Distributed distribution transformer high-voltage side intelligent terminal fault identification method and system

Abstract

The application relates to the technical field of power distribution automation, and discloses a distributed distribution transformer high-voltage side intelligent terminal fault identification method and system. The method comprises the following steps: collecting three-phase current signals on the high-voltage side of a distribution transformer and preprocessing, extracting effective values of the three-phase currents to calculate a standard value and three-phase unbalance characteristic parameters, collecting switch state codes as state identifiers to determine a fault type in combination with the characteristic parameters, establishing a distribution loop topology relationship to verify a fault determination result, and generating an isolation control instruction to realize fault isolation and power supply recovery. The application solves the problems of long response delay, low fault positioning accuracy, lack of fine fault type identification and topology verification mechanism caused by centralized processing in the existing power distribution network fault detection system, and improves the accuracy of fault identification and the fault isolation response speed on the high-voltage side of the distribution transformer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution automation, and in particular to a distributed distribution transformer high-voltage side intelligent terminal fault identification method and system. BACKGROUND

[0002] As an important part of the power system, the distribution network undertakes the key task of distributing electric energy from the transmission network to the terminal user. The distribution transformer, as the core equipment of the distribution network, directly affects the power supply reliability and power quality. The traditional fault detection of the distribution network mainly relies on centralized fault indicators and manual line inspection. The centralized fault indicators determine the fault occurrence by monitoring the changes of line current and voltage, and the manual line inspection determines the fault location by on-site inspection. The power distribution automation system collects the operation data of the distribution equipment through the remote terminal unit and uploads them to the master station for centralized analysis and processing. The master station comprehensively determines the fault section according to the current and voltage data of multiple measuring points, and realizes fault isolation and power supply restoration by issuing control instructions. The distribution network has a complex topology and a large number of devices. The traditional centralized monitoring and control method has problems such as large communication delay, heavy processing load of the master station, and low fault positioning accuracy.

[0003] The existing technology has obvious deficiencies in fault identification of the high-voltage side of the distribution transformer. The centralized fault detection system relies on the centralized analysis and processing of the master station. When the scale of the distribution network expands, the master station needs to process a large amount of data, resulting in a sharp increase in calculation load. The delay and fault of the communication link will affect the timely transmission of fault information. The traditional fault indicator mainly detects the overcurrent and grounding signals of the line, and lacks fine identification ability for faults on the incoming line side, bus, and load side of the distribution transformer. The current information of a single measuring point cannot accurately distinguish whether the fault location is on the incoming line side, the outgoing bus, or the load side of the transformer. The fault determination relies on the setting of experience threshold values, and different capacity and load characteristics of the distribution transformer need to set criteria separately, increasing the configuration complexity. The fault isolation and power supply restoration decision of the centralized system relies on the control instructions issued by the master station, and the response time from fault detection to isolation control is long, affecting the power supply continuity of the non-fault area. SUMMARY

[0004] The present application provides a distributed distribution transformer high-voltage side intelligent terminal fault identification method and system, which solves the problems of long response delay, low fault positioning accuracy, lack of fine fault type identification, and topology verification mechanism in the existing distribution network fault detection system, and improves the accuracy of fault identification and the response speed of fault isolation of the high-voltage side of the distribution transformer.

[0005] In a first aspect, the present application provides a distributed distribution transformer high-voltage side intelligent terminal fault identification method, which comprises:

[0006] The three-phase current signal on the high-voltage side of the distribution transformer is collected, and the three-phase current signal is preprocessed to obtain the preprocessed current signal.

[0007] Extract the effective value of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current.

[0008] The status information of the high-voltage side switch of the distribution transformer is collected, the status information of the switch is encoded into a status identifier, and the fault type of the distribution transformer is determined by combining the three-phase current imbalance characteristic parameters.

[0009] Establish topological relationship data for multiple distribution transformers within the distribution loop, verify the determined fault type based on the topological relationship data, and confirm the fault determination result;

[0010] Based on the confirmed fault determination result, an isolation control command is generated, and the isolation control command is executed to achieve isolation of the faulty area and restoration of power supply to the non-faulty area.

[0011] Secondly, this application provides a distributed distribution transformer high-voltage side intelligent terminal fault identification system, the distributed distribution transformer high-voltage side intelligent terminal fault identification system comprising:

[0012] The processing module is used to acquire the three-phase current signal on the high-voltage side of the distribution transformer, perform signal preprocessing on the three-phase current signal, and obtain the preprocessed current signal.

[0013] The calculation module is used to extract the effective values ​​of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current.

[0014] The encoding module is used to collect the status information of the high-voltage side switch of the distribution transformer, encode the status information of the switch into a status identifier, and determine the fault type of the distribution transformer by combining the three-phase current imbalance characteristic parameters.

[0015] The verification module is used to establish topological relationship data of multiple distribution transformers within the distribution loop, verify the determined fault type based on the topological relationship data, and confirm the fault determination result.

[0016] The implementation module is used to generate isolation control instructions based on the confirmed fault determination results, and execute the isolation control instructions to realize the isolation of the fault area and the restoration of power supply to the non-fault area.

[0017] Thirdly, a distributed distribution transformer high-voltage side intelligent terminal fault identification device is provided, comprising: a memory and at least one processor, wherein the memory stores instructions; the at least one processor invokes the instructions in the memory to cause the distributed distribution transformer high-voltage side intelligent terminal fault identification device to execute the above-described distributed distribution transformer high-voltage side intelligent terminal fault identification method.

[0018] Fourthly, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium, which, when executed on a computer, cause the computer to perform the above-described method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal.

[0019] The technical solution provided in this application obtains a preprocessed current signal by acquiring the three-phase current signal of the high-voltage side of the distribution transformer and performing signal preprocessing. A multi-stage preprocessing method combining wavelet decomposition and Wiener filtering is used to simultaneously remove random noise and harmonic interference. Wavelet decomposition decomposes the signal into approximate coefficients and detail coefficients according to the frequency scale. A threshold function is used to denoise the high-frequency detail coefficients while preserving the main power frequency components. The Wiener filter achieves adaptive filtering in the frequency domain by designing a transfer function based on the ratio of the signal power spectral density to the noise power spectral density. This multi-stage preprocessing significantly improves the signal-to-noise ratio of the current signal. The per-unit value of each phase current is obtained by extracting the effective value of each phase current from the preprocessed current signal and comparing it with the historical current benchmark value. The per-unit value normalization method eliminates the influence of the difference in absolute current values ​​of distribution transformers with different capacities, enabling distribution transformers of various capacities to use a unified fault criterion. Based on the per-unit values ​​of each phase current, the characteristic parameter of three-phase current imbalance is calculated. Dividing the maximum per-unit current value by the intermediate per-unit current value quantitatively characterizes the degree of imbalance in the three-phase current distribution. When the three-phase load is symmetrical, this parameter is close to 1; when a single-phase grounding or open-circuit fault occurs, this parameter becomes significantly smaller. By collecting and encoding the status information of the high-voltage side switches of the distribution transformer into status identifiers, a mapping relationship between switch status combinations and fault-aware areas is established. The fault-aware area mapping table is queried based on the status identifiers to obtain the range of perceptible fault locations. The fault type is determined by combining the three-phase current imbalance characteristic parameters with the numerical distribution relationship of the per-unit values ​​of each phase current. This enables refined identification of incoming-side faults, busbar faults, and load-side faults. By establishing topological relationship data of multiple distribution transformers within the distribution loop, cross-verification is performed using the electrical propagation law of faults in the distribution loop. When the target distribution transformer is determined to be either an incoming-side fault or a load-side fault, it is checked whether all preceding distribution transformers are busbar faults and whether all subsequent distribution transformers are fault-free. If the single-point fault propagation law is met, the fault determination result is confirmed as correct. The topology verification mechanism effectively reduces the false judgment rate. Based on the confirmed fault determination result, isolation control commands are generated and fault area isolation and non-fault area power restoration are executed. The entire process is completed locally at the intelligent terminal on the high-voltage side of the distribution transformer without relying on centralized processing at the master station, significantly shortening the fault response time and improving the power supply reliability and self-healing capability of the distribution network.

