Bus protection method based on series reactor post-voltage calculation and differential current change rate fusion

Abstract

The invention provides a bus protection method based on series reactor post-voltage calculation and differential current change rate fusion, and the method comprises the steps: obtaining basic parameters of a low-voltage bus system, firstly calculating a differential current change rate based on a branch current, so as to determine a fault position parameter; the impedance value of the series reactor is corrected by using the fault position parameter, the voltage after the impedance value of the series reactor is calculated, and finally, the re-voltage locking state is judged by combining the preset re-voltage locking voltage threshold value, so that hardware equipment does not need to be additionally arranged, the real voltage characteristic of a fault point can be accurately reflected, and the impedance fluctuation of a low-voltage bus system and the access of a distributed power supply are adapted; re-voltage locking is reliably opened when a fault occurs in the tail end area of the series reactor, protection operation rejection is avoided, the accident influence range is narrowed, and safe and stable operation of a low-voltage bus and a power system is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, specifically to a bus protection method based on the fusion of series reactance voltage estimation and differential current change rate. Background Technology

[0002] In power system operation, the low-voltage busbar is a key link in power distribution and transmission, and its safe and stable operation directly affects the power supply reliability of the entire system. When a short-circuit fault occurs in a section of the low-voltage busbar, if the short-circuit current is too large, it may exceed the rated breaking capacity of the circuit breaker, causing the circuit breaker to fail to reliably interrupt the fault current, thereby expanding the scope of the fault and threatening the safety of power equipment and the continuity of power supply.

[0003] To address the issue of excessive short-circuit current, a common engineering practice is to connect series reactors in the busbar branches. Series reactors significantly reduce the short-circuit current amplitude by increasing the total impedance of the fault circuit, thereby improving the reliability of the circuit breaker in breaking fault currents and ensuring the effectiveness of system fault clearance.

[0004] However, the introduction of series reactors has also brought new protection technical challenges. When a short-circuit fault occurs at the end of the series reactor, the residual voltage on the bus side is difficult to reduce to the conventional setting value of the undervoltage criterion for the bus differential protection due to the voltage division effect of the series reactor. At the same time, due to the limitation of the system impedance characteristics, the amplitude of the negative sequence voltage on the bus side during the fault cannot meet the requirements for opening the undervoltage blocking, which directly leads to the bus differential protection failing to open because the undervoltage blocking conditions are not met, and ultimately the protection fails to operate. Summary of the Invention

[0005] This invention provides a bus protection method based on the fusion of series reactance voltage estimation and differential current change rate, which is used to solve the problem of bus protection failure to operate when a fault occurs in a branch containing series reactance.

[0006] On the one hand, this invention provides a bus protection method based on the fusion of series reactor voltage estimation and differential current change rate, applicable to low-voltage bus systems containing series reactor branches, including: Obtain the basic parameters of the low-voltage bus system, including the preset impedance parameters of the series reactor, the bus voltage on the bus side, and the branch current of each branch on the low-voltage bus. Based on the branch current, the differential current of the first bus and the differential current of the second bus at different sampling times are determined, and the differential current of the first bus, the differential current of the second bus, and the sampling time are substituted into the differential current change formula to obtain the differential current change rate. Substitute the differential current change rate and the preset impedance parameter into the calculation relationship between the differential current change rate and the fault location to obtain the fault location parameter; Based on the bus voltage, the branch current and the preset impedance parameters, the series reactor impedance value is corrected by the fault location parameters to obtain the standard series reactor impedance value. Calculate the product of the branch current and the impedance value of the standard series reactor, and calculate the difference between the bus voltage and the product to obtain the voltage after the series reactor; The voltage after the series reactor is compared with the preset complex voltage blocking voltage threshold to obtain the complex voltage blocking state result.

[0007] Optionally, based on the branch current, the differential current of the first bus and the differential current of the second bus at different sampling times are determined, and the differential current of the first bus, the differential current of the second bus, and the sampling time are substituted into the differential current change formula to obtain the differential current change rate, including: Set the first sampling time and the second sampling time; At the first sampling moment, the difference between the current in the branch where the series resistor is located and the current in the branch without the series resistor is obtained to obtain the first bus differential current. At the second sampling time, the difference between the current in the branch where the series resistor is located and the current in the branch without the series resistor is obtained to obtain the second bus differential current. Substituting the first bus differential current, the second bus differential current, the first sampling time, and the second sampling time into the differential current change formula, we obtain the differential current change rate. The differential flow variation formula is as follows: ; in, For the differential current of the first bus, For the second bus differential current, For the first sampling time, This is the second sampling time. The differential flow rate is denoted as .

[0008] Optionally, the differential current change rate and the preset impedance parameter are substituted into the calculation relationship between the differential current change rate and the fault location to obtain the fault location parameters, including: Determine the calculation relationship between the differential current change rate and the fault location; the calculation relationship is a location function including the differential current change rate, the inductance parameter of the series reactor, and the fault location parameter; The reactance component of the series reactor is extracted from the preset impedance parameters, and the inductance parameter of the series reactor is calculated by combining it with the frequency of the low-voltage bus system and using the conversion formula between reactance and inductance. Substitute the differential current change rate and the inductance parameters into the position function, and obtain the initial fault location parameters by solving. The initial value is checked within a range. If the fault location parameter is within the range of 0-1, then the initial fault location parameter is set as the fault location parameter.

