Secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics

Abstract

The invention relates to a secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics, and the method comprises the following steps: (1) obtaining transient recording data in a relay protection device, carrying out the further data preprocessing of the transient recording data, and removing errors and noise contained in the transient recording data; (2) calculating an electrical quantity characteristic value required by fault diagnosis according to the acquired data; (3) carrying out invisible fault diagnosis processing by using the sampling loop invisible fault expert database; and (4) generating an abnormal equipment alarm prompt according to the obtained diagnosis result so as to complete fault diagnosis. According to the secondary sampling loop hidden fault diagnosis method based on the transient recording data characteristics, the hidden characteristics in the fault (or starting) transient waveform of the relay protection device are fully extracted, and the mapping relation between the recording characteristics and the hidden faults is established through the expert rule base, so that the fault (or starting) of the relay protection device is accurately diagnosed. And the hidden fault of the secondary sampling loop can be diagnosed quickly and accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, in particular to the field of hidden fault diagnosis of secondary sampling circuits, and specifically refers to a hidden fault diagnosis method of secondary sampling circuits based on transient recording data characteristics. Background Art

[0002] With the continuous growth of the scale of power grids and the increasing proportion of new energy, the complexity of power systems has gradually increased, and they are facing more severe challenges in operational stability. As the first line of defense of the power system, relay protection devices play an important role in ensuring the long-term safe and stable operation of the power system. According to statistics, more than 75% of large-scale power outages at home and abroad are directly or indirectly related to incorrect operation of relay protection. It can be seen that the key to the stable operation of the power system is whether the relay protection device operates correctly.

[0003] As an important component of the relay protection device, the secondary sampling circuit converts various electrical parameters into digital signals through sensors, providing a basis for the judgment and action of the relay protection device. Therefore, it is not only the basis of the relay protection device, but also the basis of power system automation.

[0004] Hidden faults in the secondary sampling circuit refer to defects caused by inherent defects (such as design defects) or human factors (such as wiring errors) in the secondary sampling circuit of the relay protection device. Such defects are not easy to detect during daily operation or routine inspections of the power system, and generally only occur under specific conditions, such as when the power grid system is disturbed or fails (such as out-of-zone faults, flow reversals, and large voltage drops). Although the possibility of hidden faults being triggered is small, once triggered, it may cause the relay protection device to malfunction or refuse to operate, expand the scope of the fault, and even trigger a chain failure of the power system, causing large-scale power outages, bringing significant economic losses and personal safety risks.

[0005] For a long time, the diagnosis method of hidden faults in the secondary sampling circuit of relay protection devices in my country mainly relies on traditional means such as device inspection, post-action evaluation, and operation status assessment. It tends to occur first and then identify the fault according to the fault situation. It is "hindsight" and lacks the means of "preventive treatment". Therefore, if the hidden faults of the relay protection device can be discovered in time before they are triggered, and automatic warnings and intervention processing are prompted, the incorrect operation of the relay protection device can be effectively avoided, and the scope of the accident can be prevented from expanding, which is of great significance to ensuring the safe and reliable operation of the power system.

[0006] The diagnosis of hidden faults in the secondary sampling circuit of the power system is an important part of ensuring the safe and stable operation of the power system. Domestic and foreign scholars have conducted a lot of research on this issue. For example, Zhou Xiaozhou et al. [1]It is proposed to build a multi-layer distribution model for fault information collection, combine the detection of the fundamental component of the excitation flux linkage to fuse the fault feature information, and use the current limit circle and voltage limit feature detection method to extract the fault feature, and locate and identify the fault state parameters through real-time spectrum detection, and build a positioning monitoring model, and finally realize the real-time monitoring of the fault state of the secondary circuit of the power system relay protection with dual-port voltage stabilization control. Yang Yuhan et al. [2] Using PLC technology, the temperature changes and ambient light and shadow changes during the operation of the protection device are detected in real time, and a fault identification and detection mechanism is established. Intelligent fault diagnosis of the secondary circuit is carried out from three levels: SV link diagnosis, current circuit diagnosis, and protection action diagnosis. Using real-time spectrum detection method, a real-time spectrum detection positioning optimization model is established to realize the fault location of the relay protection secondary circuit. Du Junjie et al. [3] A safety hazard monitoring and early warning method for relay protection secondary circuit based on FPGA is proposed. Firstly, the equivalent circuit model of the relay protection secondary circuit is constructed. Then, the output current effective value and the third harmonic plane current component of the relay protection secondary circuit are used as constraint variables to analyze the stability of the stator current of each phase of the secondary circuit. Then, according to the stability analysis results and the actual operating conditions of the relay protection secondary circuit, the safety hazard characteristics are analyzed, so as to extract the characteristic quantities under the safety hazard states such as single-phase open-phase fault. Finally, the monitoring and early warning of the safety hazard of the secondary circuit are realized according to the characteristic quantity extraction results.

