Selective action identification method applied to micro-explosion type current limiter

Abstract

The invention discloses a selective action identification method applied to a micro-explosion type current limiter, and relates to the field of electric power system electrical detection and high-voltage electrical equipment control, and the method comprises the steps: determining close association nodes of the micro-explosion type current limiter according to a power distribution network topology structure; determining the connection polarity of each branch current secondary signal of the close association node based on the close association node; sampling the current of each branch, comparing and judging whether the sampling value of the current of each branch meets the current direction condition based on the polarity of the secondary signal of the current of each branch of the close association node, and determining the current limiter on the branch meeting the current direction condition as a target current limiter; calculating the current characteristic quantity of each target current limiter; judging whether the current characteristic quantity meets a fault threshold condition or not, and determining the current limiter meeting the fault threshold condition as an operable current limiter; a driving signal is sent to the operable current limiter; the selective action of the micro-explosion type current limiter is realized, and the influence of an impact load on a judgment result is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of electric system electrical detection and high-voltage electrical equipment control, and relates to a selective action identification method applied to a micro-explosion type current limiter. Background Art

[0002] During power system operation, excessive currents generated by short-circuit faults can seriously threaten the system's thermal and dynamic stability. Therefore, fault current limiters (FCLs) have become critical equipment for ensuring safe and stable power system operation. Pyrotechnic fault current limiters (PFCLs), leveraging micro-directional blasting technology, can rapidly disconnect the main conductive circuit, diverting the fault current to a parallel current-limiting fuse branch. Ultimately, this current-limiting device effectively addresses the thermal and dynamic stability issues facing power systems. Compared to other current-limiting technologies, this current limiter boasts significant advantages in terms of maturity, reliability, and cost-effectiveness. It has been widely used in power distribution systems across numerous industries, including power, chemical, metallurgy, papermaking, and sugar production.

[0003] However, in actual engineering application scenarios, such as the busbar coupling position with multiple busbar sections in parallel, the connection position of the old and new distribution systems, the interconnection of multiple power sources, and the access to the grid of small units, there is often a need for selective action. Since the breaking components of the micro-explosion type current limiter involve explosive cutting and fuse technology, they are disposable in nature and need to be replaced once they are activated, which will undoubtedly increase maintenance costs. However, when the existing micro-explosion type current limiter is selectively identified, it only controls a single current limiter and cannot perform regional selective action identification. The maintenance cost is high and it is difficult to meet the needs of complex application scenarios, which has become a technical bottleneck that limits its further optimization of application. Therefore, finding a method to solve the selective action of the micro-explosion type current limiter has important practical significance and application value. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems in the prior art that the selective action identification of micro-burst type current limiters only considers the control of a single current limiter, has high maintenance costs, cannot be controlled through regional selective action identification, and is difficult to accurately meet the needs of complex application scenarios under network topology. A method for identifying the selective action of micro-burst type current limiters is provided.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for identifying the selective action of a micro-explosion type current limiter, comprising the following steps: Determine the connection polarity of the secondary signal of each branch current according to the closely related nodes, sample the current of each branch of the closely related nodes, determine whether the sampled value of each branch current meets the current direction condition, and determine the current limiter on the branch that meets the current direction condition as the target current limiter; Calculating current characteristic quantities of each target current limiter; determining whether the current characteristic quantity meets the fault threshold condition, and determining the current limiter that meets the fault threshold condition as the actionable current limiter; Sends a drive signal to the operable current limiter.

[0006] Furthermore, the closely associated node is a node in the power distribution network topology that is directly connected to at least one micro-explosion current limiter.

[0007] Furthermore, the connection polarity of the secondary signals of the branch currents of the closely associated nodes satisfies that: when a short circuit fault occurs in the closely associated node area, the secondary signal sampling values corresponding to the branch currents have the same sign at any non-zero-crossing moment.

[0008] Furthermore, the current direction condition includes a current same direction condition, a current normalization condition or a current reverse direction condition.

[0009] Furthermore, for closely related nodes with three branches, the current direction condition is the current same direction condition or the current two-normalization condition; For closely related nodes with two branches, the current direction condition is the current same direction condition or the current reverse direction condition.

