A method for identifying selective action of a micro-explosive current limiter

Abstract

This invention discloses a method for identifying the selective operation of a micro-explosive current limiter, relating to the fields of electrical detection in power systems and control of high-voltage electrical equipment. The method includes: determining closely related nodes of the micro-explosive current limiter based on the distribution network topology; determining the connection polarity of the secondary current signals of each branch of the closely related node based on the closely related nodes; sampling the current of each branch, comparing the polarity of the secondary current signals of each branch of the closely related node to determine whether the sampled values ​​of each branch current satisfy the current direction condition, and identifying the current limiter on the branch satisfying the current direction condition as the target current limiter; calculating the current characteristic quantity of each target current limiter; determining whether the current characteristic quantity satisfies the fault threshold condition, and identifying the current limiter satisfying the fault threshold condition as an operable current limiter; sending a drive signal to the operable current limiter; and achieving selective operation of the micro-explosive current limiter, avoiding the influence of impulsive loads on the judgment results.

Description

Technical Field

[0001] This invention belongs to the field of electrical detection and high-voltage electrical equipment control technology in power systems, and relates to a method for identifying selective operation of a micro-explosive current limiter. Background Technology

[0002] During power system operation, excessive current generated by short-circuit faults can severely threaten the system's thermal and dynamic stability. Therefore, fault current limiters (FCLs) are crucial equipment for ensuring the safe and stable operation of power systems. Pyrotechnic fault current limiters (PFCLs), utilizing miniature directional blasting technology, can quickly disconnect the main conductive circuit, transferring the fault current to a parallel current-limiting fuse branch, ultimately achieving current-limiting interruption of the fault current and effectively solving the thermal and dynamic stability problems of power systems. Furthermore, compared to other current-limiting technologies, this current limiter has significant advantages in terms of mature and reliable technology and low cost, and has been widely used in power distribution systems across numerous industries, including power, chemical, metallurgical, papermaking, and sugar refining.

[0003] However, in practical engineering applications, such as bus tie locations with multiple busbars in parallel, connection points between new and old power distribution systems, interconnection of multiple power sources, and grid connection of small generating units, selective operation is often required. Since the breaking components of miniature explosive current limiters involve explosive cutting and fuse technology, they are single-use devices; once activated, they need to be replaced, which undoubtedly increases maintenance costs. However, existing miniature explosive current limiters only control a single current limiter during selective operation identification, failing to perform regional selective operation identification. This results in high maintenance costs and makes it difficult to meet the needs of complex application scenarios, becoming a technical bottleneck restricting further optimization. Therefore, finding a method to solve the selective operation problem of miniature explosive current limiters has significant practical significance and application value. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of existing technologies where selective action recognition of micro-explosive current limiters only considers the control of a single current limiter, resulting in high maintenance costs and an inability to accurately meet the needs of complex application scenarios under network topology through the identification and control of regional selective actions. The invention provides a method for identifying selective actions of micro-explosive current limiters.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for identifying the selective action of a micro-explosive current limiter, comprising the following steps:

[0007] The connection polarity of the secondary signal of the current of each branch is determined based on the closely related nodes. The current of each branch of the closely related nodes is sampled, and it is determined whether the sampled value of the current of each branch satisfies the current direction condition. The current limiter on the branch that satisfies the current direction condition is determined as the target current limiter.

[0008] Calculate the current characteristic of each target current limiter;

[0009] Determine whether the current characteristic quantity meets the fault threshold condition, and identify the current limiter that meets the fault threshold condition as an operable current limiter;

[0010] Send a drive signal to the operable current limiter.

[0011] Furthermore, the closely associated node is a node in the power distribution network topology that is directly connected to at least one micro-explosive current limiter.

[0012] Furthermore, the connection polarity of the secondary signals of the branch currents of the closely associated node satisfies the following condition: when a short-circuit fault occurs in the region of the closely associated node, the sampled values ​​of the secondary signals corresponding to the branch currents have the same sign at any non-zero crossing time.

[0013] Furthermore, the current direction conditions include current in the same direction, current in two directions being equal, or current in opposite directions.

[0014] Furthermore, for closely related nodes with three branches, the current direction condition is either the current in the same direction or the current in two directions being equal.

[0015] For closely related nodes with two branches, the current direction condition is either the current in the same direction or the current in opposite directions.

