Electric energy meter on-site verification safety early warning system and method

Abstract

The invention relates to the field of electric energy metering device detection safety, in particular to an electric energy meter on-site verification safety early warning system and method. The data processing unit is used for converting the signal into digital waveform data; the data analysis unit is used for extracting a characteristic parameter set of risk early warning; the hierarchical interrupt control unit is used for generating a hardware interrupt signal representing a risk level when detecting that a risk condition is met; the main control unit is used for receiving the hardware interrupt signal and starting a response program according to the risk level; the early warning recording unit is used for outputting risk warning information; characteristic parameters such as fundamental waves, harmonic waves, voltage flicker and current change rate are extracted through a data analysis unit; the hierarchical interrupt control unit carries out data comparison and generates interrupt signals corresponding to risk levels, the main control unit drives the early warning recording unit to output hierarchical warning information, and the early warning system can trigger targeted early warning at the initial stage of PT / CT abnormity and supports operation disposal and afterwards tracing.

Description

Technical Field

[0001] This invention relates to the field of safety testing for electricity metering devices, and in particular to a safety early warning system and method for on-site verification of electricity meters. Background Technology

[0002] In the field of electricity metering, the on-site periodic verification of electricity meters at key points is a crucial link in ensuring the fairness of power grid trade settlement and operational safety. To ensure verification accuracy, operators need to connect the verification instrument to the secondary circuit of the operating voltage transformer and current transformer, which poses safety risks. In the current technology, the verification work mainly relies on the experience of operators to manually monitor the data. Although some devices are equipped with simple voltage drop or current over-limit indication functions, their core logic is still based on static threshold comparison of low-frequency sampling, monitoring data through software polling, and triggering basic audible and visual alarms once an anomaly is detected.

[0003] However, such traditional solutions have serious drawbacks in practical applications. For example, the sampling rate and accuracy are insufficient to capture millisecond-level voltage spikes before a PT secondary short circuit or the slow current drop before a CT secondary open circuit, leading to severe delays or even failures in early warning. Secondly, the software polling-based response mechanism has an inherent delay of hundreds of milliseconds, making it impossible to cut off or alarm in time at the initial moment of a fault, thus failing to effectively avoid personal and equipment safety risks. Furthermore, its warning information is usually limited to vague indicator lights or buzzers, failing to clearly convey the specific type, severity, and handling recommendations of the risk to operators, increasing the risk of accidents. The possibility of misjudgment and improper handling is not the most important issue. Existing equipment generally lacks the ability to proactively intervene in the risk of open circuit in CT secondary circuits. That is, when an open circuit risk is detected, it cannot automatically perform a physical short-circuit operation to eliminate the high voltage hazard. It still relies heavily on the manual operation procedure of "short-circuit first, then disconnect the wire," which is very easy for accidents to occur due to human negligence. Finally, existing equipment generally lacks the ability to record and trace complete data of abnormal events. It cannot provide the original waveforms and logs required for accident analysis, which is not conducive to verification quality management and accident review. Therefore, it is difficult to meet the needs of modern high-safety and high-reliability power metering field operations.

[0004] Based on the above problems, we propose a safety early warning system and method for on-site verification of electrical energy meters. Summary of the Invention

[0005] Therefore, the technical problem to be solved by this invention is to achieve early and accurate identification of risks such as secondary short circuit of PT and secondary open circuit of CT, millisecond-level response warning, multi-dimensional information transmission and full-process data traceability, reduce manpower input and operational risks, and improve the safety and efficiency of on-site verification work.

[0006] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a power meter on-site verification safety early warning system, which includes a data acquisition unit for acquiring three-phase voltage signals and three-phase current signals, and outputting corresponding analog conditioning signals; A data processing unit, connected to the data acquisition unit, is used to convert the analog conditioning signal into digital waveform data; A data analysis unit, connected to the data processing unit, is used to perform signal processing on the digital waveform data to extract a set of feature parameters for risk warning. A graded interrupt control unit, connected to the data analysis unit, is used to compare the set of feature parameters with a preset risk feature library and thresholds. When a risk condition is detected, a hardware interrupt signal representing the risk level is generated. The main control unit, connected to the hierarchical interrupt control unit, is used to receive the hardware interrupt signal and, according to the risk level represented by the interrupt signal, initiate the corresponding response program. The early warning recording unit is connected to the main control unit and is used to output risk warning information. When it is determined that there is a risk of open circuit in the secondary circuit of the current transformer, it performs an automatic short-circuit protection operation on the secondary circuit of the current transformer.