[0009] Optionally, based on the bus voltage, the branch current, and the preset impedance parameters, the series reactor impedance value is corrected using the fault location parameters to obtain a standard series reactor impedance value, including: Extract the total resistance component and total reactance component of the series reactor from the preset impedance parameters; The fault location parameter is multiplied by the total resistance component to obtain the corrected series reactor operating resistance. The fault location parameters are multiplied by the total reactance component to obtain the corrected series reactor reactance. The resistance and reactance of the series reactor are integrated into a complex impedance form to obtain the standard series reactor impedance value.

[0010] Optionally, the voltage after the series reactor is compared with a preset complex voltage blocking voltage threshold to obtain the complex voltage blocking state result, including: Determine the threshold voltage for the complex voltage blocking; Extract the amplitude of the voltage after the series reactor; The amplitude of the voltage after the series reactor is compared with the threshold voltage of the complex voltage blocking. If the amplitude of the voltage after the series reactor is less than the complex voltage blocking voltage threshold, the complex voltage blocking state result is determined to meet the complex voltage blocking opening condition, and a judgment conclusion of complex voltage blocking opening is generated. If the amplitude of the voltage after the series reactor is greater than or equal to the complex voltage blocking voltage threshold, the complex voltage blocking state result is determined to be that the complex voltage blocking opening condition is not met, and a determination conclusion of complex voltage blocking maintenance is generated.

[0011] Optionally, it also includes: If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is met, then the fault is determined to be a fault within the bus protection zone, and the bus differential protection is triggered. If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is not met, the overvoltage blocking state is maintained and the bus differential protection action is not triggered.

[0012] Optionally, after substituting the differential current change rate and the preset impedance parameter into the calculation relationship between the differential current change rate and the fault location to obtain the fault location parameter, the method further includes: Determine whether the transition resistance at the fault point in the low-voltage bus system is greater than the preset resistance; If the transition resistance is greater than the preset resistance, then check whether the differential current change rate is less than the preset series reactance suppression threshold; the series reactance suppression threshold is preset based on the inductance parameters of the series reactor. If the differential current change rate is less than the series reactance suppression threshold, the validity of the fault location parameter is confirmed.

[0013] Optionally, before performing the correction of the series reactor impedance value, the following steps are also included: A hard pressure plate is installed on the branch containing the series reactor, and the state of the hard pressure plate is obtained; If the hard pressure plate is in the engaged state, then the impedance value of the series reactor is corrected. If the hard plate is in the exit state, then the correction of the series reactor impedance value and the calculation of the voltage after the series reactor are stopped.

[0014] Optionally, after calculating the difference between the bus voltage and the product to obtain the voltage after the series reactor, the method further includes: Select the bus voltage and the branch current at multiple consecutive sampling times, and calculate the initial series reactor voltage at each sampling time; The average value of the voltages after multiple initial series reactors is taken as the voltage after the series reactors; Calculate the deviation of the initial series reactor voltage calculation. If any deviation is not within the preset deviation range, recalculate the series reactor voltage.

[0015] Optionally, it also includes: Collect measured load data of the low-voltage busbar system; The preset impedance parameters are corrected based on the measured load data.

[0016] On the other hand, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the bus protection method based on series reactance post-voltage estimation and differential current change rate fusion as described above.

[0017] On the other hand, the present invention also provides a non-transient computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the bus protection method based on series reactance post-voltage estimation and differential current change rate fusion as described above.

[0018] On the other hand, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the bus protection method based on series reactance post-voltage estimation and differential current change rate fusion as described above.

[0019] The bus protection method provided by this invention, which integrates series reactor voltage estimation and differential current change rate, obtains the basic parameters of the low-voltage bus system. First, it calculates the differential current change rate based on the branch current to determine the fault location parameters. Then, it uses the fault location parameters to correct the impedance value of the series reactor and estimates the voltage after the series reactor impedance value. Finally, it combines the preset overvoltage blocking voltage threshold to determine the overvoltage blocking status. No additional hardware equipment is required. It can accurately reflect the real voltage characteristics of the fault point, adapt to impedance fluctuations and distributed power supply access in the low-voltage bus system, ensure reliable opening of overvoltage blocking when there is a fault in the end zone of the series reactor, avoid protection failure to operate, reduce the impact range of the accident, and ensure the safe and stable operation of the low-voltage bus and the power system. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the bus protection method based on series reactance voltage estimation and differential current change rate fusion provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the low-voltage busbar configuration provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a low-voltage busbar branch provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a short-circuit fault in a series reactor branch provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] Figure 1 This is a flowchart illustrating the bus protection method based on series reactance voltage estimation and differential current change rate fusion provided in this embodiment of the invention.

