Line underreach protection method, apparatus, device, medium and product

Abstract

This application relates to a method, apparatus, device, medium, and product for under-range protection of a line. The method includes: upon detecting a fault in the protected line, determining the zero-mode current component corresponding to the voltage and current data of the protected line; decomposing the zero-mode current component to obtain two preset sub-frequency band signals, and determining the instantaneous amplitude and instantaneous phase corresponding to each preset sub-frequency band signal; determining the actual time difference between the two preset sub-frequency band signals based on their respective instantaneous amplitudes; and determining the theoretical time difference between the two preset sub-frequency band signals based on their respective instantaneous phases; and performing protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference. This application can promptly perform under-range protection actions and improve the accuracy of under-range protection actions.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to a method, apparatus, device, medium, and product for line underrange protection. Background Technology

[0002] The stable operation of modern large-scale power grids relies heavily on the ability of relay protection systems to quickly, reliably, and selectively isolate faults. Under-range protection is an important component of power system relay protection. Its main function is to act as a reliable backup measure to quickly isolate faults when the main protection or the opposite protection fails, preventing the fault range from expanding and ensuring the stable operation of the system. Its importance is self-evident.

[0003] Currently, single-ended protection technology based on traveling wave signals has been proposed and developed. This technology utilizes the transient traveling wave high-frequency signal generated at the moment of a fault for ranging and location. The fault information contained in its wavefront is not constrained by the steady-state characteristics of power frequency electrical quantities, and therefore theoretically is not affected by system oscillations, transition resistance, and current transformer saturation, possessing the potential for ultra-high-speed operation. However, single-ended protection based on traveling waves also has its own problems: the wavefront recognition algorithm is complex, leading to a delay in the protection action of under-range protection, i.e., it cannot perform under-range protection action in a timely manner; moreover, setting the propagation speed to a fixed value, but in reality, different frequency components propagate at different speeds, thus the accuracy of under-range protection action is poor. Summary of the Invention

[0004] Therefore, it is necessary to provide a line under-range protection method, device, equipment, medium, and product that can perform under-range protection actions in a timely manner and improve the accuracy of under-range protection actions, in order to address the above-mentioned technical problems.

[0005] In a first aspect, this application provides a method for under-range protection of a line, comprising: when a fault is detected in the protected line, determining the zero-mode current component corresponding to the voltage and current data of the protected line; performing signal decomposition on the zero-mode current component to obtain two preset sub-frequency band signals, and determining the instantaneous amplitude and instantaneous phase corresponding to each preset sub-frequency band signal; determining the actual time difference between the two preset sub-frequency band signals based on the instantaneous amplitudes corresponding to the two preset sub-frequency band signals respectively; and determining the theoretical time difference between the two preset sub-frequency band signals based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively; and performing protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference.

[0006] In one embodiment, determining the actual time difference between two preset sub-frequency band signals based on their respective instantaneous amplitude values ​​includes: for each preset sub-frequency band signal, determining the occurrence time of the first peak in the preset sub-frequency band signal based on the instantaneous amplitude value corresponding to the preset sub-frequency band signal; and determining the actual time difference between the two preset sub-frequency band signals based on the absolute value of the difference between the determined occurrence times.

[0007] In one embodiment, determining the theoretical time difference between two preset sub-frequency band signals based on their respective instantaneous phases includes: for each preset sub-frequency band signal, determining the instantaneous center frequency of the preset sub-frequency band signal based on its corresponding instantaneous phase, and determining the theoretical wave velocity of the preset sub-frequency band signal based on its instantaneous center frequency; and determining the theoretical time difference between the two preset sub-frequency band signals based on the determined theoretical wave velocities.

[0008] In one embodiment, determining the theoretical wave velocity of a preset sub-band signal based on the instantaneous center frequency includes: determining the unit inductance and unit capacitance at the corresponding frequency of the preset sub-band signal based on the instantaneous center frequency of the preset sub-band signal; and determining the theoretical wave velocity of the preset sub-band signal based on the unit inductance and unit capacitance.

