Safety detection method and device for polarity selector of on-load tap-changer

Abstract

The invention discloses a safety detection method and device for a polarity selector of an on-load tap-changer, and relates to the technical field of safety detection methods. According to the resistance change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap-changer, the conduction state of the zinc oxide nonlinear resistor is determined, and the detection accuracy of the conduction state of the zinc oxide nonlinear resistor is improved. Therefore, the safety detection area of the polarity selector of the on-load tap-changer is determined according to the conduction state of the zinc oxide nonlinear resistor, the plurality of working data of the polarity selector and the corresponding real-time image; the risk event is determined based on the detection of the safety detection area, and the safety level of the polarity selector of the on-load tap-changer is determined based on the risk event, the working state of the on-load tap-changer and the conduction state of the zinc oxide nonlinear resistor, so that the accuracy of the safety level of the polarity selector of the on-load tap-changer is improved.

Description

Technical Field

[0001] This invention relates to the technical field of safety detection methods, and more particularly to a safety detection method and apparatus for a polarity selector of an on-load tap changer. Background Technology

[0002] With the development of technology, the polarity selector (or diverter) of an on-load tap changer is a crucial component inside the switch. Its core function is to change the connection direction between the voltage regulating winding (or tap winding) and the main winding, thereby achieving "positive" and "negative" switching of the voltage regulation range. The polarity selector is usually located at the bottom of the on-load tap changer. In existing technology, multiple operating data points of the on-load tap changer are collected, and the corresponding switching state is identified based on these data points. A corresponding resistor is then matched based on this switching state. However, the influence of resistance changes in the zinc oxide nonlinear resistor is ignored, affecting the accuracy of detecting the conduction state of the zinc oxide nonlinear resistor. This results in lower accuracy of the safety level of the polarity selector in the on-load tap changer. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a safety detection method and device for the polarity selector of an on-load tap changer.

[0004] This invention provides a safety detection method for the polarity selector of an on-load tap changer, comprising: Collect multiple operating data of the on-load tap changer, determine the corresponding switching state based on the identification of the multiple operating data of the on-load tap changer, and determine the maximum offset voltage based on the switching state and the multiple voltage data corresponding to the polarity selector of the on-load tap changer. Based on the maximum offset voltage and the corresponding zinc oxide nonlinear resistor matched to the on-load tap changer, the zinc oxide nonlinear resistor is connected to the contact terminal of the polarity selector of the on-load tap changer. Collect multiple resistance data of the zinc oxide nonlinear resistor, determine the resistance change event of the zinc oxide nonlinear resistor based on the multiple resistance data, and determine the conduction state of the zinc oxide nonlinear resistor according to the resistance change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap changer. The safe detection area of ​​the polarity selector of the on-load tap changer is determined based on the conduction state of the zinc oxide nonlinear resistor, multiple operating data of the polarity selector, and the corresponding real-time image. Risk events are identified based on the detection of this safety detection area. The safety level of the polarity selector of the on-load tap changer is determined based on the risk event, the operating state of the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor.

[0005] This invention provides a safety detection device for the polarity selector of an on-load tap changer. The safety detection device for the polarity selector of the on-load tap changer is applied to the aforementioned safety detection method for the polarity selector of the on-load tap changer. The safety detection device for the polarity selector of the on-load tap changer includes: The offset voltage module is used to collect multiple operating data of the on-load tap changer, determine the corresponding switching state based on the identification of the multiple operating data of the on-load tap changer, and determine the maximum offset voltage based on the switching state and the multiple voltage data corresponding to the polarity selector of the on-load tap changer. The resistor matching module is used to match the corresponding zinc oxide nonlinear resistor based on the maximum offset voltage and the on-load tap changer, and connect the zinc oxide nonlinear resistor to the contact terminal of the polarity selector of the on-load tap changer. The resistance status module is used to collect multiple resistance data of the zinc oxide nonlinear resistor, determine the resistance change event of the zinc oxide nonlinear resistor based on the multiple resistance data, and determine the conduction state of the zinc oxide nonlinear resistor according to the resistance change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap changer. The safety detection area module is used to determine the safety detection area of ​​the polarity selector of the on-load tap changer based on the conduction state of the zinc oxide nonlinear resistor, multiple working data of the polarity selector, and the corresponding real-time image. The safety level module is used to determine risk events based on the detection in the safety detection area, and to determine the safety level of the polarity selector of the on-load tap changer based on the risk event, the operating state of the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor.

[0006] Compared with the prior art, the beneficial effects of the present invention are: In this embodiment of the invention, the method involves collecting multiple operating data from an on-load tap changer, determining the corresponding switching state based on the identification of these data, determining the maximum offset voltage based on the switching state and multiple voltage data corresponding to the polarity selector of the on-load tap changer, matching the on-load tap changer with a zinc oxide nonlinear resistor, and connecting the zinc oxide nonlinear resistor to the contact terminal of the polarity selector of the on-load tap changer, collecting multiple resistance data from the zinc oxide nonlinear resistor, determining resistance change events based on these data, and determining the conduction state of the zinc oxide nonlinear resistor based on the resistance change events, the corresponding connection position, and the circuit diagram corresponding to the on-load tap changer. The introduction of a maximum offset voltage allows for the control of the zinc oxide nonlinear resistor, incorporating a holistic consideration of resistance change events, corresponding connection positions, and the circuit diagram corresponding to the on-load tap changer, thereby improving the accuracy of detecting the conduction state of the zinc oxide nonlinear resistor.

[0007] Therefore, based on the conduction state of the zinc oxide nonlinear resistor, multiple operating data of the polarity selector, and the corresponding real-time image, the safety detection area of ​​the polarity selector of the on-load tap changer is determined. Risk events are identified based on the detection within this safety detection area. The safety level of the polarity selector is then determined based on the risk event, the operating state of the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor. This introduces a safety detection area for the polarity selector, further controlling this area and achieving a holistic consideration of the risk event, the operating state of the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor, thus improving the accuracy of the safety level of the polarity selector of the on-load tap changer. Attached Figure Description

[0008] Figure 1 This is a flowchart illustrating the safety detection method for the polarity selector of an on-load tap changer in an embodiment of the present invention. Figure 2 This is a flowchart illustrating step S11 in the safety detection method for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 3 This is a flowchart illustrating step S12 in the safety detection method for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 4 This is a flowchart illustrating step S13 in the safety detection method for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 5 This is a flowchart illustrating step S14 in the safety detection method for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 6 This is a flowchart illustrating step S15 in the safety detection method for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 7 This is a schematic diagram of the structural composition of the safety detection device for the polarity selector of the on-load tap changer in an embodiment of the present invention. Figure 8 This is a schematic diagram of the polarity selector of the on-load tap changer in an embodiment of the present invention. Detailed Implementation

[0009] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0010] Please see Figures 1 to 8 A safety detection method for the polarity selector of an on-load tap changer, applied to safety detection scenarios; the safety detection method for the polarity selector of an on-load tap changer includes: Step S11: Collect multiple operating data of the on-load tap changer, determine the corresponding switching state based on the identification of the multiple operating data of the on-load tap changer, and determine the maximum offset voltage based on the switching state and the multiple voltage data corresponding to the polarity selector of the on-load tap changer. Step S12: Based on the maximum offset voltage and the corresponding zinc oxide nonlinear resistor matched to the on-load tap changer, connect the zinc oxide nonlinear resistor to the contact terminal of the polarity selector of the on-load tap changer; Step S13: Collect multiple resistance data of the zinc oxide nonlinear resistor, determine the resistance change event of the zinc oxide nonlinear resistor based on the multiple resistance data, and determine the conduction state of the zinc oxide nonlinear resistor according to the resistance change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap changer. Step S14: Determine the safe detection area of ​​the polarity selector of the on-load tap changer based on the conduction state of the zinc oxide nonlinear resistor, multiple working data of the polarity selector, and the corresponding real-time image. Step S15: Based on the detection of the safety detection area, determine the risk event, and based on the risk event, the operating state of the on-load tap changer and the conduction state of the zinc oxide nonlinear resistor, determine the safety level of the polarity selector of the on-load tap changer.

