CN102768183B - System and method for online monitoring filth of fiber bragg grating transmission line - Google Patents

Abstract

The invention discloses an on-line pollution monitoring system of an optical fiber Bragg grating transmission line in the technical field of on-line monitoring of power lines. The invention includes a computer, a wavelength demodulation system, a junction box, an output optical cable of the junction box, a shutter box, a first lead-out optical fiber, a second lead-out optical fiber, an optical fiber Bragg grating pollution sensor array and an optical fiber Bragg grating compensation sensor; The dispatching system includes a solar power generation module and a wireless communication module. The accurate salt density and gray density measurement of this system is suitable for use in the strong electromagnetic environment and harsh temperature and humidity environment where insulators are located.

Description

An online monitoring system and method for contamination of transmission lines with optical fiber Bragg gratings

technical field

The invention belongs to the technical field of on-line monitoring of power lines, and in particular relates to an on-line monitoring system and method for contamination of optical fiber Bragg grating transmission lines.

Background technique

Since the 1990s, large-scale pollution flashover accidents in power grids have occurred frequently across the country, seriously threatening the safe operation of the power system. The root cause of pollution flashover accidents on transmission lines is that dirty substances are deposited on the surface of the insulator. When it absorbs the moisture in the humid air, the dielectric strength drops sharply, and flashover occurs due to the inability to withstand the working voltage. Reliable detection of pollution level of insulators is helpful for power maintenance personnel to grasp the pollution status of insulators in a timely and accurate manner, which is a very important part of anti-pollution flashover work. At the same time, reliable pollution degree detection can ensure the accurate division of pollution areas, thereby providing a scientific basis for the design of external insulation of power transmission and transformation equipment and the selection of insulators, which is the basic guarantee for preventing large-scale pollution flashover accidents.

Online monitoring can effectively track the change process of insulator pollution, so that it can give early warning when the pollution level reaches a critical state, so that electric power workers can take early countermeasures to prevent pollution flashover accidents. Many domestic experts and scholars from Tsinghua University, China Electric Power Research Institute, Chongqing University, North China Electric Power University, Xi'an Jiaotong University, South China University of Technology, Harbin University of Science and Technology, and many universities and research institutions have carried out a lot of fruitful work in this field. , and developed a large number of online detection devices. At present, the means and methods of pollution detection of high-voltage insulators at home and abroad include: microwave radiation method, ultraviolet pulse method, infrared imaging method, acoustic emission method, leakage current method and light intensity method. Microwave radiation method, due to the complex pollution components, the measurement results are difficult to correspond to the pollution components; ultraviolet and infrared methods, due to the high price of optical measurement equipment such as ultraviolet and infrared, are easily damaged and require high power consumption, they are not suitable for long-term on-line monitoring; With the acoustic emission method, due to the harsh electromagnetic environment near the power transmission and the high noise, the received signal of the acoustic emission method is easily submerged, and it is difficult to obtain the real pollution situation. Leakage current method and spectroscopic method are widely used in the field.

Leakage current is the result of the comprehensive action of the three elements of operating voltage, pollution degree, and climate conditions. It is a dynamic parameter and is suitable for online monitoring. The leakage current flowing through the surface of the insulator is obtained in real time by the leakage current sensor, and a large number of on-line monitoring systems for transmission line insulator pollution are formed. A large number of experimental studies by the research group of Professor Guan Zhicheng of Tsinghua University have shown that: for the type of insulator studied, the relationship between the maximum leakage current and the pollution state is obvious, which can be used to evaluate the pollution degree.

The research on leakage current on-line monitoring technology has been carried out for many years, but there are still many problems in practical application. The main problems are: 1) The size of the leakage current is related to various factors such as the type of insulator used (material, umbrella type, disk diameter), pollution composition, equivalent salt density (ESDD), dust density, weather conditions, etc., so it is difficult to use Leakage current assesses the pollution level of insulators; 2) Judging the operating status and early warning interval of insulators based on leakage current, there is no authoritative standard to follow, and there is not enough operating data accumulated, and the cleaning or maintenance must be determined based on the experience of the operator Critical value, its accuracy is not high; 3) The operating environment of the device is relatively harsh, and the reliability is not high; 4) Since the measurement system is not specially designed for the environment near the outdoor transmission line, there are disadvantages such as being susceptible to electromagnetic interference and fast aging .

