Dynamic switching type NO2 gas sensor and insulation defect detection method thereof

Abstract

The invention discloses a dynamic switching type NO2 gas sensor and an insulation defect detection method thereof, and belongs to the technical field of gas sensors, the dynamic switching type NO2 gas sensor comprises a gas diffusion layer, a detection electrode layer, a solid electrolyte layer, a shared counter electrode and a substrate supporting layer which are stacked layer by layer, and the detection electrode layer comprises a voltage detection area and a current detection area; the voltage detection area adopts a double-layer electrode; the current detection area adopts an annular electrode; the voltage detection area and the current detection area are isolated through an insulating groove; the sensor is provided with a multi-mode switching strategy and is used for switching a constant-potential electrolysis mode and an open-circuit potential detection mode by detecting the concentration of gas. According to the invention, a dual-electrode design of a voltage detection area and a current detection area is adopted, a multi-mode switching strategy is combined, a constant potential electrolysis mode or an open circuit potential mode is dynamically selected, full-range coverage from a sub-ppm level to a thousand ppm level is realized, and the detection sensitivity and the range adaptability are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a dynamically switching NO2 gas sensor and an insulation defect detection method thereof. Background Art

[0002] In recent years, as power systems continue to evolve toward digitalization, intelligence, and high reliability, condition monitoring and fault warning technologies for power equipment have become a hot topic in research and application. Air-type switchgear has been widely used in medium and low voltage distribution networks due to its simple structure, easy installation, and low maintenance costs. However, over the long term, air-type switchgear can gradually degrade its internal insulation due to various factors such as partial discharge, arc faults, and environmental pollution. This can eventually lead to serious insulation failures, impacting the safe and stable operation of the entire power system.

[0003] Partial discharge, an early sign of insulation defects, causes the decomposition and recombination of gas components within air-type switchgear when it occurs. Specifically, partial discharge and arc faults cause the decomposition of common airborne components such as oxygen, nitrogen, and water vapor, generating highly reactive free radicals such as active oxygen atoms, nitrogen atoms, and OH groups. These primary products then, under certain conditions, undergo a complex series of chemical reactions to generate stable nitrogen dioxide (NO2) gas. Because the NO2 gas generation process is relatively stable, changes in its concentration directly reflect the intensity and duration of partial discharge, making it a key indicator for assessing switchgear insulation defects.

[0004] At present, traditional insulation defect detection methods mostly rely on electromagnetic, acoustic or infrared thermal imaging. However, these methods are susceptible to environmental interference, complex installation and difficult data processing in practical applications, and cannot effectively monitor the historical accumulation effect of partial discharge. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is that the traditional insulation defect detection method is easily affected by environmental interference, has complex installation and is difficult to process data in practical applications, and cannot effectively monitor the historical accumulation effect of partial discharge.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a dynamic switching NO2 gas sensor, which includes the following steps:

[0008] The gas diffusion layer, detection electrode layer, solid electrolyte layer, shared counter electrode, and substrate support layer are stacked layer by layer.

[0009] The detection electrode layer includes a voltage detection area and a current detection area;

[0010] The voltage detection area uses a double-layer electrode and can be used to detect NO2 gas in the concentration range of 10-1500wt.ppm;

[0011] The current detection area uses a ring electrode and can be used to detect NO2 gas in a concentration range of 0.5-10wt.ppm;

[0012] The voltage detection area and the current detection area are isolated by an insulating trench to block signals and prevent signal crosstalk;

[0013] The sensor is configured with a multi-modal switching strategy, switching between a constant potential electrolysis mode and an open circuit potential detection mode according to the concentration of the detected gas.

[0014] As a preferred solution of the dynamic switching NO2 gas sensor described in the present invention, the gas diffusion layer is a porous ceramic membrane structure with a pore size of 1-5 μm.

[0015] The beneficial effect of this preferred technical solution is that by covering the surface of the detection electrode, NO2 gas is allowed to penetrate quickly while preventing dust and liquid pollutants from entering the sensor.

