A method, apparatus, and storage medium for monitoring short-circuit current in a power system.
By obtaining the voltage change ratio in the power system and calculating the short-circuit current using a sub-power system model, the problem of accurately locating the short-circuit current in existing technologies is solved, enabling rapid and efficient short-circuit current monitoring and alarm.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HANGZHOU GUODIAN ELECTRIC POWER TECH DEV CO LTD
- Filing Date
- 2023-04-28
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, the calculation of power system short-circuit current by monitoring changes in bus voltage and power cannot accurately characterize the short-circuit location, resulting in the inability to precisely pinpoint the actual location where the short-circuit current occurs.
By acquiring the voltage values of all monitoring points in the power system, calculating the voltage change ratio, identifying the monitoring point with the largest voltage change as the short-circuit location, and using a sub-power system model to calculate the short-circuit current, the monitoring efficiency is improved.
It enables rapid and efficient monitoring of short-circuit current in power systems, accurately locates short-circuit positions and generates alarm signals, reducing equipment damage and the impact on power quality.
Smart Images
Figure CN116679108B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power system analysis technology, and in particular to a method, apparatus and storage medium for monitoring short-circuit current in a power system. Background Technology
[0002] Short-circuit faults disrupt the normal operation of power systems. The main hazards include: currents in branches near the fault point will be many times higher than normal; considering the electrodynamic effect of the current, significant mechanical stress will be generated between conductors, increasing the risk of the fault escalating into an accident; prolonged short circuits may damage equipment due to heat; and a significant drop in system voltage during a short circuit can severely impact users with high power quality requirements, potentially even causing load tripping due to low voltage. Because power systems can take timely action to protect equipment and circuits when abnormal short-circuit currents are detected, monitoring short-circuit currents in power systems is necessary to mitigate the hazards caused by these faults.
[0003] Currently, existing technologies determine the voltage and power changes of the monitored bus at the nth sampling time point by measuring the voltage vector and downstream combined power at the n+1th sampling time point, and then calculate the short-circuit current of the bus at the nth sampling time point based on these voltage and power changes. This method only requires collecting the voltage vector and downstream combined power from the local information of the monitored bus to determine the short-circuit current, without needing to perform short-circuit current calculations based on global information such as power flow and system parameters.
[0004] However, busbars in a power system are only located between different voltage distribution devices in a substation, and between electrical equipment such as transformers and their corresponding distribution devices. For long-distance power transmission, transmission lines are used. Both busbars and transmission lines in a power system are susceptible to short circuits. Therefore, when a short circuit occurs in a power system, calculating the short-circuit current of the busbar alone cannot accurately represent the actual short-circuit current generated at the location of the short circuit. Summary of the Invention
[0005] To improve the efficiency of monitoring short-circuit current in power systems, embodiments of this application provide a method, apparatus, and storage medium for monitoring short-circuit current in power systems.
[0006] In a first aspect, this embodiment provides a method for monitoring short-circuit current in a power system, the method comprising:
[0007] Obtain the voltage values at all monitoring points in the power system, where each monitoring point has a unique monitoring number.
[0008] Each time a voltage value is acquired, the voltage change ratio at each monitoring point at the current moment is obtained based on the two most recent acquired voltage values. It is then determined whether at least one voltage change ratio exceeds the preset change ratio. If so, the monitoring number corresponding to the monitoring point whose voltage change ratio exceeds the preset change ratio is changed.
[0009] Obtain the reference monitoring number corresponding to the largest voltage change ratio from all changed monitoring numbers, and obtain the associated monitoring number related to the reference monitoring number based on the reference monitoring number;
[0010] A sub-power system model is formed by obtaining the reference monitoring number and the associated monitoring number from the preset power system model, and the short-circuit current generated by the short circuit is obtained using the sub-power system model.
[0011] In some embodiments, obtaining the associated monitoring number related to the reference monitoring number based on the reference monitoring number includes:
[0012] Obtain the reference monitoring point corresponding to the reference monitoring number, obtain the associated monitoring point at the next higher level and / or the next lower level of the reference monitoring point according to the preset power system model, and determine the monitoring number corresponding to the associated monitoring point as the associated monitoring number related to the reference monitoring number.
[0013] In some embodiments, using the sub-power system model to obtain the short-circuit current resulting from a short circuit includes:
[0014] Based on the connection relationships and impedance information in the sub-power system model, the sub-power flow calculation formula for solving the current is obtained for the sub-power system model.
[0015] Obtain the known parameters required for the sub-power flow calculation formula, and substitute the known parameters into the sub-power flow calculation formula to obtain the current value of each branch in the sub-power model;
[0016] Based on the current value, obtain the current difference between any two current values, determine whether the values of all current differences do not exceed the preset current difference, and if they do not exceed the preset current difference, add all current values together to obtain the short circuit current generated by the short circuit.
