Zero-sequence inverse time limit protection method and device based on definite inverse time limit composite characteristic

Abstract

The invention discloses a zero-sequence inverse time limit protection method and device based on definite inverse time limit composite characteristics. The method comprises the following steps: determining time extreme values of transformer protection and line protection according to a transformer inverse-time zero-sequence current protection action time equation and a line inverse-time zero-sequence current protection action time equation; judging whether the definite inverse time limit characteristic switching current under the time extreme value meets a preset limiting condition or not, and determining a final definite inverse time limit characteristic switching current according to a judgment result; according to the final inverse time characteristic switching current, the inverse time protection time constant value of the transformer is updated, and the inverse time protection time constant value of the transformer is determined and updated; and according to the time extreme value, the final definite and inverse time limit characteristic switching current and the updated transformer inverse time limit protection time constant value, constructing a transformer definite and inverse time limit composite characteristic zero-sequence current protection action time equation and a line definite and inverse time limit composite characteristic zero-sequence current protection action time equation to carry out zero-sequence inverse time limit protection.

Description

Technical Field

[0001] The present invention relates to the technical field of large power grid backup protection, and more specifically, to a zero-sequence inverse time protection method and device based on fixed-inverse time composite characteristics. Background Art

[0002] Zero-sequence current protection consists of three-stage (or four-stage) zero-sequence current protection and inverse time zero-sequence current. As a supplementary protection for grounding distance when a grounding fault occurs in the line, when the line is grounded through high resistance, the distance protection may not work. At this time, it is necessary to rely on the last stage of zero-sequence current protection to cut off the fault. Therefore, zero-sequence current protection is an important part of maintaining the stability of large power grid operation. With the rapid development of new power systems, the interconnection of AC and DC power grids in my country has become more obvious, and the complexity and globalization of faults have become more prominent. The current large-scale power grid zero-sequence current protection and the backup protection system with it as the core are difficult to effectively cope with the increasingly complex grid structure and operation mode, and are also difficult to meet the increasingly high reliability requirements of backup protection for the safety and stability of large-scale power grids. Specifically, there are the following problems: First, the existing zero-sequence current protection is mainly based on time limit, and it was four-stage in the early days, but in actual projects, it is mostly simplified to two or one stage. Affected by the rapid expansion of the grid structure and the gradual increase in the requirements for coordination across voltage levels (transformers), the coordination between zero-sequence current protections has become increasingly difficult, and there are a large number of objective non-cooperation problems and potential safety risks. Moreover, after the grid structure changes, the set value needs to be modified on a large scale, and the setting calculation work is time-consuming and laborious, but the effect is not good; second, some lines that use zero-sequence inverse time limit protection have risks such as transformer and line non-cooperation and protection over-level tripping. Therefore, while applying zero-sequence inverse time limit protection to improve the problems of high difficulty in protection coordination and large setting workload, it is also necessary to improve its traditional characteristics to solve the mismatch risk in some scenarios. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a zero-sequence inverse time protection method and device based on fixed-inverse time composite characteristics.

[0004] According to one aspect of the present invention, a zero-sequence inverse time protection method based on fixed inverse time composite characteristics is provided, comprising:

[0005] Determine the time extremes of transformer protection and line protection according to the transformer inverse time zero sequence current protection action time equation and the line inverse time zero sequence current protection action time equation;

[0006] Determine whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting conditions, and determine the final fixed inverse time characteristic switching current according to the determination result;

[0007] According to the final inverse time characteristic switching current, the transformer inverse time protection time setting value is updated, and the transformer inverse time protection time setting value is determined and updated;

[0008] According to the time extreme value, the final fixed inverse time characteristic switching current and the update of the transformer inverse time protection time setting value, the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation are constructed;

[0009] Zero-sequence inverse time protection is performed according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

[0010] Optionally, the transformer inverse time zero-sequence current protection action time equation t z,T (I) and the line inverse time zero sequence current protection action time equation t z,L The expression of (I) is:

[0011]

[0012] Where, T 0,T (I) and T 0,L (I) are respectively the inverse time characteristic equation of transformer protection and the inverse time characteristic equation of line protection; I p,T and I p,L are the current settings of transformer inverse time protection and line inverse time protection, T p,T and T p,L They are the time settings of transformer inverse time protection and line inverse time protection respectively; T h,T and T h,L are the coordination time of transformer protection and line protection respectively; T x,T and T x,L They are the minimum time for transformer protection and line protection respectively.

