A method and system for limiting short-circuit current in a power system

Abstract

The present invention discloses a method and system for limiting short-circuit current in a power system, including: obtaining the switch current and bus voltage of each switch in a substation, judging whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determining the fault type and fault location when a fault occurs; comparing the fault type and fault location with the target fault type and target fault location where the short-circuit current exceeds the standard when the switch is opened, to determine whether there is a situation where the short-circuit current exceeds the standard when the switch is opened; when it is determined that there is a situation where the short-circuit current exceeds the standard when the switch is opened, matching according to the fault type, fault location and preset opened branches corresponding to different types of faults occurring at different positions to determine the target opened branch; before the conventional circuit breaker completes opening, disconnecting the target opened branch to limit the short-circuit current in the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and more particularly, to a method and system for limiting short-circuit current in a power system. Background Art

[0002] With the rapid development of the power grid, the scale of the power grid is increasing day by day, and the short-circuit current level in China's power system has been increasing year by year. Excessive short-circuit current will pose hazards to the safe and stable operation of the power system and the electrical equipment itself. To ensure the safe operation of the power system, it is necessary to strengthen or replace the electrical equipment in the power grid to solve the problem caused by the excessive short-circuit current. On the one hand, this will lead to a significant increase in the investment and technical requirements for electrical equipment in the system. In addition, due to the limitation of the breaking capacity of the circuit breaker, there may be no suitable circuit breaker available. Therefore, to avoid a series of hazards caused by excessive short-circuit current, how to limit the short-circuit current level within the safety margin has become a problem that must be solved in the development of contemporary power grids.

[0003] The conventional control means for short-circuit current adopted in the actual power system mainly include line outage, installation of current-limiting reactors, etc. After adopting the above measures, problems such as decreased power supply reliability and increased system loss often occur. Conventional fault current limiters are relatively less applied at the 500 kV level, and are often costly, occupy a large area, and are difficult to promote and apply.

[0004] When a short-circuit grounding fault occurs in the power system, a short-circuit current will pass through the fault point. When the short-circuit current level exceeds the breaking capacity of the circuit breaker, the short-circuit may not be interrupted. Currently, the short-circuit current level that a conventional circuit breaker can interrupt generally does not exceed 63 kA. When the short-circuit current level exceeds 63 kA, relevant current-limiting measures need to be taken. Summary of the Invention

[0005] The present invention provides a method and system for limiting short-circuit current in a power system to solve the problem of how to limit the short-circuit current in the power system.

[0006] To solve the above problems, according to one aspect of the present invention, a method for limiting short-circuit current in a power system is provided, the method comprising:

[0007] Obtaining the switch current and bus voltage of each switch in the substation, judging whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determining the fault type and fault location when a fault occurs;

[0008] Comparing the fault type and fault location with the target fault type and target fault location where the short-circuit current exceeds the standard when the switch is opened preset, and determining whether there is a situation where the short-circuit current exceeds the standard when the switch is opened;

[0009] When it is determined that the short - circuit current interrupted by the switch exceeds the standard, match according to the fault type, fault location, and the preset interrupted branch corresponding to different types of faults occurring at different locations to determine the target interrupted branch;

[0010] Before the conventional circuit breaker completes opening, disconnect the target interrupted branch to limit the short - circuit current of the power system.

[0011] Preferably, the method of judging whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determining the fault type and fault location when a fault occurs includes:

[0012] When the instantaneous value of the single - phase switch current is greater than or equal to the preset instantaneous current threshold, or the current rising rate exceeds the preset rising rate threshold, or the bus voltage is less than or equal to the preset bus voltage threshold, it is determined that a fault occurs, and the fault type is a single - phase fault;

[0013] When the instantaneous value of the three - phase switch current is greater than or equal to the preset instantaneous current threshold, or the current rising rate exceeds the preset rising rate threshold, or the bus voltage is less than or equal to the preset bus voltage threshold, it is determined that a fault occurs, and the fault type is a three - phase fault;

[0014] Determine the branch current of each branch according to the switch current, and compare it with the first short - circuit current of each branch preset for different types of faults occurring at different locations according to the DC circuit to determine the fault location.

