Electric reactor arc short circuit fault early diagnosis method and system based on open triangular voltage waveform collapse characteristics

Abstract

The invention relates to an electric reactor arc short circuit fault early diagnosis method and system based on open triangular voltage waveform collapse characteristics. The method comprises the steps that open triangular voltage signals obtained by sequentially connecting the secondary sides of voltage transformers at the two ends of a three-phase series electric reactor in a high-voltage parallel capacitor bank are obtained in real time; sampling according to a preset sampling frequency, and calculating an open delta voltage change rate at adjacent sampling moments; when the absolute value of the voltage change rate at the current moment is greater than a preset threshold value and is different from the voltage change rate at the previous moment, judging that the waveform is abnormal once; and counting the cumulative number of waveform anomalies in the window during pre-design, and if the cumulative number is greater than a preset number limiting value, judging that an arc short circuit fault occurs in the series reactor and triggering an alarm. According to the invention, by analyzing the open triangular voltage waveform collapse abrupt change characteristics, accurate identification can be carried out at a slight short-circuit stage at the early stage of a fault, and the sensitivity and reliability of diagnosis are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of power detection technology, specifically relating to an early diagnosis method and system for arc short-circuit faults in reactors based on the characteristics of open delta voltage waveform sag. Background Technology

[0002] High-voltage parallel capacitor banks are important reactive power compensation devices in power grids. Dry-type air-core reactors, which are usually used in series with them, are used to suppress inrush current and low-frequency harmonics. In actual use, the inter-turn short-circuit fault conditions of these series reactors typically manifest as early inter-turn arc reignition short-circuit faults and mid-to-late-stage inter-turn fusion short-circuit faults.

[0003] In existing technologies, fault detection for dry-type air-core reactors mainly employs analytical calculation methods based on inductance characteristics, relay protection based on current amplitude, regular infrared inspections by operation and maintenance personnel, and monitoring methods for phase voltage and current phase angle deviation changes. However, in actual power grid operating environments, complex harmonic voltage interference is unavoidable on the background side of the power grid, and three-phase series reactors often have unbalanced initial parameters during manufacturing or installation.

[0004] Because early arc reignition short-circuit faults are extremely short-lived and have very weak electrical characteristics, traditional detection methods based on harmonic component extraction or phasor offset calculation are easily masked by the aforementioned background harmonic interference and initial parameter imbalances, leading to a significant reduction in detection sensitivity. When an early, weak inter-turn arc short circuit occurs inside a series reactor, existing methods struggle to accurately identify its actual operating state, easily resulting in missed or delayed detections, and failing to provide timely and effective protection before the fault escalates into a severe fusion short circuit.

[0005] Therefore, there is an urgent need for a solution that can overcome the effects of background harmonic interference and device parameter imbalance, and accurately identify and diagnose inter-turn arc short-circuit faults in reactors in their early stages. Summary of the Invention

[0006] One of the objectives of this invention is to at least solve one or more of the aforementioned problems existing in the prior art. In other words, one of the objectives of this invention is to provide an early diagnosis method and system for reactor arc short-circuit faults based on the open delta voltage waveform trap characteristics that meets one or more of the aforementioned requirements.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an early diagnosis method for arc short-circuit faults in reactors based on the open-delta voltage waveform sag characteristics, applicable to high-voltage parallel capacitor banks, comprising: Real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank; The open delta voltage signal is sampled according to a preset sampling frequency, and the voltage change rate of the open delta voltage signal at adjacent sampling times is calculated. Determine whether the absolute value of the voltage change rate at the current moment is greater than the preset change rate threshold. If so, and the voltage change rate at the current moment is of a different sign than the voltage change rate at the previous sampling moment, then determine that the open delta voltage signal at the current moment has a waveform abnormality. Start the preset timing window and count the cumulative number of waveform anomalies within the timing window; If the cumulative number of occurrences exceeds the preset limit, an arc short circuit fault is determined to have occurred inside the three-phase series reactor, and an alarm is triggered.

[0008] As a preferred embodiment, calculating the rate of change of the open delta voltage signal at adjacent sampling times includes: The voltage change is obtained by calculating the difference between the first voltage amplitude collected at the current moment and the second voltage amplitude collected at the previous sampling moment. Divide the voltage change by the sampling period corresponding to the preset sampling frequency to obtain the voltage change rate.

