A fault detection method for pole-mounted switch station complete equipment

Abstract

The present application relates to power distribution equipment detection technical field, specifically to a kind of pole switch station complete equipment fault detection method.The present application is based on the real-time waveform data analysis of three-phase voltage, three-phase current and zero sequence component, generates primary circuit operation state report, simultaneously by actively injecting analog overload, low voltage and single-phase ground fault test signals to feeder terminal obtains uplink communication message, and analyzes uplink communication message to generate evaluation report, finally correlation analysis primary circuit operation state report and evaluation report;Realize the collaborative development of primary circuit state monitoring and feeder terminal function test, overcome the problem that both are separated in prior art, cannot judge fault reason.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment testing technology, specifically to a fault detection method for a complete set of equipment in a pole-mounted switch station. Background Technology

[0002] With the continuous improvement of the automation level of the power distribution network, pole-mounted switch stations and their supporting feeder terminals are key nodes for achieving fault isolation and self-healing. Their operational reliability is directly related to the power supply quality, so they need to be inspected regularly.

[0003] Existing technologies, such as Chinese invention patent publication number CN211905649U, disclose a hood-type portable FTU fault detection box. By introducing an adapter detection box, voltage and current circuits are measured on the terminal blocks using a multimeter or clamp meter without changing the original wiring method. Although this solves the risk of short circuits caused by densely packed connector pins, it is essentially still a passive, single-point, and static measurement method. It cannot simulate real fault conditions, nor can it actively test and evaluate the core functions of the feeder terminal, such as protection logic, measurement accuracy, and communication response.

[0004] Secondly, the primary circuit status monitoring and feeder terminal function testing are separate from each other, lacking collaborative analysis and failing to integrate historical data for diagnosis. This leads to discrepancies between test conditions and actual faults, and makes it difficult to accurately locate the cause of faults under complex conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and solve the problems of disconnect between primary circuit status monitoring and feeder terminal function testing, inability to simulate real fault signals for active testing, and lack of multi-source data correlation analysis and historical data fusion diagnostic capabilities.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a fault detection method for a complete set of equipment of pole-mounted switch station, including the following steps: S1, connecting the detection device and the feeder terminal, and synchronously collecting real-time waveform data of three-phase voltage, three-phase current and zero-sequence component.

[0007] S2. Analyze real-time waveform data to obtain fundamental amplitude, three-phase phase difference, total harmonic distortion rate and effective value of zero-sequence component, and generate a primary circuit operation status report accordingly.

[0008] S3. Start the programmable signal source of the detection device, and inject test signals simulating overload, low voltage and single-phase grounding fault into the feeder terminal in sequence, and record the uplink communication messages simultaneously.

[0009] S4. Parse the uplink communication message to obtain the measurement value and protection action event triggered by the test signal; calculate the relative error based on the instantaneous value and measurement value of the test signal, and check whether the type and timing of the protection action event match the injected test signal, and then generate an evaluation report.

[0010] S5. Associate the primary circuit operation status report and evaluation report, combine the historical operation data of the site to generate fault location conclusions, and output a structured detection report.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention generates a primary circuit operation status report based on real-time waveform data analysis of three-phase voltage, three-phase current and zero-sequence component. At the same time, it obtains uplink communication messages by actively injecting test signals simulating overload, low voltage and single-phase grounding faults into the feeder terminal, and generates an evaluation report by parsing the uplink communication messages. Finally, it correlates and analyzes the primary circuit operation status report and the evaluation report; it realizes the coordinated development of primary circuit status monitoring and feeder terminal functional testing, and overcomes the problem of separation between the two and inability to link them to determine the cause of the fault in the prior art.

[0012] 2. This invention simulates three typical power distribution network fault conditions: overload, low voltage, and single-phase grounding. It injects corresponding test signals into the feeder terminal and simultaneously collects its uplink communication messages. This verifies the feeder terminal's measurement response and protection behavior to various faults in a real communication environment, effectively improving the accuracy of feeder terminal function testing.

[0013] 3. This invention generates fault location conclusions and outputs structured inspection reports by correlating and analyzing the primary circuit operation status report and evaluation report, and combining the historical operation data of the site. This enables comprehensive judgment and accurate location of fault causes of complete sets of equipment in pole-mounted switch stations, overcoming the problems of vague fault diagnosis and difficult location caused by the lack of multi-source data fusion analysis in existing technologies. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the detection method of the present invention.

