Low-voltage line zero line live-line fault on-line monitoring device and method

Abstract

The invention discloses a low-voltage line zero line live-line fault on-line monitoring device and method. The device comprises a current measurement module, a relay gateway and an on-line monitoring terminal. The current measurement module comprises four groups of independent split core type current transformers which are respectively and correspondingly connected with three-phase leads and zero line leads of the low-voltage distribution line and are used for acquiring three-phase current values and zero line current values in real time; the relay gateway is connected with the current measurement module through a wireless communication link, is internally provided with an unbalance degree calculation unit, and is used for summing absolute difference values of a three-phase current value and a zero line current value to obtain a total unbalance degree and comparing the total unbalance degree with a preset safety threshold value in real time; the on-line monitoring terminal receives a fault determination signal of the relay gateway through the mobile communication network and triggers the alarm device and the remote operation and maintenance platform to give an alarm.

Description

Technical Field

[0001] This application relates to the field of power system safety monitoring technology, and in particular to an online monitoring device and method for live faults in the neutral wire of a low-voltage line. Background Technology

[0002] Today, with the widespread application of industrial and residential electrical equipment, the safe and stable operation of low-voltage power distribution networks is particularly crucial. However, abnormally energized neutral wires in these systems occur frequently, potentially leading to serious consequences: endangering operator safety, causing abnormal equipment damage, and even disrupting production processes. Therefore, quickly identifying and eliminating potential neutral wire energization hazards is a core element in ensuring personnel and equipment safety and maintaining production continuity.

[0003] In the industry, troubleshooting such faults mainly relies on manual methods using neon tube test pens. While this method is simple to operate, it has significant drawbacks: it requires manually checking each system circuit one by one, and then using experience to deduce the source of the fault, which is time-consuming and labor-intensive; the judgment results are highly dependent on the operator's skill level, and oversights or misdiagnoses are prone to occur; and the testing requires contact with live conductors, especially when the neutral wire is abnormally energized, which significantly increases the risk of electric shock.

[0004] Therefore, there is an urgent need to develop new detection technologies and devices to significantly improve screening efficiency and operational safety, simplify work processes, reduce potential safety risks at the source, and meet the urgent needs of current practical application scenarios. Summary of the Invention

[0005] This application provides an online monitoring device and method for live faults in the neutral wire of low-voltage lines to solve the above-mentioned problems.

[0006] On one hand, this application provides an online monitoring device for live neutral wire faults in low-voltage lines. The device includes: a current measurement module, a relay gateway, and an online monitoring terminal. The current measurement module contains four sets of independent clamp-on current transformers, which are respectively connected to the three-phase conductors and the neutral conductor of the low-voltage distribution line, for real-time acquisition of three-phase current values ​​and neutral wire current values. The relay gateway is connected to the current measurement module through a wireless communication link and has a built-in unbalance calculation unit, which is used to sum the absolute differences between the three-phase current values ​​and the neutral wire current values ​​to obtain the total unbalance, and compare the total unbalance with a preset safety threshold in real time. The online monitoring terminal receives the fault judgment signal from the relay gateway through a mobile communication network and triggers alarm devices and remote operation and maintenance platforms.

[0007] In one implementation of this application, the current measurement module further includes a sequentially connected signal conditioning chain. The output terminal of the secondary side of the current transformer is connected to a differential amplifier circuit to enhance the amplitude of the weak current signal. The output terminal of the differential amplifier circuit is connected to a bandpass filter circuit, which adopts a second-order active filter topology, and the passband covers the power frequency and its harmonic range. The output terminal of the filter circuit is connected to a multi-channel analog-to-digital converter for high-resolution synchronous sampling. The output terminal of the analog-to-digital converter is connected to a microcontroller, which has a built-in digital signal processing algorithm to extract the effective value of the current. The microcontroller transmits data through a low-power wireless communication module.

[0008] In one implementation of this application, the differential amplifier circuit adopts an instrumentation amplifier architecture, the gain factor is set by an external adjustable resistor, and an electromagnetic compatibility shielding structure is integrated; the bandpass filter circuit is implemented based on a Sallen-Key topology, the operational amplifier adopts a dual power supply mode, and the feedback network is configured with temperature stability components.

