Method for rapid detection of water ingress into high voltage cable grounding box based on shield current
Patent Information
- Application Number
- CN202611113158.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-26
- Publication Date
- 2026-10-30
AI Technical Summary
[0005]本发明旨在提供一种高压电缆接地箱进水快速检测方法，以解决现有技术中检测滞后、灵敏度低、依赖人工开箱等问题
[0018]与现有技术相比，本发明具有显著的有益效果，
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Figure CN123008142A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-voltage cable sheath testing, and more specifically, to a rapid detection method for water ingress into high-voltage cable grounding boxes based on sheath grounding current. Background Technology
[0002] In high-voltage power systems, the operational safety of cross-connected cables is directly related to the stability and reliability of the power grid. The cross-connection grounding box, as a key device for realizing the cross-connection of the metal sheaths of high-voltage cables and installing sheath protectors, directly affects the safety and stability of the cable lines. In actual operation, due to aging sealing structures, limited protection levels, and insufficient drainage, the grounding box is susceptible to rainwater or groundwater intrusion. Once water enters, the insulation environment inside the box deteriorates, insulation resistance decreases, and leakage paths may form between the sheath protector, connecting conductors, and terminals, leading to abnormal sheath grounding circuits, unbalanced current distribution, and malfunctioning protectors. Simultaneously, prolonged moisture exposure accelerates metal corrosion and insulation aging, reducing the sheath's overvoltage protection capability, and in severe cases, may cause sheath damage or even main insulation failure.
[0003] In existing technologies, water ingress detection of cable grounding boxes mainly relies on manual inspections and water immersion sensors. However, these methods suffer from drawbacks such as long detection cycles, high labor costs, difficulty in achieving real-time monitoring, and insufficient sensitivity to early water ingress defects. Furthermore, they are susceptible to external interference in complex environments, making it difficult to fully guarantee the reliability and accuracy of the detection results, and thus failing to meet the rapid response requirements for the safe operation and maintenance management of high-voltage cables. Therefore, there is an urgent need for a method that can quickly and accurately reflect the water ingress status inside cross-connected grounding boxes, especially a technical solution that can achieve online, non-invasive detection based on changes in the cable sheath grounding current, thereby effectively preventing insulation damage and power grid safety hazards caused by water ingress into the grounding box.
[0004] Against this technical background, the present invention proposes a rapid detection method for water ingress in high-voltage cable grounding boxes based on sheath grounding current. By monitoring abnormal changes in sheath grounding current in real time, the method can quickly identify water ingress in the grounding box, providing a reliable, online, and non-invasive technical means for the operation and maintenance of high-voltage cables. Summary of the Invention
[0005] This invention aims to provide a rapid detection method for water ingress in high-voltage cable grounding boxes, addressing the problems of detection lag, low sensitivity, and reliance on manual box opening in existing technologies. The method involves installing current transformers at both ends of the cable sheath to collect the amplitude and phase characteristics of the sheath current, and establishing a recognition model based on the XGBoost algorithm to achieve rapid and accurate identification of water ingress defects in the grounding box. This method possesses online, non-invasive detection capabilities, detecting abnormalities in the sheath grounding circuit and potential water ingress risks without damaging the cable structure. It effectively prevents insulation performance degradation and sheath damage, improving the automation level of high-voltage cable operation and maintenance and the safety and reliability of the power grid.
[0006] To achieve the above objectives, this application provides the following technical solution:
[0007] This application provides a rapid detection method for water ingress into a high-voltage cable grounding box based on the sheath grounding current, including the following steps:
[0008] Establish a calculation model for the sheath current of water entering the cross-interconnected grounding box of high-voltage cables;
[0009] An equivalent simulation of the water ingress defect in the cross-connected grounding box was performed.
[0010] The current response at both ends of the cable sheath was calculated under different degrees of water ingress defects.
[0011] Construct a sample set for identifying water ingress defects in grounding boxes;
[0012] A model for identifying water ingress defects in grounding boxes was established using the XGBoost algorithm.