[0009] In one embodiment, protection processing is performed on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference, including: initiating protection action on the under-range protection area of ​​the protected line when the actual time difference and the theoretical time difference meet preset conditions; wherein, the preset conditions include the actual time difference being less than the product of the theoretical time difference and a preset coefficient.

[0010] In one embodiment, detecting a fault in a protected line includes: extracting a fundamental voltage signal from the voltage and current data of the protected line; performing orthogonal decomposition on the fundamental voltage signal to obtain initial state data; performing state prediction based on the initial state data to obtain at least one predicted state data; determining at least one predicted difference data based on each predicted state data and the actual state data corresponding to the fundamental voltage signal; and determining that a fault has been detected in the protected line if at least one of the predicted difference data has an absolute value greater than a preset difference threshold.

[0011] Secondly, this application also provides a line under-range protection device, comprising: a first determining module, configured to determine the zero-mode current component corresponding to the voltage and current data of the protected line when a fault is detected in the protected line; a first decomposition module, configured to decompose the zero-mode current component into two preset sub-frequency band signals, and determine the instantaneous amplitude and instantaneous phase corresponding to each preset sub-frequency band signal; a second determining module, configured to determine the actual time difference between the two preset sub-frequency band signals based on the instantaneous amplitudes corresponding to the two preset sub-frequency band signals respectively; and a third determining module, configured to determine the theoretical time difference between the two preset sub-frequency band signals based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively; and a protection processing module, configured to perform protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference.

[0012] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method provided in the first aspect.

[0013] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method provided in the first aspect.

[0014] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the method provided in the first aspect.

[0015] The aforementioned under-range protection method, device, equipment, medium, and product, upon detecting a fault in the protected line, determine the zero-mode current component corresponding to the voltage and current data of the protected line. The zero-mode current component is then decomposed to obtain two preset sub-frequency band signals. The actual time difference between the two preset sub-frequency band signals is determined based on their instantaneous amplitudes, and the theoretical time difference is determined based on their instantaneous phases. Finally, protection processing is applied to the under-range protection area of ​​the protected line based solely on the actual and theoretical time differences. This embodiment eliminates the need for wavefront identification, avoiding delays in protection action due to complex wavefront identification algorithms, and ensuring timely under-range protection. Furthermore, this embodiment does not require setting the propagation speed of each frequency component to a fixed value, thus avoiding errors caused by setting the propagation speed to a fixed value and improving the accuracy of the protection action. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1A This is a flowchart illustrating a line under-range protection method in one embodiment;

[0018] Figure 1B This is a schematic diagram showing the change of the amplitude of the zero-mode current component over time in one embodiment;

[0019] Figure 2 This is a flowchart illustrating the steps for determining the actual time difference in one embodiment.

[0020] Figure 3A This is a flowchart illustrating the steps for determining the theoretical time difference in one embodiment;

[0021] Figure 3B This is a schematic diagram of the instantaneous center frequency of a preset sub-band signal in one embodiment;

[0022] Figure 3C This is a schematic diagram of the instantaneous center frequency of another preset sub-band signal in one embodiment;

[0023] Figure 4 This is a flowchart illustrating the steps for determining the theoretical wave velocity in one embodiment.

[0024] Figure 5 This is a flowchart illustrating the protection processing steps in one embodiment;

[0025] Figure 6A This is a flowchart illustrating the fault detection steps in one embodiment;

[0026] Figure 6B This is a schematic diagram showing the comparison between predicted state data and actual state data in one embodiment.

[0027] Figure 6C This is a schematic diagram illustrating the prediction of differential data in one embodiment;

[0028] Figure 7 This is a structural block diagram of a line under-range protection device in one embodiment;

[0029] Figure 8 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0032] In one exemplary embodiment, a line underrange protection method is provided, see [link to relevant documentation]. Figure 1A The method includes:

[0033] S110, when a fault is detected in the protected line, determines the zero-mode current component corresponding to the voltage and current data of the protected line.