[0010] Furthermore, the current same-direction condition is that when the signs of the current sampling values of each branch are the same at any time, all micro-explosion current limiters directly connected to the closely associated node should be determined as target current limiters; The current two-normalization condition is that the current sampling values of two branches among the three branches have the same sign at any time and are opposite in sign to the sampling value of the current of the third branch, then the micro-explosion current limiter on the third branch is determined to be the target current limiter; The current reversal condition is that the signs of the current sampling values of the two branches at any time are always opposite, and the micro-explosion current limiter directly connected to the closely related node is determined as the target current limiter.

[0011] Furthermore, the current characteristic quantities include instantaneous current value, instantaneous current change rate, small half-wave zero-crossing time span of instantaneous current value or instantaneous change rate, fast prediction of current steady-state peak value, current and current algebraic sum.

[0012] Furthermore, the fault threshold condition is a characteristic parameter in the current characteristic quantity or a logical combination of multiple characteristic parameters in the current characteristic quantity.

[0013] Furthermore, the driving signal is an electrical pulse signal or an optical pulse signal.

[0014] Furthermore, for a current limiter on a common branch of two adjacent closely associated nodes, only when it is simultaneously determined as a target current limiter by the two adjacent closely associated nodes, can the current limiter be finally confirmed as the target current limiter.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for identifying the selective action of a micro-explosion type current limiter. The method determines the closely related nodes of the micro-explosion type current limiter through the topological structure of the power distribution network, clarifies the connection polarity of the secondary signal of the current of each branch, and selects the target current limiter in combination with the current direction condition. That is, a mapping rule between the number of branches of the topological node and the current direction condition is established. According to the dynamic screening rule of the number of node branches, one of the micro-explosion type current limiters under the same closely related node can be selected as the target current limiter for action. With this method, only one control system needs to be arranged at the closely related node, and one control system needs to be selected at the closely related node. The control system can control multiple micro-explosion current limiters of each branch of a closely related node. There is no need to arrange a control system at each micro-explosion current limiter to control the actions of multiple micro-explosion current limiters at the node, which saves implementation costs. At the same time, for multiple micro-explosion current limiters of each branch of each closely related node, the present invention only needs to collect the current of each branch to complete the control of the multiple current limiters. Compared with the existing micro-explosion current limiter control method, in which each current limiter needs to be arranged with a control system and the current and port current of each current limiter need to be measured, the present invention is easy to implement and greatly reduces operation and maintenance costs.

[0016] By adopting the method of the present invention, a control system can identify whether the micro-explosion current limiter of each branch of a closely associated node is the target current limiter, and complete the fault isolation of the closely associated node area. There is no need to install a control system on each micro-explosion current limiter. For a multi-node topology network, the judgment of the target current limiter of each node does not rely on the judgment of other nodes, which is easy to implement. The present invention determines the target current limiter by whether the current conditions of each branch at the closely associated node meet the current direction condition. By comparing the current characteristic quantity of the target current limiter with the fault threshold, the influence of each branch of the closely associated node is taken into account, and the specific area where the fault occurs can be accurately locked, avoiding large-scale power outages caused by fuzzy fault location, and significantly improving the efficiency of fault investigation and repair. Based on the dual judgment mechanism of current direction condition and fault threshold condition, it effectively distinguishes normal operating current fluctuations from real fault current, avoids the current limiter from triggering action under unnecessary circumstances, reduces unnecessary equipment action loss and power outage loss, and improves the stability and reliability of the distribution system operation. By rapidly sampling and evaluating the current in each branch, the system quickly selects the actionable current limiters that meet the conditions and promptly sends actuation signals. This allows for rapid fault isolation, shortens the fault duration, reduces the impact of the fault on the distribution system and electrical equipment, reduces system disturbances, and enhances system stability. This method ensures that the current limiter operates only when necessary, reducing the impact of frequent current limiter activation on the system, extending equipment life, and reducing operation and maintenance costs. It also ensures continuous power supply in non-faulty areas, improving power supply continuity and operational efficiency across the entire distribution network.

