CN119165007A - Hydrogen detection in-situ sensor chip and preparation method, sensor and self-calibration method - Google Patents
Hydrogen detection in-situ sensor chip and preparation method, sensor and self-calibration method Download PDFInfo
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Abstract
The invention discloses a hydrogen detection in-situ sensing chip in transformer oil, a preparation method, a sensor and a self-calibration method, wherein in a sensing chip element, a heating resistor is laminated on a third insulating layer in a zigzag structure to form a heating area of a uniform thermal physical field, a second insulating layer is laminated on the heating resistor, a plurality of gas sensitive resistors are arranged on the second insulating layer and are positioned in a heating area, the gas sensitive resistors comprise a zigzag structure made of palladium metal alloy materials and gas sensitive lead electrodes connected with the zigzag structure, the zigzag structure is formed into a Wheatstone bridge structure, the temperature measuring resistors are arranged on the second insulating layer and are surrounded in the heating area through the plurality of gas sensitive resistors, the temperature measuring resistors comprise a single wire structure made of platinum materials and temperature measuring lead electrodes arranged at two ends of the single wire structure, a Si3N4 isolation layer covers two opposite bridge arms of the Wheatstone bridge structure, the other two opposite bridge arms are exposed in air, and the gas sensitive resistors output a responsive voltage signal based on hydrogen.
Description
Technical Field
The invention relates to the technical field of hydrogen detection in transformer oil, in particular to an in-situ sensing chip for hydrogen detection in transformer oil, a preparation method, a sensor and a self-calibration method.
Background
During the operation of the transformer, the transformer oil is cracked into gases such as hydrogen, carbon dioxide, methane and the like at high temperature generated by internal electric arcs and the like. The related researchers find that the fault type and the severity of the faults of the transformer have close relations with the types and the concentrations of gases in the transformer oil, wherein the hydrogen in the transformer oil has low generation temperature, wide generation source and linearly-changed concentration, so that the hydrogen is the first choice gas in single gas detection of the gases in the transformer oil. Meanwhile, if multi-gas detection is to be performed on the gas in the transformer oil, hydrogen is also an important gas in the multi-gas detection.
Therefore, the method is one of effective means for ensuring the normal operation of the power system by detecting the hydrogen in the transformer oil and maintaining the transformer according to the detection result. The current detection means for hydrogen in oil is often oil chromatographic analysis and gas separation detection through a matched oil-gas separation device, so that the problems that in-situ measurement cannot be carried out, the matched oil-gas separation device is complex, in-situ self calibration cannot be realized and the like exist, the measurement of the concentration of hydrogen in oil is difficult to be carried out rapidly, in real time and accurately without damaging the environment of the original transformer oil, and the detection requirement of real-time fault analysis of a transformer cannot be met. In the prior art, other hydrogen sensor measurement means in oil have no in-situ self-calibration function, the calibration means is simply combination of a back-end calibration algorithm and a sensor, and the defects that a sensor device is complex, an MEMS (Micro-electro-MECHANICAL SYSTEM) process cannot be compatible, low cost and large-scale manufacturing requirements are difficult to meet, a complex back-end processing circuit is required to obtain the measured hydrogen concentration, the cost is high, the high-volume application is impossible, the combination mode of the back-end calibration algorithm and the sensor is poor in reliability in practical application, and accurate self calibration is difficult to realize in long-term work still exist.
The information disclosed in the background section is only for enhancement of understanding of the background of the invention and therefore may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
Aiming at the defects or drawbacks existing in the prior art, the invention provides an in-situ sensing chip for detecting hydrogen in transformer oil, a preparation method, a sensor and a self-calibration method, wherein the characteristic that a palladium alloy hydrogen sensor can directly measure hydrogen in oil is utilized, and the self-calibration structure and the method are combined to fundamentally solve the problem that the real-time analysis of the running state of the transformer is realized through the detection of the hydrogen concentration in the transformer oil, so that the hydrogen concentration detection precision is improved. The sensor self-calibration mode is utilized in real time in the long-term use process without dismantling the sensor, the baseline correction and the response coefficient correction of the sensor are carried out, the long-term continuous working hydrogen concentration monitoring is realized, the effects of real-time and reliable detection, analysis and early warning of the faults of the transformer are achieved, the problems that the sensor device is complex, the MEMS technology cannot be compatible and cannot be manufactured on a large scale, the back-end processing circuit is complex, the accurate self-calibration is difficult to realize in the long-term working and the like in the existing scheme are overcome,
The aim of the invention is achieved by the following technical scheme.
An in-situ sensing chip for detecting hydrogen in transformer oil comprises,
A silicon substrate having an upper surface and a lower surface;
A first insulating layer laminated on the lower surface;
a third insulating layer laminated on the upper surface;
A heating resistor laminated on the third insulating layer in a zigzag structure to form a heating region of a uniform thermophysical field;
A second insulating layer laminated on the heating resistor;
a plurality of gas-sensitive resistors provided on the second insulating layer and located in the heating region, the gas-sensitive resistors including a polygonal structure made of an alloy material of palladium metal and gas-sensitive lead electrodes connected to the polygonal structure, the polygonal structure being configured as a wheatstone bridge structure,
The temperature measuring resistor is arranged on the second insulating layer and surrounds the second insulating layer in the heating area through a plurality of gas sensitive resistors, and comprises a single-wire structure made of platinum materials and temperature measuring lead electrodes arranged at two ends of the single-wire structure;
and the Si3N4 isolation layer is covered on two opposite bridge arms of the Wheatstone bridge structure, the other two opposite bridge arms are exposed in the air, and the gas-sensitive resistor outputs a responsive voltage signal based on hydrogen.
