CN111461918B - Power transmission line tree flash hidden danger monitoring method based on satellite optical image - Google Patents
Power transmission line tree flash hidden danger monitoring method based on satellite optical image Download PDFInfo
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Abstract
The invention discloses a method for monitoring the tree flashover hidden danger of a power transmission line based on satellite optical images, which utilizes satellite optical image data and data, takes crown line distance, tree line distance and tree height as evaluation indexes of the tree flashover hidden danger of the power transmission line, adopts a mark control watershed algorithm to extract the size of a crown and a maximum likelihood method to extract the power transmission line, and provides a crown line and tree line shortest distance calculation method based on a tree height and shortest distance method of a distance compensation method, thereby monitoring, identifying and evaluating the tree flashover hidden danger of the power transmission line.
Description
Technical Field
The invention belongs to the technical field of natural disaster fault monitoring of power transmission lines, and particularly relates to a power transmission line tree flash hidden trouble monitoring method based on satellite optical images.
Background
With the increase of the power grid scale, the probability of tree flashover accidents of the power transmission line in thunderstorm weather is also increased. In natural disaster accidents of the power transmission line, lightning disaster accidents account for more than 70%; the tree flash may cause the shutdown of the power transmission line due to the protection trip, the sudden trip of the power transmission line also threatens the safe and stable operation of a large-scale power grid, the life of people is influenced, and huge economic loss is brought to production. Therefore, if the hidden danger of the tree flash fault can be found in time, the damage can be minimized by timely arranging and arranging the handling and checking personnel for processing.
At present, the transmission line inspection is still mainly carried out by manual inspection and manual recording, and the defects of high cost, dangerous working conditions, inspection missing and the like exist, so that the transmission line inspection is difficult to operate and maintain and has high working strength. In recent years, aviation inspection is adopted, and the detection efficiency and the detection precision are improved. But aviation inspection is limited by factors such as flight safety, aviation control, weather changes, and fueling. The development of satellite technology provides a new means for transmission line tree flash monitoring, and compared with manual and aviation inspection, satellite inspection has the advantages of short period, no potential safety hazard, wider inspection coverage area, high response speed and the like. At present, satellite optical images are applied to the forest management fields of tree crown segmentation, tree height calculation and the like, but researches and concerns on the aspect of monitoring the flashover hidden danger of the power transmission line are few.
Disclosure of Invention
The tree flashing accident is related to the tree and the crown line distance, the tree height and other parameter indexes of the power transmission line, the tree growth speed is high, the crown is close to the power transmission line, and the tree flashing fault can easily occur, so that the power transmission line is tripped and stopped, the safe and stable operation of a power system is threatened, and huge losses are brought to the life and production of people. Because the tree flash fault hidden danger and the accident risk are in direct proportion to the crown line distance, the tree height and other parameter indexes of the power transmission line, the tree flash fault hidden danger of the power transmission line can be judged according to the data indexes, and the tree flash fault hidden danger can be timely found and judged through monitoring the data indexes. The invention provides a method for extracting and judging the size of a tree crown based on a mark control watershed algorithm based on remote sensing satellite optical image data and data, and respectively calculating the height of a tree, the shortest distance between the edge of the tree crown and the peak of the tree and a power transmission line based on a tree height compensation method and a shortest distance algorithm, thereby realizing the identification and judgment of the fault hidden danger of tree flashover of the power transmission line. Based on satellite optical image data and data, the method for identifying and monitoring the tree flash fault hidden danger of the power transmission line has the advantages of short inspection period, no potential safety hazard, wide inspection coverage area, high response speed and the like of the power transmission line.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention utilizes satellite optical image data and data, takes crown line distance, tree line distance and tree height as evaluation indexes of the tree flash hidden trouble of the power transmission line, adopts a mark control watershed algorithm to extract the size of the crown and a maximum likelihood method to extract the power transmission line, and provides a crown line and tree line shortest distance calculation method based on a tree height and shortest distance method of a distance compensation method, thereby monitoring, identifying and evaluating the tree flash hidden trouble of the power transmission line.