[0017] Furthermore, by defining the "current same-direction condition," "current normalization condition," and "current reverse direction condition," differentiated judgment rules are developed for closely related nodes with varying numbers of branches, enabling precise identification of fault current flow characteristics. In scenarios with three branches, applying the current same-direction condition or the current normalization condition accurately determines the faulty branch. In scenarios with two branches, the current same-direction or reverse direction condition allows for rapid localization of the fault location, significantly improving the sophistication and accuracy of fault location. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Flowchart of the selective action identification method applied to a micro-explosion type current limiter of the present invention; Figure 2The embodiment of the present invention is directed to a power distribution network having only a single three-branch closely associated node; Figure 3 The embodiment of the present invention is directed to a power distribution network having three adjacent closely associated nodes and a common current limiter branch; Figure 4 This embodiment of the present invention is directed to a power distribution network having only a single two-branch closely connected node. Here, FCL1 is the first microburst current limiter; FCL2 is the second microburst current limiter; and FCL3 is the third microburst current limiter. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and marked in the drawings herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0023] It should be noted that all the flow limiters mentioned in the embodiments of the present invention are micro-explosion type flow limiters.

[0024] The present invention is described in further detail below with reference to the accompanying drawings: See also Figure 1 The present invention discloses a method for identifying the selective action of a micro-explosion type current limiter, comprising the following steps: Step 1: Determine closely associated nodes for the microburst current limiter based on the distribution network topology. The principle for determining closely associated nodes is that the node is directly connected to at least one microburst current limiter, meaning there is at least one microburst current limiter branch. Nodes with multiple microburst current limiter branches are preferred as closely associated nodes, and the total number of branches at the node should be 2 or 3. Each branch current includes three phases: A, B, and C. For distribution systems with a neutral point grounded via an arc suppression coil or high-resistance grounding, each branch current can be any two of these phases.

[0025] Step 2: Determine the connection polarity of the secondary current signals of each branch of the closely associated node based on the closely associated node; the connection polarity of the secondary current signals of each branch should satisfy the following requirement: when a short circuit fault occurs in the closely associated node area, the secondary signal sampling values corresponding to each branch current have the same sign at any non-zero-crossing moment.

[0026] Step 3: Sample the current of each branch, and determine whether the sampled value of each branch current meets the current direction condition based on the polarity identification of the secondary signal of each branch current of closely related nodes, and determine the current limiter on the branch that meets the current direction condition as the target current limiter.

[0027] The current direction condition is specifically: for a node with three closely related branches, the current direction condition is a current same direction condition or a current two-to-one condition; for a node with two closely related branches, the current direction condition is a current same direction condition or a current reverse direction condition.

[0028] The current same-direction condition is that the signs of the current sampling values of each branch are the same at any time, and all current limiters directly connected to the closely related node should be determined as the target current limiter.

[0029] The current two-normalization condition is that at any time, the signs of the sampling values of the currents of two branches are always the same and opposite to the signs of the sampling values of the current of the third branch. Then the current limiter on the third branch is determined to be the target current limiter.

[0030] The current reversal condition is only applicable to two closely related nodes. If the signs of the two branch current sampling values are always opposite at any time, the current limiter directly connected to the closely related node is determined as the target current limiter.

[0031] In particular, for a current limiter on a common branch of two adjacent closely associated nodes, only when it is simultaneously determined as a target current limiter by the two adjacent closely associated nodes, can the current limiter be finally confirmed as the target current limiter; Step 4: Calculate the current characteristic of each target current limiter. Specifically, the current characteristic may include the instantaneous value of the current , instantaneous value of current change rate , the instantaneous value of current or the instantaneous rate of change of current is small half-wave zero crossing time span , fast prediction value of current steady-state peak , current and current algebraic sum These characteristic quantities can be obtained through the sampling value of the current. Assume that the expression of the phase A current signal of a target current limiter branch is as follows: (1) Where, is the peak value of the fault current, is the peak operating current before the fault, is the angular frequency, is the system voltage phase angle at the moment of short circuit, is the power factor angle of the short-circuit circuit, is the power factor angle during normal operation before short circuit, is a sine function, is the Euler number, is the time constant of the circuit.

[0032] Then the first differential signal of the instantaneous value of the current is for:

[0033] in, is the cosine function, It is the first differential signal of the instantaneous value of current.

[0034] Ignoring the non-periodic components, we get: (2) Then the second-order differential signal of the instantaneous current is The expression is as follows:

[0035] in, It is the second differential signal of the instantaneous value of current.