[0017] If at least one exceeds the preset current difference, the larger of the two current values is determined as the short-circuit current caused by the short circuit.
[0018] In some embodiments, using the sub-power system model to obtain the short-circuit current generated by a short circuit further includes:
[0019] Based on the connection relationships in the sub-power system model, obtain the hierarchical relationship between each associated monitoring number and the reference monitoring number in the sub-power system model;
[0020] The associated voltage and associated power values at each associated monitoring number in the sub-power system model, as well as the reference voltage and reference power values at each reference monitoring number, are obtained sequentially from the upper level to the lower level based on the hierarchical relationship. The power difference between each associated power value and the reference power value, and the voltage difference between each associated voltage value and the reference voltage value are obtained sequentially from the upper level to the lower level. Each power difference corresponds to a uniquely determined voltage difference.
[0021] The current value is obtained based on each voltage difference and the corresponding power difference. The current difference between any two current values is obtained based on the current value. It is determined whether the values of all current differences do not exceed the preset current difference. If they do not exceed the preset current difference, all current values are added together to obtain the short-circuit current generated by the short circuit.
[0022] If at least one exceeds the preset current difference, the larger of the two current values is determined as the short-circuit current generated by the short circuit.
[0023] In some embodiments, obtaining the associated monitoring points at the level above and / or below the reference monitoring point according to a preset power system model includes:
[0024] Determine whether the value of the reference monitoring number is the smallest among all monitoring numbers. If it is the smallest, obtain the associated monitoring point located at the next level below the reference monitoring point according to the connection relationship in the preset power system model.
[0025] If it is not the smallest, determine whether the value of the reference monitoring number is the largest among all monitoring numbers. If it is the largest, obtain the associated monitoring point located one level above the reference monitoring point according to the connection relationship in the preset power system model.
[0026] If it is neither the maximum nor the minimum, the associated monitoring point at the next level above the reference monitoring point and the associated monitoring point at the next level are obtained according to the connection relationship in the preset power system model.
[0027] In some embodiments, the method further includes:
[0028] If none of the voltage change ratios exceed the preset change ratio, continue waiting to acquire the voltage values at each monitoring point in the power system.
[0029] In some embodiments, after obtaining the short-circuit current generated by a short circuit using the sub-power system model, an alarm signal corresponding one-to-one with the reference monitoring number is generated.
[0030] Secondly, this embodiment provides a device for monitoring short-circuit current in a power system, the device comprising: a voltage acquisition module, a processing module, a correlation acquisition module, and a monitoring module; wherein,
[0031] The voltage acquisition module is used to acquire the voltage values at all monitoring points in the power system, wherein each monitoring point has a unique monitoring number.
[0032] The processing module is used to obtain the voltage change value at each monitoring point at the current moment based on the two most recent voltage values obtained each time a voltage value is acquired, and to determine whether at least one voltage change value exceeds a preset change value. If so, the module obtains the change monitoring number corresponding to the monitoring point whose voltage change value exceeds the preset change value.
[0033] The association acquisition module is used to obtain the reference monitoring number corresponding to the largest voltage change value from all changed monitoring numbers, and to obtain the associated monitoring number related to the reference monitoring number based on the reference monitoring number.
[0034] The monitoring module is used to obtain a sub-power system model formed by the reference monitoring number and the associated monitoring number from the preset power system model, and to use the sub-power system model to obtain the short-circuit current generated when a short circuit occurs.
[0035] In some embodiments, the device further includes an alarm module; wherein,
[0036] The alarm module is used to obtain the short-circuit current generated by the short circuit using the sub-power system model, and then generate an alarm signal that corresponds one-to-one with the reference monitoring number.
[0037] Thirdly, this embodiment provides a computer-readable storage medium having a computer program stored thereon that can run on a processor, wherein when the computer program is executed by the processor, it implements a method for monitoring short-circuit current in a power system as described in the first aspect.
[0038] By employing the above method, this application first obtains the voltage values at all monitoring points in the power system, and then calculates the voltage change ratio at each monitoring point based on the two most recent voltage values. Next, it compares this voltage change ratio with a preset change ratio. If at least one voltage change ratio exceeds the preset ratio, it indicates a short circuit in the power system. In this case, it continues to obtain the change monitoring number corresponding to the monitoring point whose voltage change ratio exceeds the preset ratio. It then obtains the reference monitoring number corresponding to the largest voltage change ratio from all the change monitoring numbers. The location corresponding to this reference monitoring number is near the location of the short circuit in the power system. Therefore, it obtains an associated monitoring number based on the reference monitoring number. A sub-power system model formed by the reference monitoring number and the associated monitoring number is obtained from a preset power system model. The short-circuit current generated by the short circuit is obtained using this sub-power system model. Compared to the preset power system model, the sub-power system model is simpler. Using a simpler sub-power system model to monitor the short-circuit current generated by the short circuit facilitates faster and more efficient monitoring of the power system's short-circuit current. Attached Figure Description
[0039] Figure 1 This is a block diagram of a method for monitoring short-circuit current in a power system, provided in an embodiment of this application.