[0007] Some of the above traditional methods require the addition of additional data collection and transfer channels when constructing the substation, while others require the addition of additional auxiliary hardware equipment. In other words, there is currently a lack of a hidden fault diagnosis method for the secondary sampling loop of the power system that can be applied to most of the substations that have been built without additional costs.

[0008] References:

[0009] [1] Zhou Xiaozhou, Fan Changxin, Wei Yaqiu, et al. Real-time monitoring and analysis of secondary circuit fault status of relay protection[J]. Integrated Circuit Applications, 2022, 39(03): 284-285. DOI: 10.19339 / j.issn.1674-2583.2022.03.129.

[0010] [2] Yang Yuhan. Maintenance method of secondary circuit of relay protection in smart substation based on PLC technology[J]. Electronic Design Engineering, 2023, 31(10): 25-28+33. DOI: 10.14022 / j.issn1674-6236.2023.10.006.

[0011] [3] Du Junjie, He Lihui, Du Yang, et al. Safety hazard monitoring and early warning method of relay protection secondary circuit based on FPGA[J]. Bulletin of Science and Technology, 2019, 35(09): 61-65. DOI: 10.13774 / j.cnki.kjtb.2019.09.011. Summary of the invention

[0012] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for diagnosing hidden faults of a secondary sampling circuit based on the characteristics of transient recording data.

[0013] In order to achieve the above object, the secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics of the present invention is as follows:

[0014] The main feature of the secondary sampling circuit hidden fault diagnosis method based on transient recording data characteristics is that the method comprises the following steps:

[0015] (1) Obtain transient recording data from the relay protection device and perform further data preprocessing to remove the errors and noise contained therein;

[0016] (2) Calculating the electrical quantity characteristic values ​​required for fault diagnosis based on the acquired data;

[0017] (3) Using the hidden fault expert database of sampling loops to diagnose and process hidden faults;

[0018] (4) Generate abnormal equipment alarm prompts based on the acquired diagnostic results to complete fault diagnosis.

[0019] Preferably, the step (1) includes performing semantic standardization of the recording channel in the following manner:

[0020] The composition format for setting the semantics of the recording channel is: type phase_serial number, where the serial number can be omitted for relay protection devices that have only one set of three-phase current / voltage channels or only one set of three-phase current / voltage channels that need to participate in diagnosis; for relay protection devices with multiple sets of current / voltage channels, if their names contain numbers, the serial number is set to be consistent with the numbers, otherwise the serial number is incremented.

[0021] Preferably, the step (1) includes performing transient recording resampling processing in the following manner:

[0022]

[0023]

[0024] Among them, x(n) represents the original sampling value at time n, y(t) represents the sampling value at time t after resampling, m represents the sliding window radius, ω represents the weight, and the sum of the weights of each point in the sliding window is equal to 1.

[0025] Preferably, the electrical quantity characteristic value in step (2) includes a DC component, a fundamental component, a second harmonic component, a third harmonic component and a self-generated zero-sequence effective value, wherein the DC component, the fundamental component, the second harmonic component and the third harmonic component are calculated in the following manner:

[0026]

[0027] Where i(n) represents the channel sampling value, n ranges from {0,1,2,…,N-1}, and N is the total number of sampling points in one cycle; k represents the harmonic order, and ranges from {0,1,2,…,N-1}. The calculation formulas for the DC component I(0), fundamental component I(1), second harmonic component I(2), and third harmonic component I(3) are as follows:

[0028]

[0029] The self-generated zero-sequence effective value is the sum of the effective values ​​of the three-phase channels:

[0030] I 0 (0) = I A (0)+I B (0)+I C (0)

[0031] Among them, I 0 (0) indicates the self-generated zero-sequence effective value, I A (0),I B (0) I C (0) are the effective values ​​of the three-phase channels A, B, and C respectively.