In the in-situ sensing chip for detecting hydrogen in the transformer oil, a plurality of gas-sensitive resistors are symmetrically distributed by taking the temperature measuring resistor as a center, and the gas-sensitive lead electrode and the temperature measuring lead electrode are both made of gold materials.
In the in-situ sensing chip for detecting hydrogen in the transformer oil, a connecting layer made of Ti material is deposited between the second insulating layer and the gas-sensitive resistor as well as between the second insulating layer and the temperature-measuring resistor.
In the in-situ sensing chip for hydrogen detection in transformer oil, the thickness of the gas-sensitive resistor is 40nm, the thickness of the temperature measuring resistor is 100nm, the thicknesses of the gas-sensitive lead electrode and the temperature measuring lead electrode are 250nm, the thickness of the Si3N4 isolation layer is 250nm, and the thickness of the connecting layer is 20nm-30nm.
In the in-situ sensing chip for hydrogen detection in transformer oil, the first insulating layer and the third insulating layer are sequentially formed by four layers of films of SiO2/Si3N4/SiO2/Si3N 4.
In the in-situ sensing chip for detecting hydrogen in the transformer oil, the heating resistor and the gas-sensitive resistor are arranged in an upper layer and a lower layer through a fold line structure.
The preparation method of the hydrogen detection in-situ sensing chip in the transformer oil comprises the steps of,
Step S1, selecting a 4-inch double-sided polished silicon wafer as a silicon substrate,
Step S2, sequentially preparing a first insulating layer and a third insulating layer of SiO2/Si3N4/SiO2/Si3N4 positioned on the two sides of the silicon substrate by utilizing plasma enhanced chemical vapor deposition,
Step S3, forming a heating resistor with a zigzag structure on one side of the third insulating layer by utilizing magnetron sputtering or electron beam evaporation to deposit gold material,
Step S4, preparing a second insulating layer of SiO2/Si3N4/SiO2/Si3N4 sequentially by utilizing plasma enhanced chemical vapor deposition,
S5, utilizing magnetron sputtering or electron beam evaporation to deposit a plurality of gas sensitive resistors and temperature measuring resistors on the upper side of the second insulating layer, connecting lead electrodes with the gas sensitive resistors and the temperature measuring resistors, distributing the gas sensitive resistors and the temperature measuring resistors in the heating area, positioning the temperature measuring resistor at the most center of the gas sensitive resistors,
S6, preparing Si3N4 isolation layers on two bridge arms opposite to each other by utilizing magnetron sputtering,
And S7, sequentially etching Si3N4/SiO2/Si3N4/SiO2/Si by using a dry etching process, and releasing the silicon-based substrate material below the deposited metal material.
The in-situ self-calibration sensor for detecting hydrogen in transformer oil comprises a hydrogen measuring probe, wherein the hydrogen measuring probe comprises,
A pre-amplifying circuit board integrating the hydrogen detection in-situ sensing chip, the humidity (micro water) sensor and the pressure sensor in the transformer oil to obtain the hydrogen concentration value and the temperature, pressure and humidity analog signals,
And the post-signal processing circuit board is connected with the pre-amplification circuit board and converts the temperature, pressure and humidity analog signals into digital signals by AD analog-to-digital conversion, and the post-signal processing circuit board performs real-time and long-term work self-calibration control on the hydrogen concentration values.
In the in-situ self-calibration sensor for detecting hydrogen in transformer oil, the sensor also comprises,
A front-end probe shell, a front-end probe shell and a front-end probe shell,
An oil inlet which is arranged at the front end of the front end probe shell and is arranged above an oil taking port of the transformer through connecting threads of the transformer,
A middle-end circuit housing connected with the front-end probe housing through a sensor connection thread, a pre-amplification circuit board is arranged in the middle-end circuit housing, a post-signal processing circuit board is connected with the pre-amplification circuit board through a sealing connector,
A signal output circuit board which is arranged in the middle-end circuit shell and is connected with the post-signal processing circuit board through a sealing connector,
The rear end sealing shell is in threaded connection with the middle end circuit shell, and the rear end sealing shell is provided with a signal wire transmission hole for leading out a signal wire.
The self-calibration method of the hydrogen detection in-situ self-calibration sensor in the transformer oil comprises the following steps,
In the hydrogen detection range of the concentration below 200ppm (the hydrogen concentration in transformer oil is generally lower than 80 ppm), the response of the hydrogen detection in-situ self-calibration sensor to the hydrogen concentration is in a linear relation, the expression is Rs (x) =A+Kx, wherein A is called a sensor baseline, K is called a response coefficient of the sensor, the hydrogen concentration is influenced by real-time temperature, humidity and pressure, so that the sensor baseline A and the response coefficient K generate drift respectively called real-time baseline drift a 1 and response coefficient drift K 1, after long-term continuous operation, the gas-sensitive resistor generates drift due to the change of the property of the gas-sensitive resistor, respectively called long-term baseline drift a 2 and response coefficient drift K 2, and the real-time temperature, humidity (micro water) and pressure are measured through the temperature measuring resistor of the hydrogen detection in-situ self-calibration sensor, the integrated humidity (micro water) sensor and the pressure sensor,
In the real-time working process, the self calibration of the real-time baseline drift a 1 and the response coefficient drift k 1 is carried out on the hydrogen concentration value through a compensation model based on temperature, humidity (micro water) and pressure;
After long-term continuous operation, the self-calibration mode can be selected, the hydrogen detection in-situ self-calibration sensor is heated to the temperature required by self calibration (150 ℃ and 60 ℃ for normal operation) through temperature closed-loop control formed by the temperature measurement integrated on the hydrogen detection in-situ self-calibration sensor and a heating resistor, at the temperature, the sensor cannot react with hydrogen in transformer oil, at the moment, the output value is the baseline value of the sensor at the self-calibration temperature, so that the baseline value after long-term operation at the normal operation temperature can be obtained according to the resistance temperature coefficient of the gas-sensitive resistor and the difference value between the self-calibration temperature and the normal operation temperature, the difference value between the baseline value and the baseline value is the baseline drift for long-term operation, and the self calibration of the long-term baseline drift a 2 can be completed according to the difference value;
Further, four temperature points of 60 ℃, 90 ℃, 120 ℃ and 150 ℃ are selected, the obtained self-calibrated baseline value is combined with the gas-sensitive resistance temperature coefficient, the baseline value at the four temperature points can be obtained, meanwhile, the response value of the hydrogen concentration measured at the moment can be directly read out by a sensor, the difference value of the baseline value and the response value is response output at different working temperatures caused by the hydrogen concentration in oil at the moment, the relation between the response output and the working temperature is established, the established relation database between the response output and the working temperature of different concentrations is inquired, the actual hydrogen concentration in the transformer oil in the current environment is obtained, and the self calibration of the long-term working response coefficient drift k 2 can be carried out by utilizing the relation between the actual hydrogen concentration and the response output.
