Fiber Optic Implantation-Based Detection and Visualization Method for Water Ingress in Filling Layers

Abstract

The present invention discloses a method for detecting water ingress in a filling layer based on fiber optic implantation and visual display. In this method, multiple linear fiber optic temperature sensors are internally layered at different depths in the filling layer of the cable, and the temperature detection points of the linear fiber optic temperature sensors are sorted and numbered. Then, the data of each temperature detection point are collected, and the temperature detection point is compared with the surrounding temperature detection points at the same depth. The temperature difference is calculated and compared with the preset temperature difference levels to calibrate the water ingress position, area, and degree of water ingress at the node. Then, based on the comparison of the temperature detection points in adjacent layers, the water ingress depth is calibrated, and the water ingress situation is visually displayed. The present invention improves the reliability and timeliness of cable water ingress monitoring, reflects the degree of water ingress in real time, provides decision-making references for emergency repairs, and has high social and economic benefits for ensuring the stability of power grid operation and the reliable operation of cables. At the same time, the water ingress can also be visually displayed.

Description

Technical Field

[0001] The present invention relates to cable detection technology, and in particular to a filling layer water ingress detection and visual display method based on optical fiber implantation. Background Art

[0002] As power cables account for an increasing proportion in urban power transmission and distribution networks, their operational safety is a key issue that requires attention. Since most power cables are laid underground, failures are common in complex operating environments, and most power cable accidents are caused by water ingress into the cables. If water ingress into the cables is not promptly treated, water dendrites will gradually form on the main insulation of the cables, and later develop into electrical dendrites, which will reduce the insulation of the cables and cause breakdown and other failures, resulting in power outages and serious losses to the national economy.

[0003] Most of the current methods for judging and locating water ingress in cables are based on offline insulation resistance tests, DC withstand voltage and leakage current tests. They can only determine whether water has ingressed, but cannot locate the specific location and scope of water ingress. Such methods need to be performed after power is cut off, which will interrupt the power supply to users, and the test method will affect the performance of the cable, which is highly controversial. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above existing technologies and provide a filling layer water ingress detection and visualization display method based on optical fiber implantation. This filling layer water ingress detection and visualization display method based on optical fiber implantation can detect the water ingress of the cable in a timely manner and determine the coverage and depth of the water ingress.

[0005] The purpose of the present invention is achieved through the following technical solution: The method for detecting and visually displaying water ingress into a filling layer based on optical fiber implantation comprises the following steps:

[0006] S1. Multiple linear optical fiber temperature sensors are built into the filling layer of the cable. All the linear optical fiber temperature sensors are divided into two layers. The linear optical fiber temperature sensors of each layer are evenly distributed relative to the circumference of the cable core, and the linear optical fiber temperature sensors corresponding to each layer are distributed radially.

[0007] S2. Set N temperature detection points on each linear optical fiber temperature sensor, and the distance between two adjacent temperature detection points on each linear optical fiber temperature sensor is D; let the number of layers of linear optical fiber temperature sensors be n, where n=2, and the number of linear optical fiber temperature sensors in each layer is m, and sort and number the temperature detection points;

[0008] S3. After the cable enters the stable operation state, collect the data of each temperature detection point, make the lowest temperature point the most likely water inlet point, and then determine whether the data corresponding to the lowest temperature point is within the temperature range. If the data of the temperature detection point is within the temperature range, then this temperature detection point is the water inlet point, and a water inlet range is delimited around this point;

[0009] S4. Based on the water inlet point obtained in S3, calculate the water inlet depth and visually display the water inlet situation.

[0010] The specific process of marking the water inlet position and the water inlet range in step S3 is as follows:

[0011] S3-1. Denote the temperature data detected by the temperature detection point as T (x，i，k) , where x is the number of layers, 0 < x ≤ 2; i is the number of columns, 0 < i ≤ m; k is the number of digits, 0 < k ≤ N; let the temperature range be (T min , T max );

[0012] S3-2. Judge the temperature data T (2，i，k) of the outermost layer, and make the temperature detection point with the lowest temperature in the outermost layer the most likely water inlet point:

[0013] When the measured temperature T (2，i，k) ≥T max , then this position is normal;

[0014] When the measured temperature T (2，i，k) is within (T min , T max ), then compare the temperatures between T (2，i，k) and T (2，i，k+1) , T (2，i，k-1) , T (2，i+1，k) , T (2，i-1，k) in turn, and mark the minimum value T min(2，i，k) as the water inlet position T’ 0(2，i0，k0) ;