[0016] Figure 2 This is a schematic diagram of the process for generating a primary loop operation status report according to the present invention.

[0017] Figure 3This is a schematic diagram of the process for generating an evaluation report for this invention.

[0018] Figure 4 This is a flowchart illustrating the process of generating a conclusion on the cause of a fault in this invention. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0020] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0021] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] The following describes in detail, with reference to the accompanying drawings, a specific scheme for a fault detection method for a complete set of pole-mounted switchgear provided by the present invention.

[0024] Please see Figure 1 The diagram shows a flowchart of a fault detection method for a complete set of equipment for a pole-mounted switch station provided by the present invention, which specifically includes the following steps: Step S1, connect the detection device and the feeder terminal, and synchronously collect real-time waveform data of three-phase voltage, three-phase current and zero-sequence component.

[0025] In actual deployment, the detection device is physically connected to the secondary output terminals of the voltage and current transformers at the feeder terminal via its built-in multi-channel test signal input port. Simultaneously, the detection device acquires real-time waveform data of three-phase voltage, three-phase current, and zero-sequence components through its internally integrated high-speed synchronous sampling analog-to-digital converter.

[0026] Step S2: Analyze the real-time waveform data to obtain the fundamental amplitude, three-phase phase difference, total harmonic distortion rate and effective value of zero-sequence component, and generate a primary circuit operation status report accordingly.

[0027] Step S21 involves digital filtering and timing conversion of the real-time waveform data. Specifically, a Butterworth low-pass digital filter with a cutoff frequency of 3kHz is used to filter the original sampling sequence to suppress high-frequency noise and sampling aliasing interference. After filtering, the discrete sampling points are re-aligned according to their timestamps.

[0028] Step S22: Determine the whole period window to enable accurate spectrum analysis in the future.

[0029] The specific process is as follows: Select a phase voltage as a reference and detect its zero-crossing point from negative to positive. The zero-crossing point refers to the moment when the voltage waveform crosses the zero axis from the negative half-cycle to the positive half-cycle, and the voltage value at this moment is zero.

[0030] The zero-crossing detection algorithm can be as follows: when the product of the voltage values ​​of two adjacent sampling points is found to be less than or equal to zero, it is initially determined that there is a zero-crossing point between them; then, the precise zero-crossing point position is calculated between these two sampling points using linear interpolation.

[0031] Then, starting from the first zero-crossing point, subsequent zero-crossing points are continuously tracked; the time interval between two adjacent zero-crossing points is taken as the instantaneous power frequency cycle. If its deviation from the standard power frequency cycle does not exceed the preset deviation threshold, it indicates that the zero-crossing point is stable and effective, rather than a false zero-crossing point caused by noise interference, and is thus determined to be a valid zero-crossing point.

[0032] By determining the validity of the zero-crossing point, the stability of the captured signal segment is ensured, thus providing a reliable data foundation for subsequent spectrum analysis.

[0033] Finally, the time interval between two consecutive valid zero crossings is defined as the integer period window; the length of the integer period window is the instantaneous period of the current power frequency signal, which is used to ensure that subsequent spectrum analysis is carried out within a complete fundamental frequency period.

[0034] The standard power frequency period can be determined based on the nominal frequency of the power grid. For example, for a 50Hz system, the standard power frequency period is 20ms.

[0035] In practical applications, considering the slight fluctuations in power grid frequency, the preset deviation threshold can be set to ±1% of the standard power frequency cycle. In high-disturbance regions, it can be relaxed to ±1.5% to improve fault tolerance; in high-precision verification scenarios, it can be tightened to ±0.5% to obtain more stable cycle data.

[0036] If the full cycle window cannot be determined within the preset maximum waiting time, the standard power frequency cycle will be used as the full cycle window for subsequent analysis, and a waveform stability warning will be issued and recorded in the primary circuit operation status report.

[0037] Based on the fact that the recovery time for frequency disturbances in typical distribution networks is usually less than 2 seconds and the time requirement for rapid on-site diagnosis, the maximum waiting time is set to 2 seconds for example. Those skilled in the art can adjust it within the range of 1 to 5 seconds to balance waiting stability and response speed.

[0038] Step S23: Based on the whole cycle window, perform spectrum analysis on the time series data of each phase voltage and current to obtain the fundamental amplitude, three-phase phase difference, total harmonic distortion rate and effective value of zero sequence component.

