Insulator defect grading method based on exogenous irradiation and solar blind detection

Abstract

The invention relates to an insulator defect grading method based on external source irradiation and solar blind detection, which comprises the following steps: irradiating the surface of an insulator through a short wave external light source pulse, carrying out solar blind ultraviolet photon detection in a discharge active period after irradiation, and grading defects through an ultraviolet photon number measurement result. Therefore, traditional passive discharge detection is converted into active controllable detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulation condition monitoring of power equipment, and in particular, to a method for grading insulator defects based on external source irradiation and solar-blind detection. Background Art

[0002] Insulators and bushings are key components in the power system, and they play a crucial role in ensuring the safe and reliable operation of the power system. The main functions of insulators and insulating bushings are to provide electrical insulation for wire or equipment outgoing leads to prevent current from leaking to the ground or other conductors through air or other media. When an external insulation fault occurs in a line insulator or equipment bushing, it may cause an arc or fire, posing a safety threat to personnel and equipment, and the fire caused by the insulation fault may pollute the surrounding environment.

[0003] In order to reduce the risk of external insulation faults, the following measures are generally taken for the detection of insulator discharge defects: 1) Using tools such as telescopes to visually inspect insulators to exclude defects such as damaged or severely aged umbrella skirts. It relies on the experience and observation ability of operators. Although this method is simple and easy to implement, it has obvious limitations. The detection results are easily affected by the subjective judgment of operators, and it is difficult to detect potential or weak early defects. In addition, visual inspection is greatly affected by environmental factors such as weather and light, which is not conducive to all-weather detection; 2) Using an on-line leakage current monitoring system, which evaluates the insulation performance of insulators by monitoring the leakage current of insulators. This method requires installing current sensors and monitoring systems on insulators or bushings, but the engineering quantity of installing them string by string is large and the reliability is low. The high installation and maintenance costs limit its popularization in large-scale applications; 3) Using a handheld ultraviolet solar-blind imager to detect insulator strings to discover corona discharges caused by abnormal electric fields. This method is suitable for all-weather measurement, can detect weak corona discharges, and discover early defects. However, due to the long test distance and large photon propagation loss, it has limited sensitivity in photon counting, and it is difficult to be carried on an unmanned aerial vehicle platform for large-scale applications due to high costs.

[0004] In addition, it should be emphasized that the withstand voltage test voltage of insulators or bushings is generally lower than the designed electric field strength, and the discharge critical electric field of micro-defects is relatively high. It is difficult to stimulate the discharge of micro-defects under operating voltage. Under operating voltage, defects often show occasional discharges, and their amplitudes are lower than the detection threshold. During the development of defects, the discharge has the characteristics of randomness and intermittency, and the signal is difficult to be captured in time, resulting in missed judgments. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention proposes a method for grading insulator defects based on external irradiation and solar-blind detection. This method is applicable to being carried by an unmanned aerial vehicle (UAV), changing the previous passive detection method to an active solar-blind photon detection based on external irradiation-induced discharge, realizing rapid in-situ rating and diagnosis of insulator discharge defects. This technical method has the following technical advantages: 1. The optical path structure is simple, the mechanical robustness is good, it is suitable for miniaturized design, which is conducive to the lightweight construction of the UAV, and can cover a large area of lines or power equipment during on-site detection to achieve piece-by-piece detection; 2. Using the external light irradiation method to reduce the insulation defect discharge threshold is beneficial to discovering potential and hidden insulation defects, has a strong ability to detect early insulation faults, and under irradiation, the discharge time delay is greatly reduced, improving the detection efficiency; 3. By cooperating with a solar-blind ultraviolet switching device and an irradiation light source, it can support all-weather detection and is free from the interference of ambient sunlight; 4. By counting ultraviolet photons to rate the severity of discharge defects, the detection quantification ability is enhanced, the analysis and judgment results are more referenceable, and it is convenient for operation and maintenance management personnel to quickly make maintenance decisions.

[0006] In view of the defects existing in the above-mentioned prior art, the present invention discloses a method for grading insulator defects based on external irradiation and solar-blind detection. The method irradiates the surface of the insulator with short-wave external light source pulses, performs solar-blind ultraviolet photon detection during the discharge active period after irradiation, and rates the defects based on the measurement results of the ultraviolet photon count, so as to transform the traditional passive discharge detection into an active controllable detection.

[0007] Preferably,

[0008] The method is based on a detection device composed of an active short-wave external light source and a solar-blind ultraviolet photon detection unit.

[0009] Preferably,

[0010] The detection device includes: 1 controllable ultraviolet short-wave light source.

[0011] Preferably,

[0012] The detection device further includes:

[0013] 1 light guide for light expansion.