A method for monitoring the tree flash hidden trouble of a power transmission line based on satellite optical images comprises the following steps:
1) 4 wave bands of the satellite image are analyzed by an optimal index method (OIF), wherein 1 wave band, 2 wave band, 3 wave band and 4 wave band correspond to the following steps: blue light wave band, green light wave band, red light wave band and near infrared wave band, 4 wave bands have four kinds of wave band combinations, are respectively: 1. 2,3 wave bands, 1,2, 4 wave bands, 1, 3, 4 wave bands, 2,3, 4 wave bands, respectively calculating the indexes of the wave band combinations, selecting the wave band combination with the largest index as an experimental wave band, then generating a false color image of the experimental wave band by using ENVI software, carrying out normalized vegetation index treatment and mask treatment on the false color image, and segmenting out a crown area image by morphological filtering and a watershed marking algorithm;
2) Coarse classification is carried out on the power transmission line images in the satellite images by using a maximum likelihood method, and the classified power transmission line images are manually classified for the second time in ENVI class to obtain power transmission line images;
3) Intercepting a tree satellite picture in a satellite image, then importing the tree satellite picture into a sktch Up software, constructing an external rectangle of the tree satellite picture in the tree satellite picture, setting the time and place of the tree satellite picture in the sktch Up software, adjusting the height of the external rectangle to establish a three-dimensional model of the external rectangle of the tree contour, enabling the shadow highest point of the three-dimensional model to coincide with the shadow highest point of the tree satellite picture, measuring the height of the three-dimensional model, obtaining pseudo tree height through proportional conversion, and calculating by adopting a distance compensation method to obtain the tree height after compensation correction;
4) Synthesizing the crown area image obtained in the step 1) and the power transmission line image obtained in the step 2), determining the shortest distance from the tree to the power transmission line by adopting a circular ring search method according to the synthesized image of the crown area image and the power transmission line image, and determining the shortest distance from the power transmission line to the crown edge by adopting a strip area search method;
5) Dividing the early warning of the tree flashover hidden trouble of the power transmission line into the following steps according to the shortest distance from the tree to the power transmission line and the shortest distance from the power transmission line to the edge of the crown, which are obtained in the step 4): extremely dangerous, and the need for removing tree barriers is urgent; medium danger, need to clear the tree obstacle recently; safety, no attention is required in the recent time; thus giving an early warning strategy.
Based on the above scheme, the calculation formula of the index of the band combination in step 1) is:
wherein OIF is the index of band combination, S i I=1, 2,3, r, the standard deviation of the i-th band in the band combination jk And r is the number of combinations of different wave bands in the wave band combination.
Based on the scheme, the specific process of calculating the compensated and corrected tree height by adopting the distance compensation method in the step 3) is as follows:
the true shade length of the tree is I 1 +X L By using the height h of the three-dimensional model m And calculating the shadow length I of the three-dimensional model by the solar altitude angle alpha 1 Obtaining a compensation distance X according to the distance from the center of the crown to the edge of the crown L Then calculating to obtain the tree real tree height H by using trigonometric function s The calculation formula is as follows:
δ(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)
+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t= (true solar time-12) ×15° (5)
True solar time = flat solar time + true solar time difference (6)
I 1 ＝h m /tan(α) (7)
H s ＝(I 1 +X L )×tan(α) (8)
Wherein alpha is the solar altitude angle,
for geographic latitude, delta represents solar declination, and t represents time angle; b is the angle of earth revolution from 1 month 1 day to the calculation day, the calculation formula is b=2×pi× (day-1)/365, day is the number of days from 1 month 1 day to the calculation day each year, pi is the circumference ratio, and deg represents the angle; real solar time is a time system formulated according to real solar days; the solar time is Beijing time; the true solar time difference is the time difference between the satellite image shooting place and the Beijing time by taking the Beijing time as a marker post; i 1 Is the shadow length of the three-dimensional model, h m For three-dimensional model height, H s X is the true height of the tree L To compensate for the distance.
Based on the scheme, the specific process of the circular ring search method in the step 4) is as follows:
firstly, preprocessing the edge of a crown and a power transmission line, distinguishing different crowns and power transmission lines by setting different gray values for different crown edges and power transmission lines, and then using crown vertices O (x) 0 ,y 0 ) The edge point of the crown closest to the crown vertex is the radius r d Making a circle with radius r d Is in pixels, the circular equation is:
(x-x 0 ) 2 +(y-y0) 2 ＝r d 2 (9)
by r d +1 as new radius, with crown vertex O (x 0 ,y 0 ) Continuing to make a circle for the center of the circle, wherein the equation of the circle is as follows:
(x-x 0 ) 2 +(y-y 0 ) 2 ＝(r d +1) 2 (10)
the part of the circular ring formed between the two circles is a search area, and the search area meets the requirement
r d 2 <＝(x-x 0 ) 2 +(y-y0) 2 <＝(r d +1) 2 (11)
If no satisfactory points exist in the search area, the radius of the inner and outer circles is increased by 1 pixel to form a new circular ring to continue searching until satisfactory pixel points are searched, and all satisfactory pixel points in the circular ring are subjected to distance calculation with the circle center to obtain a distance (d 1 ,d 2 ,...,d n ) Find the minimum distance d from it s D as the minimum horizontal distance of the tree line s The unit of (2) is pixel, and the calculation formula of the distance is:
wherein, (x) i‘ ,y i’ ) Is any point in the ring that meets the requirements, where i' =1, 2,.. i’ A horizontal distance from the point to the crown vertex;
minimum horizontal distance d of tree line according to resolution of image s The shortest horizontal distance D from the tree to the transmission line is converted into the actual tree to the transmission line, the unit is meter, and the conversion formula is as follows:
D＝d s x resolution (13)
The shortest horizontal distance D of the tree to the transmission line is combined with the transmission line height M and the true height H of the tree s Whether the tree breaks and threatens the power transmission line is calculated, and the calculation formula is as follows:
wherein S is the linear distance from the bottom end of the tree to the power transmission line, the unit is meter, W is the nearest distance from the power transmission line when the tree breaks, and the unit is meter, wherein the height M of the power transmission line and the true height H of the tree s The units of (a) are all meters.