The light intensity method successfully solves the shortcomings of the leakage current method that cannot directly measure the amount of pollution and has weak anti-electromagnetic interference ability. Its theoretical basis is the light field distribution theory and the light energy loss mechanism in the dielectric optical waveguide. When there is pollution on the quartz glass rod, the transmission conditions of the high-order mode and the fundamental mode are changed by the pollutants, and at the same time, the absorption and scattering of light energy by the pollution particles will cause light energy loss, which can be calculated by detecting the light energy parameters The amount of salt on the surface of the sensor. Some scholars have tried to establish the relationship between luminous flux, humidity, dust ratio and ESDD through neural network, but due to the small number of samples, the research is not sufficient.

The spectroscopic salt density on-line monitoring system has been put into operation in some areas of northern my country in recent years, but the system has not yet been promoted and used in various power companies, mainly because the accuracy of the equivalent salt density measurement needs to be verified, and light intensity measurement exists The fatal shortcoming is that due to the use of light intensity as the monitoring quantity, the unstable factors of optical components have a great influence on the measurement results. At the same time, the system cannot directly measure the dust density, and the relationship between luminous flux attenuation and humidity, dust ratio and ESDD needs to be further studied.

Contents of the invention

In view of the shortcomings mentioned in the above background technology that the existing on-line monitoring system cannot measure dust density and the measurement results are easily disturbed, the present invention proposes an on-line monitoring system and method for contamination of fiber Bragg grating transmission lines.

The technical solution of the present invention is an on-line monitoring system for contamination of optical fiber Bragg grating transmission lines, which is characterized in that the system includes a computer, a wavelength demodulation system, a junction box, an output optical cable of the junction box, a shutter box, a first lead-out optical fiber, The second lead-out optical fiber, fiber Bragg grating pollution sensor array and fiber Bragg grating compensation sensor;

The wavelength demodulation system includes a solar power generation module and a wireless communication module;

The computer is connected to the wavelength demodulation system; the wavelength demodulation system is connected to the junction box through the output optical cable of the junction box; Connect to the grating compensation sensor; the optical fiber Bragg grating compensation sensor is placed in the shutter box;

The fiber Bragg grating pollution sensor array is composed of a first fiber Bragg grating pollution sensor and a second fiber Bragg grating pollution sensor, and the first fiber Bragg grating pollution sensor is coated with a first set thickness wet The fiber Bragg grating of sensitive material; The second fiber Bragg grating pollution sensor is the fiber Bragg grating of coating the second setting thickness moisture sensitive material;

Half of the optical fiber Bragg grating compensation sensor is an optical fiber Bragg grating coated with a moisture-sensitive material with a third set thickness, and the other half of the optical fiber Bragg grating compensation sensor is an optical fiber Bragg grating that is not coated with a moisture-sensitive material. The fiber Bragg grating compensation sensor is equipped with a moisture-permeable and dust-proof sheath;

The wavelength demodulation system is used to demodulate the wavelength collected by the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor;

The computer uses the wavelength data to calculate and obtain salt density and gray density.

The output optical cable of the junction box is an optical fiber composite overhead ground wire OPGW, an all-dielectric self-supporting optical cable ADSS, an OPPC optical cable or an armored optical cable.

The first fiber Bragg grating pollution sensor and the second fiber Bragg grating pollution sensor are connected in series or in parallel.

The moisture-sensitive material is polyimide or hydrogel.

The computer and the wavelength demodulation system are connected through a network cable or a wireless communication module.

When the computer and the wavelength demodulation system are connected through a network cable, the wavelength demodulation system is powered by commercial power.

When the computer and the wavelength demodulation system are connected through the wireless communication module, the wavelength demodulation system is powered by the solar power generation module.

A method for on-line monitoring of transmission line contamination is characterized in that the method includes the following steps:

Step 1: placing the junction box, the shutter box, the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor at a designated position on the transmission line;

Step 2: Send the data collected by the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor to the wavelength demodulation system through the junction box;

Step 3: the wavelength demodulation system sends the demodulated Bragg wavelength data to the computer;

Step 4: The computer calculates salt density and gray density according to the demodulated Bragg wavelength data.