[0036] Ignoring the non-periodic components, we get: (3) Combining equations (2) and (3), we can obtain: (4) According to the instantaneous value of current Sampling interval The sampling array sequence can be obtained 、 An array sequence of values, as shown below: 、 、 、 、 、 、 、 、 、 … 、 、 、 、 、 、 、 … 、 、 、 、 、 … in, 、 、 、 、 、 、 、 、 、 is the instantaneous value of current by is the 10 sampling values of the sampling interval; 、 、 、 、 、 、 、 is the first differential signal of the instantaneous value of the current Array sequence of ; 、 、 、 、 、 is the second differential signal of the instantaneous current value A sequence of arrays.

[0037] by As an example, we can obviously get the moment (i.e. time) and value: (5) (6) Substituting equations (5) and (6) into equation (4), we can obtain The predicted value of .

[0038] In addition, according to the above Sampling interval The sampling array sequence and the digital processing Array sequence, can be detected and The time span between the first two zero crossings :

[0039] in, is the sampling interval, is the first zero crossing point, is the second zero-crossing point. The specific criteria for the zero-crossing point are: For the instantaneous value of current : First zero crossing: × ≤0 Second zero crossing: × ≤0 in, is the instantaneous value of the current at the first zero crossing point, is the instantaneous value of the current at the sampling moment before the first zero crossing point, is the instantaneous value of the current at the second zero crossing point, is the instantaneous value of the current at the sampling moment before the second zero-crossing point.

[0040] For the instantaneous rate of change of current : First zero crossing: × ≤0 Second zero crossing: × ≤0 in, is the instantaneous rate of change of current at the first zero crossing point, is the instantaneous rate of change of current at the sampling moment before the first zero crossing point, is the instantaneous rate of change of current at the second zero crossing point, is the instantaneous rate of change of current at the sampling moment before the second zero-crossing point.

[0041] Similarly, based on the sampling values of each branch current, it is easy to obtain the current algebraic sum Assuming that the closely related node is a 3-branch closely related node, the first phase current of each branch A is The sampling values are 、 、 ,but .

[0042] Step 5: Determine whether the current characteristic quantity meets the fault threshold condition, and determine the current limiter that meets the fault threshold condition as the actionable current limiter; the fault threshold condition can be the threshold condition of a parameter in the current characteristic quantity, or a logical combination of multiple parameter threshold conditions.

[0043] For example: ≥i set AND ≥[ ] set Another example: ≥i set OR 1ms≤ ≤5ms}AND{ ≥[ ] set OR ≥I set} Among them, i set Indicates the fault threshold of the instantaneous value of the current; [ ] set Indicates the fault threshold of the instantaneous rate of change of current; I set Indicates the fault threshold for rapid prediction of the steady-state peak current. AND indicates the logical operation and OR indicates the logical operation.

[0044] Step 6: Output a drive signal to all operable current limiters. The drive signal can be either an electrical pulse or an optical pulse. Optical pulses offer enhanced immunity to electromagnetic interference and superior isolation between high and low potentials. This signal can serve as the trigger for the current limiter's operation or simply as an auxiliary criterion. When the drive signal serves solely as an auxiliary criterion for current limiter operation, the threshold conditions described in Step 5 primarily serve to mitigate interference and prevent false operation. Because the current direction condition may be met under normal operating conditions, the current threshold condition must be used as a blocking mechanism.

[0045] One embodiment of the present invention provides a method for identifying the selective action of a micro-burst current limiter for a power distribution network having only a single three-branch closely related node. Figure 2 As shown, T1, T2, and T3 are all transformers, each with a node connected to a current limiter. Each node branch is equipped with a current transformer (CT). A short circuit in the node 1 area requires that only the first microburst current limiter FCL1 be activated. A fault in the node 2 area requires that both the first microburst current limiter FCL1 and the second microburst current limiter FCL2 be activated. A fault in the node 3 area requires that only the second microburst current limiter FCL2 be activated. Only in this way can the fault be isolated with minimal disruption to the distribution network and at the lowest cost. Based on the selective action identification method for microburst current limiters described in the present invention, a method for identifying the selective action of the first microburst current limiter FCL1 and the second microburst current limiter FCL2 is constructed (in actual operation, the core ideas contained in this method can be compiled into dedicated software and embedded in a specially designed intelligent identification device to achieve automatic detection and control), so that the microburst current limiters in the distribution network have a selective action function. The specific steps are as follows: S1, select closely associated nodes: Node 2 is a three-branch node, including two current limiter branches, so node 2 should be selected as the only closely associated node.