[0013] The specific steps for establishing the sheath current calculation model for water ingress into the cross-interconnected grounding box of high-voltage cables are as follows: based on the actual cable line structure and sheath grounding circuit parameters, the sheath current calculation relationship under the cross-interconnected state is constructed to obtain the current amplitude and phase distribution characteristics of the beginning and end of the metal sheath of each cable section under normal operating conditions. This model can reflect the influence of cable load current, grounding resistance, etc. on sheath current, providing a basis for subsequent water ingress defect simulation and sample generation.
[0014] The equivalent simulation of the water ingress defect in the cross-interconnected grounding box is specifically carried out by adjusting the grounding resistances R3, R4, and R5 in cross-interconnected box C1 and the grounding resistances R6, R7, and R8 in cross-interconnected box C2, so that their resistance values are gradually reduced from 10 MΩ under normal insulation conditions to 0 Ω, in order to simulate the evolution process of the grounding box from normal state, insulation degradation, severe water ingress, until the metal sheath is directly grounded at the grounding box.
[0015] Specifically, the calculation of the current response at both ends of the cable sheath under different degrees of water ingress defects involves calculating or collecting sheath current data at each measuring point for different grounding resistance values, and extracting characteristic quantities that can characterize the water ingress state of the grounding box, namely the amplitude and phase of the sheath current at both ends.
[0016] The specific method for constructing a sample set for identifying water ingress defects in grounding boxes involves taking cross-interconnected grounding box C1 as an example, selecting the corresponding R3-R5 resistance values as the research object, setting them to 25 resistance values to characterize the development process of water ingress defects from slight dampness to severe grounding. Samples are generated under each resistance value condition. Similarly, cross-interconnected grounding box C2 is generated in the same way. The sheath current characteristics corresponding to different grounding resistance levels are used as input features, and the water ingress location and degree of water ingress in the grounding box are used as sample labels to form training samples. Based on the grounding resistance decrease range, the grounding box status is divided into different defect levels such as normal, slight water ingress, moderate water ingress, severe water ingress, and direct grounding, resulting in a sample set covering multiple operating conditions.
[0017] The specific steps for establishing a grounding box water ingress defect identification model using the XGBoost algorithm are as follows: the completed sample set is divided into a training set and a test set. The sheath current amplitude and phase correlation characteristics are used as model inputs, and the degree of grounding box water ingress defect is used as model outputs. The XGBoost model is trained. After training, the sheath current characteristics collected in real time are input into the model, which can quickly output whether the grounding box has a water ingress defect and its corresponding defect degree.
[0018] Compared with the prior art, the present invention has significant beneficial effects.
[0019] This invention utilizes current transformers placed at both ends of the cable's metallic sheath to collect the amplitude and phase characteristics of the sheath current. Combined with the XGBoost algorithm, it identifies water ingress defects in cross-connected grounding boxes, avoiding the lag and destructive nature of traditional manual inspections or box-opening checks. This method requires no alteration to the cable's structure and features online, non-invasive, and fast response. By equating the decrease in insulation resistance caused by water ingress into the grounding box with a change in grounding resistance, and constructing sample sets for different defect levels, the model's ability to distinguish between mild dampness, severe water ingress, and direct grounding is effectively improved. Compared to single-threshold judgment methods, this invention comprehensively utilizes the amplitude, phase, and variation patterns of the sheath current, enhancing the accuracy and anti-interference capability of defect identification, and providing a reliable basis for high-voltage cable operational status assessment and fault early warning. Attached Figure Description
[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of a three-phase nine-segment cross-connected high-voltage cable;
[0022] Figure 2 Equivalent circuit diagram of inductive coupling in the cross-interconnected grounding box for water inlet;
[0023] Figure 3 This is the equivalent circuit diagram for capacitive coupling of the cross-connected grounding box inlet. Detailed Implementation
[0024] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0025] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0026] (1) Technical principles
[0027] 1. Equivalent circuit of cross-connected system
[0028] A schematic diagram of a three-phase nine-segment cross-connected high-voltage cable is shown below. Figure 1 As shown, the nine segments A1-C3 are the cable sheath. The cable sheath is transposed to make the vector sum of the induced electromotive force of the three-phase sheath approach zero, reducing the induced circulating current. The three circuits are A1-B2-C3, B1-C2-A3, and C1-A2-B3, respectively. R3-R8 are the equivalent impedance of the sheath protector, and R1 and R2 are the grounding resistances. The sheath is transposed through the two cross-interconnected grounding boxes C1 and C2 in the middle.