[0015] S3-3. Delimit the water inlet range:

[0016] S3-3-1. Taking the point at T’ 0(2，i0，k0) as the reference point, judge whether the temperature data T (2，i0，k0-1) , T (2，i0-1，k0) , T (2，i0，k0+1) and T (2，i0+1，k0) of the 4 adjacent directions are within (T min , T max );

[0017] S3-3-2. Mark the ones within (T min , T max) The temperature detection point inside is also the water inlet point, and then using this water inlet point as the reference point, repeat S3-3-1 until there are no points within (T min , T max ) among the adjacent temperature detection points of all water inlet points;

[0018] S3-3-3. Connect all the water inlet points. The area enclosed by the connection lines of each water inlet point is the water inlet range.

[0019] Calculate the water inlet depth and visually display the water inlet situation as follows:

[0020] S4-1. Calculate the temperature difference △T between the water inlet point T’ n(2，in，kn) and its radially inner temperature measurement point T (1，in，kn) , and judge the temperature difference △T:

[0021] When △T = 0, connect these two points;

[0022] When △T is in the interval (T max - T min , 0), starting from the outer water inlet point T’, n(2，in，kn) draw a line segment towards the corresponding inner temperature measurement point T (1，in，kn) . The length of the line segment is H = h * △T / (T max - T min ), where H represents the water inlet depth here, and h is the distance between the inner and outer layer of linear optical fiber temperature sensors;

[0023] S4-2. Repeat S4-1 for each water inlet point on the outermost layer;

[0024] S4-3. Color the line segments obtained from S3, S4-1 and S4-2 to visually display the water inlet situation.

[0025] The number m of linear optical fiber temperature sensors in each layer is 4 to 16.

[0026] The present invention has the following advantages compared with the prior art:

[0027] The present invention sets at least two layers of linear optical fiber temperature sensors in the filling layer of the cable, and compares the temperatures detected by adjacent temperature detection points to realize real-time detection, positioning of the water inlet position and visual display of the water inlet situation.

[0028] The present invention installs linear optical fiber temperature sensors in the filling layer of the cable. By comparing the temperatures of each node with each other, the visualization is enhanced, the water inlet position can be located, and the water inlet depth can also be further determined.

[0029] The method of the present invention improves the reliability and timeliness of cable water ingress monitoring, and has high social and economic benefits for ensuring the stability of power grid operation and the reliable operation of cables. Description of the Drawings

[0030] Figure 1 is a flowchart of the method for detecting water ingress in the filling layer and visualizing the display based on optical fiber implantation according to an embodiment of the present invention.

[0031] Figure 2 is a schematic diagram of a cable with a linear optical fiber temperature sensor built-in.

[0032] Figure 3 is a single-layer water ingress marking diagram of the present invention.

[0033] Figure 4 is a cross-sectional view of the visualization of water ingress at the cable temperature measurement node of the present invention.

[0034] Figure 5 is a diagram showing the depth of the cable water ingress area of the present invention.

[0035] Among them, 1 is the cable, 2 is the linear optical fiber temperature sensor, 3 is the filling layer, and 4 is the cable core. Detailed Embodiment

[0036] The present invention will be further described below in conjunction with the drawings and embodiments.

[0037] As Figure 1 shown, the method for detecting water ingress in the filling layer and visualizing the display based on optical fiber implantation includes the following steps:

[0038] S1. A plurality of linear optical fiber temperature sensors are built into the filling layer of the cable. All the linear optical fiber temperature sensors are divided into two layers. The linear optical fiber temperature sensors in each layer are evenly distributed around the circumference of the cable core, and the corresponding linear optical fiber temperature sensors in each layer are distributed radially, as Figure 2 shown. Each layer has 12 linear optical fiber temperature sensors. The 12 linear optical fiber temperature sensors in each layer are evenly distributed around the circumference of the cable core, and the linear optical fiber temperature sensors in the two layers correspond one by one, that is, the corresponding linear optical fiber temperature sensors in the two layers are distributed radially.