[0039] Specifically, the process is as follows: First, within a defined integer period window, a Hanning window is applied to the timing data of each phase voltage and current to suppress spectral leakage. Then, a fast Fourier transform is performed to convert the time-domain signal to the frequency domain, thereby obtaining its complex spectrum.

[0040] Then, in the complex spectrum, the maximum value of the amplitude magnitude is searched. The frequency corresponding to the maximum value is the fundamental frequency of the signal, and the amplitude magnitude corresponding to the maximum value is the fundamental peak value. Next, the ratio of the fundamental peak value to the number of sampling points within the entire period window is calculated, and then this ratio is compared with... Multiplying these values ​​yields the fundamental amplitude of each phase voltage and current.

[0041] The argument of the complex spectrum value corresponding to the main frequency is the phase angle. Based on this, the phase difference can be obtained by calculating the difference between any two phase angles.

[0042] Furthermore, the harmonic amplitudes of each phase voltage and current are extracted; based on the calculation process of the fundamental amplitude, the effective values ​​of each harmonic are calculated in the same way, and the total effective value of harmonics is obtained from the root mean square value of each harmonic effective value. The ratio of the total effective value of harmonics to the fundamental amplitude is used as the total harmonic distortion rate.

[0043] During the analysis, if a phase current signal is missing due to a current transformer fault, loose wiring, or channel limitation of the detection device, that is, there is a phase current that is not directly collected, then based on the principle that the algebraic sum of the three-phase currents is zero, the instantaneous current value of the missing phase can be deduced by using the instantaneous current values ​​of the other two phases.

[0044] Next, based on the same instantaneous moment, the sum of the instantaneous values ​​of the three-phase currents is taken as the instantaneous value of the zero-sequence current, and the average of the instantaneous values ​​of the three-phase voltages is taken as the instantaneous value of the zero-sequence voltage. Then, the root mean square values ​​of the instantaneous values ​​of the zero-sequence voltage and the instantaneous values ​​of the zero-sequence current are calculated separately within the whole cycle window, and these are taken as the effective values ​​of the zero-sequence components.

[0045] Please see Figure 2 Step S24: Generate a primary circuit operation status report. Specifically, this includes: when the ratio of the maximum to the minimum amplitude of the three-phase voltage or current fundamental wave is greater than a preset ratio, it indicates that there is a significant imbalance in the system, such as uneven load distribution in the primary circuit, and then the voltage or current imbalance status is recorded.

[0046] If the ratio of the maximum value to the minimum value is less than or equal to the preset ratio, the unbalanced state is not recorded, meaning that the current three-phase voltage and current are considered to be within an acceptable balance range.

[0047] The preset ratio is set with reference to the national power quality standards. Under normal operating conditions of the power system, the negative sequence voltage imbalance should not exceed 2%, and for short periods, it should not exceed 4%. Converted to the ratio of the maximum to minimum phase voltage amplitude, this is approximately (1 + 2 × imbalance), i.e., 1.02-1.04. To allow for a certain margin and consider fluctuations in on-site measurements, the preset ratio can be taken as 1.15.

[0048] The three phase differences are arranged in order of magnitude. If the absolute value of the difference between any phase difference and the standard phase difference exceeds the preset tolerance, the phase sequence is recorded as abnormal; otherwise, the phase sequence is recorded as normal.

[0049] In a standard three-phase positive sequence system, the three phases lag by 120° sequentially, and the phase differences between any two phases should be 120°, 120°, and 120°, with the standard phase difference being 120°.

[0050] Given that the typical phase measurement error of high-precision power quality measurement devices does not exceed 1° to 2°, and industry standards require that the phase angle measurement error generally does not exceed 3°, a preset tolerance of 9° is set to ensure that normal measurement fluctuations can be effectively distinguished from actual phase sequence anomalies.

[0051] Next, the maximum value among the differences between each phase difference and the standard phase difference is marked as the phase deviation characteristic, and the phase voltage with the largest total harmonic distortion rate is marked as the voltage harmonic dominant phase.

[0052] Simultaneously, the harmonic order with the highest amplitude in each phase current is recorded as the characteristic harmonic distribution. If multiple harmonics in a certain phase current have the same or similar amplitudes, and all are at their highest, then all harmonic orders that reach the highest amplitude can be recorded.

[0053] Furthermore, considering that abnormal fluctuations in zero-sequence voltage are often associated with drops in the voltage of a certain phase, the correlation between zero-sequence voltage and three-phase voltage fluctuations is analyzed to provide an important basis for subsequent judgment on whether there is a single-phase grounding fault or an abnormal zero-sequence circuit.