[0016] Furthermore, the current unidirectional condition is that if the signs of the current sampling values ​​of each branch are the same at any time, then all micro-explosion type current limiters directly connected to the closely related node should be identified as target current limiters.

[0017] The current uniformity condition is that the current sampling values ​​of two out of the three branches have the same sign at any time, and the sign of the current sampling value of the third branch is opposite to that of the third branch. Then, the micro-explosion type current limiter on the third branch is determined as the target current limiter.

[0018] If the current reversal condition is that the signs of the current sampling values ​​of the two branches are always opposite at any time, then the micro-explosion type current limiter directly connected to the closely related node is determined as the target current limiter.

[0019] Furthermore, the current characteristic quantities include instantaneous current value, instantaneous rate of change of current, small half-wave zero-crossing time span of instantaneous current value or rate of change of current, rapid prediction of steady-state peak current, current and algebraic sum of current.

[0020] Furthermore, the fault threshold condition is a single characteristic parameter in the current characteristic quantity or a logical combination of multiple characteristic parameters in the current characteristic quantity.

[0021] Furthermore, the driving signal is an electrical pulse signal or an optical pulse signal.

[0022] Furthermore, for a current limiter on a common branch of two adjacent closely related nodes, the current limiter can only be ultimately confirmed as a target current limiter if it is simultaneously identified as such by the two adjacent closely related nodes.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention discloses a method for identifying the selective action of micro-explosive current limiters. It determines the closely associated nodes of the micro-explosive current limiters through the distribution network topology and clarifies the polarity of the secondary signal connections for each branch current. Combined with current direction conditions, it filters the target current limiter, establishing a mapping rule between the number of branches in the topology node and the current direction condition. Based on the dynamic filtering rule of the number of branches in the node, it can select one of the multiple micro-explosive current limiters under the same closely associated node as the target current limiter for action. Using this method, only one control system needs to be deployed at the closely associated node, and one controller... This system can control multiple micro-explosive current limiters on each branch of a closely related node, eliminating the need for a separate control system at each micro-explosive current limiter and thus saving implementation costs. Furthermore, for multiple micro-explosive current limiters on each branch of a closely related node, this invention only requires collecting the current of each branch to control multiple current limiters. Compared to existing micro-explosive current limiter control methods, which require a separate control system for each current limiter and measurements of the current and port current of each current limiter, this invention is easier to implement and significantly reduces maintenance costs.

[0025] Using the method of this invention, a single control system can identify whether the micro-explosive current limiters in each branch of a closely related node are target current limiters, thus completing fault isolation in the area of ​​that closely related node. This eliminates the need to install a control system on each micro-explosive current limiter. For multi-node topologies, the determination of the target current limiter at each node does not depend on the determination of other nodes, making it easy to implement. This invention determines the target current limiter by checking whether the current conditions of each branch at the closely related node meet the current direction condition. By comparing the current characteristics of the target current limiter with the fault threshold, the influence of each branch of the closely related node is considered, enabling precise location of the specific fault area. This avoids large-scale power outages caused by ambiguous fault location and significantly improves fault diagnosis and repair efficiency. Based on the dual judgment mechanism of current direction condition and fault threshold condition, it effectively distinguishes between normal operating current fluctuations and actual fault current, preventing the current limiter from triggering unnecessarily, reducing unnecessary equipment operation losses and power outage losses, and improving the stability and reliability of the power distribution system. This method rapidly samples and judges the current in each branch, quickly filters out operable current limiters that meet the conditions, and promptly sends drive signals to achieve rapid fault isolation, shorten fault duration, reduce the impact of faults on the power distribution system and electrical equipment, reduce system disturbances, and enhance system stability. It ensures that the current limiter operates only when necessary, reducing the impact of frequent current limiter operation on the system, extending equipment lifespan, and lowering maintenance costs. It also guarantees continuous power supply to non-faulty areas, improving the power supply continuity and operational efficiency of the entire power distribution network.

