Electric leakage detection alarm method and system of distribution box

Abstract

The invention provides an electric leakage detection alarm method and system for a distribution box. The method comprises the steps of collecting zero-sequence current signals of all branches; dividing a fundamental wave region, a low-frequency harmonic region and a high-frequency harmonic region, and calculating the energy ratio of each frequency band; identifying higher harmonic interference based on the high-frequency energy ratio; a load type is determined through an equipment identification module, and a zero-sequence current tolerance interval is generated in combination with a preset model; according to the invention, the zero-sequence current tolerance model associated with the equipment type is constructed, the equipment identification module and the model generation module are combined, and the dynamic zero-sequence current tolerance interval is generated according to the information of the equipment type, the rated parameter, the grounding mode and the operation cycle, and is used as an important basis for judging whether the electric leakage behavior belongs to a normal working condition or not. When the actual detection value is in the tolerance interval, even if the zero-sequence current level is high, the system can correctly identify the state as a non-fault state, so that the problem of false alarm or alarm dead zone is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of leakage detection and alarm, and particularly to a leakage detection and alarm method and system for a distribution box. Background Art

[0002] With the continuous development of distribution automation and intelligent monitoring technologies, leakage detection and alarm systems have been widely applied to various distribution boxes to achieve real-time monitoring of the insulation status of lines and the risk of personal electric shock. The leakage detection methods of traditional distribution boxes mainly rely on residual current operated protective devices or online detection modules, and judge whether there are potential leakage hazards by collecting the residual current in the main line or branch circuits. However, in the actual application process, there are still many technical bottlenecks in the existing technologies, which are difficult to meet the requirements of high reliability and low misjudgment in complex power usage environments. On the one hand, a large number of non-linear load devices such as frequency converters and rectifiers are used in the power distribution system, which will introduce high-order harmonic interference signals, making the current transformers or detection circuits in the leakage detection devices vulnerable to interference and prone to malfunction. On the other hand, most of the existing leakage detection systems do not fully consider the leakage characteristics of the electrical equipment itself and the influence of additional filters. In some scenarios, equipment aging, insulation degradation or unreasonable structural design will generate non-negligible leakage current of the equipment body. At the same time, passive filters, capacitor compensation devices, etc. added to improve the power quality will also form a leakage path to the ground during operation, resulting in an increase in the overall residual current level, thereby causing system misjudgment or even alarm dead zones.

[0003] Therefore, a leakage detection and alarm method and system for a distribution box are proposed. Summary of the Invention

[0004] In view of this, the present invention provides a leakage detection and alarm method and system for a distribution box to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial option.