[0007] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the data acquisition unit includes multiple independent voltage sampling circuits and multiple independent current sampling circuits; wherein, each voltage sampling circuit is used to acquire the corresponding phase voltage signal, and each current sampling circuit is used to acquire the corresponding phase current signal.

[0008] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the data analysis unit performs Fourier transform on the digital waveform data to obtain the fundamental amplitude and harmonic components, and obtains the total harmonic distortion rate based on the fundamental amplitude and the harmonic components; the data analysis unit continuously extracts voltage data using a sliding window and obtains the short-time flicker value reflecting the degree of instantaneous voltage fluctuation; and the data analysis unit processes the current data to obtain parameters characterizing the rate of current change.

[0009] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the hierarchical interruption control unit is provided with a feature library for identifying risks; The feature library includes a first type of feature group and a second type of feature group; The first type of feature group is used to identify the short-circuit risk in the secondary circuit of the voltage transformer. The second type of feature group is used to identify the risk of open circuit in the secondary circuit of a current transformer.

[0010] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the graded interruption control unit is provided with three levels of thresholds, which are set as early warning threshold, alarm threshold and emergency threshold respectively, based on the characteristic parameters of the equipment during normal operation; When the set of feature parameters exceeds the warning threshold, it is determined to be a potential risk; When the set of feature parameters matches the risk feature library and exceeds the alarm threshold, it is determined to be a clear risk; When the set of feature parameters matches the risk feature library and exceeds the emergency threshold, it is determined to be a serious risk.

[0011] In a preferred embodiment of the on-site verification safety early warning system for electricity meters according to the present invention: the main control unit is also connected to the data acquisition unit, data processing unit, data analysis unit and early warning recording unit respectively to coordinate the working sequence of each unit; after receiving an interruption signal, the main control unit immediately suspends the current data processing task and calls the preset hierarchical response program to output control instructions containing early warning level, risk type and characteristic parameters to the early warning recording unit.

[0012] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the early warning recording unit consists of an audible and visual alarm module, a voice broadcast module, a data storage module, and a CT secondary short-circuit module; wherein, the audible and visual alarm module is used to output corresponding visual and auditory warning signals according to the risk level, the voice broadcast module is used to broadcast structured voice information including event time, phase, and fault type, the data storage module is used to automatically record the original waveform data and event log of a preset number of cycles before and after triggering the early warning event, and the CT secondary short-circuit module is used to automatically short-circuit the secondary winding of the current transformer when receiving the corresponding risk level control command issued by the main control unit.

[0013] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the CT secondary short-circuit module includes an electromagnetic relay, whose normally closed contact is connected across the secondary output terminals of the current transformer; and wherein, the electromagnetic relay is in a closed conducting state by default; when receiving a drive signal from the main control unit, it switches to an open state to allow normal verification; and when receiving a short-circuit command from the main control unit, it switches back to a closed state to perform protection operation.

[0014] In a preferred embodiment of the power meter field verification safety early warning system of the present invention: the CT secondary short-circuit module further includes a status feedback module for monitoring the on / off status of relay contacts and feeding back the status signal to the main control unit; when the status feedback module does not detect the expected current, the main control unit triggers an emergency alarm for short-circuit failure.

[0015] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a safety early warning method for on-site verification of power meters, which includes acquiring three-phase voltage signals and three-phase current signals, and converting the signals into digital waveform data; The digital waveform data is processed to extract a set of characteristic parameters for identifying the short-circuit risk of the secondary circuit of the voltage transformer and the open-circuit risk of the secondary circuit of the current transformer. The set of feature parameters is compared in real time with a preset risk feature library and thresholds to determine whether there are any abnormal situations that meet the risk level. When an abnormal situation that meets the risk level is determined to exist, an interrupt signal corresponding to the risk level is generated; In response to the interrupt signal, the system outputs risk warning information corresponding to the risk level to the operator, and automatically short-circuits the secondary winding of the current transformer when it is determined that there is a risk of open circuit in the secondary circuit of the current transformer.