[0040] Figure 2 This is a schematic diagram showing the monitoring numbers corresponding to all monitoring points in the power system provided in this application embodiment.
[0041] Figure 3 This is a block diagram provided in this application embodiment for obtaining associated monitoring points located one level above and / or one level below the reference monitoring point based on a preset power system model.
[0042] Figure 4 This application provides a block diagram for obtaining the short-circuit current generated by a short circuit using a sub-power system model.
[0043] Figure 5 This application provides another block diagram for obtaining the short-circuit current generated by a short circuit using a sub-power system model.
[0044] Figure 6 This is a schematic diagram of a device for monitoring short-circuit current in a power system, provided in an embodiment of this application. Detailed Implementation
[0045] To better understand the purpose, technical solutions, and advantages of this application, it has been described and illustrated below with reference to the accompanying drawings and embodiments. However, those skilled in the art should understand that this application can be implemented without these details. It will be apparent to those skilled in the art that various modifications can be made to the embodiments disclosed in this application, and the general principles defined in this application can be applied to other embodiments and application scenarios without departing from the principles and scope of this application. Therefore, this application is not limited to the illustrated embodiments, but is consistent with the broadest scope claimed in this application.
[0046] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.
[0047] An electric power system is a system for the production and consumption of electrical energy, consisting of power plants, transmission and transformation lines, power distribution stations, and electricity consumers. Its function is to convert primary energy from nature into electrical energy through power generation devices, and then supply the electrical energy to various users through transmission, transformation, and distribution.
[0048] A short circuit occurs when two points with different electrical potentials are improperly brought into direct contact or connected by a conductor with very low impedance (or resistance) in a normal circuit. The short-circuit current is the current flowing through a power system when an abnormal connection (i.e., a short circuit) occurs between phases or between a phase and ground (or the neutral line). Its value can be much greater than the rated current and depends on the electrical distance between the short-circuit point and the power source.
[0049] Figure 1 This is a block diagram of a method for monitoring short-circuit current in a power system, provided in an embodiment of this application. Figure 1 As shown, a method for monitoring short-circuit current in a power system includes the following steps:
[0050] Step S100: Obtain the voltage values at all monitoring points in the power system, where each monitoring point has a unique monitoring number.
[0051] The power system transmits electrical energy generated by power plants to users through various load-bearing carriers, including but not limited to transmission lines and busbars, sequentially through power plants, transmission lines, substations, and users. The power transmission path from the power plant to the user involves multiple splits and aggregations, each creating a corresponding node, which serves as a monitoring point within the power system.
[0052] Each node in the power system is numbered sequentially from power plant to power consumption, from smallest to largest, so that each monitoring point corresponds to a unique monitoring number; alternatively, each stage of the power system is numbered sequentially from power plant to power consumption, from largest to smallest, so that each monitoring point corresponds to a unique monitoring number. The requirement is that all monitoring points in the power system have distinct monitoring numbers, meaning each monitoring point has a unique monitoring number. This application preferably uses the sequential numbering method from power plant to power consumption, where each node is numbered in ascending order, so that each monitoring point corresponds to a unique monitoring number.
[0053] Figure 2 This is a schematic diagram showing the monitoring numbers corresponding to all monitoring points in the power system provided in this application embodiment. For example... Figure 2 As shown, in the power system, monitoring points are numbered sequentially from the power plant to the user's electricity consumption point, from smallest to largest. Specifically, when at least two nodes are obtained after a power split, the location of the person is used as a reference point, and the monitoring points are numbered sequentially from farthest to nearest to obtain the corresponding monitoring number for each node. When a node is obtained after a power split and then converged, the largest monitoring number obtained from the previous split is incremented by one to obtain the monitoring number corresponding to the converged node. When several nodes are obtained after a power split, the location of the person is still used as a reference point, and the largest monitoring number obtained from the previous split is used as a reference point, with the monitoring points numbered sequentially from farthest to nearest to obtain the corresponding monitoring number for each node.
[0054] The WAMS system or other measurement systems can be used to simultaneously measure the voltage value at each monitoring point in the power system, thereby obtaining the voltage values at all monitoring points in the power system. The time interval between two consecutive acquisitions of voltage values at all monitoring points in the power system can be determined directly based on the measurement frequency of the WAMS system or other measurement systems. This ensures timely acquisition of voltage values at all monitoring points in the power system, reducing the possibility of missed voltage values.