The calculation formula of the fiber Bragg grating compensation sensor temperature and humidity is:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right.$

λ ₃ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is coated with the moisture-sensitive material part;

λ ₄ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is not coated with the moisture-sensitive material part;

α _T3 is the sensitivity coefficient of Bragg wavelength to temperature obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor;

α _T4 is the sensitivity coefficient of the Bragg wavelength to temperature obtained from the part of the fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials;

α _H3 is the sensitivity coefficient of the Bragg wavelength to humidity obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor;

α _H4 is the sensitivity coefficient of the Bragg wavelength to humidity obtained from the part of the optical fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials;

T is the temperature;

H is humidity.

The formulas for calculating salt density and gray density are:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\end{array}\right.$

in:

λ ₁ is the Bragg wavelength of the first fiber Bragg grating contamination sensor;

λ ₂ is the Bragg wavelength of the second fiber Bragg grating contamination sensor;

α _T1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to temperature;

α _T2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to temperature;

α _H1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to humidity;

α _H2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to humidity;

α _S1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to salinity;

α _S2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to salinity;

α _A1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to the gray scale;

α _A2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to the gray scale;

S is salinity;

A is grayscale.

The invention solves the disadvantages of poor accuracy and incapable of accurate salt and gray density measurement in the prior art. The system has many advantages such as anti-electromagnetic interference, stable performance, long monitoring distance, and not affected by light intensity. It is especially suitable for use in strong electromagnetic environments and harsh temperature and humidity environments where insulators are located.

Description of drawings

Figure 1 is a schematic diagram of a fiber Bragg grating pollution sensor;

Figure 2 is the site layout of the fiber Bragg grating pollution sensor;

Figure 3 is part of the data in the database of "humidity-sensitive coating thickness-humidity-salt density-gray density-redshift amplitude-redshift response time".

Detailed ways

The preferred embodiments will be described in detail below in conjunction with the accompanying drawings. It should be emphasized that the following description is only exemplary and not intended to limit the scope of the invention and its application.

In order to overcome the above-mentioned problems existing in the prior art, the present invention adopts the fiber Bragg grating (FBG) to carry out the on-line monitoring of the insulator contamination of the transmission line. Because FBG has many advantages such as anti-electromagnetic interference, stable performance, long monitoring distance, and not affected by light intensity, it is especially suitable for use in strong electromagnetic environments and harsh temperature and humidity environments where insulators are located. However, since the characteristic Bragg wavelength of FBG is only sensitive to temperature and strain, there is currently no way to directly use fiber Bragg grating FBG to measure the salt or ash content of pollution.

There are two ways to install the wavelength demodulation system in the tower and in the substation. When the wavelength demodulation system is located on the tower, the wavelength demodulation system is connected to the computer through wireless. Connect to computer wirelessly. The wavelength demodulation system sends the output wavelength signal to the computer, and the computer uses the wavelength data to calculate the salt density and gray density according to the built-in algorithm.

The principle of the fiber Bragg grating pollution sensor is that salt or ash will inhibit the water absorption and water absorption speed of the moisture-sensitive material on the surface of the fiber Bragg grating, and reflect the salt density and dust density by monitoring the wavelength of the fiber Bragg grating sensor.

The invention includes a computer, a wavelength demodulation system, a junction box, an output optical cable of the junction box, a shutter box, a first lead-out optical fiber, a second lead-out optical fiber, an optical fiber Bragg grating pollution sensor array and an optical fiber Bragg grating compensation sensor; The modulation system includes a solar power generation module and a wireless communication module; the computer is connected to the wavelength demodulation system; the wavelength demodulation system is connected to the junction box through the output optical cable of the junction box; The fiber Bragg grating pollution sensor array is connected with the fiber Bragg grating compensation sensor; the fiber Bragg grating compensation sensor is placed in the shutter box; the fiber Bragg grating pollution sensor array is composed of the first fiber Bragg grating pollution sensor and the second optical fiber Composed of Bragg grating pollution sensors, the first fiber Bragg grating pollution sensor is a fiber Bragg grating coated with a moisture-sensitive material with a first set thickness; the second fiber Bragg grating pollution sensor is coated with a second device Fiber Bragg grating for moisture-sensitive material with a fixed thickness; half of the fiber-optic Bragg grating compensation sensor is the fiber-optic Bragg grating coated with the moisture-sensitive material with the third set thickness, and the other half of the fiber-optic Bragg grating compensation sensor is Fiber Bragg gratings without moisture-sensitive materials, and fiber Bragg grating compensation sensors are equipped with moisture-permeable and dust-proof sheaths; wavelength demodulation systems are used for fiber Bragg grating pollution sensor arrays and fiber The wavelength collected by the grating compensation sensor is demodulated; the computer uses the wavelength data to calculate the salt density and ash density.