[0054] The specific analysis process of correlation fluctuation is as follows: Based on multiple consecutive integer period windows, calculate the root mean square of the instantaneous value of zero-sequence voltage within each integer period window, and use it as the effective value of zero-sequence voltage.

[0055] In this invention, 5 to 10 consecutive whole-cycle windows can be used for analysis. This number captures the continuous trend of zero-sequence voltage and phase voltage changes without introducing too much historical data due to excessively long windows, thus affecting the timeliness of the judgment.

[0056] Subsequently, the effective value of zero-sequence voltage and the fundamental amplitude of three-phase voltage are arranged in chronological order to form the time series of effective value of zero-sequence voltage and the time series of fundamental amplitude of three-phase voltage, respectively.

[0057] Then, in the time series of the effective value of the zero-sequence voltage, the interval in which the value continuously and monotonically increases and the number of increasing points is not less than 2 is taken as the rising period; in the time series of the fundamental amplitude of the three-phase voltage, the interval in which the value continuously and monotonically decreases and the number of decreasing points is not less than 2 is taken as the falling period.

[0058] If any rising and falling period intersects on the time axis, it is considered a coincidence, indicating a possible single-phase ground fault, causing a voltage drop in the faulty phase and simultaneously triggering zero-sequence voltage. Therefore, a correlated fluctuation is determined to exist; otherwise, no correlated fluctuation is detected.

[0059] Finally, the primary circuit operation status report is constructed by integrating the voltage imbalance status, current imbalance status, phase sequence abnormality, phase sequence normality, phase deviation characteristics, voltage harmonic dominant phase, characteristic harmonic distribution and analysis results, as well as the fundamental amplitude, three-phase phase difference, total harmonic distortion rate and effective value of zero-sequence component. The primary circuit operation status report reflects the electrical operating health status of the primary circuit.

[0060] Step S3: Start the programmable signal source of the detection device, and sequentially inject test signals simulating overload, low voltage and single-phase grounding fault into the feeder terminal, and simultaneously record the uplink communication messages.

[0061] Overload, undervoltage, and single-phase grounding faults are the most common typical faults and abnormal operating conditions in pole-mounted switchgear. Among them, overload reflects the risk of long-term overcurrent in the line; undervoltage reflects power supply quality problems; and single-phase grounding faults are the most frequent type of fault in medium-voltage distribution networks.

[0062] In actual operation, the testing device has a built-in high-precision programmable signal source, which has the ability to independently control the output of three-phase voltage, three-phase current, and zero-sequence current. The testing process is executed sequentially according to the simulated overload, undervoltage, and single-phase grounding faults to avoid interference from multiple faults in the judgment logic.

[0063] Step S31: Simulate overload test. The specific process is as follows: The programmable signal source of the detection device outputs three-phase voltages containing rated frequency, standard phase, and normal phase sequence.

[0064] The rated frequency is determined based on the nominal frequency of the power grid, and is usually 50Hz. The standard phase refers to the standard phase relationship where the voltages of each phase differ by 120°.

[0065] At the same time, the output amplitude increases from the rated value to a three-phase current exceeding the overcurrent protection setting value according to a preset time gradient.

[0066] The rated value is the rated current of the secondary side of the current transformer, and its value is determined according to the transformer nameplate or design specifications. Common values ​​are 5A or 1A.

[0067] Overcurrent protection settings can be obtained from the actual protection setting sheet of the feeder terminal being monitored. This setting sheet is issued by the distribution network dispatching or maintenance department after being calculated and set according to parameters such as the line's short-circuit capacity and load characteristics. For example, if the setting sheet specifies that the overcurrent stage I protection setting is 6 times the rated current.

[0068] In this invention, the preset time gradient can be exemplarily set to 100ms / step to ensure that the current rises slowly to trigger the timed overcurrent protection, rather than a sudden surge.

[0069] Step S32: Simulate low voltage test. The specific process is as follows: The programmable signal source of the detection device outputs a three-phase current containing the rated frequency, standard phase, and normal phase sequence. The rated frequency and standard phase are as described above.

[0070] At the same time, the output amplitude decreases from the rated value to a three-phase voltage less than the undervoltage protection setting value according to a preset time gradient.

[0071] The rated value is the rated voltage of the secondary side of the voltage transformer, which is determined according to the transformer type and the nominal voltage of the system. For voltage transformers commonly used in 10kV systems, the rated line voltage of the secondary side is usually 100V.

