Calibration system, data acquisition system and method for monitoring a stray current de-magnetization event

Abstract

The application provides a kind of calibration system, data acquisition system and method for monitoring stray current magnetic bias event, and relates to the technical field of power system monitoring.The clock module receives absolute standard time signal and outputs absolute standard time and PPS second pulse;Multi-dimensional synchronous acquisition and control module sets trigger time ready flag according to current absolute standard time and preset output absolute standard time;After setting, when detecting the rising edge of PPS second pulse corresponding to preset output absolute standard time, control DC current source outputs DC current to transformer neutral point grounding loop;Current sensor samples grounding loop current, and when outputting first level when exceeding threshold, multi-dimensional synchronous acquisition and control module latches current time and uploads to stray current magnetic bias event analysis server;The server calculates the difference between each site's latched time and preset time to realize the synchronization of each site's built-in clock and alignment with absolute standard time.This application anchors all monitoring sites to the same global absolute standard time axis.

Description

Technical Field

[0001] This invention relates to the field of power system monitoring technology, specifically to a calibration system, data acquisition system, and method for monitoring stray current bias events. Background Technology

[0002] Stray current bias events are abnormal current phenomena in power systems caused by geomagnetic storms, DC transmission, and rail transit, which may lead to transformer core saturation, increased harmonics, and aggravated equipment losses. The impact of stray current bias events on equipment is difficult to observe and verify directly, necessitating an effective method to simulate and verify these events. Traditional monitoring relies on individual testing methods: such as clamp meter current measurement, chromatographic analysis of insulating oil, and manual inspection of vibration and noise. Inconsistent data timescales prevent the correlation between mechanical deformation and electrical anomalies. Stray current bias events, such as DC intrusions from rail transit, are characterized by both instantaneous (10ms level) and continuous (10s level) events. Sampling frequencies of 100kHz and above are typically used to accurately capture sudden current changes during start-up / stopping, such as inrush currents and oscillation decay processes, which may be smoothed out or missed at lower sampling frequencies. However, high sampling frequencies and continuous recording place high demands on system communication and storage hardware.

[0003] Existing technologies employ multiple independent clock sources such as BeiDou / GPS and NTP, resulting in a fragmented technical approach and an inability to verify the synchronization between distributed devices, leading to time discrepancies between different monitoring stations. Synchronization discrepancies distort the temporal correlation analysis of stray current events, making it difficult to capture cross-regional current propagation patterns (such as the path of stray currents entering the power grid transformer in subways), and affecting the accurate tracing of the causes of stray current magnetization events.

[0004] Existing waveform recording devices have a minimum sampling interval of 1 second, while the transient current changes generated by train start-stop are in the millisecond range (e.g., 10ms~100ms). Current technology cannot record the details of rapidly changing currents. Waveform distortion makes it impossible to reconstruct key features such as current peaks and harmonic distortions at the moment of fault during accident analysis, increasing the difficulty of fault diagnosis.

[0005] In existing technologies, DC current, vibration, and noise data are collected by independent systems, lacking a time alignment mechanism. Current sensors monitor electrical anomalies, such as neutral point DC bias; piezoelectric accelerometers reflect loose mechanical structures; and condenser microphones detect magnetostriction anomalies in the iron core. The existing discrete systems prevent data correlation, making it difficult to establish multi-dimensional fault models encompassing electrical, mechanical, and acoustic aspects. For example, it is impossible to distinguish between vibration and noise caused by DC bias and mechanical aging, leading to misdiagnosis. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a calibration system for monitoring stray current bias events, comprising: The clock module is used to receive external absolute standard time signals in real time and output absolute standard time and PPS second pulses according to the absolute standard time signals. The multidimensional synchronous acquisition and control module is used to determine whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source. Under the premise that the trigger time ready flag of the DC current source has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the interrupt response of the multidimensional synchronous acquisition and control module is triggered, and the DC current source is controlled to output DC current to the neutral point grounding circuit of the transformer in the corresponding power grid substation to simulate stray current bias event. The current sensor is used to sample the current signal of the transformer neutral point grounding circuit in the current power grid substation. When the voltage drop signal corresponding to the current signal is greater than the threshold of the voltage drop signal corresponding to the stray current bias event, it outputs the first level. The multi-dimensional synchronous acquisition and control module is also used to trigger the interrupt response of the multi-dimensional synchronous acquisition and control module when the first level is detected, and to latch the time of the built-in clock of the multi-dimensional synchronous acquisition and control module when the first level is detected. When the duration of the first level exceeds the first preset duration, the latched time is uploaded to the stray current bias event analysis server. The stray current bias event analysis server is used to calculate the difference between the time latched by the multi-dimensional synchronous acquisition and control module in each power grid substation and the preset output absolute standard time of the DC current source. Based on the difference, it sends a time calibration command to the multi-dimensional synchronous acquisition and control module of each power grid substation so that the built-in clock of the multi-dimensional synchronous acquisition and control module of each power grid substation is synchronized and aligned with the absolute standard time.

[0007] Furthermore, the stray current bias event analysis server is also used to configure the preset output absolute standard time of the DC current source and send it to the multi-dimensional synchronous acquisition and control module. The preset output absolute standard time of the DC current source is delayed by a second preset time compared with the absolute standard time of the sending operation.

[0008] Furthermore, in the multi-dimensional synchronous acquisition and control module, the specific method for determining whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source is as follows: The trigger time ready flag is set only when the current absolute standard time coincides with the time corresponding to the third preset time before the preset output absolute standard time of the DC current source. At other times, the setting operation is not performed.

[0009] Furthermore, the multi-dimensional synchronous acquisition and control module is also used to reset the trigger time ready flag when completing the operation of controlling the DC current source to output DC current to the neutral point grounding circuit of the transformer in the power grid substation.

[0010] A data acquisition system based on the calibration system for monitoring stray current bias events, wherein a current sensor is used to output a second level when the voltage drop signal corresponding to the current signal of the current substation is less than or equal to the voltage drop signal threshold corresponding to the stray current bias event. The multidimensional synchronous acquisition and control module is used to continuously acquire raw multidimensional data of the power grid substation status through a multidimensional sensor at a preset sampling frequency when the second level is detected. Using a first acquisition time window as the rolling period, at the end of each rolling first acquisition time window, it calculates the feature value set of the raw multidimensional data acquired within that first acquisition time window, sends the feature value set to the stray current bias event analysis server, and continuously stores the raw multidimensional data within a continuous time interval with the current time of the built-in clock as the endpoint and the second acquisition time window as the duration. When the first level is detected, the module acquires raw multidimensional data of the power grid substation status through a multidimensional sensor at a preset sampling frequency within a third acquisition time window. At the end of the third acquisition time window, the continuously stored raw multidimensional data and the raw multidimensional data acquired within the third acquisition time window are merged sequentially to obtain merged raw multidimensional data, which is then sent to the stray current bias event analysis server.