[0020] This application applies wavelet decomposition and Wiener filtering algorithms for signal preprocessing in the specific field of distribution network fault diagnosis and self-healing control. The contribution of the algorithms to the scheme is reflected in the effective separation of the power frequency component and noise harmonic components of the current signal through multi-stage preprocessing, which significantly improves the accuracy of subsequent fault feature extraction. The per-unit value normalization algorithm eliminates the influence of distribution transformer capacity differences on fault criteria, enabling distributed intelligent terminals to use a unified criterion threshold. The calculation method of three-phase current imbalance characteristic parameters quantitatively characterizes the asymmetry of the three-phase current distribution by the ratio of the maximum current per-unit value to the intermediate current per-unit value, providing reliable characteristic parameters for fault type determination. Switch state coding... The code-and-fault-aware-area mapping algorithm establishes the correlation between switch state combinations and electrical location ranges. Combined with current imbalance characteristic parameters, it achieves fine-grained fault location. The distribution loop topology verification algorithm utilizes the propagation law of faults in the loop. By calculating the bus fault matching degree of the preceding distribution transformer fault type and the fault-free matching degree of the subsequent distribution transformer fault type, it cross-verifies the correctness of the single-point fault judgment result. The application of the algorithm enables the distributed intelligent terminal to have the ability of local fault identification, topology verification, and automatic isolation control. It can achieve rapid fault location and power supply restoration without relying on centralized processing at the master station, thus improving the overall intelligence level and fault response speed of the distribution network. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of an embodiment of the fault identification method for the high-voltage side intelligent terminal of distributed distribution transformers in this application.

[0023] Figure 2 This is a schematic diagram of one embodiment of the distributed distribution transformer high-voltage side intelligent terminal fault identification system in this application.

[0024] Figure 3 This is a schematic block diagram of the structure of the distributed distribution transformer high-voltage side intelligent terminal fault identification device in this embodiment of the invention. Detailed Implementation

[0025] This application provides a method and system for fault identification of a smart terminal on the high-voltage side of a distributed distribution transformer. The terms "first," "second," "third," "fourth," etc. (if present)," in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" or "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0026] For ease of understanding, the specific process of the embodiments of this application is described below. Please refer to [link / reference]. Figure 1 One embodiment of the fault identification method for the high-voltage side intelligent terminal of distributed distribution transformers in this application includes:

[0027] Step S101: Collect the three-phase current signal from the high-voltage side of the distribution transformer, perform signal preprocessing on the three-phase current signal, and obtain the preprocessed current signal.

[0028] Step S102: Extract the effective value of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current.

[0029] Step S103: Collect the status information of the high-voltage side switch of the distribution transformer, encode the status information of the switch into a status identifier, and determine the fault type of the distribution transformer by combining the three-phase current imbalance characteristic parameters.

[0030] Step S104: Establish topology data of multiple distribution transformers in the distribution loop, verify the determined fault type based on the topology data, and confirm the fault determination result.

[0031] Step S105: Generate isolation control commands based on the confirmed fault determination results, and execute the isolation control commands to realize the isolation of the faulty area and the restoration of power supply to the non-faulty area.

[0032] It is understood that the implementing entity of this application can be a distributed distribution transformer high-voltage side intelligent terminal fault identification system, or it can be a terminal or a server; the specific implementation is not limited here. This application's embodiment uses a server as an example for illustration.

