Fault alarm method and system for distribution box

Abstract

The application discloses a power distribution box fault alarm method and system, and belongs to the technical field of power system fault monitoring and safety early warning. The method solves the problem that when the number of power distribution boxes on a construction site is large and the power distribution boxes are distributed in a scattered manner, the position and number of a fault power distribution box cannot be quickly determined after short-circuit or grounding fault tripping, and each power distribution box needs to be checked. The method is characterized in that an independent sound and light alarm device is installed on the outer wall of each power distribution box and connected with a fault indicator, a short-circuit and grounding detection sensor is sleeved on the outer periphery of a cable and connected with a host through an optical fiber; after tripping, the sound and light alarm device sends out sound and light alarms to enable an inspection personnel to remotely find the fault power distribution box, a wireless communication module reports a pre-stored number to a cloud end through 4G Cat.1, and the cloud end pushes a time stamp, the number and a fault type to a user terminal applet for display and vibration prompting. The method is mainly used for rapid positioning and remote alarm of faults of a temporary power distribution system on a construction site.

Description

Technical Field

[0001] This invention belongs to the field of power system fault monitoring and safety early warning technology, and specifically relates to a method and system for alarming faults in distribution boxes. Background Technology

[0002] Construction sites typically have numerous temporary distribution boxes to distribute power to various construction tools and lighting equipment. These distribution boxes form a temporary power supply network through multi-level cable series or star connections, covering the entire construction area. In actual operation, due to reasons such as damaged cable insulation, loose joints, equipment overload, or accidental contact by construction machinery, short circuits or grounding faults frequently occur in the power distribution lines, causing the circuit breakers in the corresponding distribution boxes to trip.

[0003] When such a fault occurs and the circuit breaker trips, due to the large number of distribution boxes on the construction site and their scattered installation locations (some boxes may be located in basements, corners of floors, or temporarily obscured by materials), on-site electricians and construction managers often cannot immediately determine which distribution box has tripped. The common practice is for electricians to carry tools and inspect each distribution box sequentially, opening the door one by one to observe the circuit breaker status until the tripped box is found. When the construction site is large and there are many layers of distribution boxes, this method of opening and checking each box individually consumes a significant amount of walking time and manpower.

[0004] Furthermore, short circuits or grounding faults may only cause a single distribution box to trip, but downstream equipment affected by its power supply will also cease operation. On-site personnel often lack the specific point of the fault in the power supply line, requiring them to trace back from the end-user equipment to the power source, further prolonging the fault location time. For construction processes that rely on continuous power supply, such as concrete pouring and dewatering, prolonged downtime can lead to potential quality issues and economic losses.

[0005] To address this issue, the industry has attempted to install simple mechanical indicator lights on distribution box panels or rely on changes in the physical position of the circuit breaker handle to indicate tripping status. However, these solutions still require inspectors to approach the distribution box and carefully observe it to detect abnormalities. Given the large number and dispersed distribution boxes, this does not fundamentally reduce the time and labor intensity required to locate faulty boxes. Therefore, how to enable inspectors to quickly and remotely determine the specific location and number of faulty distribution boxes without having to open each box individually after a short circuit or ground fault trips has become a long-standing practical challenge in temporary power management at construction sites. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] Another objective of this invention is to provide a method for alarming faults in distribution boxes. This method enables an audible and visual alarm installed on the outer wall of the distribution box to emit flashing and audible alarm signals after a short circuit or grounding fault occurs and the circuit breaker trips. This allows inspection personnel to directly locate the faulty distribution box from a distance. Simultaneously, the method pushes the faulty distribution box number to the user's terminal app in real time via wireless communication, reducing the time and manpower costs associated with opening and checking each distribution box individually.

[0008] To achieve these objectives and other advantages of the present invention, a method for alarming faults in a distribution box is provided, comprising the following steps: S1: Install an audible and visual alarm with an independent power supply on the outer wall of each distribution box, and connect the trigger signal input terminal of the audible and visual alarm to the alarm output terminal of the fault indicator via a wired connection. S2: Install the main unit of the fault indicator on the front panel of the distribution box, and put the short circuit detection sensor of the fault indicator on the outer periphery of each phase cable in the distribution box, and the grounding detection sensor on the outer periphery of the three-phase cable in the distribution box. The short circuit detection sensor and the grounding detection sensor are respectively connected to the main unit of the fault indicator through optical fiber. S3: Install a wireless communication module in each distribution box and connect the wireless communication module to the remote signal output terminal of the relay of the fault indicator. The wireless communication module has the number information of the distribution box pre-stored. S4: When a short circuit or ground fault occurs in the distribution box and the circuit breaker trips, the fault indicator detects the fault current and triggers an alarm. It sends a trigger signal to the audible and visual alarm through the alarm output terminal, driving the audible and visual alarm to emit a flash alarm with a 1-10Hz Hz Hz Hz and an audible alarm with a sound pressure level of 80-120dB. S5: When the fault indicator triggers an alarm, it simultaneously sends an alarm trigger signal to the wireless communication module through the relay remote signal output terminal. After receiving the alarm trigger signal, the wireless communication module sends the fault alarm data packet containing the number information to the cloud server through the 4G Cat.1 communication standard. S6: After parsing the received fault alarm data packet, the cloud server pushes the timestamp of the fault occurrence, the number information, and the fault type to the user terminal applet that is connected to the cloud server. S7: After receiving the push notification, the user terminal applet displays the number of the faulty distribution box and the fault type on the terminal screen, and triggers local vibration feedback and sound prompts on the terminal.

[0009] Preferably, in step S2, the main unit of the fault indicator is equipped with a CT power supply unit, a rectifier and voltage regulator circuit, an energy storage capacitor, a voltage comparator, and an electronic switch. The input terminal of the CT power-taking unit is connected to at least one of the short-circuit detection sensors installed around the periphery of each phase cable in the distribution box, and the input terminal of the CT power-taking unit is also connected to the secondary winding of the grounding detection sensor installed around the periphery of the three-phase cable in the distribution box, for inducing power from the short-circuit fault current or grounding fault current. The output of the CT power supply unit is connected to the input of the rectifier and voltage regulator circuit. The output of the rectifier and voltage regulator circuit is also connected to the power supply terminal of the internal working circuit of the fault indicator, the positive terminal of the energy storage capacitor, and the positive input terminal of the voltage comparator. A reference voltage is connected to the negative input terminal of the voltage comparator, and the output of the voltage comparator is connected to the control terminal of the electronic switch. The input terminal of the electronic switch is connected to the positive terminal of the energy storage capacitor, and the output terminal of the electronic switch is connected to the power supply input terminal of the wireless communication module. Before a short circuit or ground fault occurs in the distribution box and the circuit breaker trips, the CT power take-up unit charges the energy storage capacitor through the electrical energy generated by the fault current through the rectifier and voltage regulator circuit, so that the voltage across the energy storage capacitor rises to a level greater than the reference voltage. When the circuit breaker trips, the CT power supply unit stops outputting power, and the energy storage capacitor supplies power to the internal working circuit of the fault indicator. The voltage comparator continues to output a high level until the voltage across the energy storage capacitor drops below the reference voltage, controlling the electronic switch to remain on and supplying the voltage of the energy storage capacitor to the wireless communication module. The wireless communication module completes the transmission of the fault alarm data packet before the voltage of the energy storage capacitor drops to the minimum operating voltage of the wireless communication module.

[0010] Preferably, in step S2, the host of the fault indicator is also equipped with a power failure detection circuit, a narrowband IoT communication backup module, and a data cache register. The input terminal of the power failure detection circuit is connected to the output terminal of the rectifier and voltage regulator circuit, and the output terminal of the power failure detection circuit is connected to the interrupt pin of the microcontroller of the fault indicator host. The narrowband IoT communication backup module is connected to the microcontroller via a serial peripheral interface. The narrowband IoT communication backup module has the number information of the distribution box pre-stored. The data buffer register is connected to the microcontroller; When the power failure detection circuit detects that the output voltage of the rectifier and voltage regulator circuit drops to the first preset threshold range of 2.8-3.0V, it sends an interrupt signal to the microcontroller. After responding to the interrupt signal, the microcontroller writes the number information of the distribution box to be sent and the fault type into the data buffer register, and starts the narrowband IoT communication backup module through the serial peripheral interface. The narrowband IoT communication backup module adopts the NB-IoT communication standard. Before the voltage of the energy storage capacitor drops to the minimum operating voltage of the narrowband IoT communication backup module, 2.1V, it sends a compressed data frame containing number information and fault type to the cloud server in a single unacknowledged transmission mode. The data payload length of the compressed data frame is no more than 12 bytes.

[0011] Preferably, in step S2, the fault indicator's host is also equipped with a ferroelectric memory, which is connected to the microcontroller of the fault indicator's host via an SPI interface. When the power failure detection circuit detects that the output voltage of the rectifier and voltage regulator circuit drops to the second preset threshold range of 2.5-2.7V, the microcontroller first writes the distribution box number information, fault type and current real-time clock count value as a fault record into the ferroelectric memory. Ferroelectric memories use an SPI interface for data reading and writing, and their write operations are completed before the voltage of the energy storage capacitor drops to the minimum operating voltage of the microcontroller. When the circuit breaker in the distribution box is re-closed and power is restored, and the wireless communication module completes its power-on initialization, the microcontroller reads the fault record from the ferroelectric memory. If the fault type in the fault record is a short-circuit fault or a ground fault, the fault record is combined with the timestamp of the current power restoration time and sent to the cloud server via the wireless communication module using the 4G Cat.1 communication standard. After successful transmission, the fault record in the ferroelectric memory is cleared.