[0034] The fault is either a sudden fault or another type of fault, which is not specified here.

[0035] Specifically, the process of determining the zero-mode current component corresponding to the voltage and current data of the protected line may include: converting the current in the voltage and current data through a phase-mode conversion matrix to obtain the zero-mode current component I0, i.e., the zero-mode current component. See also Figure 1B This is a schematic diagram showing the change in the amplitude of the zero-mode current component over time.

[0036] Of course, other methods can be used to determine the zero-mode current component, which are not limited here.

[0037] In practical scenarios, the voltage in the voltage and current data can be converted using a phase-mode conversion matrix to obtain the zero-mode component U0 of the voltage. Based on the zero-mode component U0 of the voltage and the zero-mode component I0 of the current, the inverse current wave of the zero-mode component can be calculated. The specific calculation formula is as follows:

[0038]

[0039] In the formula, It is the zero-mode impedance.

[0040] S120 decomposes the zero-mode current component into two preset sub-band signals and determines the instantaneous amplitude and instantaneous phase of each preset sub-band signal.

[0041] In one optional implementation, wavelet packet decomposition is first performed on the zero-mode current component, thereby uniformly dividing the signal bandwidth of the zero-mode current component into multiple equal-width sub-band signals. These multiple equal-width sub-band signals can represent the complete frequency band energy distribution from low to high frequencies. Then, two preset sub-band signals are selected from the multiple sub-band signals. and The frequencies corresponding to the two preset sub-band signals differ significantly; for example, the frequency difference is greater than a preset difference value. Therefore, one preset sub-band signal corresponds to a higher frequency, while the other preset sub-band signal corresponds to a lower frequency.

[0042] In one optional implementation, the instantaneous amplitude and instantaneous phase are determined using the following formula:

[0043]

[0044] In the formula, Preset sub-band signal The instantaneous amplitude, Preset sub-band signal The instantaneous amplitude, Preset sub-band signal The instantaneous phase, Preset sub-band signal The instantaneous phase, To The result obtained by performing the Hilbert transform To The result obtained by performing the Hilbert transform.

[0045] The above method can quickly and accurately calculate the instantaneous amplitude and instantaneous phase. Of course, other methods can also be used to determine the instantaneous amplitude and instantaneous phase, which are not limited here.

[0046] S130, determine the actual time difference between the two preset sub-frequency band signals based on the instantaneous amplitude values ​​corresponding to the two preset sub-frequency band signals respectively.

[0047] The actual time difference between the two preset sub-band signals. This reflects the actual difference between the two preset sub-band signals in the time dimension.

[0048] For example, the actual time difference between two preset sub-band signals is the time difference between the same positions in the waveforms corresponding to the two preset sub-band signals, such as the actual time difference between the troughs in the waveforms corresponding to the two preset sub-band signals, or the actual time difference between the peaks in the waveforms corresponding to the two preset sub-band signals.

[0049] S140, determine the theoretical time difference between the two preset sub-frequency band signals based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively.

[0050] The theoretical time difference between the two preset sub-band signals reflects the theoretical difference between the two preset sub-band signals in the time dimension.

[0051] There is no specific order between S130 and S140.

[0052] S150 performs protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference.

[0053] Understandably, under-range protection refers to protection devices operating within a range shorter than the entire length of the protected line. For example, the operating range of the protection device may be 80% to 90% of the total length of the protected line. This design ensures that the protection device operates only for faults within the line itself, and does not operate for external faults (such as faults in adjacent lines), thereby improving the selectivity of the protection.

[0054] The protection device can be a relay, an electric gate, or other protection device, and there is no limitation on it.

[0055] The under-range protection area refers to the operating range of the protection device. Implementing protection measures for the under-range protection area ensures selectivity and prevents malfunctions caused by external faults.