[0015] Preferably, the method further includes:

[0016] Establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short - circuit current interrupted by each switch when different types of faults occur at different locations;

[0017] Select the fault type and fault location corresponding to the second short - circuit current greater than or equal to the preset second short - circuit current threshold as the target fault type and target fault location where the short - circuit current interrupted by the switch exceeds the standard.

[0018] Preferably, the method further includes:

[0019] Sort the first short - circuit current of each branch when any type of fault occurs at any location in descending order to determine the branch sequence, and initialize i = 1;

[0020] Select the i - th branch in the branch sequence as the current key branch;

[0021] Disconnect the current key branch, and obtain the third short - circuit current interrupted by the switch and the system stability level when different types of faults occur at different locations;

[0022] When the third short - circuit current is less than the third short - circuit current threshold and the system stability is stable, determine the current critical branch as the target opening branch; otherwise, update i = i + 1, and re - determine the current critical branch until the third short - circuit current is less than the third short - circuit current threshold and the system stability is stable, and determine the current critical branch as the opening branch corresponding to any type of fault occurring at any position.

[0023] Preferably, the method further includes:

[0024] Establish a simulation model based on the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the first short - circuit current of each branch when different types of faults occur at different positions.

[0025] Preferably, the method further includes:

[0026] After the fault is removed, judge the reclosing conditions, and when the bus voltage returns to normal, restore the conduction of the target opening branch.

[0027] Preferably, the method further includes:

[0028] If the fault type is a single - phase fault and the fault location is a transmission line, judge the reclosing conditions after the opening time of the target opening branch reaches the first preset time threshold; otherwise, judge the reclosing conditions after the opening time of the target opening branch reaches the second preset time threshold.

[0029] According to another aspect of the present invention, a system for limiting the short - circuit current of a power system is provided, and the system includes:

[0030] A fault determination unit, configured to obtain the switch current and bus voltage of each switch in the substation, judge whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determine the fault type and fault location when a fault occurs;

[0031] A short - circuit current over - standard judgment unit, configured to compare the fault type and fault location with the target fault type and target fault location where the short - circuit current exceeds the standard when the switch is opened preset, and determine whether there is a situation where the short - circuit current exceeds the standard when the switch is opened;

[0032] A target opening branch determination unit, configured to, when it is determined that there is a situation where the short - circuit current exceeds the standard when the switch is opened, perform matching according to the fault type, fault location, and the corresponding opening branch preset when different types of faults occur at different positions, and determine the target opening branch;

[0033] An action unit, configured to disconnect the target opening branch before the conventional circuit breaker completes opening to limit the short - circuit current of the power system.

[0034] Preferably, the fault determination unit determines whether a grounding fault occurs in the power system according to the switching current and the bus voltage, and determines the fault type and the fault location when a fault occurs, including::

[0035] When the instantaneous value of the switching current of a single phase is greater than or equal to the preset current instantaneous threshold, or the current rising rate exceeds the preset rising rate threshold, or the bus voltage is less than or equal to the preset bus voltage threshold, it is determined that a fault occurs, and the fault type is a single-phase fault;

[0036] When the instantaneous values of the switching currents of three phases are greater than or equal to the preset current instantaneous threshold, or the current rising rate exceeds the preset rising rate threshold, or the bus voltage is less than or equal to the preset bus voltage threshold, it is determined that a fault occurs, and the fault type is a three-phase fault;

[0037] Determine the branch current of each branch according to the switching current, and compare it with the first short-circuit current of each branch when different types of faults occur at different positions according to the DC circuit to determine the fault location.

[0038] Preferably, the system further includes::

[0039] A second short-circuit current determination unit, configured to establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short-circuit current of each switch opening when different types of faults occur at different positions;

[0040] A target fault type and location determination unit, configured to select the fault type and the fault location corresponding to the second short-circuit current greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault location where the short-circuit current of the switch opening exceeds the standard.