The output optical cable of the junction box is optical fiber composite overhead ground wire OPGW, all-dielectric self-supporting optical cable ADSS or OPPC optical cable; the connection mode of the first optical fiber Bragg grating pollution sensor and the second optical fiber Bragg grating pollution sensor is series or parallel; The moisture-sensitive material is polyimide or hydrogel; the computer and the wavelength demodulation system are connected through a network cable or a wireless communication module; when the computer and the wavelength demodulation system are connected through a network cable, the wavelength demodulation system is powered by the mains; When the demodulation system is connected through the wireless communication module, the wavelength demodulation system is powered by the solar power generation module.

The Bragg wavelengths of the first fiber Bragg grating pollution sensor and the second fiber Bragg grating pollution sensor are different in sensitivity to salt density and dust density in pollution;

The fiber Bragg grating pollution sensor is a fiber Bragg grating coated with moisture-sensitive materials. The factors affecting the sensor Bragg wavelength include humidity, temperature, salt and ash.

The Bragg wavelength of the optical fiber Bragg grating compensation sensor redshifts with the increase of humidity, and the magnitude of the redshift increases with the increase of humidity and temperature.

Fiber Bragg Grating Contamination Sensor

1) In the absence of pollution, the magnitude of the redshift of the Bragg wavelength increases with the increase of humidity and temperature.

2) There is pollution, pollution includes two kinds of salt and ash

With the increase of temperature and humidity, the Bragg wavelength of the fiber Bragg grating pollution sensor will be red-shifted.

As the salt content increases, the Bragg wavelength redshift of the fiber Bragg grating pollution sensor decreases. Response time variation is negligible.

As the ash content increases, the Bragg wavelength redshift of the fiber Bragg grating pollution sensor decreases, and the response time increases.

Salt density is the result of dividing the amount of salt deposited on a given surface of an insulator (metal parts and cemented materials are not included in this surface) by the area of that surface.

Ash density refers to the result of dividing the water-insoluble substances deposited on a given surface of an insulator (metal parts and cemented materials are not included in this surface) divided by the surface area.

Salt and ash caused by fiber Bragg grating pollution sensors have different reductions in the wavelength red shift, and the response time changes are also different.

The sensitivity of the FBG pollution sensor is different in the case of different coating thicknesses of moisture-sensitive materials.

The invention utilizes the inhibitory effect of pollution on specific humidity-sensitive FBG to develop the FBG pollution measurement sensor. The principle of the moisture-sensitive FBG is that the moisture-sensitive material expands by absorbing water, which leads to an increase in the strain of the FBG, which in turn redshifts the Bragg wavelength of the FBG. The water absorption of the moisture-sensitive material (such as polyimide) in the present invention is affected by the fouling components by using specific coating and modification methods. The sensor is arranged on the insulator of the transmission line without pollution. When the air humidity increases, the strain on the sensor increases and the wavelength red shifts. When only salt covers the insulator and sensor, when the air humidity increases, the FBG Bragg wavelength redshift decreases compared with the case of no pollution due to the salt contacting the FBG pollution sensor, but the response time does not change; only the ash covers the insulator and When the sensor is used, when the air humidity increases, due to the ash contacting the FBG pollution sensor, the FBG Bragg wavelength redshift response time increases compared with the non-pollution situation, and the redshift range is smaller than that of the non-pollution situation and smaller than the salt coverage situation.

Under the same salt density or dust density, the Bragg wavelength redshift of the developed FBG pollution sensor increases with the increase of humidity. Under the same gray density, the Bragg wavelength redshift response time of the developed FBG pollution sensor decreases with the increase of humidity. Under the same humidity, with the increase of salt density and dust density, the Bragg wavelength redshift of the developed FBG pollution sensor decreases. Under the same humidity, with the increase of dust density, the Bragg wavelength redshift response time of the developed FBG pollution sensor increases. The sensitivity of the FBG pollution sensor is different in the case of different coating thicknesses of moisture-sensitive materials.