[0016] As a preferred solution of the dynamic switching NO2 gas sensor described in the present invention, the solid electrolyte layer is made of yttrium oxide ceramic material.

[0017] The beneficial effect of this preferred technical solution is that it is prepared into a dense thin layer through high-temperature sintering during processing, and can form a high-efficiency oxygen ion conduction channel.

[0018] As a preferred solution of the dynamic switching NO2 gas sensor described in the present invention, the shared counter electrode layer is a Pt thin film structure.

[0019] As a preferred solution of the dynamic switching NO2 gas sensor described in the present invention, the base support layer is an Al2O3 ceramic plate structure.

[0020] The beneficial effects of this preferred technical solution are: providing mechanical strength and integrating thermistors for temperature compensation.

[0021] As a preferred solution of the dynamic switching NO2 gas sensor described in the present invention, the multi-modal switching strategy includes the following steps:

[0022] Apply voltage through the current detection area, compare the background current with the voltage, and choose to enter low concentration mode, high concentration mode or parallel sampling mode;

[0023] In low concentration mode, voltage is applied and NO2 concentration is detected by transient current peak;

[0024] In high concentration mode, the electromotive force is output and NO2 concentration is calculated in combination with temperature compensation;

[0025] Synchronously acquire voltage and current signals in parallel sampling mode to identify transient discharge events.

[0026] Another object of the present invention is to provide a method for detecting insulation defects of a dynamically switching NO2 gas sensor, comprising the following steps:

[0027] Install the sensor inside the equipment to be tested to monitor the changes in gas concentration in real time;

[0028] The detection mode is adjusted through a multi-modal switching strategy to cover the NO2 concentration range of 0.5-1500wt.ppm;

[0029] Based on the current or voltage signal output by the sensor and the temperature-compensated calculation equation, the NO2 partial pressure is calculated and correlated with the partial discharge intensity.

[0030] When the NO2 concentration is detected as a transient event, an insulation defect warning is triggered, wherein the calculation equation is the Nernst equation.

[0031] As a preferred solution of the insulation defect detection method of the present invention, the transient event determination logic includes:

[0032] When the signal of the current detection area suddenly increases and the voltage detection area is not saturated, it is marked as a partial discharge event and the partial discharge event is output as a transient event.

[0033] As a preferred embodiment of the insulation defect detection method of the present invention, the temperature-compensated calculation equation is expressed as follows:

[0034]

[0035] Where, E is the change in electromotive force measured by the sensor; E0 is the reference potential under standard conditions; R is the gas constant; T is the absolute temperature; n is the number of electrons transferred in the electrochemical reaction; F is the Faraday constant; P NO2 is the partial pressure of NO2 gas.

[0036] The beneficial effects of this preferred technical solution are: refining the technical details of temperature compensation, eliminating environmental interference through high-precision temperature sensors and mathematical correction formulas, and ensuring measurement accuracy

[0037] As a preferred solution of the insulation defect detection method of the present invention, the insulation defect warning includes a hierarchical response logic, specifically,

[0038] When the NO2 concentration exceeds 50ppm continuously, a yellow warning is triggered;

[0039] When the NO2 concentration exceeds 100ppm or there are three transient events within one hour, a red alarm is triggered;

[0040] Record event waveform data, store it on a local SD card, and upload it to a cloud analysis system simultaneously.

[0041] The beneficial effects of this preferred technical solution are: defining an early warning classification mechanism, directly linking the concentration threshold with the operation and maintenance response, reflecting the closed-loop control logic from early warning to emergency disposal, and enhancing the practicality of the solution.

[0042] Beneficial effects of the present invention:

[0043] The dual-electrode design with voltage detection area and current detection area, combined with a multi-modal switching strategy, dynamically selects constant potential electrolysis mode or open circuit potential mode to achieve full range coverage from sub-ppm to 1000ppm, significantly improving detection sensitivity and range adaptability.