[0056] The aforementioned under-range protection method, upon detecting a fault in the protected line, determines the zero-mode current component corresponding to the voltage and current data of the protected line. This zero-mode current component is then decomposed to obtain two preset sub-frequency band signals. The actual time difference between the two preset sub-frequency band signals is determined based on their instantaneous amplitudes, and the theoretical time difference is determined based on their instantaneous phases. Finally, protection processing is applied to the under-range protection area of ​​the protected line based solely on the actual and theoretical time differences. This embodiment eliminates the need for wavefront identification, avoiding delays in protection action due to complex wavefront identification algorithms, and ensuring timely under-range protection. Furthermore, this embodiment does not require setting the propagation speed of each frequency component to a fixed value, thus avoiding errors introduced by setting the propagation speed to a fixed value and improving the accuracy of the protection action.

[0057] Based on the technical solutions provided in the above embodiments, an optional embodiment is provided, in which the actual time difference determination step in S130 is refined.

[0058] See Figure 2The detailed steps for determining the actual time difference include:

[0059] S210, for each preset sub-band signal, determine the occurrence time of the first peak in the preset sub-band signal based on the instantaneous amplitude corresponding to the preset sub-band signal.

[0060] The first peak is the first maximum value of the waveform.

[0061] Understandably, based on the instantaneous amplitude of the preset sub-band signal at each moment, the first maximum instantaneous amplitude is found, and the first maximum instantaneous amplitude is taken as the first peak, thereby determining the time when the first peak appears.

[0062] S220, determine the actual time difference between two preset sub-band signals based on the absolute value of the difference between the determined occurrence times.

[0063] That is, the absolute value of the difference between the times when the first peak of each of the two preset sub-band signals appears is taken as the actual time difference.

[0064] In this embodiment, the absolute value of the difference between the occurrence times of the first peak of each of the two preset sub-frequency band signals is taken as the actual time difference. It can be seen that this embodiment uses the first peak in the preset sub-frequency band signal as the reference point. The first peak is relatively easy to find and the search time is short. Therefore, the first peak can be found efficiently and accurately, thereby efficiently and accurately determining the actual time difference, and thus achieving efficient and accurate under-range protection.

[0065] Based on the technical solutions provided in the above embodiments, an optional embodiment is provided, in which the theoretical time difference determination step in S140 is refined.

[0066] See Figure 3A The detailed steps for determining the theoretical time difference include:

[0067] S310: For each preset sub-band signal, determine the instantaneous center frequency of the preset sub-band signal based on the instantaneous phase corresponding to the preset sub-band signal, and determine the theoretical wave velocity of the preset sub-band signal based on the instantaneous center frequency.

[0068] Specifically, the instantaneous phase corresponding to the preset sub-band signal can be differentiated to obtain the instantaneous center frequency of the preset sub-band signal. The specific differentiation formula is as follows:

[0069]

[0070] In the formula, Preset sub-band signal The instantaneous center frequency, Preset sub-band signal The instantaneous center frequency.

[0071] See Figure 3B Preset sub-band signal A schematic diagram of the instantaneous center frequency is shown in the image. Figure 3C Preset sub-band signal A schematic diagram of the instantaneous center frequency.

[0072] That is, using a preset sub-frequency band signal The preset sub-band signal can be determined by the instantaneous center frequency at each moment. Theoretical wave speed Using preset sub-frequency band signals The preset sub-band signal can be determined by the instantaneous center frequency at each moment. Theoretical wave speed .

[0073] S320 determines the theoretical time difference between two preset sub-band signals based on the determined theoretical wave velocities.

[0074] The theoretical time difference is calculated based on two theoretical wave velocities and the fault distance, using the following formula:

[0075]

[0076] In the formula, Where L is the theoretical time difference and L is the fault distance.

[0077] In this embodiment, based on the known relationship between phase and frequency, the instantaneous center frequency of the preset sub-band signal can be accurately calculated according to the instantaneous phase corresponding to the preset sub-band signal. Based on the instantaneous center frequency of the preset sub-band signal at each moment, the theoretical wave velocity of the preset sub-band signal can be accurately calculated. Based on the known relationship between distance, velocity, and time, the theoretical time difference can be accurately calculated according to the fault distance and the theoretical wave velocity, thereby achieving accurate under-range protection.