The calculation formula of fiber Bragg grating compensation sensor temperature and humidity is:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right.$

λ ₃ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is coated with the moisture-sensitive material part;

λ ₄ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is not coated with the moisture-sensitive material part;

α _T3 is the sensitivity coefficient of Bragg wavelength to temperature obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor;

α _T4 is the sensitivity coefficient of the Bragg wavelength to temperature obtained from the part of the fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials;

α _H3 is the sensitivity coefficient of the Bragg wavelength to humidity obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor;

α _H4 is the sensitivity coefficient of the Bragg wavelength to humidity obtained from the part of the optical fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials;

T is the temperature;

H is humidity.

The calculation formulas of salt density and gray density are:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\end{array}\right.$

in:

λ ₁ is the Bragg wavelength of the first fiber Bragg grating pollution sensor;

λ ₂ is the Bragg wavelength of the second fiber Bragg grating pollution sensor;

α _T1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to temperature;

α _T2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to temperature;

α _H1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to humidity;

α _H2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to humidity;

α _S1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to salinity;

α _S2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to salinity;

α _A1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to the gray scale;

α _A2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to the gray scale;

T is the temperature;

H is humidity;

S is salinity;

A is grayscale.

The present invention contains the database of "humidity-sensitive coating thickness-humidity-salt density-gray density-red shift amplitude-red shift response time". The sensor measurement results and the database obtain the salt density and ash density of the measured point.

In the present invention, the FBG pollution sensor can be arranged on the insulators of different poles and towers, and the distributed measurement of the pollution of large-scale transmission lines can be realized by means of wavelength division multiplexing and time division multiplexing.

Fig. 1 is a schematic diagram of a fiber Bragg grating pollution sensor. Specific moisture-sensitive materials 100 are coated on the surface of a fiber Bragg grating 105. The sensor is arranged on an insulator of a power transmission line without pollution. When the air humidity increases, the sensor As the strain increases, the wavelength red shifts. When only salt covers the insulator and sensor, when the air humidity increases, the FBG Bragg wavelength redshift decreases compared with the case of no pollution due to the salt contacting the FBG pollution sensor, but the response time does not change; only the ash covers the insulator and When the sensor is used, when the air humidity increases, due to the ash contacting the FBG pollution sensor, the FBG Bragg wavelength redshift response time increases compared with the non-pollution situation, and the redshift range is smaller than that of the non-pollution situation and smaller than the salt coverage situation.

Fig. 2 is according to an embodiment of the present invention the fiber Bragg grating pollution sensor site layout diagram, insulator 200 is used for connecting wire 205 and crossarm 210, the purpose of the system of the present invention is to measure the pollution on the insulator 200, fiber Bragg The grating pollution sensor array (215) is arranged on the surface of the insulator, and is connected to the junction box 225 through the first outgoing optical fiber 220; the fiber Bragg grating compensation sensor 235 arranged in the shutter box 230 is used to measure the ambient humidity and temperature, It is connected to the junction box 225 through the second outgoing optical fiber 240 . The output optical cable 245 of the junction box is connected with OPGW or ADSS, or connected with OPPC through a special insulator. The computer 255 is connected to the wavelength demodulation system 250 by wired or wireless means; the wavelength demodulation system 250 is connected to the optical fiber composite overhead ground wire OPGW, all-dielectric self-supporting optical cable ADSS, OPPC optical cable or armored optical cable, junction box and optical fiber Bragg The grating sensor is connected.

Figure 3 is part of the data in the database "Moisture Sensitive Coating Thickness-Humidity-Salt Density-Gray Density-Redshift Amplitude-Redshift Response Time". Under the same humidity, with the increase of salt density, the Bragg wavelength redshift amplitude of the developed FBG pollution sensor decreases. Under the same salt density, the Bragg wavelength redshift of the developed FBG pollution sensor increases with the increase of humidity.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (10)