[0009] As a preferred implementation, after starting a preset timing window and counting the cumulative number of waveform anomalies within the timing window, the method further includes: If the cumulative count is less than or equal to the preset limit at the end of the timing window, the cumulative count will be cleared to zero, and the system will wait for the open delta voltage signal to show abnormal waveform again.

[0010] As a preferred embodiment, after calculating the rate of change of the open delta voltage signal at adjacent sampling times, the method further includes: Calculate the difference between the voltage change rate at the current moment and the voltage change rate at the previous sampling moment to obtain the slope change. The characteristics of the opening triangle voltage waveform trap are quantified based on three parameters: the change in opening voltage, the rate of change in voltage, and the change in slope between adjacent sampling times.

[0011] As a preferred embodiment, real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank includes: Collect the terminal voltage of each phase of the three-phase series reactor; The open delta voltage signal is obtained by physically connecting or vector summing the terminal voltages of each phase.

[0012] As a preferred embodiment, the preset timing window length and preset number of times are determined according to the specifications and voltage level of the high-voltage parallel capacitor bank.

[0013] As a preferred implementation, the preset sampling frequency is not less than 16kHz.

[0014] As a preferred implementation, the preset change rate threshold is 25, the time length of the timing window is 2 minutes, and the number of times is limited to 2000.

[0015] On the other hand, the present invention also provides an early diagnosis system for arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics, applied to high-voltage parallel capacitor banks, comprising: The voltage acquisition module is used to acquire the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank in real time. The data acquisition module, connected to the voltage acquisition module, is used to sample the open delta voltage signal according to a preset sampling frequency; The processor, connected to the data acquisition module, is used to calculate the voltage change rate of the open delta voltage signal at adjacent sampling times; determine whether the absolute value of the voltage change rate at the current time is greater than a preset change rate threshold; if so, and the voltage change rate at the current time is of a different sign than the voltage change rate at the previous sampling time, then determine that the open delta voltage signal at the current time has a waveform abnormality; and start a preset timing window and count the cumulative number of waveform abnormalities within the timing window. The alarm device is connected to the processor. When the cumulative number of alarms exceeds the preset limit, the processor determines that an arc short circuit fault has occurred inside the three-phase series reactor and controls the alarm device to trigger an alarm.

[0016] In a preferred embodiment, the voltage acquisition module includes voltage transformers connected in parallel across each phase of the three-phase series reactor, wherein the secondary windings of each phase voltage transformer are connected in an open delta voltage connection to output an open delta voltage signal.

[0017] Compared with the prior art, the method and system for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics provided by the present invention have the following beneficial effects: This invention acquires the open delta voltage signal of a three-phase series reactor in a high-voltage parallel capacitor bank and jointly monitors the voltage change rate of the open delta voltage signal at adjacent sampling times and the cumulative number of waveform anomalies within a preset timing window. This enables the diagnostic system to directly capture the instantaneous changes in reactor impedance caused by the periodic or non-periodic combustion of inter-turn arcs. Furthermore, it accurately extracts the waveform dips and amplitude abrupt changes in the open delta voltage caused by arc reignition and extinction, effectively eliminating the masking of weak fault signals by complex harmonic interference from the power grid background and the initial parameter imbalance of the three-phase series reactor. Ultimately, it achieves highly sensitive and highly anti-interference accurate identification and diagnostic protection in the early stages of inter-turn arc short-circuit faults in series reactors. Attached Figure Description

[0018] Figure 1 This is a flowchart of an early diagnosis method for reactor arc short-circuit faults based on the open delta voltage waveform trap characteristics, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the early diagnosis system for reactor arc short-circuit faults based on the open delta voltage waveform trap characteristics, according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the invention. Various processes or components may be appropriately omitted, substituted, or added to the various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0021] Reference Figure 1 This invention provides an early diagnosis method for arc short-circuit faults in reactors based on the characteristics of open-delta voltage waveform sag, applicable to high-voltage parallel capacitor banks. Specifically, the diagnostic method mainly includes the following steps: Step S100: Real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank; Step S200: Sample the open delta voltage signal according to the preset sampling frequency, and calculate the voltage change rate of the open delta voltage signal at adjacent sampling times. Step S300: Determine whether the absolute value of the voltage change rate at the current moment is greater than the preset change rate threshold. If so, and the voltage change rate at the current moment is of opposite sign to the voltage change rate at the previous sampling moment, then determine that the open delta voltage signal at the current moment has a waveform abnormality. Step S400: Start the preset timing window and count the cumulative number of waveform abnormalities within the timing window; In step S400, if the cumulative number of times exceeds the preset limit, it is determined that an arc short circuit fault has occurred inside the three-phase series reactor, and an alarm is triggered.