[0033] Specifically, the intelligent terminal synchronously acquires the A-phase, B-phase, and C-phase current signals at the positions of the incoming switch, outgoing switch, and load switch via current transformers installed on the high-voltage side of the distribution transformer. A current transformer is an electromagnetic device that proportionally transforms a large current into a smaller current. Typically, it converts the kiloampere-level current on the high-voltage side into a standard 5-ampere or 1-ampere signal according to a specific transformation ratio for easy measurement. During the acquisition process, the three-phase current signals must be sampled simultaneously to ensure phase synchronization. The acquired raw three-phase current signals contain noise interference and harmonic components, therefore preprocessing is required. First, a wavelet basis is used to perform multi-level wavelet decomposition on the raw three-phase current signals. Wavelet decomposition is a time-frequency analysis method that decomposes the signal... To achieve multi-resolution signal analysis using wavelet coefficients at different frequency scales, approximation coefficients and multi-level detail coefficients are obtained after decomposition. The approximation coefficients represent the main low-frequency components of the signal, while the detail coefficients represent the high-frequency noise components. A threshold function is used to denoise the multi-level detail coefficients. This threshold function sets a threshold value, zeroing or shrinking detail coefficients with amplitudes smaller than that threshold to remove high-frequency noise. After denoising, the signal is reconstructed using inverse wavelet transform. The processed approximation and detail coefficients are then recombined according to the inverse process of wavelet decomposition to obtain the denoised current signal. This denoised current signal is then converted to the frequency domain using Fast Fourier Transform (FFT), an efficient algorithm for calculating Discrete Fourier Transform (DFT) to transform a time-domain signal into a frequency-domain signal. Represented as the superposition of different frequency components, the Wiener filter's frequency domain transfer function is applied for filtering in the frequency domain. The Wiener filter is an optimal linear filter based on the minimum mean square error criterion. Its frequency domain transfer function is designed according to the ratio of signal power spectral density to noise power spectral density, attenuating different frequency components to varying degrees. After filtering, the signal is converted back to the time domain using an inverse fast Fourier transform, yielding the final preprocessed current signal. This preprocessing removes both random noise and harmonic interference. The preprocessed current signal then undergoes effective value extraction. The effective current value refers to the value required for the thermal effect of alternating current within one cycle to be equivalent to that of direct current. This is achieved by averaging the squares of the instantaneous current values ​​within one cycle and then... The method involves obtaining the effective values ​​of phase A, phase B, and phase C currents, respectively. Then, the reference current values ​​for phase A, phase B, and phase C before the fault are read from the historical current reference value storage queue. This queue is a data structure that stores the effective values ​​of each phase current during normal operation in chronological order. The queue stores the steady-state current values ​​for a period of time before the fault as a reference. The per-unit value of phase A current is obtained by dividing the effective value of phase A current by the reference value of phase A current; the per-unit value of phase B current is obtained by dividing the effective value of phase B current by the reference value of phase B current; and the per-unit value of phase C current is obtained by dividing the effective value of phase C current by the reference value of phase C current. The per-unit value is a normalized relative value representation method.The influence of absolute numerical values ​​is eliminated by comparing them with a benchmark value, facilitating unified judgment of distribution transformers with different capacities. The maximum and intermediate per-unit current values ​​are selected from the per-unit current values ​​of phase A, phase B, and phase C. Dividing the maximum and intermediate per-unit current values ​​yields a three-phase current imbalance characteristic parameter. This parameter reflects the degree of imbalance in the three-phase current distribution. When the three-phase load is symmetrical, this parameter is close to 1; when a single-phase grounding or open-circuit fault occurs, this parameter increases significantly. The status of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer is collected. The open state is defined as 0 (switch open), and the closed state is defined as 1 (switch closed). Based on the status of the three switches... The combination of states encodes the switch state triplet to obtain a state identifier. The state identifier is a three-bit binary code, with the most significant bit representing the state of the incoming switch, outgoing switch, and load switch, respectively. The power supply direction identifier of the distribution loop containing the distribution transformer is obtained, indicating whether electrical energy flows from the incoming side to the load side or from the other end. Based on the state identifier, the fault-aware area mapping table is consulted to obtain the range of detectable fault locations. This pre-established lookup table records the electrical location range of faults that can be detected by the intelligent terminal corresponding to different switch state combinations. The three-phase current imbalance characteristic parameters are compared with preset thresholds, which are based on a large number of historical faults. The criteria obtained from data statistical analysis indicate that when the three-phase current imbalance characteristic parameter exceeds a preset threshold, it indicates an abnormality in the three-phase current distribution. Combining the numerical distribution relationship of the per-unit current values ​​of each phase, the fault type of the distribution transformer is determined within the perceptible fault location range. The numerical distribution relationship includes a significant decrease in the per-unit current value of a certain phase, indicating a phase open-circuit fault; and a significant increase in the per-unit current value of one or two phases, indicating a short-circuit fault. A loop topology state matrix is ​​constructed according to the connection sequence of the distribution transformers within the distribution loop. This loop topology state matrix is ​​a one-dimensional or two-dimensional data structure. Each element in the matrix corresponds to the location of a distribution transformer in the distribution loop, and the element value records the fault type identifier of the distribution transformer at that location. A one-dimensional... The power transmission direction matrix records the power transmission direction identifiers of distribution transformers at each location. Target distribution transformers with fault types of either incoming-side or load-side faults are extracted from the loop topology state matrix. An incoming-side fault refers to a fault point located between the incoming switch and the power source of the distribution transformer; a load-side fault refers to a fault point located between the load switch and the load of the distribution transformer. The sets of fault types for preceding and succeeding distribution transformers are obtained. Preceding distribution transformers refer to those upstream of the target distribution transformer in the distribution loop, and succeeding distribution transformers refer to those downstream of the target distribution transformer. The power transmission direction identifier value of the target distribution transformer is read from the power transmission direction matrix.Based on the power transmission direction indicator value, the location range of the preceding and following distribution transformer fault type sets is determined. For the preceding distribution transformer fault type set, a bus fault type matching degree is calculated. A bus fault refers to a fault on the outgoing bus of the distribution transformer. The matching degree calculation is obtained by ratioing the number of bus fault types in the set to the total number of elements in the set. For the following distribution transformer fault type set, a fault-free type matching degree is calculated by ratioing the number of fault-free types in the set to the total number of elements in the set. When both the preceding and following matching degree values ​​are equal to 1, it indicates that all distribution transformers upstream of the target distribution transformer have detected bus faults, while all distribution transformers downstream have detected bus faults. No faults were detected in any of the transformers, which conforms to the electrical propagation law of single-point faults. The loop status identifier value at the corresponding position in the loop topology state matrix is ​​set to a single-point fault locating state. If the preceding or following matching degree value is less than 1, it indicates a situation that does not conform to the single-point fault propagation law, and the loop status identifier value is set to a multi-point fault pending verification state. The loop status identifier value is read from the loop topology state matrix. When the loop status identifier value is a single-point fault locating state, the location index and fault type of the faulty distribution transformer are extracted. The location index is the position number of the distribution transformer in the loop topology state matrix. Based on the fault type, the target disconnect switch combination is obtained by querying the fault isolation strategy mapping table. The fault isolation strategy mapping table is a pre-planned table. The reference table records the switch combinations that need to be tripped for different fault types. A switch tripping command sequence is generated based on the target isolating switch combination. This sequence consists of a series of switch control commands arranged in the order of operation. The switch tripping command sequence is then sent to the high-voltage side switch actuator of the corresponding distribution transformer via a communication link. The communication link is the data transmission channel between the intelligent terminal and the switch actuator. The switches in the target isolating switch combination are controlled to perform tripping operations to isolate the fault area. From the loop topology state matrix, a set of healthy distribution transformers located in the same distribution loop as the faulty distribution transformer and in the non-fault area is identified. This set of healthy distribution transformers includes all distribution transformers with a fault-free fault type. The healthy distribution transformers... Topology analysis is performed on the power supply paths of each distribution transformer in the power distribution unit set. This analysis involves traversing the connections of the distribution loop to find available power supply paths from the backup power source to the viable distribution transformers. A sequence of switch closing commands is generated to control the switches on the backup power supply paths to perform closing operations, thus restoring power to the viable distribution transformer set. In a certain distribution loop, five distribution transformers are connected sequentially. When distribution transformer number 3 detects the status indicators of the incoming switch closing, the outgoing switch opening, and the load switch closing, it synchronously acquires the A-phase current signal waveform data through the current transformer. A 5-level wavelet decomposition is performed using a db4 wavelet basis. After decomposition, the detail coefficients from level 3 to level 5 are processed using a soft threshold function, with the threshold set to three times the standard deviation of each level's detail coefficient.The processed detail coefficients and approximation coefficients are reconstructed using inverse wavelet transform. The reconstructed denoised current signal is then converted to the frequency domain using a 2048-point Fast Fourier Transform. In the frequency domain, the transfer function of a Wiener filter is applied. This transfer function is designed based on the ratio of signal power spectral density to noise power spectral density, preserving the 50 Hz fundamental wave and its integer multiples of harmonics while attenuating other frequency components. After filtering, the signal is converted back to the time domain using an inverse Fast Fourier Transform to obtain the preprocessed current signal. The effective value of the preprocessed current signal is extracted. The effective value of the A-phase current is obtained by summing the squares of the sampled data points within 20 milliseconds of one power frequency cycle, dividing by the number of sampled points, and then taking the square root. The A-phase reference current value within 10 seconds before the fault occurrence is read from the historical current reference value storage queue. The average effective value of phase A current over 10 seconds is used to obtain the phase A current per unit value. Dividing the effective value of phase A current by the phase A reference current value yields the phase A current per unit value. The same method is used to obtain the phase B and phase C current per unit values. From these three phase current per unit values, the maximum and intermediate current per unit values ​​are selected. Dividing the maximum current per unit value by the intermediate current per unit value yields the three-phase current imbalance characteristic parameter. This parameter is compared with a preset threshold of 1.5. It is found that the three-phase current imbalance characteristic parameter is greater than the preset threshold. Combined with the numerical distribution relationship where the phase A current per unit value significantly decreases to 0.1 while the phase B and phase C current per unit values ​​remain above 0.95, the fault-aware area mapping table is consulted based on the status identifier. The perceptible fault location range corresponding to this switch status combination includes... Based on the current per-unit value distribution relationship in the line-side and busbar areas, the fault type is determined to be an A-phase open-circuit fault on the incoming line side. A loop topology state matrix is ​​constructed to record the fault types of the five distribution transformers. Among them, distribution transformer No. 3 is recorded as an incoming line side fault, distribution transformers No. 1 and No. 2 are recorded as busbar faults, and distribution transformers No. 4 and No. 5 are recorded as fault-free. The power supply direction identifier of distribution transformer No. 3 is read from the power supply direction matrix as positive power supply, determining that the preceding distribution transformers are No. 1 and No. 2, and the following distribution transformers are No. 4 and No. 5. The matching degree is calculated for the fault type set of the preceding distribution transformers. The set contains 2 busbar fault type elements, and the total number of elements in the set is 2. The ratio calculation yields a matching degree of 1 for the preceding set. The matching degree for the fault type set of the following distribution transformers is calculated. The matching degree is calculated. The set contains two fault-free elements, and the total number of elements in the set is 2. The ratio operation yields a subsequent matching degree of 1. Since both the preceding and subsequent matching degree values ​​are equal to 1, the loop status identifier is set to a single-point fault location state. The loop status identifier is read from the loop topology state matrix as a single-point fault location state. The location index of distribution transformer No. 3 is extracted as 3, and the fault type is incoming A-phase open circuit fault. Based on the fault type, the fault isolation strategy mapping table is queried, and the target disconnect switch combination is obtained, which includes the incoming switch of distribution transformer No. 3 and the outgoing switch of distribution transformer No. 2. A switch opening command sequence is generated, first controlling the opening of the incoming switch of distribution transformer No. 3, and then controlling the opening of the outgoing switch of distribution transformer No. 2.The fault area was isolated, and the complete set of distribution transformers, including transformers 4 and 5, was identified. Topology analysis of the power supply path revealed a backup power source at the other end of the distribution loop, accessible via the tie switch of transformer 5. A switch-closing command sequence was generated, controlling the tie switch to perform the closing operation, thus restoring power to transformers 4 and 5.

[0034] In one specific embodiment, three-phase current signals from the high-voltage side of the distribution transformer are acquired, and the three-phase current signals are preprocessed to obtain preprocessed current signals, including:

[0035] The original three-phase current signals are obtained by synchronously acquiring the A-phase current signal, B-phase current signal, and C-phase current signal at the positions of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer using current transformers.

[0036] The original three-phase current signal is decomposed into multiple wavelet bases to obtain approximation coefficients and multiple detail coefficients. The multiple detail coefficients are then denoised using a threshold function. The denoised current signal is then reconstructed by inverse wavelet transform.

[0037] The denoised current signal is converted to the frequency domain by Fast Fourier Transform, filtered by the frequency domain transfer function of the Wiener filter, and then converted to the time domain by Inverse Fast Fourier Transform to obtain the preprocessed current signal.