[0011] refer to Figure 2 In step S11, the specific steps are as follows: S111: Real-time monitoring of on-load tap changers, collection of multiple working data of on-load tap changers based on monitoring of on-load tap changers, determination of multiple working combinations based on multiple working data of on-load tap changers and corresponding working modes, and determination of corresponding switching states based on multiple working combinations and the current working content of on-load tap changers. S112: Mark the polarity selector of the on-load tap changer and collect multiple voltage data corresponding to the polarity selector of the on-load tap changer. Based on the multiple voltage data and the switching event of the polarity selector, determine the voltage dynamic diagram of the polarity selector of the on-load tap changer. Based on the voltage dynamic diagram of the polarity selector and the switching state of the on-load tap changer, determine the maximum offset voltage.

[0012] In the embodiments of this application, the on-load tap changer is monitored in real time, and multiple working data of the on-load tap changer are collected based on the monitoring of the on-load tap changer. Multiple working combinations are determined based on the multiple working data of the on-load tap changer and the corresponding working mode. The corresponding switching state is determined based on the multiple working combinations and the current working content of the on-load tap changer. This approach takes into account the overall consideration of multiple working combinations and the current working content of the on-load tap changer, ensuring the accuracy of the corresponding switching state.

[0013] At this point, using a current transformer or a high-precision current sensor to accurately measure the magnitude and waveform of the current flowing through the switch can reflect the load condition and potential arcing phenomena; by using a voltage transformer or voltage sensor to obtain voltage data between the two ends of the switch and between each contact, it is crucial for determining the recovery voltage when the contacts separate; temperature sensors are installed on key heat-generating parts such as contacts and windings to monitor temperature changes in real time; abnormal temperature rises are often a direct manifestation of poor contact, overload, or arcing.

[0014] By using displacement sensors or encoders, the actual position and movement of the polarity selector contacts are accurately tracked, which can directly reflect whether the mechanical action of the switch is in place, and whether there is jamming or delay. All the collected data will be transmitted in real time to the central data acquisition system or monitoring platform, providing a basis for subsequent in-depth analysis.

[0015] By combining multi-dimensional data with the operating state of the switch, a clearly directional "operating combination" is formed, thus more accurately depicting the instantaneous state of the switch. At this point, based on real-time collected data such as current, voltage, and temperature, the operating states can be preliminarily divided into: steady-state operation: current and voltage waveforms are stable, and temperature fluctuates within the normal range; voltage regulation process: current and voltage exhibit regular or irregular fluctuations, while mechanical position data changes; fault state: phenomena such as sudden current changes, abnormal voltage drops or spikes, and rapid temperature increases occur. Based on the design function of the on-load tap changer, its operating states can be divided into: Positive voltage regulation: The polarity selector contact switches from the "-" position to the "+" position, aiming to increase the transformer output voltage; Reverse voltage regulation: The polarity selector contact switches from the "+" position to the "-" position, aiming to decrease the transformer output voltage; Neutral point grounding: The contact is connected to the neutral point for system grounding; By cross-combining information from these two dimensions, a series of specific operating combinations can be formed; For example, "steady-state operation, positive voltage regulation" refers to the stable state after the switching is completed; "voltage regulation process, reverse voltage regulation" clearly indicates that the switch is in the process of reducing voltage; "fault state, abnormal current" directly points to a specific electrical fault.

[0016] The system combines the previously determined work combination with the current working command of the switch to determine its precise switching state and assess its safety. The system simultaneously analyzes two key inputs: the physical state reflected by the current work combination and the current working content issued by the control system (e.g., "execute positive voltage regulation" command). By comparing and verifying the two, a conclusion can be drawn. Through this series of coherent monitoring, combination, and judgment, the system can accurately identify that the switch is in a switching state with serious safety hazards. In this way, maintenance personnel can immediately receive an alarm and take emergency measures (such as interrupting operation or arranging maintenance), thereby effectively avoiding equipment damage and ensuring the safe and stable operation of the entire power system. Furthermore, the polarity selector of the on-load tap changer is marked, and multiple voltage data corresponding to the polarity selector of the on-load tap changer are collected. Based on the multiple voltage data and the switching events of the polarity selector, the voltage dynamic diagram of the polarity selector of the on-load tap changer is determined. Based on the voltage dynamic diagram of the polarity selector and the switching state of the on-load tap changer, the maximum offset voltage is determined. This method takes into account both the voltage dynamic diagram of the polarity selector and the switching state of the on-load tap changer, ensuring the accuracy of the maximum offset voltage.

[0017] At this point, in order to accurately analyze the complex switching system, it is essential to ensure that each individual polarity selector can be clearly identified. This step is achieved by establishing a unique identifier, laying the foundation for subsequent data acquisition and analysis. Specific methods include physical labeling and digital labeling. Physical labeling involves using durable labels or different colored paints on each polarity selector body to distinguish them, making it easy for on-site personnel to identify. In the data acquisition system, each polarity selector is assigned a unique digital identifier (ID) to ensure that all acquired data can be accurately mapped to the specific device.

[0018] Dedicated voltage sensors are installed between the critical contacts of the polarity selector to measure the voltage difference between the contacts in real time. The signals from these sensors are fed into a high-speed data acquisition system that can continuously record voltage data at extremely high frequencies (e.g., 1 kHz or higher). Such a high sampling frequency is crucial because it ensures that the short-lived voltage transients and spikes that occur during switching are captured. These transient phenomena are often key indicators of potential safety risks.

[0019] After collecting massive amounts of raw voltage data, it needs to be transformed into an intuitive visualization analysis tool—a voltage dynamic graph. This step aims to reveal the complete voltage change trend of the polarity selector during the switching process in a graphical way. The collected voltage data is plotted as a voltage-time curve, which allows a visual view of the entire process of voltage evolution over time. Secondly, by calculating the voltage difference between adjacent contacts, the sudden voltage changes are analyzed, which helps to identify unstable stages in the switching process. The voltage peaks in the curve are specifically analyzed to study their occurrence time and specific magnitude in order to determine whether overvoltage phenomena exist. This is an important step in assessing the insulation performance and arc risk of the equipment.

[0020] Based on the voltage dynamic graph, the next step is to quantitatively assess the maximum risk point during the switching process—the maximum offset voltage. This parameter is directly related to the safety margin of the equipment. The voltage peak value is accurately identified in the voltage dynamic graph, that is, the specific value when the voltage reaches its maximum value. This peak voltage is compared with a reference point (usually the neutral point voltage), and the actual offset voltage is calculated. This maximum offset voltage value is a key quantitative indicator for assessing the safety of switching, as it directly reflects the maximum electrical stress borne by the contacts at the moment of switching.

[0021] refer to Figure 3 In step S12, the specific steps are as follows: S121: Collect the circuit diagram of the on-load tap changer, determine the corresponding resistor matching content based on the circuit diagram, the maximum offset voltage of the polarity selector and the corresponding current state, and determine the corresponding zinc oxide nonlinear resistor based on the identification of the resistor matching content. S122: Position the contact terminal of the polarity selector of the on-load tap changer and connect the zinc oxide nonlinear resistor to the contact terminal of the polarity selector of the on-load tap changer. At this time, connect the zinc oxide nonlinear resistor in series between the contact K of the polarity selector and "+" or "-" to ensure that the installation position and connection method of the zinc oxide nonlinear resistor are reasonable and to ensure its normal operation.