[0012] Preferably, in step S5, the fault alarm data packet sent by the wireless communication module also includes fault current amplitude data and a timestamp of the tripping time. The fault current amplitude data is recorded by the host of the fault indicator and transmitted to the wireless communication module when the fault current is detected. In step S6, a fault tree analysis engine is set up in the cloud server. The fault tree analysis engine has a pre-stored construction site power distribution box topology table. The construction site power distribution box topology table records the hierarchical relationship of each power distribution box number, the number of the superior power distribution box number, and the number of the subordinate power distribution box number. When the cloud server receives fault alarm data packets from at least two distribution boxes within a preset time window of 3 to 5 seconds, the fault tree analysis engine extracts the distribution box number, fault current amplitude data, and timestamp from all the fault alarm data packets received within the preset time window. Based on the site distribution box topology table, it constructs a fault propagation path diagram and identifies the distribution box with the largest fault current amplitude as the candidate root cause box. If there are multiple distribution boxes with the largest fault current amplitude, the one with the highest topology level is identified as the root cause fault box. If the topology levels are still the same, the one with the earliest timestamp is identified as the root cause fault box. In step S6, the cloud server pushes the root cause fault box number and the fault propagation path diagram to the user terminal applet. In step S7, the user terminal applet highlights the number of the root cause fault distribution box on the terminal screen in a first display style, and displays the numbers of other affected tripped distribution boxes in chronological or topological order in a second display style.

[0013] Preferably, in step S2, the main unit of the fault indicator is also equipped with a voltage sampling circuit, a phase comparator, and a signal selection switch. The input terminal of the voltage sampling circuit is connected to the inlet terminal of each phase cable in the distribution box through a resistor voltage divider network to obtain the AC voltage signal in phase with the phase voltage. The microcontroller controls the voltage sampling circuit to output the voltage signal of the corresponding fault phase according to the determined fault phase. The first input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the short-circuit detection sensor, the second input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the ground detection sensor, and the output terminal of the signal selection switch is connected to the second input terminal of the phase comparator. When the fault indicator detects a short-circuit fault, the microcontroller selects the switch according to the determined fault phase control signal to connect the signal output terminal of the secondary winding of the short-circuit detection sensor of the corresponding fault phase to the phase comparator. When the fault type detected by the host of the fault indicator is a ground fault, the microcontroller control signal selection switch connects the signal output terminal of the secondary winding of the ground detection sensor to the phase comparator; the first input terminal of the phase comparator is connected to the output terminal of the voltage sampling circuit. The phase comparator is used to determine the phase relationship between the fault current and the voltage and output a fault direction flag bit. The fault direction flag bit can be positive or negative. In step S5, the fault alarm data packet sent by the wireless communication module also includes a fault direction flag bit; In step S6, after the fault tree analysis engine of the cloud server determines the distribution box with the largest fault current amplitude and located at the upstream of the fault propagation path graph as the root cause fault box, it also performs a direction verification step: extracting the fault direction flag bit from the fault alarm data packet corresponding to the root cause fault box. If the fault direction flag bit is positive, the determination result of the root cause fault box is maintained. If the fault direction flag is in the opposite direction, the fault tree analysis engine traverses the upstream distribution boxes adjacent to the root cause fault box in the fault propagation path diagram, re-identifies the distribution box with the largest fault current amplitude and the fault direction flag as the root cause fault box, and updates the fault propagation path diagram.

[0014] Preferably, in step S2, the main unit of the fault indicator is further provided with a current transient recording unit, a transient feature memory, and a direction determination logic circuit. The input terminal of the current transient waveform recording unit is connected to the output terminal of the signal selection switch. The current transient waveform recording unit samples the fault current waveform at a sampling frequency range of 6.4kHz to 12.8kHz and stores the sampled data in the transient feature memory. The transient feature memory pre-stores transient waveform templates for positive and negative fault currents; the first input of the direction determination logic circuit is connected to the output of the voltage sampling circuit, the second input of the direction determination logic circuit is connected to the data output of the transient feature memory, and the third input of the direction determination logic circuit is connected to the output of the phase comparator. In step S5, when the fault direction flag bit output by the phase comparator is invalid or the AC voltage amplitude detected by the voltage sampling circuit is lower than a preset threshold of 10V, the direction determination logic circuit reads the fault current transient sampling data within the first half cycle after the fault occurs from the transient feature memory, performs a first correlation calculation with the fault current transient waveform template in the positive direction, and performs a second correlation calculation with the fault current transient waveform template in the reverse direction. If the first correlation is greater than the second correlation, the positive direction is output as the fault direction flag bit; if the second correlation is greater than the first correlation, the reverse direction is output as the fault direction flag bit; if the first correlation is equal to the second correlation, the positive direction is output as the fault direction flag bit, and this fault direction flag bit replaces the fault direction flag bit output by the phase comparator and is written into the fault alarm data packet.

[0015] Preferably, in step S5, when the fault direction flag bit output by the phase comparator is in an effective state and the AC voltage amplitude detected by the voltage sampling circuit is greater than or equal to the upper limit of the preset threshold range of 20V, the direction determination logic circuit reads the fault current transient sampling data in the first half cycle after the fault occurs from the transient feature memory as the transient sample of the current fault, and stores the transient sample into the positive direction template buffer or the negative direction template buffer in the transient feature memory corresponding to the value according to the value of the fault direction flag bit output by the phase comparator. The direction determination logic circuit performs a sliding weighted average operation on the transient samples of at least five most recent faults stored in the positive direction template buffer, and replaces the positive direction fault current transient waveform template stored in the transient feature memory with the result of the operation. It also performs a sliding weighted average operation on the transient samples of at least five most recent faults stored in the negative direction template buffer, and replaces the negative direction fault current transient waveform template stored in the transient feature memory with the result of the operation.

[0016] A power distribution box fault alarm system includes multiple power distribution boxes, a fault detection alarm device installed in each power distribution box, a cloud server, and a user terminal applet. The fault detection alarm device includes an audible and visual alarm with an independent power supply installed on the outer wall of the distribution box, a fault indicator host installed on the front panel of the distribution box, short circuit detection sensors sleeved around the periphery of each phase cable inside the distribution box, grounding detection sensors sleeved around the periphery of the three-phase cables inside the distribution box, and a wireless communication module installed inside the distribution box. The trigger signal input terminal of the audible and visual alarm is connected to the alarm output terminal of the fault indicator host via a wired connection. The wireless communication module is connected to the relay remote transmission signal output terminal of the fault indicator host. The wireless communication module has the number information of the distribution box pre-stored. The short circuit detection sensor and the grounding detection sensor are respectively connected to the fault indicator host via optical fiber. The fault indicator host is equipped with a CT power supply unit, rectifier and voltage regulator circuit, energy storage capacitor, voltage comparator, electronic switch, power failure detection circuit, narrowband IoT communication backup module, data buffer register, microcontroller, ferroelectric memory, voltage sampling circuit, phase comparator, signal selection switch, current transient waveform recording unit, transient feature memory and direction determination logic circuit. The input terminal of the CT power supply unit is connected to the secondary winding of the short circuit detection sensor and the secondary winding of the grounding detection sensor. The output terminal of the CT power supply unit is connected to the input terminal of the rectifier and voltage regulator circuit. The output terminal of the rectifier and voltage regulator circuit is simultaneously connected to the power supply terminal of the internal working circuit of the fault indicator host, the positive terminal of the energy storage capacitor, and the positive input terminal of the voltage comparator. A reference voltage is connected to the negative input terminal of the voltage comparator, the output terminal of the voltage comparator is connected to the control terminal of the electronic switch, the input terminal of the electronic switch is connected to the positive terminal of the energy storage capacitor, and the output terminal of the electronic switch is connected to the power supply input terminal of the wireless communication module. The input of the power failure detection circuit is connected to the output of the rectifier and voltage regulator circuit. The output of the power failure detection circuit is connected to the interrupt pin of the microcontroller. The narrowband IoT communication backup module is connected to the microcontroller through a serial peripheral interface. The narrowband IoT communication backup module has the number information of the distribution box pre-stored. The data cache register is connected to the microcontroller. The ferroelectric memory is connected to the microcontroller through an SPI interface. The input terminal of the voltage sampling circuit is connected to the input terminal of each phase cable in the distribution box through a resistor divider network. The first input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the short circuit detection sensor. The second input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the grounding detection sensor. The output terminal of the signal selection switch is connected to the second input terminal of the phase comparator. The first input terminal of the phase comparator is connected to the output terminal of the voltage sampling circuit. The input terminal of the current transient waveform recording unit is connected to the output terminal of the signal selection switch, the output terminal of the current transient waveform recording unit is connected to the data input terminal of the transient feature memory, the transient feature memory contains a forward fault current transient waveform template and a reverse fault current transient waveform template, the first input terminal of the direction determination logic circuit is connected to the output terminal of the voltage sampling circuit, the second input terminal of the direction determination logic circuit is connected to the data output terminal of the transient feature memory, and the third input terminal of the direction determination logic circuit is connected to the output terminal of the phase comparator. The wireless communication module communicates with the cloud server via the 4G Cat.1 communication standard, and the narrowband IoT communication backup module communicates with the cloud server via the NB-IoT communication standard. The cloud server is equipped with a fault tree analysis engine, which pre-stores a topology table of the construction site distribution boxes. The topology table records the hierarchical relationship of each distribution box number, the number of the superior distribution box, and the number of the subordinate distribution boxes. The cloud server communicates with the user terminal applet.