[0013] Optionally, the time extreme value t eq The calculation expression is:

[0014] t eq =t z,L (I Z ) = t z,T (2I Z )

[0015] In the formula, I Z Switching current with inverse time characteristic.

[0016] Optionally, determining the final inverse time characteristic switching current according to the judgment result includes:

[0017] When the judgment result is that the fixed inverse time characteristic switching current under the time extreme value meets the limiting condition, the current fixed inverse time characteristic switching current is used as the final fixed inverse time characteristic switching current;

[0018] When the judgment result is that the fixed inverse time characteristic switching current under the time extreme value does not meet the limiting condition, the fixed inverse time characteristic switching current is limited according to the limiting condition to determine the final fixed inverse time characteristic switching current.

[0019] Optionally, the qualification condition is:

[0020]

[0021] In the formula, K is a constant coefficient.

[0022] Optionally, the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation t' z,T (I) and the line fixed inverse time composite characteristic zero sequence current protection action time equation t' z,L The expression of (I) is:

[0023]

[0024] Wherein, Δt represents the time difference between transformer protection and line protection in the definite time characteristic stage.

[0025] According to another aspect of the present invention, there is provided a zero-sequence inverse time protection device based on a fixed inverse time composite characteristic, comprising:

[0026] The first determination module is used to determine the time extremes of transformer protection and line protection according to the transformer inverse time zero-sequence current protection action time equation and the line inverse time zero-sequence current protection action time equation;

[0027] A judgment module is used to judge whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting conditions, and determine the final fixed inverse time characteristic switching current according to the judgment result;

[0028] The second determination module is used to update the transformer inverse time protection time setting value according to the final inverse time characteristic switching current, and determine to update the transformer inverse time protection time setting value;

[0029] A construction module is used to switch the current and update the transformer inverse time protection time setting value according to the time extreme value and the final fixed inverse time characteristic, and to construct the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation;

[0030] The protection module is used to perform zero-sequence inverse time protection according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

[0031] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method described in any one of the above aspects of the present invention.

[0032] According to another aspect of the present invention, an electronic device is provided, comprising: a processor; a memory for storing instructions executable by the processor; 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 the above aspects of the present invention.

[0033] Therefore, the present invention determines the fixed-time and inverse-time switching current value based on the "twice current isochrones" of the line and the transformer. Below this current value, the line has a fixed-time characteristic, and above this current value, it has an inverse-time characteristic. When the transformer protection current does not exceed twice the line protection current, the transformer action time is always later than the line. Therefore, by appropriately sacrificing the selectivity between the various levels of protection of the high-resistance fault line, the serious accident of transformer over-tripping is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0035] Figure 1 It is a flow chart of a zero-sequence inverse time protection method based on fixed inverse time composite characteristics provided by an exemplary embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the coordination between a transformer and a line inverse time protection provided by an exemplary embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of a fixed-inverse time composite characteristic curve provided by an exemplary embodiment of the present invention;

[0038] Figure 4 It is a fixed-inverse time composite characteristic protection logic diagram provided by an exemplary embodiment of the present invention;

[0039] Figure 5 It is an equivalent impedance distribution diagram of a certain actual engineering system provided by an exemplary embodiment of the present invention;

[0040] Figure 6 It is a zero-sequence inverse time characteristic curve of a transformer and a line in a certain actual project provided by an exemplary embodiment of the present invention;

[0041] Figure 7 It is a structural schematic diagram of a zero-sequence inverse time protection device based on fixed-inverse time composite characteristics provided by an exemplary embodiment of the present invention;

[0042] Figure 8 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0043] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described here.