[0041] Preferably, the system further includes: a branch opening determination unit, configured to::

[0042] Sort the first short-circuit currents of each branch when any type of fault occurs at any position in descending order to determine the branch sequence, and initialize i = 1;

[0043] Select the i-th branch in the branch sequence as the current key branch;

[0044] Disconnect the current key branch, and obtain the third short-circuit current of the switch opening and the system stability level when different types of faults occur at different positions;

[0045] When the third short - circuit current is less than the third short - circuit current threshold and the system stability is stable, determine the current critical branch as the target opening branch; otherwise, update \(i = i + 1\), and re - determine the current critical branch until the third short - circuit current is less than the third short - circuit current threshold and the system stability is stable, then determine the current critical branch as the opening branch corresponding to any type of fault occurring at any position.

[0046] Preferably, the system further includes:

[0047] A first short - circuit current determination unit, configured to establish a simulation model based on the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the first short - circuit current of each branch when different types of faults occur at different positions.

[0048] Preferably, the system further includes:

[0049] A restoration unit, configured to, after the fault is removed, judge the reclosing condition, and when the bus voltage returns to normal, restore the conduction of the target opening branch.

[0050] Preferably, the restoration unit further includes:

[0051] If the fault type is a single - phase fault and the fault location is a transmission line, then judge the reclosing condition after the opening time of the target opening branch reaches the first preset time threshold; otherwise, judge the reclosing condition after the opening time of the target opening branch reaches the second preset time threshold.

[0052] The present invention provides a method and system for limiting the short - circuit current of a power system, including: obtaining the switch current and bus voltage of each switch in a substation, judging whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determining the fault type and fault location when a fault occurs; determining whether there is an excessive short - circuit current interruption by a switch according to the fault type and fault location; when it is determined that there is an excessive short - circuit current interruption by a switch, match according to the fault type, fault location and the preset opening branches corresponding to different types of faults occurring at different positions to determine the target opening branch; before the conventional circuit breaker completes opening, disconnect the target opening branch to limit the short - circuit current of the power system. The method of the present invention can quickly detect faults, determine the fault location and type, and quickly open the target opening branch, thereby limiting the short - circuit current, reducing the short - circuit current interruption level of the system circuit breaker, and ensuring the safety of the system and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] By referring to the following drawings, the exemplary embodiments of the present invention can be more completely understood:

[0054] Figure 1 Flow chart of method 100 for limiting short - circuit current in a power system according to an embodiment of the present invention;

[0055] Figure 2 Schematic wiring diagram of a typical 500 kV system according to an embodiment of the present invention;

[0056] Figure 3 Control schematic diagram of the device for limiting short - circuit current according to an embodiment of the present invention;

[0057] Figure 4 Schematic diagram of suppressing short - circuit current in a 500 kV system according to an embodiment of the present invention;

[0058] Figure 5 Schematic structural diagram of system 500 for limiting short - circuit current in a power system according to an embodiment of the present invention. Detailed implementation manners

[0059] Now, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the drawings are not limitations on the present invention. In the drawings, the same units / components are denoted by the same reference numerals.

[0060] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the art. Additionally, it can be understood that terms defined in commonly used dictionaries should be construed as having a meaning consistent with the context of their relevant fields, and should not be construed as having an idealized or overly formal meaning.

[0061] Figure 1 Flow chart of method 100 for limiting short - circuit current in a power system according to an embodiment of the present invention. As Figure 1 shown, the method 100 for limiting short - circuit current in a power system provided by the embodiment of the present invention starts at step 101. At step 101, the switch currents and bus voltages of each switch in the substation are obtained, and based on the switch currents and bus voltages, it is determined whether a ground fault has occurred in the power system, and when a fault occurs, the fault type and fault location are determined.

[0062] Preferably, the determining whether a ground fault has occurred in the power system based on the switch currents and bus voltages, and determining the fault type and fault location when a fault occurs, includes:

[0063] When the instantaneous value of the switching current of a single phase is greater than or equal to a preset instantaneous current threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, it is determined that a fault has occurred, and the fault type is a single-phase fault;

[0064] When the instantaneous values of the switching currents of three phases are greater than or equal to a preset instantaneous current threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, it is determined that a fault has occurred, and the fault type is a three-phase fault;

[0065] Determine the branch current of each branch according to the switching current, and compare it with the first short-circuit current of each branch when different types of faults occur at different positions according to the DC circuit and a preset value, so as to determine the fault position.