[0038] Specifically, current transformers are installed at the incoming switch, outgoing switch, and load switch positions on the high-voltage side of the distribution transformer. These current transformers convert the large high-voltage current into a smaller current signal using a fixed transformation ratio. For example, a 400-ampere primary current is converted to a 5-ampere secondary current using an 80:1 transformation ratio. The intelligent terminal synchronously acquires the A-phase, B-phase, and C-phase current signals output from the current transformers at these three locations via an analog-to-digital converter. Synchronous acquisition means sampling the three-phase current signals simultaneously, with a sampling frequency set to 10,000 sampling points per second. Each 50 Hz power frequency cycle corresponds to 200 sampling points within 20 milliseconds. The acquired raw three-phase current signals contain random noise. To mitigate harmonic interference, the original three-phase current signal is decomposed using a multi-level wavelet basis. A wavelet basis is a basis function with time-frequency localization properties. The db4 wavelet basis, with its symmetry, is suitable for power signal analysis. Multi-level wavelet decomposition decomposes the signal into approximation coefficients and detail coefficients according to different frequency scales. Approximation coefficients represent the low-frequency component of the signal, i.e., the main power frequency component, while detail coefficients represent the high-frequency component, i.e., noise and harmonic components. Taking the A-phase current signal as an example, a 5-level wavelet decomposition is performed. The first level decomposition divides the signal into approximation coefficients in the frequency range of 0 to 2500 Hz and detail coefficients in the frequency range of 2500 to 5000 Hz. This decomposition continues until the fifth level, ultimately obtaining the fifth-level approximation coefficients and five sets of detail coefficients from the first to the fifth level. The multi-level detail coefficients are then further refined. The coefficients are denoised using a threshold function. The threshold function sets coefficients with amplitudes less than the threshold to zero or shrinks them. A soft threshold function subtracts the threshold from coefficients greater than the threshold while retaining their sign. The threshold is set to three times the standard deviation of the detail coefficients at each level. The denoised detail coefficients and the fifth-level approximation coefficients are reconstructed using an inverse wavelet transform. The inverse wavelet transform is the reverse process of wavelet decomposition. The approximation coefficients and detail coefficients at each level are weighted and summed according to wavelet basis functions to reconstruct a time-domain signal, ultimately yielding a denoised current signal. This denoised current signal is then converted to the frequency domain using a fast Fourier transform. The fast Fourier transform decomposes the time-domain signal into a superposition of sine and cosine components of different frequencies, resulting in a frequency-domain signal. Each frequency point in the frequency-domain signal corresponds to a... Complex values, where the modulus of a complex number represents the amplitude of a frequency component, are used for filtering in the frequency domain. The Wiener filter's frequency transfer function is designed based on the ratio of the signal power spectral density to the noise power spectral density. The signal power spectral density is obtained by squaring the frequency domain amplitude of the denoised current signal. The Wiener filter's transfer function approaches 1 at frequencies with high signal power spectral density, preserving the frequency component, and approaches 0 at frequencies with high noise power spectral density, suppressing the frequency component. The filtered frequency domain signal is obtained by multiplying the complex value of each frequency point of the frequency domain signal by the corresponding transfer function value. This filtered frequency domain signal is then converted back to the time domain using an inverse fast Fourier transform (IFFT), which is the inverse process of the fast Fourier transform.The frequency components of the frequency domain signal are synthesized into a time domain signal according to their corresponding amplitude and phase to obtain a preprocessed current signal. The position of the incoming switch on the high-voltage side of the distribution transformer detects an output of 5 amps from the A-phase current transformer, corresponding to a primary current of 400 amps. The original A-phase current signal with 200 sampling points is acquired within one power frequency cycle (20 milliseconds) using an analog-to-digital converter. A 5-level wavelet decomposition of the original A-phase current signal is performed using a db4 wavelet basis. The first level of decomposition halves the number of sampling points from 200 to 100, resulting in 100 approximation coefficients for the first level and... The first layer has 100 detail coefficients. The second layer decomposes by halving the 100 approximation coefficients in the first layer to 50. This process is repeated up to the fifth layer, yielding 6 approximation coefficients for the fifth layer and detail coefficients for each layer. The standard deviation of the first layer detail coefficients is calculated by summing the squares of the 100 detail coefficients, dividing by 100, and then taking the square root. The threshold is set to three times the standard deviation. Coefficients in the first layer with amplitudes less than the threshold are set to zero, while coefficients with amplitudes greater than the threshold are subtracted from the threshold and their signs are retained. The same method is used to calculate the thresholds for detail coefficients from the second to the fifth layer for denoising. The denoised fifth layer approximation coefficients are then compared with the... The layer detail coefficients are reconstructed using inverse wavelet transform. The 5th-layer approximation coefficients are upsampled and interpolated, then convolved with the denoised 5th-layer detail coefficients and added to reconstruct the 4th-layer approximation coefficients. This reconstruction continues until the 1st layer, ultimately resulting in a denoised current signal with 200 sampling points. A 256-point Fast Fourier Transform is performed on this denoised current signal, padding the remaining 56 sampling points with zeros. The resulting frequency domain data has 128 frequency points. The power spectral density of the denoised current signal is calculated, and the amplitudes at these 128 frequency points are squared. The Wiener filter's transmission... The transfer function at each frequency point is equal to the signal power spectral density divided by the sum of the signal power spectral density and the noise power spectral density. Near 50 Hz, the transfer function value is close to 1, preserving the power frequency component. In the high-frequency region far from 50 Hz, the transfer function value is close to 0, suppressing high-frequency noise. The complex values ​​of the 128 frequency points of the frequency domain signal are multiplied by their corresponding transfer function values ​​to obtain the filtered frequency domain signal. An inverse Fast Fourier Transform is performed on the filtered 128 frequency points to obtain a time-domain signal with 256 sampling points. The first 200 sampling points are used as the preprocessed current signal.

[0039] In one specific embodiment, the effective values ​​of each phase current in the preprocessed current signal are extracted, and the ratio of the current effective value of each phase current to the corresponding reference current value is calculated to obtain the per-unit value of each phase current. Based on the per-unit value of each phase current, the three-phase current imbalance characteristic parameters are calculated, including:

[0040] The preprocessed current signal is subjected to effective value extraction processing to obtain the effective values ​​of phase A current, phase B current and phase C current respectively;

[0041] Read the A-phase reference current value, B-phase reference current value, and C-phase reference current value before the fault occurred from the historical current reference value storage queue. Divide the effective value of the A-phase current by the A-phase reference current value to obtain the per-unit value of the A-phase current. Divide the effective value of the B-phase current by the B-phase reference current value to obtain the per-unit value of the B-phase current. Divide the effective value of the C-phase current by the C-phase reference current value to obtain the per-unit value of the C-phase current.

[0042] The maximum and intermediate current per-unit values ​​are selected from the current per-unit values ​​of phase A, phase B, and phase C. The maximum current per-unit value is divided by the intermediate current per-unit value to obtain the characteristic parameters of the three-phase current imbalance.

[0043] Specifically, the preprocessed current signal undergoes RMS value extraction. The RMS value is the value required for the thermal effect of the AC current within one cycle to be equivalent to that of the DC current. The calculation method involves squaring the instantaneous current values ​​within one power frequency cycle, summing the results, dividing by the number of sampling points, and then taking the square root. The intelligent terminal segments the preprocessed current signal according to the power frequency cycle, with each power frequency cycle corresponding to a 20-millisecond duration at 50 Hz, corresponding to 200 sampling points at the sampling frequency. The instantaneous current values ​​of these 200 sampling points are squared and summed, and the summation is divided by 200 to obtain the average value. The square root of the average value is then used to obtain the RMS value of phase A current for that power frequency cycle. The RMS values ​​of phase B current and phase C current are calculated using the same method. Historical current reference values ​​are stored... The current storage queue is a first-in, first-out (FIFO) data structure that stores the effective values ​​of each phase current during normal operation of the distribution transformer in chronological order. The queue length is set to store current data within the most recent period. When a fault trigger signal is detected, the intelligent terminal reads the A-phase reference current value, B-phase reference current value, and C-phase reference current value before the fault from the historical current reference value storage queue. The reference current value is selected as the steady-state current value within a certain time window before the fault. The currently detected effective value of the A-phase current is divided by the A-phase reference current value read from the queue to obtain the per-unit value of the A-phase current. The per-unit value is a normalized representation method that eliminates the influence of absolute numerical magnitude by comparing it with the reference value, allowing distribution transformers of different capacities to use different values. A unified criterion is used: dividing the effective value of phase B current by the reference value of phase B current yields the per-unit value of phase B current; dividing the effective value of phase C current by the reference value of phase C current yields the per-unit value of phase C current. The per-unit values ​​of the three-phase current reflect the change factor of each phase current relative to normal operating conditions. The per-unit values ​​of phase A, phase B, and phase C current are compared and sorted, and the largest per-unit value and the middle per-unit value are selected. Dividing the largest per-unit value by the middle per-unit value yields the three-phase current imbalance characteristic parameter. This parameter reflects the degree of imbalance in the three-phase current distribution. When the three-phase load is perfectly symmetrical, the per-unit values ​​of the three-phase current are equal. The maximum per-unit value and the middle per-unit value are then compared. The ratio of the per-unit values ​​is close to 1. When a single-phase ground fault or open-circuit fault occurs, the difference between the current of a certain phase and the currents of the other two phases increases significantly. The ratio of the maximum per-unit current to the intermediate per-unit current deviates significantly from 1. The intelligent terminal on the high-voltage side of the distribution transformer extracts the effective value of the pre-processed A-phase current signal at the incoming switch position. The pre-processed signal contains 200 sampling points for one power frequency cycle. The instantaneous current values ​​of these 200 sampling points are squared respectively. The square of the instantaneous value of the first sampling point is added to the square of the instantaneous value of the second sampling point, and so on, up to the square of the instantaneous value of the 200th sampling point. The sum is divided by 200 to obtain the average value. The square root of the average value is used to obtain the effective value of the A-phase current. The effective values ​​of the B-phase current and the C-phase current are obtained in the same way.The historical current reference value storage queue stores the effective values ​​of each phase current for each power frequency cycle within the most recent 10 seconds before the fault occurred. The queue contains data for 500 power frequency cycles. When a change in switch state is detected and fault judgment is triggered, the effective values ​​of each phase current during the steady-state period before the last power frequency cycle are read from the queue as reference values. The effective value of phase A current detected at the time of the fault is divided by the reference value of phase A current read from the queue to obtain the per-unit value of phase A current. Assuming that the effective value of phase A current drops significantly, the per-unit value of phase A current is less than 1. The effective value of phase B current is divided by the reference value of phase B current to obtain the per-unit value of phase B current close to 1. The effective value of phase C current is divided by the reference value of phase C current to obtain the per-unit value of phase C current. The value is close to 1. Comparing the per-unit values ​​of the three-phase currents, the per-unit values ​​of phase B and phase C are close in value and greater than the per-unit value of phase A. The maximum per-unit current value is the larger of the two phase values, and the intermediate per-unit current value is the smaller of the two phase values. Dividing the maximum per-unit current value by the intermediate per-unit current value, since their values ​​are close, results in a ratio close to 1, indicating that the current distribution in phases B and C is balanced. However, the per-unit value of phase A current deviates significantly from both the maximum and intermediate per-unit values. The ratio obtained by dividing the maximum per-unit current value by the phase A current value is significantly greater than 1. This ratio, as a characteristic parameter of three-phase current imbalance, reflects the degree of three-phase imbalance caused by the abnormal decrease in phase A current.