[0016] The beneficial effects of this invention are as follows: The data acquisition unit acquires the complete waveforms of three-phase voltage and current; the data analysis unit extracts characteristic parameters such as fundamental frequency, harmonics, voltage flicker, and current change rate; the hierarchical interruption control unit compares the set of characteristic parameters with a preset risk feature library and three-level thresholds in real time. Upon matching, an interrupt signal corresponding to the risk level is generated. The main control unit then drives the early warning recording unit to output hierarchical warning information. When a risk of open circuit in the secondary circuit of the current transformer is determined, the CT secondary short-circuit module is triggered to automatically short-circuit the winding, while storing the original waveforms before and after the event. This setting allows for targeted early warnings to be triggered in the early stages of PT / CT anomalies, and automatic elimination of high-voltage hazards when an open circuit risk in the CT is detected. Operators can promptly handle the situation based on the risk level and voice prompts, and conduct post-event analysis. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A block diagram of a field verification safety early warning system for electrical energy meters is shown. Figure 2 The circuit diagram of single-channel voltage sampling principle is shown; Figure 3 The circuit diagram of single-channel voltage sampling principle is shown; Figure 4 A schematic diagram of the workflow of the on-site verification safety early warning system for electricity meters is shown. Figure 5 A schematic diagram of the FFT processing flow in a DSP is shown; Figure 6 The schematic diagram of the CT secondary automatic short-circuit protection module is shown. Figure 7 A schematic diagram of the CT secondary short-circuit module's working process is shown. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0020] Reference Figures 1-7 This embodiment provides a safety early warning system for on-site verification of electricity meters, including: Data acquisition unit 1 is used to acquire three-phase voltage signals and three-phase current signals, and output corresponding analog conditioning signals; Data processing unit 2, connected to data acquisition unit 1, is used to convert analog conditioning signals into digital waveform data; The TI ADS1278IPAPR, a 24-bit resolution 8-channel ADC chip, is selected as the core device. This chip supports a maximum sampling rate of 144kSPS, while this solution uses a sampling rate of 16kSPS. At a standard 50Hz power grid frequency, this sampling rate can achieve high-density data acquisition of 320 sample points per cycle, which is more than 30 times higher than that of traditional equipment. It can completely capture the millisecond-level waveform fluctuations and distortion characteristics before faults such as PT short circuit and CT open circuit. Furthermore, the digitized data of the ADC chip is transmitted to the data analysis unit 3 in real time through the SPI interface. Data analysis unit 3, connected to data processing unit 2, is used to perform signal processing on digital waveform data to extract a set of feature parameters for risk warning. The characteristic parameter set includes fundamental amplitude, total harmonic distortion rate, short-time voltage flicker, and current change rate. These four parameters can be used to identify the short-circuit risk of the secondary circuit of a voltage transformer (PT) and the open-circuit risk of the secondary circuit of a current transformer (CT). The hierarchical interrupt control unit 4 is connected to the data analysis unit 3 and is used to compare the feature parameter set with the preset risk feature library and threshold. When the risk conditions are detected, a hardware interrupt signal representing the risk level is generated. The main control unit 5 is connected to the hierarchical interrupt control unit 4 and is used to receive hardware interrupt signals and start the corresponding response program according to the risk level represented by the interrupt signal. The early warning recording unit 6 is connected to the main control unit 5. It is used to output risk warning information and, when it is determined that there is an open circuit risk in the secondary circuit of the current transformer, it performs an automatic short-circuit protection operation on the secondary circuit of the current transformer.

[0021] In one embodiment provided in this application, the data acquisition unit 1 includes multiple independent voltage sampling circuits and multiple independent current sampling circuits; wherein, each voltage sampling circuit is used to acquire the corresponding phase voltage signal, and each current sampling circuit is used to acquire the corresponding phase current signal.

[0022] The data acquisition unit 1 is mainly used for signal acquisition, employing 6 independent acquisition channels corresponding to three-phase voltage and three-phase current signals respectively. Each voltage acquisition branch uses metal film sampling resistors with 0.05% accuracy and 5ppm / ℃ low temperature drift, such as UPR-1 / 2-10R±0.05%±5PPM and EE1 / 4W-6K±0.05%±5PPM, which, together with the signal conditioning circuit composed of operational amplifiers, attenuate the 0-400V AC voltage signal to the 0-3.3V range adapted by the ADC chip. Each current acquisition branch uses sampling resistors of the same accuracy level, combined with the secondary side signal conversion circuit of the current transformer, to achieve accurate acquisition of 0-5A AC current signals. The signal conditioning circuit has a built-in second-order low-pass filter and electromagnetic interference suppression circuit, which can effectively filter out high-frequency noise in the field verification environment and ensure the reliability of the original signal.