[0022] In the embodiments of this application, the circuit diagram of the on-load tap changer is acquired, and the corresponding resistor matching content is determined based on the circuit diagram, the maximum offset voltage of the polarity selector and the corresponding current configuration. The corresponding zinc oxide nonlinear resistor is determined based on the identification of the resistor matching content, which takes into account the overall consideration of resistor matching content identification and ensures the accuracy of the corresponding zinc oxide nonlinear resistor.

[0023] At this point, retrieve the accurate circuit diagram of this model of on-load tap changer. This diagram is the basic blueprint for all subsequent electrical calculations and simulations. It not only depicts in detail the connection relationships between the main winding, tap winding, and various contacts of the polarity selector (such as K, K+, K-), but more importantly, it must include or be able to derive the parasitic capacitance parameters between each part, such as the coupling capacitance (C1) between the main winding and the tap winding and the capacitance (C2) of the tap winding to ground. These capacitances are the physical source of the dangerous recovery voltage generated at the moment of switching. Therefore, having an accurate circuit diagram is a prerequisite for effective protection design.

[0024] The system transforms abstract fault risks into specific, quantifiable component parameters. It comprehensively analyzes three core inputs: first, the newly acquired circuit diagram, which provides the basis for calculating voltage and current paths; second, the measured maximum offset voltage obtained from the preceding detection steps (such as S11), which is the trigger threshold that the protection component must respond to; and third, the current form of the polarity selector itself, including its model, insulation class, rated voltage, and physical limitations such as internal structural dimensions. Through comprehensive calculation of this information, the system generates a detailed list of "resistance matching contents," which typically includes: nominal varistor voltage (V_n), current capacity (I_k), maximum energy absorption capacity (W_max), residual voltage level (V_r), and key parameters such as physical dimensions and mounting interfaces.

[0025] The system uses all the technical parameters in the list as strict screening criteria to query and match them in a database containing various zinc oxide resistor specifications. The system will then select candidate models that meet all the requirements and recommend an optimal choice based on comprehensive indicators such as cost, lifespan, and reliability. The output is a specific, purchasable zinc oxide nonlinear resistor model, thus completing a complete closed loop from fault diagnosis to solution development.

[0026] Specifically, during the safety test of the A-type on-load tap changer, the preliminary steps determined that the maximum offset voltage generated when the moving contact K is disconnected from the "+" contact during the "reverse voltage regulation" operation is 5.8kV; the system retrieved the official circuit diagram of the A-type switch; the drawing clearly indicates that the coupling capacitance C1 between the main winding and the tap winding is 150pF, and the capacitance C2 of the tap winding to ground is 300pF. These data provide key inputs for subsequent calculations.

[0027] The maximum offset voltage is 5.8kV, and the insulation class of the A-type switch is 10kV. The internal space available for installing protective components is Φ30mm x 60mm. The nominal varistor voltage (V_n) is set at 6.8kV to ensure reliable operation under an offset voltage of 5.8kV, while allowing a 15%-20% safety margin to cope with temperature changes and component aging. The current carrying capacity (I_k) is estimated based on the capacitance value and voltage change rate. The inrush current, combined with a safety factor, determines that the required current capacity should not be less than 10kA (8 / 20μs waveform); energy absorption capacity (W_max): based on the capacitor energy storage formula E=1 / 2×C×V², the system estimates the energy of a single discharge and determines that the required energy absorption capacity should not be less than 4kJ; the system generates a precise procurement requirement list: {V_n:6.8kV, I_k:≥10kA, W_max:≥4kJ, physical dimensions:≤Φ30mmx60mm}.

[0028] The system inputs this list into the component database for matching; after screening, a zinc oxide nonlinear resistor with the model number "YH-W6.8K / 10K" is selected; its specifications show: nominal varistor voltage of 6.8kV, current capacity of 10kA, energy absorption capacity of 5kJ, and physical dimensions of Φ25mm x 50mm; all parameters of this model perfectly match the list requirements, and its size is smaller than the available space, making it easy to install.

[0029] Furthermore, the contact terminals of the polarity selector of the on-load tap changer are positioned, and the zinc oxide nonlinear resistor is connected to the contact terminals of the polarity selector of the on-load tap changer. At this time, the zinc oxide nonlinear resistor is connected in series between the contact K of the polarity selector and the "+" or "-" to ensure that the installation position and connection method of the zinc oxide nonlinear resistor are reasonable and to ensure its normal operation. This introduces the reasonable installation position and connection method of the zinc oxide nonlinear resistor.

[0030] At this point, the system will call the 3D CAD model, assembly drawing, and electrical wiring diagram of the switch model as data sources. Through these drawings, the system can identify the polarity selector component in virtual space and accurately locate the physical leads of the moving contact K and the two fixed contacts "+" and "-", including their spatial coordinates, geometry, and operable areas. In addition, the system will also perform virtual assembly simulation to analyze whether the installation tools or robotic arms can contact these terminals without interference in a limited space, and assess the surrounding electromagnetic and thermal environment, providing a basis for the selection of subsequent installation processes.

[0031] The connection method needs to be designed according to the specific form of the contact terminals (such as studs, connecting pieces, etc.), which involves special wire lugs, conductive clips, or laser welding processes. Next, the critical parallel connection operation is performed: the two leads of the zinc oxide nonlinear resistor are connected to the moving contact K and a fixed contact (e.g., "+") respectively. To achieve full-range protection, two resistors are usually installed, one in parallel between K and "+", and the other in parallel between K and "-". After the connection is completed, the resistor body and leads must be reliably insulated and mechanically fixed using insulating sleeves, cable ties, or special clamps to ensure that the connection will not loosen or come into accidental contact with other components under long-term mechanical vibration and complex working conditions.

[0032] Electrical continuity testing is performed using a high-impedance tester to confirm continuity and absence of loose connections between the resistor and contact terminals. Next, insulation resistance testing is conducted, measuring the insulation resistance of the resistor leads and body to other switch components and ground to eliminate short-circuit risks. Then, the system adds the installed resistor model to the circuit diagram and re-simulates to verify that the resistor conducts as expected and clamps the voltage at a safe level under maximum offset voltage. The system automatically generates a detailed installation report, including installation location, connection method descriptions, and all test data, comparing it with the initial design requirements to ensure all parameters comply with the "resistance matching" specifications.

[0033] Specifically, a zinc oxide nonlinear resistor of model "YH-W6.8K / 10K" was selected for switch A to address its 5.8kV offset voltage issue. The system loaded a 3D model of switch A and quickly identified the polarity selector as being located in the lower middle part of the switch tank. The model showed that the lead-out of the moving contact K was an M6 copper stud, while the leads-out of the fixed contacts "+" and "-" were two copper terminals spaced 30mm apart. Simulation analysis confirmed that a miniature robotic arm could enter through the maintenance port on the top of the switch and reach the installation position without interference.

[0034] The system instructs the operator to use two wire lugs with M6 threaded holes to crimp them to both ends of the "YH-W6.8K / 10K" resistor. The operator then secures one wire lug to the stud on the moving contact K with an M6 nut, and uses a special conductive clip to firmly clamp the other wire lug to the terminal block of the fixed contact "+". In this way, the first resistor is successfully connected in parallel between K and "+". The same operation is performed again between K and "-" to install the second resistor, achieving full protection. The operator wraps all connection points with high-temperature resistant and transformer oil resistant insulating sleeves and uses flame-retardant cable ties to fix the resistor body to a nearby insulating support.