Based on the scheme, the specific process of the strip-shaped area searching method in the step 4) is as follows:
according to the minimum horizontal distance d of the tree line s Obtaining the crown vertex O (x) 0 ，y 0 ) Nearest point P 1 (x 1 ，y 1 ) The shortest distance theorem from point to straight line can obtain line segment OP 1 Perpendicular to the transmission line L 1 ，P 1 For foot drop, according to crown vertices O and P 1 The coordinates of the points give line segments OP 1 Slope k of (2) 1 The power line L is obtained by the product of the vertical slopes of the two straight lines being-1 1 Slope k of (2) 2 Transmission line L 1 And line segment OP 1 The linear equation of (2) is:
the power line L 1 Along line segment OP 1 Shifting one pixel unit downward in the direction to obtain a slope k 2 Straight line L of (2) 2 Straight line L 2 And line segment OP 1 Intersecting at point P 2 Let P be 2 Is (x) 2 ,y 2 ) The minimum horizontal distance of the tree line is d s Thus OP 2 Length d of (2) s -1, P 2 The point coordinates are taken into the formulas (12) and (15), and calculated to obtain:
by P 2 Point coordinates and straight line L 2 Slope of (2) to obtain a straight line L 2 Equation, power line L 1 And straight line L 2 The strip-shaped area between the two is used as a searching area, and if no point meeting the requirement exists in the searching area, the power transmission line L is used for 1 And straight line L 2 All along OP 1 Translating 1 pixel downwards in the direction to form a new search area, continuing to search until the pixel points meeting the requirements are searched for the first time, and calculating all the pixel points meeting the requirements and the power transmission line L by using a point-to-straight line distance formula 1 The formula is as follows:
where U, V, G is the coefficient of the linear equation, (x) s' ,y s' ) For any target point coordinate to be calculated, s' e [1, n]，f s' For any target point to be calculated to the power line L 1 Finding the minimum distance F from the power line to the crown edge, obtaining the minimum distance F from the power line to the crown edge in pixels, and multiplying the minimum distance F from the power line to the crown edge by the resolution to obtain the actual minimum horizontal distance F from the power line to the crown edge s The unit is meter.
Based on the scheme, the specific process of the step 5) is as follows:
the positional relationship between trees and transmission lines is divided into two types:
(1) When the tree is under the transmission line, the transmission line is threatened by the tree, the transmission line height M and the true tree height H s Related to;
a)M-H s <9, issuing a first-level early warning when extremely dangerous;
b)9<M-H s <12, moderately dangerous, issuing a second-level early warning;
c)M-H s >12, safety and no early warning is issued;
(2) When the tree is on the two sides of the transmission line, whether the transmission line is threatened or not and the true height H of the tree s Height M of the transmission line, shortest distance W from the transmission line when the tree breaks, shortest horizontal distance F from the transmission line to the crown edge s Related to;
a)F s <8.5 and H s >When M-2 or W is less than or equal to 0, the danger is extremely high, and a first-level early warning is issued;
b)F s >11.5 and W>3 or H s <M-9, safety and no early warning are issued;
c) Other conditions are moderate dangers, and secondary early warning is issued.
The beneficial effects are that:
the method for monitoring the tree flash hidden trouble of the transmission line based on the satellite optical image utilizes the high-resolution No. 2 satellite image with the resolution of 0.8 meter, and develops a case simulation calculation result to show that the method has the following effects:
1) The proposed algorithm for calculating the shortest distance between the tree and the transmission line and the shortest distance between the edge of the crown and the transmission line can judge whether the transmission line is threatened by the trees at the two sides and below.
2) The existing crown segmentation and building height calculation method is applied to crown extraction and tree height calculation of the power transmission line tree flash hidden trouble monitoring, and the tree height compensation method is added to the tree height compensation method monitoring and calculating flow.