[0005] The technical solution of the present invention is implemented as follows: A leakage detection and alarm method for a distribution box includes S1. Set a plurality of zero-sequence current transformers at the main incoming line and key branches of the distribution box to collect zero-sequence current signals of each loop, and synchronously sample the zero-sequence current signals at a sampling frequency higher than 10 kHz. S2. Input the collected zero-sequence current signals into a spectrum analysis module, perform a fast Fourier transform, extract the fundamental wave and the amplitudes of each harmonic in the frequency components, and calculate the proportion of the spectrum energy of each frequency section. S3. Judge whether there is high-order harmonic interference in the current zero-sequence current according to the distribution characteristics of the spectrum energy. If the proportion of the high-frequency components in the spectrum energy is abnormal, mark it as an interference-type leakage event. The method for judging whether there is high - order harmonic interference includes: When the proportion of the energy in the high - frequency harmonic region in the total energy of the zero - sequence current is greater than 30%, and the proportion of the energy in the fundamental - wave region is less than 50%, it is determined that the current zero - sequence current is affected by high - frequency harmonic interference; The marking of the interference - type leakage event is used to exclude the periodic data in the subsequent alarm judgment to prevent false alarms; S4. Identify the types of electrical equipment connected to each branch circuit in the distribution box, and call the corresponding equipment leakage - current tolerance model to generate the tolerance interval of the residual current of the electrical equipment in the current state; The equipment leakage - current tolerance model is generated according to the preset equipment type, rated current, operating duration, and grounding method; Output a pair of upper and lower threshold values by looking up a table or interpolation to form the zero - sequence current tolerance interval corresponding to the equipment, which is used to determine the acceptable range of the zero - sequence current when the equipment is operating normally; When the effective value of the currently collected zero - sequence current is within the zero - sequence current tolerance interval, it is recognized as the normal leakage behavior of the equipment itself; S5. Compare the effective value of the zero - sequence current in the current cycle with the tolerance interval. If the effective value of the zero - sequence current is within the tolerance interval, it is determined as the leakage behavior of the equipment itself and no alarm is triggered; S6. Dynamically adjust the leakage alarm current threshold according to the type, spectral energy, and volatility of the near - term historical data of the identified equipment; The method for dynamically adjusting the leakage alarm current threshold includes: Perform variance calculation on the effective values of the zero - sequence current collected in multiple consecutive detection cycles within the last five minutes; If the variance value is less than the preset stability threshold, indicating that the current is stable, the current leakage alarm current threshold is increased by 5%; if the growth rate of the residual current between any two adjacent detection cycles is greater than 1 mA / s, or the proportion of high - frequency harmonics in the corresponding spectrum increases by more than 20%, the leakage alarm current threshold is decreased by 10%; S7. Adopt composite judgment. When the following conditions are met in multiple consecutive detection cycles: The effective value of the zero - sequence current exceeds the current leakage alarm current threshold, its spectrum is mainly composed of the fundamental wave and does not belong to the tolerance interval, then output a fault leakage alarm signal and trigger the alarm response module; The alarm judgment process includes the following judgment steps: Step S71. Judge whether the zero - sequence current in the current cycle exceeds the dynamically adjusted leakage alarm current threshold; Step S72. Judge whether the proportion of the fundamental - wave energy in the zero - sequence current spectrum is higher than 60%; Step S73. Judge whether the current zero - sequence current is outside the equipment leakage - current tolerance interval; When the above three conditions are all satisfied within three consecutive sampling periods, a fault leakage alarm signal is output, and the local acoustic-optic alarm module and the remote communication alarm module are triggered synchronously.

[0006] Further preferably, in step S2, the spectral energy is divided by frequency intervals into: a fundamental wave region from 45 Hz to 55 Hz, a low-frequency harmonic region from 100 Hz to 250 Hz, and a high-frequency harmonic region from 250 Hz to 2500 Hz; Calculate the spectral energy corresponding to the three frequency bands respectively, and calculate the proportion of the spectral energy in the total spectral energy of the zero-sequence current, including: a. The total energy of the zero-sequence current is the sum of the squares of the amplitudes of all frequency points after Fourier transform; b. The energy of the fundamental wave region is the sum of the squares of the amplitudes of each frequency point within 45 Hz to 55 Hz; c. The energy of the low-frequency harmonic region is the sum of the squares of the amplitudes of the frequency points within the range of 100 Hz to 250 Hz; d. The energy of the high-frequency harmonic region is the sum of the squares of the amplitudes of the frequency points within the range of 250 Hz to 2500 Hz; Divide the energies of the three frequency bands by the total energy of the zero-sequence current, and calculate the proportion of the fundamental wave energy, the proportion of the low-frequency harmonic energy, and the proportion of the high-frequency harmonic energy respectively.

[0007] The proportion of the spectral energy is used to judge whether there is high-order harmonic interference in the current zero-sequence current.

[0008] Further preferably, in step S7, the composite judgment further includes using a sliding window to analyze the change trend of the zero-sequence current within three consecutive sampling periods; If it is detected that the zero-sequence current continues to rise, and the proportion of the fundamental wave energy in these three periods is higher than 60%, and the zero-sequence current is not within the tolerance interval of the equipment, it is determined that this leakage behavior is a fault leakage, output a fault leakage alarm signal, and transmit a signal to the alarm response module.