Compared with the prior art, the invention has the beneficial effects that:
1. The sensor has the advantages that the volume of the sensor is greatly reduced through integrating the heating resistor, the temperature measuring resistor and the gas sensitive resistor together, meanwhile, the heating field is more uniform through the layered design of the heating resistor, the response of the gas sensitive resistor and the accurate measurement of the temperature by the temperature measuring resistor are facilitated, the measured signal is in the form of a voltage signal through the Wheatstone bridge structure design of the gas sensitive resistor, compared with the resistance signal, the measured signal is easier to measure, the sensor has high sensitivity, the silicon substrate under a deposited metal material film is released, the sensor can reach the optimal working temperature under the lower working voltage, the power consumption of the sensor is greatly reduced, the insulating layer is in a SiO2/Si3N4/SiO2/Si3N4 four-layer film structure, the film stress matching is more reasonable, the stress concentration film breakage is avoided, the dense Si3N4 film is selected by the two bridge arms of the gas sensitive resistor, and the gas sensitive resistor of the bridge structure outputs a voltage response signal.
2. The hydrogen measuring probe formed by the miniature integrated palladium alloy film hydrogen sensor, the micro water sensor and the pressure sensor has small volume which is not more than 300mm < 3 >, and can directly and real-timely detect the change of the hydrogen concentration in the transformer by directly being arranged on the transformer to be in contact with the transformer oil so as to monitor the running condition in the transformer in real time.
3. The palladium-gold alloy gas-sensitive material has relatively stable performance, can be directly contacted with transformer oil to measure the concentration of hydrogen, does not need an oil-gas separation device, has simple test, can be directly used for in-situ and real-time measurement, and greatly reduces the monitoring cost of the working state of the transformer.
4. By combining long-term working self-calibration with temperature, humidity (micro water) and pressure real-time self-calibration, the excellent stability of long-term working of the sensor is realized, the self-calibration is carried out in real time while continuous working is carried out, the hydrogen measurement precision under long-term continuous working is kept, and the measurement accuracy is ensured.
The description is merely an overview of the technical solutions of the present invention, in order to make the technical means of the present invention more clearly apparent to those skilled in the art, and in order to make the description of the present invention and other objects, features and advantages of the present invention more obvious, the following description of the specific embodiments of the present invention will be exemplified.
Drawings
Various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. It is evident that the figures described below are only some embodiments of the invention, from which other figures can be obtained without inventive effort for a person skilled in the art. Also, like reference numerals are used to designate like parts throughout the figures.
In the drawings:
FIG. 1 is a schematic view of a heating resistor layer of the present invention;
FIG. 2 is a schematic diagram of a gas sensor and temperature sensor layer of the present invention;
FIG. 3 is a schematic cross-sectional view of a sensor chip of the present invention;
FIG. 4 is a flow chart of the chip preparation of the present invention;
FIG. 5 is a schematic flow chart of the self-calibration method of the present invention;
FIG. 6 is a schematic flow chart of a circuit implementation of the present invention;
FIG. 7 is a schematic view of the overall sensor arrangement of the present invention;
FIG. 8 is a schematic diagram of the sensor of the present invention installed on an oil immersed transformer;
In the figure, 1, an AD analog-to-digital converter, 2, MCU, 3, a gas-sensitive resistor, 4, a gas-sensitive lead electrode, 5, a temperature measuring resistor, 6, a temperature measuring lead electrode, 7, a gas-sensitive resistor and a temperature measuring resistor layer, 8, a heating resistor, 9, a Si3N4 isolation layer, 10, a second insulating layer, 11, a third insulating layer, 12, a silicon substrate, 13, a first insulating layer, 14, a substrate release groove, 15, an oil inlet, 16, a transformer connecting thread, 17, a front end probe shell, 18, a sensor connecting thread, 19, a pre-amplifying circuit board, 20, a sealing connector, 21, a middle end circuit shell, 22, a post signal processing circuit board, 23, a signal output circuit board, 24, a back end sealing shell, 25, a signal wire transmission hole, 26, a hydrogen detection in-situ sensor and 27, an oil immersed transformer.
The invention is further explained below with reference to the drawings and examples.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. Those of skill in the art will understand that a person may refer to the same component by different names. The description and claims do not identify differences in terms of components, but rather differences in terms of the functionality of the components. As used throughout the specification and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description hereinafter sets forth a preferred embodiment for practicing the invention, but is not intended to limit the scope of the invention, as the description proceeds with reference to the general principles of the description. The scope of the invention is defined by the appended claims.