[0044] A Pt1000 thin film temperature sensor is integrated into the base support layer to correct the temperature deviation term in the Nernst equation in real time, ensuring the accuracy of NO2 concentration calculation, eliminating temperature interference on sensor output, making long-term monitoring data more stable and reliable, and directly related to the historical evolution trend of insulation defects.

[0045] An insulating trench is set between the voltage detection area and the current detection area to isolate signal crosstalk; in parallel sampling mode, current pulses and electromotive force signals are synchronously collected, and through logical judgment, the sudden characteristics of partial discharge are identified in real time, thereby improving the timeliness of fault warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A cross-sectional view of the layout of a dynamically switching NO2 gas sensor provided in accordance with an embodiment of the present invention.

[0048] Figure 2 A top view of the regional electrode layout and isolation trenches of a dynamically switching NO2 gas sensor provided in accordance with one embodiment of the present invention.

[0049] Figure 3A flowchart of a method for detecting insulation defects in a dynamically switching NO2 gas sensor is provided in accordance with an embodiment of the present invention.

[0050] In the figure: 1. Gas diffusion layer; 2. Detection electrode layer; 21. Voltage detection area; 22. Current detection area; 23. Insulation trench; 3. Solid electrolyte layer; 4. Shared counter electrode; 5. Base support layer. DETAILED DESCRIPTION

[0051] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0052] Example 1, with reference to Figures 1 and 2 , which is the first embodiment of the present invention, provides a dynamically switching NO2 gas sensor, comprising a gas diffusion layer 1, a detection electrode layer 2, a solid electrolyte layer 3, a shared counter electrode 4, and a base support layer 5 stacked layer by layer,

[0053] The detection electrode layer 2 includes a voltage detection area 21 and a current detection area 22;

[0054] The voltage detection area 21 uses a double-layer electrode to detect NO2 gas in the concentration range of 10-1500wt.ppm;

[0055] The current detection area 22 uses a ring electrode to detect NO2 gas in the concentration range of 0.5-10wt.ppm;

[0056] The voltage detection area 21 and the current detection area 22 are isolated by an insulating trench 23 to block signals and prevent signal crosstalk;

[0057] The sensor is equipped with a multi-mode switching strategy, which is used to switch between constant potential electrolysis mode and open circuit potential detection mode by detecting the concentration of the gas.

[0058] Furthermore, the gas diffusion layer 1 is a porous ceramic membrane structure with a pore size of 1-5 μm. By covering the surface of the detection electrode, it allows NO2 gas to penetrate quickly while blocking dust and liquid pollutants from entering the sensor.

[0059] In an optional embodiment, a porous ceramic membrane with a diameter of about 5 mm and a pore size of 3 μm is prepared by ceramic sintering technology to ensure gas diffusion performance and mechanical stability. The ceramic sintering technology uses alumina ceramic powder as raw material and prepares a blank with a diameter of 5 mm and a thickness of 0.5 mm through a dry pressing molding process, which is then sintered at a high temperature of 1600°C for 2 hours to form a porous ceramic membrane with a pore size of 3 μm.

[0060] The 3μm pore size balances the gas diffusion rate and pollutant blocking requirements, avoiding delayed gas response due to a too small pore size or the introduction of pollutants due to a too large pore size; high-temperature sintering ensures the density and chemical stability of the ceramic membrane, making it suitable for the harsh environment of high temperature and high humidity in switch cabinets.

[0061] In another alternative embodiment, a porous ceramic membrane is prepared using a zirconium oxide-toughened alumina composite material through a sol-gel method combined with a foaming process. ZrO2 nanoparticles are mixed with Al2O3 sol to form a uniform slurry. Polymethyl methacrylate microspheres are added, stirred, and then injected into a mold. After room temperature curing, the mixture is sintered at 1450°C for 1.5 hours to form a porous ceramic membrane with a diameter of 5 mm and a thickness of 0.3 mm, with an average pore size of 1.5 μm.