[0026] Furthermore, by clearly defining the "current in the same direction condition," "current two-to-one condition," and "current in opposite directions condition," differentiated judgment rules are formulated for closely related nodes with different numbers of branches, enabling precise identification of the flow characteristics of fault current. In a scenario with three branches, the faulty branch can be accurately identified using the current in the same direction condition or the current two-to-one condition; with two branches, the faulty area can be quickly located based on the current in the same direction or in opposite directions condition, greatly improving the precision and accuracy of fault location. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the selective action identification method for micro-explosive current limiters according to the present invention;

[0029] Figure 2This embodiment of the invention is for a power distribution network with only a single, closely connected three-branch node;

[0030] Figure 3 This embodiment of the invention is for a power distribution network with three closely related nodes of adjacent branches and a common current limiter branch;

[0031] Figure 4 This embodiment of the invention is for a power distribution network with only a single, closely connected node between two branches. Wherein, FCL1 is the first micro-explosion current limiter; FCL2 is the second micro-explosion current limiter; and FCL3 is the third micro-explosion current limiter. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and marked in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] It should be noted that all current limiters mentioned in the embodiments of the present invention are micro-explosive current limiters.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings:

[0037] See Figure 1 This invention discloses a method for identifying the selective action of a micro-explosive current limiter, comprising the following steps:

[0038] Step 1: Determine the closely associated nodes of the micro-explosive current limiters based on the distribution network topology. The principle for determining closely associated nodes is that the node must be directly connected to at least one micro-explosive current limiter, i.e., there must be at least one micro-explosive current limiter branch. Nodes with multiple micro-explosive current limiter branches are preferred as closely associated nodes, and the total number of branches of the node should be 2 or 3. Each branch current includes three phases A, B, and C. For distribution systems where the neutral point is grounded through an arc suppression coil or high-resistance grounding, the current of each branch can be any two phases.

[0039] Step 2: Determine the connection polarity of the secondary signals of the branch currents of the closely associated nodes; the connection polarity of the secondary signals of the branch currents should satisfy the following: when a short-circuit fault occurs in the area of ​​the closely associated node, the sampled values ​​of the secondary signals corresponding to the branch currents have the same sign at any non-zero crossing time.

[0040] Step 3: Sample the current of each branch. Based on the polarity identification of the secondary signal of the current of each branch of closely related nodes, determine whether the sampled value of the current of each branch meets the current direction condition. The current limiter on the branch that meets the current direction condition is identified as the target current limiter.

[0041] The current direction conditions are as follows: for a node with three closely connected branches, the current direction conditions are either the current in the same direction or the current in two directions being equal; for a node with two closely connected branches, the current direction conditions are either the current in the same direction or the current in opposite directions.

[0042] The condition for current in the same direction is that the current sampling values ​​of each branch are of the same sign at any time. Then, all current limiters directly connected to this closely related node should be identified as target current limiters.

[0043] The current uniformity condition is that at any given time, the signs of the sampled current values ​​of two branches are always the same, and the signs are opposite to those of the sampled current value of the third branch. In this case, the current limiter on the third branch is determined to be the target current limiter.

[0044] The current reversal condition applies only to nodes with two closely connected branches. If the signs of the sampled current values ​​of the two branches are always opposite at any given time, then the current limiter directly connected to that closely connected node is determined as the target current limiter.

[0045] Specifically, for a current limiter on a common branch of two adjacent closely related nodes, the current limiter can only be finally identified as the target current limiter if it is simultaneously identified as the target current limiter by the two adjacent closely related nodes.

[0046] Step 4: Calculate the current characteristic quantities of each target current limiter. Specifically, the current characteristic quantities may include the instantaneous current values. Instantaneous value of current change rate The instantaneous value of the current or the instantaneous rate of change of the current is less than the zero-crossing time span of the half-wave. Fast prediction of steady-state peak current Current and the algebraic sum of currents These are isoparameters, and these characteristic quantities can be obtained through sampling the current values. Assume the expression for the phase A current signal of a target current limiter branch is as follows:

[0047] (1)

[0048] In the formula, This represents the peak value of the fault current. This represents the peak operating current before the fault. Angular frequency, The system voltage phase angle at the moment of short circuit. The power factor angle of the short-circuit loop. The power factor angle is the angle of normal operation before the short circuit. It is a sine function. For Euler number, is the time constant of the circuit.

[0049] Then the first differential signal of the instantaneous value of the current for:

[0050]

[0051] in, It is a cosine function. It is the first differential signal of the instantaneous value of the current.

[0052] Ignoring aperiodic components, we get:

[0053] (2)

[0054] The second-order differential signal of the instantaneous current value The expression is as follows:

[0055]

[0056] in, It is the second derivative of the instantaneous value of the current.