[0055] Alternatively, the time interval between two consecutive voltage acquisitions of all monitoring points in the power system can be determined based on the measurement frequency of the WAMS system or other measurement systems and the time required to complete one short-circuit current measurement. That is, the shortest allowable time interval for each voltage acquisition by the WAMS system or other monitoring systems is determined theoretically based on the measurement frequency. The maximum value between this shortest time interval and the time required to complete one short-circuit current measurement is then used as the time interval between two consecutive voltage acquisitions of all monitoring points in the power system. This ensures that when the shortest time interval is less than the time required to complete one short-circuit current measurement, the time required to complete one short-circuit current measurement is used to determine the time interval between two consecutive voltage acquisitions of all monitoring points in the power system. This allows the acquired voltage values to be used promptly to determine the short-circuit current generated by a short circuit, reducing the possibility of the acquired voltage values not being calculated in a timely manner due to the time interval for acquiring voltage values being less than the time interval for calculating the short-circuit current. In this application embodiment, it is preferable to directly determine the time interval between two consecutive voltage acquisitions of all monitoring points in the power system based on the measurement frequency of the WAMS system or other measurement systems.
[0056] Step S200: For each voltage value acquired, the voltage change ratio at each monitoring point at the current moment is obtained based on the two most recent acquired voltage values. It is determined whether at least one voltage change ratio exceeds the preset change ratio. If so, the monitoring number corresponding to the monitoring point whose voltage change ratio exceeds the preset change ratio is changed.
[0057] Each time the voltage values at all monitoring points in the power system are acquired, these values are stored, thus obtaining the voltage values at all monitoring points in the power system for each acquisition. Since each monitoring point corresponds to a unique monitoring number, and each voltage value corresponds to a unique monitoring point, each voltage value also corresponds to a unique monitoring number. Subtracting the second-to-last acquired voltage value from the most recent acquired voltage value for the same monitoring number yields the voltage change value at that monitoring point. Dividing this voltage change value by the second-to-last acquired voltage value gives the voltage change ratio at that monitoring point. This process is repeated for each other monitoring number, subtracting the second-to-last acquired voltage value from the most recent acquired voltage value to obtain the voltage change value at each monitoring point for that other monitoring number. Dividing each voltage change value by the second-to-last acquired voltage value gives the voltage change ratio at each monitoring point for that other monitoring number, thus obtaining the voltage change value at each monitoring point at the current moment.
[0058] When a power system is transmitting electricity normally, the voltage ratio at each node does not fluctuate significantly. The aforementioned preset change ratio represents the maximum normal change in the voltage ratio at all nodes when the power system is transmitting electricity normally. The value of the preset change ratio can be determined according to the actual situation. Subtracting the preset change ratio from each voltage change ratio sequentially yields a corresponding number of ratio differences. If all ratio differences are not greater than zero, then all voltage change ratios do not exceed the preset change ratio, indicating that no short circuit has occurred in the power system. Therefore, the voltage values at each monitoring point in the power system are then acquired and awaited.
[0059] If at least one proportional difference is greater than zero, then at least one voltage change ratio exceeds a preset change ratio, indicating a short circuit in the power system, requiring further monitoring of the short-circuit current. A first keyword is added to the monitoring numbers corresponding to voltage change ratios exceeding the preset change ratio, thus making the monitoring number with the first keyword a representation of the voltage change ratio exceeding the preset change ratio. Therefore, by checking whether each monitoring number has the first keyword, the monitoring number corresponding to the monitoring point whose voltage change ratio exceeds the preset change ratio can be obtained by changing the monitoring number.
[0060] Step S300: Obtain the reference monitoring number corresponding to the largest voltage change ratio from all changed monitoring numbers, and obtain the associated monitoring number related to the reference monitoring number based on the reference monitoring number.
[0061] Sort all voltage change percentages corresponding to changed monitoring numbers in ascending or descending order to obtain the largest voltage change percentage and the corresponding monitoring number. Add a second key to the monitoring number corresponding to the largest voltage change percentage, so that the monitoring number with the added second key represents the reference monitoring number corresponding to the largest voltage change percentage among all changed monitoring numbers. Since a short circuit causes a significant voltage drop, the location with the largest voltage change percentage is the location of the short circuit. Since a short circuit can occur anywhere in the power system, the monitoring point corresponding to the reference monitoring number is the monitoring point closest to the short circuit.
[0062] Considering that a short circuit in the power system may occur at a level above or below the monitoring point corresponding to the reference monitoring number, in order to monitor the short circuit current more accurately, in addition to the reference monitoring number, associated monitoring numbers are also considered. The short circuit current is monitored jointly by the monitoring points corresponding to the reference monitoring number and the monitoring points corresponding to the associated monitoring numbers.