[0078] Based on the technical solutions provided in the above embodiments, an optional embodiment is provided, in which the theoretical wave velocity determination step in S310 is refined.

[0079] See Figure 4 The detailed steps for determining the theoretical wave velocity include:

[0080] S410 determines the unit inductance and unit capacitance at the frequency corresponding to the preset sub-band signal based on the instantaneous center frequency of the preset sub-band signal.

[0081] Here, unit inductance can be understood as inductance per unit length of line.

[0082] Here, unit capacitance can be understood as capacitance per unit length of line.

[0083] It is understandable that unit inductance and unit capacitance are factors affecting the instantaneous center frequency corresponding to the preset sub-band signal.

[0084] For example, a frequency-dependent line parameter model can be established based on the zero-mode dispersion principle, and the preset sub-band signal can be calculated using the line parameter model. Unit inductance at corresponding frequency and unit capacitance And calculate the preset sub-band signal Unit inductance at corresponding frequency and unit capacitance .

[0085] S420 determines the theoretical wave velocity of the preset sub-band signal based on the unit inductance and unit capacitance.

[0086] For example, the preset sub-band signal can be calculated using the following formula. Theoretical wave speed and preset sub-band signals Theoretical wave speed :

[0087]

[0088] Understandably, this embodiment utilizes the significant time difference characteristic generated by the difference in propagation speed between high-frequency and low-frequency components in dispersive lines to expand the discrimination margin of whether subsequent faults occur in the under-range protection area, thereby improving the protection range coverage and protection sensitivity.

[0089] In this embodiment, the unit inductance and unit capacitance at the corresponding frequency of the preset sub-band signal are determined based on the instantaneous center frequency of the preset sub-band signal. The unit inductance and unit capacitance together determine the propagation speed of the signal in the transmission line. Therefore, the theoretical wave speed of the preset sub-band signal can be accurately calculated using the unit inductance and unit capacitance at the corresponding frequency of the preset sub-band signal.

[0090] Based on the technical solutions provided in the above embodiments, an optional embodiment is provided, in which the protection processing steps in S150 are refined.

[0091] See Figure 5 The detailed protection process includes:

[0092] S510 initiates protection action for the under-range protection area of ​​the protected line when the actual time difference and theoretical time difference meet the preset conditions.

[0093] The preset conditions include that the actual time difference is less than the product of the theoretical time difference and a preset coefficient. These preset conditions can be expressed as: , This is the actual time difference. For the theoretical time difference, These are preset coefficients, such as confidence coefficients.

[0094] Understandably, if the actual time difference and the theoretical time difference meet the preset conditions, it indicates that the fault occurred within the under-range protection area of ​​the protected line, and therefore the protection action is activated.

[0095] One way to initiate a protection action is to send a trip signal to the protection device so that the protection device can perform a power-off process.

[0096] In real-world scenarios, if the actual time difference and the theoretical time difference do not meet the preset conditions, it indicates that the fault occurred outside the under-range protection area of ​​the protected line, and therefore the protection action is not initiated.

[0097] In this embodiment, based on whether the actual time difference and the theoretical time difference meet the preset conditions, it is known whether the fault occurs within the under-range protection area, thereby determining whether to perform protection action to ensure the selectivity of protection and avoid protection malfunction due to external faults.

[0098] Based on the technical solutions provided in the above embodiments, an optional embodiment is provided, in which the fault detection steps in S110 are refined.

[0099] See Figure 6A The detailed fault detection steps include:

[0100] S610 extracts the fundamental voltage signal from the voltage and current data of the protected line.

[0101] In practical scenarios, before executing S610, the voltage signal in the voltage and current data can be normalized and preprocessed to eliminate the influence of dimensions and ensure the stability of the data in subsequent processing.