[0057] Ignoring aperiodic components, we get:

[0058] (3)

[0059] Combining equations (2) and (3), we can obtain:

[0060] (4)

[0061] Based on the instantaneous value of the current sampling interval From the sampled array sequence, we can obtain , An array sequence of values, as shown in the example below:

[0062] , , , , , , , , , …

[0063] , , , , , , , …

[0064] , , , , , …

[0065] in, , , , , , , , , , Instantaneous value of current by For each sampling interval, there are 10 sampled values; , , , , , , , The first differential signal of the instantaneous value of the current an array sequence; , , , , , The second derivative signal of the instantaneous value of the current An array sequence.

[0066] by Taking time as an example, it is obvious that the time (i.e.) can be obtained. (moment) and value:

[0067] (5)

[0068] (6)

[0069] Substituting equations (5) and (6) into equation (4), we can obtain The predicted value.

[0070] In addition, according to the above sampling interval The sampled array sequence and the result obtained after digitization Array sequences can be detected and The time span between the first two zero crossings :

[0071]

[0072] in, The sampling interval is... For the first zero crossing, This is the second zero-crossing point. The specific criteria for zero-crossing are:

[0073] For the instantaneous value of current :

[0074] First crossing of zero: × ≤0

[0075] Second crossing of zero: × ≤0

[0076] in, The instantaneous value of the current at the first zero-crossing point. The instantaneous current value at the sampling moment preceding the first zero-crossing point. This is the instantaneous value of the current at the second zero-crossing point. It is the instantaneous current value at the sampling moment preceding the second zero-crossing point.

[0077] For the instantaneous rate of change of current :

[0078] First crossing of zero: × ≤0

[0079] Second crossing of zero: × ≤0

[0080] in, The instantaneous rate of change of current at the first zero-crossing point. The instantaneous rate of change of current at the sampling moment preceding the first zero-crossing point. The instantaneous rate of change of current at the second zero-crossing point. The instantaneous rate of change of current at the sampling moment preceding the second zero-crossing point.

[0081] Similarly, based on the sampled values ​​of the current in each branch, the algebraic sum of the currents can be easily obtained. Assuming the closely associated node is a 3-branch closely associated node, the A-phase current of each branch is... The sampled values ​​are respectively , , ,but .

[0082] Step 5: Determine whether the current characteristic quantity meets the fault threshold condition, and identify the current limiter that meets the fault threshold condition as an operable current limiter; the fault threshold condition can be the threshold condition of a certain parameter in the current characteristic quantity, or it can be a logical combination of multiple parameter threshold conditions.

[0083] For example: ≥i set AND ≥[ ] set

[0084] For example: { ≥i set OR 1ms≤ ≤5ms}AND{ ≥[ ] set OR ≥I set}

[0085] Among them, i set The fault threshold representing the instantaneous value of the current; ] set The fault threshold representing the instantaneous rate of change of current; I set The fault threshold for rapid prediction of steady-state peak current is represented by AND, which indicates a logical AND operation, and OR, which indicates a logical OR operation.

[0086] Step 6: Output a drive signal to all operable current limiters. The drive signal can be an electrical pulse signal or an optical pulse signal. Optical pulse signals have stronger anti-electromagnetic interference performance and superior high-low potential isolation performance. This signal can be used as the operation criterion for the current limiter, or it can be used only as an auxiliary criterion for the current limiter's operation. When the drive signal is used only as an auxiliary criterion for the current limiter's operation, the threshold condition mentioned in Step 5 mainly serves to resist interference and avoid malfunctions, because the current direction condition may also be satisfied under normal operating conditions. In this case, the current threshold condition must be used as a lockout.

[0087] One embodiment of the present invention provides a method for identifying the selective operation of a micro-explosive current limiter in a power distribution network with only a single closely related three-branch node. For example... Figure 2 As shown, T1, T2, and T3 are all transformers, each with nodes connected to current limiters. Each node branch is equipped with a current transformer (CT). A short circuit in node 1 requires only the first micro-explosive current limiter FCL1 to operate; a fault in node 2 requires both the first and second micro-explosive current limiters FCL1 and FCL2 to operate; and a fault in node 3 requires only the second micro-explosive current limiter FCL2 to operate. Only in this way can faults be isolated with minimal disturbance to the distribution network and at the lowest cost. Based on the selective operation identification method for micro-explosive current limiters described in this invention, a selective operation identification method for the first and second micro-explosive current limiters FCL1 and FCL2 is constructed (in practice, 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), enabling the micro-explosive current limiters in this distribution network to have selective operation functionality. The specific steps are as follows:

[0088] S1, Select closely related nodes: Node 2 is a three-branch node, containing two current limiter branches, so Node 2 should be the only closely related node.