[0044] In one specific embodiment, the status information of the high-voltage side switch of the distribution transformer is collected, the status information of the switch is encoded into a status identifier, and the fault type of the distribution transformer is determined by combining the three-phase current imbalance characteristic parameters, including:

[0045] The status of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer is collected. The open state is defined as 0 and the closed state is defined as 1. The status identifier is obtained by encoding the switch status triplet based on the combination of the three switch statuses.

[0046] Obtain the power supply direction identifier of the distribution loop where the distribution transformer is located, and query the fault-sensible area mapping table based on the status identifier to obtain the range of the perceptible fault location.

[0047] The three-phase current imbalance characteristic parameters are compared with preset thresholds. When the three-phase current imbalance characteristic parameters are greater than the preset thresholds, the fault type of the distribution transformer is determined within the perceptible fault location range by combining the numerical distribution relationship of the per-unit values ​​of each phase current.

[0048] Specifically, the intelligent terminal collects the status of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer through a digital input interface. The switch status signals are output through auxiliary contacts. When the switch is open (corresponding to an open state), the auxiliary contact outputs a low-level signal (defined as 0). When the switch is closed (corresponding to a closed state), the auxiliary contact outputs a high-level signal (defined as 1). The statuses of the three switches are combined into a switch status triplet in the order of incoming switch, outgoing switch, and load switch. This triplet is then binary-encoded to obtain a status identifier, which is a three-bit binary number. The highest bit represents the incoming switch status, the middle bit represents the outgoing switch status, and the lowest bit represents the load switch status. When the incoming switch is closed, the outgoing switch is open, and the load switch is closed, the status triplet is 101, which is converted to decimal as 5, serving as the status identifier. The power supply direction identifier of the distribution loop records the direction of energy flow. Forward power supply indicates that energy flows from the incoming side of the distribution transformer to the load side, and reverse power supply indicates that energy flows from the outgoing side of the distribution transformer to the load side. The power supply direction identifier is stored in the configuration parameters of the distribution transformer. The intelligent terminal reads the power supply direction identifier and queries the fault-detectable area mapping table according to the status identifier. The fault-detectable area mapping table is a pre-established lookup table. Each row in the table records the detectable fault location range corresponding to a status identifier. The detectable fault location range corresponding to status identifier 5 includes the incoming line side and busbar area. The detectable fault location range corresponding to status identifier 7 includes the incoming line side, busbar area, and load side. The intelligent terminal finds the corresponding row in the mapping table according to the status identifier, reads the detectable fault location range field of that row to obtain the electrical location range of the fault that the intelligent terminal can detect under the current switch status combination, and compares the calculated three-phase current imbalance characteristic parameter with the preset threshold. The preset threshold is determined based on statistical analysis of a large amount of historical fault data. When the three-phase load is completely symmetrical, the three-phase current imbalance characteristic parameter is close to 1. When a fault occurs, the parameter increases significantly. The preset threshold is set to 1.5. When the three-phase current imbalance characteristic parameter exceeds a preset threshold, an abnormality in the three-phase current distribution is determined. The fault type is then determined by combining the numerical distribution relationship of the per-unit current values ​​of each phase. This numerical distribution relationship includes different modes such as a one-phase current per-unit value being significantly less than the other two phases, a one-phase current per-unit value being significantly greater than the other two phases, and two phases having per-unit current values ​​significantly less than the other phase. When the per-unit current value of phase A is significantly less than that of phases B and C, it is determined to be a phase A open-circuit fault. When the per-unit current value of phase A is significantly greater than that of phases B and C, it is determined to be a phase A ground fault. The fault type of the distribution transformer is determined within the perceptible fault location range. When the perceptible fault location range includes both the incoming side and the busbar area, the fault location is determined by combining the current per-unit value distribution relationship. The intelligent terminal on the high-voltage side of the distribution transformer collects a high-level signal output from the auxiliary contact of the incoming switch through the digital input interface, recording the incoming switch status as 1. It collects a low-level signal output from the auxiliary contact of the outgoing switch, recording the outgoing switch status as 0. It collects a high-level signal output from the auxiliary contact of the load switch, recording the load switch status as 1. The switch status triplets, arranged sequentially as 101, are binary encoded. The highest bit (1) represents the incoming switch closed, the middle bit (0) represents the outgoing switch open, and the lowest bit (1) represents the load switch closed. The binary number 101 is converted to the decimal value 5 as the status identifier. The power supply direction identifier (positive power supply) is read from the distribution transformer's configuration parameter storage area. Based on status identifier 5, the fault-aware area mapping table is queried. The row corresponding to status identifier 5 in the mapping table shows the perceptible fault location range as the incoming side and busbar area. The perceptible fault location range field of this row is read, and the calculated... The obtained three-phase current imbalance characteristic parameters are compared with a preset threshold of 1.5. If the three-phase current imbalance characteristic parameters are greater than the preset threshold, an abnormality in the three-phase current distribution is determined. The per-unit values ​​of phase A, phase B, and phase C currents are read. The per-unit value of phase A current is significantly smaller than that of phases B and C currents. The per-unit values ​​of phase B current and phase C currents are close, indicating an A-phase open-circuit fault. Considering the tripped state of the outgoing switch within the detectable fault location range, the fault type is determined to be an incoming-side A-phase open-circuit fault. When the outgoing switch is closed, the fault type is determined to be a busbar A-phase open-circuit fault.

[0049] In one specific embodiment, topological relationship data of multiple distribution transformers within a distribution loop is established. The determined fault type is verified based on this topological relationship data to confirm the fault determination result, including:

[0050] A loop topology state matrix is ​​constructed according to the connection sequence of the distribution transformers in the distribution loop. The loop topology state matrix records the fault type of the distribution transformer at each location. A power transmission direction matrix of the same dimension is constructed to record the power transmission direction identifier of the distribution transformer at each location.

[0051] Extract the target distribution transformer with fault type of incoming side fault or load side fault from the loop topology state matrix, and obtain the set of fault types of the preceding distribution transformer and the set of fault types of the following distribution transformer from the target distribution transformer.

[0052] Check whether the fault type set of the preceding distribution transformer is entirely a bus fault, and check whether the fault type set of the following distribution transformer is entirely without fault. When all checks pass, the fault determination result is confirmed to be correct.