[0046] S2, determine the connection polarity of the secondary signal of each branch current: connect the three branch currents I CT2 , I CT3 , I CT4 (This current is measured by the current transformer on each branch, that is, CT2 measures I CT2 CT3 measurement I CT3 , CT4 measurement I CT4 ) Connect the three input interfaces IN1, IN2 and IN3 of the intelligent identification device with the correct polarity, that is, ensure that the corresponding secondary signal sampling values when the primary current of each branch flows into node 2 have the same sign at any non-zero-crossing moment.

[0047] S3, determine the current direction condition, and determine the current limiter on the branch that meets the current direction condition as the target current limiter. For three-branch nodes, the "current same direction" condition or the "current two normalization" condition should be adopted. When the sampling values of the three-branch currents at any time (in actual operation, it can be several consecutive sampling points, the same below) are all positive or negative, that is, the "current same direction" condition is met, indicating that the fault is in the node 2 area, the first micro-explosion current limiter FCL1 and the second micro-explosion current limiter FCL2 on the node 2 branch can be determined as the target current limiter. When at any time, I CT3 , I CT4 The value of is always in the same direction as I CT2 Always in reverse, that is, I CT2 The "current two-to-one" condition is met, indicating that the fault is in the node 1 area. CT2 The first microburst current limiter FCL1 on the branch is determined as the target current limiter. CT2 , I CT3 The value of is always in the same direction as I CT4 Always in reverse, that is, I CT4 The "current two-to-one" condition is met, indicating that the fault is in the node 3 area. CT4 The second microburst current limiter FCL2 on the branch line is determined as the target current limiter.

[0048] S4: If there is a target current limiter, it is necessary to determine the current characteristic value I of each target current limiter. F Whether the fault threshold condition I is met F-SET , if I F ≥I F-SET , the corresponding target current limiter can be confirmed as an actionable current limiter.

[0049] S5 outputs a driving signal to the actionable current limiter through the output interface of the intelligent device.

[0050] One embodiment of the present invention provides a method for identifying the selective action of a micro-burst current limiter for a power distribution network having three adjacent closely related nodes and a common current limiter branch. Figure 3 As shown, if a short circuit occurs in the node 1 area, only the first microburst current limiter FCL1 is required to be activated. If a fault occurs in the node 2 area, only the first microburst current limiter FCL1 and the second microburst current limiter FCL2 are required to be activated. If a fault occurs in the node 3 area, only the second microburst current limiter FCL2 and the third microburst current limiter FCL3 are required to be activated. And if a fault occurs in the node 4 area, only the third microburst current limiter FCL3 is required to be activated. Only in this way can the fault be isolated with the lowest disturbance to the distribution network and the lowest cost. According to the steps described in the present invention, a method for identifying the selective activation of the first microburst current limiter FCL1, the second microburst current limiter FCL2, and the third microburst current limiter FCL3 is constructed (in actual operation, the core ideas contained in this method can be compiled into dedicated software and embedded in a specially designed intelligent identification device to achieve automatic detection and control), so that the microburst current limiters in the distribution network have selective activation capabilities. The specific steps are as follows: S1, select closely connected nodes: Node 2 and Node 3 are both three-branch nodes, and each node contains two current limiter branches. Therefore, both Node 2 and Node 3 should be selected as closely connected nodes, and the FCL2 branch should be the common branch of these two nodes.

[0051] S2, determine the connection polarity of the secondary signals of each branch current: closely associate the three branch currents I CT2 , I CT3 , I CT4 Connect the three input interfaces IN1, IN2 and IN3 of the intelligent identification device-1 with the correct polarity, that is, ensure that the corresponding secondary signal sampling values when the primary current of each branch flows into node 2 have the same sign at any non-zero-crossing moment. CT4 , I CT5 , I CT6 Connect the three input interfaces IN1, IN2 and IN3 of the intelligent identification device-2 with correct polarity, that is, ensure that the corresponding secondary signal sampling values when the primary current of each branch flows into the node 3 have the same sign at any non-zero-crossing moment.

[0052] S3: Determine the current direction condition and select the current limiter on the branch that meets the current direction condition as the target current limiter. For a three-branch node, the current direction condition or the current normalization condition should be used.