[0011] Furthermore, the multi-dimensional synchronous acquisition and control module integrates a sample-and-hold amplifier, which is used for multi-channel synchronous acquisition of monitoring data, with the sampling time deviation between channels being less than a preset time deviation.

[0012] Furthermore, the current sensor integrates a programmable amplifier circuit, which can amplify the voltage drop signal generated by the current in the grounding circuit.

[0013] Furthermore, the multidimensional synchronous acquisition and control module first responds to the time calibration command, and after the built-in clock of the multidimensional synchronous acquisition and control module of each power grid substation is synchronized and aligned with the absolute standard time, it then acquires the original multidimensional data of the power grid substation status.

[0014] A calibration method for monitoring stray current bias events includes the following steps: The clock module receives external absolute standard time signals in real time and outputs absolute standard time and PPS second pulses based on the absolute standard time signals. The multidimensional synchronous acquisition and control module determines whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source. If the trigger time ready flag of the DC current source has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the interrupt response of the multidimensional synchronous acquisition and control module is triggered, and the DC current source is controlled to output DC current to the neutral point grounding circuit of the transformer in the corresponding power grid substation to simulate stray current bias event. The current sensor samples the current signal of the transformer neutral point grounding circuit in the current power grid substation. When the voltage drop signal corresponding to the current signal is greater than the threshold of the voltage drop signal corresponding to the stray current bias event, the first level is output. When the first level is detected, the multi-dimensional synchronous acquisition and control module triggers an interrupt response and latches the time of the built-in clock of the multi-dimensional synchronous acquisition and control module when the first level is detected. When the duration of the first level exceeds the first preset duration, the latched time is uploaded to the stray current bias event analysis server. The stray current bias event analysis server calculates the difference between the time latched by the multi-dimensional synchronous acquisition and control module in each power grid substation and the preset output absolute standard time of the DC current source. Based on the difference, it sends a time calibration command to the multi-dimensional synchronous acquisition and control module of each power grid substation to synchronize the built-in clock of the multi-dimensional synchronous acquisition and control module of each power grid substation and align it with the absolute standard time.

[0015] A data acquisition method based on the above-mentioned calibration method for monitoring stray current bias events includes the following steps: The current sensor outputs a second level when the voltage drop signal corresponding to the current signal of the current substation in the current power grid is less than or equal to the threshold of the voltage drop signal corresponding to the stray current bias event; When the second level is detected, the multidimensional synchronous acquisition and control module continuously acquires raw multidimensional data of the power grid substation status through a multidimensional sensor at a preset sampling frequency. Using a first acquisition time window as the rolling cycle, at the end of each rolling first acquisition time window, it calculates the feature value set of the raw multidimensional data acquired within that first acquisition time window and sends the feature value set to the stray current bias event analysis server. The module also continuously stores raw multidimensional data within a continuous time interval, ending at the current time of the built-in clock and lasting for the second acquisition time window. When the first level is detected, the module acquires raw multidimensional data of the power grid substation status through a multidimensional sensor at a preset sampling frequency within a third acquisition time window. At the end of the third acquisition time window, the rolling stored raw multidimensional data and the raw multidimensional data acquired within the third acquisition time window are merged sequentially to obtain merged raw multidimensional data, which is then sent to the stray current bias event analysis server.

[0016] The beneficial effects of this invention are as follows: 1. This invention utilizes a globally unified stray current and magnetic bias event analysis server to distribute a unified preset absolute standard time of DC current source output to all distributed sites along the entire line. This controls all monitoring sites to synchronously output simulated DC current and magnetic bias events at the same absolute standard time. Furthermore, the difference between the built-in clock time of the multi-dimensional synchronous acquisition and control module latched at each site and the preset standard time of the DC current is used to calibrate the built-in clocks of all sites. This overcomes the limitations of existing technologies that can only achieve single-point time synchronization and cannot verify the synchronization accuracy across all sites. It allows all distributed monitoring sites to be anchored to the same global absolute standard time axis, providing a unified, reliable, and high-precision time reference for cross-site magnetic bias event timing comparison and accurate tracing of stray current propagation paths.

[0017] 2. This invention utilizes two independently configured external hardware interrupt channels, respectively connecting to the PPS second pulse synchronization trigger signal and the magnetic bias over-limit trigger signal, achieving nanosecond-level interrupt response without software polling detection. Simultaneously, it employs the built-in clock of the multi-dimensional synchronous acquisition and control module, calibrated at the absolute standard time level, as the latching reference. This resolves the irreconcilable timing contradiction between the BeiDou clock module's message transmission delay and the random triggering of transient events, enabling microsecond-level precise time latching at the instant of stray current magnetic bias event triggering. Combined with a raw multi-dimensional data recording scheme featuring pre-event rolling buffering, post-event continuous acquisition, and full-cycle timing merging, it can completely preserve the raw multi-dimensional waveform data of the entire process of a magnetic bias event from its inception, development, over-limit triggering to its dissipation. It accurately captures transient current mutations at the 10ms or even microsecond level, fully restoring the current peak value, harmonic distortion, and other characteristics at the moment of the fault, overcoming the shortcomings of existing technologies such as large recording intervals, transient waveform distortion, and loss of critical data before triggering. Attached Figure Description

[0018] Figure 1 This is a system block diagram of Embodiment 1 of the present invention.

[0019] Explanation of reference numerals in the attached diagram: 1-Clamp-type current sensor; 2-Piezoelectric accelerometer; 3-Capacitive microphone; 4-DC current source; 5-BeiDou clock module; 6-Multi-dimensional synchronous acquisition and control module; 7-Communication module; 8-Stray current bias event analysis server. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] The following is an explanation of the proper nouns used in this invention: Absolute standard time signal: The absolute standard time synchronization signal is an internationally unified benchmark. It is the Coordinated Universal Time (UTC) legal time benchmark broadcast by China's BeiDou and other global satellite navigation systems (GNSS) and traced back to International Atomic Time (TAI). It consists of two parts: UTC absolute time digital messages and PPS second pulse hardware synchronization signals. It provides unambiguous, high-precision, and globally unified absolute time scale and hardware synchronization anchor points for any distributed node in the world. It is the core foundation for achieving cross-site microsecond / nanosecond level time synchronization.

[0022] UTC (Coordinated Universal Time) is the official global time standard and the absolute reference system for all time zone divisions.

[0023] PPS (Pulse Per Second) is a hardware synchronization pulse that occurs once per second and is strictly aligned with the whole second of UTC absolute time. It provides a nanosecond / submicrosecond time reference for high-precision time synchronization of distributed devices.