[0053] Specifically, the distribution loop contains multiple distribution transformers. A loop topology state matrix is ​​constructed according to their physical connection order within the loop. This matrix is ​​a one-dimensional array structure, where each element corresponds to the position of a distribution transformer in the loop. The element's index indicates the transformer's position number within the loop, and the element's value records the fault type identifier for that transformer. Fault type identifiers include no fault, incoming-side fault, bus fault, and load-side fault. A power transmission direction matrix of the same dimension is constructed to record the power transmission direction identifiers for each distribution transformer at each position. This matrix has the same array length as the loop topology state matrix, and each element records the power transmission direction and identifier for the corresponding distribution transformer at that position. This includes both forward and reverse power transmission. Elements are traversed one by one from the loop topology state matrix to extract distribution transformers with fault types of either incoming-side or load-side faults as target distribution transformers. The position index of the target distribution transformer in the matrix is ​​recorded. The sets of fault types for preceding and following distribution transformers are obtained. Preceding distribution transformers are those upstream of the target distribution transformer in the distribution loop, and following distribution transformers are those downstream of the target distribution transformer. The power transmission direction identifier of the target distribution transformer is read from the power transmission direction matrix. When the power transmission direction identifier is forward power transmission, the preceding distribution transformer is any distribution transformer whose position index is less than that of the target distribution transformer. The subsequent distribution transformers are all distribution transformers whose location index is greater than the target distribution transformer's location index. The fault type identifiers of the corresponding positions of the preceding distribution transformers are read from the loop topology state matrix, and these fault type identifiers are combined into a preceding distribution transformer fault type set. Similarly, the fault type identifiers of the corresponding positions of the subsequent distribution transformers are read from the loop topology state matrix, and these fault type identifiers are combined into a subsequent distribution transformer fault type set. Each element in the preceding distribution transformer fault type set is checked to determine if it is a bus fault type identifier. All elements in the set are traversed, and each element is compared with a bus fault type identifier. When all elements in the set are equal to the bus fault type identifier, the preceding distribution transformer... The fault type set check passes. Next, each element in the fault type set of the subsequent distribution transformers is checked to determine if it contains a fault-free identifier. All elements in the set are traversed, and each element is compared with a fault-free identifier. If all elements in the set are equal to a fault-free identifier, the subsequent distribution transformer fault type set check passes. If both the preceding and subsequent distribution transformer fault type set checks pass, the fault determination result is confirmed to be correct. The distribution loop contains 5 distribution transformers. A loop topology state matrix is ​​constructed according to the connection order. The matrix contains 5 elements, with indices 0 to 4 corresponding to the 1st to 5th distribution transformers, respectively. After the intelligent terminal of each distribution transformer determines the fault type...Write the fault type identifier into the corresponding position in the loop topology state matrix. Index 0 records no fault, index 1 records a bus fault, index 2 records a bus fault, index 3 records an incoming line fault, and index 4 records no fault. Construct a power supply direction matrix, where the power supply direction identifiers from index 0 to index 4 are all positive power supply. Traverse the elements in the loop topology state matrix. The fault type at index 3 is an incoming line fault. Extract the distribution transformer at index 3 as the target distribution transformer. Read the power supply direction identifier at index 3 from the power supply direction matrix; it is positive power supply. The preceding distribution transformer is the distribution transformer with an index less than 3, including the distribution transformers at index 0, index 1, and index 2. The following distribution transformer is the distribution transformer with an index greater than 3, including the distribution transformer at index 4. From the loop topology state matrix... The fault type identifiers at indices 0, 1, and 2 are read. Index 0 indicates no fault, index 1 indicates a bus fault, and index 2 indicates a bus fault. These three fault type identifiers are combined into a preceding distribution transformer fault type set. Traversing this set, the fault type at index 0 (no fault) does not equal a bus fault, so the preceding distribution transformer fault type set check fails. The fault type identifier at index 4 in the loop topology state matrix is ​​read as "no fault," and this identifier is combined into a subsequent distribution transformer fault type set. Traversing this set, the fault type at index 4 (no fault) equals "no fault," so the subsequent distribution transformer fault type set check passes. However, because the preceding distribution transformer fault type set check fails, the fault determination result cannot be confirmed as correct.

[0054] In one specific embodiment, it is checked whether the set of fault types of the preceding distribution transformers are all bus faults, and whether the set of fault types of the subsequent distribution transformers are all fault-free. When all checks pass, the fault determination result is confirmed to be correct, including:

[0055] Read the power transmission direction identification value of the target distribution transformer from the power transmission direction matrix, and determine the location range of the fault type set of the preceding distribution transformer and the fault type set of the following distribution transformer based on the power transmission direction identification value;

[0056] The bus fault type matching degree is calculated for the set of preceding distribution transformer fault types. The ratio of the number of bus fault types in the set to the total number of elements in the set is calculated to obtain the preceding matching degree value. The fault-free type matching degree is calculated for the set of subsequent distribution transformer fault types. The ratio of the number of fault-free types in the set to the total number of elements in the set is calculated to obtain the subsequent matching degree value.

[0057] When both the preceding and following matching degree values ​​are equal to 1, the loop status identifier value at the corresponding position in the loop topology status matrix is ​​set to a single-point fault locationable state; when either the preceding or following matching degree value is less than 1, the loop status identifier value is set to a multi-point fault pending verification state.

[0058] Specifically, the power transmission direction identifier value of the target distribution transformer is read from the power transmission direction matrix. The power transmission direction identifier value includes two types: forward power transmission and reverse power transmission. Based on the power transmission direction identifier value, the location range of the preceding and following distribution transformer fault type sets is determined. When the power transmission direction identifier value is forward power transmission, the preceding distribution transformers are all distribution transformers before the target distribution transformer's position index in the loop topology state matrix, and the following distribution transformers are all distribution transformers after the position index. When the power transmission direction identifier value is reverse power transmission, the preceding distribution transformers are all distribution transformers after the position index, and the following distribution transformers are all distribution transformers before the position index. This process is applied to the preceding distribution transformer... The fault type matching degree of the preceding distribution transformer fault type set is calculated by iterating through each element in the preceding distribution transformer fault type set and counting the number of elements whose fault type identifier is equal to bus fault. The number of bus fault types is then divided by the total number of elements in the set. The ratio is calculated by dividing the number of bus fault types by the total number of elements in the set. The preceding matching degree value ranges from 0 to 1. When all elements in the set are bus faults, the preceding matching degree value is 1; when there are no bus faults in the set, the preceding matching degree value is 0. The fault-free type matching degree of the subsequent distribution transformer fault type set is then calculated by iterating through each element in the subsequent distribution transformer fault type set. For each element, the number of elements with a fault type identifier equal to "no fault" is counted. The number of "no fault" elements is then divided by the total number of elements in the set, with the number of "no fault" elements as the numerator and the total number of elements as the denominator. This division yields the subsequent matching degree value, which ranges from 0 to 1. The subsequent matching degree value is 1 when all elements in the set are fault-free, and 0 when none of the elements are fault-free. Finally, both the preceding and subsequent matching degree values ​​are checked. If both the preceding and subsequent matching degree values ​​are 1, it indicates that all distribution transformers upstream of the target distribution transformer have detected a bus fault, while all distribution transformers downstream of the target distribution transformer have not detected one. Upon encountering a fault, which conforms to the electrical propagation law of a single-point fault, the loop status identifier value corresponding to the target distribution transformer location in the loop topology state matrix is ​​set to a single-point fault locatable state. This indicates that the fault location has been accurately located and the fault type has been correctly determined. If the preceding or subsequent matching degree value is less than 1, it indicates that there is a non-busbar fault type in the preceding distribution transformer or a non-fault-free type in the subsequent distribution transformer, which does not conform to the electrical propagation law of a single-point fault. In this case, the loop status identifier value is set to a multi-point fault pending verification state. This indicates that there are multiple fault points in the distribution loop or that the fault determination result is incorrect and requires further verification. The distribution loop contains 5 distribution transformers.The distribution transformer at index 3 of the loop topology state matrix is ​​identified as having an incoming-side fault and is selected as the target distribution transformer. The power transmission direction identifier at index 3 is read from the power transmission direction matrix as positive power transmission. Based on positive power transmission, the location range of the preceding distribution transformer is determined to be from index 0 to index 2, and the location range of the following distribution transformer is index 4. The fault type identifiers at indexes 0 to 2 are read from the loop topology state matrix: index 0 indicates no fault, index 1 indicates a bus fault, and index 2 indicates a bus fault. These three fault type identifiers form a set of preceding distribution transformer fault types, with a total of 3 elements. Traversing this set, the fault type identifier at index 1 equals a bus fault, and the fault type identifier at index 2 also equals a bus fault. The number of bus fault types is 2. Dividing the number of bus fault types (2) by the total number of elements (3) gives a preceding matching degree of approximately 0.67. The fault type identifier at index 4 in the loop topology state matrix is ​​read as "no fault". This fault type identifier is used to form a set of subsequent distribution transformer fault types, with a total of 1 element. Traversing this set, the fault type identifier at index 4 equals "no fault", and the number of "no fault" types is 1. Using the number of "no fault" types (1) as the numerator and the total number of elements in the set (1) as the denominator, a division is performed. Dividing 1 by 1 yields a subsequent matching degree value of 1. The preceding matching degree value (0.67) is not equal to 1. Therefore, the loop state identifier at index 3 in the loop topology state matrix is ​​set to a multi-point fault pending verification state. In another scenario where the fault type identifiers at indices 0 to 2 are all bus faults, the number of bus fault types is 3, and the total number of elements in the set is 3. Dividing 3 by 3 yields a preceding matching degree value of 1, and the subsequent matching degree value is also 1. Since both the preceding and subsequent matching values ​​are 1, the loop state identifier value is set to a single-point fault locatable state.