[0072] The low voltage protection setting is also obtained from the actual protection setting sheet of the feeder terminal being tested. The preset time gradient is also set to 100ms / step.

[0073] Step S33: Simulate a single-phase ground fault test. The specific process is as follows: while keeping the voltages of the other two phases and the currents of the three phases at their corresponding rated values, reduce the fundamental amplitude of the selected phase voltage by a preset amplitude, and inject a zero-sequence current with a preset amplitude and phase to simulate the single-phase ground fault into the zero-sequence circuit.

[0074] This method reproduces the electrical characteristics of a single-phase ground fault, such as a voltage drop in one phase, the appearance of zero-sequence quantities, and a relatively unchanged voltage in the non-faulty phases, thereby effectively verifying the grounding protection function of the feeder terminal.

[0075] In simulation tests, to effectively assess the protection function, the preset amplitude is usually set to 30% to 80% of the rated value, thereby covering most cases from typical low-resistance grounding to medium-resistance grounding. In this invention, the preset amplitude can be exemplarily set to 50% of the rated value.

[0076] The preset amplitude is usually taken as 0.2 to 0.5 times the rated current. This range covers the common amplitude of zero-sequence current when a single phase is grounded in most medium-voltage distribution networks. In this invention, 0.3 times the rated current can be used as an example.

[0077] The zero-sequence current amplitude is theoretically equal to the fault point current, and its phase is opposite to the fault phase voltage when grounded. Therefore, in simulation tests, the phase of the injected zero-sequence current is usually set to be 180 degrees out of phase with the reduced fault phase voltage.

[0078] Throughout the entire process of injecting each test signal, the detection device synchronously listens to and records all uplink communication messages uploaded by the feeder terminal. Uplink communication messages refer to data frames actively sent or responded to by the feeder terminal during the test, according to the established communication protocol.

[0079] In addition, timestamps need to be added to each uplink communication message to accurately record the time when the message was generated, and the timestamps need to be associated with the corresponding test signal injection time so that the response time of the feeder terminal can be accurately evaluated later.

[0080] Please see Figure 3 Step S4: Parse the uplink communication message to obtain the measurement value and protection action event triggered by the test signal; calculate the relative error based on the instantaneous value and measurement value of the test signal, and check whether the type and timing of the protection action event match the injected test signal, and then generate an evaluation report.

[0081] The specific process is as follows: First, the uplink communication messages during each test period are filtered according to the timestamp and associated marker, and then decoded according to the feeder terminal communication protocol.

[0082] The feeder terminal communication protocol refers to a set of predefined rules for data interaction between feeder terminals and master or substations in a distribution network automation system. These rules include frame format, data type, and transmission rules. Specific details can be found in the equipment's technical specifications or communication protocol documents.

[0083] The decoding process is as follows: based on the definition of the feeder terminal communication protocol, the start bit, length, control field, address field, application service data unit and other information are identified from the received raw byte stream, and finally the specific data content carried by the uplink communication message is parsed out.

[0084] Next, measured values ​​of three-phase voltage, three-phase current, zero-sequence voltage, and zero-sequence current are extracted from the specific data. Alarm and trip events for overcurrent, undervoltage, and ground faults are also extracted as protection action events. The measured values, protection action events, and the type and timing of the injected test signals are then correlated.

[0085] Then, based on the instantaneous value of the test signal output by the programmable signal source, the following error calculations and type and timing checks are performed.

[0086] The error calculation process is as follows: In each test, the corresponding item is selected from the measured values. Specifically, the overload test selects three-phase current, the undervoltage test selects three-phase voltage, and the single-phase ground fault test selects zero-sequence voltage and zero-sequence current. Then, the absolute difference between the selected item and the corresponding benchmark is divided by the benchmark to obtain the relative error.

[0087] The type and timing verification is as follows: by comparing the extracted protection action event types with the current test type, it is verified whether the protection action event types meet the following matching relationship: overload test matches overcurrent event; undervoltage test matches undervoltage event; single-phase ground fault test matches grounding event.

[0088] If the protection action event type matches the relationship, it indicates that the protection logic of the feeder terminal is correct in terms of type identification; if the protection action event type does not match the relationship, it is determined that the protection logic configuration is incorrect.

[0089] At the same time, check whether the time difference between the timestamp of the protection action event and the corresponding test signal injection time exceeds the preset limit in order to evaluate the response speed.