[0024] The bus protection method based on voltage estimation after series reactor and differential current change rate fusion provided in this invention is applied to low-voltage bus systems containing series reactor branches. The low-voltage bus system containing series reactor branches is as follows: Figure 2 As shown, 3822, 3823, 3824, and 3825 are circuit breakers for outgoing lines or capacitors / reactors on the 35kV side; 212 is a 220kV high-voltage side circuit breaker; 312 is a 35kV low-voltage side circuit breaker; 5011 is a 500kV ultra-high-voltage side circuit breaker; 5012 is a busbar circuit breaker for bus #1; and 5013 is a busbar circuit breaker for bus #2. The low-voltage side busbar scenario in a 500kV substation is a crucial link in the power system for power distribution and transmission, including multiple functional branches. To address the issue of short-circuit currents easily exceeding the rated breaking capacity of circuit breakers in situations such as proximity to the low-voltage side of transformers and large busbar cross-sections, reactors are connected in series between the switches in specific branches, such as the station service transformer bay, and the low-voltage busbar. This increases the total impedance of the fault circuit, reducing the short-circuit current and improving the reliability of the circuit breaker in breaking fault currents. Low-voltage busbar systems are typically single-power-source systems, with the main transformer of the substation on the power supply side and downstream equipment such as station service transformers on the load side. However, the introduction of series reactors also presents protection challenges for low-voltage busbar systems. When a short-circuit fault occurs at the end of the series reactor, the voltage division effect of the series reactor makes it difficult for the residual voltage on the busbar side to drop to the setting value of the low-voltage criterion for the differential protection undervoltage blocking. At the same time, the negative sequence voltage amplitude is insufficient, which can easily cause the differential protection to fail to operate due to the failure of the undervoltage blocking to open, which may lead to the spread and expansion of the fault.

[0025] To address the issue of bus protection malfunctioning when a fault occurs in a branch containing series reactors, such as... Figure 1 As shown, the bus protection method based on series reactance voltage estimation and differential current change rate fusion provided in this embodiment of the invention mainly includes the following steps: 101. Obtain the basic parameters of the low-voltage busbar system.

[0026] The basic parameters of the low-voltage bus system include the preset impedance parameters of the series reactor, the bus voltage on the bus side, and the branch current of each branch on the low-voltage bus.

[0027] Specifically, the preset impedance parameters of the series reactor are inherent technical parameters of the series reactor and can be extracted from the manufacturer's technical data. The series reactor is specifically in the form of complex impedance, including the total resistance component and the total reactance component. In addition, the preset impedance parameters of the series reactor are also dynamically calibrated in conjunction with the quarterly load measurement data of the low-voltage bus system to ensure that the parameters match the actual operating conditions of the system.

[0028] For the bus voltage on the bus side, synchronous acquisition is performed by a high-frequency sampling unit configured on the low-voltage bus, such as a 1MHz ADC module. The sampling process needs to capture the instantaneous value of the bus voltage in real time to ensure that the acquired data can truly reflect the voltage status on the bus side.

[0029] The branch current of each branch on the low-voltage bus is collected by the current transformer configured for each branch. The current of the branch with the series reactor and the branch without the series reactor must be collected. The collected current data must be synchronized with the bus voltage data on the bus side to provide accurate basic data for subsequent differential current calculation and differential current change rate analysis.

[0030] 102. Based on the branch current, determine the differential current of the first bus and the differential current of the second bus at different sampling times, and substitute the differential current of the first bus, the differential current of the second bus, and the sampling time into the differential current change formula to obtain the differential current change rate.

[0031] Among them, the differential current change rate is the core data for determining the fault location parameter. By substituting the differential current change rate and the preset impedance parameter of the series reactor into the correlation calculation relationship, the fault location parameter reflecting the location of the fault point on the series reactor can be obtained, providing key data support for subsequent correction of the series reactor impedance value. In addition, the differential current change rate can reflect the change of the bus differential current over time, providing a reference for judging the fault development trend and subsequent bus protection operation. It helps to accurately identify faults in the bus protection zone, ensures reliable opening of the overvoltage blocking when a fault occurs in the end zone of the series reactor, and avoids protection failure to operate.

[0032] Specifically, based on the branch current, the differential current of the first bus and the second bus at different sampling times are determined. The differential currents of the first bus, the second bus, and the sampling times are then substituted into the differential current variation formula to obtain the differential current variation rate, including: Set the first sampling time and the second sampling time.

[0033] At the first sampling moment, the difference between the current in the branch containing the series resistor and the current in the branch without the series resistor is obtained to obtain the first bus differential current.

[0034] At the second sampling time, the difference between the current in the branch containing the series resistor and the current in the branch without the series resistor is obtained to obtain the second bus differential current.

[0035] Substituting the differential current of the first busbar, the differential current of the second busbar, the first sampling time, and the second sampling time into the differential current change formula, we obtain the differential current change rate.

[0036] The process begins by setting the first and second sampling times. Using a 1MHz ADC module, two consecutive, interference-free times are selected according to a synchronous sampling mechanism. The time interval between the first and second sampling times must accurately capture the transient current changes during a fault, avoiding loss of differential current characteristics due to excessively long intervals or introduction of sampling noise due to excessively short intervals. Next, at the first sampling time, the branch containing the series reactor is selected from the currents collected from each branch of the low-voltage bus. Figure 3 As shown, the current of the transformer bay branch at station 3825, which has a series reactor configured between the switch and the low-voltage bus, and the current of a branch without a series reactor, such as the capacitor bay branch at 3823, are calculated by subtracting the current values ​​of these two branches at the first sampling time. The result is the first bus differential current. Then, at the second sampling time, the same branch selection criteria as at the first sampling time are maintained, and the branch with the series reactor and the branch without the series reactor are selected. The synchronous sampling current values ​​of the two branches at the second sampling time are extracted, and the difference calculation method is used in the same way as for calculating the first bus differential current to obtain the second bus differential current. Finally, the first bus differential current, the second bus differential current, the first sampling time, and the second sampling time are substituted into the differential current change formula to obtain the differential current change rate that reflects the transient characteristics of the fault.