[0009] The present invention also provides a system for a leakage detection and alarm method of a distribution box, and the system includes: a current sampling module, which is used to sample the current signals of multiple circuits in the distribution box to obtain zero-sequence current signals; a spectral analysis module, connected to the current sampling module, which is used to perform a fast Fourier transform on the zero-sequence current signal, extract the fundamental wave and each order of harmonics, and calculate the spectral energy distribution; a device identification module, which is used to identify the types of electrical equipment connected to each circuit; a model generation module, connected to the device identification module, which is used to generate a zero-sequence current tolerance interval corresponding to the device; A threshold adjustment module, connected to the spectrum analysis module and the model generation module, for dynamically adjusting the alarm current threshold; An alarm judgment module, connected to the spectrum analysis module, the model generation module and the threshold adjustment module, for judging whether the alarm condition is satisfied and outputting an alarm signal when the condition is satisfied; An alarm execution module, connected to the alarm judgment module, for triggering an audible and visual alarm and remote notification according to the alarm signal.

[0010] Due to the adoption of the above technical solutions in the embodiments of the present invention, it has the following advantages: First, in the leakage detection method of the present invention, through the judgment of high-frequency harmonic energy, combined with the frequency component extraction and energy division based on the fast Fourier transform in the spectrum analysis module, it can effectively identify the high-order harmonic interference signals introduced by non-linear loads in the zero-sequence current signal. When the energy ratio in the high-frequency harmonic region exceeds the set threshold and the fundamental wave energy ratio is relatively low, that is, mark this period as an interference-type leakage event, and automatically exclude the subsequent alarm judgment path, thereby avoiding false alarms.

[0011] Second, the present invention generates a dynamic zero-sequence current tolerance interval by constructing a zero-sequence current tolerance model associated with the device type, combining the device identification module and the model generation module, according to the information of the device type, rated parameters, grounding method and operating cycle, as an important basis for judging whether the leakage behavior belongs to the normal working condition. When the actual detected value is within this tolerance interval, even if the zero-sequence current level is relatively high, the system can correctly identify it as a non-fault state, thereby avoiding false alarms or alarm dead zones.

[0012] The above summary is only for the purpose of the specification and is not intended to be limiting in any way. In addition to the above-described illustrative aspects, embodiments and features, further aspects, embodiments and features of the present invention will be readily apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] Figure 1 is the step flow chart of the present invention; Figure 2 is the system architecture diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] In the following text, only some exemplary embodiments are briefly described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0016] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] As Figure 1-2 shown, the embodiments of the present invention provide a method and system for detecting and alarming leakage of a distribution box, including: The overall deployment of the distribution box leakage detection and alarm system provided in this embodiment is in the low-voltage power distribution system, applicable to multi-branch distribution boxes in residential, commercial, and industrial scenarios, used to monitor the power consumption status of each branch in real time, identify high-order harmonic interference, extract key spectrum information, and build a leakage capacitance tolerance model in combination with the operating characteristics of load devices to achieve fault leakage determination and real-time alarm response; The overall module composition of this system: current sampling module, spectrum analysis module, device identification module, model generation module, threshold adjustment module, alarm judgment module, alarm execution module; Current sampling module, the current sampling module is responsible for synchronously sampling the current signals of the main incoming line and each branch in the distribution box. The live wire and neutral wire of each branch pass through a zero-sequence current transformer (using a differential-mode current transformer), and the detected zero-sequence current is output as an analog signal through the zero-sequence current transformer; The sampling frequency is set to be higher than 10 kHz, meeting the coverage requirements for power frequency (50 Hz) and high-order harmonics (up to 2500 Hz), ensuring sufficient resolution and bandwidth support in the subsequent Fourier spectrum transformation process. The synchronous sampling data of multiple zero-sequence current transformers is collected through an ADC with synchronous sampling trigger to ensure that branch data is not lost; Spectrum analysis module, the zero-sequence current signal output by the current sampling module enters the spectrum analysis module in frames. By using the fast Fourier transform (FFT) algorithm, the amplitude of the frequency components of each frame of the signal in the range of 0 to 2500 Hz is calculated, and the spectrum energy section is divided accordingly. The specific division method is as follows: Fundamental wave region: 45 to 55 Hz, used to detect the main power frequency component; Low-frequency harmonic region: 100 to 250 Hz, mainly reflecting the energy distribution of the 2nd to 5th harmonics; High-frequency harmonic region: 250 to 2500 Hz, used to identify interference caused by non-linear devices such as variable frequency drives.