[0032] Preferably, the step (3) comprises performing CT saturation diagnosis in the following manner:

[0033] (3.1.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0034] (3.1.2) Sampling window: 10ms to 50ms, i.e., from the half cycle after the mutation point to 2.5 cycles;

[0035] (3.1.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection;

[0036] (3.1.4) Identification method: a) Determine whether the maximum effective value in the time window is greater than the threshold. If so, perform CT saturation judgment, otherwise directly report normal; b) For the recordings that meet the diagnostic prerequisites, continue to determine whether the maximum value of the percentage of the second and third harmonics of the current channel in the sampling window to the fundamental content exceeds the threshold. If one of them exceeds the threshold, it is diagnosed as a CT saturation diagnosis abnormality.

[0037] Preferably, the step (3) includes performing CT-N disconnection diagnosis in the following manner:

[0038] (3.2.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0039] (3.2.2) Sampling window: 0ms to 40ms, i.e. two cycles after the mutation point;

[0040] (3.2.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection;

[0041] (3.2.4) Identification method: a) Determine whether the current fault type is an asymmetric ground fault. If so, perform CT saturation judgment, otherwise the notification is not applicable; b) For line protection recordings that meet the diagnostic prerequisites, if the maximum effective value of its self-generated or external zero-sequence current in the sampling window is greater than 0.05In, it is judged to be normal, otherwise it is judged to be abnormal; c) For main transformer protection recordings that meet the diagnostic prerequisites, if the maximum effective values ​​of its self-generated and external zero-sequence current in the sampling window are both greater than or less than 0.05In, it is judged to be normal; that is, if the self-generated value is greater than the threshold and the external value is less than the threshold, the diagnosis is that the neutral point CT of the main transformer is broken; if the self-generated value is less than the threshold and the external value is greater than the threshold, the diagnosis is that the main transformer switch CT is broken.

[0042] Preferably, the step (3) includes performing CT-N two-point grounding diagnosis in the following manner:

[0043] (3.3.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0044] (3.3.2) Sampling window: full range of recording;

[0045] (3.3.3) Sampling channel: including external zero-sequence current channel and self-generated zero-sequence current channel;

[0046] (3.3.4) Identification method: a) Determine whether the maximum effective values ​​of the two zero-sequence currents within the time window are zero-drifting values. If so, perform CT-N two-point grounding diagnosis, otherwise the notification is not applicable; b) Compare the effective values ​​of the self-generated zero-sequence current and the external zero-sequence current of the same recording point by point. When there are three consecutive points with effective value errors greater than 10%, it is diagnosed as CT-N two-point grounding.

[0047] Preferably, the step (3) includes performing PT-N high resistance diagnosis in the following manner:

[0048] (3.4.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this station and adjacent substations;

[0049] (3.4.2) Sampling window: recording of the steady-state section before the fault starting point, i.e. recording the first cycle;

[0050] (3.4.3) Sampling channels: including the voltage channel of line protection, the voltage channels of each busbar of busbar protection, and the voltage channels of each side of main transformer protection;

[0051] (3.4.4) Identification method: a) Determine whether the first cycle of the recording is a steady-state segment. If so, perform PT-N high resistance diagnosis, otherwise the notification is not applicable; b) If the absolute value threshold of the third harmonic of any phase in the three-phase voltage channel is greater than 6V, it is directly diagnosed as PT-N high resistance.

[0052] The secondary sampling circuit hidden fault diagnosis method based on transient recording data characteristics of the present invention is adopted. In view of the problems of narrow application scope and high cost of the existing secondary sampling circuit hidden fault scheme, firstly, the fault (or startup) transient recordings generated by each relay protection device in the substation are collected and sorted, and the electrical quantity characteristics (such as third harmonic content, self-generated zero-sequence current, etc.) are calculated; then, the data are input into the expert rule library respectively, and various hidden fault diagnosis conclusions are obtained according to relevant criteria; finally, the abnormal items and specific criteria of the relay protection device are given, thereby improving the hidden fault troubleshooting efficiency of operation and maintenance personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The present invention is a flow chart of the method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics.