[0037] The differential flow variation formula is as follows: ; in, For the first bus differential current, For the second bus differential current, This is the first sampling time. This is the second sampling time. This represents the differential flow rate.

[0038] 103. Substitute the differential current change rate and the preset impedance parameters into the calculation relationship between the associated differential current change rate and the fault location to obtain the fault location parameters.

[0039] The fault location parameter is a percentage coefficient representing the distance of the fault point from the busbar side, ranging from 0 to 1. Its purpose is to provide a basis for correcting the impedance value of the series reactor, thereby ensuring the accuracy of voltage calculation after the series reactor and ultimately solving the problem of traditional voltage-complexing blocking failure caused by series reactor voltage division. Specifically, since short-circuit faults can occur at any location on the series reactor, the actual effective impedance of the series reactor varies depending on the fault location. The closer the fault point is to the end of the series reactor, the greater the series reactor impedance participating in voltage division, and the more significant the difference between the residual voltage on the busbar side and the voltage at the fault point. Therefore, the fault location parameter quantifies the relative positional relationship between the fault point and the busbar side.

[0040] The fault location parameters are obtained by substituting the differential current change rate and the preset impedance parameters into the calculation relationship between the differential current change rate and the fault location, including: Determine the calculation relationship between the differential current change rate and the fault location; wherein the calculation relationship includes the location function of the differential current change rate, the inductance parameter of the series reactor, and the fault location parameter; The reactance component of the series reactor is extracted from the preset impedance parameters. Combined with the frequency of the low-voltage bus system, the inductance parameter of the series reactor is calculated using the conversion formula between reactance and inductance. Substitute the differential current change rate and inductance parameters into the position function, and solve to obtain the initial fault location parameters. Perform interval verification on the initial value. If the fault location parameter is within the range of 0-1, then set the initial fault location parameter to the fault location parameter.

[0041] Specifically, the calculation relationship between the differential current change rate and the fault location is determined. The calculation relationship is a location function constructed for a low-voltage bus system with a series reactor branch. The location function includes the differential current change rate, the inductance parameter of the series reactor, and the fault location parameter, which can realize the quantitative correlation between the three and provide a mathematical basis for subsequent fault location calculation.

[0042] Next, the reactance component is extracted from the preset impedance parameters of the series reactor. Combined with the actual operating frequency of the low-voltage bus system, the inductance parameters of the series reactor are calculated using the standard conversion formula between reactance and inductance, ensuring that the inductance parameters conform to the actual operating conditions of the system.

[0043] Subsequently, the differential current change rate and the inductance parameters of the series reactor are substituted into the position function, and the initial fault position parameters are obtained by solving the function. The initial fault position parameters initially reflect the position of the fault point relative to the bus side.

[0044] Finally, the initial fault location parameters are checked for range to determine whether they fall within the 0-1 range. If the initial fault location parameters meet the range requirements, they are determined as the final fault location parameters. If they exceed the range, the data and calculation process of the preceding steps need to be checked again to ensure the accuracy and rationality of the fault location parameters.

[0045] The position function is: ； in, For fault location parameters, For the current in the series reactor branch, The resistance component of the series reactor. These are the inductance parameters of the series reactor. For the frequency of the low-voltage bus system, The imaginary unit, This represents the differential flow rate.

[0046] 104. Based on the bus voltage, bus current and preset impedance parameters, the impedance value of the series reactor is corrected by the fault location parameters to obtain the standard impedance value of the series reactor.

[0047] Among them, correcting the impedance value of the series reactor can match the actual impedance from the fault point to the bus side, providing a reliable basis for calculating the voltage after the series reactor, thereby ensuring the reliability of the protection criteria.

[0048] Specifically, based on the bus voltage, bus current, and preset impedance parameters, the series reactor impedance value is corrected using fault location parameters to obtain the standard series reactor impedance value, including: Extract the total resistance and total reactance components of the series reactor from the preset impedance parameters; The fault location parameters are multiplied by the total resistance component to obtain the corrected series reactor operating resistance. The fault location parameters are multiplied by the total reactance component to obtain the corrected series reactor reactance. The effective resistance and effective reactance of the series reactor are integrated into a complex impedance form to obtain the standard series reactor impedance value.

[0049] Among them, the total resistance component and the total reactance component are extracted from the preset impedance parameters of the series reactor. The total resistance component and the total reactance component are the inherent parameters of the series reactor as a complex impedance.

[0050] Subsequently, since the location of the fault point on the series reactor affects the proportion of resistance in the actual fault circuit impedance, and the fault location parameter can reflect the proportion of effective resistance, the fault location parameter used to quantify the relative position of the fault point from the bus side is multiplied with the extracted total resistance component to obtain the corrected series reactor effective resistance.