[0022] In one specific embodiment of the present invention, step S100, which involves real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank, may specifically include: Step S101: Collect the terminal voltage of each phase of the three-phase series reactor; Step S102: The open delta voltage signal is obtained by physically connecting or vector summing the terminal voltages of each phase.

[0023] This implementation method takes into account the direct calculation of the three-phase terminal voltage, which can effectively sever the coupling relationship with the capacitor terminal voltage. Therefore, it is beneficial to clearly and objectively reflect the operating status of the reactor body, thereby significantly improving the sensitivity and accuracy of subsequent fault diagnosis.

[0024] In one specific embodiment of the present invention, step S200 above, calculating the voltage change rate of the open delta voltage signal at adjacent sampling times, may specifically include: Step S201: Calculate the difference between the first voltage amplitude collected at the current time and the second voltage amplitude collected at the previous sampling time to obtain the voltage change. Step S202: Divide the voltage change by the sampling period corresponding to the preset sampling frequency to obtain the voltage change rate.

[0025] Specifically, steps S201 and S202 are calculated using the following formula:

[0026] in, Sampling time; This represents the amplitude of the opening voltage collected at the current moment; This represents the amplitude of the opening voltage collected at the previous moment; This represents the change in opening voltage between adjacent sampling times; This refers to the sampling time interval, i.e., the sampling period; This represents the rate of change of the opening voltage at adjacent sampling times.

[0027] The specific implementation of step S200 above, by calculating the degree of voltage fluctuation between adjacent discrete sampling points, helps to convert the minute waveform trap features that are difficult to detect in the time domain into slope change parameters that are easy for computer systems to recognize numerically, thereby laying a solid data foundation for the subsequent fault threshold identification mechanism.

[0028] In one specific embodiment of the present invention, after calculating the voltage change rate of the open delta voltage signal at adjacent sampling times in step 200, the method may further include the following steps: Step S203: Calculate the difference between the voltage change rate at the current moment and the voltage change rate at the previous sampling moment to obtain the slope change. Step S204: Based on three parameters—the change in opening voltage, the rate of change in voltage, and the change in slope—between adjacent sampling times, the trapping characteristics of the opening triangle voltage waveform are quantified.

[0029] This implementation takes into account that a single voltage change parameter is easily affected by conventional harmonics or operational fluctuations in a complex power grid context. Therefore, by comprehensively characterizing the voltage sag features by combining the voltage change and slope change, it is beneficial to improve the completeness of fault feature extraction, so as to improve the system's ability to resist background harmonic interference in a targeted manner.

[0030] Furthermore, in a specific embodiment of the present invention, in step S200 above, the open delta voltage signal is sampled according to a preset sampling frequency. Specifically, the preset sampling frequency can be configured to be no less than 16kHz, and the open delta voltage signal is collected in real time according to the preset sampling frequency.

[0031] This implementation takes into account the transient high-frequency characteristics of waveform sag caused by the early stage of inter-turn arc short-circuit faults. Therefore, it configures a high-frequency sampling rate of not less than 16kHz, which is conducive to the system accurately capturing waveform distortion details at the millisecond or even microsecond level and effectively avoiding early fault omissions due to insufficient sampling frequency.

[0032] In one specific embodiment of the present invention, after step S400 starts a preset timing window and counts the cumulative number of waveform abnormalities within the timing window, the method further includes: step S401, if at the end of the timing window the cumulative number is less than or equal to a preset limit, then the cumulative number is cleared to zero, and the open delta voltage signal is waited for waveform abnormalities to reappear.

[0033] This implementation takes into account the occasional abnormal jumps that may occur due to transient disturbances in the actual power grid operation. Therefore, a time-constrained reset mechanism is introduced, which helps to prevent the downstream protection alarm device from malfunctioning.