[0024] External interrupt channel: The full name is external hardware interrupt channel. It is a hardware-level interrupt triggering path built into the multi-dimensional synchronous acquisition and control module 6 in this invention. It can independently configure the triggering mode and response priority. It can directly receive the level transition signal output by the external hardware circuit, trigger the preset interrupt response program, and realize nanosecond-level hardware real-time response. It is a hardware unit that ensures the synchronous triggering accuracy and transient fault latching capability of this solution.

[0025] Interrupt Response: The full name is External Hardware Interrupt Response. In response to the hardware trigger signal received by the external interrupt channel, the hardware-level real-time response mechanism immediately suspends the currently executing ordinary software task and jumps to execute the preset priority interrupt service routine. It is the execution link that ensures the nanosecond-level real-time latching of synchronous actions and transient fault moments in this solution.

[0026] Example 1 refer to Figure 1 In this embodiment, a calibration system for monitoring stray current bias events adopts a distributed deployment architecture. Considering the characteristic of stray currents spreading along subway traction lines and affecting multiple substations along the line, an independent monitoring station is deployed at each target substation. Each monitoring station is distributed and operates independently. Each monitoring station includes a clamp-type current sensor 1, a piezoelectric accelerometer 2, a capacitive microphone 3, a DC current source 4, a Beidou clock module 5, a multi-dimensional synchronous acquisition and control module 6, and a communication module 7. Independent of the monitoring stations, there is also a stray current bias event analysis server 8. There is at least one stray current bias event analysis server 8; in this embodiment, there is one. The stray current bias event analysis server 8 communicates bidirectionally with the multi-dimensional synchronous acquisition and control module 6 at each monitoring station.

[0027] The multidimensional synchronous acquisition and control module 6 has a built-in clock and two external interrupt channels. The pins of the two external interrupt channels are electrically connected to the PPS second pulse output terminal of the Beidou clock module 5 and the threshold comparator output terminal of the clamp-type current sensor 1, respectively. The clamp-type current sensor 1 has a built-in threshold comparator.

[0028] The Beidou clock module 5 is used to receive the absolute standard time signal from the Beidou navigation satellite in real time. It is an industrial-grade Beidou timing module. The absolute standard time signal includes UTC absolute time information, and outputs the absolute standard time (UTC absolute time in this embodiment) and PPS second pulse according to the absolute standard time signal. The rising edge of the PPS second pulse is aligned with the zero point of the absolute standard time. In the technical solution of this invention, the clock module is a satellite timing module. The Beidou clock module 5 is one type of clock module in the technical solution of this invention. In addition to the Beidou clock module 5, GPS (Global Positioning System) clock modules (timed by GPS navigation satellites) and Galileo clock modules (timed by Galileo navigation satellites) can also be used, etc.

[0029] The multidimensional synchronous acquisition and control module 6 is used to determine whether the trigger time ready flag of the DC current source 4 can be set according to the current absolute standard time and the preset output absolute standard time of the DC current source 4. If the trigger time ready flag has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the interrupt response of the multidimensional synchronous acquisition and control module is triggered through an external interrupt channel, and the DC current source 4 is controlled to output DC current to the transformer neutral point grounding circuit in the power grid substation to simulate stray current bias event.

[0030] The clamp-type current sensor 1 is used to sample the current signal of the neutral point grounding circuit of the transformer in the power grid substation. When the voltage drop signal corresponding to the current signal is less than or equal to the voltage drop signal threshold corresponding to the stray current bias event, the threshold comparator outputs a second level. When the voltage drop signal corresponding to the current signal is greater than the voltage drop signal threshold corresponding to the stray current bias event, the threshold comparator outputs a first level. In this embodiment, the second level is a high level (e.g., 3.3V), and the first level is a low level (e.g., 0V). The clamp-type current sensor 1 has an openable clamping structure and is fixedly mounted on the straight section of the galvanized flat steel below the grounding lead of the main transformer core clamp in the power grid substation. At the same time, the clamp-type current sensor 1 collects the DC component of the grounding circuit of the core clamp, cross-verifies the authenticity of stray current bias events, filters false alarms, distinguishes between bias and multi-point grounding faults in the core, and quantifies the true magnetization degree inside the core. The clamp-type current sensor 1 is one type of current sensor in the technical solution of this invention. In addition to the clamp-type current sensor 1, the current sensor can also be a closed-loop zero-flux Hall current sensor, a fluxgate current sensor, etc.

[0031] The piezoelectric accelerometer 2 is powered by a constant current source and can convert radial acceleration vibration into a voltage difference signal, with a maximum distinguishable acceleration of ±80g. The piezoelectric accelerometer 2 is installed on the tank wall of the main transformer in the substation, directly in the radial direction of the internal core column. Simultaneously, the piezoelectric accelerometer 2 collects the radial vibration signal of the transformer core, quantifies the damage risk of bias magnetization to the equipment, classifies the severity of the event, verifies the core saturation degree, and detects latent damage to the equipment.

[0032] The condenser microphone 3 is powered by a constant current source and can convert sound signals with frequencies from 10Hz to 20kHz into voltage difference signals, achieving a dynamic range of sound intensity of 15~140dB. The condenser microphone 3 is installed approximately 0.3 meters outside the outline of the main transformer body in the substation, at a height of approximately 1.2~1.5 meters above the ground, directly facing the main radiating surface of the transformer tank, and must be unobstructed. Simultaneously, the condenser microphone 3 collects noise signals from the transformer body, matching them with on-site maintenance perception, verifying the authenticity of alarms in a closed-loop manner, and assisting in distinguishing magnetic bias from other equipment anomalies. The data meets national metrological standards.

[0033] The multidimensional synchronous acquisition and control module 6 is also used to trigger an interrupt response of the multidimensional synchronous acquisition and control module 6 through another external interrupt channel when the threshold comparator outputs a first level, and to latch the moment of the built-in clock when the threshold comparator outputs a first level. When the duration of the first level output by the threshold comparator exceeds a first preset duration (e.g., 3s), the latched moment is uploaded to the stray current bias event analysis server.

[0034] The communication module 7 is bidirectionally electrically connected to the multi-dimensional synchronous acquisition and control module 6 at the same monitoring station. Simultaneously, it establishes a bidirectional, low-latency, and highly reliable real-time communication channel with the globally unique stray current bias event analysis server 8 via an industrial-grade wired or wireless communication link. The communication module 7 serves as the sole data interaction bridge between the distributed front-end monitoring stations and the global analysis center.