[0017] The present invention has at least the following beneficial effects: First, the method of this invention equips each distribution box with an independent audible and visual alarm and a wired fault indicator. Short-circuit and grounding detection sensors are respectively fitted around the phase and three-phase cables and connected to the fault indicator host via optical fiber. When a short circuit or grounding fault occurs in the distribution box, causing the circuit breaker to trip, the audible and visual alarm emits an alarm signal with a 1Hz to 10Hz strobe range and a sound pressure level of 80dB to 120dB. Inspection personnel can directly locate the faulty distribution box from a distance without having to open each box individually. Simultaneously, the wireless communication module sends the pre-stored distribution box number information to the cloud server in the form of a fault alarm data packet via 4G Cat.1 communication. The cloud server pushes the timestamp of the fault occurrence, the number information, and the fault type to the user terminal app. The app displays the faulty distribution box number and fault type on the terminal screen and triggers vibration and sound alerts, allowing even on-site management personnel to instantly know the specific number of the faulty distribution box, shortening the time interval between fault occurrence and personnel response.

[0018] Secondly, the CT power-taking unit obtains fault current from the secondary windings of the short-circuit detection sensor and the grounding detection sensor and draws power accordingly. Before the circuit breaker trips, it uses the energy of the fault current to charge the energy storage capacitor, making the voltage across the energy storage capacitor higher than the reference voltage. After the circuit breaker trips, the main power supply is lost, the CT power-taking unit stops outputting, and the energy storage capacitor instead supplies power to the internal working circuit of the fault indicator host. The voltage comparator continuously outputs a high level to keep the electronic switch conducting until the voltage of the energy storage capacitor drops to the reference voltage, supplying the voltage of the energy storage capacitor to the wireless communication module. The wireless communication module uses this brief period of power to complete the transmission of fault alarm data packets, thus enabling the fault number and type to be reported to the cloud server even when the distribution box is completely de-energized, avoiding the loss of remote alarm function due to power failure.

[0019] Third, the method of the present invention further includes a power failure detection circuit, a narrowband IoT communication backup module, and a data buffer register in step S2. The power failure detection circuit monitors the output voltage of the rectifier and voltage regulator circuit. When the voltage drops to a first preset threshold range of 2.8-3.0V, it triggers a microcontroller interrupt. The microcontroller writes the distribution box number information and fault type into the data buffer register and starts the narrowband IoT communication backup module. This module adopts the NB-IoT communication standard and sends compressed data frames with a data payload of no more than 12 bytes to the cloud server in a single unacknowledged transmission mode before the energy storage capacitor voltage drops to 2.1V. Compared with the complete network search and registration process under the 4G Cat.1 communication standard, NB-IoT communication has a shorter startup and transmission time, and can complete data reporting within a limited energy storage time even in areas with weak signal coverage, reducing the probability of data loss due to communication delay.

[0020] Fourth, when the power failure detection circuit detects that the output voltage of the rectifier and regulator circuit has dropped to the second preset threshold range of 2.5-2.7V, the microcontroller writes the distribution box number, fault type, and real-time clock count as a fault record into the ferroelectric memory. The ferroelectric memory uses an SPI interface for power supply and data reading / writing, offering fast writing speed and low power consumption, and can complete the storage operation before the energy storage capacitor voltage drops to the microcontroller's minimum operating voltage. After the distribution box circuit breaker is re-closed and power is restored, the wireless communication module initializes, and the microcontroller reads the previously unreported fault record from the ferroelectric memory, combines it with the timestamp of the current power restoration time, and transmits it to the cloud server via 4G Cat.1 communication. The record is then cleared after successful transmission. Thus, even if a single NB-IoT transmission fails due to a signal dead zone or momentary strong electromagnetic interference, the fault information will not be permanently lost and can still be traced and reported after power is restored.

[0021] Fifth, the cloud server pre-stores a topology table of the site's distribution boxes, recording the box numbers and their hierarchical relationships. When the cloud server receives fault alarm data packets from at least two distribution boxes within a preset time window of 3 to 5 seconds, the fault tree analysis engine extracts the distribution box number, fault current amplitude, and timestamp from each data packet. Based on the topology table, it constructs a fault propagation path diagram and identifies the distribution box with the largest fault current amplitude located at the upstream end of the propagation path as the root cause fault box. The cloud server pushes the root cause fault box number and the fault propagation path diagram to the user's terminal app. The app highlights the root cause fault box in the first display style and displays other tripped boxes in the second display style according to time or hierarchical order. Thus, when a fault at a higher level causes multiple lower-level distribution boxes to trip almost simultaneously, managers can quickly pinpoint the source of the fault without analyzing a massive number of concurrent alarms, avoiding misjudgments.

[0022] Sixth, the voltage sampling circuit is connected to the incoming terminals of each phase cable in the distribution box through a resistor divider network to obtain AC voltage signals in phase with the phase voltage. The signal selection switch connects the secondary winding signals of the short-circuit detection sensor or grounding detection sensor to the phase comparator according to the fault type detected by the microcontroller. The phase comparator determines the phase relationship between the fault current and the voltage and outputs a fault direction flag bit in either the positive or negative direction. This flag bit is sent to the cloud server along with the fault alarm data packet. After initially determining the root cause fault box, the fault tree analysis engine on the cloud server further extracts the fault direction flag bit of that box for verification: if the flag bit is positive, the original determination is maintained; if it is negative, the system traverses the adjacent upstream distribution boxes with the largest fault current amplitude and a positive direction flag bit, and re-determines it as the root cause fault box. In cases where the impedance distribution of temporary lines on the construction site is uneven or the topology table is not updated in a timely manner, this direction verification step can correct misjudgments that may arise from relying solely on current amplitude and pre-stored topology relationships.

[0023] Seventh, the current transient waveform recording unit samples the fault current waveform at a sampling frequency of 6.4kHz to 12.8kHz and stores it in the transient feature memory, which pre-stores fault current transient waveform templates in both the positive and negative directions. When the fault direction flag output by the phase comparator is invalid or the AC voltage amplitude detected by the voltage sampling circuit is lower than a preset threshold of 10V, the direction determination logic circuit reads the current transient sampling data within the first half-cycle after the fault occurs, calculates the correlation with the positive and negative direction templates respectively, and takes the side with the higher correlation as the fault direction output. This direction flag replaces the original output value of the phase comparator and is written into the fault alarm data packet. Even when a metallic short-circuit fault causes a deep voltage drop and the phase comparator is difficult to operate reliably, this method can still provide effective direction information using the current transient waveform characteristics, ensuring the continuous operation of the root cause verification process.

[0024] Eighth, when the fault direction flag output by the phase comparator is valid and the AC voltage amplitude detected by the voltage sampling circuit is not less than 20V, the direction determination logic circuit uses the transient current sampling data within the first half-cycle after the fault occurrence as transient samples and stores them in the positive or negative direction template buffer according to the direction flag output by the phase comparator. For at least five transient samples of the most recent faults stored in the positive direction template buffer, the direction determination logic circuit performs a sliding weighted average calculation and replaces the pre-stored positive direction fault current transient waveform template with the calculation result. The same processing is performed on the negative direction template buffer. As actual operating data of the power distribution lines at the construction site accumulates, the positive and negative templates can be updated online and gradually converge to the transient response characteristics of the current line. Subsequently, when relying on transient waveforms for direction determination under voltage loss conditions, the accuracy of correlation calculation is maintained.

[0025] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0026] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0027] In the actual operation of temporary power supply systems at construction sites, on-duty electricians usually need to open the door of each distribution box one by one to observe the open / closed state of the internal circuit breaker to determine which distribution box has a tripping fault. When dozens or even hundreds of distribution boxes are arranged in the construction area, and some of them are not easily accessible due to material stacking or site constraints, this method of troubleshooting by opening each box often takes dozens of minutes or even longer, which seriously affects the normal progress of construction processes that require continuous power supply, such as concrete pouring and foundation pit dewatering. In addition, some distribution boxes are only equipped with a mechanical indicator window linked to the circuit breaker on the panel, so inspectors still have to walk close to the distribution box to identify the tripping state, which fails to fundamentally shorten the fault detection time.

[0028] In view of the above situation, the present embodiment provides a distribution box fault alarm solution suitable for construction sites. First, a battery-powered acousto-optic alarm is fixedly installed on the outer wall of each distribution box. The alarm adopts a commercially available integrated finished product of waterproof industrial warning light and buzzer, and its trigger signal input end adopts a dry contact trigger mode. A two-core shielded cable is used for wired connection between the trigger signal input end of the acousto-optic alarm and the alarm output end of the fault indicator. The fault indicator adopts a line fault indicator product that can detect both short-circuit faults and ground faults, and its main unit is installed at an easily observable position inside or outside the front panel of the distribution box in a snap-fit manner. Three short-circuit detection sensors matching the fault indicator are respectively sleeved on the peripheries of the A-phase, B-phase and C-phase cables in the distribution box, and one matching ground detection sensor is sleeved on the peripheries of the three phase cables. The sensors are connected to the main unit through multi-mode optical fibers to isolate the high voltage on the primary side. When an inter-phase short circuit or phase-to-ground leakage fault occurs in the distribution box, the fault current flows through the cable, the sensors sleeved on the periphery of the cable sense the abnormal current change, and transmit the signal to the main unit of the fault indicator through the optical fiber. After the main unit confirms the fault through internal logic judgment, it outputs a closed contact signal to the acousto-optic alarm on the outer wall of the box through the alarm output end.