[0035] The operator used a multimeter to measure and confirm that both resistors were correctly connected in parallel across the corresponding contacts and that the connection was secure. An insulation megohmmeter was used to measure and confirm that the insulation resistance between the resistor leads and the switch housing was greater than 1000MΩ, fully complying with safety standards. The system automatically generated a report detailing the installation location, connection method, and various test data, and compared it with the matching information in step S121 (V_n=6.8kV, I_k=10kA, etc.), and the results were completely consistent.

[0036] refer to Figure 4 In step S13, the specific steps are as follows: S131: Real-time monitoring of the zinc oxide nonlinear resistor and marking the resistance data of the zinc oxide nonlinear resistor at different times to collect multiple resistance data of the zinc oxide nonlinear resistor, and determine the resistance change event of the zinc oxide nonlinear resistor based on the multiple resistance data of the zinc oxide nonlinear resistor and the corresponding energizing state. S132: Based on the detection of resistance change events of zinc oxide nonlinear resistor, multiple sub-resistance change contents are determined, and the first sub-conduction event is determined according to the multiple sub-resistance change contents and the connection position of zinc oxide nonlinear resistor; S133: Determine the second sub-conduction event based on the changes in multiple sub-resistance values ​​and the circuit diagram corresponding to the on-load tap changer, and determine the conduction state of the zinc oxide nonlinear resistor based on the first and second sub-conduction events.

[0037] In the embodiments of this application, the zinc oxide nonlinear resistor is monitored in real time, and the resistance data of the zinc oxide nonlinear resistor at different times is marked to collect multiple resistance data of the zinc oxide nonlinear resistor. The resistance change event of the zinc oxide nonlinear resistor is determined based on the multiple resistance data of the zinc oxide nonlinear resistor and the corresponding energizing state. This approach takes into account the overall consideration of multiple resistance data of the zinc oxide nonlinear resistor and the corresponding energizing state, ensuring the accuracy of the resistance change event of the zinc oxide nonlinear resistor.

[0038] At this point, a dedicated monitoring circuit is designed. This circuit typically consists of a constant current source and a high-resolution, high-speed analog-to-digital converter (ADC). Its working principle is as follows: the constant current source injects a small, constant test current (e.g., 1mA) into the zinc oxide nonlinear resistor, and the high-speed ADC measures the voltage drop across the resistor at an extremely high frequency. Since the injected current is constant, any change in voltage directly reflects the change in resistance. In order to capture the fast response at the nanosecond to microsecond level, the sampling frequency of the ADC must reach the megahertz level. The monitoring system is synchronized with the control system of the on-load tap changer. Once it receives the trigger signal that the switching is about to begin, it will immediately enter the data recording mode with the highest sampling rate to ensure that no critical details are missed.

[0039] During high-speed monitoring, a massive amount of analog signals are generated. These signals are converted into structured digital data that can be analyzed. Each resistance data point obtained through ADC conversion is assigned a high-precision timestamp. This timestamp comes from a unified, highly stable clock source. Its function is to ensure that the resistance data can be accurately time-aligned with data from other sensors (such as contact voltage and current sensors), laying the foundation for subsequent comprehensive analysis. During the brief time window of the switching action (lasting only a few hundred microseconds), these timestamped data points are temporarily stored in a high-speed cache. After the action is completed, the system quickly organizes these data into a complete time-series dataset, i.e., "multiple resistance data", and saves it to non-volatile memory for subsequent analysis.

[0040] The system runs a specialized event detection algorithm that scans the entire data sequence in real time or afterward, looking for abrupt changes that simultaneously satisfy two key characteristics: first, the magnitude of the change, where the resistance value drops by more than several preset orders of magnitude instantaneously (e.g., from 10MΩ to below 100Ω); and second, the rate of change, where the slope of the resistance value drop is extremely steep, indicating that it was completed in a very short time. Once the algorithm detects an abrupt change that simultaneously satisfies both conditions, it determines that a "resistance change event" has occurred. The system automatically records a series of key parameters of the event, such as the start time, end time, lowest resistance value, and duration, thereby transforming a continuous physical process into a clear, quantifiable, and structured event.

[0041] Specifically, the A-type switch has a "YH-W6.8K / 10K" zinc oxide resistor Rp installed. Now, a "reverse voltage regulation" operation is required (the moving contact K is disconnected from the "+" contact) to verify whether the protection is effective as expected. The monitoring system receives the "reverse voltage regulation start" command from the switch control unit and immediately starts high-speed sampling at the megahertz level. The constant current source starts injecting a 1mA test current into Rp, and the high-speed ADC records the voltage across Rp at full speed to calculate its real-time resistance value.

[0042] Within the time window from T=0ms (switching start) to T=5ms, the system collected thousands of data points; each data point was marked with a timestamp accurate to microseconds, forming the following sequence: {timestamp: 2.351121s, resistance value: 10.2MΩ}, {timestamp: 2.351122s, resistance value: 10.1MΩ}...; at timestamp 2.351351s, the data sequence changed dramatically: the previous data point was {timestamp: 2.351351s, resistance value: 9.8MΩ}, and the next data point immediately became {timestamp: 2.351351001s, resistance value: 2.5Ω}.

[0043] When scanning the data sequence, the event detection algorithm detected a sudden drop in resistance of more than six orders of magnitude at a precise time point of 2.351351s. The algorithm immediately determined that a successful "resistance change event" had occurred at 2.351351s. The system automatically generated an event report, which recorded in detail the start time of the event, the fact that it lasted for about 150 microseconds before returning to a high-resistance state, and the lowest resistance of 2.5Ω during conduction.

[0044] Furthermore, multiple sub-resistance change events are determined based on the detection of resistance change events of the zinc oxide nonlinear resistor. The first sub-conduction event is determined based on the multiple sub-resistance change events and the connection position of the zinc oxide nonlinear resistor. This approach takes into account the overall consideration of multiple sub-resistance change events and the connection position of the zinc oxide nonlinear resistor, ensuring the accuracy of the first sub-conduction event.

[0045] At this point, the system will perform a detailed analysis of the resistance data sequence recorded in S131, extracting a series of key sub-resistance value changes. These include: the precise start and end times of the event, the total duration, the steady-state resistance value before conduction, the minimum resistance value reached during conduction, the peak conduction current calculated based on voltage and resistance, and the residual voltage across the resistor when the peak current flows. These parameters together constitute a complete and multi-dimensional description of the protective element's behavior.

[0046] The system retrieves the physical connection information of the zinc oxide nonlinear resistor, for example, it is connected in parallel between the moving contact K and the fixed contact "+" of the polarity selector. Then, the system compares the "sub-resistance value change content" generated in the previous step with the built-in rule base based on electrical principles and protection logic. This comparison process is very rigorous, including: time matching, that is, whether the start time of the event closely matches the moment when the polarity selector contact K is disconnected from "+"; amplitude matching, that is, whether the peak conduction current and residual voltage are within the rated parameter range of this type of resistor; and characteristic matching, that is, whether the resistance drop and recovery curves conform to the typical nonlinear current-voltage characteristics of zinc oxide material.

[0047] If all the content closely matches the expected patterns in the rule base, the system identifies a "first sub-conduction event," which indicates that, from the perspective of the component's own behavior, it did indeed conduct at the predetermined time and in the expected manner.

[0048] Specifically, the resistor Rp of the A-type switch successfully captured a resistance change event; the system performed in-depth analysis of the recorded event data and automatically generated a detailed "sub-resistance change content" report: {start time: 2.351351s, duration: 150μs, minimum resistance: 2.5Ω, peak current: 500A, residual voltage: 1.25kV}. This report accurately quantifies all the key performance characteristics of the resistor during the operation.