[0039] S2. Set N temperature detection points on each linear optical fiber temperature sensor. The distance between two adjacent temperature detection points on each linear optical fiber temperature sensor is D; let the number of layers of the linear optical fiber temperature sensor be n, where n = 2, and the number of linear optical fiber temperature sensors in each layer is m. Sort and number the temperature detection points; as Figure 2As shown, to ensure the accuracy of the measurement conclusion, in this embodiment, m = 12, that is, 12 straight fiber optic temperature sensors are used for each layer; the size of D is 10 cm to 20 cm. The sorting and numbering of the temperature detection points are as follows: three coordinates of the number of layers, the number of columns, and the number of digits are adopted. Among them, the number of layers is the number of layers of the two-layer straight fiber optic temperature sensor, sorted from the outside to the inside of the cable, that is, the outermost straight fiber optic temperature sensor is the first layer; the number of columns is the number of straight fiber optic temperature sensors that surround the cable core in the clockwise direction of the cross-section. In this embodiment, the number of columns is 12 in total; the number of digits is along the axial direction of the straight fiber optic temperature sensor. Let the number of digits be x, the number of columns be i, and the number of digits be k to obtain the coordinates (x, i, k) of each temperature detection point.

[0040] S3. After the cable enters the stable operation state, collect the data of each temperature detection point, let the lowest temperature point be the most likely water inlet point, and then determine whether the data corresponding to the lowest temperature point is within the temperature range. If the data of the temperature detection point is within the temperature range, then this temperature detection point is the water inlet point, and a water inlet range is delimited around this point;

[0041] The specific process of marking the water inlet position and the water inlet range in step S3 is as follows:

[0042] S3-1. Denote the temperature data detected by the temperature detection point as T (x，i，k) , where x is the number of layers, 0 < x ≤ 2; i is the number of columns, 0 < i ≤ m; k is the number of digits, 0 < k ≤ N; let the temperature range be (T min , T max ); Since the cable operation will cause the filling layer to heat up, when there is no water inlet accident, the temperature detection results of each point in the filling layer are theoretically equal and are a stable temperature value; when a water inlet accident occurs, due to the heat absorption of water, the temperature at the water inlet will decrease. Therefore, there is a temperature range in the filling layer: the highest temperature is the temperature T max caused by cable heating during normal operation, and the lowest temperature is the room temperature T min when the water completely penetrates the filling layer. When the water does not completely penetrate the filling layer, the temperature at this place will be within the range of (T max , T min ).

[0043] S3-2. Judge the temperature data T (2，i，k) of the outermost layer, and let the temperature detection point with the lowest temperature in the outermost layer be the most likely water inlet point:

[0044] When the measured temperature T (2，i，k) ≥ T max , then this position is normal;

[0045] When the measured temperature T (2，i，k) is in (T min , Tmax ) within, then compare them with T (2，i，k) and T (2，i，k+1) , T (2，i，k-1) , T (2，i+1，k) , T (2，i-1，k) in sequence, mark the minimum temperature T min(2，i，k) among them as the water inlet position T’ 0(2，i0，k0) ;

[0046] S3-3. Define the water inlet range:

[0047] S3-3-1. Taking the point at T’ 0(2，i0，k0) as the reference point, judge whether the temperature data T (2，i0，k0-1) , T (2，i0-1，k0) , T (2，i0，k0+1) and T (2，i0+1，k0) in 4 adjacent directions are within (T min , T max );

[0048] S3-3-2. Mark the temperature detection points within (T min , T max ) as water inlet points, and then repeat S3-3-1 with this water inlet point as the reference point until there are no points within (T min , T max ) among the adjacent temperature detection points of all water inlet points;

[0049] S3-3-3. Connect all the water inlet points, and the area enclosed by the connection lines of each water inlet point is the water inlet range, as shown in Figure 3 .

[0050] S4. Based on the water inlet points obtained in S3, calculate the water inlet depth and visually display the water inlet situation.

[0051] Calculate the water inlet depth and visually display the water inlet situation as follows:

[0052] S4-1. Calculate the temperature difference △T between the water inlet point T’ n(2，in，kn) and its radially inner layer temperature measurement point T (1，in，kn) , and judge the temperature difference △T: According to whether there is water inlet and the water penetration situation, the radial temperature measurement difference △T of the filling layer must be within the interval (T max - T min , 0). Among them, when the temperature difference is T max - T min , it means that the outer layer is inlet with water and the inner layer is still dry, and the inner and outer layers have not been penetrated; when the temperature difference is 0, it means that the inner and outer layers are completely penetrated; when the temperature difference is within (T max - T min, when it is (0, 0), it means that water has entered between the inner and outer layers at this time, but it has not completely penetrated, and the degree of water intake increases linearly as the temperature difference decreases.