[0089] S2, Determine the connection polarity of the secondary signals of the three branch currents: I3 = I4 = I5 = I6 = I7 = I8 = I9 = I1 = I2 = I3 = I4 = I5< / CT2 I CT3 I CT4 (This current is measured by the current transformers on each branch, i.e., 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 secondary signal sampling value corresponding to the primary current flowing into node 2 of each branch has the same sign at any non-zero crossing moment.

[0090] S3, determine the current direction condition, and identify the current limiter on the branch that meets the current direction condition as the target current limiter. For a three-branch node, the "current in the same direction" condition or the "current two to one" condition should be used. When the sampled values ​​of the currents in the three branches are all positive or all negative at any time (in actual operation, this can be several consecutive sampling points, the same below), the "current in the same direction" condition is met, indicating that the fault is in the node 2 area, and the first micro-explosive current limiter FCL1 and the second micro-explosive current limiter FCL2 on the node 2 branch can be identified as the target current limiters. When at any time, I CT3 I CT4 The values ​​are always in the same direction, while those of I are... CT2 Always in the opposite direction, i.e., I CT2 The fact that the "current convergence" condition is met indicates that the fault is in the node 1 region, and I can be... CT2 The first micro-explosion current limiter FCL1 on the branch is identified as the target current limiter. At any given time, I... CT2 I CT3 The values ​​are always in the same direction, while those of I are... CT4 Always in the opposite direction, i.e., I CT4 The fact that the "current convergence" condition is met indicates that the fault is in the node 3 region, and I can be... CT4 The second micro-explosion current limiter FCL2 on the branch line was identified as the target current limiter.

[0091] S4, if a target current limiter exists, then the current characteristic quantity I of each target current limiter needs to be determined. F Does the fault threshold condition I meet? F-SET , if I F ≥I F-SET Then the corresponding target current limiter can be identified as an operable current limiter.

[0092] S5 outputs a drive signal to the operable current limiter through the output interface of the smart device.

[0093] One embodiment of the present invention provides a method for identifying the selective operation of a micro-explosive current limiter in a power distribution network with closely related nodes of three adjacent branches and a common current limiter branch. For example... Figure 3As shown, a short circuit in node 1 requires only the operation of the first micro-explosive current limiter FCL1; a fault in node 2 requires only the operation of the first micro-explosive current limiter FCL1 and the second micro-explosive current limiter FCL2; a fault in node 3 requires only the operation of the second micro-explosive current limiter FCL2 and the third micro-explosive current limiter FCL3; and a fault in node 4 requires only the operation of the third micro-explosive current limiter FCL3. Only in this way can faults be isolated with minimal disturbance to the distribution network and at the lowest cost. Based on the steps described in this invention, a method for identifying the selective operation of the first micro-explosive current limiter FCL1, the second micro-explosive current limiter FCL2, and the third micro-explosive current limiter FCL3 is constructed (in practice, 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), enabling the micro-explosive current limiters in the distribution network to have selective operation functionality. The specific steps are as follows:

[0094] S1, Select closely related nodes: Node 2 and Node 3 are both three-branch nodes, and each node contains two current limiter branches. Therefore, Node 2 and Node 3 should be selected as closely related nodes, and the FCL2 branch is the common branch of these two nodes.

[0095] S2, determine the connection polarity of the secondary signals of each branch current: connect the three branch currents I of closely related node 2. CT2 I CT3 I CT4 Connect the three input interfaces IN1, IN2, and IN3 of the intelligent identification device-1 with the correct polarity. This ensures that the secondary signal sampling value corresponding to the primary current flowing into node 2 of each branch has the same sign at any non-zero crossing moment. Connect the three branch currents I of closely related node 3. CT4 I CT5 I CT6 Connect the three input interfaces IN1, IN2 and IN3 of the intelligent identification device-2 with the correct polarity, which ensures that the secondary signal sampling value corresponding to the primary current flowing into node 3 of each branch has the same sign at any non-zero crossing moment.