[0014] Preferably,

[0015] The detection device further includes:

[0016] 1 solar-blind ultraviolet photon detection unit.

[0017] Preferably,

[0018] The detection device further includes:

[0019] 1 light guide for light concentration.

[0020] Preferably,

[0021] The detection device further includes:

[0022] One control unit.

[0023] Preferably,

[0024] The detection device further includes:

[0025] One data acquisition and processing unit.

[0026] Preferably,

[0027] The method adjusts the attitude and detection distance of the detection device to cover the irradiation area of the ultraviolet short-wave light source with the detection object, starts the solar-blind ultraviolet photon detection unit to continuously pre-detect the detection target area, and obtains the background solar-blind ultraviolet photons under the condition of no irradiation, and its continuous detection duration is T.

[0028] Preferably,

[0029] T is not less than 1 s.

[0030] The beneficial effects of the present invention are:

[0031] The present invention uses a set of detection devices composed of an active short-wave external light source and a solar-blind ultraviolet photon detection unit. In actual use, its implementation method is simple and has high robustness, and can be effectively carried on an industrial drone platform through miniaturization design. The present invention irradiates the surface of the insulator through the pulse of the short-wave external light source, detects the solar-blind ultraviolet photons during the discharge active period after irradiation, and rates the defects based on the measurement results of the ultraviolet photon number, thereby transforming the traditional passive discharge detection into an active and controllable detection. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the system structure in an embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram of the on-site insulator string defect detection by the drone carrying the detection device in an embodiment of the present invention. Detailed Embodiments

[0034] The following further describes the present invention in conjunction with the attached Figures 1 to 2 for further details.

[0035] The inventive concept of the present invention lies in:

[0036] The necessary condition for insulation defects to generate discharge is that the applied electric field strength is higher than the critical field strength of defect discharge. Therefore, in the early stage of the development of micro-defects, discharge phenomena may not necessarily occur. However, with the effect of discharge aging, latent defects may rapidly develop into sudden insulation faults. Through experiments, it is found that under the irradiation of a short-wave external light source, insulation defects can generate stable discharge at a lower electric field, thereby reducing the partial discharge field threshold and significantly reducing the discharge time delay, which is beneficial for quickly and effectively detecting defects.

[0037] Therefore, the present invention proposes a method for grading insulator defects based on external source irradiation and solar-blind detection. It irradiates the surface of the insulator with pulses of a short-wave external light source and performs solar-blind ultraviolet photon detection during the active discharge period after irradiation, thereby transforming traditional passive discharge detection into active and controllable detection. Moreover, the hardware device required to implement this method is relatively simple in structure and has high robustness. Through miniaturization design, it can be effectively carried on an industrial drone platform.

[0038] See Figure 1 , in one embodiment, it discloses the implementation manner of the method of the present invention based on an active short-wave external light source and a solar-blind ultraviolet detection device. Exemplarily, the detection device includes: a controllable ultraviolet short-wave light source, a light diffusing optical fiber, a solar-blind ultraviolet photon detection unit, a light condensing optical fiber, a control unit, and a data acquisition and processing unit, where:

[0039] Controllable ultraviolet short-wave light source a: This light source is a pulsed light source, and the emission spectrum range should cover the short-wave ultraviolet band (100 - 280 nm). The peak power of the light pulse should be adjustable within at least the range of 0 - 850 W, the adjustable power interval should not be higher than 50 W, the electro-optical conversion efficiency should not be lower than 35%, the light pulse width should not be higher than 10 μs, and the light pulse repetition frequency can be adjusted within the range of 50 - 1000 Hz. The above-mentioned light pulse peak value, light pulse width, and light pulse repetition frequency can all be controlled by the control unit;

[0040] It can be understood that the present invention adopts a controllable ultraviolet short-wave pulsed light source (100 - 280 nm) with adjustable peak power (0 - 850 W), pulse width ≤ 10 μs, and repetition frequency 50 - 1000 Hz, and dynamically adjusts the parameters through the control unit, which helps to stimulate the discharge of latent defects, improve the ability to capture weak signals, and solve the problem of missed judgment in traditional passive detection;

[0041] Light diffusing optical fiber b: The light diffusing optical fiber is used to rectangularly diffuse the light beam of the ultraviolet short-wave light source, so as to irradiate the rectangular area where the surface of the insulator is located. Preferably, a fused silica light diffuser that can convert Gaussian light into rectangular flat-top light can be used. The incident light aperture should cover the diameter of the emission area of the ultraviolet short-wave light source, and the transmittance in the short-wave ultraviolet band (100 - 280 nm) should not be lower than 85%;

[0042] It can be understood that the present invention uses a light-expanding optical fiber to convert a Gaussian beam into a rectangular flat-top beam, which is beneficial to evenly cover the surface area of the insulator (for example, the area S of the adaptation area), ensuring that the irradiation range matches the detection target and avoiding local missed detection; this is because the present invention can avoid the blind area of the traditional point light source by covering the target area with rectangular irradiation.

