CN106290183A - snow state parameter measuring method based on spectral reflectance - Google Patents

Abstract

The invention relates to a method for measuring snow state parameters based on spectral reflectance. Its main technical characteristics include the following steps: measuring standard snow sample state parameter data and establishing a regression fitting equation for standard snow sample state parameters; on-site measurement of transmission line insulators The spectral reflectance of the snow covered, and according to the regression fitting equation, the moisture content, bulk density and particle size of the snow sample to be measured are obtained. The invention forms a database by establishing the fitting equation of the spectral reflectance of the standard snow sample and state parameters such as snow water content, bulk density and particle size, and by measuring the spectral reflectance of the snow sample on the on-site power transmission line and insulator, the fitting equation The moisture content, bulk density and particle size of the snow are obtained, and the remote measurement function of the state parameters of the snow covering on the running insulator far away from the ground is realized. Its flashover work provides an important reference.

Description

Measurement method of snow state parameters based on spectral reflectance

technical field

The invention belongs to the technical field of transmission lines, in particular to a method for measuring snow state parameters based on spectral reflectance.

Background technique

With the deepening of my country's economic structural transformation, the output value of high-value-added high-precision industries is increasing year by year. These industries have high requirements for power quality and power supply reliability. However, my country's complex topography and frequent occurrence of micro-meteorological conditions lead to ice and snow covering insulators of transmission lines, greatly reducing insulation strength, inducing insulator flashover accidents, causing large-scale power outages and economic losses. In order to prevent the power transmission system from being affected by complex weather environments, such as ice and snow and other natural disasters, it is urgent to conduct research on related issues and propose corresponding prevention methods.

At present, domestic and foreign studies generally believe that when the icing type of transmission line insulators is rime, the flashover voltage is the lowest, so the flashover probability is the highest. However, under special climatic conditions, flashovers caused by snow cover often occur. The snow-covered flashover accident of transmission lines has promoted the research process of insulator snow-covered flashover mechanism, and the snow-covered bridging shed that may lead to flashover factors, inner layer melting and icing, or snow-covered form changes under special climatic conditions have been paid attention to. Relevant foreign scholars have found that there are obvious differences in the development process of leakage current, local arc distribution and flashover process of snow in different states. Snow with very low water content, that is, dry snow, has high snow body resistance and small leakage current, and the Joule heat generated is not enough to melt the snow body, and the state of the insulator remains unchanged, so the flashover voltage is high; while snow with high water content , that is, wet snow, in which the snow-water mixture flows along the shed of the insulator, which greatly reduces the insulation resistance, distorts the electric field of the insulator, and then generates a local arc, and finally develops to a full-string flashover, so the flashover voltage is low and the flashover Great danger. Therefore, the measurement of the state parameters of insulator snow cover is the basis of on-site snow protection and flashover work.

Since EHV and UHV insulators are erected on transmission towers far away from the ground, the height above the ground is more than 20 meters, it is difficult to effectively distinguish different states of snow with the naked eye, and in order to reduce the impact on normal power supply, power failure cannot The snow cover is sampled for direct measurement. In order to enable inspection personnel to accurately and timely grasp the snow coverage of transmission line insulators, it is urgent to conduct long-distance measurement of snow state parameters.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, provide a snow state parameter measurement method based on spectral reflectance, and solve the problem of remote measurement of the snow-covered state of transmission line insulators.

The present invention solves its technical problem and realizes by taking the following technical solutions:

A method for measuring snow state parameters based on spectral reflectance, comprising the following steps:

Step 1. Measure the standard snow sample state parameter data and establish the regression fitting equation of the standard snow sample state parameter;

Step 2. Measure the spectral reflectance of the snow covered on the insulator of the transmission line on site, and obtain the water content, bulk density and particle size of the snow sample to be tested according to the regression fitting equation.

The processing method of the step 1 is:

(1) The spectrometer receives the optical fiber probe to keep the angle between the incident light and reflected light and the normal at 45 degrees, and the azimuth angle of the optical fiber detection is 180 degrees;

⑵ Turn on the spectrometer, adjust and set up the instrument;

(3) Use a standard reflective white board as a sample, and obtain the spectral intensity value of the white board at 400-1400nm as a reference, which is recorded as A ₀ ;

(4) Use the standard snow sample to be tested as a sample to obtain the spectral intensity value of the snow sample at 400-1400 nm, which is recorded as A _i ;

(5) Obtain the standard reflectance array of the snow sample, denoted as R _i , then

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; .</span>$

⑹ Measure the bulk density and particle size of the snow sample;

(7) Use the data of the characteristic spectral segment in R _i to establish the regression fitting equation with the water content, bulk density and particle size of snow respectively. The fitting equation is as follows:

W _c =A ₁ R _a +B ₁

V _d =A ₂ R _b +B ₂

D _p =A ₃ R _c +B ₃

In the formula: W _c , V _d and D _p are the water content, bulk density and particle size of the standard snow sample, respectively. A ₁ , A ₂ , A ₃ , B ₁ , B ₂ and B ₃ are constants, respectively undetermined coefficients of the fitting equation, and R _a , R _b and R _c are the characteristics corresponding to the fitting equation of the three state parameters Standard reflectance for spectral bands.