[0066] Preferably, the method further includes:

[0067] Establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the first short-circuit current of each branch when different types of faults occur at different positions.

[0068] The schematic diagram of the existing typical 500 kV system wiring is as Figure 2 shown. In the area of the power system with a relatively high short-circuit current, the short-circuit current is generally formed by the convergence of the fault currents of multiple branches. As Figure 2 shown. When a fault occurs, the fault current of the circuit breaker directly connected to the fault point is the sum of the branch fault currents. At this time, the fault current is relatively large and may exceed the breaking capacity of the circuit breaker. Therefore, in the embodiments of the present invention, by quickly detecting the fault, determining the fault position and type, and quickly opening the target opening branch, the short-circuit current is limited, the short-circuit current breaking level of the system circuit breaker is reduced, and the safety of the system and equipment is ensured.

[0069] In the embodiments of the present invention, first, a quick detection of the fault and a judgment of the position and type are performed. Specifically, the switching current of each switch in the substation and the bus voltage of the substation are detected. When the instantaneous value of the switching current is greater than or equal to a preset instantaneous current threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, it is determined that a fault has occurred in the system. If the phases where the faults occur are all in the same phase, it is determined that a fault has occurred, and the fault type is a single-phase fault. If the phases where the faults occur include three phases, it is determined that a fault has occurred, and the fault type is a three-phase fault. When determining the fault position, it is judged according to the collected switching current. Specifically, the branch current of each branch is determined according to the switching current, and it is compared with the first short-circuit current of each branch when different types of faults occur at different positions according to the DC circuit, so as to determine the fault position.

[0070] Among them, in the embodiments of the present invention, according to the system operation data, a detailed simulation model considering the substation wiring topology is established, and simulation calculations are performed using the detailed simulation model, so as to calculate the first short-circuit current of each branch when different types of faults occur at different positions.

[0071] In step 102, compare the fault type and fault position with the target fault type and target fault position where the short-circuit current exceeds the standard when the switch is opened, and determine whether there is a situation where the short-circuit current exceeds the standard when the switch is opened.

[0072] Preferably, the method further includes:

[0073] Establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short-circuit current when each switch is opened when different types of faults occur at different positions;

[0074] Select the fault type and fault position corresponding to the second short-circuit current greater than or equal to the preset second short-circuit current threshold as the target fault type and target fault position where the short-circuit current exceeds the standard when the switch is opened.

[0075] In the embodiments of the present invention, it is also necessary to perform simulation calculations according to the above-mentioned detailed simulation model to determine the second short-circuit current actually opened by the switch when different types of faults occur at different fault positions, and determine the fault positions and fault types where the short-circuit current level exceeds the standard according to the second short-circuit current, as the target fault positions and target fault types, for use when the control device determines whether there is a situation where the short-circuit current exceeds the standard when the switch is opened.

[0076] In the embodiments of the present invention, compare the fault position and type obtained in step 101 with the target fault position and target fault type. When the obtained fault position and fault type are the target fault position and target fault type where the opening current of the switch exceeds the standard, it is determined that there is a situation where the short-circuit current exceeds the standard when the switch is opened.

[0077] In step 103, when it is determined that there is a situation where the short-circuit current exceeds the standard when the switch is opened, match according to the fault type, fault position, and the corresponding opened branch when different types of faults occur at different positions, and determine the target opened branch.

[0078] Preferably, the method further includes:

[0079] Sort the first short-circuit current of each branch when any type of fault occurs at any position in descending order to determine the branch sequence, and initialize i = 1;

[0080] Select the i-th branch in the branch sequence as the current key branch;

[0081] Disconnect the current critical branch, and obtain the third short-circuit current and the system stability level when the switch opens during different types of faults occurring at different positions;

[0082] When the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, determine the current critical branch as the target opening branch; otherwise, update i = i + 1, and re-determine the current critical branch until the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, and determine the current critical branch as the opening branch corresponding to any type of fault occurring at any position.