[0029] Upon receiving a trigger signal, the audible and visual alarm activates immediately, driving its built-in LED strobe light to flash several times per second with high brightness, while simultaneously activating a buzzer to emit a sound clearly audible to the human ear within a range of tens of meters. Because the alarm is powered by its built-in battery and does not rely on the main power supply of the distribution box, it can continue to emit alarm signals even if a circuit breaker trips due to a fault, causing a complete power outage inside the distribution box. Inspection personnel can directly proceed to the faulty distribution box from anywhere on the construction site after hearing or seeing the alarm signal, without needing to open each box individually to check the circuit breaker status or carry additional testing tools. Simultaneously, each distribution box is equipped with an industrial-grade 4GCat.1 wireless communication module. This module connects to the remote signal output terminal of the fault indicator's relay and has a unique number for that distribution box pre-written in its internal memory. At the same moment the fault indicator host triggers the alarm, its relay remote signal output terminal sends a switching signal to the wireless communication module. The wireless communication module uses this switching signal as a start command and sends a fault alarm data packet containing the distribution box number information to the cloud server via the 4G Cat.1 communication standard. After parsing the data packet, the cloud server sends the timestamp of the fault occurrence, the distribution box number, and the fault type to the pre-bound user terminal applet via push notification. Upon receiving the push notification, the applet directly displays the faulty distribution box number and fault type on the mobile phone or other terminal screen, accompanied by the terminal's vibration and alert sound, enabling off-site management personnel to grasp the fault information and organize repairs immediately. Throughout the process, on-site personnel quickly locate the distribution box using sound and light signals, while management personnel rely on mobile phone push notifications to grasp the fault overview. The two complement each other, reducing the fault discovery time from tens of minutes to within a few minutes.

[0030] In existing construction site power distribution box fault alarm solutions, the wireless communication module typically relies on the main power supply inside the distribution box. Once a short circuit or grounding fault occurs inside the distribution box, causing the circuit breaker to trip, the main power supply is cut off, and the wireless communication module immediately loses power and stops working, unable to send fault information to the cloud server. Some improved solutions configure a separate battery for the wireless communication module; however, the battery needs to be replaced or charged regularly, increasing daily maintenance workload. Furthermore, the battery's performance degrades rapidly in high or low temperature environments, making it difficult to guarantee sufficient power to complete a full remote alarm at any time during a fault.

[0031] To address the issue of power interruption for the wireless communication module after a main power failure, this implementation adds a CT power-taking unit, a rectifier and voltage regulator circuit, an energy storage capacitor, a voltage comparator, and an electronic switch inside the fault indicator host. The CT power-taking unit consists of a secondary winding wound on an iron core. Its iron core shares a magnetic circuit with the short-circuit detection sensors mounted on the outer periphery of each phase cable within the distribution box. Simultaneously, the input terminal of the CT power-taking unit is connected in parallel with the secondary winding of a grounding detection sensor mounted on the outer periphery of the three-phase cable via a signal line. When a short-circuit or grounding fault occurs in the lines connected to the distribution box, the fault current flows through the cable, passes through the sensor's magnetic ring, and induces an AC voltage signal proportional to the fault current amplitude in the secondary winding. This signal is sent to the CT power-taking unit and converted into pulsating DC by an internal rectifier bridge. The output of the CT power unit is connected to the input of a rectifier and voltage regulator circuit. This circuit uses a combination of a low-dropout linear regulator and a filter capacitor to smooth pulsating DC power into a stable DC output voltage, with the output voltage range set between 3.3V and 5.0V. The output of the rectifier and voltage regulator circuit is connected to three points: first, the power supply to the internal circuitry of the fault indicator, providing operating voltage to the microcontroller and signal processing circuitry; second, the positive terminal of an energy storage capacitor (a 220-470 μF tantalum electrolytic capacitor) for storing electrical energy; and third, the positive input of a voltage comparator.

[0032] The negative input of the voltage comparator is connected to a reference voltage generated by a resistor divider network, with the reference voltage value set at approximately 70% of the rated operating voltage of the energy storage capacitor. The output of the voltage comparator is connected to the control terminal of an electronic switch, which can be an N-channel enhancement-mode MOSFET or an analog switch chip. Its input is connected to the positive terminal of the energy storage capacitor, and its output is led to the power supply input terminal of the wireless communication module, which is connected to the remote signal output terminal of the relay on the fault indicator's main casing.

[0033] During the brief period following a short circuit or ground fault in the distribution box, before the circuit breaker trips, the fault current amplitude is high. The current induced by the fault current in the CT power-taking unit continuously charges the energy storage capacitor through the rectifier and voltage regulator circuit. The voltage across the energy storage capacitor rapidly rises to a value higher than the reference voltage. At this time, the voltage comparator outputs a high level, the electronic switch remains on, and the current path between the energy storage capacitor and the power input terminal of the wireless communication module is opened. When the circuit breaker trips after tens of milliseconds, the main circuit current is cut off, the CT power-taking unit immediately stops outputting power, and the output voltage of the rectifier and voltage regulator circuit begins to decay. At this time, the energy stored in the energy storage capacitor continues to power the main unit through the internal working circuit power supply terminal of the fault indicator host, while simultaneously providing operating voltage to the wireless communication module through the on-state electronic switch. The voltage comparator continues to output a high level until the voltage across the energy storage capacitor drops below the reference voltage, and the electronic switch remains on, ensuring uninterrupted power supply to the wireless communication module. After powering on, the wireless communication module quickly completes network attachment and data packaging. Before the voltage of the energy storage capacitor drops to the minimum operating voltage of the wireless communication module, it sends the fault alarm data packet containing the distribution box number to the cloud server via the 4G Cat.1 communication standard.

[0034] With the above solution, the fault indicator host does not need an external independent battery or UPS power supply. It uses the energy of the fault current itself to charge the energy storage capacitor. Even under extreme conditions where the main power supply is completely lost due to the circuit breaker tripping, it can still provide a short but reliable power supply window for the wireless communication module, ensuring the continuity of the remote alarm function.

[0035] In a scheme that uses a CT (current transformer) power supply and an energy storage capacitor to power the wireless communication module, when the construction site where the distribution box is located is in an area with poor mobile communication signal coverage, the entire process of the 4G Cat.1 wireless communication module from power-on, network search, registration to data transmission may take several seconds or even more than ten seconds. The energy storage capacitor has limited capacity, and when powering both the fault indicator host and the wireless communication module simultaneously, the voltage decays rapidly, potentially dropping below the minimum operating voltage of the wireless communication module before the data packet is even sent, causing the remote alarm to fail.

[0036] To address the aforementioned issues, this embodiment further incorporates a power-down detection circuit, a narrowband IoT communication backup module, and a data buffer register within the fault indicator host. The power-down detection circuit comprises a resistor divider network and a voltage comparator, with its input connected in parallel to the output of the rectifier and voltage regulator circuit to monitor the rectified and regulated DC bus voltage in real time. The output of the power-down detection circuit is connected to the external interrupt pin of the microcontroller in the fault indicator host. When the bus voltage drops to a first preset threshold range of 2.8-3.0V, the power-down detection circuit sends a falling-edge interrupt signal to the microcontroller. The narrowband IoT communication backup module uses an industrial-grade module supporting the NB-IoT communication standard. This module connects to the microcontroller via a serial peripheral interface, and the distribution box's identification number is pre-written into the module's internal memory. The data buffer register is a designated address area in the microcontroller's internal random access memory used to temporarily store data to be transmitted.

[0037] When a short circuit or ground fault occurs in the distribution box and the circuit breaker trips, the CT power supply unit stops outputting power, and the output voltage of the rectifier and voltage regulator circuit begins to drop. When the power failure detection circuit detects the voltage drop to the first preset threshold range, the microcontroller immediately responds to the interrupt signal and enters the interrupt service routine. The microcontroller first reads the current distribution box number and the determined fault type from the main program variable area and temporarily stores them in the data buffer register. Then, the microcontroller sends a start command and configuration parameters to the narrowband IoT communication backup module via the serial peripheral interface, switching the module from deep sleep to working state. After the narrowband IoT communication backup module is powered on, the microcontroller reads the number information and fault type from the data buffer register, compresses them in hexadecimal format into a compressed data frame with a data payload length not exceeding twelve bytes, writes it to the narrowband IoT communication backup module's transmit buffer via the serial peripheral interface, and issues a transmit command. The narrowband IoT communication backup module uses the NB-IoT communication standard and forwards the compressed data frame to the cloud server via the operator's base station in a single-pass, unacknowledged transmission mode. Since the NB-IoT communication standard does not require the execution of a complete TCP / IP protocol stack interaction process, its overall network search and attachment time and data transmission time are significantly shorter than that of the 4G Cat.1 communication standard. Transmission can be completed within the time window when the energy storage capacitor voltage drops from 2.8V to the minimum operating voltage of 2.1V of the narrowband IoT communication backup module.

