Double-probe zero-value insulation identification method considering surface wetting state of insulator

Abstract

The invention provides a double-probe zero-value insulation identification method considering an insulator surface wetting state, and relates to the technical field of power transmission line state detection. The method comprises the steps that S1, two electric field probes are arranged on the surface of an umbrella skirt of an insulator at intervals in the axial direction, and the electric field intensities output by the two electric field probes are marked as E1 and E2 respectively; s2, calculating a deviation rate eta based on the electric field intensities output by the two electric field probes; s3, detecting a surface wetting index W of the insulator; s4, correcting the surface wetting index W to obtain a correction coefficient Kwet; s5, modifying the criterion of the zero value state into eta < lt >; and the zero value state is recognized according to the set threshold value Eta0. Kwet, and Eta0 is a fixed threshold value. According to the method, the accuracy of insulator zero value state recognition can be kept in multiple environment scenes such as rain, fog and moisture, and high robustness and high adaptability are improved for intelligent routing inspection and zero value defect recognition of a power transmission line.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power transmission line state detection, in particular to a double-probe zero-value insulator identification method considering the wetting state of insulator surface. BACKGROUND

[0002] During long-term operation, power transmission line insulators may have problems such as partial breakdown, contamination, and aging, among which "zero-value insulator" is one of the most dangerous defects.

[0003] In order to ensure the safe operation of power transmission lines and the safety of personnel during live-line work, insulators need to be detected. The existing methods for detecting zero-value insulators mainly include spark gap method, distributed voltage detection method, infrared thermal imaging detection method, ultrasonic detection method, resistance measurement method, inductive coupling method, and capacitive coupling method. The disadvantages of these methods can be summarized as follows: 1. Accuracy Subjective factors and weak signals are difficult to measure: the spark gap method is easily affected by subjective judgment, the ultrasonic detection method is not sensitive to small defects, and the capacitive coupling method is not directly related to the evaluation of insulator performance, which may lead to inaccurate judgment of insulator state.

[0004] Environmental interference: the infrared thermal imaging detection method is affected by environmental temperature and direct sunlight, the capacitive coupling method and the distributed voltage detection method are disturbed by environmental factors such as humidity and contamination, and the inductive coupling method is disturbed by external electromagnetic fields. These situations may mask the problems of insulators themselves or cause signal changes, affecting the accuracy of judgment.

[0005] 2. Detection efficiency Complex operation and time-consuming: the ultrasonic detection method and the resistance measurement method have relatively slow detection processes, the distributed voltage detection method requires professional personnel and equipment, and the operation is relatively complex, resulting in low detection efficiency. The spark gap method relies on manual climbing of the tower, which is slow and labor-intensive.

[0006] 3. Safety and cost Safety risks: the spark gap method involves manual operation on the tower, which poses a risk of falling from a great height and electric shock.

[0007] High equipment cost: the infrared thermal imaging detection method, inductive coupling method, and capacitive coupling method require expensive equipment, and some of the equipment also needs regular maintenance and calibration, increasing the cost of detection. At the same time, some methods require professional technical personnel to operate, also increasing the labor cost.

[0008] Power outage restrictions: the resistance measurement method generally requires power outage detection, which affects the normal operation of the power system and limits its application.

[0009] Currently, the unmanned aerial vehicle carries a space electric field sensor as a new means, and the monitoring advantages mainly lie in the following aspects: the detection personnel do not need to directly contact high-voltage equipment and lines, avoiding the risks of electric shock and high-altitude falling, and the safety is significantly improved. The unmanned aerial vehicle is flexible and can quickly reach and cover a large area of detection area, greatly improving the detection efficiency. At the same time, the data can be monitored and transmitted in real time, which is convenient for technicians to make timely decisions and enhances the timeliness of the inspection. The non-contact detection does not cause physical damage or interference to the insulator, which conforms to the trend of non-destructive testing and is beneficial to the safe and stable operation of the transmission line.

[0010] However, the traditional method mainly depends on a single probe to scan the whole insulator string to obtain the electric field distribution, but the motion speed of the robot and the probe spacing are difficult to keep constant, resulting in a large error in field detection. Existing researches have proved that by analyzing the mutation characteristics of the local electric field distribution at the zero value position, the zero value recognition can be realized by using a double-probe or multi-probe local array. The reference data show that in the double-probe array, the deviation rate η of the probe under the zero value state is significantly smaller than that under the perfect state, and there is a clear criterion space.

[0011] However, the existing technology does not consider the influence of the wetting state (wet, water film) of the insulator surface on the surface electric field distribution. In actual field, the wetting of the insulator surface will reduce the electric field gradient, and the deviation rate η of the zero value recognition will be reduced as a whole, resulting in the failure of the fixed threshold criterion.