[0009] In one implementation of this application, the relay gateway has a built-in distributed time synchronization protocol to broadcast precise timestamps to each current measurement module, forcing multiple modules to perform sampling under a unified time base; the fault determination unit adopts a sliding time window analysis mechanism to calculate the total imbalance of multiple consecutive power frequency cycles by moving average, and sets the duration of continuous over-limit as a fault confirmation condition to eliminate false judgments due to instantaneous interference.

[0010] In one implementation of this application, the online monitoring terminal integrates a multi-mode communication interface to support interconnection between cellular mobile networks and substation monitoring systems; the online monitoring terminal has a built-in fault database that associates line topology information and automatically generates fault location maps; the online monitoring terminal also includes a protection linkage unit configured with programmable logic to trigger a circuit breaker tripping command when a neutral line energization fault is confirmed.

[0011] On the other hand, this application also provides an online monitoring method for live faults in the neutral wire of low-voltage lines, the method comprising: Step S1: The relay gateway sends a time synchronization command to the distributed current measurement module; Step S2: Each current measurement module acquires the instantaneous values ​​of the three-phase current and neutral current under the synchronous time base, calculates the effective value of the current after signal conditioning, and transmits it back. Step S3: The relay gateway performs vector differential calculation on the three-phase current value and the neutral current value to generate the total unbalance index; Step S4: Determine the neutral wire live fault based on the continuous over-limit behavior of the total imbalance index, and encrypt and transmit the alarm information to the online monitoring terminal.

[0012] In one implementation of this application, the signal conditioning process in step S2 includes: The output signal of the current transformer is proportionally amplified by an instrumentation amplifier. The amplified signal is input into a second-order active bandpass filter to suppress out-of-band noise. The filtered output signal is digitized by a high-resolution analog-to-digital converter; The microcontroller uses frequency domain analysis to extract the fundamental component of the current and calculate its effective value.

[0013] In one implementation of this application, the fault determination logic in step S4 includes a dynamic threshold optimization mechanism, specifically: Set a basic threshold based on the historical load curve of the line; Incorporate ambient temperature sensor data to compensate for threshold offset; Automatically adjust threshold sensitivity based on electricity consumption period characteristics; After the fault is resolved, a threshold self-learning report is generated to optimize the parameters.

[0014] The online monitoring device and method for live faults in the neutral wire of low-voltage lines provided in this application have the following beneficial effects: (1) Synchronous acquisition of three-phase and neutral current is achieved through four sets of independent clamp-on current transformers. A precision signal chain is constructed by combining an instrumentation amplifier (AD620) and a 16-bit high-resolution ADC (AD7606), which significantly improves the measurement accuracy of weak currents. A second-order active bandpass filter (30-500Hz) effectively suppresses power frequency harmonic interference, improves the signal-to-noise ratio by more than 30dB, and ensures that the current effective value extraction error is <1%. This design can accurately capture transient leakage current and solve the problem of high misjudgment rate in traditional manual detection.

[0015] (2) The relay gateway uses a distributed time synchronization protocol to force multiple nodes to uniformly sample the time base and eliminate phase deviation; it calculates the total imbalance (ΔI=Σ|Ix-In|) of the continuous power frequency cycle based on a sliding time window and combines it with a threshold for the duration of continuous over-limit to determine the fault. This algorithm can filter out instantaneous interference (such as surge current) and only triggers an alarm when the abnormality lasts for more than a set time (such as 200ms), reducing the false alarm rate and greatly improving the reliability of diagnosis.

[0016] (3) The online monitoring terminal integrates dynamic threshold optimization and protection linkage functions: it adaptively adjusts the threshold sensitivity based on historical load curves, ambient temperature, and electricity consumption period characteristics to achieve accurate fault location; at the same time, it links the remote operation and maintenance platform and circuit breaker tripping system through the cellular network, triggering an audible and visual alarm and automatically cutting off the power supply within 200ms after fault confirmation. Combined with the self-learning mechanism to generate a threshold optimization report, the operation and maintenance response efficiency is improved, and the risks of manual live operation are completely avoided. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 An architecture diagram of an online monitoring device for live faults in the neutral wire of a low-voltage line provided in this application embodiment; Figure 2 A three-dimensional diagram of a single current measurement component provided in an embodiment of this application; Figure 3 This is a diagram illustrating the internal architecture of a single current measurement component provided in an embodiment of this application. Figure 4 A power supply circuit diagram for the current measurement component provided in an embodiment of this application; Figure 5 This is a circuit diagram of the signal amplification circuit of the current measurement component provided in an embodiment of this application; Figure 6 A filter circuit diagram of the current measurement component provided in an embodiment of this application; Figure 7 A circuit diagram of an analog-to-digital conversion component for a current measurement component provided in an embodiment of this application; Figure 8 Circuit diagram of the communication module of the current measurement component provided in the embodiments of this application; Figure 9 A flowchart illustrating a single monitoring of a live neutral line fault in a low-voltage power distribution network, as provided in this application embodiment. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] This application provides an online monitoring device and method for live faults in the neutral wire of a low-voltage line. The technical solution proposed in this application will be described in detail below with reference to the accompanying drawings.