[0083] In step 104, before the conventional circuit breaker completes the opening operation, disconnect the target opening branch to limit the short-circuit current of the power system.

[0084] In an embodiment of the present invention, when it is determined that there is an over-standard short-circuit current for the switch opening, match according to the fault type, fault location obtained in step 101 and the preset opening branches corresponding to different types of faults occurring at different positions to determine the target opening branch. Among them, a fast switch is used as the branch opening device, and redundant configuration is achieved through the series connection of double switches to avoid the serious consequences caused by the switch malfunction. When a fault is detected and the fault type and fault location belong to the condition where the opening current of the circuit breaker exceeds the standard, command the fast switch to act and open the fault branch, thereby limiting the fault current.

[0085] Among them, the following method is used to determine the opening branch when any type of fault occurs at any position, including:

[0086] a) According to the system operation data, establish a detailed simulation model considering the substation wiring topology, and calculate the first short-circuit current level provided by each branch when a substation fault occurs; sort the first short-circuit currents in descending order to determine the branch sequence, and select the first branch in the branch sequence as the critical branch, that is, select the branch providing the largest short-circuit current as the critical branch.

[0087] b) Calculate the third short-circuit current actually opened by the switch when different types of faults occur at different fault positions in the substation after disconnecting the critical branch. If the third short-circuit current meets the requirements (that is, less than the preset third short-circuit current threshold), then further calculate the system stability level under the fault condition. If the system stability meets the requirements, select this branch as the branch to be opened during the fault.

[0088] c) If the system stability does not meet the requirements at this time, then select the next branch in the branch sequence and repeat the above steps.

[0089] Preferably, the method further includes:

[0090] After the fault is cleared, the reclosing condition is judged, and when the bus voltage returns to normal, the conduction of the target opened branch is restored.

[0091] Preferably, the method further includes:

[0092] If the fault type is a single-phase fault and the fault location is on a transmission line, the reclosing condition is judged after the opening time of the target opened branch reaches the first preset time threshold; otherwise, the reclosing condition is judged after the opening time of the target opened branch reaches the second preset time threshold.

[0093] In an embodiment of the present invention, after a fault occurs, the branch is opened. After the fault is cleared, it is necessary to quickly restore the opened branch, thereby reducing the impact on the system. To achieve rapid restoration after a fault, after the branch is opened, the substation bus voltage is detected in real time. When the bus voltage returns to normal and the voltage difference and phase angle difference with the branch voltage are within the allowable range, the conduction of the target opened branch is restored.

[0094] Among them, different restoration strategies are set according to the fault location and type. If it is a single-phase fault and the fault location is on a transmission line, the reclosing condition is judged 1 s after the branch is opened. If the conditions are met, the opened branch is reclosed; in other cases (for example, the fault location is a transformer), the condition is judged 0.2 s after the branch is opened. If the conditions are met, the opened branch is reclosed to reduce the branch opening time and probability.

[0095] Figure 3 It is a control schematic diagram of the device for limiting short-circuit current according to an embodiment of the present invention. As Figure 3 shown, the device specifically includes the following parts:

[0096] Control device: includes a measurement module and a control module. The measurement module collects the bus voltage of the substation, the electrical quantities of the current of the switch, and the state of the switch equipment in real time. The control module is used for the action of the opening device.

[0097] Fast opening device: installed on the key branches of the substation according to the selection method. The opening device includes two fast switches connected in series to ensure reliable current limiting even when a single switch fails.

[0098] The specific control strategy is as follows:

[0099] 1) In the normal operation state of the system, the opening device is in the normal closed operation state.

[0100] 2) The control device monitors the current and current of the substation in real time, quickly judges the fault. When it is judged that a fault occurs and the fault location and type will cause the breaker opening current to exceed the standard, a command is sent to the opening device to disconnect.

[0101] 3) The system's relay protection operates normally, and the conventional circuit breaker opens to cut off the fault.

[0102] 4) After the fault is cut off, the control device determines whether the reclosing condition is met. If the condition is met, the opened branch is reclosed.