[0012] Therefore, it is necessary to provide a double-probe zero value recognition method which can automatically correct the influence of surface wetting. SUMMARY

[0013] The purpose of the present application includes providing a double-probe zero value insulator recognition method considering the wetting state of the insulator surface, which can maintain the accuracy of the zero value state recognition of the insulator in rain, fog, wet and other environmental scenes, and provides high robustness and high adaptability for intelligent inspection and zero value defect recognition of the transmission line.

[0014] The embodiments of the present application can be implemented as follows: The present application provides a double-probe zero value insulator recognition method considering the wetting state of the insulator surface, and the method comprises the following steps: S1: arranging two electric field probes on the umbrella skirt surface of the insulator in an axial direction, and the electric field intensities output by the two electric field probes are denoted as E1 and E2, respectively; S2: calculating the deviation rate η based on the electric field intensities output by the two electric field probes; S3: detecting the surface wetting index W of the insulator; S4: correcting the surface wetting index W to obtain a correction coefficient K wet ; S5: modifying the criterion of the zero value state as η<η0·Kwet , and a zero-value state is identified, where η0 is a fixed threshold.

[0015] In an optional embodiment, S1 comprises: Two electric field probes are arranged on the surface of the shed of the insulator at an axial interval of 80-120 mm.

[0016] In an optional embodiment, in S2, the deviation rate η is expressed as: .

[0017] In an optional embodiment, in S3, the surface wetness index W can be converted based on the relative humidity RH, the leakage current signal I_leak, the water film reflection characteristic, or the electric field fluctuation degree σE.

[0018] In an optional embodiment, in S4, the formula for correcting the surface wetness index W is: K wet =1-αW, where α is an empirical coefficient or a calibration coefficient.

[0019] In an optional embodiment, S5 comprises: determining whether η<η0·K wet , and if yes, identifying a zero-value state; and if no, identifying a perfect state.

[0020] In an optional embodiment, the fixed threshold η0 is 12%-17%.

[0021] In an optional embodiment, S5 comprises: For a 500 kV double-shed insulator, when the insulator is in a dry state: K wet =1, then η0·K wet =15%; when the insulator is in a slightly wet state: K wet =0.85, then η0·K wet =12.75%; and when the insulator is in a surface water film state: K wet =0.60, then η0·K wet =9%.

[0022] The double-probe zero-value insulator identification method considering the wetting state of the surface of the insulator provided by the embodiments has the following beneficial effects: 1. The method proposes a correction coefficient K wet of the surface wetness index W, modifies the criterion for the zero-value state to η<η0·K wet , and maintains the accuracy of identifying the zero-value state of the insulator in rain, fog, humidity, and other environmental scenarios; 2. The whole method has the advantages of simple steps, no need for whole-string scanning, low calculation amount, and direct embedding into a patrol robot. 3. The method improves high robustness and high adaptability for intelligent inspection of power transmission lines and zero-value defect identification. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0024] Figure 1 The flow chart of the double-probe zero-value insulation identification method considering the wetting state of the insulator surface provided by the embodiments of the present application. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] It should be noted that the features in the embodiments of the present application can be combined with each other without conflict.

[0028] The zero-value identification method of the traditional insulator relies on power-off detection and other methods, and the new infrared technology has poor environmental adaptability. The double-probe electric field method can capture the local electric field mutation characteristics at the zero-value shed, and the deviation rate is significantly smaller than that in the intact state in the zero-value state, but the existing research does not consider the systematic influence of humidity on the deviation rate. Under wet conditions, the leakage current on the surface of the shed is enhanced, which makes the electric field distribution uniform, and the deviation rate is reduced as a whole, so that a large number of misjudgments will be produced if a fixed threshold is used.

[0029] For this purpose, please refer to Figure 1 The embodiments provide a double-probe zero-value insulation identification method (hereinafter referred to as: method) considering the wetting state of the insulator surface. wet The criterion for the zero-value state is modified as η<η0·Kwet In the rain, fog, humidity and other multi-environmental scenarios, the accuracy of identifying the zero value state of the insulator is maintained. Specifically, the method comprises the following steps: S1: Two electric field probes are arranged on the umbrella skirt surface of the insulator in an axial direction, and the electric field strengths output by the two electric field probes are denoted as E1 and E2, respectively.

[0030] Specifically, because the two electric field probes only need to cover the zero value characteristic area of the umbrella skirt surface of the insulator in an axial direction by 80mm-120mm, two electric field probes are arranged on the umbrella skirt surface of the insulator in an axial direction by 80mm-120mm (preferably 100mm), and the electric field strengths output by the two electric field probes are denoted as E1 and E2, respectively. Because the electric field curve of the zero value area is steep and the gradient is significant, double probes are used to effectively capture the mutation characteristics of the local electric field.