[0044] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0045] Those skilled in the art can understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0046] It should also be understood that, in the embodiments of the present invention, “plurality” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0047] 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 limited or otherwise indicated in the context.

[0048] In addition, the term "and / or" in the present invention is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0049] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced to each other, and for the sake of brevity, they will not be described one by one.

[0050] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0051] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0052] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0053] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0054] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, servers, etc., which can operate with many other general or special computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, servers, etc. 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 personal computers, small computer systems, large computer systems, and distributed cloud computing technology environments including any of the above systems, etc.

[0055] Electronic devices such as terminal devices, computer systems, servers, etc. can be described in the general context of computer system executable instructions (such as program modules) executed by computer systems. Generally, 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 a distributed cloud computing environment, where tasks are performed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media including storage devices.

[0056] Exemplary Methods

[0057] Figure 1 1 is a flow chart of a zero-sequence inverse time protection method based on a fixed inverse time composite characteristic provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as Figure 1 As shown, the zero-sequence inverse time protection method 100 based on the fixed inverse time composite characteristic includes the following steps:

[0058] Step 101, determining the time extremes of transformer protection and line protection according to the transformer inverse time zero sequence current protection action time equation and the line inverse time zero sequence current protection action time equation;

[0059] Step 102, judging whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting condition, and determining the final fixed inverse time characteristic switching current according to the judgment result;

[0060] Step 103, updating the transformer inverse time protection time setting value according to the final inverse time characteristic switching current, and determining to update the transformer inverse time protection time setting value;

[0061] Step 104, constructing a transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and a line fixed inverse time composite characteristic zero-sequence current protection action time equation according to the time extreme value, the final fixed inverse time characteristic switching current and the updated transformer inverse time protection time setting value;

[0062] Step 105, performing zero-sequence inverse time protection according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

[0063] Specifically, in view of the problems existing in the prior art, the present invention aims to support the backup protection of ground faults in large power grids, and proposes a zero-sequence inverse time protection method with fixed inverse time composite characteristics to avoid the above risks without affecting the original coordination effect. The specific implementation is as follows:

[0064] like Figure 2 As shown in the figure, K1 and K2 are the protections for the transformer and line respectively. When a fault occurs in the line NP, K2 must act before K1. When there is only one line connected between K1 and the fault point, the current flowing through K2 must be greater than or equal to the current of K1, so the action time of K1 must not be earlier than that of K2, thereby achieving coordination between the transformer and line protection. However, when there are two lines connected between K1 and the fault point, the current flowing through K1 may exceed K2, causing K1 to act earlier than K2, resulting in the transformer protection tripping. To address this problem, a zero-sequence inverse time protection method with a comprehensive fixed-inverse time composite characteristic is proposed to avoid the K1 overstepping problem. The specific steps are as follows:

[0065] Step 1): Transformer inverse time zero sequence current protection action time equation t z,T (I) and the line inverse time zero sequence current protection action time equation t z,L (I) are all reflected as a function of the protection action time t to the current I, as shown in formula (1):

[0066]

[0067] Where, T 0,T (I) and T 0,L(I) are the inverse time characteristic equations of transformer protection and line protection, which contain two settable values, namely, time constant and current constant. Let the current constants of the inverse time characteristic equations of transformer inverse time protection and line inverse time protection be denoted as I p,T and I p,L , the time constants are recorded as T p,T and T p,L On this basis, t z,T (I), t z,L (I) also includes coordination time setting and minimum time setting, where the coordination time for transformer protection and line protection is denoted by T h,T and T h,L , and their minimum time is denoted as T x,T and T x,L The above four parameters of current setting value, time setting value, coordination time setting value and minimum time setting value are preset values, which together determine the inverse time characteristics of the protection.