[0051] Similarly, the fault location determines the proportion of effective reactance that actually participates in voltage division and affects the circuit reactance characteristics. Therefore, by multiplying the fault location parameter with the total reactance component, the corrected series reactor reactance is obtained.

[0052] Finally, the operating resistance and reactance of the series reactor, after being corrected for the fault location parameters, are integrated into a complex impedance form of resistance + j × reactance. This yields a standard series reactor impedance value that matches the actual impedance characteristics of the series reactor at the current fault location, providing an accurate basis for subsequent protection-related calculations such as voltage estimation after the series reactor.

[0053] 105. Calculate the product of the branch current and the impedance value of the standard series reactor, and calculate the difference between the bus voltage and the product to obtain the voltage after the series reactor.

[0054] In calculating the voltage after the series reactor, the branch current and the standard series reactor impedance value, corrected for fault location parameters, are first obtained. Based on the relationship between voltage, current, and impedance in the circuit, the product of the branch current and the standard series reactor impedance value is calculated. This product represents the voltage drop across the series reactor at the current fault location, reflecting the actual voltage division of the series reactor. Finally, the bus voltage on the bus side is subtracted from this product; the difference is the voltage after the series reactor, which is the true voltage at the fault point of the series reactor and reflects the voltage state at the fault point when the fault occurs.

[0055] 106. Compare the voltage after the series reactor with the preset overvoltage blocking voltage threshold to obtain the overvoltage blocking state result.

[0056] The process involves obtaining the voltage after the series reactor, then retrieving the pre-set overvoltage blocking voltage threshold based on protection requirements and operating characteristics. The voltage after the series reactor is compared with this overvoltage blocking voltage threshold: if the voltage after the series reactor is lower than the overvoltage blocking voltage threshold, or if its negative sequence voltage component is higher than the negative sequence voltage threshold, the overvoltage blocking condition is considered met. Conversely, if the threshold requirements are not met, the overvoltage blocking remains in the blocked state. Finally, through this comparison process, the overvoltage blocking state result is obtained. This result serves as a key condition in subsequent bus protection action criteria, ensuring accurate response of the protection device under fault scenarios and preventing protection failure or maloperation due to abnormal residual voltage on the bus side caused by voltage division from the series reactor.

[0057] Specifically, the voltage after the series reactor is compared with the preset complex voltage blocking voltage threshold to obtain the complex voltage blocking state result, including: Determine the threshold voltage for the complex voltage blocking; Extract the amplitude of the voltage after the series reactor; The amplitude of the voltage after the series reactor is numerically compared with the overvoltage blocking voltage threshold. If the amplitude of the voltage after the series reactor is less than the voltage threshold of the complex voltage blocking, the complex voltage blocking state is determined to meet the condition for opening the complex voltage blocking, and a judgment conclusion of opening the complex voltage blocking is generated. If the amplitude of the voltage after the series reactor is greater than or equal to the overvoltage blocking voltage threshold, the result of the overvoltage blocking state is determined to be that the overvoltage blocking opening condition is not met, and a determination conclusion of overvoltage blocking maintenance is generated.

[0058] The first step is to determine the overvoltage blocking voltage threshold. This threshold needs to be set in conjunction with the low-voltage busbar system protection design requirements and the rated voltage of the low-voltage busbar. For example, the rated voltage of the 35kV busbar on the low-voltage side of a 500kV substation is... The threshold voltage for the complex voltage blocking is set to 0.7. The voltage threshold for the overvoltage blocking is used as the voltage baseline for determining whether the overvoltage blocking is open.

[0059] Next, the amplitude of the voltage after the series reactor is extracted, which reflects the electrical quantity of the actual voltage at the fault point. This needs to be calculated by the amplitude, such as by summing the squares of the real and imaginary parts and taking the arithmetic square root to obtain the voltage amplitude. This ensures that the actual voltage magnitude is compared in the subsequent comparisons, and avoids the phase characteristics of the complex voltage affecting the judgment result.

[0060] Then, the amplitude of the voltage after the series reactor is compared with the voltage threshold of the overvoltage blocking. The comparison process must ensure that both are based on the same voltage unit and reference, such as actual voltage values ​​or per-unit values ​​relative to the rated voltage of the bus, to eliminate comparison deviations caused by inconsistent units or references.

[0061] If the comparison result shows that the amplitude of the voltage after the series reactor is less than the voltage threshold of the overvoltage blocking, it indicates that the voltage on the fault point side has dropped significantly to meet the conditions for overvoltage blocking to open. Even if the voltage on the bus side does not meet the standard due to the voltage division of the series reactor, the result of the overvoltage blocking state is still determined to meet the conditions for overvoltage blocking to open, and a judgment conclusion of overvoltage blocking to open is generated, providing a key premise for the operation of the bus protection.

[0062] If the comparison result shows that the amplitude of the voltage after the series reactor is greater than or equal to the overvoltage blocking voltage threshold, it indicates that the voltage on the fault side has not reached the voltage requirement for overvoltage blocking to open. The result of the overvoltage blocking status is determined to be that the overvoltage blocking opening condition is not met, and a judgment conclusion of overvoltage blocking maintenance is generated to avoid protection maloperation and ensure the stable operation of the low-voltage bus system when there is no fault or the voltage does not meet the opening condition.