3) The tree flashing hidden danger monitoring flow including crown segmentation, transmission line segmentation, tree height calculation, tree line distance, crown line distance and early warning criterion is constructed, and the monitoring of the tree flashing hidden danger of the transmission line can be realized.
4) The result of the calculation of the typical case shows that the accuracy of the monitoring method for the tree flashover hidden danger can reach 82.69 percent, and the method can be used for satellite inspection monitoring of the tree flashover hidden danger of the power transmission line.
5) Although the accuracy of satellite monitoring of the tree flash hidden trouble of the transmission line is still to be improved, compared with aviation inspection and monitoring, the satellite monitoring system has the advantages of short period, no potential safety hazard, wider inspection coverage area and the like.
Drawings
Fig. 1 is a tree height compensation principle.
Fig. 2 tree apex search principle.
Fig. 3 crown line distance search principle.
Fig. 4 is a flowchart of a method for monitoring the potential risk of the tree flashover of the transmission line based on satellite optical images.
Detailed Description
The present invention will be fully described in detail with reference to the accompanying drawings, figures 1-4.
According to the flow chart of the method for monitoring the tree flash hidden trouble of the power transmission line in FIG. 4, the specific implementation modes of the techniques of image segmentation, tree height calculation, tree-to-power transmission line distance algorithm, early warning criterion and the like are as follows.
1) Image segmentation
The satellite images have 4 wave bands of red, green, blue and near infrared, in order to reduce the data processing amount, correlation analysis is firstly carried out, and 3 wave bands with the maximum information content are selected as experimental wave bands by using an optimal exponential method (Optimum Index Factor, OIF). The calculation formula of OIF is:
wherein OIF is the index of band combination, S i Is the standard deviation of the ith wave band in the wave band combination, R jk And r is the number of combinations of different wave bands in the wave band combination.
The ENVI software was used to calculate the correlation coefficient and covariance between the image bands, and the calculation results are shown in Table 1.
TABLE 1 correlation coefficient and covariance for each band
| | Band | 1 | Band 2 | Band 3 | Band 4 |
| |
1.000000 | 0.993261 | 0.990752 | 0.759142 | |
| Band 2 | 0.993261 | 1.000000 | 0.986537 | 0.816912 | |
| Band 3 | 0.990752 | 0.986537 | 1.000000 | 0.749464 | |
| Band 4 | 0.759142 | 0.816912 | 0.749464 | 1.000000 | |
| Covariance (covariance) | |
Band 2 | Band 3 | Band 4 | |
| |
2560.926532 | 3172.649500 | 4168.986695 | 3228.762659 | |
| Band 2 | 3172.649500 | 3984.012354 | 5177.744817 | 4333.614357 | |
| Band 3 | 4168.986695 | 5177.744817 | 6914.075962 | 5237.600634 | |
| Band 4 | 3228.762659 | 4333.614357 | 5237.600634 | 7063.651733 |
The combination form of the 4 wave bands is as follows: 1. 2,3 wave bands; 1. 2, 4 wave bands; 1. 3, 4 wave bands; 2. the data in table 1 are substituted into the formula (1) to calculate OIF, and the calculation results are shown in table 2.
TABLE 2 OIF calculation results
| |
1，2，3 | 1，2，4 | 1，3，4 | 2，3，4 |
| Correlation coefficient | 2.97055 | 2.569315 | 2.499358 | 2.552913 |
| Standard deviation of | 13459.01 | 13608.59 | 16538.65 | 17961.74 |
| OIF | 4530.816 | 5296.583 | 6617.161 | 7035.782 |
As can be seen from table 2, the OIF values of bands 2,3, 4 are the largest, i.e. the best band combination. And synthesizing the standard false color images by the 2,3 and 4 wave bands according to the sequence of 4, 3 and 2. To further highlight crown removal background, normalized vegetation index processing (normalized differenced vegetation index, NDVI) is performed on the standard false color image, and the standard calculation formula of NDVI is:
wherein NDVI is normalized vegetation index, NIR is near infrared band reflectivity, R b The reflectivity of the red light wave band corresponds to the two wave bands with the lowest correlation in the wave band combination, namely the wave band 4 and the wave band 3.
Setting a threshold value to classify the NDVI result, taking the classified image as a mask to mask the false color image, and carrying out morphological filtering on the processed image. The top of the crown is strongest in solar radiation, the pixel reflectivity is larger, the tree top point is a local maximum point of the crown area, and the tree top point is used as a foreground mark; at this time, the background of the image is black, so that the point with the pixel value of 0 is used as a background mark, and the crown area is segmented by a watershed algorithm.
And marking and classifying the ground features such as the power transmission lines, the crowns and the lands in the images by using ENVI software, wherein the classified images have a small amount of wrong classification, and the ENVI classification software is required to be modified manually, namely, the areas of the power transmission lines are re-marked and the power transmission lines are extracted.