[0068] Step 2): Figure 3 As shown, under the most severe conditions, the maximum zero-sequence current flowing through the transformer does not exceed twice the maximum zero-sequence current value of the zero-sequence protection on both sides of the line. The transformer and line inverse time action time equations in equation (1) are combined to calculate the time t that satisfies the following equation: eq and current I Z :

[0069] t eq =t z,L (I Z ) = t z,T (2I Z ) (2)

[0070] In the formula, I Z Indicates a specific current value, called the fixed inverse time characteristic switching value; the line protection inverse time action time equation t z,L (I) At current I Z The corresponding time and the inverse time action time equation of transformer protection are in the current 2I Z The corresponding time is exactly the same, and this time is recorded as t eq , called the "double current isochrone" of the transformer inverse time protection and line inverse time protection characteristic curve.

[0071] Step 3): Adopting fixed-time inverse composite characteristics Since the fixed-time characteristic is adopted in the low current region, the selectivity between line protections when a high-resistance fault occurs will be sacrificed to a certain extent. In order to reduce the above influence and optimize the coordination performance between line protections while ensuring the coordination between the transformer and the line, the fixed-time inverse composite characteristics switching current I is limited according to formula (3). Z The maximum value of. In formula (3), if IZ After calculation by formula (2), the limit value K·I is not reached. p,L , then no modification is made and go to step 4); if I Z After calculation by formula (2), the limit value K·I is reached p,L , then the modified I Z Substitute into equation (1) and equation (2), and update T while keeping other parameters unchanged. p,T Take a value so that equations (1) and (2) still hold, and then go to step 4).

[0072]

[0073] In the formula, K is a constant coefficient, which can usually be 1. <K≤1.5。

[0074] Step 4): Based on the above steps, the transformer inverse time zero-sequence current protection action time equation t z,T (I) Line inverse time zero sequence current protection action time equation t z,L (I) Inverse time characteristics of line protection on the “twice current isochrone line” t eq , set the inverse time characteristic switching setting I Z , the fixed inverse time composite characteristic of zero sequence current protection is described as follows, and its action logic diagram can be obtained by Figure 4 express.

[0075]

[0076] In the formula, t' z,T (I) and t' z,L (I) represents the action time of transformer and line zero-sequence current protection adopting fixed-time and inverse-time composite characteristics, and Δt represents the time difference between transformer and line protection in the fixed-time characteristic stage.

[0077] The effects of the present invention are described as follows: it can solve the problem that when there is a certain zero-sequence impedance distribution mode, the zero-sequence current flowing through the main transformer after a line fault is greater than the zero-sequence current flowing through both sides of the fault line, and the use of zero-sequence inverse time protection will increase the risk of over-tripping. Figure 5 The equivalent network shown, E M 、E N and E K is the equivalent potential of the three-side system, busbars A, C and D are the three-side system busbars, E K The side system is connected to E through a transformer connected to bus D. M and E N Connected systems.

[0078] E M and E NThe equivalent zero-sequence impedance of the systems on both sides depends on the neutral point grounding method of the systems on both sides and the strength of the systems on both sides. When a fault occurs at point F1, the zero-sequence current flows from the fault point to both sides, passing through protections 3 and 4 located at busbars B and C. The magnitude of the current at the fault point is determined by the zero-sequence equivalent impedance, and the distribution of the current from the fault point to both sides depends on the magnitude relationship of the zero-sequence impedance on both sides. In extreme cases, when E M and E N When the neutral point of the systems on both sides is ungrounded, or the systems on both sides are weak and the equivalent zero-sequence impedance is large, the currents on both sides of the fault point are almost all collected on the transformer side connected to busbar D, that is, the current flowing through protection 5 is approximately the sum of protections 3 and 4. When the currents flowing through protections 3 and 4 are equal, the ratio of the current flowing through protection 5 to the larger value of the two is the maximum, close to twice. At this time, if the transformer and the line use the same inverse time characteristic curve or do not have a characteristic curve that can distinguish the above current differences, the transformer protection 5 will trip beyond the level, causing the accident to expand.