[0053] For node 2, when the three-branch current I CT2 , I CT3 , I CT4The sampling values of at any time (in actual operation, it can be several consecutive sampling points, the same below) are all positive or negative, that is, the "current same direction" condition is met, indicating that the fault is in the node 2 area, and the first micro-burst current limiter FCL1 and the second micro-burst current limiter FCL2 on the node 2 branch can be determined as the target current limiter. When at any time, I CT3 , I CT4 The value of is always in the same direction as I CT2 Reverse, that is, I CT2 The "current two-to-one" condition is met, indicating that the fault is in the node 1 area. CT2 The first microburst current limiter FCL1 on the branch is determined as the target current limiter. CT2 , I CT3 The value of is always in the same direction as I CT4 Reverse, that is, I CT4 If the "current two-to-one" condition is met, it means the fault is in the node 3 or node 4 area. CT4 The second microburst current limiter FCL2 on the branch line is determined as the target current limiter.

[0054] For node 3, when the three-branch current I CT4 , I CT5 , I CT6 The sampling values at any time have the same sign, that is, they meet the "current same direction" condition, indicating that the fault is in the node 3 area. The first microburst current limiter FCL1 and the second microburst current limiter FCL2 on the node 2 branch can be determined as the target current limiter. CT5 , I CT6 The value of is always in the same direction as I CT4 Reverse, that is, I CT4 If the "current two-to-one" condition is met, it means the fault is in the node 2 or node 1 area. CT4 The second microburst current limiter FCL2 on the branch is determined as the target current limiter. CT4 , I CT5 The value of is always in the same direction as I CT6 Reverse, that is, I CT6 The "current two-to-one" condition is met, indicating that the fault is in the node 4 area. CT6 The current limiter FCL3 on the branch line is determined as the target current limiter.

[0055] For the second microburst current limiter FCL2 on the common branch of node 2 and node 3, it can only be used as a current limiter if it is simultaneously confirmed as the target by the intelligent identification device-1 and the intelligent identification device-2 ( Figure 3 In the process, the intelligent identification device-2 outputs a handshake signal to the intelligent identification device-1, and the intelligent identification device-1 makes the final decision), and the current limiter can finally be identified as the target current limiter.

[0056] S4, if there is a target current limiter, the current characteristic quantity I of each target current limiter must be determined F Whether the respective fault threshold conditions are met I F-SET , if I F ≥I F-SET , the corresponding target current limiter can be confirmed as an actionable current limiter.

[0057] S5, outputting a driving signal to all the actionable current limiters through the output interface corresponding to the intelligent identification device.

[0058] One embodiment of the present invention provides a method for identifying the selective action of a micro-explosion current limiter for a power distribution network having only a single two-branch closely related node. Figure 4 As shown, Area A represents the old power supply system (Phase I project), and Area B represents the newly installed power supply system (Phase II project). The total short-circuit current of the Phase I project is 25kA, and the breaking capacity of all feeder circuit breakers is 31.5kA. Without considering the Phase II project, the system is safe in terms of short-circuit current interruption. Due to production needs, the Phase II project was added. The total short-circuit current of the Phase II project is 10kA, and the breaking capacity of all feeder circuit breakers in Phase II is selected to be 40kA. To ensure voltage quality and power supply reliability, Phases I and II need to be interconnected, that is, electrically connected via tie lines. Obviously, this would result in insufficient breaking capacity for all circuit breakers in Phase I. Therefore, the consideration is to deploy a first microburst current limiter (FCL1) at the tie line or bus tie position. If a short circuit occurs in Node 1 (Phase I), the first microburst current limiter (FCL1) will quickly trip and de-energize the system. However, if a short circuit occurs in Node 2 (Phase II), the first microburst current limiter (FCL1) does not need to operate. Only in this way can the fault be isolated with the lowest disturbance to the distribution network and the lowest cost. Figure 1 The process shown here constructs a method for identifying the selective action of the first microburst current limiter FCL1 (in actual operation, the core ideas contained in this method can be compiled into dedicated software and embedded with a specially designed intelligent identification device to achieve automatic detection and control), so that the microburst current limiter in the distribution network has the selective action function. The specific steps are as follows: S1, select closely related nodes: In this distribution network, node 1 and node 2 are both two-branch nodes, both containing a current limiter branch, so they can both be selected as closely related nodes. For the convenience of description, node 2 may be selected as the closely related node.