[0018] The energies of the three frequency bands are calculated by summing the squared amplitudes of the corresponding frequency points, and then the ratios of the fundamental wave energy, low-frequency harmonic energy, and high-frequency harmonic energy to the total spectrum energy of the zero-sequence current are calculated, which are used as the input features for subsequent interference identification and leakage type judgment. The spectrum analysis module uses an embedded FFT acceleration core or a high-performance ARM / DSP for calculation to achieve millisecond-level real-time spectrum analysis, which is suitable for continuous real-time leakage monitoring scenarios.

[0019] The device identification module. Each sampling channel corresponds one-to-one with a specific branch in the distribution box. The sampling signal is bound to the load device connected to the target branch through hardware address coding, initialization configuration table, or identification logic during operation. For example, branch 1 is connected to the lighting circuit, branch 2 is connected to the variable-frequency air conditioner, and branch 3 is connected to the motor.

[0020] The device identification module comprehensively judges the device type based on the device's number information, rated current, operation periodicity, or historical data volatility.

[0021] The model generation module. After the device type is identified, it generates by calling the built-in leakage tolerance model to model the residual current range of each type of device under normal working conditions. The generation parameters of the leakage tolerance model include: Device type (such as motor, LED driver), rated current (such as 10A, 32A), grounding method (such as TT, TN-C), operation duration (used to judge the aging trend); The leakage tolerance model outputs a pair of upper and lower limits of the zero-sequence current threshold to form the device tolerance interval, which is used to judge whether the current leakage behavior of the device is normal subsequently. The leakage tolerance model can be quickly matched by looking up a table or generated in the device database using linear interpolation. For the same type of device, template reuse is also supported.

[0022] The threshold adjustment module is responsible for continuously and dynamically adjusting the leakage alarm current threshold during actual operation to avoid false alarms or missed alarms caused by a fixed threshold. The threshold adjustment module performs real-time analysis based on the historical effective value sequence of the zero-sequence current within the sliding window, including: When the variance of the effective value in 50 sampling periods within 5 minutes of the sliding window is less than the "stationarity threshold", it is considered that the current fluctuation is stable, and the leakage alarm current threshold can be increased by +5%; If the growth rate of the effective value between two consecutive periods is detected to be greater than 1mA / s, or the high-frequency harmonic ratio suddenly increases by more than 20%, the leakage alarm current threshold will be decreased by -10%; The threshold adjustment is executed periodically, and the result is refreshed every 60 seconds, ensuring that the system has an adaptive ability under different power grid qualities and operating environments.

[0023] An alarm judgment module performs three composite judgments based on the spectrum analysis result, the tolerance model interval, and the current threshold: Judge whether the zero-sequence current in the current cycle exceeds the leakage alarm current threshold after dynamic adjustment; Judge whether the proportion of fundamental wave energy in the zero-sequence current spectrum is higher than 60%; Judge whether the current zero-sequence current is outside the equipment leakage capacitance tolerance interval.

[0024] When the above three conditions are all met in three consecutive detection cycles, it is determined that the leakage behavior is faulty, an alarm signal is output, and short-time current fluctuations, switch interference, or equipment errors are effectively filtered out.

[0025] An alarm execution module, after the alarm signal is output, immediately performs the following operations: Activate the local audible and visual alarm module, the buzzer emits a high-frequency alarm sound, and the red flash light is lit; Upload the alarm event to the background platform through the communication interface (supporting RS485, LoRa, Ethernet); The alarm information includes: branch number, equipment type, effective value of zero-sequence current, energy proportion of each frequency band, zero-sequence current tolerance interval, and judgment result, and the alarm information is locally stored and remotely synchronized through the remote communication alarm module.