For the purpose of facilitating an understanding of the embodiments of the invention, reference will now be made to the drawings of several embodiments illustrated in the drawings, and the accompanying drawings are not to be taken as limiting the embodiments of the invention.
For better understanding, as shown in fig. 1 to 8, a hydrogen detection in-situ sensor chip in transformer oil comprises,
A silicon substrate 12 having an upper surface and a lower surface;
a first insulating layer 13 laminated on the lower surface;
a third insulating layer 11 laminated on the upper surface;
a heating resistor 8 laminated on the third insulating layer 11 in a zigzag structure to form a heating region of a uniform thermal physical field;
a second insulating layer 10 laminated on the heating resistor 8;
a plurality of gas-sensitive resistors 3 provided on the second insulating layer 10 and located in the heating region, the gas-sensitive resistors 3 including a polygonal line structure made of an alloy material of palladium metal and gas-sensitive lead electrodes 4 connected to the polygonal line structure, the polygonal line structure being configured as a wheatstone bridge structure,
The temperature measuring resistor 5 is arranged on the second insulating layer 10 and is surrounded by the plurality of gas sensing resistors 3 in the heating area, and the temperature measuring resistor 5 comprises a single wire structure made of platinum material and temperature measuring lead electrodes 6 arranged at two ends of the single wire structure;
And a Si3N4 isolation layer 9 which is covered on two opposite bridge arms of the Wheatstone bridge structure, the other two opposite bridge arms are exposed in the air, and the gas sensitive resistor 3 outputs a responsive voltage signal based on hydrogen.
In the preferred embodiment of the in-situ sensing chip for detecting hydrogen in transformer oil, a plurality of gas-sensitive resistors 3 are symmetrically distributed by taking a temperature measuring resistor 5 as a center, and the gas-sensitive lead electrode 4 and the temperature measuring lead electrode 6 are both made of gold materials.
In the preferred embodiment of the in-situ sensing chip for hydrogen detection in transformer oil, a connecting layer made of Ti material is deposited between the second insulating layer 10 and the gas-sensitive resistor 3 and between the second insulating layer and the temperature-measuring resistor 5.
In the preferred embodiment of the hydrogen detection in-situ sensing chip in the transformer oil, the thickness of the gas-sensitive resistor 3 is 40nm, the thickness of the temperature measuring resistor 5 is 100nm, the thicknesses of the gas-sensitive lead electrode 4 and the temperature measuring lead electrode 6 are 250nm, the thickness of the Si3N4 isolation layer 9 is 250nm, and the thickness of the connecting layer is 20nm-30nm.
In the preferred embodiment of the in-situ sensing chip for detecting hydrogen in transformer oil, the first insulating layer 13 and the third insulating layer 11 are sequentially composed of four layers of films of SiO2/Si3N4/SiO2/Si3N 4.
In the preferred embodiment of the in-situ sensing chip for detecting hydrogen in transformer oil, the heating resistor 8 and the gas-sensitive resistor 3 are arranged in an upper layer and a lower layer through a folded line type structure.
The preparation method of the hydrogen detection in-situ sensing chip in the transformer oil comprises the steps of,
Step S1, a 4-inch double-sided polished silicon wafer is selected as the silicon substrate 12,
Step S2, sequentially preparing a first insulating layer 13 and a third insulating layer 11 of SiO2/Si3N4/SiO2/Si3N4 positioned on the two sides of the silicon substrate 12 by utilizing plasma enhanced chemical vapor deposition,
Step S3, forming a heating resistor 8 with a zigzag structure on one side of the third insulating layer 11 by utilizing magnetron sputtering or electron beam evaporation to deposit gold material,
Step S4, preparing a second insulating layer 10 of SiO2/Si3N4/SiO2/Si3N4 in sequence by utilizing plasma enhanced chemical vapor deposition,
Step S5, a plurality of gas-sensitive resistors 3 and temperature-measuring resistors 5 are deposited on the upper side of the second insulating layer 10 by utilizing magnetron sputtering or electron beam evaporation, lead electrodes are connected with the gas-sensitive resistors 3 and the temperature-measuring resistors 5, the gas-sensitive resistors 3 and the temperature-measuring resistors 5 are distributed in the heating area, the temperature-measuring resistors 5 are positioned at the most center of the gas-sensitive resistors 3,
Step S6, preparing Si3N4 isolation layers 9 on two bridge arms opposite to the gas-sensitive resistor 3 by utilizing magnetron sputtering,
And S7, sequentially etching Si3N4/SiO2/Si3N4/SiO2/Si by using a dry etching process, and releasing the material of the silicon substrate 12 below the deposited metal material.
The in-situ self-calibration sensor for detecting hydrogen in transformer oil comprises a hydrogen measuring probe, wherein the hydrogen measuring probe comprises,
A pre-amplifying circuit board 19 integrating the hydrogen detection in-situ sensing chip, the micro-water sensor and the pressure sensor in the transformer oil to obtain the hydrogen concentration value and the temperature, pressure and humidity analog signals,
And a post-signal processing circuit board 22 connected with the pre-amplifying circuit board 19 for AD analog-to-digital conversion of the temperature, pressure and humidity analog signals into digital signals, wherein the post-signal processing circuit board 22 performs self-calibration of temperature, pressure and humidity compensation on the hydrogen concentration value.