[0023] Specifically, such as Figure 2 As shown, the voltage acquisition branch uses 0.05% / 5ppm metal film precision resistors, where R1-R8 precision resistors form a sampling and voltage divider network, and K1, K2, K3, and K4 are range switching relays for 60V, 100V, 240V, and 480V ranges respectively, ensuring high-precision measurement of any voltage value within the 0-480V voltage range; the voltage after voltage division is then conditioned to 0-3.3V by a follower circuit composed of operational amplifier U1 to adapt to ADC operation; R12 and C3 form a low-pass filter to filter out high-frequency noise in the circuit; Figure 2Taking phase A voltage acquisition as an example, the principle of phase B and phase C voltage acquisition is the same.

[0024] Furthermore, such as Figure 3 As shown, the current acquisition branch uses a 5A / 5mA current clamp for measurement. The current signals at IA+ and IA- are full-scale 5mA current signals. Through sampling resistor R22 (selecting a precision resistor of 0.05% / 5ppm), the current signal is converted into a 0-1V voltage signal, which is then amplified to 0-3.3V by operational amplifier U2 to adapt to the ADC chip's operating range. R27 and C23 form a low-pass filter to filter out high-frequency noise in the circuit. Figure 3 Taking phase A current acquisition as an example, the principle of phase B and phase C current acquisition is the same; different range current clamp meters (1A, 10A, 100A, etc.) can also be configured here according to different application scenarios.

[0025] In one embodiment provided in this application, the data analysis unit 3 performs a Fourier transform on the digital waveform data to obtain the fundamental amplitude and harmonic components, and obtains the total harmonic distortion rate based on the fundamental amplitude and harmonic components.

[0026] The data analysis unit 3 can utilize TI's high-performance 32-bit floating-point digital signal processor (DSP) TMS320F28335ZJZA. This processor features a 150MHz clock frequency and a hardware multiplier, enabling it to efficiently execute complex digital signal processing algorithms. Its core processing flow includes, for example: Figure 5 As shown, a 1024-point FFT transformation is performed on the digitized waveform data to separate the fundamental amplitude and the 1st to 31st harmonic components.

[0027] Substituting the following formula 31 times yields... Calculate the total harmonic distortion, where U1 is the fundamental voltage, and U2-U... 31 These are the effective values ​​of each harmonic; the calculation method for current harmonics is the same.

[0028] In one embodiment provided in this application, the data analysis unit 3 continuously captures voltage data using a sliding window and obtains a short-time flicker value that reflects the degree of instantaneous voltage fluctuation; and the data analysis unit 3 processes current data to obtain parameters characterizing the rate of current change.

[0029] Specifically, a 200ms sliding window is used to continuously capture voltage data. The short-time flicker value Pst is calculated according to the standard in IEC 61000-4-15:2010 Electromagnetic Compatibility (EMC) to reflect the degree of instantaneous voltage fluctuation. The first derivative of the current data is performed to obtain the current change rate (di / dt) and identify the current sudden change characteristics. The fundamental amplitude, total harmonic distortion, voltage flicker Pst, and current sudden change rate generated by the above processing constitute a multi-dimensional feature parameter set, which is transmitted to the hierarchical interrupt control unit 4 through the data bus.

[0030] In one embodiment provided in this application, the hierarchical interrupt control unit 4 is provided with a feature library for identifying risks; The feature library includes a first type of feature group and a second type of feature group; The first type of feature group is used to identify the short-circuit risk in the secondary circuit of voltage transformers. The second type of feature group is used to identify the risk of open circuit in the secondary circuit of a current transformer.

[0031] The hierarchical interrupt control unit 4 is mainly responsible for risk identification and interrupt triggering. It has a built-in programmable logic device (CPLD) and a storage module. The storage module pre-stores two types of fault feature libraries. The first type of PT secondary circuit short circuit feature library includes: sudden drop in A-phase voltage! PT secondary circuit short circuit risk; A-phase voltage flicker frequency exceeds the standard, suspected precursor to PT secondary short circuit; A-phase voltage is continuously low (severe waveform distortion), PT secondary short circuit warning. The second type of CT secondary circuit open circuit feature library includes: sudden drop in A-phase current! CT secondary circuit open circuit risk; A-phase current flicker frequency exceeds the standard, suspected precursor to CT secondary open circuit; A-phase current is continuously low, CT secondary short circuit warning.