[0020] Figure 1 This application provides an architecture diagram of an online monitoring device for live faults in the neutral wire of a low-voltage line. Figure 1 As shown, the equipment includes: four current measurement modules, one relay gateway, and one online monitoring terminal. The current measurement modules CTA, CTB, CTC, and CTN are responsible for measuring the currents flowing through phases A, B, C, and N of the line. The measurement results are, in order, I... a Ib I c .

[0021] The working principle is as follows: the measurement data is transmitted to the relay gateway via the communication module on the measurement component. The relay gateway is responsible for calculating the imbalance between the three-phase currents A, B, and C and the N-phase current, ΔI. a =abs(I a -I n ), ΔI b =abs(I a -In) and ΔI c =abs(I c -In). ΔI=ΔI a +ΔI b +ΔI c If ΔI is greater than the set threshold ΔI th If this occurs, a three-phase current imbalance exists, and the system can determine that there is a leakage current or a line damage fault. The measured current value and the judgment result are transmitted to the online monitoring terminal via a 4G antenna to prompt engineers to maintain the line.

[0022] In this embodiment of the application, a three-dimensional diagram of a single current measurement component is shown below. Figure 2 As shown, its internal structure is as follows Figure 3 As shown, it consists of four parts: power supply, signal sampling and processing, central control, and data interaction and storage.

[0023] In the embodiments of this application, the power supply circuit (see...) Figure 4 It is powered by a lithium battery, with its negative terminal grounded and the positive terminal led out to power supply V-BAT via a fuse. To stabilize the voltage and filter out noise, a 10μF tantalum electrolytic capacitor is connected in parallel between V-BAT and ground. The signal acquisition and processing stage includes a current transformer (CT), a signal amplification circuit, a filtering circuit, and an analog-to-digital converter (ADC) module.

[0024] Signal amplifier circuit (see) Figure 5 The AD620 differential amplifier was selected to effectively amplify the weak current transformer signal to a range that the subsequent acquisition unit could process. The AD620 offers advantages such as high accuracy, low noise, high common-mode rejection ratio (CMRR), low linearity error, high input impedance, and ease of use, making it ideal for weak signal amplification. Its gain is set by a single resistor connected between pins 1 and 8. Given that the system needs to detect a 50Hz power frequency signal, a bandpass filter with a center frequency of 50Hz was subsequently configured for signal extraction.

[0025] A second-order bandpass filter was designed using a Sallen-Key topology (see...). Figure 6The bandwidth covers 30Hz to 500Hz. The circuit uses a ±5V powered NE5532 dual operational amplifier to achieve a second-order Butterworth response, with a theoretical stopband attenuation rate of -40dB / decathlon.

[0026] The analog-to-digital converter (ADC) circuit is a crucial component of the hardware; its conversion speed and accuracy directly affect the accuracy of subsequent signal processing, thus determining the current detection result. Since the microcontroller's built-in ADC cannot meet the speed and accuracy requirements, an external high-performance ADC chip, AD7606 (see...), is selected. Figure 7 This chip offers 7 channels, 16-bit resolution input, and operates from a single 5V supply to reduce power consumption, with a sampling rate of up to 200 kSPS per channel. Its ±5V analog input range supports signal frequencies up to 22kHz, fully meeting system requirements.

[0027] The core controller of the system uses the MSP430 microcontroller, which is known for its ultra-low power consumption, flexible operating modes and strong processing capabilities.

[0028] The data interaction and storage section consists of a wireless communication module and a storage unit. Considering factors such as low power consumption, a simple data format, and peripheral circuit design, the nRF24L01 chip was selected as the wireless transceiver core. This module operates in the 2.4GHz ISM band, supports transmission rates up to 2 Mbps, and has extremely low power consumption. The specific circuit design of the wireless communication module is as follows... Figure 8 As shown.