2) Tree height calculation
The Sketch Up software has the function of simulating sun and light, can enable an object to generate corresponding shadows at a certain set moment and place, introduces satellite pictures, builds external rectangles of trees in the pictures, sets the time and place of the pictures in the software, adjusts the height of the external rectangles to build a three-dimensional model, enables the highest point of the shadows of the model to coincide with the highest point of the shadows of the trees, measures the height of the three-dimensional model, and obtains pseudo tree heights through proportional conversion.
The pseudo tree height is required to be subjected to distance compensation treatment to obtain correct tree height, as shown in fig. 1, when the furthest shadow point of the three-dimensional model reaches the Z point, the obtained height of the three-dimensional model is the tree height, the furthest shadow point Q of the tree is known in actual operation, the shadow of the three-dimensional model is overlapped with the furthest shadow point Q of the tree, and the obtained model height h m Is smaller than the true height H of the tree s The tree height needs to be compensated, so that the real tree height is obtained, and the compensation principle is shown in figure 1.
The true shade length of the tree is (I 1 +X L ) By means of the height h of the model m And the sun altitude angle alpha can calculate the shadow length I of the model 1 The compensation distance X can be obtained according to the distance from the center of the crown to the edge of the crown L The actual tree height can be calculated by using the trigonometric function, and the specific process is as follows:
δ(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)
+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t= (true solar time-12) ×15° (5)
True solar time = flat solar time + true solar time difference (6)
I 1 ＝h m /tan(α) (7)
H s ＝(I 1 +X L )×tan(α) (8)
Wherein alpha is the solar altitude angle,
for geographic latitude, delta represents solar declination, and t represents time angle; b is the angle of earth revolution from 1 month 1 day to the calculation day, the calculation formula is b=2×pi× (day-1)/365, day is the number of days from 1 month 1 day to the calculation day each year, pi is the circumference ratio, and deg represents the angle; real solar time is a time system formulated according to real solar days; the solar time is Beijing time; the true solar time difference is the time difference between the calculated ground and the Beijing time by taking the Beijing time as a marker post; i 1 For the model shadow length, h m Is the height of the model; h s X is the true height of the tree L To compensate for the distance.
Based on the extracted composite graph of the crown and the power transmission line, a shortest distance algorithm for searching the power transmission line by using a tree vertex ring and a shortest distance algorithm for searching the crown by using the power transmission line are provided.
3) Tree and transmission line distance algorithm
The principle diagram of the horizontal distance algorithm from the bottom end of the tree to the transmission line is shown in fig. 2. Firstly, preprocessing the edges of the crowns and the power lines, and distinguishing different crowns and power lines by setting different gray values for different crowns and power lines. Then with crown apex O (x 0 ,y 0 ) The edge point of the crown closest to the crown is the radius r as the center of the circle d (unit: pixels) making a circle, the round equation is:
(x-x 0 ) 2 +(y-y 0 ) 2 ＝r d 2 (9)
with (r) d +1) (unit: pixels) as a new radius, continuing to make a circle by taking the crown vertex as the center of a circle, wherein the equation is as follows:
(x-x 0 ) 2 +(y-y 0 ) 2 ＝(r d +1) 2 (10)
the part of the circular ring formed between the two circles is a search area, and the search area meets the requirement
r d 2 <＝(x-x 0 ) 2 +(y-y 0 ) 2 <＝(r d +1) 2 (11)
If no satisfactory point exists in the search area, the radius of the inner circle and the outer circle is increased by 1 pixel to form a new circular ring, and the search is continued until the satisfactory pixel point is searched. All the pixel points meeting the requirements in the circular ring are connected with the circle center (x 0 ,y 0 ) Obtaining the distance (d) by performing distance calculation 1 ,d 2 ,...,d n ) Find the minimum distance d from it s (Unit: pixels) as the minimum horizontal distance of the tree line. The distance formula is:
wherein, (x) i‘ ,y i’ ) Is any point in the ring that meets the requirements, where i' =1, 2,.. i’ Is the horizontal distance from the point to the tree's apex.
The shortest distance d calculated according to the resolution of the image s The shortest distance D (unit: meter) from the tree to the transmission line is converted into the actual shortest distance D (unit: meter) from the tree to the transmission line, and the conversion formula is as follows:
D＝d s x resolution (13)
The shortest distance D from tree to transmission line is combined with the transmission line height M (unit: meter) and the true height H of tree s (unit: meter), can calculate whether trees break and can cause the threat to the power transmission line, the computational formula is:
wherein S is the linear distance (in meters) from the bottom end of the tree to the power transmission line, and W is the nearest distance (in meters) from the power transmission line when the tree breaks.
The algorithm uses a circular ring as a search area so that all pixels are not repeatedly traversed.