[0049] The system query found that the resistor Rp is installed in parallel between the moving contact K and the fixed contact '+'. The system query also found that the resistor Rp is installed in parallel between the moving contact K and the fixed contact '+'. The start time of resistor conduction (2.351351s) and the moment the contacts physically disconnect (2.351350s) differ by only 1 microsecond, which is highly consistent within the system error range. This strongly indicates that the resistor responds immediately at the instant the contacts separate and the voltage recovers. The measured peak current of 500A and residual voltage... The voltage drop of 1.25kV is within the safe range of the rated current capacity and residual voltage characteristic curve of the resistor "YH-W6.8K / 10K", indicating that its working state is normal and there is no overload. The resistance drops sharply from a high resistance state of more than 10MΩ to a low resistance state of 2.5Ω, which is a typical conduction characteristic of a zinc oxide resistor under overvoltage impact. Event judgment: Since all the "sub-resistance value changes" are completely consistent with the expected logic of protection action occurring "between K and '+'", the system successfully determined a "first sub-conduction event".

[0050] Therefore, the second sub-conduction event is determined based on the changes in multiple sub-resistance values ​​and the circuit diagram corresponding to the on-load tap changer. The conduction state of the zinc oxide nonlinear resistor is determined based on the first and second sub-conduction events. This approach takes into account both the first and second sub-conduction events, ensuring the accuracy of the conduction state of the zinc oxide nonlinear resistor. A maximum offset voltage is introduced to control the zinc oxide nonlinear resistor. This approach takes into account the resistance change events of the zinc oxide nonlinear resistor, the corresponding connection positions, and the circuit diagram corresponding to the on-load tap changer, thus improving the accuracy of detecting the conduction state of the zinc oxide nonlinear resistor.

[0051] At this point, the system uses the sub-resistance value changes extracted in S132 (such as conduction time, residual voltage, etc.) as input and loads these parameters into the digital circuit model of the on-load tap changer. The model performs a fast transient simulation to predict what changes should occur in the electrical quantities of other key nodes in the circuit when the resistor conducts with specific parameters at a specific time. For example, the voltage between contacts should be clamped at the residual voltage level. The system retrieves the actual measurement data collected by other sensors at the same time and compares it point by point with the simulation prediction results. If the actual data and the simulation prediction are highly consistent in waveform, amplitude, and timing, the system determines a "second sub-conduction event," which indicates that the conduction behavior of the resistor does indeed trigger the expected chain reaction in the real circuit.

[0052] The system integrates the "first sub-conduction event" from the component itself and the "second sub-conduction event" from the system response, and makes a high-confidence comprehensive judgment through a decision fusion logic; the final conduction state is divided into three types: Status: On; When both the first sub-on event and the second sub-on event are successfully detected and are completely consistent in time and logic, the system determines that it is "on", which indicates that the protection element has successfully acted as expected and effectively suppressed the overvoltage; Status: Not conducting; When neither of the two events is detected, the system determines it to be "not conducting", which means that the switching process has not reached the protection action threshold, or the protection element has failed; Status: Abnormal / Fault; When a logical contradiction occurs, the system is judged as "abnormal"; for example, if a change in the resistance itself is detected but the system does not respond, it means that the resistance performance has deteriorated; conversely, it means that other unexpected faults have occurred, and this status requires immediate in-depth diagnosis.

[0053] Specifically, the system inputs the key parameters extracted from S132, such as {residual voltage: 1.25kV, conduction time: 2.351351s}, into the circuit model of the A-type switch; the simulation results predict that at 2.351351s, the voltage between the moving contact K and the fixed contact "+" should be forced to clamp at a level of about 1.25kV from its rising trend of about to reach a dangerous 5.8kV.

[0054] The system retrieves the actual data recorded by the voltage sensor installed between K and "+". The data shows that at 2.351351s, the voltage was indeed instantly suppressed from the surge state and stabilized at 1.26kV, which is highly consistent with the simulation prediction of 1.25kV. Since the actual system response perfectly matches the model prediction, the system successfully identified a "second sub-conduction event".

[0055] The system enters the final decision logic; First sub-conduction event: confirmed; the resistor itself turned on at the correct time and with the correct parameters; Second sub-conduction event: confirmed; the circuit system also produced the expected and effective voltage clamping effect; Since these two independent chains of evidence (the component's own behavior and the system's macroscopic response) both point to the same conclusion and corroborate each other, the system finally determines that the conduction state of the zinc oxide nonlinear resistor Rp is "conduction".

[0056] refer to Figure 5 In step S14, the specific steps are as follows: S141: Collect multiple working data of the polarity selector and perform dynamic detection on the polarity selector to acquire real-time images of the polarity selector, and determine multiple safety control positions of the polarity selector based on the recognition of the real-time images of the polarity selector. S142: Determine the first control area based on the multiple safety control positions of the polarity selector and the multiple operating data of the polarity selector; determine the second control area based on the multiple safety control positions of the polarity selector and the conduction state of the zinc oxide nonlinear resistor; and construct and determine the safety detection area of ​​the polarity selector of the on-load tap changer based on the first control area and the second control area.

[0057] In the embodiments of this application, multiple working data of the polarity selector are collected, and the polarity selector is dynamically detected to collect real-time images of the polarity selector. Multiple safety control positions of the polarity selector are determined based on the recognition of the real-time images of the polarity selector, which takes into account the overall consideration of the recognition of the real-time images of the polarity selector and ensures the accuracy of the multiple safety control positions of the polarity selector.

[0058] At this point, the Data Acquisition System (DAQ) will synchronously acquire multiple working data from step S11 with high time accuracy. These include electrical data such as load current and voltage across the contacts, as well as mechanical data such as drive motor current and contact position encoder values. Most importantly, all acquired data will be stamped with a unified high-precision timestamp. This ensures that a particular frame of image can be accurately correlated with the electrical and mechanical states at the same time, achieving "image-data" synchronization and laying the foundation for subsequent comprehensive analysis.

[0059] After acquiring synchronized operating data, the system then captures high-speed dynamic images of the polarity selector during its operation to obtain instantaneous physical phenomena that are invisible to the naked eye. This requires deploying high-voltage, transformer oil-resistant, high-speed industrial cameras or industrial endoscopes on the switch's observation window or specially designed flange interface. The camera's shooting is precisely triggered by the switch's control signal. When the system issues a "switching start" command, the camera immediately starts and continuously shoots at the key parts of the polarity selector at an extremely high frame rate (e.g., 2000 frames / second) until the switching action is completed. The system will output a high-frame-rate video stream or a series of continuous real-time images, completely recording the entire process of contact separation, movement, and closure.

[0060] The system performs preprocessing on the acquired raw images, such as noise reduction and contrast enhancement. It employs a deep learning-based target detection algorithm, which is pre-trained and can identify specific components in the image, such as the moving contact K and the fixed contact "+". After identifying the components, the system further uses a key point detection algorithm to accurately locate the feature points on them, such as the tip of the contact or the center point of the edge contour. The system maps the pixel coordinates in these images to actual physical coordinates and outputs a list containing multiple key locations, namely "multiple security control locations", each location including its name, coordinates, and recognition confidence level.

[0061] Specifically, the A-type switch is performing a "reverse voltage regulation" operation (moving contact K is disconnected from "+") to detect whether gas is generated due to electric arc; at T=0, the system issues a switching command; the data acquisition system synchronously records the operating conditions at this time: {Time: T+0ms, Command: Reverse voltage regulation, Load current: 500A, Contact position: Closed}.