[0029] The online monitoring system for live neutral wire faults in low-voltage lines relies on a hardware platform and also requires the development of appropriate software programs to implement control functions. The entire system's monitoring process for live neutral wire faults in low-voltage lines is as follows: Figure 9 As shown. First, the relay gateway sends a time synchronization command to each current measurement component to ensure that each current measurement component measures the current value in the line simultaneously. After receiving the time synchronization command, each current measurement component samples the current value of the phase it is responsible for and sends it to the relay gateway in sequence. The relay gateway determines whether a neutral wire energization fault has occurred based on a set threshold. If a fault occurs, it reports the "fault" status to the online monitoring terminal. If no fault occurs, it ends and waits for the next data collection.

[0030] The three-phase current and neutral current imbalance algorithm (ΔI=Σ|Ix-In|) determines leakage / line damage faults in real time by setting a threshold ΔIth, effectively solving the problems of low efficiency and high misjudgment rate of traditional manual inspection; it adopts a high-precision signal chain of AD620 differential amplifier + AD7606 16-bit ADC, supports 22kHz wideband signal acquisition, and combined with 200kSPS high-speed sampling capability, it can capture transient fault current; the Sallen-Key second-order bandpass filter (30-500Hz) combined with -40dB / decade stopband attenuation significantly enhances the anti-interference of 50Hz power frequency signal, and improves the signal-to-noise ratio by 30dB.

[0031] The above describes an online monitoring device for live neutral wire faults in low-voltage lines, provided by an embodiment of this application. Based on the same inventive concept, this application also provides an online monitoring method for live neutral wire faults in low-voltage lines, the method comprising: Step S1: The relay gateway sends a time synchronization command to the distributed current measurement module; Step S2: Each current measurement module acquires the instantaneous values ​​of the three-phase current and neutral current under the synchronous time base, calculates the effective value of the current after signal conditioning, and transmits it back. Step S3: The relay gateway performs vector differential calculation on the three-phase current value and the neutral current value to generate the total unbalance index; Step S4: Determine the neutral wire live fault based on the continuous over-limit behavior of the total imbalance index, and encrypt and transmit the alarm information to the online monitoring terminal.

[0032] In this application, the signal conditioning process in step S2 includes: The output signal of the current transformer is proportionally amplified by an instrumentation amplifier. The amplified signal is input into a second-order active bandpass filter to suppress out-of-band noise. The filtered output signal is digitized by a high-resolution analog-to-digital converter; The microcontroller uses frequency domain analysis to extract the fundamental component of the current and calculate its effective value.

[0033] In this application, the fault determination logic in step S4 includes a dynamic threshold optimization mechanism, specifically: Set a basic threshold based on the historical load curve of the line; Incorporate ambient temperature sensor data to compensate for threshold offset; Automatically adjust threshold sensitivity based on electricity consumption period characteristics; After the fault is resolved, a threshold self-learning report is generated to optimize the parameters.

[0034] The specific embodiments of this application are as follows: The current measurement components CTA / CTB / CTC are clamped to phase lines A / B / C respectively, and CTN is clamped to the neutral line (N phase), ensuring the air gap of the current transformer is closed (error < 0.5mm). The relay gateway is fixed in a central position ≤ 200m away from the measurement components and connected to a 220V mains backup power supply. The monitoring terminal is deployed in the operation and maintenance center and equipped with a 4G SIM card and a data receiving server.

[0035] The software configuration process is as follows: First, the relay gateway sends a time synchronization command to each current measurement component to determine that each current measurement component measures the current value in the line at the same time. After the current measurement component receives the time synchronization command, each current measurement component samples the current value of the phase it is responsible for and sends it to the relay gateway in sequence.

[0036] The relay gateway is responsible for calculating the imbalance between the three-phase currents A, B, and C and the N-phase current, ΔI. a =abs(I a -I n ), ΔI b =abs(I a -In) and ΔI c =abs(I c -In). ΔI=ΔI a +ΔI b +ΔI c If ΔI is greater than the set threshold ΔI th If there is an imbalance in the three-phase current, the system can determine that there is a leakage current or a line damage fault.

[0037] If a fault occurs, the system will report the "fault" status to the online monitoring terminal. If no fault occurs, the system will stop and wait for the next data collection.