[0090] If the time difference exceeds the preset limit, it indicates a timing abnormality, which may be due to sampling delay or logic processing lag; otherwise, it indicates that the response timing is normal.

[0091] The preset limit is usually set to protection setting delay ±20ms to distinguish between normal operation and abnormal delay. The protection setting refers to the action time setting value of the protection device, which is determined by the field operation procedure. For example, the overcurrent stage II setting delay is 0.3s.

[0092] It is also necessary to simultaneously verify whether the alarm timestamp in the same test is earlier than the trip timestamp. The normal protection sequence should be alarm first and then trip. If the sequence is reversed or the time difference between the two is negative, it indicates that there is a fault in the protection action event recording mechanism; otherwise, it indicates that the protection action event recording sequence is correct.

[0093] The timestamp refers to the moment when an alarm or tripping event is recorded by the feeder terminal and prepared for transmission.

[0094] Finally, the measured values, relative errors, protection action events, and verification results are summarized to generate an evaluation report. The evaluation report reflects the measurement accuracy, protection function correctness, and timeliness of the feeder terminal.

[0095] Step S5: Associate the primary circuit operation status report and evaluation report, combine the historical operation data of the site to generate a conclusion on the cause of the fault, and output a structured test report.

[0096] Please see Figure 4The process of generating a conclusion on the cause of the fault is as follows: First, the primary circuit operation status report generated immediately after this test is aligned with the evaluation report in terms of time.

[0097] Based on this, if there is a voltage or current imbalance in the primary circuit operation status report, the absolute value of the relative error of the corresponding phase in the evaluation report is greater than the absolute value of the maximum relative error in similar historical tests and the error direction is consistent; the error direction refers to the sign of the relative error.

[0098] At this point, it indicates that there may be an asymmetry in the primary circuit, and the secondary circuit of the corresponding phase also has problems, such as aging of the transformer core or increased contact resistance of the secondary wiring; therefore, it is determined that the characteristics of the primary transformer are deviated or the wiring is loose.

[0099] Otherwise, it may be due to temporary asymmetric fluctuations in the primary circuit itself, rather than a problem with the measurement circuit, and therefore it is not considered a equipment failure.

[0100] If the primary circuit operation status report shows abnormal phase sequence or phase deviation characteristics, and the protection action in the evaluation report is delayed but the type is correct, it indicates that the zero-crossing detection is offset due to a phase error, affecting the phase-based protection algorithm and causing the delay; therefore, it is determined that the feeder terminal sampling phase calibration has failed.

[0101] Otherwise, the phase abnormality may only be caused by momentary interference or external primary circuit wiring error, and the sampling logic of the feeder terminal itself is not disordered, so it is not judged as a calibration failure.

[0102] Among them, protection action delay refers to the time difference between the timestamp of the protection action event and the injection time exceeding a preset limit.

[0103] If there are correlated fluctuations in the primary circuit operation status report, and the single-phase grounding test protection action is missing or incorrect in the assessment report, it indicates that a suspected grounding feature has appeared during the operation of the primary circuit, but the protection function of the feeder terminal has not responded correctly; therefore, it is determined to be a zero-sequence current loop disconnection or grounding fault detection logic failure.

[0104] Otherwise, it indicates that there may have been a momentary grounding or interference in the primary circuit, but the feeder terminal is functioning normally and is not considered a fault.

[0105] If the same type of fault is found multiple times in the site's historical operation data, it will be marked as a recurring fault in this judgment, and the operation and maintenance personnel will be prompted to focus on investigating persistent problems.

[0106] If this is the first time it has occurred, the conclusion of this judgment will be adopted; at the same time, in order to assess the urgency of the fault, corresponding characteristic data, such as total harmonic distortion rate and phase difference, will be extracted from the primary circuit operation status report.

[0107] Then, extract the historical sequence of this feature data from the site's historical operational data. If the absolute difference between this feature data and the average of the historical sequence exceeds a preset value, it indicates that the current anomaly has significantly deviated from the site's historical norm, belonging to a low-probability serious deviation event, and there is a risk of rapid deterioration.

[0108] Therefore, an urgency indicator is added to this assessment to remind maintenance personnel to prioritize serious issues that may lead to rapid deterioration. If the absolute difference does not exceed the preset value, it indicates that although the current anomaly is the first of its kind, its severity is still within the historical fluctuation range, and the urgency is relatively low, so no special indicator is needed.

[0109] In this invention, based on statistical principles, the preset value can be exemplarily taken as twice the standard deviation of the historical mean. For example, if the historical total harmonic distortion rate has a mean of 2.0% and a standard deviation of 0.3%, then the preset value is 0.6%.