[0062] At time T=0, the system issues a switching command; the data acquisition system synchronously records the operating conditions at this time: {Time: T+0ms, Command: Reverse voltage regulation, Load current: 500A, Contact position: Closed}; this frame image is immediately sent to the computer vision module for processing; the target detection algorithm successfully identifies three components in the image: "moving contact K", "fixed contact +", and "insulation support"; the key point detection algorithm further refines the positioning: the pixel coordinates of the tip of the moving contact K are (250, 300); the pixel coordinates of the center of the surface of the fixed contact "+" are (250, 350); the system finally outputs a series of structured safety control positions: Safety control position 1: {Name: K contact tip, coordinates: (250, 300)}; Safety control position 2: {Name: + contact surface, coordinates: (250, 350)}; Safety control position 3: {Name: gap between K and +, coordinates: (250, 325)}.

[0063] Furthermore, a first control region is determined based on multiple safety control positions and multiple operating data of the polarity selector, and a second control region is determined based on multiple safety control positions and the conduction state of the zinc oxide nonlinear resistor. The safety detection region of the polarity selector of the on-load tap changer is constructed based on the first and second control regions, which is compatible with the overall consideration of the construction of the first and second control regions and ensures the accuracy of the safety detection region of the polarity selector of the on-load tap changer.

[0064] At this point, the system will delineate a basic risk concern area based on conventional electrical conditions and physical structure. This area mainly reflects the locations where wear or minor risks occur due to the inherent electrical stress (such as load current) of the switching action itself under ideal or conventional protection conditions. The system will receive safety control positions (such as contact coordinates) from S141 and working data (such as load current) from S11. A built-in rule engine based on electrical engineering knowledge will dynamically adjust the size of the area according to the working data. Its core logic is: the larger the load current, the greater the arc energy generated when the contacts separate (even if it is successfully suppressed), and the higher the potential risk of ablation. Therefore, the control area should be expanded accordingly. The system will use the key safety control positions as the geometric center and calculate a three-dimensional space (such as a sphere or cylinder) according to the magnitude of the load current through a preset algorithm, and assign it a basic risk level.

[0065] The system will reassess and dynamically adjust the risk area based on the actual protection effect of the zinc oxide nonlinear resistor. This area directly reflects whether the protection system is successful, failed, or abnormal. The system will receive the safety control position and the resistor conduction status from S13. This is a condition-driven logic branch: if the conduction status is "conducting", it indicates that the protection is successful, the dangerous recovery voltage is effectively clamped, and the arc is suppressed. At this time, the risk is extremely low, and the second control area will shrink drastically, or even be set to zero. Conversely, if the conduction status is "not conducting" or "abnormal", it indicates that the protection has failed. The polarity selector will bear the entire recovery voltage, and there is a high probability of a strong arc breakdown. At this time, the risk is extremely high, and the second control area will expand drastically, covering the entire arc channel between the moving contact and the fixed contact, as well as the surface of all nearby insulating components burned by the high-temperature arc.

[0066] The system will merge the first and second control areas using spatial fusion algorithms (such as spatial union or weighted logic). The basic principle is that the final risk area must cover all potential risk points. If the second control area, representing protection failure, is activated, its high risk level and large spatial range will dominate the final detection result. The system will render the final generated security detection area in real time and overlay it onto a real-time image or 3D model to form a highlighted, dynamically visualized area with different colors indicating the risk level, which will be provided directly to the operator or used as input for subsequent risk event identification.

[0067] Specifically, the A-type switch is performing a "reverse voltage regulation" operation, with a current load current of 500A. The first control zone is determined by the system acquiring the spatial coordinates of the moving contact K tip (P_K) and the fixed contact "+" surface (P_plus), as well as the current load current of 500A. Based on the 500A current, the system calculates, using a built-in algorithm, that the typical ablation radius on the contact surface requiring attention is 2mm. The system generates two spherical regions with a radius of 2mm centered on P_K and P_plus, which serve as the first control zone and are assigned a "medium" risk level.

[0068] Determine the second control area: The system obtains the position of the gap between K and "+" (P_gap) and learns from step S13 that the zinc oxide resistor is in the "conducting" state; since the protection is successful, the system determines that the dangerous arc risk has been eliminated; the system sets the second control area as a small point with a radius of only 0.5mm, located at the center of P_gap, for confirmatory monitoring of "no arc" and assigns it a "low" risk level.

[0069] The system spatially merges the first and second control areas; since the risk level (low) of the second control area is much lower than that of the first control area (medium), the final area is mainly defined by the first control area; output: the final safety detection area is two bright spheres with a radius of 2mm covering the surfaces of the K contact and the "+" contact; on the real-time monitoring screen, the operator will see these two contact surfaces highlighted, indicating that the system is closely monitoring the long-term wear of this area, while there are no large risk markings in the contact gap.

[0070] refer to Figure 6 In step S15, the specific steps are as follows: S151: Detect the security detection area and determine multiple sub-risk locations based on the detection of the security detection area. Determine risk events based on each sub-risk location, the corresponding risk behavior, and multiple working data of the polarity selector. S152: Collect the operating status of the on-load tap changer, determine the first safety factor based on the operating status of the on-load tap changer and the risk event, determine the second safety factor based on the operating status of the on-load tap changer and the conduction state of the zinc oxide nonlinear resistor, and determine the safety level of the polarity selector of the on-load tap changer based on the mapping relationship between the first safety factor, the second safety factor and the safety level.

[0071] In the embodiments of this application, the security detection area is detected, and multiple sub-risk locations are determined based on the detection of the security detection area. Risk events are determined based on each sub-risk location, the corresponding risk behavior, and multiple working data of the polarity selector. This approach takes into account the overall consideration of each sub-risk location, the corresponding risk behavior, and multiple working data of the polarity selector, ensuring the accuracy of risk events.

[0072] At this point, after delineating the safety detection area requiring attention, the system will perform multimodal and depth scanning to detect any potential anomalies and accurately locate their physical coordinates. This process does not rely solely on a single image but integrates data from multiple sensors for comprehensive detection. The system will analyze image pixels within the area through visual detection to find anomalies that are inconsistent with the normal background, such as instantaneous high-brightness pixels (for electric arcs) or local color darkening (for carbonization). Through thermal imaging detection, the system will analyze the temperature distribution within the area to identify "hot spots" where the temperature is abnormally higher than the surrounding area. If equipped with spectral detection, the system will also analyze the spectral composition of light to detect the characteristic spectral lines unique to metal vapor arcs. When any detection mode detects an anomaly, the system will record the precise coordinates of the anomaly, forming a "sub-risk location" with anomaly type and confidence level.

[0073] The system aligns and correlates three types of information over time: spatial information (where the sub-risk is located), behavioral information (what the corresponding risk behavior is), and operating condition information (what the equipment is doing at the same time). The system compares this fused information with a predefined risk pattern knowledge base, which stores feature combinations of various typical faults. For example, the risk event corresponding to {location: contact gap, behavior: instantaneous brightening, operating condition: instantaneous switching} is "arc discharge". When a match is successful, the system finally determines a specific risk event, completing the judgment from phenomenon to essence.

[0074] Specifically, switch A is performing a "reverse voltage regulation" operation. Step S14 has designated the "gap between K and +" as a high-priority safety detection area. At T+5.231 milliseconds, the high-speed camera captures the 11th frame image. Within the safety detection area, the system detects a pixel cluster at coordinates (250, 325), whose brightness value instantly exceeds the preset arc light threshold. At the same moment, the thermal imager detects a hot spot near coordinates (250, 325) where the temperature suddenly rises from 80°C to over 1500°C. The system combines these two detection results to generate a high-confidence sub-risk location: {Location: (250, 325), Risk Behavior: Instantaneous high brightness accompanied by a sudden temperature rise, Confidence: 99%}.