The hydrogen detection in-situ self-calibration sensor in transformer oil also comprises,
A front-end probe housing 17,
An oil inlet 15 which is arranged at the front end of the front end probe shell 17 and is arranged above an oil taking port of the transformer through a transformer connecting thread 16,
A middle-end circuit housing 21 connected to the front-end probe housing 17 via sensor connection threads 18, a pre-amplification circuit board 19 is provided within the middle-end circuit housing 21, a post-signal processing circuit board 22 is connected to the pre-amplification circuit board 19 via a seal connector 20,
A signal output circuit board 23 provided in the middle-end circuit housing 21 and connected to the post-signal processing circuit board 22 via the sealing connector 20,
And a rear-end sealing housing 24 screwed to the middle-end circuit housing 21, wherein the rear-end sealing housing 24 is provided with a signal line transmission hole 25 for leading out a signal line.
The self-calibration method of the hydrogen detection in-situ self-calibration sensor in the transformer oil comprises the following steps,
In the hydrogen detection range of the concentration below 200ppm (the hydrogen concentration in transformer oil is generally lower than 80 ppm), the response of the hydrogen detection in-situ self-calibration sensor to the hydrogen concentration is in a linear relation, the expression is Rs (x) =A+Kx, wherein A is called a sensor baseline, K is called a response coefficient of the sensor, the hydrogen concentration is influenced by real-time temperature, humidity and pressure, so that the sensor baseline A and the response coefficient K generate drift respectively called real-time baseline drift a1 and response coefficient drift K1, after long-term continuous operation, the gas-sensitive resistor generates drift due to the change of the property of the gas-sensitive resistor, respectively called long-time baseline drift a2 and response coefficient drift K2, and the real-time temperature, humidity and pressure are measured through the temperature measuring resistor of the hydrogen detection in-situ self-calibration sensor, the integrated humidity (micro-water) sensor and the pressure sensor,
In the real-time working process, the self calibration of the real-time baseline drift a1 and the response coefficient drift k1 is carried out on the hydrogen concentration value through a compensation model based on temperature, humidity (micro water) and pressure;
Calibration model of real-time temperature, humidity, pressure:
Real-time baseline drift a 1=KpKtA+Kh.
The real-time response coefficient drifts by K 1= KpKt K.
K p、Kt、Kh is the pressure, temperature, humidity (micro water) calibration coefficient, respectively.
After long-term continuous operation, the self-calibration mode can be selected, the hydrogen detection in-situ self-calibration sensor is heated to the temperature required by self calibration (150 ℃ and 60 ℃ for normal operation) through temperature closed-loop control formed by the temperature measurement integrated on the hydrogen detection in-situ self-calibration sensor and a heating resistor, at the temperature, the sensor cannot react with hydrogen in transformer oil, at the moment, the output value is the baseline value of the sensor at the self-calibration temperature, so that the baseline value after long-term operation at the normal operation temperature can be obtained according to the resistance temperature coefficient of the gas-sensitive resistor and the difference value between the self-calibration temperature and the normal operation temperature, the difference value between the baseline value and the baseline value is the baseline drift for long-term operation, and the self calibration of the long-term baseline drift a2 can be completed according to the difference value;
Further, four temperature points of 60 ℃, 90 ℃, 120 ℃ and 150 ℃ are selected, the obtained self-calibrated baseline value is combined with the gas-sensitive resistance temperature coefficient, the baseline value at the four temperature points can be obtained, meanwhile, the response value of the hydrogen concentration measured at the moment can be directly read out by a sensor, the difference value of the baseline value and the response value is response output at different working temperatures caused by the hydrogen concentration in oil at the moment, the relation between the response output and the working temperature is established, the established relation database between the response output and the working temperature of different concentrations is queried, the actual hydrogen concentration in the transformer oil in the current environment is obtained, and the self calibration of the long-term working response coefficient drift k2 can be carried out by utilizing the relation between the actual hydrogen concentration and the response output.
In one embodiment, as shown in fig. 1, the heating resistor 8 is made of gold material and is designed into a folded line structure, so that a uniform thermophysical field can be formed on the whole heating plane, a second insulating layer 10 is prepared on the heating resistor, so that the heating layer is separated from the gas-sensitive resistor to prevent the conduction failure of the chip, specifically, the thickness of a gold film is selected to be 250nm, and the connecting layer is 50nmCr.
As shown in the schematic diagram of the gas-sensitive resistor and the temperature-measuring resistor layer provided by the embodiment of the invention shown in FIG. 2, the gas-sensitive resistor 3 is made of an alloy material of palladium metal, the temperature-measuring resistor 5 is made of a platinum material, the gas-sensitive lead electrode 4 and the temperature-measuring lead electrode 6 are both made of gold materials, the gas-sensitive material is in a Wheatstone bridge structure, wherein two opposite bridge arms are covered by a compact Si3N4 isolation layer 9, so that a responsive voltage signal can be output when hydrogen is detected, the design of the bridge structure improves the sensitivity of detection, so that the sensor has better response to the concentration of hydrogen at low concentration, the temperature-measuring resistor adopts a single-wire structure and is arranged at the most middle part of the gas-sensitive material, so that the temperature can be measured more accurately, specifically, the gas-sensitive resistor 3 is a film with the thickness of 40nm, the connecting layer is 20nmTi is a film with the thickness of 100nm, the connecting layer is 30nmTi, the film thickness of the gas-sensitive lead electrode is 250nm, the connecting layer is 50 nCr, and the thickness of the compact Si3N4 isolation layer is 250nm.
The schematic cross section of the sensor chip provided by the embodiment of the invention shown in fig. 3 is shown as a schematic cross section of the sensor chip, which is composed of a first insulating layer 13, a silicon substrate 12, a third insulating layer 11, a heating resistor 8, a second insulating layer 10, a gas-sensitive resistor and temperature-measuring resistor layer 7 and a Si3N4 insulating layer 9 from bottom to top, and has good film stress matching characteristics, so that the stability of the film is improved, the release of a substrate material is completed through an ICP etching process, so that the sensor can reach a higher temperature under a lower heating voltage to realize the preparation of an ultralow-power consumption sensor, specifically, the ICP etching process is repeatedly realized through 11 times of cyclic etching, the former four times of etching of SiO2/Si3N4/SiO2/Si3N4 films are respectively, each time of etching of 80nm silicon is performed in a5 th to 10 th times of cycle, and the 11 th time of the release of all silicon substrates is completed according to reasonable parameters selected according to the previous etching conditions.