[0029] 2. Equivalent circuit for water inlet of cross-connected grounding box
[0030] The equivalent circuit of the inductive coupling of the cross-connected grounding box inlet is as follows: Figure 2 As shown in the figure, U Xn Z is the induced voltage generated by the current flowing through the conductor. Xn Let X be the equivalent sheath impedance of each cable segment, where X is one of phases A, B, and C, and n is one of segments 1, 2, and 3. In the established inductive coupling model of loop 1, the defect states under different water ingress stages of the cross-interconnection grounding box are simulated by adjusting the values of R3-R8. Specifically, R3-R5 is changed to simulate water ingress into cross-interconnection grounding box C1, and R6-R8 is changed to simulate water ingress into cross-interconnection grounding box C2. The sinusoidal steady-state induced electromotive force of the sheath of the cable segment A1-B2-C3 in loop 1 is:
[0031] (1)
[0032] Among them, I A I B I C Z represents the current flowing through the conductors of phases A, B, and C. x,yn The mutual impedance between the x-phase conductor and the yn-section of the cable is defined as follows:
[0033] (2)
[0034] In the formula, x and y represent phases A, B, and C; f is the system frequency; μ0 is the free permeability; d x,y This represents the geometric mean distance between the x-phase conductor and the y-phase sheath; n takes the values 1, 2, or 3 to represent 3 small segments of cable sheath.
[0035] Based on Kirchhoff's voltage law, the node voltage equations for the inductively coupled circuit of loop 1 are as follows:
[0036] (3)
[0037] Where A is the topology matrix of the inductively coupled circuit of loop 1, expressed as:
[0038] (4)
[0039] Y is the nodal admittance matrix, expressed as:
[0040] (5)
[0041] Nodal voltage column vector U n for
[0042] (6)
[0043] In the formula, U1 and U2 are the voltages (V) of the grounding branch node where the sheath protector is located relative to the ground.
[0044] U s For voltage source column phasors, the expression is:
[0045] (7)
[0046] The induced current components I at the left and right ends of circuit 1 a1 I a2 for
[0047] (8)
[0048] Figure 3 This is the equivalent circuit for capacitive coupling in loop 1. In the diagram: the node voltages to ground for each node are U... 1L U 2L U 3L U 4L U 5L , V.
[0049] Taking the ground as the reference node, list the node voltage equations for loop 1. Calculate the phase voltage U. A U B U C Under individual action, the nodal voltage equations of the five nodes relative to the ground are as follows:
[0050] (9)
[0051] Circuit topology matrix A for capacitive coupling current in loop 1 L for
[0052] (10)
[0053] Y L The nodal admittance matrix
[0054] (11)
[0055] U Lx Nodal voltage column vector
[0056] (12)
[0057] In the formula, x takes the values A, B, and C, and U 1Lx ~U 5Lx This represents the node voltage generated by phase x at nodes 1-5. U sLx The column vector of voltage sources generated by phase x
[0058] (13)
[0059] The capacitive current component I at the beginning and end points a1 and a2 of circuit 1a1L I a2L for
[0060] (14)
[0061] The sheath current is the vector sum of inductive and capacitive currents.
[0062] (2) Implementation process
[0063] (1) Establish a calculation model for the sheath current of the high-voltage cable cross-interconnection grounding box with water inlet.