[0032] Meanwhile, the hierarchical interrupt control unit 4 also pre-stores three levels of thresholds. Based on the characteristic parameters during normal equipment operation, three levels of thresholds are set: warning, alarm, and emergency. Specifically, the CPLD compares the received multi-dimensional characteristic parameter set with the feature library and thresholds in real time. When the parameter only exceeds the warning threshold, it is determined to be a potential risk. When the parameter matches the fault feature library and exceeds the alarm threshold, it is determined to be a clear risk. When the parameter matches the fault feature library and exceeds the emergency threshold, it is determined to be a serious risk. Corresponding to different risk levels, the CPLD immediately generates low, medium, and high level hardware interrupt signals, which are transmitted to the main control unit 5 through the interrupt interface. The interrupt response delay is controlled within 10ms, eliminating the waiting delay of the traditional polling mode.

[0033] In one embodiment provided in this application, the main control unit 5 is also connected to the data acquisition unit 1, the data processing unit 2, the data analysis unit 3 and the early warning recording unit 6 respectively, so as to coordinate the working sequence of each unit.

[0034] In one embodiment provided in this application, after receiving an interrupt signal, the main control unit 5 immediately suspends the current data processing task and calls a preset graded response program to output a control command containing the warning level, risk type and characteristic parameters to the warning recording unit 6.

[0035] Among them, the main control unit 5 can use an STM32F407ZGT6 processor, which has the ability to manage multiple interrupt priorities and can prioritize responding to the emergency level interrupt signals of the hierarchical interrupt control module.

[0036] Furthermore, when the main control unit 5 receives an interrupt signal, the processor immediately suspends the regular data processing task, calls the preset hierarchical response program, and outputs precise control instructions to the early warning recording unit 6, including key information such as early warning level, risk type, and characteristic parameters; at the same time, the main control unit 5 is responsible for coordinating the timing synchronization of each module to ensure the continuity of the sampling, analysis, and early warning process.

[0037] In one embodiment provided in this application, the early warning recording unit 6 consists of an audible and visual alarm module 61, a voice broadcast module 62, a data storage module 63, and a CT secondary short-circuit module 64.

[0038] The audible and visual alarm module 61 uses tri-color LEDs and an adjustable frequency buzzer. The warning level corresponds to a slow flashing yellow light (1Hz) + low-frequency buzzer (2Hz); the alarm level corresponds to a fast flashing orange light (5Hz) + medium-frequency buzzer (5Hz); and the emergency level corresponds to a constant red light + high-frequency buzzer (10Hz). The voice broadcast module 62 uses a SYN6288 voice synthesis chip, pre-stores more than 100 voice commands, and can broadcast "2025-11-05 11:30:00, A-phase current suddenly drops, CT..." The system displays specific information such as "Secondary open circuit alarm, please check wiring," and prioritizes abnormal broadcasts over scheduled broadcasts. The broadcast type and cycle can be flexibly set. The data storage module 63, with its large-capacity memory, can automatically record the original waveforms, characteristic parameters, risk levels, and operation logs for 10 cycles before and after an abnormal event. The stored data can be saved locally or transferred to computer backend software via USB. Additionally, the early warning recording unit 6 may include a communication module, employing multiple communication methods such as Bluetooth, USB, and RS232 to upload abnormal event data to the control tablet or backend management system in real time. The uploaded content includes event records and key parameters, enabling remote monitoring and centralized management.

[0039] It must be clarified that the secondary side of the current transformer (CT) must not be open-circuited during operation. Once an open circuit occurs, the primary current will be entirely converted into excitation current, leading to severe core saturation and generating an induced electromotive force of several thousand volts. This could not only break down the insulation and damage the equipment, but also pose a fatal risk of electric shock to personnel on site. Although there are operating procedures in traditional calibration work, such as short-circuiting first and then disconnecting the wires, open-circuit accidents still occur due to human negligence or loose wiring. Therefore, a CT secondary short-circuit module 64 is set up to automatically short-circuit the secondary winding of the current transformer when it receives a control command of the corresponding risk level issued by the main control unit 5. The corresponding risk level refers to the risk of open circuit in the secondary circuit of the current transformer or an emergency interruption signal.