[0038] With the addition of the above circuit, even in the edge area of ​​the construction site where the 4G Cat.1 signal coverage is weak, when the output voltage of the rectifier and voltage regulator circuit begins to drop, the microcontroller can actively switch to the NB-IoT narrowband Internet of Things communication backup module with lower power consumption and faster connection to report fault information. It can use the limited energy at the end of the discharge of the energy storage capacitor to complete a reliable data transmission, reducing the probability of alarm information loss due to excessive communication delay.

[0039] When using a narrowband IoT communication backup module to send fault information in a single, unconfirmed transmission mode, if the construction site happens to be located in an NB-IoT signal coverage blind spot or experiences strong electromagnetic interference at the moment of the fault, the transmission may not be successfully received by the cloud server. Since the distribution box loses power completely after the circuit breaker trips, the microcontroller and wireless communication module immediately cease operation. No record of the faulty distribution box number and fault type is left locally for later review, making the fault event untraceable and posing difficulties for subsequent line maintenance and fault analysis.

[0040] To address this issue, this implementation adds a ferroelectric memory chip inside the fault indicator host. The power and data pins of the ferroelectric memory are connected to the corresponding interfaces of the microcontroller via SPI interfaces. Ferroelectric memory features fast write speed, long erase / write life, and low power consumption; the current required for write operations is far less than that of conventional flash memory. In addition to monitoring the first preset threshold range, the power-down detection circuit also sets a second preset threshold range of 2.5-2.7V. When the output voltage of the rectifier and regulator circuit continues to drop and reaches the second preset threshold range, the microcontroller combines the distribution box number information, the determined fault type, and the current count value read from the real-time clock module to form a fault record, which is then stored in the designated address area of ​​the ferroelectric memory via the SPI interface in byte-by-byte write mode. Because the ferroelectric memory has an extremely fast write speed, its write timing can be completed in just a few hundred nanoseconds, sufficient to complete the storage operation within the short time window during which the energy storage capacitor voltage drops from 2.5V to the microcontroller's minimum operating voltage.

[0041] After the fault in the distribution box is cleared and the circuit breaker is re-closed to restore power, the wireless communication module completes its power-on initialization, and the microcontroller starts from the reset state and executes the power-on self-test program. The self-test program includes reading operations on a specific address area of ​​the ferroelectric memory. The microcontroller traverses the memory cells, checking for any uncleared fault records. If the fault type field in the read fault record corresponds to a short-circuit fault or ground fault, the microcontroller combines this fault record with the timestamp of the current power restoration time obtained from the cloud server and retransmits it to the cloud server via the wireless communication module using the 4G Cat.1 communication standard. Upon receiving this retransmitted data packet, the cloud server adds it to the fault history database. After successful transmission, the microcontroller writes a clear command to the ferroelectric memory, resetting the memory cell containing the fault record to an empty state.

[0042] In this way, even if the NB-IoT single transmission fails to reach the cloud server for various reasons at the moment of power outage, the fault information is still reliably stored in the non-volatile ferroelectric memory. After the power supply is restored, the transmission is automatically completed, so that every fault trip event is traceable and the permanent loss of fault records is avoided.

[0043] In existing remote alarm systems for construction site distribution boxes, when a short circuit or grounding fault occurs in the upstream power supply line, circuit breakers in multiple downstream distribution boxes often trip successively within a very short time. The cloud server receives multiple fault alarm data packets from different distribution boxes within seconds, and numerous push notifications simultaneously pop up on the user terminal's mini-program interface. Faced with a screen full of alarm information, on-duty management personnel often have to check the box number and fault type one by one, making it difficult to quickly distinguish which box is the source of the fault and which boxes are passively tripped due to the upstream fault. This can easily lead to incorrect troubleshooting directions and delays in emergency repairs.

[0044] To address this issue, this implementation adds two key data fields to the fault alarm data packet sent by the wireless communication module. The first is the fault current amplitude data, which is sampled and recorded by the fault indicator host via an internal analog-to-digital converter at the instant the fault current is detected, in amperes. The second is the timestamp of the tripping moment, generated by the real-time clock module of the fault indicator host at the moment the alarm is triggered, accurate to the millisecond level. When the alarm is triggered, the fault indicator host transmits these two data fields along with the distribution box number to the wireless communication module. The wireless communication module then encapsulates this data and sends it to the cloud server via 4G Cat.1 communication.

[0045] The cloud server is equipped with a fault tree analysis engine, which pre-stores a topology table of the site's electrical distribution boxes. This topology table was entered by engineering technicians during the initial system deployment based on the actual power supply drawings at the site, recording the unique number of each distribution box, its parent distribution box number, and the hierarchical relationship of its child distribution box numbers. When the cloud server receives fault alarm data packets from at least two distribution boxes within a preset time window of 3 to 5 seconds, the fault tree analysis engine is activated. The engine first extracts the distribution box number, fault current amplitude data, and timestamp from all fault alarm data packets received within the time window and stores them in a temporary buffer. Then, based on the hierarchical connections of the distribution boxes in the topology table, the engine constructs a fault propagation path diagram with each alarm box as a node. Arrows in the diagram indicate the power supply direction from the parent to the child distribution box. The engine traverses all nodes in the propagation path diagram, compares the fault current amplitude data of each node, and identifies the hierarchical position of each node in the topology. The engine identifies the distribution box with the largest fault current amplitude as the candidate root cause distribution box; if there are multiple distribution boxes with the largest fault current amplitude, the one with the highest topology level is identified as the root cause fault distribution box; if the topology levels are still the same, the one with the earliest timestamp is identified as the root cause fault distribution box.

[0046] After determining the root cause, the cloud server sends the root cause fault box number and a complete fault propagation path diagram as part of the push notification to the user terminal mini-program connected to the cloud server. Upon receiving the push notification, the user terminal mini-program highlights the root cause fault box number on the terminal screen in a first display style, such as using bold red font or a pinned card. Simultaneously, the mini-program displays the numbers of other affected tripped distribution boxes in chronological or topological order in a second display style, such as using small gray text or an indented list. The mini-program retains the function of triggering local vibration feedback and sound alerts on the terminal.

[0047] After adopting the above solution, when a complex fault involving multiple power outages occurs at the construction site, managers can immediately see the root cause faulty electrical box automatically identified by the system on their mobile phone screens, eliminating the need for manual inference and analysis from a large number of concurrent alarm messages. Following the push notifications, they can directly go to the location of the root cause electrical box for troubleshooting and repair. The downstream electrical boxes will automatically resume normal operation after power is restored from the upstream, significantly shortening fault handling time and reducing the probability of misjudgments and missed diagnoses.

[0048] In determining the root cause fault box based on the fault current amplitude and the pre-stored topology table, when the impedance distribution of the site's power distribution lines is uneven due to significant differences in cable laying length or mid-course wiring changes, the fault current amplitude detected by the upstream box closer to the power source and the downstream box closer to the load side may be quite similar. In some cases, the downstream box may even measure a larger current due to shorter cables. If the topology table fails to reflect the actual wiring changes on site in a timely manner, the cloud server may misidentify a downstream, non-root cause fault box as the root cause fault box based solely on the current amplitude and the static topology table, leading maintenance personnel to troubleshoot in the wrong direction.

[0049] To address this issue, this implementation adds a voltage sampling circuit, a phase comparator, and a signal selection switch inside the fault indicator main unit. The input of the voltage sampling circuit is connected to the input terminals of each phase cable in the distribution box via a resistor divider network. The voltage division ratio is selected based on the rated voltage of the distribution box, ensuring that the amplitude of the sampled output signal is within the allowable input range of the phase comparator, while maintaining a sinusoidal waveform in phase with the phase voltage. The signal selection switch uses a dual-channel analog multiplexer chip. Its first input is connected to the signal output terminal of the secondary winding of the short-circuit detection sensor, its second input is connected to the signal output terminal of the secondary winding of the grounding detection sensor, and its output is connected to the second input terminal of the phase comparator. The first input terminal of the phase comparator is connected to the output terminal of the voltage sampling circuit.

[0050] When the microcontroller inside the fault indicator detects a short-circuit fault or a ground fault, it outputs a control level to the address selection pin of the signal selection switch based on the fault type. When the fault type is a short-circuit fault, the microcontroller selects the corresponding fault phase and connects the signal output of the secondary winding of the short-circuit detection sensor to the second input of the phase comparator, simultaneously controlling the voltage sampling circuit to output the voltage signal of the corresponding fault phase. When the fault type is a ground fault, the microcontroller selects the ground fault detection sensor and connects the signal output of the secondary winding to the second input of the phase comparator. Thus, the two inputs of the phase comparator obtain a voltage signal in phase with the fault phase voltage and a current-to-voltage signal in phase with the fault current, respectively. The phase comparator internally uses a zero-crossing detection circuit to capture the zero-crossing point of the rising edge of each signal, measures the time difference between them, and converts it into a phase angle difference. If the current signal lags the voltage signal by an angle between 0 and 180 degrees, the phase comparator outputs a positive direction as a fault direction flag; if the current signal leads the voltage signal by an angle between 0 and 180 degrees, the phase comparator outputs a negative direction as a fault direction flag. This fault direction flag is added as a new data field and uploaded to the cloud server along with the fault alarm data packet sent by the wireless communication module.