[0031] S2: Based on the electric field strengths output by the two electric field probes, the deviation rate η is calculated.

[0032] Specifically, the deviation rate η expression is:

[0033] Analysis shows that: when the surface of the insulator is wet, there is a water film or dew, the surface leakage current increases, the actual electric field distribution of the umbrella skirt surface becomes more uniform, which is manifested as: the difference between the electric field strengths E1 and E2 output by the two electric field probes decreases, that is, the value of (E1-E2) becomes smaller; makes the calculated deviation rate η overall decreases. If, when the surface of the insulator is wet, there is a water film or dew, the fixed threshold judgment mode: η<η0 is still used to determine the zero value state, which may appear misjudgment (for example, the perfect wet state is misidentified as a zero value state), that is, when the calculated η is less than η0, it is determined that it is a zero value state, wherein η0 is a fixed threshold.

[0034] The determination process of the fixed threshold η0 is as follows: After a large number of simulations and tests, the deviation rates η corresponding to the zero value state and the perfect state of the insulator surface in the dry state are counted:

[0035] From the above table data, it can be seen that in the case of dry surface of the insulator, the deviation rate η of the zero value state is usually 1.5%-12%; the deviation rate η of the perfect state is 17%-50%. Therefore, in the dry environment, the fixed threshold η0 can be set to 12%-17%, and in this embodiment, η0=15% is taken, and the fixed threshold judgment mode is: η<η0=15%.

[0036] The embodiment has analyzed that if the surface of the insulator is wet, the calculated η will be smaller, which may misidentify the perfect wet state as the zero value state. The embodiment introduces a correction mechanism for compensation.

[0037] S3: detecting a surface wetness index W of the insulator.

[0038] The surface wetness index W can be selected from humidity, surface conductivity, etc. The embodiment provides the following ways to obtain the surface wetness index W: Firstly, a temperature and humidity sensor is carried on the insulator to measure the relative humidity RH of the surface of the insulator. The greater the relative humidity RH, the greater the surface wetness index W. Therefore, the surface wetness index W can be converted based on the relative humidity RH, i.e. W=f(relative humidity RH).

[0039] Secondly, the leakage current signal I_leak of the surface of the insulator shed is measured. The leakage current signal I_leak is positively correlated with the surface wetness index W (i.e. W∝I_leak). The surface wetness index W can also be converted based on the leakage current signal I_leak.

[0040] Thirdly, the water film reflection characteristic of the surface of the insulator shed is identified by machine vision. The greater the water film reflection characteristic, the greater the surface wetness index W. Therefore, the surface wetness index W can be converted based on the water film reflection characteristic.

[0041] Fourthly, the electric field fluctuation degree σE of the surface of the insulator shed is measured. The greater the electric field fluctuation degree σE, the greater the surface wetness index W. Therefore, the surface wetness index W can be converted based on the electric field fluctuation degree σE.

[0042] It should be noted that although the embodiment explicitly gives the calculation formula of the surface wetness index W, any one of the above three ways can be selected, and the corresponding relationship between the surface wetness index W and the measurement parameter (relative humidity RH, leakage current signal I_leak, water film reflection characteristic or electric field fluctuation degree σE) can be obtained based on a certain amount of experimental data, so as to summarize the calculation formula of the surface wetness index W.

[0043] S4: correcting the surface wetness index W to obtain a correction coefficient K wet .

[0044] The formula for correcting the surface wetness index W is: K wet =1−αW, where α is an empirical coefficient or a calibration coefficient, and the value of α can be 0.1-0.5. As can be seen from the correction formula, the more humid the surface of the insulator (i.e. the greater the surface wetness index W), the smaller the correction coefficient K wet .

[0045] S5: modify the criterion of zero-value state to η < η0·K wet , and identify the zero-value state.

[0046] Specifically, S5 includes: S51: determine whether η < η0·K wet If yes, execute S52: identify as a zero-value state; if no, execute S53: identify as a sound state.

[0047] For 500kV double-umbrella insulators, according to simulation and actual measurement data, it is shown that: When the insulator is in a dry state: K wet = 1, then η0·K wet = 15%; When the insulator is in a slightly wet state: K wet = 0.85, then η0·K wet = 12.75%; When the insulator is in a state of surface water film: K wet = 0.60, then η0·K wet = 9%.

[0048] The criterion of zero-value state is modified to η < η0·K wet , and the identified zero-value state is more accurate, solving the problem of misjudgment of zero-value state caused by overall deviation of η under wet conditions.