As shown in fig. 4, the chip preparation flow chart provided by the embodiment of the invention selects a 4-inch double-sided polished silicon chip as a substrate, sequentially prepares a first insulating layer 13 and a third insulating layer 11 of a double-sided SiO2/Si3N4/SiO2/Si3N4 film by using plasma enhanced chemical vapor deposition, sequentially prepares a second insulating layer 10 of the SiO2/Si3N4/SiO2/Si3N4 film by using magnetron sputtering or electron beam evaporation deposition heating resistance material on one side of the third insulating layer 11, and (3) depositing a gas-sensitive resistor, a temperature-measuring resistor material and a lead electrode material on the upper side of the second insulating layer 10 by utilizing magnetron sputtering or electron beam evaporation, wherein the lead electrode is connected with the gas-sensitive resistor and the temperature-measuring resistor, the gas-sensitive resistor and the temperature-measuring resistor are distributed in a heating area, the temperature-measuring resistor is positioned at the most center of the gas-sensitive resistor, a compact Si3N4 isolation layer of a film is prepared on two bridge arms opposite to the gas-sensitive material by utilizing magnetron sputtering, finally, etching Si3N4/SiO2/Si3N4/SiO2/Si is sequentially carried out by utilizing a dry etching process, a silicon-based substrate material below the deposited metal material is released, and further, a substrate release groove 14 is arranged below the silicon-based substrate 12.
FIG. 5 is a schematic flow chart of a self-calibration method provided by the embodiment of the invention. The self calibration of the base line and the response coefficient can be completed directly through a preset compensation model by temperature, humidity (micro water) and pressure, and a long-term self calibration working mode is mainly described herein.
In the low concentration hydrogen detection range (200 ppm or less), the response of the sensor to the hydrogen concentration can be regarded as approximately linear, and the expression is:
Rs(x)=A+Kx
wherein A is called a sensor baseline, K is called a response coefficient of the sensor, the hydrogen concentration is influenced by real-time temperature, humidity and pressure, so that the sensor baseline A and the response coefficient K drift, respectively called real-time baseline drift a 1 and response coefficient drift K 1, after long-term continuous operation, the gas-sensitive resistor generates drift due to the change of the property of the gas-sensitive resistor, respectively called long-term baseline drift a 2 and response coefficient drift K 2, the temperature measuring resistor of the in-situ self-calibration sensor and the integrated humidity (micro water) sensor and pressure sensor are used for measuring the real-time temperature, humidity and pressure through hydrogen detection,
In the real-time working process, the self calibration of the real-time baseline drift a 1 and the response coefficient drift k 1 is carried out on the hydrogen concentration value through a compensation model based on temperature, humidity and pressure;
after long-term continuous operation, the self-calibration mode can be selectively entered, the hydrogen detection in-situ self-calibration sensor is heated to the temperature required by self calibration (150 ℃, the normal operating temperature is 60 ℃) through temperature closed-loop control formed by the temperature measurement integrated on the hydrogen detection in-situ self-calibration sensor and the heating resistor, at the temperature, the sensor cannot react with hydrogen in transformer oil, at the moment, the output value is the baseline value of the sensor at the self-calibration temperature, the baseline value after long-term operation at the normal operating temperature can be obtained according to the resistance temperature coefficient of the gas-sensitive resistor and the difference value between the self-calibration temperature and the normal operating temperature, the difference value between the baseline value and the baseline value during initial operation is the baseline drift of long-term operation, the self-calibration of the long-term baseline drift a 2 can be completed according to the difference value, further, the baseline value after the self-calibration at the temperature is obtained is 60 ℃, the temperature coefficient of the temperature is combined with the hydrogen, the baseline value under the four temperature points can be obtained, at the moment, the sensor can directly read out the baseline value after the self-calibration, the temperature coefficient is combined with the temperature coefficient, the actual concentration of the hydrogen is different from the temperature coefficient, the response is different from the actual concentration of the hydrogen, the temperature coefficient, the response is not found out, and the current concentration is different from the temperature coefficient of the sensor, the temperature is in response is found, and the temperature, the response is different from the temperature, and the temperature is in the temperature-dependent on the temperature, and the temperature of the temperature.
Specifically, the normal working temperature of the transformer is set to be 60 ℃, the high-temperature heating temperature in the self-calibration mode is set to be 150 ℃, the short time of self-calibration heating is set to be 10s, the self-calibration interval is set to be 30 days, the influence on transformer oil is reduced as much as possible, and the transformer oil can be changed according to the actual measurement condition.
A hardware flow diagram of an implementation of the self-calibration method provided by the example of the present invention as shown in fig. 6. Specifically, an ARM microcontroller STM32F407VET6 is adopted to form a signal acquisition, processing, storage and communication system, so that the driving, signal pre-amplification and acquisition of a hydrogen sensor, a humidity (micro water) sensor and a pressure sensor can be realized, the sensor data is stored in flash for at least 30 days, and the sensor data is transmitted to a monitoring base station (upper computer) in a mode of combining RS-485 wired communication and Bluetooth wireless communication. The signal acquisition and processing circuit board is divided into a pre-amplifying board and a conversion communication circuit board due to the actual requirement that the sensor is installed in the transformer bushing. The pre-amplification circuit board is directly immersed in transformer oil, and the conversion communication circuit board is positioned on the outer side.