[0026] In this embodiment, the specific working process: After the system is started, the current sampling module continuously samples the zero-sequence current signal from each branch, with a frequency of not less than 10 kHz to ensure signal fidelity; Send the sampled signal to the spectrum analysis module, and obtain each frequency component through fast Fourier transform; Divide the spectrum into three energy sections, and calculate the energy and proportion respectively; If the proportion of high-frequency harmonic energy exceeds 30% and the proportion of fundamental wave energy is lower than 50%, it is marked as a high-order harmonic interference event, and subsequent alarm judgments are not triggered; If it is a normal spectrum structure, enter the equipment identification link to determine the type of equipment connected to the branch; Query or generate an equipment tolerance model to obtain the tolerance interval of the current zero-sequence current; Judge whether the zero-sequence current exceeds the tolerance range; If it has exceeded, execute the alarm judgment logic in combination with the trend and spectrum proportion; If the three alarm judgment conditions are met in three consecutive cycles, trigger the alarm execution module; The alarm execution module controls the audible and visual device to sound, and at the same time uploads the alarm signal and diagnostic data to the remote system.

[0027] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various changes or substitutions, and these should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described.

Claims

1. A method for detecting and alarming leakage of a distribution box, characterized in that: Including S1. Install multiple zero-sequence current transformers at the main incoming line and key branches of the distribution box to collect zero-sequence current signals of each loop, and synchronously sample the zero-sequence current signals at a sampling frequency higher than 10 kHz; S2. Input the collected zero-sequence current signals into the spectrum analysis module, perform fast Fourier transform, extract the fundamental wave and the amplitudes of each harmonic in the frequency components, and calculate the proportion of the spectrum energy in each frequency section; S3. Judge whether there is high-order harmonic interference in the current zero-sequence current according to the distribution characteristics of the spectrum energy. If the proportion of the high-frequency components in the spectrum energy is abnormal, it is marked as an interference-type leakage event; S4. Identify the types of electrical equipment connected to each branch circuit in the distribution box, and call the corresponding equipment leakage capacitance tolerance model to generate the tolerance interval of the residual current under the current state of the electrical equipment; S5. Compare the effective value of the zero-sequence current in the current cycle with the tolerance interval. If the effective value of the zero-sequence current is within the tolerance interval, it is determined as the leakage behavior of the equipment itself and the alarm is not triggered; S6. Dynamically adjust the leakage alarm current threshold according to the type of the identified equipment, the spectrum energy and the volatility of the historical data in the recent period; S7. Adopt composite judgment. When the following conditions are met in multiple consecutive detection cycles: The effective value of the zero-sequence current exceeds the current leakage alarm current threshold, its spectrum energy is mainly the fundamental wave and does not belong to the tolerance interval, then output a fault leakage alarm signal and trigger the alarm response module.

2. The leakage detection and alarm method for a distribution box according to claim 1, wherein: In step S2, the spectrum energy is divided into frequency intervals as follows: Fundamental wave region: 45 Hz to 55 Hz, low-frequency harmonic region: 100 Hz to 250 Hz, and high-frequency harmonic region: 250 Hz to 2500 Hz; Calculate the spectrum energy corresponding to the three frequency bands respectively, and calculate the proportion of the spectrum energy in the total spectrum energy of the zero-sequence current, including: a. The total energy of the zero-sequence current is the sum of the squares of the amplitudes of all frequency points after Fourier transform; b. The energy of the fundamental wave region is the sum of the squares of the amplitudes of each frequency point within 45 Hz to 55 Hz; c. The energy of the low-frequency harmonic region is the sum of the squares of the amplitudes of the frequency points within the range of 100 Hz to 250 Hz; d. The energy of the high-frequency harmonic region is the sum of the squares of the amplitudes of the frequency points within the range of 250 Hz to 2500 Hz; Divide the energies of the three frequency bands by the total energy of the zero-sequence current to calculate the fundamental wave energy proportion, low-frequency harmonic energy proportion and high-frequency harmonic energy proportion respectively; The proportion of the spectrum energy is used to judge whether there is high-order harmonic interference in the current zero-sequence current.