[0103] Using a typical system structure, the effectiveness of the above device in interrupting large short-circuit currents was simulated. The wiring principle of the typical system is as Figure 4 shown. A fast-opening device is installed on the outgoing line 1 branch. When a fault occurs in this system, the short-circuit current reaches a maximum of 64 kA, exceeding the interrupting capacity of the existing circuit breaker, which is 63 kA. At this time, conventional limiting measures include shutting down some lines, which has a greater impact on the normal operation of the system.

[0104] Using the method of the present invention, by calculating the short-circuit current levels of different branches when a substation fault occurs and performing system stability analysis calculations, the opening device is installed on the line 1 branch. When the system is operating normally, the opening device is in the closed state, and at this time, the normal operation mode of the system is not affected. When a fault occurs in the substation, after the control device detects the fault, it first commands the opening device to open quickly, and the short-circuit current is limited. The limited short-circuit current level is 58 kA, which is lower than the circuit breaker's short-circuit current interrupting level of 63 kA.

[0105] The method of the present invention can, after a short-circuit fault occurs in the system, quickly detect the fault and determine the fault location, quickly open the key branch connected to the fault point that provides the short-circuit current, thereby limiting the short-circuit current, reducing the short-circuit current interrupting level of the system circuit breaker, and ensuring the safety of the system and equipment.

[0106] Figure 5 FIG. 500 is a schematic structural diagram of a system for limiting short-circuit current in a power system according to an embodiment of the present invention. As Figure 5 shown, the system 500 for limiting short-circuit current in a power system provided by the embodiment of the present invention includes: a fault determination unit 501, a short-circuit current exceeding standard determination unit 502, a target opening branch determination unit 503, and an action unit 504.

[0107] Preferably, the fault determination unit 501 is configured to obtain the switch current and bus voltage of each switch in the substation, determine whether a ground fault occurs in the power system according to the switch current and bus voltage, and determine the fault type and fault location when a fault occurs.

[0108] Preferably, the fault determination unit 501 determines whether a ground fault occurs in the power system according to the switch current and bus voltage, and determines the fault type and fault location when a fault occurs, including:

[0109] When the instantaneous value of the switching current in a single phase is greater than or equal to a preset instantaneous current threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, it is determined that a fault has occurred, and the fault type is a single-phase fault;

[0110] When the instantaneous values of the switching currents in three phases are greater than or equal to a preset instantaneous current threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, it is determined that a fault has occurred, and the fault type is a three-phase fault;

[0111] Determine the branch current of each branch according to the switching current, and compare it with the first short-circuit current of each branch when different types of faults occur at different positions in the DC circuit and a preset one to determine the fault position.

[0112] Preferably, the short-circuit current over-limit judgment unit 502 is configured to compare the fault type and fault position with the target fault type and target fault position where the short-circuit current exceeds the limit when the switch is opened preset, to determine whether there is a situation where the short-circuit current exceeds the limit when the switch is opened.

[0113] Preferably, the system further includes:

[0114] A second short-circuit current determination unit, configured to establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short-circuit current when each switch is opened when different types of faults occur at different positions;

[0115] A target fault type and position determination unit, configured to select the fault type and fault position corresponding to the second short-circuit current greater than or equal to a preset second short-circuit current threshold as the target fault type and target fault position where the short-circuit current exceeds the limit when the switch is opened.

[0116] Preferably, the target opening branch determination unit 503 is configured to, when it is determined that there is a situation where the short-circuit current exceeds the limit when the switch is opened, match according to the fault type, fault position and the corresponding opening branch when different types of faults occur at different positions preset, to determine the target opening branch.

[0117] Preferably, the system further includes: an opening branch determination unit, configured to:

[0118] Sort the first short-circuit currents of each branch when any type of fault occurs at any position in descending order to determine a branch sequence, and initialize i = 1;

[0119] Select the i-th branch in the branch sequence as the current key branch;

[0120] Disconnect the current critical branch, and obtain the third short-circuit current and the system stability level when the switch opens during different types of faults occurring at different positions;

[0121] When the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, determine the current critical branch as the target opening branch; otherwise, update i = i + 1, and re-determine the current critical branch until the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, and determine the current critical branch as the opening branch corresponding to any type of fault occurring at any position.