[0110] Finally, all judgment conclusions are summarized as the fault cause determination conclusion. A structured inspection report is output and displayed locally and synchronized remotely. The structured inspection report consists of a report header, a primary circuit status summary table, a feeder terminal performance evaluation table, a fault cause determination conclusion table, and a raw data index.

[0111] The report header includes the site identifier, testing time, and testing device information. The primary circuit status summary table visually displays the content of the primary circuit operation status report. The feeder terminal performance evaluation table visually displays the content of the evaluation report.

[0112] The fault cause determination table displays the judgment conclusions item by item. The raw data index provides the storage identifiers for the real-time waveform data, uplink communication messages and related timestamps and associated markers of this test, ensuring the traceability and verifiability of the test process.

[0113] The following is a summary table of the local primary loop states, as shown in Table 1.

[0114]

[0115] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0116] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0117] In addition, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0118] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0119] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting a fault in a pole-mounted switchgear station, characterized by, The method comprises the following steps: S1, connecting the detection device with the feeder terminal, and synchronously collecting real-time waveform data of three-phase voltage, three-phase current and zero sequence component; S2, analyzing the real-time waveform data to obtain fundamental wave amplitude, three-phase phase difference, total harmonic distortion rate and zero sequence component effective value, and generating a primary circuit operation state report accordingly; S3, starting the program-controlled signal source of the detection device, sequentially injecting test signals of simulated overload, low voltage and single-phase grounding fault into the feeder terminal, and synchronously recording the uplink communication messages; S4, analyzing the uplink communication messages to obtain the measurement values triggered by the test signals and the protection action events; Based on the instantaneous values of the test signals and the measurement values, the relative errors are calculated, and it is checked whether the types and time sequences of the protection action events match the injected test signals, and then an evaluation report is generated; S5, associating the primary circuit operation state report with the evaluation report, combining the historical operation data of the station to generate a fault cause determination conclusion, and outputting a structured detection report; The test signals of simulated overload, low voltage and single-phase grounding fault are sequentially injected; wherein the test signal of simulated overload is three-phase voltage containing rated frequency, standard phase and normal phase sequence, and three-phase current with amplitude increasing from rated value to over-current protection setting value according to a preset time gradient; the test signal of simulated low voltage is three-phase current containing rated frequency, standard phase and normal phase sequence, and three-phase voltage with amplitude decreasing from rated value to less than low voltage protection setting value according to a preset time gradient; the test signal of simulated single-phase grounding fault is that under the condition of keeping the voltage and three-phase current of the remaining two phases as corresponding rated values, the fundamental wave amplitude of the selected phase voltage is reduced by a preset amplitude, and a zero sequence current with a preset amplitude and phase is injected into the zero sequence loop to simulate the single-phase grounding fault; all uplink communication messages are synchronously listened to and recorded during the injection of each test signal, a time stamp is added to each uplink communication message, and the time stamp is associated with the injection time of the corresponding test signal; According to the time stamp and the association mark, the uplink communication messages during each test period are screened, and are decoded according to the communication protocol of the feeder terminal; the measurement values including three-phase voltage, three-phase current, zero sequence voltage and zero sequence current are extracted, and the alarm and tripping events of over-current, low voltage and grounding fault are extracted as protection action events, which are associated with the type and injection time of the injected test signal; The instantaneous values of the test signals output by the program-controlled signal source are taken as the reference; in each test, the corresponding item is selected from the measurement values, the absolute difference between the selected item and the corresponding reference is divided by the reference to obtain the relative error; it is checked whether the type of the protection action event matches the matching relationship: overload test matches over-current event; low voltage test matches low voltage event; single-phase grounding fault test matches grounding event; it is checked whether the time difference between the time stamp of the protection action event and the corresponding injection time exceeds the preset limit value; it is checked whether the alarm time stamp is earlier than the tripping time stamp in the same test; the measurement values, relative errors, protection action events and checking results are summarized to generate an evaluation report; Based on the primary circuit operation state report and the evaluation report of this detection: if there is a voltage or current imbalance state, the absolute value of the relative error of the corresponding phase in the evaluation report is greater than the absolute value of the maximum relative error in the historical test of the same type and the error direction is consistent, it is determined that the primary side mutual inductor characteristic is deviated or the connection is loose; if there is a phase sequence abnormality or phase deviation feature, and the protection action is delayed but the type is correct, it is determined that the sampling phase calibration of the feeder terminal fails; if there is a correlation fluctuation, and the single-phase grounding test protection action is missing or the type is wrong, it is determined that the zero sequence current loop is disconnected or the grounding fault detection logic is faulty; if there are multiple similar faults in the historical operation data of the station, mark the repeated fault in the conclusion of this determination; if it appears for the first time, use the conclusion of this determination, and extract the corresponding feature data from the primary circuit operation state report, if the absolute difference between the feature data and the historical sequence average value exceeds the preset value, add the fault urgency identifier to the conclusion of this determination; summarize all the determination conclusions as the fault cause determination conclusion.