The schematic diagram of the sensor integrated device provided by the embodiment of the invention is shown in fig. 7, an oil inlet 15 is directly arranged above an oil taking port of a transformer through a connecting thread 16 of the transformer, a front-end probe shell is connected with a middle-end circuit shell 21 through a connecting thread 18 of the sensor, a pre-amplifying circuit board 19 is integrated with a hydrogen sensor, a humidity (micro water) sensor and a pressure sensor, and is connected with a post-signal processing circuit board 22 and a signal output circuit board 23 through a sealing connector 20, so that ultra-high tightness is realized, transformer oil leakage is avoided, and the middle-end circuit shell 21 is connected with a rear-end sealing shell 24 through threads. The signal line is led out through the signal line transmission hole 25. Specifically, all connecting threads are pipe threads with tightness, the sealing connector is selected to be 12-channel connection, and the circuit board adopts electromagnetic protection design.
The example of the invention shown in fig. 8 provides a schematic diagram of the sensor installed on an oil-immersed transformer, and the hydrogen gas detection in-situ self-calibration sensor 26 is directly installed on the oil-immersed transformer 27. Specifically, the installation position of the hydrogen detection in-situ self-calibration sensor is an oil taking port of the transformer.
In one embodiment, the sensor substrate is preferably selected to be a silicon substrate covered with a silicon oxide insulating layer. Preferably, the third insulating layer and the first insulating layer are respectively distributed on the upper surface and the lower surface of the substrate, and sequentially comprise four layers of films of SiO2/Si3N4/SiO2/Si3N 4. The integrated palladium alloy bridge film hydrogen sensor is integrated with a heating resistor, a temperature measuring resistor and a gas sensitive resistor, wherein the heating resistor and the gas sensitive resistor are respectively arranged in an upper layer and a lower layer through a fold line structure, and the temperature measuring resistor is arranged at the most center of an upper layer gas sensitive material structure.
Preferably, a second insulating layer is prepared between the heating resistor and the temperature measuring resistor and between the heating resistor and the gas sensitive resistor, and the second insulating layer sequentially consists of four layers of films of SiO2/Si3N4/SiO2/Si3N 4. Preferably, the thermistor is made of Pt material, the thermal resistor is made of Au material, and the sensitive resistor is made of palladium metal alloy material.
Preferably, a connection layer of Ti material that increases adhesion between the electrode and the insulating layer is deposited between and among the thermistor Pt material, the heating resistor Au material, and the sensing resistor palladium metal alloy material and the insulating layer.
Preferably, the gas-sensitive resistor is designed into a Wheatstone bridge structure, two opposite bridge arms of the gas-sensitive resistor are deposited with a layer of compact Si3N4 film through magnetron sputtering, and the other two opposite bridge arms are exposed in the air. And releasing the silicon substrate material below the deposited metal material through a dry etching process to form a suspended film structure. The volume of the hydrogen measuring probe consisting of the integrated palladium alloy film hydrogen sensor, the humidity (micro water) sensor and the pressure sensor which are connected on the printed circuit board is not more than 300mm 3.
In one embodiment, the hydrogen gas detection in-situ self-calibrating detection method comprises:
The method comprises the steps of carrying out closed loop control on gradient working temperature by using a heating resistor and a temperature measuring resistor, wherein low-concentration hydrogen (below 200 ppm) cannot react with a sensor at self-calibration temperature, so that a sensor baseline after long-term working at high temperature can be obtained, a baseline value after long-term working at normal working temperature can be obtained according to a resistance temperature coefficient of the gas-sensitive resistor and a difference value between the self-calibration temperature and normal working temperature, the difference value between the baseline value and the baseline value at initial working temperature is the baseline drift of long-term working, self calibration of the long-term baseline drift a2 can be completed according to the difference value, further, four temperature points of 60 ℃, 90 ℃, 120 ℃ and 150 ℃ are selected, the obtained baseline value after self-calibration is combined with a gas-sensitive resistor temperature coefficient, the baseline value at the four temperature points can be obtained, meanwhile, the response value of the hydrogen concentration measured at the moment can be directly read by the sensor, the difference value is the response output at different working temperatures caused by the hydrogen concentration in oil at the moment, the time, the response output of transformer oil at the different working temperatures is established, the response output of the hydrogen concentration and the transformer oil at different working temperatures, the actual working temperatures can be obtained by using the response coefficients of the hydrogen concentration in the current temperature drift, and the current environment, and the response relation of the hydrogen concentration and the hydrogen concentration can be output by the actual environment with the temperature drift, and the current temperature. And (3) the self calibration of the long-term working response coefficient of the sensor is completed at two points of the baseline value of zero concentration after the long-term working baseline drift correction at the working temperature and the response value of hydrogen standard concentration.
The integrated palladium alloy bridge film hydrogen sensor, the humidity (micro water) sensor and the pressure sensor are connected to a post signal processing and outputting circuit through a pre signal amplifying circuit board connecting wire, compensation self-calibration of temperature, pressure and humidity is directly carried out according to a preset model, baseline drift and response coefficient change of the hydrogen sensor caused by temperature, pressure and humidity change in the transformer are eliminated, and self-calibration of the humidity, pressure and humidity baseline and response coefficient is completed. The method comprises the following steps of connecting a micro palladium alloy film hydrogen sensor, a humidity (micro water) sensor and a pressure sensor to a voltage dividing circuit, reading out resistance values, outputting voltage signals of hydrogen concentration, humidity (micro water) change and pressure change of transformer oil in a transformer by the voltage dividing circuit, amplifying the voltage signals by an amplifying and filtering circuit, converting conditioned temperature, hydrogen concentration, humidity (micro water) content and pressure analog signals into digital signals by an AD analog-to-digital converter 1, and carrying out self calibration of temperature, humidity, pressure and long-term working drift on the hydrogen concentration signals by an MCU2 by adopting a preset compensation model to obtain accurate concentration values of hydrogen in the transformer.