[0062] ZrO2 toughening improves the thermal shock resistance and mechanical strength of the ceramic membrane, adapting to the sudden temperature changes caused by frequent start-stop in the switch cabinet; the 1.5μm pore size further refines the filtration accuracy, suitable for industrial scenarios with extremely high dust concentrations; high porosity and uniform pore size distribution accelerate gas diffusion, improving the sensor's ability to capture transient partial discharges.

[0063] Furthermore, the solid electrolyte layer 3 is made of a stable yttrium oxide ceramic material with excellent oxygen ion conductivity. Therefore, it is prepared into a dense thin layer through high-temperature sintering during processing, which can form an efficient oxygen ion conduction channel.

[0064] In this embodiment, 8 mol% Y2O3-doped ZrO2 powder can be used to form a 50 μm thick green sheet through a tape casting process, and sintered at 1550°C for 4 hours to form a dense YSZ layer with a grain size of 2 μm and clear grain boundaries.

[0065] YSZ ceramics exhibit excellent oxygen ion conductivity of approximately 0.1 S / cm at high temperatures (>600°C). This ensures rapid oxygen ion migration during electrochemical reactions in the sensor, improving response speed and signal stability. YSZ is also resistant to high-temperature oxidation and corrosion, allowing it to operate within switchgear under long-term exposure to gases such as NO2, O2, and H2O. The dense layer formed by high-temperature sintering prevents gases from directly penetrating the electrolyte, forcing oxygen ions to migrate through the conductive path, thereby avoiding electrochemical interference.

[0066] Preferably, the shared counter electrode layer 4 is a Pt thin film structure.

[0067] In an optional embodiment, the Pt film is 25nm thick and acts as a catalyst for the oxygen reduction reaction, reducing the activation energy of the reaction, increasing the reaction rate of the counter electrode, and ensuring the integrity of the electrochemical circuit. The contact resistance between the Pt and YSZ electrolyte interface is <1Ω·cm 2 , reduce energy loss and improve the signal-to-noise ratio of the sensor output signal.

[0068] In another alternative embodiment, a 25 nm thick Pt film was deposited on the surface of the YSZ electrolyte layer using a magnetron sputtering process with a sputtering power of 200 W and a substrate temperature of 300°C. In an accelerated aging test at 85°C / 85% RH, the surface roughness of the Pt film increased by only 0.3 nm after 1000 hours.

[0069] Preferably, the base support layer 5 is an Al2O3 ceramic plate. In this embodiment, the Al2O3 ceramic plate is 1 mm thick and has a three-point bending strength of ≥300 MPa, providing rigid support for the multi-layer stacked structure. A Pt1000 thermistor is embedded in the surface via screen printing. The thermistor is connected to the sensor pins via gold wire bonding, and the signal line is shielded to suppress electromagnetic interference. The temperature term in the Nernst equation is corrected in real time, achieving a NO2 concentration measurement error of <±2%.

[0070] Example 2 is the second embodiment of the present invention, which provides steps for a multi-mode switching strategy, specifically including:

[0071] Apply voltage through the current detection area 22, compare the background current with the voltage, and select to enter low concentration mode, high concentration mode or parallel sampling mode;

[0072] In this embodiment, a constant voltage of 0.5 V was applied to the current detection region (annular Pt electrode) for 10 seconds, and the background current and baseline voltage were measured.

[0073] And the comparison logic is:

[0074] If the background current is <0.1nA and the baseline voltage is <5mV, the output is in standby mode, that is, it wakes up and rescans every 5 minutes;

[0075] If the background current is <0.1nA and the baseline voltage is ≥5mV, the output is low concentration mode;

[0076] If the baseline voltage is ≥5mV and the background current is ≥0.1nA, the output is high concentration mode;

[0077] If the background current and voltage change suddenly at the same time, the parallel sampling mode is used and marked as a “transient event”.