[0075] The system correlates the sub-risk location information with the working data at the same time: Space / Behavior: Location (250, 325) is in the contact gap, behavior is instantaneous high brightness and high temperature; Working condition: Working data shows that it is currently in the "contact K and + separation" stage of "reverse voltage regulation" operation, and the load current is 500A; The system matches this fused information package {location: contact gap, behavior: instantaneous high brightness / high temperature, working condition: switching} with the risk pattern knowledge base; Event output: This information package perfectly matches the "arc discharge" pattern in the knowledge base; The system finally identifies a clear risk event: "arc discharge".

[0076] Furthermore, the operating status of the on-load tap changer is collected. A first safety factor is determined based on the operating status of the on-load tap changer and the risk event. A second safety factor is determined based on the operating status of the on-load tap changer and the conduction state of the zinc oxide nonlinear resistor. The safety level of the polarity selector of the on-load tap changer is determined based on the mapping relationship between the first safety factor, the second safety factor, and the safety level. This comprehensive consideration of the mapping relationship between the first safety factor, the second safety factor, and the safety level ensures the accuracy of the safety level of the polarity selector of the on-load tap changer. A safety detection area for the polarity selector is introduced to further control the safety detection area of ​​the polarity selector. This achieves a comprehensive consideration of the risk event, the operating status of the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor, thereby improving the accuracy of the safety level of the polarity selector of the on-load tap changer.

[0077] At this point, the system will assess the health status of the polarity selector body under the current operating conditions and the degree of damage after being subjected to risks. This coefficient mainly reflects the health level of the equipment itself. The system will collect the operating status of the switch (such as load current, cumulative number of actions) and the risk events determined by S151 as inputs. A weighted scoring model based on expert knowledge and historical data will be used for calculation. Usually, a base score (such as 100 points) is used as the starting point, and points are deducted according to the severity of the risk event. For example, the deduction for an "arc discharge" event is much higher than that for a "minor spark".

[0078] The system also introduces a condition correction factor because arcing under high load causes more damage than arcing under low load, and the deduction should be greater. A quantitative first safety factor is calculated using the formula "base score - Σ(risk event deduction score × condition correction factor)," which intuitively reflects the decline in the health of the equipment due to the current risk event.

[0079] The system will evaluate the reliability of the protection system (zinc oxide nonlinear resistor). This coefficient reflects the equipment's ability to withstand risks and is usually more important than the first safety factor because protection failure is catastrophic. The system will collect the operating status of the switch and the resistance conduction status determined by S13 as inputs.

[0080] A state-value mapping table directly maps the conduction state to a safety factor value. If the conduction state is "conducting", it indicates that the protection system is working as expected, and the second safety factor is assigned a high value (e.g., 100 points). If the state is "not conducting", it indicates that the protection has failed and the equipment is exposed to all risks, and the factor is assigned an extremely low value (e.g., 0 points). If the state is "abnormal", it is assigned a moderately low value (e.g., 40 points) as a warning.

[0081] The system calculates a weighted average of the first and second safety factors to obtain a comprehensive safety score. The weighting reflects the design philosophy, with the second safety factor (protection reliability) typically having a higher weight, for example, 0.6, while the first safety factor (equipment health) has a weight of 0.4. The calculation formula is: "Comprehensive Safety Score = (First Safety Factor × 0.4) + (Second Safety Factor × 0.6)". The system has a built-in safety level mapping table that maps the comprehensive safety score to discrete safety levels, such as "Safe", "Caution", "Warning", and "Danger", providing a direct and clear basis for the final operation and maintenance decision.

[0082] Specifically, after a "reverse voltage regulation" operation, the system completed the S151 detection for the A-type switch and detected a risk event. The first safety factor was determined as follows: the system obtained the working status as "load rate 80%" and the risk event as "arc discharge". Starting from a base score of 100, the "arc discharge" event itself deducted 40 points. Since it occurred under a high load of 80%, the working condition correction factor was 1.2. Therefore, the first safety factor = 100 - (40 × 1.2) = 52. This score indicates that the equipment body suffered moderate damage.

[0083] Determine the second safety factor: The system obtains the working status as "switching complete" and learns from step S13 that the conduction state of the zinc oxide resistor is "not conducting"; since the protection system completely fails at the critical moment, the system directly assigns the second safety factor to 0.

[0084] The system calculates according to the preset weights; the comprehensive safety score = (52 × 0.4) + (0 × 0.6) = 20.8; comparing 20.8 with the built-in mapping table, since 20.8 ≤ 50, the system determines that it belongs to the highest risk level; the system determines the safety level of the switch polarity selector as "Level 4 (Dangerous)".

[0085] In another embodiment of this application, during the on-load tap changer's forward and reverse voltage regulation switching, the transformer remains in an energized state. At this time, coupling capacitances (referred to as C1 and C2, respectively) exist between the main winding and the tap winding, and between the tap winding and ground potential (such as the iron core). The presence of these capacitances results in a continuous flow of tens of milliamperes of capacitive current through the polarity selector's contact K.

[0086] When the moving contact K of the polarity selector disconnects from the "+" or "-" fixed contact, it cuts off the capacitor current. This operation causes the tap winding to momentarily separate from the main winding and become floating. Due to the electric field coupling effect, this floating tap winding will induce a coupling potential corresponding to the adjacent winding or core through capacitors C1 and C2. This is the so-called recovery voltage, also often referred to as the offset voltage.

[0087] The continuous increase in this recovery voltage is highly likely to cause insulation breakdown at the break between the moving contact K and the "+" or "-" of the fixed contact. At the instant the contact closes and opens, the voltage on capacitor C1 will decrease, while the voltage on capacitor C2 will increase. The capacitor discharge caused by this recovery voltage will severely burn the contacts and contaminate the transformer oil, thereby affecting the overall operating performance and safety of the converter transformer.

[0088] Specifically, when the moving contact of the polarity selector separates from the fixed contact, the small capacitive current interrupted will generate sparks between the separated contacts, causing the transformer oil to decompose and produce bubbles. Simultaneously, the extremely high recovery voltage generated between the contacts can cause breakdown discharge. This can lead to gas formation in the transformer's main tank, or even a sustained arc, causing a direct short circuit in the tap winding. Furthermore, when the moving contact K connects to the other fixed contact, a capacitive current will also be activated due to the coupling capacitance. This will also cause the polarity switching contact to burn out and decompose, generating gas in the transformer's main tank. These generated gases can easily cause the transformer's gas relay to malfunction, leading to unnecessary equipment downtime and economic losses.

[0089] Please see Figure 7 , Figure 7 This is a schematic diagram of the structural composition of the safety detection device for the polarity selector of the on-load tap changer in an embodiment of the present invention; the safety detection device for the polarity selector of the on-load tap changer includes: Offset voltage module 21 is used to collect multiple operating data of on-load tap changer, determine the corresponding switching state based on the identification of multiple operating data of on-load tap changer, and determine the maximum offset voltage based on the switching state and multiple voltage data corresponding to the polarity selector of on-load tap changer. The resistor matching module 22 is used to match the corresponding zinc oxide nonlinear resistor based on the maximum offset voltage and the on-load tap changer, and connect the zinc oxide nonlinear resistor to the contact terminal of the polarity selector of the on-load tap changer. The resistor status module 23 is used to collect multiple resistance data of the zinc oxide nonlinear resistor, determine the resistance change event of the zinc oxide nonlinear resistor based on the multiple resistance data, and determine the conduction state of the zinc oxide nonlinear resistor according to the resistance change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap changer. The safety detection area module 24 is used to determine the safety detection area of ​​the polarity selector of the on-load tap changer based on the conduction state of the zinc oxide nonlinear resistor, multiple working data of the polarity selector, and the corresponding real-time image. Safety level module 25 is used to determine risk events based on the detection of the safety detection area, and to determine the safety level of the polarity selector of the on-load tap changer based on the risk event, the operating state of the on-load tap changer and the conduction state of the zinc oxide nonlinear resistor.