In one embodiment, the pre-amp circuit board 19 is electromagnetically shielded from the post-signal processing circuit board 22. The post-signal processing circuit board 22 is provided with an AD analog-to-digital converter 1 and an MCU2, the AD analog-to-digital converter 1 converts the conditioned temperature, hydrogen concentration, humidity (micro water) content and pressure analog signals into digital signals, and the MCU2 adopts a preset compensation model to self-calibrate the hydrogen concentration signals for temperature, humidity, pressure and long-term working drift, so that the accurate concentration value of the hydrogen in the transformer is obtained.
The basic principles of the present application have been described above in connection with specific embodiments, but it should be noted that the advantages, benefits, effects, etc. mentioned in the present application are merely examples and not intended to be limiting, and these advantages, benefits, effects, etc. are not to be construed as necessarily possessed by the various embodiments of the application. Furthermore, the specific details disclosed herein are for purposes of illustration and understanding only, and are not intended to be limiting, as the application is not necessarily limited to practice with the above described specific details.
The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the application to the form disclosed herein. Although a number of example aspects and embodiments have been discussed above, a person of ordinary skill in the art will recognize certain variations, modifications, alterations, additions, and subcombinations thereof.
Claims (8)
1. The in-situ sensing chip for detecting hydrogen in transformer oil is characterized by comprising,
A silicon substrate having an upper surface and a lower surface;
A first insulating layer laminated on the lower surface;
a third insulating layer laminated on the upper surface;
A heating resistor laminated on the third insulating layer in a zigzag structure to form a heating region of a uniform thermophysical field;
A second insulating layer laminated on the heating resistor;
a plurality of gas-sensitive resistors provided on the second insulating layer and located in the heating region, the gas-sensitive resistors including a polygonal structure made of an alloy material of palladium metal and gas-sensitive lead electrodes connected to the polygonal structure, the polygonal structure being configured as a wheatstone bridge structure,
The temperature measuring resistor is arranged on the second insulating layer and surrounds the second insulating layer in the heating area through a plurality of gas sensitive resistors, and comprises a single-wire structure made of platinum materials and temperature measuring lead electrodes arranged at two ends of the single-wire structure;
and the Si3N4 isolation layer is covered on two opposite bridge arms of the Wheatstone bridge structure, the other two opposite bridge arms are exposed in the air, and the gas-sensitive resistor outputs a responsive voltage signal based on hydrogen.
2. The in-situ sensing chip for hydrogen detection in transformer oil according to claim 1, wherein the plurality of gas-sensitive resistors are preferably symmetrically distributed with respect to the temperature measuring resistor as a center, and the gas-sensitive lead electrode and the temperature measuring lead electrode are both made of gold material.
3. The in-situ sensing chip for hydrogen detection in transformer oil of claim 1, wherein a connecting layer made of Ti material is deposited between the second insulating layer and each of the gas-sensitive resistor and the temperature-measuring resistor.
4. The in-situ sensing chip for hydrogen detection in transformer oil according to claim 1, wherein the thickness of the gas-sensitive resistor is 40nm, the thickness of the temperature measuring resistor is 100nm, the thicknesses of the gas-sensitive lead electrode and the temperature measuring lead electrode are 250nm, the thickness of the Si3N4 isolation layer is 250nm, and the thickness of the connecting layer is 20nm-30nm.
5. The in-situ sensing chip for hydrogen detection in transformer oil of claim 1, wherein the first insulating layer and the third insulating layer are sequentially composed of four films of SiO 2/Si3N4/SiO2/Si3N4.
6. The in-situ sensing chip for hydrogen detection in transformer oil according to claim 1, wherein the heating resistor and the gas-sensitive resistor are arranged in an upper layer and a lower layer through a zigzag structure.
7. The in-situ self-calibration sensor for detecting hydrogen in transformer oil is characterized by comprising a hydrogen measuring probe, wherein the hydrogen measuring probe comprises,
A pre-amplifying circuit board integrating the hydrogen detection in-situ sensor chip, the humidity sensor and the pressure sensor in the transformer oil according to any one of claims 1-6 to obtain hydrogen concentration value and temperature, pressure and humidity analog signals,
And the post-signal processing circuit board is connected with the pre-amplification circuit board to convert the temperature, pressure and humidity analog signals into digital signals by AD analog-to-digital conversion, and the post-signal processing circuit board carries out self-calibration of temperature, pressure and humidity compensation on the hydrogen concentration value.
8. The hydrogen detection in-situ self-calibrating sensor in transformer oil of claim 7, further comprising,
A front-end probe shell, a front-end probe shell and a front-end probe shell,
An oil inlet which is arranged at the front end of the front end probe shell and is arranged above an oil taking port of the transformer through connecting threads of the transformer,
A middle-end circuit housing connected with the front-end probe housing through a sensor connection thread, a pre-amplification circuit board is arranged in the middle-end circuit housing, a post-signal processing circuit board is connected with the pre-amplification circuit board through a sealing connector,
A signal output circuit board which is arranged in the middle-end circuit shell and is connected with the post-signal processing circuit board through a sealing connector,
The rear end sealing shell is in threaded connection with the middle end circuit shell, and the rear end sealing shell is provided with a signal wire transmission hole for leading out a signal wire.
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| CN202411136594.9A CN119165007A (en) | 2024-08-19 | 2024-08-19 | Hydrogen detection in-situ sensor chip and preparation method, sensor and self-calibration method |
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