[0078] In low concentration mode, voltage is applied and NO2 concentration is detected by transient current peak;

[0079] In this embodiment, the specific steps are: enable the current detection area, apply a 1Hz pulse voltage with an amplitude of 0.8-1.2V and a pulse width of 100ms, capture the transient current peak through a transimpedance amplifier, and if the result is >8ppm for three consecutive times, switch the trigger mode to the high concentration mode.

[0080] In high concentration mode, the electromotive force is output and NO2 concentration is calculated in combination with temperature compensation;

[0081] Switch to the voltage detection area (circular Au-Pt electrode), disconnect the external bias, measure the open-circuit electromotive force E, and calculate the NO2 partial pressure using the modified Nernst equation based on the real-time temperature T. If the result continues to drop to <10ppm for more than 10 minutes, switch back to low-concentration mode.

[0082] Synchronously acquire voltage and current signals in parallel sampling mode to identify transient discharge events.

[0083] In this embodiment, dual-zone sampling (current detection zone + voltage detection zone) is performed simultaneously, with a sampling rate of up to 10kHz. If the current signal suddenly increases and the voltage is not saturated, it is marked as a partial discharge transient event. If the voltage signal is saturated, the system switches to high-concentration mode and ignores the current signal. The event waveform, for example, lasting 100ms, is stored and uploaded to a host computer via a wireless module for analysis.

[0084] This embodiment achieves full-range NO2 detection from sub-ppm to 1000 ppm through dynamic threshold judgment and dual-signal parallelism, and accurately captures partial discharge transient events. It directly solves the problems of narrow detection range, poor anti-interference and insufficient transient response of traditional methods in the background technology, and provides reliable technical support for early warning of insulation defects in switchgear.

[0085] Example 3, reference Figure 3 , which is a third embodiment of the present invention, provides a method for detecting insulation defects in a dynamically switching NO2 gas sensor, specifically comprising:

[0086] S1. Install the sensor inside the equipment to be tested and monitor the changes in gas concentration in real time.

[0087] In this embodiment, the equipment to be tested includes but is not limited to switchgear. During installation, the sensor probe is embedded inside the top vent of the air-operated switchgear, 10-15 cm away from the insulating components inside the cabinet to ensure an unobstructed gas diffusion path. A high-temperature silicone seal with a temperature resistance of -40°C to 150°C is used, combined with a magnetic base to prevent mechanical vibration interference.

[0088] Pre-install the sensor bracket on the inner wall of the switch cabinet to ensure that the probe is perpendicular to the airflow direction in the cabinet to avoid dust accumulation; after powering on, a self-test process is performed: the electrode impedance is detected. The normal range is set to 10-50Ω in the voltage range and 5-20Ω in the current range. If the limit is exceeded, a fault alarm is triggered.

[0089] In this embodiment, the electrochemical reaction principle is used to detect NO2 gas. Its basic principle and working mode are as follows:

[0090] The sensor uses solid electrochemical principles to convert the chemical energy of NO2 gas into an electrical signal. The sensor contains a solid electrolyte (YSZ) with oxygen ion conductivity sandwiched between the detection electrode and the counter electrode. When NO2 gas contacts the detection electrode surface, the following electrode reaction occurs:

[0091]

[0092] After the detection electrode comes into contact with NO2 gas, NO2 undergoes a partial reduction reaction on the surface of the Pt catalytic electrode, generating NO and releasing oxygen ions (O 2- ); simultaneously, the counter electrode is catalytically reduced using oxygen in the air, absorbing electrons to generate oxygen ions. These two half-reactions are coupled via oxygen ions conducted in the YSZ solid electrolyte, forming a complete electrochemical cell. In summary, NO₂ is reduced (releasing electrons) at the detection electrode, while oxygen is reduced (absorbing electrons) at the counter electrode, causing oxygen ions to migrate between the two electrodes. When the circuit is open, the migration of oxygen ions reaches equilibrium, and the electrochemical potentials on both sides are equal, establishing a stable electromotive force between the electrodes that is logarithmically related to the partial pressure of NO₂ gas.