[0122] Preferably, the system further includes:

[0123] A first short-circuit current determination unit, configured to establish a simulation model based on the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the first short-circuit current of each branch when different types of faults occur at different positions.

[0124] Preferably, the action unit 504 is configured to disconnect the target opening branch before the conventional circuit breaker completes opening to limit the short-circuit current of the power system.

[0125] Preferably, the system further includes:

[0126] A recovery unit, configured to judge the reclosing condition after the fault is removed, and when the bus voltage returns to normal, restore the conduction of the target opening branch.

[0127] Preferably, the recovery unit further includes:

[0128] If the fault type is a single-phase fault and the fault location is a transmission line, judge the reclosing condition after the opening time of the target opening branch reaches the first preset time threshold; otherwise, judge the reclosing condition after the opening time of the target opening branch reaches the second preset time threshold.

[0129] The system 500 for limiting the short-circuit current of the power system in the embodiment of the present invention corresponds to the method 100 for limiting the short-circuit current of the power system in another embodiment of the present invention, and will not be elaborated here.

[0130] The present invention has been described by referring to a few embodiments. However, as is well known to those skilled in the art, as defined by the appended patent claims, other embodiments equivalent to those disclosed above of the present invention equally fall within the scope of the present invention.

[0131] Generally, all terms used in the claims are construed according to their ordinary meaning in the technical field, unless otherwise expressly defined therein. All references to "a / the [device, component, etc.]" are to be construed openly as at least one instance of the device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless expressly stated.

[0132] Those skilled in the art will appreciate that the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0133] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0134] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including instruction means that implement the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for limiting short - circuit current in a power system, characterized in that, the method includes: Obtain the switch current and bus voltage of each switch in the substation, judge whether a ground fault occurs in the power system according to the switch current and bus voltage, and determine the fault type and fault location when a fault occurs; Compare the fault type and fault location with the target fault type and target fault location where the short - circuit current exceeds the standard when the switch is opened as preset, and determine whether there is a situation where the short - circuit current exceeds the standard when the switch is opened; When it is determined that there is a situation where the short - circuit current exceeds the standard when the switch is opened, match according to the fault type, fault location and the corresponding opened branch when different types of faults occur at different positions as preset, and determine the target opened branch; Before the conventional circuit breaker completes opening, disconnect the target opened branch to limit the short - circuit current in the power system; wherein, judging whether a ground fault occurs in the power system according to the switch current and bus voltage, and determining the fault type and fault location when a fault occurs, includes: When the instantaneous value of the single - phase switch current is greater than or equal to the preset current instantaneous threshold value, or the current rising rate exceeds the preset rising rate threshold value, or the bus voltage is less than or equal to the preset bus voltage threshold value, it is determined that a fault occurs, and the fault type is a single - phase fault; When the instantaneous values of the three - phase switch currents are greater than or equal to the preset current instantaneous threshold value, or the current rising rate exceeds the preset rising rate threshold value, or the bus voltage is less than or equal to the preset bus voltage threshold value, it is determined that a fault occurs, and the fault type is a three - phase fault; Determine the branch current of each branch according to the switch current, and compare the branch current with the first short - circuit current of each branch when different types of faults occur at different positions as preset, and determine the fault location; wherein, the method further includes: Sort the first short - circuit currents of each branch when any type of fault occurs at any position in descending order to determine the branch sequence, and initialize i = 1; Select the i - th branch in the branch sequence as the current key branch; Disconnect the current key branch, and obtain the third short - circuit current and system stability level when the switch is opened when different types of faults occur at different positions; When the third short - circuit current is less than the third short - circuit current threshold value and the system stability is stable, determine the current key branch as the target opened branch; otherwise, update i = i + 1, and re - determine the current key branch until the third short - circuit current is less than the third short - circuit current threshold value and the system stability is stable, and determine the current key branch as the opened branch corresponding to when any type of fault occurs at any position.