[0064] Based on the actual cable line structure and sheath grounding circuit parameters, a calculation relationship for sheath current under cross-interconnection conditions is constructed to obtain the current amplitude and phase distribution characteristics at the beginning and end of the metal sheath of each cable segment under normal operating conditions. This model can reflect the influence of cable load current, grounding resistance, etc. on sheath current, providing a foundation for subsequent water ingress defect simulation and sample generation.
[0065] (2) Perform equivalent simulation of water ingress defects in cross-connected grounding boxes.
[0066] Since water ingress into the grounding box leads to the deterioration of the insulation environment inside the box, creating leakage paths of varying degrees between the sheath protector, connecting conductors, terminals, and the box body, this invention characterizes the degree of water ingress by changing the equivalent grounding resistance inside the grounding box. Specifically, by adjusting the grounding resistances R3, R4, and R5 in cross-interconnection box C1 and the grounding resistances R6, R7, and R8 in cross-interconnection box C2, their resistance values are gradually reduced from 10 MΩ under normal insulation conditions to 0 Ω. This simulates the evolution of the grounding box from a normal state, to reduced insulation, to severe water ingress, and finally to direct grounding of the metal sheath at the grounding box.
[0067] (3) Calculate the current response at both ends of the cable sheath under different water ingress defect levels.
[0068] For different grounding resistance values, the sheath current data of each measuring point are calculated or collected, and the characteristic quantities that can characterize the water ingress state of the grounding box are extracted, namely the amplitude and phase of the sheath current at the beginning and end.
[0069] (4) Construct a sample set for identifying water ingress defects in grounding boxes.
[0070] Taking the cross-interconnected grounding box C1 as an example, the corresponding R3-R5 resistance values are selected as the research objects. According to Tables 1 and 2, 25 resistance values are set to characterize the development process of water ingress defects from slight dampness to severe grounding. Samples are generated under each resistance value condition, and the same applies to the cross-interconnected grounding box C2.
[0071] Table 1. Changes in grounding resistance during water ingress into the cross-connected grounding box.
[0072]
[0073] Table 2 Classification of Water Ingress Defect Levels in Cross-Interconnected Grounding Boxes
[0074]
[0075] The sheath current characteristics corresponding to different grounding resistance levels are used as input features, and the location and degree of water ingress in the grounding box are used as sample labels to form training samples. Based on the grounding resistance decrease range, the grounding box status is divided into different defect levels such as normal, slight water ingress, moderate water ingress, severe water ingress, and direct grounding, resulting in a sample set covering multiple operating conditions.
[0076] (5) Use the XGBoost algorithm to establish a grounding box water ingress defect identification model.
[0077] The constructed sample set is divided into a training set and a test set. The XGBoost model is trained using the sheath current amplitude and phase correlation characteristics as model inputs and the degree of water ingress defect in the grounding box as model output. After training, the real-time collected sheath current characteristics are input into the model to quickly output whether there is a water ingress defect in the grounding box and its corresponding defect degree.
[0078] This method can fully utilize the variation law of sheath current amplitude and phase during the insulation degradation process of grounding box to achieve online, rapid and non-invasive identification of water ingress defects in cross-interconnected grounding boxes.
[0079] By adopting the above implementation process, the present invention does not require opening the grounding box or damaging the cable structure. It can determine the water ingress status of the grounding box simply by collecting current information through current transformers at both ends of the sheath. It has the advantages of fast detection speed, high identification accuracy and strong field applicability.
[0080] This embodiment takes a 110 kV cross-linked polyethylene high-voltage cable line with a total length of 1.5 km as an example. The line adopts a cross-interconnection grounding method, with a cross-interconnection grounding box set every 500 m. Cross-interconnection box C1 located at 500 m and cross-interconnection box C2 located at 1 km are selected as the monitoring objects for water ingress defects.
[0081] Hardware deployment: Current transformers are installed at both ends of the cable's metallic sheath to collect the sheath grounding current signal. The transformer outputs are connected to a data acquisition device to obtain the sheath current amplitude and phase information.
[0082] Benchmark establishment: Under normal line operation, collect current data at both ends of the sheath under different load conditions to establish a characteristic benchmark for sheath current under normal operating conditions.