[0063] In some embodiments, the bus protection method based on series reactance voltage estimation and differential current change rate fusion provided in this application further includes: If the result of the overvoltage blocking status is that the overvoltage blocking opening condition is met, then the fault is determined to be a fault within the bus protection zone, and the bus differential protection is triggered. If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is not met, the overvoltage blocking state will be maintained and the bus differential protection will not be triggered.

[0064] If the result of the overvoltage blocking state meets the overvoltage blocking opening condition, that is, the voltage amplitude after the series reactor is less than the preset overvoltage blocking voltage threshold, then combined with the protection zone definition of the low-voltage bus protection, the fault is determined to be a fault within the bus protection zone. At this time, the bus differential protection needs to be triggered to reliably cut off the fault branch current and prevent the fault from spreading further to other areas such as the main transformer protection operating zone, thus solving the problem of protection failure caused by the failure of traditional overvoltage blocking.

[0065] If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is not met, that is, the voltage amplitude after the series reactor is greater than or equal to the overvoltage blocking voltage threshold, it indicates that the current voltage state does not meet the voltage requirements for fault judgment. It may be a non-faulty condition or the fault is not in the bus protection zone. At this time, the overvoltage blocking state should be maintained to prevent the bus differential protection from being triggered, so as to avoid the protection maloperation from affecting the stable operation of the low-voltage bus system. At the same time, the anti-interference capability of the overvoltage blocking itself should be preserved to ensure the normal power supply of the system in non-faulty scenarios.

[0066] In some embodiments, after substituting the differential current change rate and the preset impedance parameter into the calculation relationship between the associated differential current change rate and the fault location to obtain the fault location parameter, the method further includes: Determine whether the transition resistance at the fault point in the low-voltage busbar system is greater than the preset resistance; If the transition resistance is greater than the preset resistance, then check whether the differential current change rate is less than the preset series reactance suppression threshold; the series reactance suppression threshold is preset based on the inductance parameters of the series reactor. If the differential current change rate is less than the series reactance suppression threshold, the validity of the fault location parameters is confirmed.

[0067] In this process, the fault characteristics of the low-voltage busbar system are considered to determine whether the transition resistance at the fault point is greater than the preset resistance.

[0068] If the transition resistance is determined to be greater than the preset resistance, it indicates that there may be a deviation in the voltage calculation based solely on the series reactance. Further verification is needed to determine whether the differential current change rate is less than the preset series reactance suppression threshold. The series reactance suppression threshold is preset based on the inductance parameter of the series reactor. It is based on the characteristic that the series reactance inductance is negatively correlated with the differential current change rate, that is, the larger the series reactance inductance, the stronger the suppression effect on the differential current change rate. The series reactance suppression threshold is set in accordance with the current series reactance configuration.

[0069] If the differential current change rate is less than the series reactance suppression threshold, it indicates that the differential current change rate conforms to the current transient characteristics when the series reactance exists. This can corroborate that the fault location parameters can truly reflect the relative position of the fault point and the bus side, thereby confirming the validity of the fault location parameters and providing a reliable basis for subsequent correction of the series reactance impedance and calculation of the voltage after the series reactor.

[0070] In some embodiments, before performing the correction of the series reactor impedance value, the method further includes: A hard plate is installed on the branch containing the series reactor, and the status of the hard plate is obtained; If the hard plate is in the engaged state, then the impedance value of the series reactor is corrected. If the hard plate is in the exit state, then the correction of the series reactor impedance value and the calculation of the voltage after the series reactor will stop.

[0071] Before performing the operation to correct the impedance value of the series reactor, the configuration and status determination steps related to the hard plate must be completed first. First, a dedicated hard plate is configured on the branch containing the series reactor. The hard plate is used to control whether to enable the adaptive protection logic related to the series reactor.

[0072] Next, the current status of the hard platen is obtained in real time to determine whether the hard platen is in the enabled or disabled state. If the hard platen is in the enabled state, it indicates that the low-voltage bus system needs to enable the protection logic for the series reactor scenario. At this time, the subsequent series reactor impedance value correction operation can continue to be executed. If the hard platen is in the disabled state, it indicates that the low-voltage bus system does not need to enable the adaptive logic related to the series reactor. The series reactor impedance value correction operation needs to be stopped, and the subsequent series reactor voltage calculation operation also needs to be stopped to avoid unnecessary calculations from interfering with the protection logic. This ensures that the bus protection system only starts the corresponding function when it needs to adapt to the series reactor scenario.

[0073] In some embodiments, after calculating the difference between the bus voltage and the product to obtain the voltage after the series reactor, the method further includes: Select the bus voltage and branch current at multiple consecutive sampling times, and calculate the initial series reactor voltage at each sampling time. The average value of the voltages after multiple initial series reactors is taken as the voltage after the series reactors. Calculate the deviation of the initial series reactor voltage calculation. If any deviation is not within the preset deviation range, recalculate the series reactor voltage.

[0074] First, a 1MHz ADC module is used to synchronously acquire bus voltage and branch current. Bus voltage and branch current data at multiple consecutive sampling times are selected to ensure the synchronization of data acquisition at each time to avoid timing deviation.

[0075] Next, for each sampling time, combined with the preset impedance parameters of the series reactor, the initial series reactor voltage at each time is calculated by reverse derivation of the formula for the voltage after series reactor.