[0040] In one embodiment provided in this application, the CT secondary short-circuit module 64 includes an electromagnetic relay, whose normally closed contacts are connected across the secondary output terminals of the current transformer; and the electromagnetic relay is in a closed conducting state by default to ensure that the secondary winding of the current transformer is forcibly short-circuited; when a drive signal is received from the main control unit 5, it switches to an open state to allow normal verification; and when a short-circuit command is received from the main control unit 5, it switches back to a closed state to perform protection operation.

[0041] In one embodiment provided in this application, the CT secondary short-circuit module further includes a status feedback module for monitoring the on / off state of the relay contacts and feeding back the status signal to the main control unit 5; when the status feedback module does not detect the expected current, the main control unit 5 triggers an emergency alarm for short-circuit failure.

[0042] Furthermore, the CT secondary short-circuit module 64 consists of an electromagnetic relay group, a drive circuit, and a status feedback unit, and is installed between the CT secondary circuit access terminal and the calibrator. Among them, the electromagnetic relay group adopts three sets of single-pole double-throw relays, corresponding to the secondary windings of the three-phase CT (one set of relays is configured for each phase CT). The rated current of the relay contacts is ≥10A and the withstand voltage is ≥250V to ensure short-circuit reliability. The drive circuit uses optocoupler isolation (such as EL3H7-G) and driver (such as ULN2003) to drive the relay coil, ensuring that the control signal is isolated from the high-voltage circuit and improving safety. The status feedback module monitors the on / off state of the relay through Hall sensors and feeds back the status signal to the main control unit 5 to realize closed-loop control.

[0043] like Figure 6As shown, the 3.3V power supply is connected to the anode pins K1, K2, and K3 of the three optocoupler isolators U1 via 330Ω current-limiting resistors R44, R46, and R48 to receive control signals from the main control unit 5. The cathodes of the optocouplers are grounded to form a signal isolation loop on the input side. The open-collector pins of the optocouplers are connected to the +12V power supply via 4.7KΩ pull-up resistors R43, R45, and R47, and are connected to the input pins IN1, IN2, and IN3 of the relay driver chip U2, respectively. The common terminal COM of the driver chip U2 is connected to +12V, and the ground line GN... D is grounded, and its output pins OUT1, OUT2, and OUT3 are respectively connected to one end of the coil of the three electromagnetic relays, and the other end of the coil is grounded, thus forming a complete drive circuit. The normally closed contact of each relay is connected between the secondary output terminals of the corresponding current transformer to ensure that the secondary winding of the CT is always in a safe short-circuit state when the relay coil is de-energized. In addition, a Hall sensor is connected in series in each short-circuit circuit to monitor in real time whether current flows through the short contact and send the status feedback signal back to the main control unit 5 to verify whether the short-circuit action is successfully executed, thus forming a closed-loop control.

[0044] Specifically, taking phase A as an example, the secondary output terminals IA+ and IA− of the CT are connected to the input terminals of the short-circuit module, respectively. One normally closed relay has its contacts connected across IA+ and IA−. The normally closed contacts of the relay are shorted by default to prevent failure to protect against sudden power outages or program crashes that could lead to secondary open circuits. When monitoring begins, the MCU controls pin K1, which energizes the relay coil via optocoupler U1 and ULN2003, opening the normally closed contacts and allowing normal power supply on site. When the main control program detects a "CT open circuit risk" interruption, the MCU immediately controls pin K1, which de-energizes the relay coil via optocoupler U1 and ULN2003, shorting the secondary CT through its contacts. Simultaneously, a Hall current sensor ACS712 is connected in series in the short-circuit circuit to read the ACS712 voltage in real time. If the voltage is >0.1V (indicating current flow), the short circuit is considered successful; otherwise, an emergency alarm for "short circuit failure" is triggered.