[0054] Figure 2 It is a schematic diagram of a channel semantic configuration tool of the secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics of the present invention.

[0055] Figure 3 It is a schematic diagram of waveform comparison before and after resampling of the secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics of the present invention. DETAILED DESCRIPTION

[0056] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0057] Before describing in detail embodiments according to the present invention, it should be noted that, hereinafter, the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, whereby a process, method, article or apparatus comprising a series of elements includes not only these elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0058] See also Figure 1 As shown, the secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics, wherein the method comprises the following steps:

[0059] (1) Obtain transient recording data from the relay protection device and perform further data preprocessing to remove the errors and noise contained therein;

[0060] (2) Calculating the electrical quantity characteristic values ​​required for fault diagnosis based on the acquired data;

[0061] (3) Using the hidden fault expert database of sampling loops to diagnose and process hidden faults;

[0062] (4) Generate abnormal equipment alarm prompts based on the acquired diagnostic results to complete fault diagnosis.

[0063] In practical applications, in order to make full use of the relay protection devices in the existing substations, especially those with early production dates and insufficient transient recording data standardization, it is necessary to annotate the semantics of each channel in the recording. At the same time, in the actual production environment, the relay protection device is affected by factors such as the operating environment, the mutual inductance of multiple circuits on the same tower, and insufficient sampling frequency. Its transient recording data may contain certain errors and noise, which need to be removed by resampling methods.

[0064] As a preferred embodiment of the present invention, the step (1) includes performing semantic standardization of the recording channel in the following manner:

[0065] The composition format for setting the semantics of the recording channel is: type phase_serial number, where the serial number can be omitted for relay protection devices that have only one set of three-phase current / voltage channels or only one set of three-phase current / voltage channels that need to participate in diagnosis; for relay protection devices with multiple sets of current / voltage channels, if their names contain numbers, the serial number is set to be consistent with the numbers, otherwise the serial number is incremented.

[0066] For common types of recording channels, take phase A as an example, refer to the following:

[0067] (1) Line / circuit breaker protection: protection voltage Ua; protection current Ia; side circuit breaker current Ia_1; middle circuit breaker current Ia_2.

[0068] (2) T zone / short lead protection: CT1 current Ia_1; CT2 current Ia_2; CT3 current Ia_3.

[0069] (3) Busbar protection: I bus voltage Ua_1; II voltage Ua_2; VI bus voltage Ua_6; branch 1 current Ia_1; branch 2 current Ia_2; large differential current Ia_cd; I bus small differential Ia_cd1; II bus small differential Ia_cd2.

[0070] (4) Transformer protection: high voltage side voltage Ua_1; medium voltage side voltage Ua_2; low voltage 1 side voltage Ua_31; low voltage 2 side voltage Ua_32; high voltage 1 side current Ia_11; high voltage 2 side current Ia_12; medium voltage side current Ia_2; low voltage 1 side current Ia_31; low voltage 2 side current Ia_32.

[0071] As a preferred embodiment of the present invention, the resampling method of the transient recording is sliding weighted sampling, which can effectively remove irregular jitter in the original data and better retain the data peak. The step (1) includes performing transient recording resampling processing in the following manner:

[0072]

[0073]

[0074] Among them, x(n) represents the original sampling value at time n, y(t) represents the sampling value at time t after resampling, m represents the sliding window radius, ω represents the weight, and the sum of the weights of each point in the sliding window is equal to 1.

[0075] As a preferred embodiment of the present invention, the electrical quantity characteristic value described in step (2) includes a DC component, a fundamental component, a second harmonic component, a third harmonic component and a self-generated zero-sequence effective value, wherein the DC component, the fundamental component, the second harmonic component and the third harmonic component are calculated in the following manner:

[0076]

[0077] Where i(n) represents the channel sampling value, n ranges from {0,1,2,…,N-1}, and N is the total number of sampling points in one cycle; k represents the harmonic order, and ranges from {0,1,2,…,N-1}. The calculation formulas for the DC component I(0), fundamental component I(1), second harmonic component I(2), and third harmonic component I(3) are as follows:

[0078]

[0079] The self-generated zero-sequence effective value is the sum of the effective values ​​of the three-phase channels:

[0080] I 0 (0) = I A (0)+I B (0)+I C (0)

[0081] Among them, I 0 (0) indicates the self-generated zero-sequence effective value, I A (0) I B (0) I C (0) are the effective values ​​of the three-phase channels A, B, and C respectively.