[0076] Subsequently, an arithmetic average was calculated for all initial series reactor voltages, and the average value was used as the final series reactor voltage to reduce the impact of sampling errors at a single moment on the result.

[0077] Finally, the deviation between the voltage after each initial series reactor and the average value is calculated. If any deviation is not within the preset reasonable deviation range, it is determined that the current sampling data is abnormal. The bus voltage and branch current at the continuous sampling time need to be reselected, and the initial voltage calculation, averaging calculation and deviation verification process is repeated until all deviations meet the requirements. This ensures that the final voltage after the series reactor can accurately reflect the real voltage state on the fault point side, providing a basis for the overvoltage blocking determination.

[0078] In some embodiments, the bus protection method based on series reactance voltage estimation and differential current change rate fusion provided in this application further includes: Collect measured load data of the low-voltage busbar system; The preset impedance parameters are corrected based on the actual load measurement data.

[0079] The measured load data specifically includes the load current and power factor of the station service transformer and parameters related to the actual operating load of the system. The data collection must follow the principle of regularity to capture the dynamic changes in the load.

[0080] Subsequently, the preset impedance parameters of the series reactor are calibrated based on the collected load measurement data, with a focus on the changes in load current during the calibration process. If the quarterly average change in load current exceeds the preset reasonable range, it indicates a deviation between the actual operating conditions of the series reactor and the operating conditions corresponding to the preset impedance parameters. In this case, the resistance component of the preset impedance of the series reactor needs to be corrected according to the change ratio of load current to ensure that the corrected preset impedance parameters can accurately match the actual impedance characteristics of the series reactor under the current load condition. This provides accurate basic parameters for subsequent steps such as voltage extrapolation after series reactor connection and differential current change rate calculation, thereby improving the adaptability and judgment accuracy of the entire bus protection method.

[0081] like Figure 4 As shown, Figure 4 This is a schematic diagram of a short-circuit fault in a series reactor branch. When the fault occurs at the end of the series reactor... Figure 4 In the case of a fault occurring between the series reactor and the 3825 switch, the series reactor will share most of the fault voltage drop, resulting in a still relatively high bus voltage that does not reach the blocking and opening threshold. The voltage threshold for the overvoltage blocking is difficult to meet, and the criterion failure protection fails to operate, thus allowing the fault to further develop into the main transformer protection operating area, thereby expanding the scope of the accident.

[0082] Voltage after series reactance It has dropped significantly. The voltage correction criterion is derived by calculating the series reactance.

[0083] Using the known parameters of series reactance impedance Bus voltage and branch current Reverse calculation of the voltage after series reactance: Without loss of generality, it is assumed that the fault occurs at a certain percentage of the distance from the busbar side. (0<) <1). Since the station becomes the load side, it is a single-power supply system, and the end of the series reactor is at the same potential as the fault point. Therefore, the voltage at the end of the series reactor is: (1) In extreme cases, when the fault occurs on the bus side ( When =0), At this point, using reverse calculation, the voltage after series reactor recalculation equals the bus voltage, and the overvoltage blocking criterion can be opened normally. When the fault occurs at the end of the series reactor ( When =1), , This represents the fault voltage, and the voltage drop must meet the conditions for opening the re-voltage lockout.

[0084] in, This is the measured voltage on the bus side. This is the branch current. If the calculated... If the voltage threshold of the overvoltage blocking is less than the threshold, it is determined that the voltage near the fault point has met the opening condition, even if... If the standard is not met, the pressure interlock will remain open.

[0085] The bus protection method provided in this application, which is based on voltage estimation after series reactance and differential current change rate fusion, does not require the addition of an additional voltage transformer. It can reflect the true voltage state at the fault point using only existing electrical quantities and series reactance parameters, and specifically solves the problem of voltage criterion failure caused by series reactance voltage division.

[0086] Figure 5 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention.

[0087] like Figure 5 As shown, the electronic device may include a processor 510, a communications interface 520, a memory 530, and a communication bus 540. The processor 510, communications interface 520, and memory 530 communicate with each other via the communication bus 540. The processor 510 can call logic instructions from the memory 530 to execute a bus protection method based on series reactance voltage estimation and differential current change rate fusion.

[0088] Furthermore, the logical instructions in the aforementioned memory 530 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0089] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the bus protection method based on series reactance post-voltage estimation and differential current change rate fusion provided by the above methods.

[0090] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the bus protection method based on series reactance post-voltage estimation and differential current change rate fusion provided by the above methods.

[0091] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0092] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bus protection method based on the fusion of series reactor voltage estimation and differential current change rate, applied to a low-voltage bus system containing series reactor branches, characterized in that, include: Obtain the basic parameters of the low-voltage bus system, including the preset impedance parameters of the series reactor, the bus voltage on the bus side, and the branch current of each branch on the low-voltage bus. Based on the branch current, the differential current of the first bus and the differential current of the second bus at different sampling times are determined, and the differential current of the first bus, the differential current of the second bus, and the sampling time are substituted into the differential current change formula to obtain the differential current change rate. Substitute the differential current change rate and the preset impedance parameter into the calculation relationship between the differential current change rate and the fault location to obtain the fault location parameter; Based on the bus voltage, the branch current and the preset impedance parameters, the series reactor impedance value is corrected by the fault location parameters to obtain the standard series reactor impedance value. Calculate the product of the branch current and the impedance value of the standard series reactor, and calculate the difference between the bus voltage and the product to obtain the voltage after the series reactor; The voltage after the series reactor is compared with the preset complex voltage blocking voltage threshold to obtain the complex voltage blocking state result.

2. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Based on the branch current, the differential current of the first bus and the differential current of the second bus at different sampling times are determined. The differential current of the first bus, the differential current of the second bus, and the sampling time are then substituted into the differential current variation formula to obtain the differential current variation rate, including: Set the first sampling time and the second sampling time; At the first sampling moment, the difference between the current in the branch where the series resistor is located and the current in the branch without the series resistor is obtained to obtain the first bus differential current. At the second sampling time, the difference between the current in the branch where the series resistor is located and the current in the branch without the series resistor is obtained to obtain the second bus differential current. Substituting the first bus differential current, the second bus differential current, the first sampling time, and the second sampling time into the differential current change formula, we obtain the differential current change rate. The differential flow variation formula is as follows: ； in, For the differential current of the first bus, For the second bus differential current, For the first sampling time, This is the second sampling time. The differential flow rate is denoted as .

3. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Substituting the differential current change rate and the preset impedance parameter into the calculation relationship between the differential current change rate and the fault location, the fault location parameters are obtained, including: Determine the calculation relationship between the differential current change rate and the fault location; the calculation relationship is a location function including the differential current change rate, the inductance parameter of the series reactor, and the fault location parameter; The reactance component of the series reactor is extracted from the preset impedance parameters, and the inductance parameter of the series reactor is calculated by combining it with the frequency of the low-voltage bus system and using the conversion formula between reactance and inductance. Substitute the differential current change rate and the inductance parameters into the position function, and obtain the initial fault location parameters by solving. The initial value is checked within a range. If the fault location parameter is within the range of 0-1, then the initial fault location parameter is set as the fault location parameter.

4. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Based on the bus voltage, the branch current, and the preset impedance parameters, the series reactor impedance value is corrected using the fault location parameters to obtain the standard series reactor impedance value, including: Extract the total resistance component and total reactance component of the series reactor from the preset impedance parameters; The fault location parameter is multiplied by the total resistance component to obtain the corrected series reactor operating resistance. The fault location parameters are multiplied by the total reactance component to obtain the corrected series reactor reactance. The resistance and reactance of the series reactor are integrated into a complex impedance form to obtain the standard series reactor impedance value.

5. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, The voltage after the series reactor is compared with a preset complex voltage blocking voltage threshold to obtain the complex voltage blocking state result, including: Determine the threshold voltage for the complex voltage blocking; Extract the amplitude of the voltage after the series reactor; The amplitude of the voltage after the series reactor is compared with the threshold voltage of the complex voltage blocking. If the amplitude of the voltage after the series reactor is less than the complex voltage blocking voltage threshold, the complex voltage blocking state result is determined to meet the complex voltage blocking opening condition, and a judgment conclusion of complex voltage blocking opening is generated. If the amplitude of the voltage after the series reactor is greater than or equal to the complex voltage blocking voltage threshold, the complex voltage blocking state result is determined to be that the complex voltage blocking opening condition is not met, and a determination conclusion of complex voltage blocking maintenance is generated.

6. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Also includes: If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is met, then the fault is determined to be a fault within the bus protection zone, and the bus differential protection is triggered. If the result of the overvoltage blocking state is that the overvoltage blocking opening condition is not met, the overvoltage blocking state is maintained and the bus differential protection action is not triggered.

7. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, After substituting the differential current change rate and the preset impedance parameter into the calculation relationship between the differential current change rate and the fault location to obtain the fault location parameters, the method further includes: Determine whether the transition resistance at the fault point in the low-voltage bus system is greater than the preset resistance; If the transition resistance is greater than the preset resistance, then check whether the differential current change rate is less than the preset series reactance suppression threshold; the series reactance suppression threshold is preset based on the inductance parameters of the series reactor. If the differential current change rate is less than the series reactance suppression threshold, the validity of the fault location parameter is confirmed.

8. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Before correcting the series reactor impedance value, the following steps are also included: A hard pressure plate is installed on the branch containing the series reactor, and the state of the hard pressure plate is obtained; If the hard pressure plate is in the engaged state, then the impedance value of the series reactor is corrected. If the hard plate is in the exit state, then the correction of the series reactor impedance value and the calculation of the voltage after the series reactor are stopped.

9. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, After calculating the difference between the bus voltage and the product to obtain the voltage after the series reactor, the method further includes: Select the bus voltage and the branch current at multiple consecutive sampling times, and calculate the initial series reactor voltage at each sampling time; The average value of the voltages after multiple initial series reactors is taken as the voltage after the series reactors; Calculate the deviation of the initial series reactor voltage calculation. If any deviation is not within the preset deviation range, recalculate the series reactor voltage.

10. The bus protection method based on series reactance voltage estimation and differential current change rate fusion according to claim 1, characterized in that, Also includes: Collect measured load data of the low-voltage busbar system; The preset impedance parameters are corrected based on the measured load data.

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