[0035] The stray current bias event analysis server 8 is used to calculate the difference between the time latched by each monitoring station and the preset output absolute standard time of the DC current source 4, and to send a time calibration command to the multi-dimensional synchronous acquisition and control module 6 of each monitoring station according to the difference, so as to calibrate the built-in clock of the multi-dimensional synchronous acquisition and control module 6 of each monitoring station, so that the built-in clock of the multi-dimensional synchronous acquisition and control module 6 of each monitoring station is synchronized and aligned with the absolute standard time.

[0036] Each monitoring station possesses complete capabilities for on-site data acquisition, real-time processing, interrupt response, local storage, and synchronization control, eliminating the need for real-time intervention from the stray current and magnetic field event analysis server 8. This ensures the real-time performance and reliability of transient stray current and magnetic field event capture. A globally unique stray current and magnetic field event analysis and fault diagnosis server is established as the global control and analysis hub for the entire system. It establishes bidirectional communication links with all distributed monitoring stations, is responsible for distributing a globally unified calibration benchmark to all stations, receiving monitoring data uploaded by each station, completing cross-site data timing alignment, stray current propagation path tracing and fault diagnosis, and achieving closed-loop calibration of clock synchronization accuracy across all stations. Simultaneously, each distributed monitoring station achieves hardware-level synchronization with the absolute standard time through its own BeiDou clock module 5, ensuring complete time benchmark consistency across all distributed monitoring stations along the entire line and providing a high-precision global time anchor point for cross-site fault tracing.

[0037] Magnetism is a microsecond-level transient event. Time asynchrony can lead to severe misalignment of data timing. Within a single monitoring station, it is impossible to correlate current overruns, abnormal vibrations, and noise changes to the same moment, making it impossible to cross-verify the authenticity of stray current magnetism events, resulting in a soaring false alarm rate and an inability to quantify the true impact of magnetism. Among distributed multi-monitoring stations, it is impossible to determine the order of occurrence of stray current magnetism events in each substation, making it completely impossible to trace the propagation path of stray currents, directly rendering the core fault diagnosis capability of the entire system ineffective. This invention synchronizes the time of each monitoring station, anchoring the data from the clamp-type current sensor 1, piezoelectric accelerometer 2, and capacitive microphone 3 to the same UTC absolute time axis. This achieves precise timing alignment of electrical, vibration, and acoustic characteristics at the same moment, completely corresponding to the entire process of the occurrence and development of stray current magnetism events, enabling multi-dimensional feature cross-verification, and significantly reducing the false alarm rate. After synchronization among distributed multi-site stations, the timing sequence of stray current magnetism events in each substation can be accurately matched, enabling precise tracing of the stray current intrusion path and propagation direction.

[0038] The reason for latching the moment when the threshold comparator outputs the first level, instead of using an absolute standard time, is as follows: The monitored stray current bias event has the timing characteristics of random occurrence, transient triggering, and microsecond-level response latching. When the voltage drop signal corresponding to the current signal of the transformer neutral point grounding circuit is greater than the threshold signal of the voltage drop signal corresponding to the stray current bias event, the threshold comparator built into the clamp-type current sensor 1 will output a falling edge trigger signal corresponding to the first level. This trigger signal is an unpredictable random transient signal, and the triggering time can occur at any microsecond level within any absolute standard time period. To achieve timing comparison of stray current bias events and accurate tracing of stray current propagation paths among distributed multi-site locations, the multi-dimensional synchronous acquisition and control module 6 is required to complete nanosecond-level interrupt response and microsecond-level fault triggering time accurate latching at the moment of falling edge triggering, with the absolute error of the latching time not exceeding 1μs. The BeiDou clock module 5 used in this embodiment is an industrial-grade BeiDou timing module, which follows the globally accepted fixed timing output standard. Its timing characteristics are as follows: first, it outputs the rising edge of the PPS second pulse, which is strictly hardware aligned with the absolute standard time at the zero point of the second. After a fixed transmission delay, it outputs the absolute standard time digital message corresponding to the PPS pulse through the serial communication interface. In this embodiment, the absolute standard time is UTC absolute time. In specific implementation, for example, at the zero point of the absolute standard time 12:00:00.000000, the BeiDou clock module 5 outputs the rising edge of the PPS second pulse, which is strictly aligned with this time. After a minimum fixed delay of 500μs, it begins to send the absolute standard time digital message corresponding to 12:00:00. The total time for the complete transmission, parsing, and output of the valid absolute standard time of this message is 1ms~2ms, that is, the parsing of the valid absolute standard time can be completed as early as 12:00:00.002000. Based on the above two sets of timing characteristics, if the absolute standard time output by Beidou clock module 5 is directly used for fault trigger time latching, there will be unsolvable timing conflicts, which completely fails to meet the microsecond-level latching accuracy requirements of this embodiment. More than 99.99% of stray current bias events are triggered at random microsecond-level times that are not whole seconds. For example, if the trigger time is the absolute standard time 12:00:00.123456, that is, 123.456ms after the zero point of the second, the next output of the digital message corresponding to the absolute standard time by Beidou clock module 5 will have to wait until the PPS pulse output of the next absolute standard time, 12:00:01.000000, which means it will take another 876.544ms to complete the parsing of the new absolute standard time.At the moment of fault triggering, the multi-dimensional synchronous acquisition and control module 6 can only acquire the old absolute standard time data 12:00:00, which was parsed in the previous full second. It cannot acquire the precise microsecond-level absolute standard timestamp corresponding to the fault triggering time, which completely fails to meet the microsecond-level time latching requirements of this embodiment. Consequently, the fault timing comparison and stray current propagation path tracing functions among distributed multi-site sites completely fail. To resolve the above timing contradiction, this embodiment uses a built-in clock that has been hardware-calibrated to the absolute standard time as the latching reference for the fault triggering time. This built-in clock is a high-precision time counter that is built into the multi-dimensional synchronous acquisition and control module 6 and runs locally continuously. Each microsecond-level count value can be read in real time without delay and is not limited by the transmission delay of serial communication. At the same time, this built-in clock completes hardware-level calibration with the absolute standard time every second through the PPS second pulse output by the Beidou clock module 5. Its synchronization error with the absolute standard time is no more than 1μs. At the instant a fault interruption is triggered, the multi-dimensional synchronous acquisition and control module 6 can read the current count value of the built-in clock without delay through the highest priority interrupt service routine, and complete the microsecond-level precise latch at the moment of fault triggering. This not only meets the nanosecond-level response requirements of transient faults, but also ensures the global synchronization between the latch time and the absolute standard time, perfectly solving the above-mentioned timing contradiction. It provides an accurate and reliable time reference for fault timing comparison and stray current propagation path tracing in distributed multi-site systems, and also provides an accurate calculation basis for the subsequent stray current bias event analysis server 8 to complete the full-site clock calibration.