[0096] S3, determine the current direction condition, and identify 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 uniformity condition should be used.

[0097] For node 2, when the three-branch current I CT2 I CT3 I CT4If the sampled values ​​at any given time (in practice, this can be several consecutive sampling points, the same applies below) are all positive or all negative, then the "current in the same direction" condition is met, indicating that the fault is in the node 2 region. The first micro-explosive current limiter FCL1 and the second micro-explosive current limiter FCL2 on the node 2 branch can both be identified as target current limiters. When at any given time, I... CT3 I CT4 The values ​​are always in the same direction as I. CT2 Reverse, i.e., I CT2 The fact that the "current convergence" condition is met indicates that the fault is in the node 1 region, and I can be... CT2 The first micro-explosion current limiter FCL1 on the branch is identified as the target current limiter. At any given time, I... CT2 I CT3 The values ​​are always in the same direction as I. CT4 Reverse, i.e., I CT4 If the "current convergence" condition is met, it indicates that the fault is in the node 3 or node 4 region, and I can be... CT4 The second micro-explosion current limiter FCL2 on the branch line was identified as the target current limiter.

[0098] For node 3, when the three-branch current I CT4 I CT5 I CT6 The sampled values ​​at any given time all have the same sign, satisfying the "current in the same direction" condition, indicating that the fault is in the node 3 region. The first micro-explosive current limiter FCL1 and the second micro-explosive current limiter FCL2 on the node 2 branch can both be identified as the target current limiters. When at any given time, I... CT5 I CT6 The values ​​are always in the same direction as I. CT4 Reverse, i.e., I CT4 If the "current convergence" condition is met, it indicates that the fault is in the region of node 2 or node 1, and I can be... CT4 The second micro-explosion current limiter FCL2 on the branch is determined as the target current limiter. At any given time, I... CT4 I CT5 The values ​​are always in the same direction as I. CT6 Reverse, i.e., I CT6 The fact that the "current convergence" condition is met indicates that the fault is in the node 4 region, and I can be... CT6 The current limiter FCL3 on the branch line is identified as the target current limiter.

[0099] For the second micro-explosive current limiter FCL2 on the common branch of nodes 2 and 3, it is only used as a current limiter when it is simultaneously identified as a target by both intelligent identification device-1 and intelligent identification device-2. Figure 3 In the process of intelligent identification device-2 outputting a handshake signal to intelligent identification device-1 (and intelligent identification device-1 making the final decision), the current limiter can finally be identified as the target current limiter.

[0100] S4, if a target current limiter exists, then the current characteristic quantity I of each target current limiter must be determined. F Do they meet their respective fault threshold conditions? F-SET , if I F ≥I F-SET Then the corresponding target current limiter can be identified as an operable current limiter.

[0101] S5 outputs drive signals to all operable current limiters through the output interface corresponding to the intelligent identification device.

[0102] One embodiment of the present invention provides a method for identifying the selective operation of a micro-explosive current limiter in a power distribution network with only a single, closely connected node between two branches. For example... Figure 4 As shown, Area A is the old power system (Phase I), and Area B is the new power system (Phase II). The total short-circuit current of Phase I is 25kA, and the breaking capacity of all feeder circuit breakers is 31.5kA. Without considering Phase II, the system is safe in terms of short-circuit current breaking capacity. Due to production needs, Phase II is added, with a total short-circuit current of 10kA. The breaking capacity of all feeder circuit breakers in Phase II is selected to be 40kA. To ensure voltage quality and power supply reliability, Phase I and Phase II need to be interconnected, i.e., electrically connected via a tie line. Obviously, this will result in insufficient breaking capacity for all circuit breakers in Phase I. Therefore, it is considered to configure a first micro-explosive current limiter (FCL1) at the tie line or bus tie location. In the event of a short-circuit fault in Node 1 (Phase I), the first micro-explosive current limiter (FCL1) will quickly disconnect the system. However, in the event of a short circuit in Node 2 (Phase II), the first micro-explosive current limiter (FCL1) does not need to operate. Only in this way can faults be isolated with minimal disturbance to the power distribution network and at the lowest cost. This is based on the steps described in the present invention. Figure 1 The process shown constructs a method for identifying the selective action of the first micro-explosive current limiter FCL1 (in actual operation, the core ideas contained in this method can be developed into dedicated software and embedded with a specially designed intelligent identification device to achieve automatic detection and control), enabling the micro-explosive current limiter in the power distribution network to have selective action function. The specific steps are as follows:

[0103] S1. Select closely related nodes: In this power distribution network, both node 1 and node 2 are two-branch nodes, each containing a current limiter branch, so both can be selected as closely related nodes. For the sake of convenience, we can choose node 2 as the closely related node.