1. A fiber Bragg grating transmission line pollution on-line monitoring system is characterized in that the system includes a computer, a wavelength demodulation system, a junction box, a junction box output optical cable, a shutter box, the first lead-out optical fiber, the second lead-out optical fiber, Fiber Bragg grating pollution sensor array and fiber Bragg grating compensation sensor; The wavelength demodulation system includes a solar power generation module and a wireless communication module; The computer is connected to the wavelength demodulation system; the wavelength demodulation system is connected to the junction box through the output optical cable of the junction box; Connect to the grating compensation sensor; the optical fiber Bragg grating compensation sensor is placed in the shutter box; The fiber Bragg grating pollution sensor array is composed of a first fiber Bragg grating pollution sensor and a second fiber Bragg grating pollution sensor, and the first fiber Bragg grating pollution sensor is coated with a first set thickness wet The fiber Bragg grating of sensitive material; The second fiber Bragg grating pollution sensor is the fiber Bragg grating of coating the second setting thickness moisture sensitive material; Half of the optical fiber Bragg grating compensation sensor is an optical fiber Bragg grating coated with a moisture-sensitive material with a third set thickness, and the other half of the optical fiber Bragg grating compensation sensor is an optical fiber Bragg grating that is not coated with a moisture-sensitive material. The fiber Bragg grating compensation sensor is equipped with a moisture-permeable and dust-proof sheath; The wavelength demodulation system is used to demodulate the wavelength collected by the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor; The computer uses the Bragg wavelength data demodulated by the wavelength demodulation system to calculate and obtain salt density and gray density. 2. A kind of optical fiber Bragg grating transmission line contamination online monitoring system according to claim 1, characterized in that the output optical cable of the junction box is an optical fiber composite overhead ground wire OPGW, an all-dielectric self-supporting optical cable ADSS, an OPPC optical cable or armored fiber optic cable. 3. A kind of fiber Bragg grating transmission line contamination online monitoring system according to claim 1, characterized in that the first fiber Bragg grating pollution sensor and the second fiber Bragg grating pollution sensor are connected for series or parallel connection. 4. A fiber Bragg grating transmission line pollution on-line monitoring system according to claim 1, characterized in that said moisture-sensitive material is polyimide or hydrogel. 5. An online monitoring system for contamination of fiber Bragg grating transmission lines according to claim 1, characterized in that the computer and the wavelength demodulation system are connected through a network cable or a wireless communication module. 6. The on-line monitoring system for contamination of fiber Bragg grating transmission lines according to claim 5, characterized in that when the computer and the wavelength demodulation system are connected through a network cable, the wavelength demodulation system is powered by commercial power. 7. A kind of optical fiber Bragg grating transmission line contamination online monitoring system according to claim 5, characterized in that when the computer and the wavelength demodulation system are connected through a wireless communication module, the wavelength demodulation system is powered by a solar power generation module . 8. A method for on-line monitoring of transmission line pollution according to the system of claim 1, characterized in that the method comprises the following steps: Step 1: placing the junction box, the shutter box, the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor at a designated position on the transmission line; Step 2: Send the data collected by the fiber Bragg grating pollution sensor array and the fiber Bragg grating compensation sensor to the wavelength demodulation system through the junction box; Step 3: the wavelength demodulation system sends the demodulated Bragg wavelength data to the computer; Step 4: The computer calculates salt density and gray density according to the demodulated Bragg wavelength data. 9. The method for on-line monitoring of transmission line pollution according to claim 8, characterized in that the calculation formula of the optical fiber Bragg grating compensation sensor temperature and humidity is: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right.$ λ ₃ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is coated with the moisture-sensitive material part; λ ₄ is the Bragg wavelength that the optical fiber Bragg grating compensation sensor is not coated with the moisture-sensitive material part; α _T3 is the sensitivity coefficient of Bragg wavelength to temperature obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor; α _T4 is the sensitivity coefficient of the Bragg wavelength to temperature obtained from the part of the fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials; α _H3 is the sensitivity coefficient of the Bragg wavelength to humidity obtained by coating the moisture-sensitive material part of the optical fiber Bragg grating compensation sensor; α _H4 is the sensitivity coefficient of the Bragg wavelength to humidity obtained from the part of the optical fiber Bragg grating compensation sensor that is not coated with moisture-sensitive materials; T is the temperature; H is humidity. 10. A method for on-line monitoring of transmission line pollution according to claim 9, characterized in that the formulas for calculating salt density and gray density are: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\\ {\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\end{array}\right.$ in: λ ₁ is the Bragg wavelength of the first fiber Bragg grating contamination sensor; λ ₂ is the Bragg wavelength of the second fiber Bragg grating pollution sensor; α _T1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to temperature; α _T2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to temperature; α _H1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to humidity; α _H2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to humidity; α _S1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to salinity; α _S2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to salinity; α _A1 is the sensitivity coefficient of the Bragg wavelength of the first fiber Bragg grating pollution sensor to the gray scale; α _A2 is the sensitivity coefficient of the Bragg wavelength of the second fiber Bragg grating pollution sensor to the gray scale; S is salinity; A is grayscale.

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