4) Crown and transmission line distance algorithm
To calculate the crown line distance, the crown edge point closest to the power line needs to be accurately found, if the distance between the edge point and the power line is calculated one by one, the calculation is complex and time is consumed, in order to reduce the calculation time and accurately obtain the crown line distance, a method for searching the crown edge point by using the mobile power line is proposed, and a schematic diagram is shown in fig. 3.
According to the minimum horizontal distance d of the tree line s Obtaining the crown vertex O (x) 0 ，y 0 ) Nearest point P 1 (x 1 ，y 1 ) The shortest distance theorem from point to straight line can obtain line segment OP 1 Perpendicular to the transmission line L 1 ，P 1 Is foot drop. According to the O point and P 1 Coordinate of point can obtain line segment OP 1 Slope k of (2) 1 The power line L can be obtained by the product of the vertical slopes of two straight lines being-1 1 Slope k of (2) 2 Transmission line L 1 And line segment OP 1 The linear equation of (2) is:
the power line L 1 Along line segment OP 1 Shifting one pixel unit downward in the direction to obtain a slope k 2 Straight line L of (2) 2 Straight line L 2 And line segment OP 1 Intersecting at point P 2 Let P be 2 Is (x) 2 ,y 2 ) The minimum horizontal distance of the tree line is d s (Unit: pixel), thus OP 2 Length of (d) s -1) (unit: pixel) will P 2 The point coordinates are taken into formula (12) and formula (15) and calculated to obtain:
by P 2 Point coordinates and straight line L 2 Slope of (2)Obtaining a straight line L 2 Equation (d). The power line L 1 And straight line L 2 The strip-shaped area between the two is used as a searching area, and if no point meeting the requirement exists in the searching area, the power line L 1 And straight line L 2 All along OP 1 The method includes the steps of translating 1 pixel downwards to form a new searching area, and continuing searching until the pixel points meeting the requirements are searched for the first time. As shown by a curve JK in fig. 3, all the pixel points meeting the requirements are calculated with the power transmission line L by using a point-to-line distance formula 1 The formula is as follows:
where U, V, G is the coefficient of the linear equation, (x) s' ,y s' ) For any target point coordinate to be calculated, s' e [1, n]，f s' For any target point to be calculated to the power line L 1 The smallest distance F (unit: pixel) from the power line to the crown edge is the smallest distance F from the power line to the crown edge, and the smallest distance F from the power line to the crown edge is multiplied by the resolution to obtain the actual shortest horizontal distance F from the power line to the crown edge s (unit: meters).
5) Early warning criterion
The early warning relation between trees and the power transmission line is divided into three types: (1) extremely dangerous, and the need to clear tree barriers is urgent; (2) moderate danger, need to clear the tree obstacle recently; (3) safety, and no attention is needed recently.
According to the design specification of the 110 kV-750 kV overhead transmission line, the maximum windage distance of the 500kV transmission line is 8.5 meters, the maximum sag distance is 9 meters, the safety distance to the ground is 11 meters, 28 insulators are provided, each insulator is about 15 cm, so the ground clearance of the 500kV transmission line is at least: 11+9+28 x 0.15=24.2 (unit: meter). The position relationship between the tree and the power transmission line is divided into two types:
(1) When the tree is below the transmission line, whether the transmission line is threatened by the tree, the transmission line height M and the true tree height H s Related to;
a)M-H s <9, issuing a first-level early warning when extremely dangerous;
b)9<M-H s <12, moderately dangerous, issuing a second-level early warning;
c)M-H s >12, safety, no early warning is issued.
(2) When the tree is on the two sides of the transmission line, whether the transmission line is threatened or not and the true height H of the tree s Height M of the transmission line, shortest distance W from the transmission line when the tree breaks, shortest horizontal distance F from the transmission line to the crown edge s All have a relationship;
a)F s <8.5 and H s >When M-2 or W is less than or equal to 0, the danger is extremely high, and a first-level early warning is issued;
b)F s >11.5 and W>3 or H s <M-9, safety and no early warning are issued;
c) Other conditions are moderate dangers, and secondary early warning is issued.
And monitoring the flashing hidden danger of the power transmission line tree according to the implementation mode and the flow of fig. 4.
What is not described in detail in this specification is prior art known to those skilled in the art.