[0102] The fundamental voltage signal is the core component of the periodic voltage signal, representing the lowest frequency component of the voltage signal. Its characteristics determine the basic waveform and energy distribution of the voltage signal.

[0103] The voltage signal can be input to a bandpass filter, which only allows the fundamental frequency to pass through, and the bandpass filter outputs the fundamental voltage signal.

[0104] S620 performs orthogonal decomposition on the fundamental voltage signal to obtain initial state data.

[0105] Understandably, the fundamental voltage signal is orthogonally decomposed to obtain two orthogonal components, which form the initial state data, as follows.

[0106]

[0107] Where A is the fundamental amplitude, φ is the fundamental phase angle, and x 1,k and x 2,k For two orthogonal components, x k This is the initial state data.

[0108] Understandably, by using orthogonal decomposition, the nonlinear state estimation problem can be transformed into a linear state estimation problem, thereby accurately estimating the dynamic changes of the fundamental component.

[0109] S630, perform state prediction based on initial state data to obtain at least one predicted state data.

[0110] State prediction, or state estimation, can be achieved using a Kalman filter.

[0111] Before state estimation, the parameters of the Kalman filter can be initialized, including the state transition matrix. Process noise covariance matrix Q, observation noise covariance matrix R, and observation matrix State transition matrix Set it to a second-order identity matrix.

[0112] For each two adjacent time points (the previous time point and the next time point), the predicted state data of the previous time point is multiplied by the state transition matrix to obtain the predicted state data of the next time point, thus achieving prior state estimation. The state transition matrix is ​​then... The prior error covariance matrix and state transition matrix of the previous time step transpose matrix Multiplying these three factors and summing the product with the process noise covariance matrix Q yields the prior error covariance matrix for the next time step, thus updating the prior error covariance matrix. This recursive estimation method yields predicted state data and prior error covariance matrices for multiple time steps.

[0113] The relevant calculation formulas are as follows:

[0114]

[0115]

[0116] In the formula, This is the predicted state data for the next time step. This is the predicted state data from the previous moment. Let be the prior error covariance matrix of the previous time step. Let be the prior error covariance matrix for the next time step.

[0117] The predicted state data at the first time step is the initial state data, and the prior error covariance matrix at the first time step is a preset matrix.

[0118] To ensure the accuracy of the prediction, the above state estimate can be corrected using actual state observation data (i.e., actual state data), thereby achieving a posterior state estimate. The specific formula is as follows:

[0119]

[0120] In the formula, Indicates the Kalman filter gain; Indicates to For the predicted state data of the next time step The predicted state data after posterior estimation is used to achieve the predicted state data for the next time step. Update; It is the actual state observation data at the next moment; For the prior error covariance matrix at the next time step The prior error covariance matrix after posterior estimation is used to obtain the prior error covariance matrix for the next time step. Update.

[0121] Understandably, at least one of the predicted state data in S630 is the predicted state data at each time step obtained through prior estimation.

[0122] S640, based on each predicted state data and the actual state data corresponding to the fundamental voltage signal, determine at least one predicted difference data.

[0123] Among them, actual state data refers to actual state observation data.

[0124] For example, the predicted difference between the predicted state data at time k and the actual state data at time k is calculated using the following formula:

[0125]

[0126] In the formula, This represents the actual state data at time k. The predicted difference data is for time k.

[0127] For each time point, a predicted difference data is obtained, and the predicted difference data from multiple time points form a difference sequence.

[0128] See Figure 6B This diagram illustrates the comparison between the predicted state data obtained through state estimation using Kalman filtering and the actual state data. (See also...) Figure 6C This is a schematic diagram of the predicted difference data at various times.

[0129] S650, if in at least one predicted difference data point there is at least one data point whose absolute value is greater than a preset difference threshold, it is determined that a fault has been detected in the protected line.

[0130] The preset difference threshold can be set using the following calculation formula:

[0131]

[0132] In the formula, THD is the preset difference threshold, and K b For safety reasons, Normal operating period The maximum value among the absolute values ​​of the predicted difference data.