[0059] In one specific embodiment, an isolation control command is generated based on the confirmed fault determination result, and the isolation control command is executed to achieve isolation of the faulty area and restoration of power supply to the non-faulty area, including:

[0060] Read the loop status identifier value from the loop topology state matrix. When the loop status identifier value is a single-point fault locationable state, extract the location index and fault type of the faulty distribution transformer. Query the fault isolation strategy mapping table according to the fault type to obtain the target disconnect switch combination.

[0061] A switch-opening command sequence is generated based on the target disconnector switch combination. The switch-opening command sequence is then sent to the high-voltage side switch actuator of the corresponding distribution transformer via a communication link, controlling the switches in the target disconnector switch combination to perform the opening operation and complete the isolation of the fault area.

[0062] Identify a set of healthy distribution transformers that are in the same distribution loop as the faulty distribution transformer and located in a non-faulty area from the loop topology state matrix. Perform topology analysis on the power supply path of each distribution transformer in the healthy distribution transformer set, generate a switch closing command sequence to control the switch on the backup power supply path to perform the closing operation, and complete the power supply restoration of the healthy distribution transformer set.

[0063] Specifically, the loop status identifier value is read from the loop topology state matrix. This value is recorded in the matrix corresponding to the target distribution transformer. When the loop status identifier value is a single-point fault locationable state, the location index and fault type of the faulty distribution transformer are extracted. The location index is the transformer's position number in the loop topology state matrix, and the fault type is the fault type identifier determined by the transformer's intelligent terminal. Based on the fault type, the target disconnector switch combination is obtained by querying the fault isolation strategy mapping table. This table is a pre-planned lookup table, where each row records the switch combination that needs to be tripped corresponding to a specific fault type. When the fault type is an incoming-side fault, the target disconnector switch combination includes the faulty distribution transformer... When the fault type is a load-side fault, the target isolating switch combination includes the load switch of the faulty distribution transformer. A switch-opening command sequence is generated based on the target isolating switch combination. This sequence consists of a series of switch control commands arranged in operational order. Each command includes the location index of the target distribution transformer, the switch type, and the opening operation code. The switch-opening command sequence is sent to the high-voltage side switch actuator of the corresponding distribution transformer via a communication link, which can be wireless or wired. The intelligent terminal sends each command in the command sequence sequentially. Upon receiving the command, the switch actuator drives the switch operating mechanism to perform the opening action, controlling the switches in the target isolating switch combination. The switch performs a tripping operation to isolate the fault area. Fault area isolation refers to electrically disconnecting the fault point from the power supply and the healthy area through the tripping operation. From the loop topology state matrix, a set of healthy distribution transformers located in the same distribution loop as the faulty distribution transformer and in the non-faulty area is identified. This set of healthy distribution transformers includes all distribution transformers with fault type marked as fault-free. The loop topology state matrix is ​​traversed, and distribution transformers with fault type marked as fault-free and whose location index is greater than the location index of the faulty distribution transformer are selected. These distribution transformers are then grouped into a set of healthy distribution transformers. Topology analysis is performed on the power supply paths of each distribution transformer in the set of healthy distribution transformers. Topology analysis involves traversing the connection relationships of the distribution loop to find the path from... The available power supply paths from the backup power source to the viable distribution transformer are determined. Distribution loops typically have a ring network structure, with backup power supply paths existing in addition to the main power supply path. These backup power supply paths are connected to the backup power source via tie switches. Topology analysis first determines the location of each distribution transformer in the viable distribution transformer set, then locates the backup power source at the other end of the distribution loop, tracks the status of all switches between the backup power source and the viable distribution transformer, and generates a switch closing command sequence to control the switches on the backup power supply path to perform closing operations. The switch closing command sequence includes control commands for the tie switches and sectionalizing switches that need to be closed. This sequence is then sent to the corresponding switch actuators via a communication link, and the switch actuators drive the switch operating mechanisms to perform the closing action.After restoring power to the complete distribution transformer set, the distribution transformer at index 3 in the distribution loop is determined to have an incoming-side fault, and the loop status identifier is a single-point fault locatable state. The loop status identifier at index 3 is read from the loop topology status matrix as a single-point fault locatable state. The location index of the faulty distribution transformer is extracted as 3, and the fault type is an incoming-side fault. Based on the incoming-side fault type, the fault isolation strategy mapping table is queried. The target disconnect switch combination corresponding to the incoming-side fault type in the mapping table includes the incoming switch of the distribution transformer at index 3 and the outgoing switch of the distribution transformer at index 2. A switch tripping instruction sequence is generated. The first instruction contains location index 3, switch type is incoming switch, and operation code is tripping. The second instruction contains location index 2, switch type is outgoing switch, and operation code is tripping. The first instruction is sent to the incoming switch actuator of the distribution transformer at index 3 via the communication link. The switch actuator receives... Following the instruction, the incoming line switch is opened. The second instruction is sent via the communication link to the outgoing line switch actuator of the distribution transformer at index 2. The switch actuator opens the outgoing line switch, completing the fault area isolation. All elements are traversed from the loop topology state matrix. The fault type at index 4 is identified as fault-free, and its position index is greater than the faulty distribution transformer's position index 3. The distribution transformers at index 4 are grouped into a healthy distribution transformer set. Topology analysis is performed on the power supply path of the distribution transformer at index 4. A backup power supply exists at the other end of the distribution loop, connected to the distribution transformer at index 4 via a tie switch. The tie switch is currently in the open state. A switch closing instruction sequence is generated, containing the tie switch's position identifier and closing operation code. The instruction is sent via the communication link to the tie switch actuator, which closes the tie switch. The distribution transformer at index 4 receives power from the backup power supply, completing power restoration.

[0064] The above describes the fault identification method for the high-voltage side intelligent terminal of the distributed distribution transformer in the embodiments of this application. The following describes the fault identification system for the high-voltage side intelligent terminal of the distributed distribution transformer in the embodiments of this application. Please refer to [link to relevant documentation]. Figure 2 One embodiment of the distributed distribution transformer high-voltage side intelligent terminal fault identification system in this application includes:

[0065] The processing module is used to acquire the three-phase current signal on the high-voltage side of the distribution transformer, perform signal preprocessing on the three-phase current signal, and obtain the preprocessed current signal.

[0066] The calculation module is used to extract the effective values ​​of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current.

[0067] The encoding module is used to collect the status information of the high-voltage side switch of the distribution transformer, encode the status information of the switch into a status identifier, and determine the fault type of the distribution transformer by combining the three-phase current imbalance characteristic parameters.

[0068] The verification module is used to establish topological relationship data of multiple distribution transformers within the distribution loop, verify the determined fault type based on the topological relationship data, and confirm the fault determination result.

[0069] The implementation module is used to generate isolation control instructions based on the confirmed fault determination results, and execute the isolation control instructions to realize the isolation of the fault area and the restoration of power supply to the non-fault area.

[0070] above Figure 2 The fault identification system of the high-voltage side intelligent terminal of the distributed distribution transformer in this embodiment of the invention is described in detail from the perspective of modular functional entities. The fault identification device of the high-voltage side intelligent terminal of the distributed distribution transformer in this embodiment of the invention is described in detail from the perspective of hardware processing.

[0071] Reference Figure 3 This invention also provides a distributed distribution transformer high-voltage side intelligent terminal fault identification device, which can be a server, and its internal structure can be as follows: Figure 3 As shown, the distributed distribution transformer high-voltage side intelligent terminal fault identification device includes a processor, memory, display screen, input device, network interface, and database connected via a system bus. The processor, designed as a computer, provides computing and control capabilities. The memory of the distributed distribution transformer high-voltage side intelligent terminal fault identification device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the distributed distribution transformer high-voltage side intelligent terminal fault identification device stores the data corresponding to this embodiment. The network interface of the distributed distribution transformer high-voltage side intelligent terminal fault identification device is used for communication with external terminals via network connection. When the computer program is executed by the processor, it implements the above-described method.