Claims (6)
1. The method for monitoring the potential flashover hazard of the power transmission line based on the satellite optical image is characterized by comprising the following steps of:
1) 4 wave bands of the satellite image are analyzed by an optimal exponential method, wherein the 1 wave band, the 2 wave band, the 3 wave band and the 4 wave band correspond to the following steps: blue light wave band, green light wave band, red light wave band and near infrared wave band, 4 wave bands have four kinds of wave band combinations, are respectively: 1. 2,3 wave bands, 1,2, 4 wave bands, 1, 3, 4 wave bands, 2,3, 4 wave bands, respectively calculating the indexes of the wave band combinations, selecting the wave band combination with the largest index as an experimental wave band, then generating a false color image of the experimental wave band by using ENVI software, carrying out normalized vegetation index treatment and mask treatment on the false color image, and segmenting out a crown area image by morphological filtering and a watershed marking algorithm;
2) Coarse classification is carried out on the power transmission line images in the satellite images by using a maximum likelihood method, and the classified power transmission line images are manually classified for the second time in ENVI class to obtain power transmission line images;
3) Intercepting a tree satellite picture in a satellite image, then importing the tree satellite picture into a sktch Up software, constructing an external rectangle of the tree satellite picture in the tree satellite picture, setting the time and place of the tree satellite picture in the sktch Up software, adjusting the height of the external rectangle to establish a three-dimensional model of the external rectangle of the tree contour, enabling the shadow highest point of the three-dimensional model to coincide with the shadow highest point of the tree satellite picture, measuring the height of the three-dimensional model, obtaining pseudo tree height through proportional conversion, and calculating by adopting a distance compensation method to obtain the tree height after compensation correction;
4) Synthesizing the crown area image obtained in the step 1) and the power transmission line image obtained in the step 2), determining the shortest distance from the tree to the power transmission line by adopting a circular ring search method according to the synthesized image of the crown area image and the power transmission line image, and determining the shortest distance from the power transmission line to the crown edge by adopting a strip area search method;
5) Dividing the early warning of the tree flashover hidden trouble of the power transmission line into the following steps according to the shortest distance from the tree to the power transmission line and the shortest distance from the power transmission line to the edge of the crown, which are obtained in the step 4): extremely dangerous, and the need for removing tree barriers is urgent; medium danger, need to clear the tree obstacle recently; safety, no attention is required in the recent time; thus giving an early warning strategy.
2. The method for monitoring the tree flash hidden trouble of the power transmission line based on the satellite optical image as claimed in claim 1, wherein the calculation formula of the index of the band combination in the step 1) is as follows:
wherein OIF is the index of band combination, S i I=1, 2,3, r, the standard deviation of the i-th band in the band combination jk And r is the number of combinations of different wave bands in the wave band combination.
3. The method for monitoring the tree flash hidden trouble of the power transmission line based on the satellite optical image according to claim 1, wherein the specific process of calculating the corrected tree height by adopting the distance compensation method in the step 3) is as follows:
the true shade length of the tree is I 1 +X L By using the height h of the three-dimensional model m And calculating the shadow length I of the three-dimensional model by the solar altitude angle alpha 1 Obtaining a compensation distance X according to the distance from the center of the crown to the edge of the crown L Then calculating to obtain the tree real tree height H by using trigonometric function s The calculation formula is as follows:
δ(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t= (true solar time-12) ×15° (5)
True solar time = flat solar time + true solar time difference (6)
I 1 ＝h m /tan(α) (7)
H s ＝(I 1 +X L )×tan(α) (8)
Wherein alpha is the solar altitude angle,
for geographic latitude, delta represents solar declination, and t represents time angle; b is the angle of earth revolution from 1 month 1 day to the calculation day, the calculation formula is b=2×pi× (day-1)/365, day is the number of days from 1 month 1 day to the calculation day each year, pi is the circumference ratio, and deg represents the angle; real solar time is a time system formulated according to real solar days; the solar time is Beijing time; the true solar time difference is the time difference between the satellite image shooting place and the Beijing time by taking the Beijing time as a marker post; i 1 Is the shadow length of the three-dimensional model, h m For three-dimensional model height, H s X is the true height of the tree L To compensate for the distance.