[0133] As can be seen, in S650, if the absolute value of at least one predicted difference data in the difference sequence is greater than THD, then the protected line is considered to have a fault, and the fault type is a sudden fault.

[0134] In this embodiment, the fundamental voltage signal is orthogonally decomposed to obtain initial state data, thereby transforming the subsequent state estimation from a nonlinear problem into a linear one, improving the accuracy of the subsequent state estimation. State prediction is performed based on the initial state data to obtain at least one predicted state data. Then, based on each predicted state data and the actual state data corresponding to the fundamental voltage signal, at least one predicted difference data is determined. Based on at least one predicted difference data, a fault can be determined in the protected line. The complexity of the above fault detection method is reduced compared to the fault detection method in traditional single-ended protection technology, improving the efficiency of fault detection.

[0135] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0136] Based on the same inventive concept, this application also provides a line under-range protection device for implementing the line under-range protection method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more line under-range protection device embodiments provided below can be found in the limitations of the line under-range protection method described above, and will not be repeated here.

[0137] In one exemplary embodiment, such as Figure 7 As shown, a line under-range protection device is provided, comprising: a first determining module 710, a first decomposition module 720, a second determining module 730, a third determining module 740, and a protection processing module 750, wherein:

[0138] The first determining module 710 is used to determine the zero-mode current component corresponding to the voltage and current data of the protected line when a fault is detected in the protected line.

[0139] The first decomposition module 720 is used to decompose the zero-mode current component into two preset sub-frequency band signals and determine the instantaneous amplitude and instantaneous phase of each preset sub-frequency band signal.

[0140] The second determining module 730 is used to determine the actual time difference between the two preset sub-frequency band signals based on the instantaneous amplitude values ​​corresponding to the two preset sub-frequency band signals; and,

[0141] The third determining module 740 is used to determine the theoretical time difference between the two preset sub-frequency band signals based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively.

[0142] The protection processing module 750 is used to perform protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference.

[0143] In one embodiment, the second determining module is specifically used to: for each preset sub-frequency band signal, determine the occurrence time of the first peak in the preset sub-frequency band signal based on the instantaneous amplitude corresponding to the preset sub-frequency band signal; and determine the actual time difference between two preset sub-frequency band signals based on the absolute value of the difference between the determined occurrence times.

[0144] In one embodiment, the third determining module includes: a first determining unit, configured to determine the instantaneous center frequency of the preset sub-frequency band signal based on the instantaneous phase corresponding to the preset sub-frequency band signal for each preset sub-frequency band signal, and to determine the theoretical wave velocity of the preset sub-frequency band signal based on the instantaneous center frequency; and a second determining unit, configured to determine the theoretical time difference between two preset sub-frequency band signals based on the determined theoretical wave velocities.

[0145] In one embodiment, the first determining unit is specifically used to: determine the unit inductance and unit capacitance at the frequency corresponding to the preset sub-frequency band signal based on the instantaneous center frequency corresponding to the preset sub-frequency band signal; and determine the theoretical wave velocity of the preset sub-frequency band signal based on the unit inductance and unit capacitance.

[0146] In one embodiment, the protection processing module is specifically used to: initiate protection action for the under-range protection area of ​​the protected line when the actual time difference and the theoretical time difference meet preset conditions; wherein, the preset conditions include the actual time difference being less than the product of the theoretical time difference and a preset coefficient.

[0147] In one embodiment, the first determining module is specifically configured to: extract the fundamental voltage signal from the voltage and current data of the protected line; perform orthogonal decomposition on the fundamental voltage signal to obtain initial state data; perform state prediction based on the initial state data to obtain at least one predicted state data; determine at least one predicted difference data based on each predicted state data and the actual state data corresponding to the fundamental voltage signal; and determine that a fault has been detected in the protected line if at least one of the predicted difference data has an absolute value greater than a preset difference threshold.

[0148] Each module in the aforementioned under-range protection device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0149] In one exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 8 As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When executed by the processor, the computer program implements a line underrange protection method.