[0045] like Figure 7The diagram illustrates the workflow of the short-circuit module. First, risk identification is performed by the data analysis unit 3. The DSP processor calculates the current change rate (di / dt). When current is detected, it indicates a CT secondary open circuit risk, generating an "emergency level" interrupt signal. Upon receiving the emergency level interrupt signal, the main control unit 5 immediately sends a drive command to the short-circuit module. Upon receiving the command, the drive circuit triggers the electromagnetic relay coil to de-energize via optocoupler isolation, switching the relay contacts from "normally open" to "normally closed," short-circuiting the CT secondary winding (e.g., short-circuiting the secondary terminals of phase A CT). The status feedback module feeds back the relay's on / off status (e.g., "short-circuited" or "not short-circuited") to the main control unit 5. The main control module then announces via the voice broadcast module 63, "CT secondary open circuit short-circuited, please check wiring." After the operator eliminates the open circuit fault, the main control unit 5 sends a "disconnect" command via the device's "reset" button or a background command, restoring the relay contacts to the "normally open" state, and the short-circuit module 64 stops working.

[0046] Reference Figures 1-7 This embodiment provides a safety early warning method for on-site verification of power meters, including acquiring three-phase voltage signals and three-phase current signals, and converting the signals into digital waveform data; Signal processing is performed on digital waveform data to extract a set of characteristic parameters for identifying the short-circuit risk of the secondary circuit of voltage transformers and the open-circuit risk of the secondary circuit of current transformers. The feature parameter set is compared with the preset risk feature library and threshold in real time to determine whether there are any abnormal situations that meet the risk level. When an abnormal situation that meets the risk level is determined to exist, an interrupt signal corresponding to the risk level is generated; In response to the interrupt signal, the system outputs risk warning information corresponding to the risk level to the operator. When the main control unit detects the risk of open circuit in the current, it controls the CT secondary automatic protection module to short-circuit the current and adds a status readback pin. Specifically, when the risk of open circuit in the CT (including precursors) is detected, the CT secondary circuit is automatically short-circuited through relay switching, thereby eliminating the high voltage hazard from the source.

[0047] Specifically, such as Figure 4As shown, the on-site verification safety early warning method for power meters mainly involves the following steps: During the initialization phase, after the device is powered on, the main control unit 5 initializes and configures each unit, including ADC sampling rate, DSP program loading, CPLD threshold setting, and voice module baud rate, and then enters standby mode. Signal acquisition is then performed, with the data acquisition unit 1 acquiring three-phase voltage and current signals in real time. The signals are then digitized, and the acquired three-phase voltage and current signals are conditioned and filtered before being sent to the ADC chip to be converted into 24-bit digital data. Feature analysis and risk assessment are performed by the data analysis unit 3. The DSP processor receives the digitized data, performs FFT transformation and flicker analysis, generates a multi-dimensional feature parameter set, and transmits it to the CPLD. The CPLD compares the parameters with the feature library and thresholds to determine the risk level and generate a corresponding interrupt signal. The ARM processor receives the interrupt signal, drives the audible and visual alarm unit to issue a corresponding warning according to the risk level, controls the voice module to broadcast specific information, and simultaneously triggers data storage. The data storage module 63 automatically records event data and supports local USB export and remote background query.

[0048] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A safety early warning system for on-site verification of electrical energy meters, characterized in that: include, The data acquisition unit (1) is used to acquire three-phase voltage signals and three-phase current signals, and output corresponding analog conditioning signals; The data processing unit (2) is connected to the data acquisition unit (1) and is used to convert the analog conditioning signal into digital waveform data; The data analysis unit (3) is connected to the data processing unit (2) and is used to perform signal processing on the digital waveform data to extract a set of feature parameters for risk warning. The hierarchical interrupt control unit (4) is connected to the data analysis unit (3) and is used to compare the feature parameter set with the preset risk feature library and threshold. When the risk conditions are detected, a hardware interrupt signal representing the risk level is generated. The main control unit (5) is connected to the hierarchical interrupt control unit (4) and is used to receive the hardware interrupt signal and start the corresponding response program according to the risk level represented by the interrupt signal. The early warning recording unit (6) is connected to the main control unit (5) and is used to output risk warning information. When it is determined that there is an open circuit risk in the secondary circuit of the current transformer, it performs an automatic short-circuit protection operation on the secondary circuit of the current transformer.

2. The on-site verification and safety early warning system for electricity meters according to claim 1, characterized in that: The data acquisition unit (1) includes multiple independent voltage sampling circuits and multiple independent current sampling circuits; Each voltage sampling circuit is used to acquire the corresponding phase voltage signal, and each current sampling circuit is used to acquire the corresponding phase current signal.