The standard snow sample state parameter database includes the following three state parameters: moisture content, bulk density and particle size of snow.

Described four kinds of standard snow samples are respectively: dry snow, tide snow, wet snow and water wet snow, and described dry snow snow sample is the pure snow of natural sampling; Described tide snow is 200g pure snow+20g water, and it has Viscous and unformed granular snow; the wet snow is 230g pure snow + 120g water, which has a relatively high viscosity and is formed in a container; the water wet snow is 280g pure snow + 210g water , which is in the slush state.

The concrete method of described step 2 is:

(1) Point the spectrometer receiving fiber optic probe to the snow on the insulator to be measured, measure its spectral intensity value, and measure the incident angle of sunlight at this time, the detection angle and azimuth angle of the spectrometer receiving light; the wavelength range that the spectrometer can detect is required to be 400nm ~1400nm;

(2) Use a standard reflective white board to measure the spectral intensity value of 400-1400nm as a benchmark;

(3) Obtain the 400-1400nm spectral reflectance curve of the snow body to be measured, and substitute the data of a specific spectral segment into the fitting equation to obtain the water content, bulk density and particle size state parameters of the snow body to be measured.

The standard reflective whiteboard is a whiteboard made of barium sulfate.

Advantage and positive effect of the present invention are:

The invention forms a database by establishing the fitting equation of the spectral reflectance of the standard snow sample and state parameters such as snow water content, bulk density and particle size, and measures the spectral reflectance of the snow sample on the on-site power transmission line and the insulator to fit the The water content, bulk density and particle size of the snow are obtained, thus forming a complete and standard measurement process, completing the research on the state parameters of the snow, and realizing the state parameters of the snow covered on the running insulator far away from the ground The long-distance measurement function can quickly understand the snow-covered status of transmission line insulators, and provide important references for line snow-covered protection and flashover work. As a set of complete and standard measurement procedures, the present invention can guide the measurement of snow state parameters under different degrees of ice and snow weather in different regions, and enables on-site inspection personnel to accurately and timely grasp the snow-covered conditions of transmission line insulators.

Description of drawings

Fig. 1 is the schematic diagram of the principle of the method for measuring spectral reflectance of the invention;

In the figure, the sample can be a standard snow sample, a standard reflective whiteboard or a snow body during on-site measurement.

detailed description

Embodiments of the invention are described in further detail below in conjunction with the accompanying drawings:

A method for measuring snow state parameters based on spectral reflectance, comprising the following steps:

Step 1. Measure the state parameter data of the standard snow sample and establish the regression fitting equation of the standard snow sample state parameter.

In this step, a database of state parameters of standard snow samples needs to be established, and the data of spectral reflectances of 400-1400 nm of snow in four states are measured. The four states of snow are formulated according to different ratios of dry snow and water, namely dry snow, wet snow, wet snow and water wet snow. The dry snow sample is pure snow sampled naturally, and the tide snow is 200g pure snow + 20g water, which has a slightly viscous consistency, but it is still unformed granular snow. Wet snow is 230g pure snow + 120g water, with a high viscosity, and the sample can be shaped in a container. Water-wet snow is 280g pure snow + 210g water. The snow of this sample has a high degree of melting and becomes slush. The spectral reflectance, bulk density and particle size of the four state parameters were measured respectively. Figure 1 shows the schematic diagram of the spectral reflectance measurement method.

The specific process of this step is as follows:

(1) Keep the angle between the incident light and reflected light and the normal at 45 degrees, and the azimuth angle of the optical fiber detection is 180 degrees, that is, facing the direction of the incident light;

(2) Turn on the spectrometer, adjust and set up the instrument;

(3) Use a standard reflective white board (a white board made of barium sulfate is recommended) as a sample, and obtain the spectral intensity value of the white board at 400-1400nm, as a reference, and denote it as A ₀ ;

(4) Using the standard snow sample to be tested as a sample, obtain the spectral intensity value of the snow sample at 400-1400nm, which is denoted as A _i ;

(5) Obtain the standard reflectance array of the snow sample, denoted as R _i , then

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; .</span>$

(6) measure bulk density and particle diameter that obtain snow sample;

(7) Use the data of the characteristic spectral segment in R _i to establish the regression fitting equation with the water content, bulk density and particle size of snow respectively, the fitting equation is as follows:

W _c =A ₁ R _a +B ₁

V _d =A ₂ R _b +B ₂

D _p =A ₃ R _c +B ₃

In the formula: W _c , V _d and D _p are the water content, bulk density and particle size of the standard snow sample, respectively. A ₁ , A ₂ , A ₃ , B ₁ , B ₂ and B ₃ are constants, respectively undetermined coefficients of the fitting equation, and R _a , R _b and R _c are the characteristics corresponding to the fitting equation of the three state parameters Standard reflectance for spectral bands. Since different parameters correspond to different spectral absorption peak positions, there are differences in this value.