[0051] After initially identifying the root cause fault box based on the fault current amplitude and topology table, the fault tree analysis engine on the cloud server proceeds to the direction verification step. The engine extracts the fault direction flag from the fault alarm data packet corresponding to the root cause fault box for verification. If the fault direction flag is positive, it indicates that the fault current flows from the box downstream, meaning the box itself is the source of the fault or the fault is located in a downstream line, and the original judgment remains unchanged. If the fault direction flag is negative, it indicates that the fault current flows from downstream to upstream, meaning the actual fault point is located on the power supply side of the box, not itself or downstream, and the initially identified root cause box is a misjudgment. The engine then traverses the upstream distribution box nodes adjacent to the fault box in the fault propagation path diagram, selects the box with the largest fault current amplitude and a positive fault direction flag among the adjacent upstream distribution boxes, re-identifies it as the root cause fault box, and updates the root cause node identifier in the fault propagation path diagram accordingly.

[0052] With this supplementary direction verification step, even if there are significant differences in the impedance of the lines at the construction site or if there are deviations between the topology record and the actual wiring, the cloud server can still use the fault direction information uploaded by each electrical box to correct the preliminary judgment results and accurately point the investigation direction to the real source of the fault.

[0053] When using a phase comparator to determine the fault direction, if a metallic short-circuit fault occurs in the distribution box, the voltage at the fault point drops to near zero volts. The AC voltage signal acquired by the voltage sampling circuit has extremely low amplitude or severely distorted waveform, making it impossible for the phase comparator to accurately capture the zero-crossing point. The output fault direction flag may then be invalid or have an incorrect value. In this case, the direction verification step on the cloud server will fail due to the lack of valid direction information, and the determination of the faulty distribution box may still be inaccurate.

[0054] To address this issue, this embodiment further incorporates a current transient waveform recording unit, a transient feature memory, and a direction determination logic circuit within the fault indicator host. The input of the current transient waveform recording unit is connected to the output of a signal selection switch, which is also connected to the signal output of the secondary winding of the sensor corresponding to the current fault type. The current transient waveform recording unit contains a high-speed analog-to-digital converter that continuously samples the fault current waveform at a sampling frequency within the range of 6.4-12.8kHz and cyclically writes the sampled data into the transient feature memory. The transient feature memory pre-programs two sets of waveform template data: a forward fault current transient waveform template and a reverse fault current transient waveform template. These two sets of templates are current transient waveform feature data recorded during the first half-cycle after a fault occurs, under laboratory conditions and with reference to typical construction site power distribution line parameters, simulating forward and reverse short-circuit faults respectively.

[0055] The first input terminal of the direction determination logic circuit is connected to the output terminal of the voltage sampling circuit for real-time monitoring of AC voltage amplitude; the second input terminal is connected to the data output terminal of the transient feature memory, which can read the sampled data and template data in the memory; the third input terminal is connected to the output terminal of the phase comparator for obtaining the fault direction flag status output by the phase comparator.

[0056] When a short-circuit or ground fault occurs in the distribution box and the circuit breaker trips, the direction determination logic circuit first reads the fault direction flag bit output by the phase comparator and simultaneously reads the AC voltage amplitude detected by the voltage sampling circuit. If the direction determination logic circuit detects that the fault direction flag bit output by the phase comparator is invalid, or detects that the AC voltage amplitude is below a preset threshold range of 10V, it determines that direction information cannot be reliably obtained through phase comparison. At this time, the direction determination logic circuit immediately reads the sampling data from the transient feature memory for a period of time before and after the fault occurrence, and extracts the transient current sampling data for the first half-cycle after the fault occurrence as the analysis sample.

[0057] The direction determination logic circuit calculates the correlation between the analyzed sample and the pre-stored positive and negative direction fault current transient waveform templates in the transient feature memory. The correlation calculation uses a normalized cross-correlation algorithm, calculating the sum of the amplitude products of the sample sequence and the template sequence at each sampling point, and dividing by the product of the root mean square values ​​of the two sequences to obtain the first and second correlation values. The direction determination logic circuit compares the magnitudes of the first and second correlation values: if the first correlation is greater than the second correlation, it indicates that the current fault current transient waveform is more similar to the positive direction template, and the positive direction is output as the fault direction flag; if the second correlation is greater than the first correlation, the negative direction is output as the fault direction flag. If the first correlation is equal to the second correlation, the positive direction is output as the fault direction flag. The direction determination logic circuit replaces the invalid or erroneous value previously output by the phase comparator with the calculated fault direction flag and writes it into the fault alarm data packet, which is then sent to the cloud server along with the wireless communication module.

[0058] With this addition, even under adverse conditions where a metallic short-circuit fault causes a severe drop in voltage signal and the phase comparator cannot function properly, the fault indicator host can still reliably determine the fault direction by analyzing the transient waveform characteristics of the current. This provides an effective direction flag input for the subsequent root cause verification steps on the cloud server, ensuring the continuity of direction determination and the accuracy of root cause location.

[0059] In the process of using current transient waveform templates for direction determination, the forward and reverse fault current transient waveform templates pre-stored in the transient feature memory are usually offline fixed data burned at the factory, recorded based on typical line parameters and single fault conditions. However, the actual transient response characteristics of the power distribution lines on the construction site vary significantly with different cable laying lengths, laying methods, connected load types, and fault transition resistances. There may be a mismatch between the fixed templates and the actual fault current transient waveforms, causing the accuracy of the direction determination calculated by the correlation to gradually decrease as the line operating conditions change.

[0060] To address this issue, this implementation adds an online template update function to the direction determination logic circuit. When the fault direction flag bit output by the phase comparator is valid, and the AC voltage amplitude detected by the voltage sampling circuit is greater than or equal to the upper limit of the preset threshold range of 20V, it indicates that the voltage signal is normal under the current fault condition and the phase comparator can reliably determine the direction. At this time, after completing the normal direction determination, the direction determination logic circuit reads the fault current transient sampling data within the first half-cycle after the fault occurred from the transient feature memory and uses it as the transient sample for this fault. According to the value of the valid fault direction flag bit output by the phase comparator, the direction determination logic circuit stores the transient sample into the corresponding positive direction template buffer or negative direction template buffer in the transient feature memory. The positive direction template buffer and the negative direction template buffer are each a ring-shaped storage area that can accommodate multiple transient samples. Each time a new sample is stored, the oldest sample is automatically overwritten.

[0061] When the number of valid transient samples stored in the positive direction template buffer reaches at least five, the direction determination logic circuit performs a moving weighted average operation on all samples in the buffer. The moving weighted average operation is performed as follows: Samples in the buffer arranged in chronological order of their entry time are assigned weight coefficients decreasing from nearest to farthest. The amplitude of each sample at each sampling time is multiplied by its corresponding weight, summed, and then divided by the sum of the weights to obtain a new set of transient waveform data. The direction determination logic circuit replaces the pre-stored positive direction fault current transient waveform template in the transient feature memory with the result of this operation. The same moving weighted average operation is performed on the samples in the negative direction template buffer, and the result replaces the pre-stored negative direction fault current transient waveform template in the transient feature memory.

[0062] As the power distribution lines at the construction site accumulate valid fault events during long-term operation, the forward and reverse direction templates are continuously updated online. The waveform characteristics in the templates gradually converge to the typical transient response characteristics under the actual operating conditions of the line. When a subsequent metallic short-circuit fault occurs, causing a voltage drop and the phase comparator to malfunction, the forward and reverse direction templates called by the direction determination logic circuit are already versions corrected by field data, which are more consistent with the actual transient characteristics of the current line, and the accuracy of the correlation calculation is maintained at a high level.

[0063] This invention provides a power distribution box fault alarm system suitable for temporary power supply scenarios at construction sites. The system consists of multiple power distribution boxes, a fault detection alarm device installed in each power distribution box, a cloud server, and a user terminal applet running on the mobile terminal of the management personnel.

[0064] Each distribution box is equipped with a fault detection alarm device comprising the following components: A sound and light alarm with an independent power supply is fixedly mounted on the outer wall of the distribution box. This alarm has an internal lithium thionyl chloride battery pack, allowing it to continue operating even when the main power supply to the distribution box fails. The trigger signal input terminal of the sound and light alarm is wired to the alarm output terminal of the fault indicator host installed on the front panel of the distribution box via a two-core shielded cable. The fault indicator host integrates a complete signal processing and communication control circuit. A short-circuit detection sensor is fitted around the periphery of each of the A, B, and C phase cables inside the distribution box, and a grounding detection sensor is fitted around all three phase cables. These sensors are connected to the fault indicator host via multimode optical fiber. A 4G Cat.1 wireless communication module is also installed inside the distribution box. This module is connected to the relay remote signal output terminal of the fault indicator host, and the module's internal memory is pre-written with the unique serial number of the distribution box.