[0039] In addition, the interrupt response with dual-path independent priority configuration solves the latency problem, ensuring the global consistency of synchronous simulation of bias events at all distributed sites along the line, and realizing nanosecond-level response and microsecond-level time latching of random transient bias events. This provides real-time assurance for closed-loop calibration of synchronization accuracy across all sites, timing comparison of cross-site bias events, and tracing of stray current propagation paths.

[0040] In one specific implementation, the stray current bias event analysis server 8 is also used to configure the preset absolute standard time of the DC current source 4 and send it to the multi-dimensional synchronous acquisition and control module 6. The preset absolute standard time of the DC current source 4 is delayed by more than 1 minute compared to the absolute standard time of the sending operation. In this embodiment, the monitoring stations are distributed along the line, covering an area of ​​tens of kilometers. The communication links between different monitoring stations and the stray current bias event analysis server 8 may experience transmission delays, fluctuations, or even occasional packet loss. The more than 1 minute of reserved time avoids the problem of synchronization trigger failure and full-site calibration failure caused by the multi-dimensional synchronous acquisition and control module 6 of some monitoring stations not receiving instructions in time due to communication delays, thus ensuring the consistency of global synchronous triggering of the distributed system.

[0041] As a specific implementation method, in the multi-dimensional synchronous acquisition and control module 6, the specific method for determining whether the trigger time ready flag of the DC current source 4 can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source 4 is as follows: the trigger time ready flag is set only when the current absolute standard time is consistent with the time corresponding to the preset output absolute standard time of the DC current source by a third preset time (e.g., 1 second). At other times, the setting operation is not performed. The synchronous triggering condition of this technical solution is "the trigger time ready flag is set" plus "detecting the rising edge of the PPS second pulse corresponding to the preset output absolute standard time of the DC current source 4". The rising edge of the PPS second pulse is a nanosecond-level transient signal. If the software operation of time comparison and flag setting is performed only when the rising edge arrives, it will inevitably introduce a software processing delay of several microseconds, resulting in a delayed triggering action and destroying the microsecond-level synchronization accuracy of the entire site. The trigger timing ready flag is set 1 second in advance. This allows the trigger timing ready flag to be set before the preset absolute standard time of the DC current source 4 arrives, enabling the multi-dimensional synchronous acquisition and control module 6 to enter the hardware-level ready-to-trigger state. Once the rising edge of the corresponding PPS second pulse is detected, an interrupt response can be triggered immediately through the external interrupt channel, executing the output action of the DC current source 4 with zero software delay. This ensures that the synchronization error between the trigger action of the entire site and the preset absolute standard time is stably controlled within 1μs.

[0042] As a specific implementation, the multi-dimensional synchronous acquisition and control module 6 is also used to reset the trigger time ready flag and shut down the DC current source when completing the operation of controlling the DC current source to output DC current to the neutral point grounding circuit of the transformer in the power grid substation, so as to avoid the negative impact caused by outputting DC current to the neutral point grounding circuit of the transformer in the power grid substation for a long time.

[0043] In this embodiment, a globally unique stray current bias event analysis server 8 sends a unified preset absolute standard time from the DC current source 4 to all monitoring stations along the entire line. The multi-dimensional synchronous acquisition and control module 6, after comparing the current absolute standard time with the preset output time, sets a trigger time ready flag in advance. At the preset output absolute standard time, it responds to the rising edge of the PPS second pulse output by the Beidou clock module 5, which is strictly aligned with the zero point of the absolute standard time, through the first external interrupt channel. This synchronously triggers the DC current source 4 to output DC current to the transformer neutral point grounding circuit to simulate a stray current bias event. Simultaneously, the current signal is detected by the built-in threshold comparator of the clamp-type current sensor 1. When the corresponding voltage drop signal exceeds the limit, it outputs a first level, triggering the second external interrupt channel to latch the corresponding time of the clock built into the multi-dimensional synchronous acquisition and control module 6. Finally, the stray current bias event analysis server 8 compares the difference between the latched time of each station and the preset output absolute standard time, and issues a calibration command to complete the closed-loop calibration of the clock built into the multi-dimensional synchronous acquisition and control module at all stations. This technical solution overcomes the limitations of existing technologies, which can only achieve single-point time synchronization and cannot verify the synchronization accuracy across all sites. It achieves basic synchronization of the clock source, ensuring that the synchronization error across all sites is stably controlled within 1μs. At the same time, it ensures that the built-in clocks of the multi-dimensional synchronous acquisition and control modules of all monitoring sites are synchronized and strictly aligned with the absolute standard time. This provides a unified, reliable, and high-precision time reference for the time sequence comparison of stray current bias events across monitoring sites and the tracing of stray current propagation paths. It solves the problems of distortion in event correlation analysis and insufficient tracing accuracy caused by synchronization deviations in existing technologies.

[0044] In this embodiment, the multi-dimensional synchronous acquisition and control module 6 has two built-in independent external interrupt channels. The second external interrupt channel is directly electrically connected to the output of the threshold comparator built into the clamp-type current sensor 1. The falling edge of the first level output by the threshold comparator can directly trigger the highest priority interrupt response. Simultaneously, a built-in clock calibrated at the absolute standard time hardware level is used as the latching reference. This built-in clock is a locally continuously running high-precision time counter, which can read the current accurate count value without delay at the moment of interrupt triggering, resolving the timing contradiction between the absolute standard time message transmission delay of the Beidou clock module 5 and the random triggering of transient events. A misjudgment prevention mechanism with a first preset duration is synchronously set, and the latching time is uploaded only when the duration of the first level exceeds the first preset duration.

[0045] In this embodiment, each monitoring station is synchronously equipped with three types of sensors: a clamp-on current sensor 1, a piezoelectric accelerometer 2, and a capacitive microphone 3. All sensor data is collected by a multi-dimensional synchronous acquisition and control module 6, with a microsecond-level timestamp applied using a calibrated built-in clock as a unified reference. After the built-in clocks at all stations are calibrated, all multi-dimensional data are anchored on the same absolute standard time axis, achieving precise correspondence between electrical, vibration, and acoustic characteristics at the same moment. This solves the shortcomings of existing technologies where discrete systems cannot align data in time, achieving precise timing matching of current, vibration, and noise data, and fully corresponding to the entire process of stray current bias events. Through cross-validation of the features of the three types of sensors, stray current bias can be accurately distinguished from other equipment anomalies such as multi-point grounding of the iron core, loose mechanical structure, and cooling system failure, significantly reducing the misjudgment rate of stray current bias events and solving the problem that existing technologies cannot distinguish between bias and vibration / noise differences caused by other faults.