2. The method according to claim 1, characterized in that, the method further includes: Establish a simulation model according to the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short - circuit current when each switch is opened when different types of faults occur at different positions; Select the fault type and fault location corresponding to the second short - circuit current greater than or equal to the preset second short - circuit current threshold value as the target fault type and target fault location where the short - circuit current exceeds the standard when the switch is opened.

3. The method according to claim 1, characterized in that, The method further includes: establishing a simulation model based on the operation data of the power system, and performing simulation calculations based on the simulation model to obtain the first short-circuit current of each branch when different types of faults occur at different positions.

4. The method according to claim 1, wherein, the method further includes: after the fault is removed, judging the reclosing condition, and when the bus voltage returns to normal, restoring the conduction of the target opened branch.

5. The method according to claim 4, wherein, the method further includes: if the fault type is a single-phase fault and the fault location is a transmission line, judging the reclosing condition after the opening time of the target opened branch reaches a first preset time threshold; otherwise, judging the reclosing condition after the opening time of the target opened branch reaches a second preset time threshold.

6. A system for limiting short-circuit current in a power system, wherein, the system includes: a fault determination unit, configured to obtain the switch current and bus voltage of each switch in the substation, judge whether a grounding fault occurs in the power system according to the switch current and bus voltage, and determine the fault type and fault location when a fault occurs; a short-circuit current over-limit judgment unit, configured to compare the fault type and fault location with the target fault type and target fault location where the short-circuit current exceeds the limit when the switch is opened preset, and determine whether there is a situation where the short-circuit current exceeds the limit when the switch is opened; a target opened branch determination unit, configured to, when it is determined that there is a situation where the short-circuit current exceeds the limit when the switch is opened, match according to the fault type, fault location, and the opened branch corresponding to different types of faults occurring at different positions preset, and determine the target opened branch; an action unit, configured to disconnect the target opened branch before the normal circuit breaker completes opening to limit the short-circuit current in the power system; wherein, the fault determination unit is configured to: when there is an instantaneous value of the single-phase switch current greater than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determine that a fault occurs, and the fault type is a single-phase fault; when there is an instantaneous value of the three-phase switch current greater than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determine that a fault occurs, and the fault type is a three-phase fault; determine the branch current of each branch according to the switch current, and compare the branch current with the first short-circuit current of each branch corresponding to different types of faults occurring at different positions preset to determine the fault location; wherein, the target opened branch determination unit is configured to: sort the first short-circuit current of each branch when any type of fault occurs at any position in descending order to determine a branch sequence, and initialize i = 1; select the i-th branch in the branch sequence as the current key branch; disconnect the current key branch, and obtain the third short-circuit current and system stability level when the switch is opened when different types of faults occur at different positions. When the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, determine the current critical branch as the target opening branch; otherwise, update i = i + 1, and re-determine the current critical branch until the third short-circuit current is less than the third short-circuit current threshold and the system stability is stable, and determine the current critical branch as the opening branch corresponding to any type of fault occurring at any position.

7. The system according to claim 6, wherein, the system further includes: a second short-circuit current determination unit, configured to establish a simulation model based on the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the second short-circuit current of each switch opening when different types of faults occur at different positions; a target fault type and position determination unit, configured to select the fault type and fault position corresponding to the second short-circuit current greater than or equal to the preset second short-circuit current threshold as the target fault type and target fault position where the switch opening short-circuit current exceeds the standard.

8. The system according to claim 6, wherein, the system further includes: a first short-circuit current determination unit, configured to establish a simulation model based on the operation data of the power system, and perform simulation calculations based on the simulation model to obtain the first short-circuit current of each branch when different types of faults occur at different positions.

9. The system according to claim 6, wherein, the system further includes: a restoration unit, configured to determine the reclosing condition when the fault is removed, and restore the conduction of the target opening branch when the bus voltage returns to normal.

10. The system according to claim 9, wherein, the restoration unit further includes: if the fault type is a single-phase fault and the fault position is a transmission line, then determine the reclosing condition after the opening time of the target opening branch reaches the first preset time threshold; otherwise, determine the reclosing condition after the opening time of the target opening branch reaches the second preset time threshold.

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