[0072] Those skilled in the art will understand that Figure 3 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the distributed distribution transformer high-voltage side intelligent terminal fault identification device to which the present invention is applied.

[0073] The present invention also provides a computer-readable storage medium, which can be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when the instructions are executed on a computer, cause the computer to perform the steps of the distributed distribution transformer high-voltage side intelligent terminal fault identification method.

[0074] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0075] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or 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 distributed distribution transformer high-voltage side intelligent terminal fault identification 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.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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. Such 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 method for fault identification in a distributed distribution transformer high-voltage side intelligent terminal, characterized in that, The method includes: The three-phase current signal on the high-voltage side of the distribution transformer is collected, and the three-phase current signal is preprocessed to obtain the preprocessed current signal. Extract the effective value of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current. The process involves: collecting the status information of the high-voltage side switches of the distribution transformer, encoding the status information of the switches into status identifiers, and determining the fault type of the distribution transformer by combining the three-phase current imbalance characteristic parameters. This includes: collecting the status of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer; defining the open state as 0 and the closed state as 1; encoding the switch status triplets based on the combination of the three switch states to obtain the status identifiers; obtaining the power transmission direction identifier of the distribution loop where the distribution transformer is located; querying the fault-aware area mapping table based on the status identifiers to obtain the range of perceptible fault locations; comparing the three-phase current imbalance characteristic parameters with a preset threshold; and determining the fault type of the distribution transformer within the perceptible fault location range by combining the numerical distribution relationship of the per-unit values ​​of the phase currents when the three-phase current imbalance characteristic parameters are greater than the preset threshold. Establish topological relationship data for multiple distribution transformers within the distribution loop, verify the determined fault type based on the topological relationship data, and confirm the fault determination result; Based on the confirmed fault determination result, an isolation control command is generated, and the isolation control command is executed to achieve isolation of the faulty area and restoration of power supply to the non-faulty area.

2. The method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal according to claim 1, characterized in that, The process of acquiring the three-phase current signal from the high-voltage side of the distribution transformer, and performing signal preprocessing on the three-phase current signal to obtain a preprocessed current signal includes: The original three-phase current signals are obtained by synchronously acquiring the A-phase current signal, B-phase current signal, and C-phase current signal at the positions of the incoming switch, outgoing switch, and load switch on the high-voltage side of the distribution transformer using a current transformer. The original three-phase current signal is decomposed into multiple wavelet bases to obtain approximation coefficients and multiple detail coefficients. The multiple detail coefficients are then denoised using a threshold function. The denoised current signal is then reconstructed by inverse wavelet transform. The denoised current signal is converted to the frequency domain by Fast Fourier Transform, filtered by the frequency domain transfer function of the Wiener filter, and then converted to the time domain by Inverse Fast Fourier Transform to obtain the preprocessed current signal.

3. The method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal according to claim 1, characterized in that, The process involves extracting the effective values ​​of each phase current from the preprocessed current signal, calculating the ratio between the current effective values ​​of each phase current and the corresponding reference current values ​​to obtain the per-unit value of each phase current, and calculating the three-phase current imbalance characteristic parameters based on the per-unit values ​​of each phase current, including: The preprocessed current signal is subjected to effective value extraction processing to obtain the effective values ​​of phase A current, phase B current and phase C current respectively; Read the A-phase reference current value, B-phase reference current value, and C-phase reference current value before the fault occurred from the historical current reference value storage queue. Divide the effective value of the A-phase current by the A-phase reference current value to obtain the per-unit value of the A-phase current. Divide the effective value of the B-phase current by the B-phase reference current value to obtain the per-unit value of the B-phase current. Divide the effective value of the C-phase current by the C-phase reference current value to obtain the per-unit value of the C-phase current. The maximum current per-unit value and the intermediate current per-unit value are selected from the current per-unit values ​​of phase A, phase B, and phase C. The maximum current per-unit value is divided by the intermediate current per-unit value to obtain the three-phase current imbalance characteristic parameters.

4. The method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal according to claim 1, characterized in that, The process of establishing topological relationship data for multiple distribution transformers within a distribution loop, verifying the determined fault type based on the topological relationship data, and confirming the fault determination result includes: A loop topology state matrix is ​​constructed according to the connection sequence of the distribution transformers in the distribution loop. The loop topology state matrix records the fault type of the distribution transformer at each location. A power transmission direction matrix of the same dimension is constructed to record the power transmission direction identifier of the distribution transformer at each location. Extract the target distribution transformer with fault type of incoming side fault or load side fault from the loop topology state matrix, and obtain the set of fault types of the preceding distribution transformer and the set of fault types of the following distribution transformer for the target distribution transformer; Check whether the set of fault types of the preceding distribution transformers are all bus faults, and check whether the set of fault types of the following distribution transformers are all fault-free. When all checks pass, the fault determination result is confirmed to be correct.

5. The method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal according to claim 4, characterized in that, The process of checking whether the preceding set of distribution transformer fault types all represent bus faults and checking whether the subsequent set of distribution transformer fault types all represent no faults, confirming the fault determination result is correct when all checks pass, includes: Read the power transmission direction identifier value of the target distribution transformer from the power transmission direction matrix, and determine the location range of the fault type set of the preceding distribution transformer and the fault type set of the following distribution transformer based on the power transmission direction identifier value; The bus fault type matching degree is calculated for the set of preceding distribution transformer fault types. The ratio of the number of bus fault types in the set to the total number of elements in the set is calculated to obtain the preceding matching degree value. The fault-free type matching degree is calculated for the set of subsequent distribution transformer fault types. The ratio of the number of fault-free types in the set to the total number of elements in the set is calculated to obtain the subsequent matching degree value. When both the preceding and following matching degree values ​​are equal to 1, the loop status identifier value at the corresponding position in the loop topology status matrix is ​​set to a single-point fault locationable state; when either the preceding or following matching degree value is less than 1, the loop status identifier value is set to a multi-point fault pending verification state.

6. The method for fault identification of a distributed distribution transformer high-voltage side intelligent terminal according to claim 5, characterized in that, The step of generating isolation control commands based on the confirmed fault determination results and executing the isolation control commands to achieve fault area isolation and power restoration to non-fault areas includes: Read the loop status identifier value from the loop topology state matrix. When the loop status identifier value is a single-point fault locationable state, extract the location index of the faulty distribution transformer and the fault type. Query the fault isolation strategy mapping table according to the fault type to obtain the target disconnect switch combination. A switch-opening instruction sequence is generated based on the target disconnector switch combination. The switch-opening instruction sequence is then sent to the high-voltage side switch actuator of the corresponding distribution transformer via a communication link, thereby controlling the switches in the target disconnector switch combination to perform the opening operation and complete the isolation of the fault area. Identify a set of healthy distribution transformers that are in the same distribution loop as the faulty distribution transformer and located in a non-faulty area from the loop topology state matrix. Perform topology analysis on the power supply path of each distribution transformer in the healthy distribution transformer set, generate a switch closing command sequence to control the switch on the backup power supply path to perform the closing operation, and complete the power supply restoration of the healthy distribution transformer set.

7. A fault identification system for a distributed distribution transformer high-voltage side intelligent terminal, characterized in that, For implementing the distributed distribution transformer high-voltage side intelligent terminal fault identification method as described in any one of claims 1-6, the distributed distribution transformer high-voltage side intelligent terminal fault identification system comprises: The processing module is used to acquire the three-phase current signal on the high-voltage side of the distribution transformer, perform signal preprocessing on the three-phase current signal, and obtain the preprocessed current signal. The calculation module is used to extract the effective values ​​of each phase current of the preprocessed current signal, calculate the ratio of the current effective value of each phase current to the corresponding reference current value, obtain the per-unit value of each phase current, and calculate the three-phase current imbalance characteristic parameters based on the per-unit value of each phase current. The encoding module is used to collect the status information of the high-voltage side switch of the distribution transformer, encode the status information of the switch into a status identifier, and determine the fault type of the distribution transformer by combining the three-phase current imbalance characteristic parameters. The verification module is used to establish topological relationship data of multiple distribution transformers within the distribution loop, verify the determined fault type based on the topological relationship data, and confirm the fault determination result. The implementation module is used to generate isolation control instructions based on the confirmed fault determination results, and execute the isolation control instructions to realize the isolation of the fault area and the restoration of power supply to the non-fault area.

8. A fault identification device for a distributed distribution transformer high-voltage side intelligent terminal, characterized in that, The method includes a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the distributed distribution transformer high-voltage side intelligent terminal fault identification 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 run by the processor, it causes the processor to execute the distributed distribution transformer high-voltage side intelligent terminal fault identification method as described in any one of claims 1 to 6.

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