[0046] This embodiment configures a unified preset absolute standard time for stray current bias event analysis server 8, controlling the DC current sources 4 of all monitoring stations along the entire line to synchronously output DC current at the same absolute standard time. This simulates a standard stray current bias event, fully reproducing the entire process characteristics of the stray current bias event and actively verifying the system's stray current bias event capture capability, synchronization accuracy, and fault diagnosis accuracy. This overcomes the limitations of existing technologies, which can only passively monitor random stray current bias events and cannot actively verify system performance.

[0047] Example 2 A data acquisition system based on the calibration system for monitoring stray current bias events in Embodiment 1 is provided. At each monitoring station, the multidimensional synchronous acquisition and control module 6 continuously acquires raw multidimensional data via a multidimensional sensor at a preset sampling frequency when the threshold comparator outputs a second level. Using a first acquisition time window as the rolling period, at the end of each rolling first acquisition time window, the system calculates the feature value set of the raw multidimensional data acquired within that first acquisition time window and sends the feature value set to the stray current bias event analysis server 8. The multidimensional synchronous acquisition and control module 6 also continuously stores raw multidimensional data within a continuous time interval, ending at the current time of the built-in clock and lasting for a second acquisition time window. When the threshold comparator outputs a first level, raw multidimensional data is acquired via a multidimensional sensor at a preset sampling frequency within a third acquisition time window. At the end of the third acquisition time window, the continuously stored raw multidimensional data and the raw multidimensional data acquired within the third acquisition time window are merged sequentially to obtain merged raw multidimensional data, which is then sent to the stray current bias event analysis server 8.

[0048] Among them, the first acquisition time window is shorter than the second acquisition time window, the first acquisition time window is shorter than the third acquisition time window, and the second acquisition time window is equal to or not equal to the third acquisition time window.

[0049] In this embodiment, the first acquisition time window is 1 second, and the second and third acquisition time windows are both 5 seconds, with a preset sampling frequency of 100 kHz. The multidimensional synchronous acquisition and control module 6 has an internal controller that provides 16 million bytes of memory for high-speed data storage of seconds before and after stray current bias events. After 10 seconds of merged original multidimensional data are prepared, the multidimensional synchronous acquisition and control module 6 uploads 16 million bytes of waveform data sequentially according to the communication protocol, reference signal type, and channel number. The original multidimensional data is waveform data. The feature set of the original multidimensional data includes, but is not limited to, electrical dimension feature values, vibration dimension feature values, and acoustic dimension feature values. Electrical dimension feature values ​​include, but are not limited to, the average value of the DC component of the current, the total harmonic distortion (THD) of the current, the effective value of the characteristic harmonic components, the peak value of the current, and the time-domain standard deviation of the current. Vibration dimension feature values ​​include, but are not limited to, the total effective value of radial vibration acceleration (RMS), the peak value of vibration, the centroid of the vibration spectrum, and the vibration baseline drift. Acoustic dimension feature values ​​include, but are not limited to, the total effective value of the sound pressure level (dB), the sound pressure level components of the characteristic frequency band, the noise peak factor, and the sound pressure level baseline increment.

[0050] The multidimensional synchronous acquisition and control module 6 first responds to the time calibration command. After the built-in clocks of the multidimensional synchronous acquisition and control module 6 at each monitoring station are synchronized and aligned with the absolute standard time, it then acquires the raw multidimensional data of the power grid substation status.

[0051] As a specific implementation, the multi-dimensional synchronous acquisition and control module 6 integrates a sample-and-hold amplifier, which is used for multi-channel synchronous acquisition of monitoring data, with a sampling time deviation between channels of less than 25ns.

[0052] As one specific implementation, the clamp-type current sensor 1 integrates a programmable amplifier circuit, which can dynamically amplify the voltage drop signal generated by the current in the grounding circuit by 1x, 10x, 100x or 1000x.

[0053] The multi-dimensional synchronous acquisition and control module 6 integrates a sample-and-hold amplifier, enabling multi-channel synchronous acquisition of monitoring data with a sampling time deviation of less than 25ns between channels, further ensuring the timing synchronization accuracy of multi-dimensional data. The clamp-type current sensor 1 integrates a programmable amplifier circuit, capable of dynamically amplifying the voltage drop signal generated by the grounding loop current by 1x, 10x, 100x, or 1000x, accurately capturing the full range of bias current signals from weak to large values, avoiding small-signal distortion and large-signal saturation. Through the above technical solutions, nanosecond-level interrupt response and microsecond-level latching for stray current bias events are achieved, accurately capturing transient bias current mutations at the 10ms or even microsecond level, fully restoring key characteristics such as current peak value and harmonic distortion at the moment of fault. This solves the problems of large recording intervals and transient waveform distortion in existing technologies. Simultaneously, the anti-false-judgment mechanism effectively filters out false triggers caused by transient electromagnetic interference, significantly improving the reliability and accuracy of stray current bias event capture.

[0054] In this embodiment, all collected and cached raw multidimensional data are based on the built-in clock calibrated with the global absolute standard time in Embodiment 1, and are stamped with microsecond-level timestamps. The merged raw multidimensional data strictly follows the absolute standard time axis sorting. This ensures that the synchronization error between the collected data from all distributed monitoring stations along the entire line and the global absolute standard time is stably controlled within 1μs, completely eliminating the timing misalignment between distributed monitoring stations. Based on the merged raw multidimensional data synchronized and aligned by each monitoring station, the occurrence timing and waveform characteristics of stray current bias events in different substations are compared to accurately reconstruct the intrusion direction and propagation path of stray currents, achieving precise source tracing of the causes of stray current bias events.

[0055] This embodiment addresses the need for high-frequency sampling of stray current bias events at 100kHz and above by designing a hierarchical transmission mechanism: when the threshold comparator outputs the second level, raw multidimensional data is continuously acquired at a sampling frequency of 100kHz. Only at the end of the first acquisition time window of each rolling cycle is a small set of feature values ​​uploaded, rather than the full amount of raw data, thus achieving high-frequency updates of feature values. This preserves the ability of high-frequency sampling to fully capture transient current changes and oscillation decay processes, avoiding the omission of key waveform details due to low sampling rates, while significantly reducing the communication bandwidth occupancy ratio under normal operation. This greatly alleviates the bandwidth pressure of distributed multi-site long-distance communication and solves the system resource overload problem caused by high-frequency sampling and continuous waveform recording in existing technologies.

[0056] In this embodiment, under normal conditions, the original multidimensional data is continuously and continuously stored, with the current time of the built-in clock as the endpoint and the duration as the second acquisition time window. When a stray current bias event that causes the threshold comparator to output the first level is triggered, the data after the stray current bias event within the third acquisition time window is continuously acquired. Finally, the cached data before the stray current bias event and the acquired data after the event are merged in time sequence to form complete original multidimensional data of the stray current bias event, which is then uploaded to the stray current bias event analysis server 8. This solves the shortcomings of existing waveform recording devices, which can only record the waveform after triggering and lose the pre-process of the bias event from its inception and development to the over-limit triggering. It completely restores the waveform of the entire life cycle of the stray current bias event and retains key features such as the current peak value, harmonic distortion, and vibration noise linkage changes at the moment of the fault.

