and the secondary current on the opposite side of the line are sampled at the same time to obtain a first current sample value and a second current sample value. The sampled differential current is calculated based on the first current sample value and the second current sample value. The sampled differential current is compared with the preset differential operating current setting. If the sampled differential current is greater than the preset differential operating current setting, it is determined that the line meets the preset weak feeder side start-up condition.

4. The weak feed-side differential current voltage-assisted start-up method as described in claim 3, characterized in that, The line is a three-phase line, and each phase of the three-phase line has a corresponding differential current amplitude and a sampled differential current. If only one phase of the three-phase line has a corresponding differential current amplitude and a sampled differential current that are both greater than the preset differential operating current setting, then it is determined that the preset weak feeder start-up condition is met.

5. The weak feed-side differential current voltage-assisted start-up method as described in claim 1, characterized in that, The weak feed-side differential current voltage-assisted startup method includes: Detect whether the sudden change in current or the zero-sequence current is activated on the opposite side of the line; If a sudden change in current or zero-sequence current occurs on the opposite side of the line, it is determined that the preset weak feeder start-up condition is met.

6. A weak feed-side differential current voltage-assisted starting device, characterized in that, include: The acquisition module is used to acquire the phase currents of each phase at the beginning of the line and the phase currents of each phase at the end of the line, the secondary currents of the line and the opposite side, the composite voltage of the line, and to calculate the differential current amplitude and sampled differential current of each phase current on the current side and the phase current on the opposite side based on the acquired data. The calculation of the differential current amplitude includes: calculating the fundamental differential current amplitude of the line based on the fundamental amplitude of the line itself and the fundamental amplitude of the line opposite; calculating the second harmonic differential current amplitude of the line based on the second harmonic amplitude of the line itself and the second harmonic amplitude of the line opposite; and calculating the third harmonic differential current amplitude of the line based on the third harmonic amplitude of the line itself and the third harmonic amplitude of the line opposite; determining whether the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is less than the product of the fundamental differential current amplitude and a preset differential current harmonic parameter; if so, the fundamental differential current amplitude is used as the differential current amplitude between the line itself and the line opposite; if the sum of the second harmonic differential current amplitude and the third harmonic differential current amplitude is not less than the product of the fundamental differential current amplitude and the preset differential current harmonic parameter, the line does not meet the preset weak feeder side start-up conditions, and the weak feeder side start-up operation is not performed. The judgment module is used to determine whether the differential current amplitude and the sampled differential current meet the differential current criterion, whether the composite voltage meets the voltage criterion, and whether the line meets the opposite side start-up criterion, and to send the judgment result of starting the weak feeder side protection; the differential current criterion and the voltage criterion include: the differential current amplitude is greater than the preset differential operating current setting; and the negative sequence voltage in the composite voltage is greater than one voltage unit volt or the zero sequence voltage in the composite voltage is greater than three voltage units volt; The action module receives the judgment result and activates the weak feed-side protection based on the judgment result.

7. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 5.

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