[0049] The method provided in this embodiment proposes to calculate the deviation rate η based on the electric field intensity output by two electric field probes as the core index for zero-value identification; then refer to data showing that η of the zero-value state is significantly smaller than that of the sound state, with a stable criterion space; then propose a correction coefficient K wet of the surface wetness index W, dynamically correct the criterion of zero-value state by detecting the surface wetness index W of the insulator, for example, when the surface of the insulator is wet, the overall η decreases, and K wet < 1 is taken, the baseline (η0·K wet ) for judging the zero-value state is reduced, and the accuracy of zero-value state identification and environmental adaptability are improved.

[0050] The method provided in this embodiment introduces the correction coefficient K wet of the surface wetness index W on the basis of the traditional fixed threshold judgment method (η < η0), realizes adaptive criterion updating under wet conditions, improves the accuracy of zero-value identification and environmental adaptability, realizes an automatic identification process, and can be embedded in the robot end for execution.

[0051] Therefore, the embodiment also provides a robot online inspection system embedded with the method, and further provides a double-probe zero-value insulation identification device considering the wetting state of the insulator surface (hereinafter referred to as the device). The device comprises two electric field probes, a data processing module, a wetting sensing module and a criterion correction module. The two electric field probes are arranged on the shed surface of the insulator in an axial direction. The electric field strengths output by the two electric field probes are denoted as E1 and E2 respectively. The data processing module is configured to calculate a deviation rate η based on the electric field strengths output by the two electric field probes. The wetting sensing module is configured to detect a surface wetting index W of the insulator. The criterion correction module is configured to correct the surface wetting index W to obtain a correction coefficient K wet ; and further configured to modify the criterion of the zero-value state as η < η0·K wet , and identify the zero-value state.

[0052] The double-probe zero-value insulation identification method, device and robot online inspection system considering the wetting state of the insulator surface have the following advantages: the correction coefficient K wet of the surface wetting index W is proposed, the criterion of the zero-value state is modified as η < η0·K wet , and the accuracy of the identification of the zero-value state of the insulator is maintained in various environmental scenarios such as rain, fog and humidity. The whole method has the advantages of simple steps, no need for whole-string scanning and low calculation amount. The method improves the robustness and adaptability of the intelligent inspection of the power transmission line and the identification of the zero-value defect.

[0053] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A double-probe zero-value insulation identification method considering the wetting state of the surface of an insulator, characterized by, The method comprises: S1: arranging two electric field probes on the surface of the insulator along the axial direction at intervals, and the electric field intensities output by the two electric field probes are respectively denoted as E1 and E2; S2: calculating a deviation rate η based on the electric field intensities output by the two electric field probes; S3: detecting a surface wetness index W of the insulator; S4: correct the surface wetness index W to obtain a correction coefficient K wet ; S5: modify the criterion of zero-value state to η < η0·K wet , identify the zero-value state, wherein η0is a fixed threshold.

2. The dual probe zero value insulation identification method considering the surface wetting state of the insulator according to claim 1, characterized in that, S1 comprises: Arranging two electric field probes on the surface of the insulator along the axial direction at intervals of 80mm-120mm.

3. The dual probe zero value insulation identification method considering the surface wetting state of the insulator according to claim 1, characterized in that, In S2, the expression of the deviation rate η is: 。 4. The dual probe zero value insulation identification method considering the surface wetting state of an insulator according to claim 1, characterized in that, In S3, the surface wetness index W can be converted based on the relative humidity RH, the leakage current signal I_leak, the water film reflection characteristic or the electric field fluctuation degree σE.

5. The dual probe zero value insulation identification method considering the surface wetting state of the insulator according to claim 1, characterized in that, In S4, the formula for correcting the surface wetness index W is: K wet = 1 - aW, where a is an empirical or calibration coefficient.

6. The dual-probe zero-value insulation identification method considering the surface wetting state of an insulator according to claim 1, characterized in that S5 Comprise: determining whether η < η0·K wet If yes, it is identified as a zero value state; if no, it is identified as a good state.

7. The dual probe zero value insulation identification method considering the surface wetting state of the insulator according to claim 1, characterized in that, The fixed threshold η0 is 12%-17%.

8. The dual-probe zero-value insulation identification method considering the surface wetting state of an insulator according to claim 1, characterized in that S5 Comprise: For a 500kV double-umbrella insulator, assuming the insulator is in a dry state: K wet If we take the value 1, then η0·K wet =15%; When the insulator is slightly damp: K wet If we take 0.85, then η0·K wet =12.75%; When the insulator is covered with a water film on its surface: K wet If we take 0.60, then η0·K wet =9%.

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