[0057] Example 3 A calibration method for monitoring stray current bias events includes the following steps: The multidimensional synchronous acquisition and control module 6 has a built-in clock and two external interrupt channels. The pins of the two external interrupt channels are electrically connected to the PPS second pulse output terminal of the Beidou clock module 5 and the threshold comparator output terminal of the clamp-type current sensor 1, respectively. The clamp-type current sensor 1 has a built-in threshold comparator.

[0058] The Beidou clock module 5 receives the absolute standard time signal from the Beidou satellite in real time. It is an industrial-grade Beidou time synchronization module. The absolute standard time signal contains UTC absolute time information and outputs the absolute standard time (UTC absolute time in this embodiment) and PPS second pulse according to the absolute standard time signal. The rising edge of the PPS second pulse is aligned with the zero point of the absolute standard time.

[0059] The multidimensional synchronous acquisition and control module 6 determines whether the trigger time ready flag of the DC current source 4 can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source 4. If the trigger time ready flag has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the interrupt response of the multidimensional synchronous acquisition and control module is triggered through an external interrupt channel, and the DC current source 4 is controlled to output DC current to the neutral point grounding circuit of the transformer in the power grid substation to simulate stray current bias event.

[0060] The clamp-type current sensor 1 samples the current signal of the neutral point grounding circuit of the transformer in the power grid substation. When the voltage drop signal corresponding to the current signal is less than or equal to the threshold voltage drop signal corresponding to the stray current bias event, the threshold comparator outputs a second level. When the voltage drop signal corresponding to the current signal is greater than the threshold voltage drop signal corresponding to the stray current bias event, the threshold comparator outputs a first level. In this embodiment, the second level is a high level (e.g., 3.3V), and the first level is a low level (e.g., 0V). The clamp-type current sensor 1 has an opening and closing clamping structure and is fixedly mounted on the straight section of the galvanized flat steel below the grounding lead of the main transformer core clamp in the power grid substation. At the same time, the clamp-type current sensor 1 collects the DC component of the grounding circuit of the core clamp, cross-verifies the authenticity of stray current bias events, filters false alarms, distinguishes between bias and multi-point grounding faults in the core, and quantifies the true magnetization degree inside the core.

[0061] The piezoelectric accelerometer 2 is powered by a constant current source and can convert radial acceleration vibration into a voltage difference signal, with a maximum distinguishable acceleration of ±80g. The piezoelectric accelerometer 2 is installed on the tank wall of the main transformer in the substation, directly in the radial direction of the internal core column. Simultaneously, the piezoelectric accelerometer 2 collects the radial vibration signal of the transformer core, quantifies the damage risk of bias magnetization to the equipment, classifies the severity of the event, verifies the core saturation degree, and detects latent damage to the equipment.

[0062] The condenser microphone 3 is powered by a constant current source and can convert sound signals with frequencies from 10Hz to 20kHz into voltage difference signals, achieving a dynamic range of sound intensity of 15~140dB. The condenser microphone 3 is installed approximately 0.3 meters outside the outline of the main transformer body in the substation, at a height of approximately 1.2~1.5 meters above the ground, directly facing the main radiating surface of the transformer tank, and must be unobstructed. Simultaneously, the condenser microphone 3 collects noise signals from the transformer body, matching them with on-site maintenance perception, verifying the authenticity of alarms in a closed-loop manner, and assisting in distinguishing magnetic bias from other equipment anomalies. The data meets national metrological standards.

[0063] When the threshold comparator outputs a first level, the multidimensional synchronous acquisition and control module 6 also triggers an interrupt response through another external interrupt channel, and latches the moment when the threshold comparator outputs a first level. When the duration of the first level output by the threshold comparator exceeds a first preset duration (e.g., 3s), the latched moment is uploaded to the stray current bias event analysis server.

[0064] The communication module 7 is bidirectionally electrically connected to the multi-dimensional synchronous acquisition and control module 6 at the same monitoring station. Simultaneously, it establishes a bidirectional, low-latency, and highly reliable real-time communication channel with the globally unique stray current bias event analysis server 8 via an industrial-grade wired or wireless communication link. The communication module 7 serves as the sole data interaction bridge between the distributed front-end monitoring stations and the global analysis center.

[0065] The stray current bias event analysis server 8 calculates the difference between the time latched by each monitoring station and the preset output absolute standard time of the DC current source 4, and sends a time calibration command to the multi-dimensional synchronous acquisition and control module 6 of each monitoring station according to the difference, so as to calibrate the built-in clock of the multi-dimensional synchronous acquisition and control module 6 of each monitoring station, so that the built-in clock of the multi-dimensional synchronous acquisition and control module 6 of each monitoring station is synchronized and aligned with the absolute standard time.

[0066] Example 4 A data acquisition method based on the calibration method for monitoring stray current bias events in Embodiment 3 is provided. At each monitoring station, the multidimensional synchronous acquisition and control module 6 continuously acquires raw multidimensional data via a multidimensional sensor at a preset sampling frequency when the threshold comparator outputs a second level. A first acquisition time window serves as the rolling cycle. At the end of each rolling first acquisition time window, the feature value set of the raw multidimensional data acquired within that first acquisition time window is calculated and sent to the stray current bias event analysis server 8. The multidimensional synchronous acquisition and control module 6 also continuously stores raw multidimensional data within a continuous time interval, ending at the current time of the built-in clock and lasting for a second acquisition time window. When the threshold comparator outputs a first level, raw multidimensional data is acquired via a multidimensional sensor at a preset sampling frequency within a third acquisition time window. At the end of the third acquisition time window, the rolling-stored raw multidimensional data and the raw multidimensional data acquired within the third acquisition time window are merged sequentially to obtain merged raw multidimensional data, which is then sent to the stray current bias event analysis server 8.

[0067] Among them, the first acquisition time window is shorter than the second acquisition time window, the first acquisition time window is shorter than the third acquisition time window, and the second acquisition time window is equal to or not equal to the third acquisition time window.