[0063] The process of obtaining the associated monitoring number based on the reference monitoring number includes: obtaining the reference monitoring point corresponding to the reference monitoring number, obtaining the associated monitoring point at the next higher level and / or the next lower level of the reference monitoring point based on the preset power system model, and determining the monitoring number corresponding to the associated monitoring point as the associated monitoring number related to the reference monitoring number.
[0064] Figure 3 This is a block diagram provided in this application embodiment for obtaining associated monitoring points at the level above and / or below the reference monitoring point based on a preset power system model. For example... Figure 3 As shown, obtaining the associated monitoring points at the level above and / or below the reference monitoring point based on the preset power system model includes the following steps:
[0065] Step S201: Determine whether the value of the reference monitoring number is the smallest among all monitoring numbers. If it is the smallest, obtain the associated monitoring point located at the next level below the reference monitoring point according to the connection relationship in the preset power system model.
[0066] Step S202: If it is not the smallest, determine whether the value of the reference monitoring number is the largest among all monitoring numbers. If it is the largest, obtain the associated monitoring point located one level above the reference monitoring point according to the connection relationship in the preset power system model.
[0067] Step S203: If it is neither the maximum nor the minimum, obtain the associated monitoring point at the level above the reference monitoring point and the associated monitoring point at the level below the reference monitoring point according to the connection relationship in the preset power system model.
[0068] The aforementioned preset power system model refers to the power system model corresponding to the entire power system. Once the power system is built, this preset power system model is already determined. This preset power system model has corresponding input terminals, output terminals, and internal connections. The power plant segment is the input terminal, the user power consumption segment is the output terminal, and the internal connections between the power plant segment and the user power consumption segment are the relationships between them. The order from input terminal to output terminal is from upper level to lower level. If the reference monitoring number has the smallest value among all monitoring numbers, it indicates that the reference monitoring point corresponding to this reference monitoring number is the power plant monitoring point, which is the input terminal of the preset power system model. In this case, there are no associated monitoring points at the upper level of the reference monitoring point, only associated monitoring points at the lower level of the reference monitoring point. Similarly, if the reference monitoring number has the largest value among all monitoring numbers, it indicates that the reference monitoring point corresponding to this reference monitoring number is the user power consumption monitoring point, which is the output terminal of the preset power system model. In this case, there are no associated monitoring points at the lower level of the reference monitoring point, only associated monitoring points at the upper level of the reference monitoring point. If the reference monitoring number is neither the largest nor the smallest among all monitoring numbers, then there are both associated monitoring points at the level above the reference monitoring point and associated monitoring points at the level below the reference monitoring point.
[0069] The above connection relationships indicate which monitoring numbers above and below each monitoring number are in a direct hierarchical relationship. After determining the positional relationship between the associated monitoring point and the reference monitoring point, the connection relationships are used to determine the next-level associated monitoring number that is in a direct hierarchical relationship with the reference monitoring number, and the next-level associated monitoring number that is in a direct hierarchical relationship with the reference monitoring number. Then, the associated monitoring point corresponding to the next-level associated monitoring number is the next-level associated monitoring point, and the associated monitoring point corresponding to the next-level associated monitoring number is the next-level associated monitoring point. Specifically, if the reference monitoring number has the smallest value among all monitoring numbers, there is no next-level associated monitoring number in a direct hierarchical relationship with the reference monitoring number; if the reference monitoring number has the largest value among all monitoring numbers, there is no next-level associated monitoring number in a direct hierarchical relationship with the reference monitoring number.
[0070] Step S400: Obtain a sub-power system model formed by the reference monitoring number and the associated monitoring number from the preset power system model, and use the sub-power system model to obtain the short-circuit current generated by the short circuit.
[0071] The preset power system model is specifically an equivalent circuit model obtained by equating the equipment or conductors in the power system to their corresponding impedances. Each monitoring point in the preset power system model is marked with a corresponding monitoring number. All conductors connected to both the reference monitoring point corresponding to a reference monitoring number and the associated monitoring point corresponding to an associated monitoring number form a sub-power system model, thus obtaining the sub-power system model formed by the reference monitoring number and the associated monitoring number. This sub-power system model is only a part of the preset power system model, and the connection relationships between the monitoring points in this sub-power system model remain the same as those in the preset power sub-power system model. In other words, a sub-power system model containing the location of short circuits is obtained from the preset power system model. Compared to the preset power system model, the sub-power system model is simpler. Using this simpler sub-power system model to monitor the short-circuit current generated by a short circuit facilitates faster and more efficient monitoring of the power system's short-circuit current.