[0093] S2. Adjust the detection mode through a multi-modal switching strategy to cover the NO2 concentration range of 0.5-1500wt.ppm.

[0094] Importantly, to achieve both a wide measurement range and high sensitivity, the detection system utilizes a multimodal switching strategy to adjust the detection mode. This involves switching or running different detection algorithms and sensor modes in parallel for different concentration ranges. This includes a low-concentration detection mode, a high-concentration detection mode, and a parallel sampling mode combining the two. Amperometric (constant-potential electrolytic) sensors are suitable for accurate detection in low-concentration ranges, while voltage (open-circuit potential) sensors are suitable for wide-range and high-concentration detection. Hybrid sensors combining these two modes can achieve high-precision measurements across the entire measurement range.

[0095] In an optional embodiment, when in low concentration mode, that is, when the NO2 concentration is low, the detection effect is better using constant potential electrolysis. In this mode, the external circuit applies a bias voltage to the two electrodes of the sensor (usually maintaining a fixed potential difference between the electrodes and the detection electrode), forcing the electrode reaction to proceed, thereby generating a current related to the NO2 supply rate. When the NO2 concentration is at the low ppm level, the main limiting factor affecting the total reaction rate is the rate at which NO2 diffuses from the gas phase to the electrode surface. In this diffusion-controlled stage, the reaction current is linearly related to the NO2 concentration. That is, for every increase in a certain concentration of NO2, the number of NO2 molecules diffused to the electrode increases accordingly, resulting in a proportional increase in oxidation / reduction current. The sensor peripheral circuit uses a constant potential meter circuit to maintain the bias voltage and measure the Faraday current passing through the electrode. The magnitude of this current directly indicates the NO2 concentration.

[0096] Because the reaction is driven by external energy, this method offers high sensitivity and fast response at low concentrations, capable of detecting sub-ppm NO2 changes. The measured current is converted to concentration using a calibration factor, with temperature correction applied where necessary. As NO2 concentration increases, diffusion may no longer be the sole limiting factor, leading to a slowdown in current growth and even reaching a limit (sensor current saturation). Therefore, the current-mode output is suitable for concentrations within a certain upper limit; if the threshold is exceeded, the output should switch to voltage.

[0097] In another optional embodiment, when in high-concentration mode, i.e., at relatively high NO2 concentrations or when a wide range needs to be covered, an open-circuit potential detection mode is employed. At this point, no current flows between the sensor electrodes, and the adsorption / reaction of NO2 on the detection electrode reaches equilibrium with the reference electrode, generating a stable potential difference, or electromotive force (E). According to the Nernst relation, E is proportional to the logarithm of the NO2 partial pressure. Therefore, a voltage-output sensor can cover a range of NO2 concentrations over several orders of magnitude, with its output voltage varying logarithmically with concentration. For example, the EMF variation is measurable from tens of ppm to tens of thousands of ppm, and does not saturate as quickly as current does.

[0098] The advantage of voltage-based mode is that it requires no external power supply to maintain the reaction; the sensor passively senses gas concentration, making it suitable for long-term online monitoring. Furthermore, it is more reliable at high concentrations because, even with high NO₂ concentrations, the electrode reaction simply reaches a new equilibrium potential without overloading. However, a disadvantage is that at low concentrations, the signal voltage is very low, making it susceptible to noise and baseline drift. Furthermore, the response time of a voltage-based sensor depends on how quickly electrochemical equilibrium is established. When the NO₂ concentration changes suddenly, the system requires time for diffusion and reaction to stabilize the electrode potential, resulting in a generally slower response than the amperometric method. Therefore, voltage-based mode is more suitable for monitoring steady-state or slowly changing NO₂ concentrations, as well as trends in the medium- to high-concentration range. Voltage-based sensors require the measured electromotive force to be substituted into a precalibrated Nernst curve or formula to calculate the NO₂ concentration, and temperature compensation must be performed.