[0068] The contents not described in detail in this specification are prior art known to those skilled in the art. Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0069] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0070] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0071] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A calibration system for monitoring stray current bias events, characterized in that, include: The clock module is used to receive external absolute standard time signals in real time and output absolute standard time and PPS second pulses according to the absolute standard time signals. The multi-dimensional synchronous acquisition and control module is used to determine whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source. Under the premise that the trigger time ready flag of the DC current source has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the DC current source is controlled to output DC current to the neutral point grounding circuit of the transformer in the corresponding power grid substation to simulate stray current bias event. The current sensor is used to sample the current signal of the transformer neutral point grounding circuit in the current power grid substation. When the voltage drop signal corresponding to the current signal is greater than the threshold of the voltage drop signal corresponding to the stray current bias event, it outputs the first level. The multi-dimensional synchronous acquisition and control module is also used to latch the time of the built-in clock of the multi-dimensional synchronous acquisition and control module when the first level is detected, and to upload the latched time to the stray current bias event analysis server when the duration of the first level exceeds the first preset duration. The stray current bias event analysis server is used to calculate the difference between the time latched by the multi-dimensional synchronous acquisition and control module in each power grid substation and the preset output absolute standard time of the DC current source. Based on the difference, it sends a time calibration command to the multi-dimensional synchronous acquisition and control module of each power grid substation so that the built-in clock of the multi-dimensional synchronous acquisition and control module of each power grid substation is synchronized and aligned with the absolute standard time.

2. The calibration system for monitoring stray current bias events according to claim 1, characterized in that, The stray current bias event analysis server is also used to configure the preset output absolute standard time of the DC current source and send it to the multi-dimensional synchronous acquisition and control module. The preset output absolute standard time of the DC current source is delayed by a second preset time compared with the absolute standard time of the sending operation.

3. The calibration system for monitoring stray current bias events according to claim 1, characterized in that, In the multi-dimensional synchronous acquisition and control module, the specific method for determining whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source is as follows: The trigger time ready flag is set only when the current absolute standard time coincides with the time corresponding to the third preset time before the preset output absolute standard time of the DC current source. At other times, the setting operation is not performed.

4. The calibration system for monitoring stray current bias events according to claim 1, characterized in that, The multidimensional synchronous acquisition and control module is also used to trigger an interrupt response of the multidimensional synchronous acquisition and control module when the rising edge of the corresponding PPS second pulse is detected at the preset absolute standard time of the DC current source output, and when the duration of the first level exceeds the first preset duration.

5. A data acquisition system based on the calibration system for monitoring stray current bias events according to any one of claims 1 to 4, characterized in that, The current sensor is used to output a second level when the voltage drop signal corresponding to the current signal of the current substation in the current power grid is less than or equal to the voltage drop signal threshold corresponding to the stray current bias event; The multidimensional synchronous acquisition and control module is used to continuously acquire raw multidimensional data of the power grid substation status through multidimensional sensors at a preset sampling frequency when the second level is detected. The first acquisition time window is used as the rolling period. At the end of each rolling first acquisition time window, the feature value set of the raw multidimensional data acquired in the first acquisition time window is calculated and sent to the stray current bias event analysis server. The raw multidimensional data within the continuous time interval with the current time of the built-in clock as the end point and the second acquisition time window as the duration is stored in the multidimensional synchronous acquisition and control module. When the first level is detected, the original multidimensional data of the power grid substation status is collected by the multidimensional sensor at a preset sampling frequency within the third acquisition time window. At the end of the third acquisition time window, the original multidimensional data stored in the rolling storage and the original multidimensional data collected within the third acquisition time window are merged in time sequence to obtain the merged original multidimensional data, and the merged original multidimensional data is sent to the stray current bias event analysis server.

6. The data acquisition system according to claim 5, characterized in that, The multi-dimensional synchronous acquisition and control module integrates a sample-and-hold amplifier, which is used for multi-channel synchronous acquisition of monitoring data, with the sampling time deviation between channels being less than a preset time deviation.

7. The data acquisition system according to claim 5, characterized in that, The current sensor integrates a programmable amplifier circuit, which can amplify the voltage drop signal generated by the current in the grounding circuit.

8. The data acquisition system according to claim 5, characterized in that, The multidimensional synchronous acquisition and control module first responds to the time calibration command. After the built-in clocks of the multidimensional synchronous acquisition and control modules in each power grid substation are synchronized and aligned with the absolute standard time, it then acquires the original multidimensional data of the power grid substation status.

9. A calibration method for monitoring stray current bias events, characterized in that, Includes the following steps: The clock module receives external absolute standard time signals in real time and outputs absolute standard time and PPS second pulses based on the absolute standard time signals. The multi-dimensional synchronous acquisition and control module determines whether the trigger time ready flag of the DC current source can be set based on the current absolute standard time and the preset output absolute standard time of the DC current source. If the trigger time ready flag of the DC current source has been set, when the rising edge of the corresponding PPS second pulse is detected at the preset output absolute standard time of the DC current source, the module controls the DC current source to output DC current to the neutral point grounding circuit of the transformer in the corresponding power grid substation to simulate stray current bias event. The current sensor samples the current signal of the transformer neutral point grounding circuit in the current power grid substation. When the voltage drop signal corresponding to the current signal is greater than the threshold of the voltage drop signal corresponding to the stray current bias event, the first level is output. When the multi-dimensional synchronous acquisition and control module detects the first level, it latches the time of the clock built into the multi-dimensional synchronous acquisition and control module when the first level is detected. When the duration of the first level exceeds the first preset duration, it uploads the latched time to the stray current bias event analysis server. The stray current bias event analysis server calculates the difference between the time latched by the multi-dimensional synchronous acquisition and control module in each power grid substation and the preset output absolute standard time of the DC current source. Based on the difference, it sends a time calibration command to the multi-dimensional synchronous acquisition and control module of each power grid substation to synchronize the built-in clock of the multi-dimensional synchronous acquisition and control module of each power grid substation and align it with the absolute standard time.

10. A data acquisition method based on the calibration method for monitoring stray current bias events as described in claim 9, characterized in that, Includes the following steps: The current sensor outputs a second level when the voltage drop signal corresponding to the current signal of the current substation in the current power grid is less than or equal to the voltage drop signal threshold corresponding to the stray current bias event; When the second level is detected, the multidimensional synchronous acquisition and control module continuously acquires raw multidimensional data of the power grid substation status through multidimensional sensors at a preset sampling frequency. The first acquisition time window is used as the rolling period. At the end of each rolling first acquisition time window, the feature value set of the raw multidimensional data acquired in the first acquisition time window is calculated and sent to the stray current bias event analysis server. The raw multidimensional data within the continuous time interval with the current time of the built-in clock as the end point and the second acquisition time window as the duration is stored in the multidimensional synchronous acquisition and control module. When the first level is detected, the original multidimensional data of the power grid substation status is collected by the multidimensional sensor at a preset sampling frequency within the third acquisition time window. At the end of the third acquisition time window, the original multidimensional data stored in the rolling storage and the original multidimensional data collected within the third acquisition time window are merged in time sequence to obtain the merged original multidimensional data, and the merged original multidimensional data is sent to the stray current bias event analysis server.

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