3. A leakage detection and alarm method for a distribution box according to claim 1, characterized in that: In step S3, the method for judging whether there is high-order harmonic interference includes: When the proportion of the energy of the high-frequency harmonic region in the total energy of the zero-sequence current is greater than 30% and the proportion of the energy of the fundamental wave region is less than 50%, it is determined that the current zero-sequence current is affected by high-frequency harmonic interference; The marking of the interference-type leakage event is used to exclude the data of this cycle in the subsequent alarm judgment to prevent false alarms.

4. A leakage detection and alarm method for a distribution box according to claim 1, characterized in that: In step S4, the equipment leakage capacitance tolerance model is generated according to the preset equipment type, rated current, operation duration and grounding method; Output a pair of upper and lower limit thresholds by looking up tables or interpolation methods to form the zero-sequence current tolerance interval corresponding to the equipment, which is used to judge the acceptable range of the zero-sequence current when the equipment is in normal operation; When the effective value of the currently collected zero-sequence current is within the zero-sequence current tolerance range, it is recognized as a normal leakage behavior of the device itself.

5. A method for detecting and alarming leakage of a distribution box according to claim 1, characterized in that: In step S6, the method for dynamically adjusting the leakage alarm current threshold includes: Performing variance calculation on the effective values of the zero-sequence current collected in multiple consecutive detection periods within the last five minutes; If the variance value is less than the preset stability threshold, indicating that the current is stable, then increase the current leakage alarm current threshold by 5%; if the growth rate of the residual current between any two adjacent detection periods is greater than 1 mA / s, or the proportion of high-frequency harmonics in the corresponding spectrum increases by more than 20%, then decrease the leakage alarm current threshold by 10%.

6. A leakage detection and alarm method for a distribution box according to claim 1, characterized in that: In step S7, the composite judgment further includes using a sliding window to analyze the change trend of the zero-sequence current within three consecutive sampling periods; If it is detected that the zero-sequence current continues to rise, and the proportion of the fundamental wave energy in these three periods is higher than 60%, and the zero-sequence current is not within the device tolerance range, then it is determined that this leakage behavior is a faulty leakage, output a faulty leakage alarm signal, and transmit a signal to the alarm response module.

7. A leakage detection and alarm method for a distribution box according to claim 1, characterized in that: In step S7, the judgment process includes: Step S71: Judge whether the zero-sequence current in the current period exceeds the dynamically adjusted leakage alarm current threshold; Step S72: Judge whether the proportion of the fundamental wave energy in the zero-sequence current spectrum is higher than 60%; Step S73: Judge whether the current zero-sequence current is outside the device leakage capacitance tolerance range; When the above three conditions are all met within three consecutive sampling periods, then output a faulty leakage alarm signal, and synchronously trigger the local sound and light alarm module and the remote communication alarm module.

8. A system for a leakage detection and alarm method of a distribution box according to any one of claims 1-7, characterized in that, The system includes: A current sampling module for sampling the current signals of multiple circuits in the distribution box to obtain zero-sequence current signals; A spectrum analysis module connected to the current sampling module for performing a fast Fourier transform on the zero-sequence current signal, extracting the fundamental wave and each order of harmonics, and calculating the spectrum energy distribution; A device identification module for identifying the types of electrical equipment connected to each circuit; A model generation module connected to the device identification module for generating the zero-sequence current tolerance range corresponding to the device; A threshold adjustment module connected to the spectrum analysis module and the model generation module for dynamically adjusting the alarm current threshold; An alarm judgment module connected to the spectrum analysis module, the model generation module and the threshold adjustment module for judging whether the alarm conditions are met and outputting an alarm signal when the conditions are met; An alarm execution module connected to the alarm judgment module for triggering sound and light alarms and remote notifications according to the alarm signal.

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