[0034] Furthermore, it should be noted that, in order to ensure the universal applicability and anti-interference capability of the diagnostic logic, in one specific embodiment of the present invention, some parameters in step S400 can be set by the following method: A fault diagnosis model is established using the controlled variable method. By adjusting the background harmonic content, the initial imbalance parameters of the three-phase series reactor, and the capacity and reactance of the high-voltage parallel capacitor bank, the preset timing window length and preset count limit are dynamically determined. In this implementation, by dynamically matching the threshold parameters with the hardware specifications, the system can not only resist the influence of background harmonic interference and the imbalance of the initial three-phase parameters of the device, but also enhance the universal applicability of this diagnostic method to various types of capacitor banks at different voltage levels.

[0035] Furthermore, it should be noted that, in order to clarify the applicable hardware boundaries of the diagnostic method in the embodiments of the present invention, in the above-described implementation of establishing the fault determination model and dynamic matching parameters, the voltage level of the power grid where the high-voltage parallel capacitor bank is located can be 10kV or 35kV; correspondingly, the specific specifications of the high-voltage parallel capacitor bank can be one of the following parameter combinations: a capacity of 3.6MVar and a reactance rate of 5%, a capacity of 3.6MVar and a reactance rate of 12%, a capacity of 4.8MVar and a reactance rate of 5%, or a capacity of 4.8MVar and a reactance rate of 12%.

[0036] It is understood that the 10kV and 35kV voltage levels listed above, as well as the four specific combinations of capacity and reactance, are only typical hardware specifications for simulation verification and example illustration. In actual engineering applications, the early diagnosis method and waveform trap feature extraction logic proposed in this invention can be equivalently extended to other voltage levels and other high-voltage parallel capacitor banks with other capacity and reactance specifications. This invention does not strictly limit the scope of protection in this regard.

[0037] Furthermore, as a specific application scenario parameter setting, in a specific embodiment of the present invention, in response to the specification of a voltage level of 10kV and a high-voltage parallel capacitor bank capacity of 3.6MVar and a reactance rate of 5%, some parameters in the above method S100-S400 can be specifically configured as follows: a preset change rate threshold of 25, a preset timing window duration of 2 minutes, and a preset number of times limit of 2000.

[0038] Based on the same inventive concept, this invention also provides an early diagnosis system for arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics. This system is applied to high-voltage parallel capacitor banks. The system includes a three-phase capacitor C and a three-phase series reactor, wherein the three-phase series reactor specifically includes three reactors L, each connected in series with the capacitor C.

[0039] The system also includes: The voltage acquisition module is connected in parallel with the reactors L of the three phases of the three-phase series reactor to acquire the open delta voltage signal of the three-phase series reactor in real time. The data acquisition module, electrically connected to the voltage acquisition module, is used to perform analog-to-digital conversion and sampling of the open delta voltage signal according to a preset sampling frequency; The processor, which communicates with the data acquisition module, is used to calculate the voltage change rate of the open delta voltage signal at adjacent sampling times; determine whether the absolute value of the voltage change rate at the current time is greater than a preset change rate threshold; if so, and the voltage change rate at the current time is of a different sign than the voltage change rate at the previous sampling time, then determine that the open delta voltage signal at the current time has a waveform abnormality; and start the internally preset timing window and count the cumulative number of waveform abnormalities within the timing window. The alarm device is electrically or communicatively connected to the processor. When the cumulative number of alarms exceeds a preset limit, the processor determines that an arc short circuit fault has occurred inside the three-phase series reactor and outputs a trigger level or alarm command to the alarm device to trigger an alarm.

[0040] like Figure 2 The diagram shown is a structural schematic of the system described above. It can be seen that the voltage acquisition module includes voltage transformers TV connected in parallel across each phase of the three-phase series reactor. The primary side of each phase voltage transformer is connected in parallel with the corresponding three-phase series reactor, and the secondary windings of each phase voltage transformer are connected in an open delta voltage connection, forming an open delta loop. The output of the open delta loop is directly connected to the microcontroller data acquisition system to output the open delta voltage signal to the data acquisition module. The control signal output pin of the microcontroller data acquisition system establishes a control connection with the subsequent alarm device.

[0041] In one specific embodiment of the present invention, the data acquisition module and the processor can be integrated and deployed in a microcontroller data acquisition system. Specifically, the data acquisition module includes an analog-to-digital converter (ADC) unit configured in the microcontroller data acquisition system. The signal input terminal of the ADC unit is electrically connected to the output terminal of an open delta circuit formed by the secondary windings of each phase voltage transformer. The processor includes the main control chip of the microcontroller data acquisition system.