[0079] Specifically, Figure 6 The paper shows the selection of inverse time characteristic parameters when the transformer and 500kV line adopt zero-sequence inverse time protection at the same time in an actual project on site. p , T h and T x The three parameters are the same for transformers and lines, which are 300A, 0.5s and 2.5s respectively. In addition, the transformer Tp is set to 0.6s or 0.8s and the line Tp is set to 0.4s to achieve the coordination of the transformer and line inverse time protection. According to the above, under extreme conditions, the ratio of the zero-sequence current of the converter transformer to the larger value of the zero-sequence current at both ends of the fault line does not exceed 2 times, so over-tripping is most likely to occur at low fault currents, such as high-resistance faults. Figure 6 Under the parameters, take the larger current of 440A flowing through protection 3 and 4 as an example, the fault action time is 10s. In extreme cases, the current flowing through transformer protection 5 may reach twice the above value, that is, 880A. Figure 6 Under the two transformer inverse time characteristic curves, the action time of transformer protection 5 at 880A is approximately 6.3s (Tp=0.6s) and 8.0s (Tp=0.8s), that is, transformer protection 5 will act faster than line protection 3 and 4, resulting in overstepping.

[0080] Therefore, the fixed-inverse time composite characteristic proposed in the present invention determines the fixed-inverse time switching current value based on the "twice current isochrones" of the line and the transformer. Below this current value, the line has a fixed-time characteristic, and above this current value, it has an inverse time characteristic. When the transformer protection current does not exceed twice the line protection current, the transformer action time is always later than the line, thereby avoiding serious accidents such as transformer over-tripping by appropriately sacrificing the selectivity between the various levels of protection of the high-resistance fault line.

[0081] Exemplary Devices

[0082] Figure 7 FIG. 1 is a schematic diagram of the structure of a zero-sequence inverse time protection device based on a fixed inverse time composite characteristic provided by an exemplary embodiment of the present invention. Figure 7 As shown, the apparatus 700 includes:

[0083] The first determination module 710 is used to determine the time extremes of transformer protection and line protection according to the transformer inverse time zero-sequence current protection action time equation and the line inverse time zero-sequence current protection action time equation;

[0084] The judgment module 720 is used to judge whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting conditions, and determine the final fixed inverse time characteristic switching current according to the judgment result;

[0085] The second determination module 730 is used to update the transformer inverse time protection time setting value according to the final inverse time characteristic switching current, and determine to update the transformer inverse time protection time setting value;

[0086] A construction module 740 is used to switch the current and update the transformer inverse time protection time setting value according to the time extreme value and the final fixed inverse time characteristic, and to construct the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation;

[0087] The protection module 750 is used to perform zero-sequence inverse time protection according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

[0088] Optionally, the transformer inverse time zero-sequence current protection action time equation t z,T (I) and the line inverse time zero sequence current protection action time equation t z,L The expression of (I) is:

[0089]

[0090] Where, T 0,T (I) and T 0,L (I) are respectively the inverse time characteristic equation of transformer protection and the inverse time characteristic equation of line protection; I p,T and I p,L are the current settings of transformer inverse time protection and line inverse time protection, T p,T and T p,L They are the time settings of transformer inverse time protection and line inverse time protection respectively; T h,T and T h,Lare the coordination time of transformer protection and line protection respectively; T x,T and T x,L They are the minimum time for transformer protection and line protection respectively.

[0091] Optionally, the time extreme value t eq The calculation expression is:

[0092] t eq =t z,L (I Z ) = t z,T (2I Z )

[0093] In the formula, I Z Switching current with inverse time characteristic.