[0065] The internal circuitry of the fault indicator host includes a CT power supply unit, a rectifier and voltage regulator circuit, an energy storage capacitor, a voltage comparator, an electronic switch, a power-down detection circuit, a narrowband IoT communication backup module, a data buffer register, a microcontroller, a ferroelectric memory, a voltage sampling circuit, a phase comparator, a signal selection switch, a current transient recording unit, a transient feature memory, and a direction determination logic circuit. The input of the CT power supply unit is connected to the secondary windings of both the short-circuit detection sensor and the grounding detection sensor. The output of the CT power supply unit is connected to the input of the rectifier and voltage regulator circuit. The output of the rectifier and voltage regulator circuit is connected to the power supply terminal of the internal operating circuit of the fault indicator host, the positive terminal of the energy storage capacitor, and the positive input terminal of the voltage comparator. The negative input terminal of the voltage comparator is connected to a reference voltage, and its output is connected to the control terminal of the electronic switch. The input of the electronic switch is connected to the positive terminal of the energy storage capacitor, and its output is connected to the power supply input terminal of the wireless communication module. The input of the power-down detection circuit is connected to the output of the rectifier and voltage regulator circuit, and its output is connected to the interrupt pin of the microcontroller. The narrowband IoT communication backup module is connected to the microcontroller via a serial peripheral interface. This module also pre-stores the distribution box number information. A data buffer register is connected to the microcontroller, and the ferroelectric memory is connected to the microcontroller via an SPI interface. The input of the voltage sampling circuit is connected to the input terminals of each phase cable in the distribution box through a resistor divider network. The first input of the signal selection switch is connected to the signal output of the secondary winding of the short-circuit detection sensor, and the second input is connected to the signal output of the secondary winding of the grounding detection sensor. The output of the signal selection switch is connected to the second input of the phase comparator, and the first input of the phase comparator is connected to the output of the voltage sampling circuit. The input of the current transient waveform recording unit is connected to the output of the signal selection switch, and its output is connected to the data input of the transient feature memory, which pre-stores positive and negative fault current transient waveform templates. The first input of the direction determination logic circuit is connected to the output of the voltage sampling circuit, the second input is connected to the data output of the transient feature memory, and the third input is connected to the output of the phase comparator.

[0066] The wireless communication module establishes a communication connection with the cloud server via the 4G Cat.1 communication standard, while the narrowband IoT communication backup module establishes a communication connection with the cloud server via the NB-IoT communication standard. The cloud server is equipped with a fault tree analysis engine, which pre-stores a topology table of the site's electrical distribution boxes. This table records the hierarchical relationship between each distribution box number, its parent distribution box number, and its child distribution box numbers. The cloud server communicates with the user terminal app via mobile internet, allowing push notifications to be delivered to the mobile terminals held by management personnel in real time.

[0067] When a short circuit or ground fault occurs in any distribution box and the circuit breaker trips, the audible and visual alarm inside the box emits a high-brightness flash and a high-decibel sound. Inspection personnel can quickly locate the faulty box by following the direction of the sound and light. Simultaneously, the energy storage capacitor provides a brief power window to the fault indicator host and wireless communication module at the moment of tripping. The wireless communication module or narrowband IoT communication backup module sends an alarm data packet containing the box number, fault type, fault current amplitude, timestamp, and fault direction flag to the cloud server. After parsing the data, the cloud server's fault tree analysis engine automatically determines the root cause faulty box based on the topology table and direction flag, and pushes the determination result and fault propagation path diagram to the user terminal app. The app distinguishes the root cause box and affected boxes on the screen with different display styles and triggers vibration and sound alerts, enabling on-site management personnel to obtain accurate fault location information and organize emergency repairs immediately.

[0068] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for alarming faults in a distribution box, characterized in that, Includes the following steps: S1: Install an audible and visual alarm with an independent power supply on the outer wall of each distribution box, and connect the trigger signal input terminal of the audible and visual alarm to the alarm output terminal of the fault indicator via a wired connection. S2: Install the main unit of the fault indicator on the front panel of the distribution box, and put the short circuit detection sensor of the fault indicator on the outer periphery of each phase cable in the distribution box, and the grounding detection sensor on the outer periphery of the three-phase cable in the distribution box. The short circuit detection sensor and the grounding detection sensor are respectively connected to the main unit of the fault indicator through optical fiber. S3: Install a wireless communication module in each distribution box and connect the wireless communication module to the remote signal output terminal of the relay of the fault indicator. The wireless communication module has the number information of the distribution box pre-stored. S4: When a short circuit or ground fault occurs in the distribution box and the circuit breaker trips, the fault indicator detects the fault current and triggers an alarm. It sends a trigger signal to the audible and visual alarm through the alarm output terminal, driving the audible and visual alarm to emit a flash alarm with a 1-10Hz Hz Hz Hz and an audible alarm with a sound pressure level of 80-120dB. S5: When the fault indicator triggers an alarm, it simultaneously sends an alarm trigger signal to the wireless communication module through the relay remote signal output terminal. After receiving the alarm trigger signal, the wireless communication module sends the fault alarm data packet containing the number information to the cloud server through the 4G Cat.1 communication standard. S6: After parsing the received fault alarm data packet, the cloud server pushes the timestamp of the fault occurrence, the number information, and the fault type to the user terminal applet that is connected to the cloud server. S7: After receiving the push notification, the user terminal applet displays the number of the faulty distribution box and the fault type on the terminal screen, and triggers local vibration feedback and sound prompts on the terminal.

2. The method for alarming faults in a distribution box according to claim 1, characterized in that, In step S2, the main unit of the fault indicator is equipped with a CT power supply unit, a rectifier and voltage regulator circuit, an energy storage capacitor, a voltage comparator and an electronic switch. The input terminal of the CT power-taking unit is connected to at least one of the short-circuit detection sensors installed around the periphery of each phase cable in the distribution box, and the input terminal of the CT power-taking unit is also connected to the secondary winding of the grounding detection sensor installed around the periphery of the three-phase cable in the distribution box, for inducing power from the short-circuit fault current or grounding fault current. The output of the CT power supply unit is connected to the input of the rectifier and voltage regulator circuit. The output of the rectifier and voltage regulator circuit is also connected to the power supply terminal of the internal working circuit of the fault indicator, the positive terminal of the energy storage capacitor, and the positive input terminal of the voltage comparator. A reference voltage is connected to the negative input terminal of the voltage comparator, and the output of the voltage comparator is connected to the control terminal of the electronic switch. The input terminal of the electronic switch is connected to the positive terminal of the energy storage capacitor, and the output terminal of the electronic switch is connected to the power supply input terminal of the wireless communication module. Before a short circuit or ground fault occurs in the distribution box and the circuit breaker trips, the CT power take-up unit charges the energy storage capacitor through the electrical energy generated by the fault current through the rectifier and voltage regulator circuit, so that the voltage across the energy storage capacitor rises to a level greater than the reference voltage. When the circuit breaker trips, the CT power supply unit stops outputting power, and the energy storage capacitor supplies power to the internal working circuit of the fault indicator. The voltage comparator continues to output a high level until the voltage across the energy storage capacitor drops below the reference voltage, controlling the electronic switch to remain on and supplying the voltage of the energy storage capacitor to the wireless communication module. The wireless communication module completes the transmission of the fault alarm data packet before the voltage of the energy storage capacitor drops to the minimum operating voltage of the wireless communication module.

3. The method for alarming faults in a distribution box according to claim 2, characterized in that, In step S2, the fault indicator's host is also equipped with a power failure detection circuit, a narrowband IoT communication backup module, and a data cache register. The input terminal of the power failure detection circuit is connected to the output terminal of the rectifier and voltage regulator circuit, and the output terminal of the power failure detection circuit is connected to the interrupt pin of the microcontroller of the fault indicator host. The narrowband IoT communication backup module is connected to the microcontroller via a serial peripheral interface. The narrowband IoT communication backup module has the number information of the distribution box pre-stored. The data buffer register is connected to the microcontroller; When the power failure detection circuit detects that the output voltage of the rectifier and voltage regulator circuit drops to the first preset threshold range of 2.8-3.0V, it sends an interrupt signal to the microcontroller. After responding to the interrupt signal, the microcontroller writes the number information of the distribution box to be sent and the fault type into the data buffer register, and starts the narrowband IoT communication backup module through the serial peripheral interface. The narrowband IoT communication backup module adopts the NB-IoT communication standard. Before the voltage of the energy storage capacitor drops to the minimum operating voltage of the narrowband IoT communication backup module, 2.1V, it sends a compressed data frame containing number information and fault type to the cloud server in a single unacknowledged transmission mode. The data payload length of the compressed data frame is no more than 12 bytes.

4. The method for alarming faults in a distribution box according to claim 3, characterized in that, In step S2, the fault indicator's host is also equipped with a ferroelectric memory, which is connected to the microcontroller of the fault indicator's host via an SPI interface. When the power failure detection circuit detects that the output voltage of the rectifier and voltage regulator circuit drops to the second preset threshold range of 2.5-2.7V, the microcontroller first writes the distribution box number information, fault type and current real-time clock count value as a fault record into the ferroelectric memory. Ferroelectric memories use an SPI interface for data reading and writing, and their write operations are completed before the voltage of the energy storage capacitor drops to the minimum operating voltage of the microcontroller. When the circuit breaker in the distribution box is re-closed and power is restored, and the wireless communication module completes its power-on initialization, the microcontroller reads the fault record from the ferroelectric memory. If the fault type in the fault record is a short-circuit fault or a ground fault, the fault record is combined with the timestamp of the current power restoration time and sent to the cloud server via the wireless communication module using the 4G Cat.1 communication standard. After successful transmission, the fault record in the ferroelectric memory is cleared.