[0059] S2, determine the connection polarity of the secondary current signal of each branch: connect the two branch currents I CT2 , I CT3Connect the three input interfaces IN2 and IN3 of the intelligent identification device with correct polarity, that is, ensure that the corresponding secondary signal sampling values when the primary current of each branch flows into node 2 have the same sign at any non-zero-crossing moment.

[0060] S3, determine the current direction condition, and determine the current limiter on the branch that meets the current direction condition as the target current limiter. For two-branch nodes, the "current same direction" condition or "current reverse direction" condition should be adopted. When the sampling values of the currents of the two branches at any time (in actual operation, it can be several consecutive sampling points, the same below) are all positive or negative, that is, the "current same direction" condition is met, indicating that the fault is in the node 2 area and on the node 2 branch, there is no target current limiter at this time. When at any time, I CT2 , I CT3 The value of I is always in the opposite direction. CT2 The "current reverse" condition is met, indicating that the fault is in the node 1 area. CT2 The first microburst current limiter FCL1 on the branch line is determined as the target current limiter.

[0061] S4: If the first microburst current limiter FCL1 is confirmed as the target current limiter, it is necessary to determine I CT2 Current characteristic quantity I F Whether the fault threshold condition I is met F-SET . If I F ≥I F-SET , the first microburst current limiter FCL1 can be confirmed as an actionable current limiter.

[0062] S5: Output a drive signal to the first microburst current limiter FCL1 via the output interface of the intelligent device. The above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for identifying the selective action of a micro-explosion type current limiter, characterized in that: The following steps are involved: Determine the connection polarity of the secondary signal of each branch current according to the closely related nodes, sample the current of each branch of the closely related nodes, determine whether the sampled value of each branch current meets the current direction condition, and determine the current limiter on the branch that meets the current direction condition as the target current limiter; Calculating current characteristic quantities of each target current limiter; determining whether the current characteristic quantity meets the fault threshold condition, and determining the current limiter that meets the fault threshold condition as the actionable current limiter; Sends a drive signal to the operable current limiter.

2. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The closely associated node is a node in the power distribution network topology that is directly connected to at least one micro-explosion current limiter.

3. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The connection polarity of the secondary signals of the branch currents of the closely associated nodes satisfies the following requirement: when a short circuit fault occurs in the closely associated node region, the secondary signal sampling values corresponding to the branch currents have the same sign at any non-zero-crossing moment.

4. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The current direction condition includes a current same direction condition, a current normalization condition or a current reverse direction condition.

5. The selective action identification method for a micro-explosion current limiter according to claim 4, characterized in that: For closely connected nodes with three branches, the current direction condition is the current same direction condition or the current two-normalization condition; For closely related nodes with two branches, the current direction condition is the current same direction condition or the current reverse direction condition.

6. The selective action identification method for a micro-explosion current limiter according to claim 5, characterized in that: The current same-direction condition is that when the signs of the current sampling values of each branch are the same at any time, all micro-explosion current limiters directly connected to the closely associated node should be determined as target current limiters; The current two-normalization condition is that the current sampling values of two branches among the three branches have the same sign at any time and are opposite in sign to the sampling value of the current of the third branch, then the micro-explosion current limiter on the third branch is determined to be the target current limiter; The current reversal condition is that the signs of the current sampling values of the two branches at any time are always opposite, and the micro-explosion current limiter directly connected to the closely related node is determined as the target current limiter.

7. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The current characteristic quantities include instantaneous current value, instantaneous current change rate, small half-wave zero-crossing time span of instantaneous current value or instantaneous change rate, fast prediction of current steady-state peak value, current and current algebraic sum.

8. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The fault threshold condition is a characteristic parameter in the current characteristic quantity or a logical combination of multiple characteristic parameters in the current characteristic quantity.

9. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: The driving signal is an electrical pulse signal or an optical pulse signal.

10. The selective action identification method for a micro-explosion current limiter according to claim 1, characterized in that: For a current limiter on a common branch of two adjacent closely associated nodes, only when it is simultaneously determined as a target current limiter by the two adjacent closely associated nodes, can the current limiter be finally confirmed as the target current limiter.

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