[0094] Optionally, the determination module 720 includes:

[0095] The first judgment submodule is used to use the current fixed inverse time limit characteristic switching current as the final fixed inverse time limit characteristic switching current when the judgment result is that the fixed inverse time limit characteristic switching current under the time extreme value meets the limited condition;

[0096] The second judgment submodule is used to limit the fixed inverse time characteristic switching current according to the limiting conditions when the judgment result is that the fixed inverse time characteristic switching current under the time extreme value does not meet the limiting conditions, and determine the final fixed inverse time characteristic switching current.

[0097] Optionally, the qualification condition is:

[0098]

[0099] In the formula, K is a constant coefficient.

[0100] Optionally, the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation t' z,T (I) and the line fixed inverse time composite characteristic zero sequence current protection action time equation t' z,L The expression of (I) is:

[0101]

[0102] Wherein, Δt represents the time difference between transformer protection and line protection in the definite time characteristic stage.

[0103] Exemplary Electronic Devices

[0104] Figure 8 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. Figure 8 As shown, the electronic device 80 includes one or more processors 81 and a memory 82 .

[0105] The processor 81 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0106] 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 (cache), etc. 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 run the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above and / or other desired functions. In one example, the electronic device may also include: an input device 83 and an output device 84, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0107] In addition, the input device 83 may also include, for example, a keyboard, a mouse, etc.

[0108] The output device 84 can output various information to the outside, and can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

[0109] Of course, to simplify, Figure 8 Only some of the components related to the present invention in the electronic device are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device may further include any other appropriate components according to specific application conditions.

[0110] Exemplary computer program products and computer-readable storage media

[0111] In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above-mentioned "Exemplary Method" section of this specification.

[0112] The computer program product may be written in any combination of one or more programming languages ​​to write program code for performing the operations of the embodiments of the present invention, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0113] In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above “Exemplary Method” section of this specification.

[0114] The computer readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, a system, system or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0115] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0116] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0117] The block diagrams of the devices, systems, equipment, and systems involved in the present invention are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The word "such as" used here refers to the phrase "such as but not limited to", and can be used interchangeably with it.

[0118] The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware or any combination of software, hardware, firmware. The above order of steps for the method is only for illustration, and the steps of the method of the present invention are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.

[0119] It should also be noted that in the system, device and method of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in the field to make or use the present invention. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but in accordance with the widest range consistent with the principles and novel features disclosed here.

[0120] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A zero-sequence inverse time protection method based on fixed inverse time composite characteristics, characterized in that: include: Determine the time extremes of transformer protection and line protection according to the transformer inverse time zero sequence current protection action time equation and the line inverse time zero sequence current protection action time equation; Determine whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting condition, and determine the final fixed inverse time characteristic switching current according to the determination result; According to the final inverse time characteristic switching current, the transformer inverse time protection time constant is updated, and the transformer inverse time protection time constant is updated; According to the time extreme value, the final fixed inverse time characteristic switching current and the updated transformer inverse time protection time constant, a transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and a line fixed inverse time composite characteristic zero-sequence current protection action time equation are constructed; Zero-sequence inverse time protection is performed according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

2. The method according to claim 1, characterized in that The transformer inverse time zero sequence current protection action time equation t z,T (I) and the line inverse time zero sequence current protection action time equation t z,L The expression of (I) is: Where, T 0,T (I) and T 0,L (I) are respectively the inverse time characteristic equation of transformer protection and the inverse time characteristic equation of line protection; I p,T and I p,L are the current settings of transformer inverse time protection and line inverse time protection, T p,T and T p,L They are respectively the time settings of transformer inverse time protection and line inverse time protection; T h,T and T h,L are the coordination time of transformer protection and line protection respectively; T x,T and T x,L They are the minimum time for transformer protection and line protection respectively.

3. The method according to claim 2, characterized in that The time extreme value t eq The calculation expression is: t eq =t z,L (AND Z )=t z,T (2I Z ) In the formula, I Z Switching current with inverse time characteristic.