[0099] In a third alternative embodiment, when using parallel sampling mode, to achieve both sensitivity at low concentrations and a wide measurement range at high concentrations, a hybrid sensor is an optimized solution, achieving both current- and voltage-based detection within the same sensor. The developed hybrid sensor utilizes a dual-detection electrode design: the detection electrode area on one side of the same solid electrolyte sheet is divided into two sections, one for voltage detection and the other for current detection, both sharing the same solid electrolyte and counter electrode. This allows for parallel acquisition of electromotive force and current signals through the corresponding measurement circuits. A larger current detection electrode increases the current signal amplitude, while a smaller voltage detection electrode does not affect potential measurement.

[0100] The switching logic and working status of the three working modes mentioned in switchgear insulation defect detection are as follows:

[0101] S2.1. Apply a constant voltage of 0.5V to the current detection zone and measure the background current. If the background current is <0.1nA and the voltage is <5mV, remain in standby mode. If the background current is <0.1nA and the voltage is >5mV, enter low-concentration mode. If the voltage is >5mV, enter high-concentration mode. If both the background current and voltage change suddenly at the same time, trigger parallel sampling and mark it as a "transient event."

[0102] S2.2. When scanning in low-concentration mode, the annular current detection area is enabled, a pulse voltage (1 Hz, 0.8-1.2 V) is applied, and low-concentration scanning is performed using the transient current peak.

[0103] When scanning in high-concentration mode, it switches to the circular voltage detection area and outputs the electromotive force based on the Nernst equation, while also performing aerodynamic temperature compensation.

[0104] When abnormal peak detection is performed, the two regions are sampled in parallel. If the current region signal suddenly increases and the voltage region is not saturated, it is determined to be a transient discharge event.

[0105] S3. Based on the current or voltage signal output by the sensor and the temperature-compensated Nernst equation, calculate the NO2 partial pressure and correlate it with the partial discharge intensity.

[0106] First, the sensor works based on the Nernst equation, whose basic expression is:

[0107]

[0108] Where, E is the change in electromotive force measured by the sensor; E0 is the reference potential under standard conditions; R is the gas constant; T is the absolute temperature; n is the number of electrons transferred in the electrochemical reaction; F is the Faraday constant; P NO2 is the partial pressure of NO2 gas.

[0109] As can be seen, the RT / F term in the formula is directly proportional to the temperature, T. When the temperature changes, the sensor's output electromotive force will also change, even if the actual partial pressure of the NO2 gas remains unchanged. This temperature dependence can lead to misinterpretation in practical applications. For example, an increase in output voltage with rising temperature could be mistaken for an increase in NO2 concentration.

[0110] In order to eliminate the influence of temperature changes, a Pt1000 thin film resistor (accuracy ±0.3°C) is embedded in the base support layer to monitor the sensor temperature in real time. The measured temperature T is used to replace the temperature term in the Nernst equation to obtain the electromotive force calculation formula under actual working conditions by correcting the temperature term in the Nernst equation:

[0111]

[0112] Based on the E0 of the sensor calibrated at the standard temperature Tref, a temperature deviation term will be introduced when the actual temperature is different from Tref:

[0113]

[0114] This deviation term must be corrected for the change in electromotive force due to temperature changes;

[0115] The measured electromotive force is corrected by real-time calculation:

[0116] E C =E-ΔE;

[0117] Where ΔE is the temperature deviation electromotive force, and Ec is the corrected electromotive force T ref is the reference temperature.

[0118] In one example, when E=0.3V, and T=313K, T ref is 298K, so the corrected temperature deviation electromotive force is expressed as:

[0119]

[0120] Then, combine the calibration curve to infer P NO2 .

[0121] S4. When the NO2 concentration is detected as a transient event, an insulation defect warning is triggered.

[0122] In this embodiment, the insulation defect warning may adopt a concentration threshold warning, which is specifically expressed as:

[0123] In the first level warning, the NO2 concentration is >50ppm, which is a yellow warning, indicating potential insulation degradation;

[0124] During the second-level warning, the NO2 concentration is >100ppm, which is a red alarm and requires immediate maintenance.