[0082] As a preferred embodiment of the present invention, the step (3) includes performing CT saturation diagnosis in the following manner:

[0083] (3.1.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0084] (3.1.2) Sampling window: 10ms to 50ms, i.e., from the half cycle after the mutation point to 2.5 cycles;

[0085] (3.1.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection;

[0086] (3.1.4) Identification method: a) Determine whether the maximum effective value in the time window is greater than the threshold (default 0.5A). If so, perform CT saturation judgment, otherwise directly report normal; b) For the recordings that meet the diagnostic prerequisites, continue to determine whether the maximum value of the percentage of the second and third harmonics of the current channel in the sampling window to the fundamental content exceeds the threshold (default 15%). If one of them exceeds the threshold, it is diagnosed as a CT saturation diagnosis abnormality.

[0087] As a preferred embodiment of the present invention, the step (3) includes performing CT-N disconnection diagnosis in the following manner:

[0088] (3.2.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0089] (3.2.2) Sampling window: 0ms to 40ms, i.e. two cycles after the mutation point;

[0090] (3.2.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection;

[0091] (3.2.4) Identification method: a) Determine whether the current fault type is an asymmetric ground fault. If so, perform CT saturation judgment, otherwise the notification is not applicable; b) For line protection recordings that meet the diagnostic prerequisites, if the maximum effective value of its self-generated or external zero-sequence current in the sampling window is greater than 0.05In, it is judged to be normal, otherwise it is judged to be abnormal; c) For main transformer protection recordings that meet the diagnostic prerequisites, if the maximum effective values ​​of its self-generated and external zero-sequence currents (need to be divided into the zero-sequence currents of the three sides of high, medium and low) in the sampling window are both greater than or less than 0.05In, it is judged to be normal; that is, if the self-generated current is greater than the threshold and the external current is less than the threshold, the diagnosis is that the neutral point CT of the main transformer is broken; if the self-generated current is less than the threshold and the external current is greater than the threshold, the diagnosis is that the main transformer switch CT is broken.

[0092] As a preferred embodiment of the present invention, the step (3) includes performing CT-N two-point grounding diagnosis in the following manner:

[0093] (3.3.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations;

[0094] (3.3.2) Sampling window: full range of recording;

[0095] (3.3.3) Sampling channel: including external zero-sequence current channel and self-generated zero-sequence current channel;

[0096] (3.3.4) Identification method: a) Determine whether the maximum effective values ​​of the two zero-sequence currents in the time window pass through the zero drift value (default 0.1A). If so, perform CT-N two-point grounding diagnosis, otherwise the notification is not applicable; b) Compare the effective values ​​of the self-generated zero-sequence current and the external zero-sequence current of the same recording point by point. When there are three consecutive points with effective value errors greater than 10%, it is diagnosed as CT-N two-point grounding.

[0097] As a preferred embodiment of the present invention, the step (3) includes performing PT-N high resistance diagnosis in the following manner:

[0098] (3.4.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this station and adjacent substations;

[0099] (3.4.2) Sampling window: recording of the steady-state section before the fault starting point, i.e. recording the first cycle;

[0100] (3.4.3) Sampling channels: including the voltage channel of line protection, the voltage channels of each busbar of busbar protection, and the voltage channels of each side of main transformer protection;

[0101] (3.4.4) Identification method: a) Determine whether the first cycle of the recording is a steady-state segment. If so, perform PT-N high resistance diagnosis, otherwise the notification is not applicable; b) If the absolute value threshold of the third harmonic of any phase in the three-phase voltage channel is greater than 6V, it is directly diagnosed as PT-N high resistance.