[0038] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0039] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An online monitoring device for live faults in the neutral wire of a low-voltage line, characterized in that, The device includes: a current measurement module, a relay gateway, and an online monitoring terminal; the current measurement module contains four sets of independent clamp-on current transformers, which are respectively connected to the three-phase conductors and the neutral conductor of the low-voltage distribution line, for real-time acquisition of the three-phase current value and the neutral conductor current value; the relay gateway is connected to the current measurement module through a wireless communication link, and has a built-in unbalance calculation unit, which is used to sum the absolute differences between the three-phase current value and the neutral conductor current value to obtain the total unbalance, and compare the total unbalance with a preset safety threshold in real time; the online monitoring terminal receives the fault judgment signal from the relay gateway through a mobile communication network and triggers alarm devices and remote operation and maintenance platform alarms.

2. The online monitoring device for live faults in the neutral wire of a low-voltage line according to claim 1, characterized in that, The current measurement module also includes a sequentially connected signal conditioning chain. The output terminal of the secondary side of the current transformer is connected to a differential amplifier circuit to enhance the amplitude of weak current signals. The output terminal of the differential amplifier circuit is connected to a bandpass filter circuit, which adopts a second-order active filter topology and covers the power frequency and its harmonic range. The output terminal of the filter circuit is connected to a multi-channel analog-to-digital converter for high-resolution synchronous sampling. The output of the analog-to-digital converter is connected to a microcontroller, which has a built-in digital signal processing algorithm to extract the effective value of the current. The microcontroller transmits data via a low-power wireless communication module.

3. The online monitoring device for live faults in the neutral wire of a low-voltage line according to claim 2, characterized in that, The differential amplifier circuit adopts an instrumentation amplifier architecture, with the gain factor set by an external adjustable resistor and an integrated electromagnetic compatibility shielding structure; the bandpass filter circuit is implemented based on a Sallen-Key topology, the operational amplifier adopts a dual power supply mode, and the feedback network is configured with temperature stability components.

4. The online monitoring device for live faults in the neutral wire of a low-voltage line according to claim 1, characterized in that, The relay gateway has a built-in distributed time synchronization protocol that broadcasts precise timestamps to each current measurement module, forcing multiple modules to perform sampling under a unified time base. The fault determination unit adopts a sliding time window analysis mechanism to calculate the total imbalance over multiple consecutive power frequency cycles using a moving average, and sets the duration of continuous over-limit as a fault confirmation condition to eliminate false judgments due to instantaneous interference.

5. The online monitoring device for live faults in the neutral wire of a low-voltage line according to claim 1, characterized in that, The online monitoring terminal integrates a multi-mode communication interface, supporting interconnection between cellular mobile networks and substation monitoring systems; the online monitoring terminal has a built-in fault database that associates line topology information and automatically generates fault location maps; the online monitoring terminal also includes a protection linkage unit, configured with programmable logic, which triggers a circuit breaker tripping command when a neutral line energization fault is confirmed.

6. A method for online monitoring of live faults in the neutral wire of a low-voltage line, characterized in that, The method includes: Step S1: The relay gateway sends a time synchronization command to the distributed current measurement module; Step S2: Each current measurement module acquires the instantaneous values ​​of the three-phase current and neutral current under the synchronous time base, calculates the effective value of the current after signal conditioning, and transmits it back. Step S3: The relay gateway performs vector differential calculation on the three-phase current value and the neutral current value to generate the total unbalance index; Step S4: Determine the neutral wire live fault based on the continuous over-limit behavior of the total imbalance index, and encrypt and transmit the alarm information to the online monitoring terminal.

7. The method for online monitoring of live faults in the neutral wire of a low-voltage line according to claim 6, characterized in that, The signal conditioning process in step S2 includes: The output signal of the current transformer is proportionally amplified by an instrumentation amplifier. The amplified signal is input into a second-order active bandpass filter to suppress out-of-band noise. The filtered output signal is digitized by a high-resolution analog-to-digital converter; The microcontroller uses frequency domain analysis to extract the fundamental component of the current and calculate its effective value.

8. The method for online monitoring of live faults in the neutral wire of a low-voltage line according to claim 6, characterized in that, The fault determination logic in step S4 includes a dynamic threshold optimization mechanism, specifically: Set a basic threshold based on the historical load curve of the line; Incorporate ambient temperature sensor data to compensate for threshold offset; Automatically adjust threshold sensitivity based on electricity consumption period characteristics; After the fault is resolved, a threshold self-learning report is generated to optimize the parameters.

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