[0125] In the event of a single transient event, a log will be recorded and a "partial discharge abnormality" prompt will be displayed; if three events occur consecutively within one hour, an emergency shutdown command will be triggered.

[0126] The transient event determination logic includes: when the signal of the current detection area suddenly increases and the voltage detection area is not saturated, marking it as a partial discharge event, and outputting the partial discharge event as a transient event.

[0127] Example 4 is the fourth embodiment of the present invention, which differs from the first three embodiments in that:

[0128] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0129] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0130] More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0131] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A dynamically switching NO2 gas sensor, characterized by: The invention comprises a gas diffusion layer (1), a detection electrode layer (2), a solid electrolyte layer (3), a shared counter electrode (4), and a base support layer (5) stacked layer by layer. The detection electrode layer (2) includes a voltage detection area (21) and a current detection area (22); The voltage detection area (21) adopts a double-layer electrode; The current detection area (22) adopts a ring electrode; The voltage detection area (21) and the current detection area (22) are isolated by an insulating trench (23); The sensor is configured with a multi-modal switching strategy for switching between a constant potential electrolysis mode and an open circuit potential detection mode by detecting the concentration of the gas.

2. A dynamically switching NO2 gas sensor according to claim 1, characterized in that: The gas diffusion layer (1) is a porous ceramic membrane structure with a pore size of 1-5 μm.

3. The dynamically switching NO2 gas sensor according to claim 2, wherein: The solid electrolyte layer (3) is made of yttrium oxide ceramic material.

4. A dynamically switching NO2 gas sensor according to claim 3, characterized in that: The shared counter electrode layer (4) is a Pt thin film structure.

5. The dynamically switching NO2 gas sensor according to claim 4, wherein: The base support layer (5) is an Al2O3 ceramic plate structure.

6. The dynamically switching NO2 gas sensor according to claim 5, characterized in that: The multi-modal switching strategy includes the following steps: Applying a voltage through the current detection area (22), comparing the background current with the voltage, and selecting to enter a low concentration mode, a high concentration mode, or a parallel sampling mode; In low concentration mode, voltage is applied and NO2 concentration is detected by transient current peak; In high concentration mode, the electromotive force is output and NO2 concentration is calculated in combination with temperature compensation; Synchronously acquire voltage and current signals in parallel sampling mode to identify transient discharge events.

7. A method for detecting insulation defects in a dynamically switching NO2 gas sensor according to any one of claims 1 to 7, characterized in that: The following steps are included: Install the sensor inside the equipment to be tested to monitor the changes in gas concentration in real time; Adjust the detection mode through multimodal switching strategy; Based on the current or voltage signal output by the sensor and the temperature-compensated calculation equation, the NO2 partial pressure is calculated and correlated with the partial discharge intensity. When the NO2 concentration is detected as a transient event, an insulation defect warning is triggered; Wherein, the calculation equation adopts the Nernst equation.

8. The insulation defect detection method according to claim 7, wherein: The decision logic of the transient event includes: When the signal of the current detection area suddenly increases and the voltage detection area is not saturated, it is marked as a partial discharge event and the partial discharge event is output as a transient event.

9. The insulation defect detection method according to claim 8, characterized in that: The calculation equation after temperature compensation is expressed as: Where, E is the change in electromotive force measured by the sensor; E0 is the reference potential under standard conditions; R is the gas constant; T is the absolute temperature; n is the number of electrons transferred in the electrochemical reaction; F is the Faraday constant; P NO2 is the partial pressure of NO2 gas.

10. The insulation defect detection method according to claim 8 or 9, characterized in that: The insulation defect warning includes a hierarchical response logic, specifically, When the NO2 concentration exceeds 50ppm continuously, a yellow warning is triggered; When the NO2 concentration exceeds 100ppm or there are three transient events within one hour, a red alarm is triggered; Record event waveform data, store it on a local SD card, and upload it to a cloud analysis system simultaneously.

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