[0072] Figure 4 This application provides a block diagram for obtaining the short-circuit current generated by a short circuit using a sub-power system model. For example... Figure 4 As shown, obtaining the short-circuit current generated by a short circuit using a sub-power system model includes the following steps:
[0073] Step S401: Based on the connection relationships and impedance information in the sub-power system model, obtain the sub-power flow calculation formula for solving the current corresponding to the sub-power system model.
[0074] Step S402: Obtain the known parameters required for the sub-power flow calculation formula, and substitute the known parameters into the sub-power flow calculation formula to obtain the current value of each branch in the sub-power model.
[0075] Step S403: Obtain the current difference between any two current values based on the current values, determine whether the values of all current differences do not exceed the preset current difference, and if they do not exceed the preset current difference, add all current values together to obtain the short-circuit current generated by the short circuit.
[0076] Step S404: If at least one exceeds the preset current difference, the larger of the two current values is determined as the short-circuit current generated by the short circuit.
[0077] The sub-power system model already displays the impedance information and connection relationships within it. First, the topology of the sub-power system model is determined, including the connections between monitoring points, branches, and equipment. Then, for each monitoring point, Kirchhoff's Current Law and Voltage Law equations are derived based on the impedance information, forming the sub-power flow calculation formula for solving the current. Next, based on this formula, other known parameters besides the current parameters are determined. These known parameters are then monitored using a WAMS system or other monitoring systems, and all the acquired known parameters at the same time are substituted into the formula. Finally, the formula is transformed into matrix form, and methods such as Gaussian-Jordan elimination or LU decomposition are used to solve for the current value on each branch in the sub-power system model.
[0078] Since short circuits can occur on both the main circuit and branches in the sub-power system model, if a short circuit occurs on the main circuit, the current values on all branches in the sub-power system model will increase by the same degree, and the difference between the current values on each branch will not change much. Therefore, by subtracting the current values of all branches pairwise and taking the absolute value, the current difference between any two current values on a branch can be obtained. The preset current difference value mentioned above represents the maximum value of the normal current difference between different branches in the sub-power system model. The specific value of this preset current difference value can be determined according to the actual situation, and this application embodiment does not further limit the preset current difference value. If the values of all current differences do not exceed the preset current difference value, it indicates that a short circuit has occurred on the main circuit of the sub-power system model. Then, by adding the current values of all branches in the sub-power system model, the short-circuit current generated by the short circuit in the power system can be obtained.
[0079] Similarly, if at least one current difference exceeds a preset current difference, it indicates a short circuit has occurred on a branch in the sub-power system model. Since a short circuit causes a rapid increase in the current on that branch, the larger of the two current values corresponding to the two current differences exceeding the preset current difference is the short-circuit current generated by the short circuit in the power system. Compared to using the entire power system model to determine the power flow calculation formula, this application first determines the approximate location of the short circuit in the entire power system model, then decomposes it into a sub-power system model containing the location of the short circuit. Based on this sub-power system model, the sub-power flow calculation formula is determined, making the sub-power flow calculation formula simpler than the power flow calculation formula. After all, both the power flow calculation formula and the sub-power flow calculation formula are nonlinear and complex calculations. Using the simpler sub-power flow calculation formula allows for more efficient monitoring of the short-circuit current in the power system.
[0080] Figure 5 This application provides another block diagram for obtaining the short-circuit current generated by a short circuit using a sub-power system model. For example... Figure 5 As shown, another method for obtaining the short-circuit current generated by a short circuit using a sub-power system model includes the following steps:
[0081] Step S401': Based on the connection relationships in the sub-power system model, obtain the hierarchical relationship between each associated monitoring number and the reference monitoring number in the sub-power system model.
[0082] Step S402': Obtain the associated voltage and associated power values at each associated monitoring number in the sub-power system model, as well as the reference voltage and reference power values at each reference monitoring number. Based on the hierarchical relationship, obtain the power difference between each associated power value and the reference power value, and the voltage difference between each associated voltage value and the reference voltage value in sequence from the upper level to the lower level. Each power difference corresponds to a uniquely determined voltage difference.
[0083] Step S403': Obtain the current value based on each voltage difference and the corresponding power difference; obtain the current difference between any two current values based on the current values; determine whether the values of all current differences do not exceed the preset current difference; if they do not exceed the preset current difference, add all current values together to obtain the short-circuit current generated by the short circuit.
[0084] Step S404': If at least one exceeds the preset current difference, determine the larger of the two current values that exceed the preset current difference as the short-circuit current generated by the short circuit.
[0085] Since the connectivity in the sub-power system model already indicates which monitoring numbers are directly related to each monitoring number at its superior level and which are directly related to each monitoring number at its subordinate level, the hierarchical relationship between each associated monitoring number and the reference monitoring number in the sub-power system model can be obtained by examining which monitoring numbers are directly related to each other at their superior and subordinate levels.