[0104] S2, Determine the connection polarity of the secondary signals of the current in each branch: Connect the two branch currents I CT2 I CT3Connect the three input interfaces IN2 and IN3 of the intelligent identification device with the correct polarity, which ensures that the secondary signal sampling value corresponding to the primary current flowing into node 2 of each branch has the same sign at any non-zero crossing moment.

[0105] S3, determine the current direction condition, and identify the current limiter on the branch that meets the current direction condition as the target current limiter. For two-branch nodes, the "current in the same direction" condition or the "current in opposite directions" condition should be used. When the sampled values ​​of the currents of the two branches are both positive or both negative at any time (in actual operation, this can be several consecutive sampling points, the same below), the "current in the same direction" condition is met, indicating that the fault is in the node 2 region, and there is no target current limiter on the node 2 branch. When at any time, I CT2 I CT3 The value of I is always in the opposite direction. CT2 The fact that the "current reverse" condition is met indicates that the fault is in the node 1 region, and I can be... CT2 The first micro-explosion current limiter FCL1 on the branch is identified as the target current limiter.

[0106] S4, if the first micro-explosion current limiter FCL1 is identified as the target current limiter, then it is necessary to determine I. CT2 Current characteristic quantity I F Does the fault threshold condition I meet? F-SET . If I F ≥I F-SET Then the first micro-explosion current limiter FCL1 can be identified as an operable current limiter.

[0107] S5, a drive signal is output to the first micro-explosion current limiter FCL1 through the output interface of the intelligent device. The above are merely preferred embodiments of the present invention and are not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for identifying the selective action of a micro-explosive current limiter, characterized in that, Includes the following steps: The connection polarity of the secondary signals of the branch currents is determined based on the closely associated nodes. The currents of each branch of the closely associated nodes are sampled, and it is determined whether the sampled values ​​of each branch current satisfy the current direction condition. The current limiters on the branches that satisfy the current direction condition are identified as the target current limiters. The closely associated nodes are nodes in the distribution network topology that are directly connected to at least one micro-explosive current limiter. The connection polarity of the secondary signals of the branch currents of the closely associated nodes satisfies the following condition: when a short-circuit fault occurs in the area where the closely associated node is located, the sampled values ​​of the secondary signals corresponding to the branch currents have the same sign at any non-zero crossing time. The current direction condition includes the current in the same direction condition, the current two-to-one condition, or the current in opposite directions condition. Specifically: For closely related nodes with 3 branches, the current direction condition is either the current in the same direction condition or the current in two directions being equal. For closely related nodes with two branches, the current direction condition is either the current in the same direction or the current in opposite directions. The current unidirectional condition is that if the signs of the current sampling values ​​of each branch are the same at any time, then all micro-explosion type current limiters directly connected to the closely related node should be identified as target current limiters. The current uniformity condition is that if the current sampling values ​​of two branches in the three branches have the same sign at any time and the sign of the current sampling value of the third branch is opposite, then the micro-explosion type current limiter on the third branch is determined as the target current limiter. The current reversal condition is that the signs of the current sampling values ​​of the two branches are always opposite at any time. Then, the micro-explosion type current limiter directly connected to the closely related node is determined as the target current limiter. Calculate the current characteristic of each target current limiter; Determine whether the current characteristic quantity meets the fault threshold condition, and identify the current limiter that meets the fault threshold condition as an operable current limiter; Send a drive signal to the operable current limiter.

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

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

4. The method for identifying selective action of a micro-explosive current limiter according to claim 1, characterized in that, The driving signal is an electrical pulse signal or an optical pulse signal.

5. The method for identifying selective action of a micro-explosive current limiter according to claim 1, characterized in that, For a current limiter on a common branch of two adjacent closely related nodes, the current limiter can only be finally identified as the target current limiter if it is simultaneously identified as the target current limiter by the two adjacent closely related nodes.

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