Step 2. Measure the spectral reflectance of the snow covered on the insulator of the transmission line on site, and obtain the water content, bulk density and particle size of the snow sample to be tested according to the regression fitting equation.

The measurement method in this step is similar to that in step 1, and the spectral reflectance S _i of the transmission line insulator snow is obtained. The specific process is as follows:

(1) During on-site measurement, point the spectrometer receiving fiber optic probe to the snow on the insulator to be measured, measure its spectral intensity value, and measure the sunlight incident angle at this time, the spectrometer receiving light detection angle and azimuth angle. The wavelength range that the spectrometer can detect is required to be at least 400nm to 1400nm.

(2) Using a standard reflective white board, measure the spectral intensity value at 400-1400nm as a reference. It is recommended to set the optical system parameters to be the same as when measuring snow on insulators, that is, the incident angle, reflection angle and azimuth angle are all the same.

(3) Obtain the spectral reflectance curve of the snow body to be measured from 400 to 1400nm, and substitute the data of a specific spectral segment into the fitting equation obtained in step 1, and then obtain the water content, bulk density and particle size of the snow body to be measured parameter.

Due to the impact of on-site measurement visibility on measurement accuracy, the present invention needs to carry out measurement work respectively under fine weather and foggy conditions during on-site measurement.

It should be emphasized that the embodiments described in the invention are illustrative rather than limiting, so the invention includes and is not limited to the embodiments described in the specific implementation, and those who are obtained by those skilled in the art according to the technical solution of the invention Other implementation modes also belong to the scope of invention protection.

Claims (6)

1. a snow state parameter measuring method based on spectral reflectance, it is characterised in that comprise the following steps:

Step 1, measurement standard snow core state parameter data the regression fit equation of Criterion snow core state parameter；

The spectral reflectance of snowberg on step 2, in-site measurement electric transmission line isolator, and obtain according to regression fit equation model The water content of snow core to be measured, unit weight and particle diameter.

Snow state parameter measuring method based on spectral reflectance the most according to claim 1, it is characterised in that: described step The processing method of rapid 1 is:

(1) spectrogrph receives fibre-optical probe holding incident illumination and is 45 degree with reflecting the light angle with normal, the orientation of fiber-optic probe Angle is 180 degree；

(2) open spectrogrph, adjust and set instrument；

(3) make sample with standard reflection blank, obtain the spectral intensity values of blank 400～1400nm, as benchmark, be designated as A₀；

(4), with standard snow core to be measured as sample, obtain the spectral intensity values of snow core 400～1400nm, be designated as A_i；

(5) obtain the standard reflection of snow core than array, be designated as R_i, then

$R_i=\frac{A_i}{A_0}.$

(6) measure unit weight and the particle diameter obtaining snow core；

Use R the most respectively_iRegression fit equation between water content, unit weight and particle diameter that the data of middle characteristic light spectral coverage are set up and avenged, should Fit equation is as follows:

W_c=A₁R_a+B₁

V_d=A₂R_b+B₂

D_p=A₃R_c+B₃

In formula: W_c、V_dAnd D_pIt is the water content of standard snow core, unit weight and particle diameter respectively.A₁、A₂、A₃、B₁、B₂And B₃It is constant, point It not the undetermined coefficient of fit equation, R_a、R_bAnd R_cIt is the fit equation characteristic of correspondence spectrum segment of three kinds of state parameters respectively Standard reflection ratio.

Snow state parameter measuring method based on spectral reflectance the most according to claim 1, it is characterised in that: described mark Quasi-snow core state parameter data base includes following three kinds of state parameters: the water content of snow, unit weight and particle diameter.

Snow state parameter measuring method based on spectral reflectance the most according to claim 3, it is characterised in that: described four Planting standard snow core and be respectively as follows: dry snow, tide snow, snow slush and water snow slush, described dry snow snow core is the pure snow of natural sampling；Described tide snow Being 200g pure snow+20g water, it has viscosity and avenges for unfashioned shot；Described snow slush is 230g pure snow+120g water, its Have compared with high viscosity and shaping placed in the vessel；Described water snow slush is 280g pure snow+210g water, and it is slush state.

Snow state parameter measuring method based on spectral reflectance the most according to claim 1, it is characterised in that: described step Rapid 2 method particularly includes:

(1) spectrogrph is received fibre-optical probe and points to the snowberg on insulator to be measured, measure its spectral intensity values, and measure Angle of incidence of sunlight now, spectrogrph receives optical detection angle and azimuth；The wave-length coverage that spectrogrph can detect requires 400nm～1400nm；

(2) use standard reflection blank, measure the spectral intensity values of 400～1400nm, as benchmark；

(3) obtain treating the spectral reflectance curve of snow survey body 400～1400nm, by the data of certain spectral, substitute into fit equation, And then obtain treating the water content of snow survey body, unit weight and particle diameter state parameter.

6. according to the snow state parameter measuring method based on spectral reflectance described in claim 2 or 5, it is characterised in that: institute Stating standard reflection blank is barium sulfate blank.