[0086] After obtaining the hierarchical relationship between each associated monitoring number and the reference monitoring number in the sub-power system model, the associated voltage and power values at each associated monitoring number, as well as the reference voltage and power values at each reference monitoring number, are obtained using the WAMS system or other monitoring systems. The power difference between the associated power value and the reference power value is obtained by subtracting the reference power value at the lower level from the associated power value at the higher level, or vice versa. Similarly, the voltage difference between the associated voltage value and the reference voltage value is obtained by subtracting the reference voltage value at the lower level from the associated voltage value at the higher level, or vice versa. Each power difference corresponds to a uniquely determined voltage difference, and each voltage difference also corresponds to a uniquely determined power difference; that is, there is a one-to-one correspondence between power differences and voltage differences.
[0087] The short-circuit current value is determined using the formula: |Power Difference / (Voltage Difference + Voltage Difference × Conjugate of Voltage Difference)|. Then, the implementation methods of steps S403 and S404 above are used to implement steps S403' ("Obtain the current difference between any two current values based on the current values, determine whether all current differences do not exceed a preset current difference; if not, sum all current values to obtain the short-circuit current generated by the short circuit") and S404', which will not be elaborated further here. This eliminates the need for short-circuit current calculation based on global information such as power flow and system parameters. It only requires collecting the voltage and power of reference monitoring points and associated monitoring points in the sub-power system model to determine the short-circuit current, making short-circuit current monitoring in the power system simpler and faster.
[0088] In addition, after obtaining the short-circuit current generated by a short circuit using the sub-power system model, an alarm signal corresponding to a reference monitoring number is generated. This allows staff to promptly identify the location of the short circuit and quickly carry out repairs on that location, effectively preventing the damage caused by the short circuit to the power system.
[0089] Figure 6 This is a schematic diagram of a device for monitoring short-circuit current in a power system, provided in an embodiment of this application. Figure 6 As shown, a device for monitoring short-circuit current in a power system includes: a voltage acquisition module, a processing module, a correlation acquisition module, and a monitoring module.
[0090] The voltage acquisition module acquires voltage values at all monitoring points in the power system, with each monitoring point having a unique monitoring number. The processing module, after acquiring a voltage value, calculates the voltage change at each monitoring point based on the two most recent acquisitions, determines if at least one voltage change exceeds a preset value, and if so, acquires the changed monitoring number corresponding to the monitoring point with the voltage change exceeding the preset value. The association acquisition module obtains the reference monitoring number corresponding to the largest voltage change from all changed monitoring numbers, and then obtains associated monitoring numbers based on the reference monitoring number. The monitoring module acquires a sub-power system model formed by the reference monitoring number and associated monitoring numbers from a preset power system model, and uses the sub-power system model to obtain the short-circuit current generated by a short circuit.
[0091] In addition, an apparatus for monitoring short-circuit current in a power system further includes an alarm module, wherein the alarm module is used to generate an alarm signal corresponding one-to-one with the reference monitoring number after obtaining the short-circuit current generated by the short circuit using a sub-power system model.
[0092] The other functions performed by the voltage acquisition module, processing module, correlation acquisition module, monitoring module, and alarm module, as well as the technical details of each function, are the same as or similar to the corresponding features in the previously described method for monitoring short-circuit current in power systems, and therefore will not be repeated here.
[0093] This application also provides a computer storage medium storing a computer program that, when run on a computer, enables the computer to execute the steps in the previously described method for monitoring short-circuit current in a power system.
[0094] It should be understood that although the steps in the flowcharts in the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order requirement for the execution of these steps, and they can be performed in other orders.
[0095] The above description is only a partial embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A method for monitoring short-circuit current in a power system, characterized in that, The method includes: Obtain the voltage values at all monitoring points in the power system, where each monitoring point has a unique monitoring number. Each time a voltage value is acquired, the voltage change ratio at each monitoring point at the current moment is obtained based on the two most recent acquired voltage values. It is then determined whether at least one voltage change ratio exceeds the preset change ratio. If so, the monitoring number corresponding to the monitoring point whose voltage change ratio exceeds the preset change ratio is changed. Obtain the reference monitoring number corresponding to the largest voltage change ratio from all changed monitoring numbers, and obtain the associated monitoring number related to the reference monitoring number based on the reference monitoring number; A sub-power system model is formed by obtaining the reference monitoring number and the associated monitoring number from the preset power system model, and the short-circuit current generated by the short circuit is obtained using the sub-power system model.
2. The method according to claim 1, characterized in that, Obtaining associated monitoring numbers based on the reference monitoring number includes: Obtain the reference monitoring point corresponding to the reference monitoring number, obtain the associated monitoring point at the next higher level and / or the next lower level of the reference monitoring point according to the preset power system model, and determine the monitoring number corresponding to the associated monitoring point as the associated monitoring number related to the reference monitoring number.