[0102] A specific embodiment will be given below to explain in detail the secondary sampling loop hidden fault diagnosis method based on transient recording data characteristics of the technical solution:

[0103] The data used in the embodiment of the present invention are derived from the recordings collected at the substation site, a total of 20 transient recordings, of which 10 are normal device recordings and 10 are hidden fault device recordings. Specifically, the hidden fault device recordings are 3 CT saturation faults, 2 CT-N line breaks, 2 CT-N two-point grounding faults, and 3 PT-N high resistance faults. Considering that there is a certain sample imbalance in the data set, the following F is used 1 The score is used to measure the diagnostic accuracy of the secondary sampling loop hidden fault diagnosis system:

[0104]

[0105] Among them: True positive (T P ) represents the number of samples that are actually positive and predicted to be positive; false positive (F P ) represents the number of samples that are actually negative but predicted to be positive; false negative (F N ) represents the number of samples that are actually positive but predicted to be negative.

[0106] like Figure 2 As shown, the transient recording channel semantic configuration tool of the embodiment of the present invention has a semantic recognition function. By selecting two sets of homologous devices or selecting a set of devices alone, the channel semantic configuration can be automatically completed. At the same time, the configured semantics will also be displayed on the tool, which is convenient for checking whether there is mismatch or missing matching, and correcting it in time.

[0107] like Figure 3 As shown in FIG. 1 , it is a diagram showing the effect of resampling the recorded data according to an embodiment of the present invention. It can be seen that the burrs and jitters in the sample value queue are effectively removed after resampling. The diagnostic accuracy of the original waveform is compared with the diagnostic accuracy of the resampled waveform, as shown in Table 1:

[0108] Table 1 Effect of resampling on diagnostic accuracy

[0109]

[0110] It can be seen that sliding weighted sampling can effectively remove irregular jitter in the original data, better retain data peaks, and improve diagnostic accuracy.

[0111] In practical applications, the eigenvalue calculation of the embodiment of the present invention is implemented by the discrete Fourier transform formula, and the corresponding pseudo code is as follows:

[0112]

[0113]

[0114] Through the above algorithm, the required DC component, fundamental component (effective value), second harmonic component, third harmonic component and self-generated zero-sequence effective value can be calculated, and diagnosis can be performed according to the established diagnosis rules.

[0115] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0116] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device.

[0117] A person of ordinary skill in the art may understand that all or part of the steps of the method for implementing the above-mentioned embodiment may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0118] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0119] In the description of this specification, the description with reference to the terms "an embodiment", "some embodiments", "example", "specific example", or "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0120] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0121] The secondary sampling circuit hidden fault diagnosis method based on transient recording data characteristics of the present invention is adopted. In view of the problems of narrow application scope and high cost of the existing secondary sampling circuit hidden fault scheme, firstly, the fault (or startup) transient recordings generated by each relay protection device in the substation are collected and sorted, and the electrical quantity characteristics (such as third harmonic content, self-generated zero-sequence current, etc.) are calculated; then, the data are input into the expert rule library respectively, and various hidden fault diagnosis conclusions are obtained according to relevant criteria; finally, the abnormal items and specific criteria of the relay protection device are given, thereby improving the hidden fault troubleshooting efficiency of operation and maintenance personnel.

[0122] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics, characterized in that: The method comprises the following steps: (1) Obtain transient recording data from the relay protection device and perform further data preprocessing to remove the errors and noise contained therein; (2) Calculating the electrical quantity characteristic values ​​required for fault diagnosis based on the acquired data; (3) Using the sampling loop hidden fault expert database to perform hidden fault diagnosis and processing; (4) Generate abnormal equipment alarm prompts based on the acquired diagnostic results to complete fault diagnosis.

2. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (1) includes performing semantic standardization of the recording channel in the following manner: The composition format for setting the semantics of the recording channel is: type phase_serial number, where the serial number can be omitted for relay protection devices that have only one set of three-phase current / voltage channels or only one set of three-phase current / voltage channels that need to participate in diagnosis; for relay protection devices with multiple sets of current / voltage channels, if their names contain numbers, the serial number is set to be consistent with the numbers, otherwise the serial number is incremented.

3. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (1) includes performing transient recording resampling processing in the following manner: Among them, x(n) represents the original sampling value at time n, y(t) represents the sampling value at time t after resampling, m represents the sliding window radius, ω represents the weight, and the sum of the weights of each point in the sliding window is equal to 1.

4. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The electrical quantity characteristic value described in step (2) includes a DC component, a fundamental component, a second harmonic component, a third harmonic component and a self-generated zero-sequence effective value, wherein the DC component, the fundamental component, the second harmonic component and the third harmonic component are calculated in the following manner: Where i(n) represents the channel sampling value, n ranges from {0,1,2,…,N-1}, and N is the total number of sampling points in one cycle; k represents the harmonic order, and ranges from {0,1,2,…,N-1}. The calculation formulas for the DC component I(0), fundamental component I(1), second harmonic component I(2), and third harmonic component I(3) are as follows: The self-generated zero-sequence effective value is the sum of the effective values ​​of the three-phase channels: I0(0)=I A (0)+I B (0)+I C (0) Among them, I0(0) represents the self-generated zero-sequence effective value, I A (0) I B (0) I C (0) are the effective values ​​of the three-phase channels A, B, and C respectively.

5. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (3) includes performing CT saturation diagnosis in the following manner: (3.1.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations; (3.1.2) Sampling window: 10ms to 50ms, i.e., from the half cycle after the mutation point to 2.5 cycles; (3.1.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection; (3.1.4) Identification method: a) Determine whether the maximum effective value in the time window is greater than the threshold. If so, perform CT saturation judgment, otherwise directly report normal; b) For the recordings that meet the diagnostic prerequisites, continue to determine whether the maximum value of the percentage of the second and third harmonics of the current channel in the sampling window to the fundamental content exceeds the threshold. If one of them exceeds the threshold, it is diagnosed as a CT saturation diagnosis abnormality.

6. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (3) includes performing CT-N disconnection diagnosis in the following manner: (3.2.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations; (3.2.2) Sampling window: 0ms to 40ms, i.e. two cycles after the mutation point; (3.2.3) Sampling channels: including the current channel of line protection, the current channels of each branch of busbar protection, and the current channels of each side of main transformer protection; (3.2.4) Identification method: a) Determine whether the current fault type is an asymmetric ground fault. If so, perform CT saturation judgment, otherwise the notification is not applicable; b) For line protection recordings that meet the diagnostic prerequisites, if the maximum effective value of its self-generated or external zero-sequence current in the sampling window is greater than 0.05In, it is judged to be normal, otherwise it is judged to be abnormal; c) For main transformer protection recordings that meet the diagnostic prerequisites, if the maximum effective values ​​of its self-generated and external zero-sequence current in the sampling window are both greater than or less than 0.05In, it is judged to be normal; that is, if the self-generated value is greater than the threshold and the external value is less than the threshold, the diagnosis is that the neutral point CT of the main transformer is broken; if the self-generated value is less than the threshold and the external value is greater than the threshold, the diagnosis is that the main transformer switch CT is broken.

7. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (3) includes performing CT-N two-point grounding diagnosis in the following manner: (3.3.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this substation and adjacent substations; (3.3.2) Sampling window: full range of recording; (3.3.3) Sampling channel: including external zero-sequence current channel and self-generated zero-sequence current channel; (3.3.4) Identification method: a) Determine whether the maximum effective values ​​of the two zero-sequence currents within the time window are zero-drifting values. If so, perform CT-N two-point grounding diagnosis, otherwise the notification is not applicable; b) Compare the effective values ​​of the self-generated zero-sequence current and the external zero-sequence current of the same recording point by point. When there are three consecutive points with effective value errors greater than 10%, it is diagnosed as CT-N two-point grounding.

8. The method for diagnosing hidden faults in a secondary sampling circuit based on transient recording data characteristics according to claim 1 is characterized in that: The step (3) includes performing PT-N high resistance diagnosis in the following manner: (3.4.1) Inspection scope of relay protection device: Select the recording files triggered at the same time point of this station and adjacent substations; (3.4.2) Sampling window: recording of the steady-state section before the fault starting point, i.e. recording the first cycle; (3.4.3) Sampling channels: including the voltage channel of line protection, the voltage channels of each busbar of busbar protection, and the voltage channels of each side of main transformer protection; (3.4.4) Identification method: a) Determine whether the first cycle of the recording is a steady-state segment. If so, perform PT-N high resistance diagnosis, otherwise the notification is not applicable; b) If the absolute value threshold of the third harmonic of any phase in the three-phase voltage channel is greater than 6V, it is directly diagnosed as PT-N high resistance.

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