[0090] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A safety detection method of a polarity selector of an on-load tap changer, characterized in that, The method comprises the following steps: collecting a plurality of working data of the on-load tap-changer, determining a corresponding switching state according to the identification of the plurality of working data of the on-load tap-changer, and determining a maximum offset voltage based on the switching state and a plurality of voltage data corresponding to the polarity selector of the on-load tap-changer; based on the maximum offset voltage and the on-load tap-changer, a corresponding zinc oxide nonlinear resistor is matched, and the zinc oxide nonlinear resistor is connected to the contact end of the polarity selector of the on-load tap-changer; collecting a plurality of resistance data of the zinc oxide nonlinear resistor, determining a resistance value change event of the zinc oxide nonlinear resistor based on the plurality of resistance data, determining a conduction state of the zinc oxide nonlinear resistor according to the resistance value change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap-changer; determining a safety detection area of the polarity selector of the on-load tap-changer according to the conduction state of the zinc oxide nonlinear resistor, the plurality of working data of the polarity selector and the corresponding real-time image; determining a risk event based on the detection of the safety detection area, determining a safety level of the polarity selector of the on-load tap-changer based on the risk event, the working state of the on-load tap-changer and the conduction state of the zinc oxide nonlinear resistor.

2. The safety detection method of a polarity selector of a load tap changer according to claim 1, characterized in that, The method comprises the following steps: real-time monitoring of the on-load tap-changer, collecting a plurality of working data of the on-load tap-changer according to the monitoring of the on-load tap-changer, determining a plurality of working combinations based on the plurality of working data of the on-load tap-changer and the corresponding working mode, and determining a corresponding switching state according to the plurality of working combinations and the current working content of the on-load tap-changer; labeling the polarity selector of the on-load tap-changer, collecting a plurality of voltage data corresponding to the polarity selector of the on-load tap-changer, determining a voltage dynamic diagram of the polarity selector of the on-load tap-changer based on the plurality of voltage data and the switching event of the polarity selector, and determining a maximum offset voltage based on the voltage dynamic diagram of the polarity selector and the switching state of the on-load tap-changer.

3. The safety detection method of a polarity selector of a load tap changer according to claim 1, characterized in that, The method comprises the following steps: collecting a circuit distribution diagram of the on-load tap-changer, determining a corresponding resistance matching content based on the circuit distribution diagram, the maximum offset voltage of the polarity selector and the corresponding current mode, and determining a corresponding zinc oxide nonlinear resistor based on the identification of the resistance matching content; positioning the contact end of the polarity selector of the on-load tap-changer, and connecting the zinc oxide nonlinear resistor to the contact end of the polarity selector of the on-load tap-changer, at this time, the zinc oxide nonlinear resistor is connected in series between the contact K of the polarity selector and "+" or "-".

4. The safety detection method of a polarity selector of a load tap changer according to claim 1, characterized in that, The method comprises the following steps: Real-time monitoring of the zinc oxide nonlinear resistor and marking resistance data of the zinc oxide nonlinear resistor at different time points to collect a plurality of resistance data of the zinc oxide nonlinear resistor, and determining a resistance value change event of the zinc oxide nonlinear resistor according to the plurality of resistance data of the zinc oxide nonlinear resistor and a corresponding conduction state.

5. The safety detection method of a polarity selector of a load tap changer according to claim 4, characterized in that, The method comprises the following steps: Based on the detection of the resistance value change event of the zinc oxide nonlinear resistor, a plurality of sub-resistance value change contents are determined, a first sub-conduction event is determined according to the plurality of sub-resistance value change contents and the connection position of the zinc oxide nonlinear resistor; A second sub-conduction event is determined according to the plurality of sub-resistance value change contents and the circuit distribution diagram corresponding to the on-load tap changer, and the conduction state of the zinc oxide nonlinear resistor is determined based on the first sub-conduction event and the second sub-conduction event.

6. The safety detection method of a polarity selector of a load tap changer according to claim 1, characterized in that, The method comprises the following steps: Collecting a plurality of working data of the polarity selector and dynamically detecting the polarity selector to collect a real-time image of the polarity selector, and determining a plurality of safe control positions of the polarity selector according to the recognition of the real-time image of the polarity selector.

7. The safety detection method of a polarity selector of a load tap changer according to claim 6, characterized in that, The method comprises the following steps: According to the plurality of safe control positions of the polarity selector and the plurality of working data of the polarity selector, a first control area is determined, according to the plurality of safe control positions of the polarity selector and the conduction state of the zinc oxide nonlinear resistor, a second control area is determined, and based on the first control area and the second control area, a safe detection area of the polarity selector of the on-load tap changer is constructed.

8. The safety detection method of a polarity selector of a load tap changer according to claim 1, characterized in that, The method comprises the following steps: Detecting the safe detection area and determining a plurality of sub-risk positions according to the detection of the safe detection area, and determining a risk event according to each sub-risk position, a corresponding risk behavior and a plurality of working data of the polarity selector.

9. The safety detection method of a polarity selector of a load tap changer according to claim 8, characterized in that, The method comprises the following steps: According to the plurality of safe control positions of the polarity selector and the plurality of working data of the polarity selector, a first control area is determined, according to the plurality of safe control positions of the polarity selector and the conduction state of the zinc oxide nonlinear resistor, a second control area is determined, and based on the first control area and the second control area, a safe detection area of the polarity selector of the on-load tap changer is constructed. The working state of the on-load tap-changer is collected, the first safety factor is determined according to the working state of the on-load tap-changer and the risk event, the second safety factor is determined according to the working state of the on-load tap-changer and the conduction state of the zinc oxide nonlinear resistor, and the safety level of the polarity selector of the on-load tap-changer is determined based on the mapping relationship of the first safety factor, the second safety factor and the safety level.

10. A safety detection device for a polarity selector of a load tap changer, characterized in that The safety detection device of the polarity selector of the on-load tap-changer is applied to the safety detection method of the polarity selector of the on-load tap-changer as claimed in any one of claims 1-9, and comprises: The offset voltage module is configured to collect a plurality of working data of the on-load tap-changer, determine a corresponding switching state according to the identification of the plurality of working data of the on-load tap-changer, and determine a maximum offset voltage based on the switching state and a plurality of voltage data corresponding to the polarity selector of the on-load tap-changer; The resistance matching module is configured to match the zinc oxide nonlinear resistor corresponding to the on-load tap-changer based on the maximum offset voltage, and connect the zinc oxide nonlinear resistor to the contact end of the polarity selector of the on-load tap-changer; The resistance state module is configured to collect a plurality of resistance data of the zinc oxide nonlinear resistor, determine a resistance value change event of the zinc oxide nonlinear resistor based on the plurality of resistance data, and determine the conduction state of the zinc oxide nonlinear resistor according to the resistance value change event of the zinc oxide nonlinear resistor, the corresponding connection position and the circuit distribution diagram corresponding to the on-load tap-changer; The safety detection area module is configured to determine the safety detection area of the polarity selector of the on-load tap-changer according to the conduction state of the zinc oxide nonlinear resistor, the plurality of working data of the polarity selector and the corresponding real-time image; The safety level module is configured to determine a risk event based on the detection of the safety detection area, and determine the safety level of the polarity selector of the on-load tap-changer based on the risk event, the working state of the on-load tap-changer and the conduction state of the zinc oxide nonlinear resistor.

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