[0150] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0151] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the line underrange protection method described above.

[0152] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the line underrange protection method described in the above embodiments.

[0153] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the line underrange protection method described above.

[0154] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0156] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for line under-range protection, characterized in that, include: When a fault is detected in the protected line, the zero-mode current component corresponding to the voltage and current data of the protected line is determined. The zero-mode current component is decomposed to obtain two preset sub-frequency band signals, and the instantaneous amplitude and instantaneous phase corresponding to each preset sub-frequency band signal are determined. The actual time difference between the two preset sub-frequency band signals is determined based on the instantaneous amplitude values ​​corresponding to the two preset sub-frequency band signals respectively. as well as, The theoretical time difference between the two preset sub-frequency band signals is determined based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively. Based on the actual time difference and the theoretical time difference, the under-range protection area of ​​the protected line is protected.

2. The method according to claim 1, characterized in that, Determining the actual time difference between the two preset sub-frequency band signals based on their instantaneous amplitude values ​​includes: For each preset sub-frequency band signal, the occurrence time of the first peak in the preset sub-frequency band signal is determined according to the instantaneous amplitude corresponding to the preset sub-frequency band signal; The actual time difference between the two preset sub-frequency band signals is determined based on the absolute value of the difference between the determined occurrence times.

3. The method according to claim 1, characterized in that, The step of determining the theoretical time difference between the two preset sub-frequency band signals based on their respective instantaneous phases includes: For each preset sub-band signal, the instantaneous center frequency of the preset sub-band signal is determined according to the instantaneous phase corresponding to the preset sub-band signal, and the theoretical wave velocity of the preset sub-band signal is determined according to the instantaneous center frequency. Based on the determined theoretical wave velocities, the theoretical time difference between the two preset sub-band signals is determined.

4. The method according to claim 3, characterized in that, Determining the theoretical wave velocity of the preset sub-band signal based on the instantaneous center frequency includes: Based on the instantaneous center frequency corresponding to the preset sub-frequency band signal, determine the unit inductance and unit capacitance at the frequency corresponding to the preset sub-frequency band signal; The theoretical wave velocity of the preset sub-band signal is determined based on the unit inductance and the unit capacitance.

5. The method according to any one of claims 1 to 4, characterized in that, The step of performing protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference includes: When the actual time difference and the theoretical time difference meet the preset conditions, the protection action is initiated for the under-range protection area of ​​the protected line. The preset condition includes that the actual time difference is less than the product of the theoretical time difference and a preset coefficient.

6. The method according to any one of claims 1 to 4, characterized in that, The detection of a fault in the protected line includes: Extract the fundamental voltage signal from the voltage and current data of the protected line; The fundamental voltage signal is orthogonally decomposed to obtain initial state data; Based on the initial state data, state prediction is performed to obtain at least one predicted state data. Based on each predicted state data and the actual state data corresponding to the fundamental voltage signal, at least one predicted difference data is determined; If, among the at least one predicted difference data, there is at least one data point whose absolute value is greater than a preset difference threshold, it is determined that a fault has been detected in the protected line.

7. A line under-range protection device, characterized in that, include: The first determining module is used to determine the zero-mode current component corresponding to the voltage and current data of the protected line when a fault is detected in the protected line. The first decomposition module is used to decompose the zero-mode current component into two preset sub-frequency band signals, and to determine the instantaneous amplitude and instantaneous phase corresponding to each preset sub-frequency band signal. The second determining module is used to determine the actual time difference between the two preset sub-frequency band signals based on the instantaneous amplitude values ​​corresponding to the two preset sub-frequency band signals respectively. as well as, The third determining module is used to determine the theoretical time difference between the two preset sub-frequency band signals based on the instantaneous phases corresponding to the two preset sub-frequency band signals respectively; The protection processing module is used to perform protection processing on the under-range protection area of ​​the protected line based on the actual time difference and the theoretical time difference.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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