5. The method for alarming faults in a distribution box according to claim 3, characterized in that, In step S5, the fault alarm data packet sent by the wireless communication module also includes fault current amplitude data and a timestamp of the tripping time. The fault current amplitude data is recorded by the host of the fault indicator and transmitted to the wireless communication module when the fault current is detected. In step S6, a fault tree analysis engine is set up in the cloud server. The fault tree analysis engine has a pre-stored construction site power distribution box topology table. The construction site power distribution box topology table records the hierarchical relationship of each power distribution box number, the number of the superior power distribution box number, and the number of the subordinate power distribution box number. When the cloud server receives fault alarm data packets from at least two distribution boxes within a preset time window of 3 to 5 seconds, the fault tree analysis engine extracts the distribution box number, fault current amplitude data and timestamp from all the fault alarm data packets received within the preset time window, constructs a fault propagation path diagram based on the topology table of the distribution boxes on the construction site, and identifies the distribution box with the largest fault current amplitude as the candidate root cause box. If there are multiple distribution boxes with the largest fault current amplitude, the one with the highest topology level is identified as the root cause fault distribution box. If the topology levels are still the same, the one with the earliest timestamp will be identified as the root cause fault electrical box. In step S6, the cloud server pushes the root cause fault box number and the fault propagation path diagram to the user terminal applet. In step S7, the user terminal applet highlights the number of the root cause fault distribution box on the terminal screen in a first display style, and displays the numbers of other affected tripped distribution boxes in chronological or topological order in a second display style.

6. The method for alarming faults in a distribution box according to claim 5, characterized in that, In step S2, the main unit of the fault indicator is also equipped with a voltage sampling circuit, a phase comparator, and a signal selection switch. The input terminal of the voltage sampling circuit is connected to the inlet terminal of each phase cable in the distribution box through a resistor voltage divider network to obtain the AC voltage signal in phase with the phase voltage. The microcontroller controls the voltage sampling circuit to output the voltage signal of the corresponding fault phase according to the determined fault phase. The first input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the short-circuit detection sensor, the second input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the ground detection sensor, and the output terminal of the signal selection switch is connected to the second input terminal of the phase comparator. When the fault indicator detects a short-circuit fault, the microcontroller selects the switch according to the determined fault phase control signal to connect the signal output terminal of the secondary winding of the short-circuit detection sensor of the corresponding fault phase to the phase comparator. When the fault type detected by the host of the fault indicator is a ground fault, the microcontroller control signal selection switch connects the signal output terminal of the secondary winding of the ground detection sensor to the phase comparator; the first input terminal of the phase comparator is connected to the output terminal of the voltage sampling circuit. The phase comparator is used to determine the phase relationship between the fault current and the voltage and output a fault direction flag bit. The fault direction flag bit can be positive or negative. In step S5, the fault alarm data packet sent by the wireless communication module also includes a fault direction flag bit; In step S6, after the fault tree analysis engine of the cloud server determines the distribution box with the largest fault current amplitude and located at the upstream of the fault propagation path graph as the root cause fault box, it also performs a direction verification step: extracting the fault direction flag bit from the fault alarm data packet corresponding to the root cause fault box. If the fault direction flag bit is positive, the determination result of the root cause fault box is maintained. If the fault direction flag is in the opposite direction, the fault tree analysis engine traverses the upstream distribution boxes adjacent to the root cause fault box in the fault propagation path diagram, re-identifies the distribution box with the largest fault current amplitude and the fault direction flag as the root cause fault box, and updates the fault propagation path diagram.

7. The method for alarming faults in a distribution box according to claim 6, characterized in that, In step S2, the main unit of the fault indicator is also equipped with a current transient recording unit, a transient feature memory, and a direction determination logic circuit. The input terminal of the current transient waveform recording unit is connected to the output terminal of the signal selection switch. The current transient waveform recording unit samples the fault current waveform at a sampling frequency range of 6.4kHz to 12.8kHz and stores the sampled data in the transient feature memory. The transient characteristic memory pre-stores transient waveform templates for positive fault current and transient waveform templates for negative fault current. The first input terminal of the direction determination logic circuit is connected to the output terminal of the voltage sampling circuit, the second input terminal of the direction determination logic circuit is connected to the data output terminal of the transient feature memory, and the third input terminal of the direction determination logic circuit is connected to the output terminal of the phase comparator. In step S5, when the fault direction flag bit output by the phase comparator is invalid or the AC voltage amplitude detected by the voltage sampling circuit is lower than a preset threshold of 10V, the direction determination logic circuit reads the fault current transient sampling data within the first half cycle after the fault occurs from the transient feature memory, performs a first correlation calculation with the fault current transient waveform template in the positive direction, and performs a second correlation calculation with the fault current transient waveform template in the reverse direction. If the first correlation is greater than the second correlation, the positive direction is output as the fault direction flag bit; if the second correlation is greater than the first correlation, the reverse direction is output as the fault direction flag bit; if the first correlation is equal to the second correlation, the positive direction is output as the fault direction flag bit, and this fault direction flag bit replaces the fault direction flag bit output by the phase comparator and is written into the fault alarm data packet.

8. The method for alarming faults in a distribution box according to claim 7, characterized in that, In step S5, when the fault direction flag bit output by the phase comparator is in an effective state and the AC voltage amplitude detected by the voltage sampling circuit is greater than or equal to the upper limit of the preset threshold range of 20V, the direction determination logic circuit reads the fault current transient sampling data in the first half cycle after the fault occurs from the transient feature memory as the transient sample of the current fault. According to the value of the fault direction flag bit output by the phase comparator, the transient sample is stored in the positive direction template buffer or the negative direction template buffer corresponding to the value in the transient feature memory. The direction determination logic circuit performs a sliding weighted average operation on the transient samples of at least five most recent faults stored in the positive direction template buffer, and replaces the positive direction fault current transient waveform template stored in the transient feature memory with the result of the operation. It also performs a sliding weighted average operation on the transient samples of at least five most recent faults stored in the negative direction template buffer, and replaces the negative direction fault current transient waveform template stored in the transient feature memory with the result of the operation.

9. A power distribution box fault alarm system, characterized in that, It includes multiple distribution boxes, fault detection and alarm devices installed in each distribution box, a cloud server, and a user terminal applet; The fault detection alarm device includes an audible and visual alarm with an independent power supply installed on the outer wall of the distribution box, a fault indicator host installed on the front panel of the distribution box, short circuit detection sensors sleeved around the periphery of each phase cable inside the distribution box, grounding detection sensors sleeved around the periphery of the three-phase cables inside the distribution box, and a wireless communication module installed inside the distribution box. The trigger signal input terminal of the audible and visual alarm is connected to the alarm output terminal of the fault indicator host via a wired connection. The wireless communication module is connected to the relay remote transmission signal output terminal of the fault indicator host. The wireless communication module has the number information of the distribution box pre-stored. The short circuit detection sensor and the grounding detection sensor are respectively connected to the fault indicator host via optical fiber. The fault indicator host is equipped with a CT power supply unit, rectifier and voltage regulator circuit, energy storage capacitor, voltage comparator, electronic switch, power failure detection circuit, narrowband IoT communication backup module, data buffer register, microcontroller, ferroelectric memory, voltage sampling circuit, phase comparator, signal selection switch, current transient waveform recording unit, transient feature memory and direction determination logic circuit. The input terminal of the CT power supply unit is connected to the secondary winding of the short circuit detection sensor and the secondary winding of the grounding detection sensor. The output terminal of the CT power supply unit is connected to the input terminal of the rectifier and voltage regulator circuit. The output terminal of the rectifier and voltage regulator circuit is simultaneously connected to the power supply terminal of the internal working circuit of the fault indicator host, the positive terminal of the energy storage capacitor, and the positive input terminal of the voltage comparator. A reference voltage is connected to the negative input terminal of the voltage comparator, the output terminal of the voltage comparator is connected to the control terminal of the electronic switch, the input terminal of the electronic switch is connected to the positive terminal of the energy storage capacitor, and the output terminal of the electronic switch is connected to the power supply input terminal of the wireless communication module. The input of the power failure detection circuit is connected to the output of the rectifier and voltage regulator circuit. The output of the power failure detection circuit is connected to the interrupt pin of the microcontroller. The narrowband IoT communication backup module is connected to the microcontroller through a serial peripheral interface. The narrowband IoT communication backup module has the number information of the distribution box pre-stored. The data cache register is connected to the microcontroller. The ferroelectric memory is connected to the microcontroller through an SPI interface. The input terminal of the voltage sampling circuit is connected to the input terminal of each phase cable in the distribution box through a resistor divider network. The first input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the short circuit detection sensor. The second input terminal of the signal selection switch is connected to the signal output terminal of the secondary winding of the grounding detection sensor. The output terminal of the signal selection switch is connected to the second input terminal of the phase comparator. The first input terminal of the phase comparator is connected to the output terminal of the voltage sampling circuit. The input terminal of the current transient waveform recording unit is connected to the output terminal of the signal selection switch, the output terminal of the current transient waveform recording unit is connected to the data input terminal of the transient feature memory, the transient feature memory contains a forward fault current transient waveform template and a reverse fault current transient waveform template, the first input terminal of the direction determination logic circuit is connected to the output terminal of the voltage sampling circuit, the second input terminal of the direction determination logic circuit is connected to the data output terminal of the transient feature memory, and the third input terminal of the direction determination logic circuit is connected to the output terminal of the phase comparator. The wireless communication module communicates with the cloud server via the 4G Cat.1 communication standard, and the narrowband IoT communication backup module communicates with the cloud server via the NB-IoT communication standard. The cloud server is equipped with a fault tree analysis engine, which pre-stores a topology table of the construction site distribution boxes. The topology table records the hierarchical relationship of each distribution box number, the number of the superior distribution box, and the number of the subordinate distribution boxes. The cloud server communicates with the user terminal applet.