2. The method of claim 1, wherein the method further comprises: The analysis process of the real-time waveform data is: Perform digital filtering and time sequence conversion on the real-time waveform data; based on the whole cycle window, perform frequency spectrum analysis on the time sequence data of each phase voltage and current, identify the main frequency and extract the amplitude as the fundamental wave amplitude; Extract the phase angle from each phase main frequency, calculate the difference between any two phase angles to obtain the phase difference; Extract the amplitude of each harmonic of each phase voltage and current, calculate the total effective value of the harmonics, and take the ratio of the total harmonic distortion rate to the fundamental wave amplitude; Based on the same time, the sum of the three-phase current instantaneous values is taken as the zero sequence current instantaneous value, and the average of the three-phase voltage instantaneous values is taken as the zero sequence voltage instantaneous value; Calculate the root mean square value of the zero sequence voltage instantaneous value and the zero sequence current instantaneous value in the whole cycle window respectively as the zero sequence component effective value.

3. The pole-mounted switch station complete equipment fault detection method according to claim 2, characterized in that, The determination process of the whole cycle window is: Select a phase voltage as a reference and detect its zero-crossing point from negative to positive; Start from the first zero-crossing point and continuously track the subsequent zero-crossing points; The time period between adjacent two zero-crossing points is taken as the instantaneous power frequency period, if the deviation of the time period from the standard power frequency period does not exceed the preset deviation threshold, it is determined as an effective zero-crossing point; The time period between two continuous effective zero-crossing points is defined as the whole cycle window.

4. The pole-mounted switch station complete equipment fault detection method according to claim 2, characterized in that, The generation process of the primary circuit operation state report is: When the ratio of the maximum value to the minimum value of the three-phase voltage or current fundamental wave amplitude is greater than the preset proportion, record the voltage or current imbalance state; Arrange the three-phase phase differences in size, if the absolute value of the difference between any phase difference and the standard phase difference exceeds the preset tolerance, record the phase sequence abnormality, otherwise record the phase sequence normality; Mark the maximum value of the difference between each phase difference and the standard phase difference as the phase deviation feature; mark the phase voltage with the maximum total harmonic distortion rate as the voltage harmonic dominant phase; Record the harmonic order with the highest amplitude in each phase current as the characteristic harmonic distribution; analyze the correlation fluctuation of the zero sequence voltage and the three-phase voltage; The integrated voltage unbalance state, current unbalance state, phase sequence abnormality, phase sequence normality, phase deviation feature, voltage harmonic dominant phase, feature harmonic distribution and analysis result, and the fundamental amplitude, three-phase phase difference, total harmonic distortion rate and effective value of zero sequence component constitute a primary circuit operation state report.

5. The pole-mounted switch station complete equipment fault detection method according to claim 4, characterized in that, The correlation fluctuation of the analysis of the zero sequence voltage and the three-phase voltage is specifically: Based on a plurality of continuous integral cycle windows, the root mean square of the instantaneous value of the zero sequence voltage in each integral cycle window is calculated as the effective value of the zero sequence voltage, and a time sequence of the effective value of the zero sequence voltage is formed; and a time sequence of the fundamental amplitude of the three-phase voltage is formed synchronously; If the rising period of the effective value of the zero sequence voltage coincides with the falling period of the fundamental amplitude of any phase voltage, it is determined that there is a correlation fluctuation; otherwise, it is determined that no correlation fluctuation is found.

6. The pole-mounted switch station complete equipment fault detection method according to claim 1, characterized in that, The structured detection report includes a report header, a primary circuit state summary table, a feeder terminal performance evaluation table, a fault cause determination conclusion table and an original data index; The report header includes site identification, detection time and detection device information; the original data index provides storage identification of real-time waveform data, uplink communication messages and related time stamps, and correlation markers of this detection.

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