[0042] 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.

[0043] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. An early diagnosis method for arc short-circuit faults in reactors based on the characteristics of open-delta voltage waveform sag, applied to high-voltage parallel capacitor banks, characterized in that... include: Real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank; The open-delta voltage signal is sampled according to a preset sampling frequency, and the voltage change rate of the open-delta voltage signal at adjacent sampling times is calculated. Determine whether the absolute value of the voltage change rate at the current moment is greater than a preset change rate threshold. If so, and the voltage change rate at the current moment has a different sign than the voltage change rate at the previous sampling moment, then determine that the open delta voltage signal at the current moment has a waveform abnormality. Start a preset timing window and count the cumulative number of waveform anomalies within the timing window; If the cumulative number of times exceeds the preset limit, it is determined that an arc short circuit fault has occurred inside the three-phase series reactor, and an alarm is triggered.

2. The method for early diagnosis of arc short-circuit faults in reactors based on the open-delta voltage waveform sag characteristics as described in claim 1, characterized in that, The calculation of the voltage change rate of the open-delta voltage signal at adjacent sampling times includes: The voltage change is obtained by calculating the difference between the first voltage amplitude collected at the current moment and the second voltage amplitude collected at the previous sampling moment; The voltage change rate is obtained by dividing the voltage change by the sampling period corresponding to the preset sampling frequency.

3. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, After starting the preset timing window and counting the cumulative number of waveform anomalies within the timing window, the method further includes: If the cumulative count is less than or equal to the preset count limit at the end of the timing window, the cumulative count is cleared to zero, and the system waits for the open delta voltage signal to show waveform abnormality again.

4. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, After calculating the rate of change of the open-delta voltage signal at adjacent sampling times, the method further includes: Calculate the difference between the voltage change rate at the current moment and the voltage change rate at the previous sampling moment to obtain the slope change. The characteristics of the opening triangle voltage waveform trap are quantified based on three parameters: the change in opening voltage between adjacent sampling times, the rate of change of voltage, and the change in slope.

5. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, The real-time acquisition of the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank includes: Collect the terminal voltage of each phase of the three-phase series reactor; The open delta voltage signal is obtained by physically connecting or vector summing the terminal voltages of each phase.

6. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, The preset timing window length and the preset number of times limit are determined according to the specifications and voltage level of the high-voltage parallel capacitor bank.

7. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, The preset sampling frequency is not less than 16kHz.

8. The method for early diagnosis of arc short-circuit faults in reactors based on the open delta voltage waveform sag characteristics as described in claim 1, characterized in that, The preset rate of change threshold is 25, the duration of the timing window is 2 minutes, and the number of times is limited to 2000.

9. An early diagnosis system for arc short-circuit faults in reactors based on the characteristics of open-delta voltage waveform sag, applied to high-voltage parallel capacitor banks, characterized in that, include: The voltage acquisition module is used to acquire the open delta voltage signal of the three-phase series reactor in the high-voltage parallel capacitor bank in real time. A data acquisition module, connected to the voltage acquisition module, is used to sample the open delta voltage signal according to a preset sampling frequency; The processor, connected to the data acquisition module, is used to calculate the voltage change rate of the open delta voltage signal at adjacent sampling times; determine whether the absolute value of the voltage change rate at the current time is greater than a preset change rate threshold; if so, and the voltage change rate at the current time is of a different sign than the voltage change rate at the previous sampling time, then determine that the open delta voltage signal at the current time has a waveform abnormality. In addition, a preset timing window is started, and the cumulative number of waveform anomalies within the timing window is counted; An alarm device, connected to the processor, determines that an arc short circuit fault has occurred inside the three-phase series reactor when the cumulative number of times exceeds a preset limit and controls the alarm device to trigger an alarm.

10. The early diagnosis system for reactor arc short-circuit faults based on the open delta voltage waveform sag characteristic according to claim 9, characterized in that, The voltage acquisition module includes voltage transformers connected in parallel across each phase of the three-phase series reactor. The secondary windings of the voltage transformers in each phase are connected in an open delta voltage connection to output the open delta voltage signal.

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