3. The method according to claim 2, characterized in that, The short-circuit current generated by a short circuit is obtained using the aforementioned sub-power system model, including: Based on the connection relationships and impedance information in the sub-power system model, the sub-power flow calculation formula for solving the current is obtained for the sub-power system model. Obtain the known parameters required for the sub-power flow calculation formula, and substitute the known parameters into the sub-power flow calculation formula to obtain the current value on each branch in the sub-power system model; Based on the current value, obtain the current difference between any two current values, determine whether the values of all current differences do not exceed the preset current difference, and if they do not exceed the preset current difference, add all current values together to obtain the short circuit current generated by the short circuit. If at least one exceeds the preset current difference, the larger of the two current values is determined as the short-circuit current caused by the short circuit.
4. The method according to claim 2, characterized in that, Using the aforementioned sub-power system model to obtain the short-circuit current generated by a short circuit also includes: Based on the connection relationships in the sub-power system model, obtain the hierarchical relationship between each associated monitoring number and the reference monitoring number in the sub-power system model; The associated voltage and associated power values at each associated monitoring number in the sub-power system model, as well as the reference voltage and reference power values at each reference monitoring number, are obtained sequentially from the upper level to the lower level based on the hierarchical relationship. The power difference between each associated power value and the reference power value, and the voltage difference between each associated voltage value and the reference voltage value are obtained sequentially from the upper level to the lower level. Each power difference corresponds to a uniquely determined voltage difference. The current value is obtained based on each voltage difference and the corresponding power difference. The current difference between any two current values is obtained based on the current value. It is determined whether the values of all current differences do not exceed the preset current difference. If they do not exceed the preset current difference, all current values are added together to obtain the short-circuit current generated by the short circuit. If at least one exceeds the preset current difference, the larger of the two current values is determined as the short-circuit current generated by the short circuit.
5. The method according to claim 2, characterized in that, The step of obtaining the associated monitoring points located at the level above and / or below the reference monitoring point according to the preset power system model includes: Determine whether the value of the reference monitoring number is the smallest among all monitoring numbers. If it is the smallest, obtain the associated monitoring point located at the next level below the reference monitoring point according to the connection relationship in the preset power system model. If it is not the smallest, determine whether the value of the reference monitoring number is the largest among all monitoring numbers. If it is the largest, obtain the associated monitoring point located one level above the reference monitoring point according to the connection relationship in the preset power system model. If it is neither the largest nor the smallest, the associated monitoring points at the next level above the reference monitoring point and the associated monitoring points at the next level are obtained according to the connection relationship in the preset power system model. Each node is numbered from smallest to largest according to the order of the power system from the power plant to the power consumption link, so that each monitoring point corresponds to a unique monitoring number.
6. The method according to claim 1, characterized in that, The method further includes: If none of the voltage change ratios exceed the preset change ratio, continue waiting to acquire the voltage values at each monitoring point in the power system.
7. The method according to claim 1, characterized in that, After obtaining the short-circuit current generated by the short circuit using the sub-power system model, an alarm signal corresponding one-to-one with the reference monitoring number is generated.
8. A device for monitoring short-circuit current in a power system, characterized in that, The device includes: a voltage acquisition module, a processing module, a correlation acquisition module, and a monitoring module; wherein... The voltage acquisition module is used to acquire the voltage values at all monitoring points in the power system, wherein each monitoring point has a unique monitoring number. The processing module is used to obtain the voltage change value at each monitoring point at the current moment based on the two most recent voltage values obtained each time a voltage value is acquired, and to determine whether at least one voltage change value exceeds a preset change value. If so, the module obtains the change monitoring number corresponding to the monitoring point whose voltage change value exceeds the preset change value. The association acquisition module is used to obtain the reference monitoring number corresponding to the largest voltage change value from all changed monitoring numbers, and to obtain the associated monitoring number related to the reference monitoring number based on the reference monitoring number. The monitoring module is used to obtain a sub-power system model formed by the reference monitoring number and the associated monitoring number from the preset power system model, and to use the sub-power system model to obtain the short-circuit current generated when a short circuit occurs.
9. The apparatus according to claim 8, characterized in that, The device also includes an alarm module; wherein... The alarm module is used to obtain the short-circuit current generated by the short circuit using the sub-power system model, and then generate an alarm signal that corresponds one-to-one with the reference monitoring number.
10. A computer-readable storage medium having a computer program stored thereon that can run on a processor, characterized in that, When the computer program is executed by the processor, it implements a method for monitoring short-circuit current in a power system as described in any one of claims 1 to 7.