4. The method for monitoring the potential flashover hazard of the power transmission line based on the satellite optical image according to claim 3, wherein the specific process of the circular ring search method in the step 4) is as follows:
firstly, preprocessing the edge of a crown and a power transmission line, distinguishing different crowns and power transmission lines by setting different gray values for different crown edges and power transmission lines, and then using crown vertices O (x) 0 ,y 0 ) The edge point of the crown closest to the crown vertex is the radius r d Making a circle with radius r d Is in pixels, the circular equation is:
(x-x 0 ) 2 +(y-y 0 ) 2 ＝r d 2 (9)
by r d +1 as new radius, with crown vertex O (x 0 ,y 0 ) Continuing to make a circle for the center of the circle, wherein the equation of the circle is as follows:
(x-x 0 ) 2 +(y-y 0 ) 2 ＝(r d +1) 2 (10)
the part of the circular ring formed between the two circles is a search area, and the search area meets the requirement
r d 2 <＝(x-x 0 ) 2 +(y-y 0 ) 2 <＝(r d +1) 2 (11)
If no satisfactory points exist in the search area, the radius of the inner and outer circles is increased by 1 pixel to form a new circular ring to continue searching until satisfactory pixel points are searched, and all satisfactory pixel points in the circular ring are subjected to distance calculation with the circle center to obtain a distance (d 1 ,d 2 ,...,d n ) Find the minimum distance d from it s D as the minimum horizontal distance of the tree line s The unit of (2) is pixel, and the calculation formula of the distance is:
wherein, (x) i‘ ,y i’ ) Is any point in the ring that meets the requirements, where i' =1, 2,.. i’ A horizontal distance from the point to the crown vertex;
minimum horizontal distance d of tree line according to resolution of image s The shortest horizontal distance D from the tree to the transmission line is converted into the actual tree to the transmission line, the unit is meter, and the conversion formula is as follows:
D＝d s x resolution (13)
The shortest horizontal distance D of the tree to the transmission line is combined with the transmission line height M and the true height H of the tree s Whether the tree breaks and threatens the power transmission line is calculated, and the calculation formula is as follows:
wherein S is the linear distance from the bottom end of the tree to the power transmission line, the unit is meter, W is the nearest distance from the power transmission line when the tree breaks, and the unit is meter, wherein the height M of the power transmission line and the true height H of the tree s The units of (a) are all meters.
5. The method for monitoring the potential tree flashover hazard of the power transmission line based on the satellite optical image according to claim 4, wherein the specific process of the strip-shaped area searching method in the step 4) is as follows:
according to the minimum horizontal distance d of the tree line s Obtaining the crown vertex O (x) 0 ，y 0 ) Nearest point P 1 (x 1 ，y 1 ) Obtaining a line segment OP from the shortest distance theorem from point to straight line 1 Perpendicular to the transmission line L 1 ，P 1 For foot drop, according to crown vertices O and P 1 The coordinates of the points give line segments OP 1 Slope k of (2) 1 The power line L is obtained by the product of the vertical slopes of the two straight lines being-1 1 Slope k of (2) 2 Transmission line L 1 And line segment OP 1 The linear equation of (2) is:
the power line L 1 Along line segment OP 1 Shifting one pixel unit downward in the direction to obtain a slope k 2 Straight line L of (2) 2 Straight line L 2 And line segment OP 1 Intersecting at point P 2 Let P be 2 Is (x) 2 ,y 2 ) The minimum horizontal distance of the tree line is d s Thus OP 2 Length d of (2) s -1, P 2 The point coordinates are taken into the formulas (12) and (15), and calculated to obtain:
by P 2 Point coordinates and straight line L 2 Slope of (2) to obtain a straight line L 2 Equation, power line L 1 And straight line L 2 The strip-shaped area between the two is used as a searching area, and if no point meeting the requirement exists in the searching area, the power transmission line L is used for 1 And straight line L 2 All along OP 1 Translating 1 pixel downwards in the direction to form a new search area, continuing to search until the pixel points meeting the requirements are searched for the first time, and calculating all the pixel points meeting the requirements and the power transmission line L by using a point-to-straight line distance formula 1 The formula is as follows:
where U, V, G is the coefficient of the linear equation, (x) s' ,y s' ) For any target point coordinate to be calculated, s' e [1, n]，f s' For any target point to be calculated to the power line L 1 Finding the minimum distance F from the power line to the crown edge, obtaining the minimum distance F from the power line to the crown edge in pixels, and multiplying the minimum distance F from the power line to the crown edge by the resolution to obtain the actual minimum horizontal distance F from the power line to the crown edge s The unit is meter.
6. The method for monitoring the potential flashover hazard of the power transmission line based on the satellite optical image according to claim 5, wherein the specific process of the step 5) is as follows:
the positional relationship between trees and transmission lines is divided into two types:
(1) When the tree is under the transmission line, the transmission line is threatened by the tree, the transmission line height M and the true tree height H s Related to;
a)M-H s <9, issuing a first-level early warning when extremely dangerous;
b)9<M-H s <12, moderately dangerous, issuing a second-level early warning;
c)M-H s >12, safety and no early warning is issued;
(2) When the tree is on the two sides of the transmission line, whether the transmission line is threatened or not and the true height H of the tree s Height M of the transmission line, shortest distance W from the transmission line when the tree breaks, shortest horizontal distance F from the transmission line to the crown edge s Related to;
a)F s <8.5 and H s >When M-2 or W is less than or equal to 0, the danger is extremely high, and a first-level early warning is issued;
b)F s >11.5 and W>3 or H s <M-9, safety and no early warning are issued;
c) Other conditions are moderate dangers, and secondary early warning is issued.
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