4. The method according to claim 3, characterized in that The final inverse time characteristic switching current is determined according to the judgment result, including: When the judgment result is that the fixed inverse time characteristic switching current under the time extreme value satisfies the limiting condition, the current fixed inverse time characteristic switching current is used as the final fixed inverse time characteristic switching current; When the judgment result is that the fixed inverse time characteristic switching current at the time extreme value does not meet the limiting condition, the fixed inverse time characteristic switching current is limited according to the limiting condition to determine the final fixed inverse time characteristic switching current.

5. The method according to claim 4, characterized in that The limiting conditions are: In the formula, K is a constant coefficient.

6. The method according to claim 3, characterized in that The transformer fixed inverse time composite characteristic zero-sequence current protection action time equation t' z,T (I) and the line fixed inverse time composite characteristic zero sequence current protection action time equation t' z,L The expression of (I) is: Wherein, Δt represents the time difference between transformer protection and line protection in the definite time characteristic stage.

7. A zero-sequence inverse time protection device based on fixed-inverse time composite characteristics, characterized in that: include: The first determination module is used to determine the time extremes of transformer protection and line protection according to the transformer inverse time zero-sequence current protection action time equation and the line inverse time zero-sequence current protection action time equation; A judgment module, used to judge whether the fixed inverse time characteristic switching current under the time extreme value meets the preset limiting conditions, and determine the final fixed inverse time characteristic switching current according to the judgment result; A second determination module is used to update the transformer inverse time protection time setting value according to the final inverse time characteristic switching current, and determine to update the transformer inverse time protection time setting value; A construction module is used to construct a transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and a line fixed inverse time composite characteristic zero-sequence current protection action time equation according to the time extreme value, the final fixed inverse time characteristic switching current and the updated transformer inverse time protection time fixed value; The protection module is used to perform zero-sequence inverse time protection according to the transformer fixed inverse time composite characteristic zero-sequence current protection action time equation and the line fixed inverse time composite characteristic zero-sequence current protection action time equation.

8. The device according to claim 7, characterized in that The transformer inverse time zero sequence current protection action time equation t z,T (I) and the line inverse time zero sequence current protection action time equation t z,L The expression of (I) is: Where, T 0,T (I) and T 0,L (I) are respectively the inverse time characteristic equation of transformer protection and the inverse time characteristic equation of line protection; I p,T and I p,L are the current settings of transformer inverse time protection and line inverse time protection, T p,T and T p,L They are respectively the time settings of transformer inverse time protection and line inverse time protection; T h,T and T h,L are the coordination time of transformer protection and line protection respectively; T x,T and T x,L They are the minimum time for transformer protection and line protection respectively.

9. The device according to claim 8, characterized in that The time extreme value t eq The calculation expression is: t eq =t z,L (AND Z )=t z,T (2I Z ) In the formula, I Z Switching current with inverse time characteristic.

10. The device according to claim 9, characterized in that The judgment module includes: A first judgment submodule is used for, when the judgment result is that the fixed inverse time limit characteristic switching current under the time extreme value satisfies the limiting condition, taking the current fixed inverse time limit characteristic switching current as the final fixed inverse time limit characteristic switching current; The second judgment submodule is used to limit the fixed inverse time characteristic switching current according to the limiting condition when the judgment result is that the fixed inverse time characteristic switching current under the time extreme value does not meet the limiting condition, so as to determine the final fixed inverse time characteristic switching current.

11. The device according to claim 10, characterized in that The limiting conditions are: In the formula, K is a constant coefficient.

12. The device according to claim 9, characterized in that The transformer fixed inverse time composite characteristic zero-sequence current protection action time equation t' z,T (I) and the line fixed inverse time composite characteristic zero sequence current protection action time equation t' z,L The expression of (I) is: Wherein, Δt represents the time difference between transformer protection and line protection in the definite time characteristic stage.

13. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 6.

14. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is used to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1 to 6.

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