[0053] When △T = 0, connect these two points;

[0054] When △T is in the interval (T max -T min , 0), starting from the water inlet point T' of the outer layer n(2，in，kn) , draw a line segment towards the corresponding temperature measurement point T of the inner layer (1，in，kn) , and the length of the line segment is H = h * △T / (T max -T min ), where H represents the water intake depth here, and h is the distance between the linear optical fiber temperature sensors of the inner and outer layers;

[0055] S4-2. Repeat S4-1 for each water inlet point of the outermost guide;

[0056] S4-3. Color the line segments obtained in S3, S4-1, and S4-2 to visually display the water intake situation, as shown in Figure 4 and Figure 5 shown.

[0057] The above specific implementation manners are the preferred embodiments of the present invention and cannot limit the present invention. Any other changes or other equivalent replacement methods made without departing from the technical solution of the present invention are included in the protection scope of the present invention.

Claims

1. A method for detecting water ingress in a filling layer based on optical fiber implantation and visual display, characterized in that It includes the following steps: S1. A plurality of linear optical fiber temperature sensors are built into the filling layer of the cable. All the linear optical fiber temperature sensors are divided into two layers. The linear optical fiber temperature sensors in each layer are evenly distributed circumferentially with respect to the core of the cable, and the corresponding linear optical fiber temperature sensors in each layer are distributed radially; S2. Set N temperature detection points on each linear optical fiber temperature sensor. The distance between two adjacent temperature detection points on each linear optical fiber temperature sensor is D; Let the number of layers of the linear optical fiber temperature sensors be n, where n = 2, and the number of linear optical fiber temperature sensors in each layer is m. Sort and number the temperature detection points; S3. After the cable enters the stable operation state, collect the data of each temperature detection point. Let the lowest temperature point be the most likely water inlet point, and then determine whether the data corresponding to the lowest temperature point is within the temperature range. If the data of the temperature detection point is within the temperature range, then this temperature detection point is the water inlet point, and a water inlet range is delimited around this point; S4. Based on the water inlet point obtained in S3, calculate the water inlet depth and visually display the water inlet situation; The calculation of the water inlet depth and the visual display of the water inlet situation are as follows: S4-1. Calculate the water inlet point T' n(2，in，kn) and its temperature difference ΔT with the radially inner temperature measurement point T (1，in，kn) , and judge the temperature difference ΔT: When △T = 0, connect these two points; When △T is in the interval (T max - T min , 0), starting from the water inlet point T' of the outer layer n(2，in，kn) , draw a line segment towards the corresponding temperature measurement point T of the inner layer (1，in，kn) . The length of the line segment is H = h * △T / (T max - T min ). H represents the water inlet depth here, h is the distance between the inner and outer layer linear optical fiber temperature sensors; i is the number of columns, 0 < i ≤ m; k is the number of digits, 0 < k ≤ N; let the temperature interval be (T min , T max ); S4-2. Repeat S4-1 for each water inlet point in the outer layer; S4-3. Color the line segments obtained in S3, S4-1 and S4-2 to visually display the water inlet situation.

2. The method for detecting water ingress and visual display of the filling layer based on optical fiber implantation according to claim 1, wherein, The specific process of marking the water inlet position and delimiting the water inlet range in step S3 is as follows: S3-1. Denote the temperature data detected by the temperature detection points as T (x，i，k) , where x is the number of layers and 0 < x ≤ 2; S3-2. Judge the temperature data T of the outermost layer (2，i，k) to make the temperature detection point with the lowest temperature in the outermost layer the most likely water inlet point: When the measured temperature T (2，i，k) ≥ T max , then this position is normal; When the measured temperature T (2，i，k) is within (T min , T max ), then compare the temperatures between T (2，i，k) and T (2，i，k+1) , T (2，i，k-1) , T (2，i+1，k) , T (2，i-1，k) in sequence, and mark the minimum temperature T min(2，i，k) as the water inlet position T’ 0(2，i0，k0) ; S3-3. Delimit the water inlet range: S3-3-1. Taking T’ 0(2，i0，k0) as the reference point, determine whether the temperature data T (2，i0，k0-1) , T (2，i0-1，k0) , T (2，i0，k0+1) and T (2，i0+1，k0) in the four adjacent directions are within (T min , T max ); S3-3-2. The temperature detection points marked within (T min , T max ) are also the water inlet points. Then, using this water inlet point as the reference point, repeat S3-3-1 until there are no points within (T min , T max ) among the adjacent temperature detection points of all the water inlet points; S3-3-3. Connect all the water inlet points. The area enclosed by the connection lines of each water inlet point is the water inlet range.

3. The method for detecting water ingress and visual display of the filling layer based on optical fiber implantation according to claim 1, wherein: The number m of the linear optical fiber temperature sensors in each layer is 4 to 16.

Images