3. The on-site verification safety early warning system for electrical energy meters according to claim 1 or 2, characterized in that: The data analysis unit (3) performs a Fourier transform on the digital waveform data to obtain the fundamental amplitude and harmonic components, and obtains the total harmonic distortion rate based on the fundamental amplitude and the harmonic components. The data analysis unit (3) continuously extracts voltage data by using a sliding window and obtains short-time flicker values ​​that reflect the degree of instantaneous voltage fluctuation; and the data analysis unit (3) processes current data to obtain parameters that characterize the rate of current change.

4. The on-site verification and safety early warning system for electricity meters according to claim 1, characterized in that: The hierarchical interrupt control unit (4) is equipped with a feature library for identifying risks; The feature library includes a first type of feature group and a second type of feature group; The first type of feature group is used to identify the short-circuit risk in the secondary circuit of the voltage transformer. The second type of feature group is used to identify the risk of open circuit in the secondary circuit of a current transformer.

5. The on-site verification safety early warning system for electrical energy meters according to claim 4, characterized in that: The hierarchical interruption control unit (4) is equipped with three levels of thresholds. The three levels of thresholds are set as early warning threshold, alarm threshold and emergency threshold respectively, based on the characteristic parameters of the equipment during normal operation. When the set of feature parameters exceeds the warning threshold, it is determined to be a potential risk; When the set of feature parameters matches the risk feature library and exceeds the alarm threshold, it is determined to be a clear risk; When the set of feature parameters matches the risk feature library and exceeds the emergency threshold, it is determined to be a serious risk.

6. The on-site verification safety early warning system for electrical energy meters according to claim 1 or 5, characterized in that: The main control unit (5) is also connected to the data acquisition unit (1), data processing unit (2), data analysis unit (3) and early warning recording unit (6) respectively, so as to coordinate the working sequence of each unit; Upon receiving an interrupt signal, the main control unit (5) immediately suspends the current data processing task and calls the preset graded response program to output control instructions containing the warning level, risk type and characteristic parameters to the warning recording unit (6).

7. The on-site verification safety early warning system for electricity meters according to claim 6, characterized in that: The early warning recording unit (6) consists of an audible and visual alarm module (61), a voice broadcast module (62), a data storage module (63), and a CT secondary short-circuit module (64). The audible and visual alarm module (61) is used to output corresponding visual and auditory warning signals according to the risk level. The voice broadcast module (62) is used to broadcast structured voice information including event time, phase, and fault type. The data storage module (63) is used to automatically record the original waveform data and event log of a preset number of cycles before and after triggering the early warning event. The CT secondary short-circuit module (64) is used to automatically short-circuit the secondary winding of the current transformer when it receives the corresponding risk level control command issued by the main control unit (5).

8. The on-site verification safety early warning system for electricity meters according to claim 7, characterized in that: The CT secondary short-circuit module (64) includes an electromagnetic relay, whose normally closed contacts are connected across the secondary output terminals of the current transformer; and, The electromagnetic relay is in a closed conducting state by default; when it receives a drive signal from the main control unit (5), it switches to an open state to allow normal verification; when it receives a short-circuit command from the main control unit (5), it switches back to a closed state to perform protection operation.

9. The on-site verification safety early warning system for electrical energy meters according to claim 8, characterized in that: The CT secondary short-circuit module also includes a status feedback module, which is used to monitor the on / off status of the relay contacts and feed the status signal back to the main control unit (5); when the status feedback module does not detect the expected current, the main control unit (5) triggers an emergency alarm for short-circuit failure.

10. A method for on-site verification and safety early warning of electrical energy meters, characterized in that: Includes the on-site verification safety early warning system for electrical energy meters as described in any one of claims 1 to 9; as well as, Acquire three-phase voltage signals and three-phase current signals, and convert the signals into digital waveform data; The digital waveform data is processed to extract a set of characteristic parameters for identifying the short-circuit risk of the secondary circuit of the voltage transformer and the open-circuit risk of the secondary circuit of the current transformer. The set of feature parameters is compared in real time with a preset risk feature library and thresholds to determine whether there are any abnormal situations that meet the risk level. When an abnormal situation that meets the risk level is determined to exist, an interrupt signal corresponding to the risk level is generated; In response to the interrupt signal, the system outputs risk warning information corresponding to the risk level to the operator, and automatically short-circuits the secondary winding of the current transformer when it is determined that there is a risk of open circuit in the secondary circuit of the current transformer.

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