[0083] Simulation and Sample Construction: The simulation simulates the evolution of the grounding box from slight dampness and insulation deterioration to direct grounding of the metal sheath. Current signals at both ends of the sheath are calculated under various resistance conditions. Characteristic quantities such as current amplitude, phase, amplitude difference between the beginning and end ends, phase difference, and three-phase imbalance are extracted to construct a water ingress defect sample set, which is then labeled according to the degree of defect.
[0084] Model recognition: The sample set is input into the XGBoost model for training to establish a grounding box water ingress defect recognition model. During online operation, the sheath current characteristics are extracted in real time and input into the model to output the water ingress location and defect degree of the cross-connection box, realizing rapid identification of grounding box water ingress defects.
[0085] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current, characterized in that, Includes the following steps: Establish a calculation model for the sheath current of water entering the cross-interconnected grounding box of high-voltage cables; An equivalent simulation of the water ingress defect in the cross-connected grounding box was performed. The current response at both ends of the cable sheath was calculated under different degrees of water ingress defects. Construct a sample set for identifying water ingress defects in grounding boxes; A model for identifying water ingress defects in grounding boxes was established using the XGBoost algorithm.
2. The rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current according to claim 1, characterized in that, The specific steps for establishing the sheath current calculation model for water ingress into the cross-interconnected grounding box of high-voltage cables are as follows: based on the actual cable line structure and sheath grounding circuit parameters, the sheath current calculation relationship under the cross-interconnected state is constructed to obtain the current amplitude and phase distribution characteristics of the beginning and end of the metal sheath of each cable section under normal operating conditions. This model can reflect the influence of cable load current, grounding resistance, etc. on sheath current, providing a basis for subsequent water ingress defect simulation and sample generation.
3. The rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current according to claim 1, characterized in that, The equivalent simulation of the water ingress defect in the cross-interconnected grounding box is specifically carried out by adjusting the grounding resistances R3, R4, and R5 in cross-interconnected box C1 and the grounding resistances R6, R7, and R8 in cross-interconnected box C2, so that their resistance values are gradually reduced from 10 MΩ under normal insulation conditions to 0 Ω, in order to simulate the evolution process of the grounding box from normal state, insulation degradation, severe water ingress, until the metal sheath is directly grounded at the grounding box.
4. The rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current according to claim 1, characterized in that, Specifically, the calculation of the current response at both ends of the cable sheath under different degrees of water ingress defects involves calculating or collecting sheath current data at each measuring point for different grounding resistance values, and extracting characteristic quantities that can characterize the water ingress state of the grounding box, namely the amplitude and phase of the sheath current at both ends.
5. The rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current according to claim 1, characterized in that, The specific method for constructing a sample set for identifying water ingress defects in grounding boxes involves taking cross-interconnected grounding box C1 as an example, selecting the corresponding R3-R5 resistance values as the research object, setting them to 25 resistance values to characterize the development process of water ingress defects from slight dampness to severe grounding. Samples are generated under each resistance value condition. Similarly, cross-interconnected grounding box C2 is generated in the same way. The sheath current characteristics corresponding to different grounding resistance levels are used as input features, and the water ingress location and degree of water ingress in the grounding box are used as sample labels to form training samples. Based on the grounding resistance decrease range, the grounding box status is divided into different defect levels such as normal, slight water ingress, moderate water ingress, severe water ingress, and direct grounding, resulting in a sample set covering multiple operating conditions.
6. The rapid detection method for water ingress into a high-voltage cable grounding box based on sheath grounding current according to claim 1, characterized in that, The specific steps for establishing a grounding box water ingress defect identification model using the XGBoost algorithm are as follows: the completed sample set is divided into a training set and a test set. The sheath current amplitude and phase correlation characteristics are used as model inputs, and the degree of grounding box water ingress defect is used as model outputs. The XGBoost model is trained. After training, the sheath current characteristics collected in real time are input into the model, which can quickly output whether the grounding box has a water ingress defect and its corresponding defect degree.