[0043] Solar-blind ultraviolet photon detection unit c: The solar-blind ultraviolet photon detection unit preferably uses a switch-type output solar-blind ultraviolet sensor, and the light-receiving end face area is not less than 16 mm 2 , the ultraviolet light quantum conversion efficiency in the solar-blind band is not less than 25%, and the photoelectric gain is not less than 1×10 4 , and the response speed is not less than 0.25 μs;

[0044] Condensing optical fiber d: The condensing optical fiber is used to focus the discharge beam from the insulator area and input the focused beam to the light-receiving end face of the solar-blind ultraviolet photon detection unit. Preferably, it can be made of fused quartz material, and the transmittance in the short-wave ultraviolet band (100 - 280 nm) is not less than 85%. The output light aperture of the optical fiber does not exceed the area of the light-receiving end face of the solar-blind ultraviolet photon detection unit, but is not less than 80% of the area.

[0045] It can be understood that the present invention uses a condensing optical fiber to focus the discharge photons to the sensor end face (coverage area ≥ 80%) to reduce transmission loss.

[0046] Control unit e: The control unit is mainly used to control the ultraviolet short-wave light source and the solar-blind ultraviolet photon detection unit. It can adjust the light pulse peak power, pulse width, and repetition frequency of the ultraviolet short-wave light source, and can also control the start time and continuous working time of the solar-blind ultraviolet photon detection unit.

[0047] Data acquisition and processing unit f: The data acquisition and processing unit is mainly used to collect and store the switch quantity output by the solar-blind ultraviolet photon detection unit, count the high-level output during the detection time, and rate according to the built-in calculation logic multi-defect algorithm, including the following steps:

[0048] 1. According to the area S of the detection object (unit: m 2 ), through the control unit, set the light pulse peak power P = a·S (unit: W), pulse width w (unit: s), and repetition frequency f = b / P (unit: Hz) of the ultraviolet short-wave light source, where a and b are scale factors. Preferably, a = 1500 and b = 5×10 3 , and the pulse width w does not exceed 3×10 -7 ns;

[0049] 2. By adjusting the attitude and detection distance of the detection device, the irradiation area of the ultraviolet short-wave light source is covered with the detection object, and the solar-blind ultraviolet photon detection unit is started to continuously pre-detect the detection target area to obtain the background solar-blind ultraviolet photons under the condition of no irradiation. The continuous detection duration is T, and T should be not less than 1 s. The data acquisition and processing unit accumulatively counts the switching quantities output by the solar-blind ultraviolet photon detection unit, and the counting result is recorded as N 0 ;

[0050] 3. Start the ultraviolet short-wave light source to irradiate the detection target with light pulses. The irradiation intensity F is calculated as follows: F = 0.5·P·w·f·t, where t is the total irradiation time, and F should meet the adaptation conditions:

[0051] ① For porcelain insulators, 1.25 ≤ F ≤ 2.25, (unit: 10 -5 J);

[0052] ② For composite insulators, 0.8 ≤ F ≤ 1.5, (unit: 10 -5 J);

[0053] ③ For glass insulators, 0.5 ≤ F ≤ 1.0, (unit: 10 -5 J);

[0054] 4. After each adjacent ultraviolet short-wave light pulse is emitted, wait for a time (unit: s) and then start the solar-blind ultraviolet photon detection unit to continuously detect the detection target area;

[0055] 5. The data acquisition and processing unit accumulatively counts the switching quantities output by the solar-blind ultraviolet photon detection unit, and the counting result is recorded as N;

[0056] 6. Calculate the relative intensity n of the net-irradiation-excited solar-blind ultraviolet photons: n = N / (f·t) - N 0 / (f·T);

[0057] 7. Evaluate the severity of the insulation defect according to the calculation result of the relative intensity n of the net-irradiation-excited solar-blind ultraviolet photons. The evaluation classification method is as follows:

[0058] Level I: ;

[0059] Level II: ;

[0060] Level III: ;

[0061] Preferably, the values of k1, k2, and k3 are as follows:

[0062] ① For porcelain insulators, k1 = 3, k2 = 10, k3 = 20;

[0063] ②For composite insulators, k1 = 2, k2 = 6, k3 = 12;

[0064] ③For glass insulators, k1 = 5, k2 = 15, k3 = 30.

[0065] In another embodiment, taking the on-site live detection of a 500 kV line composite insulator as an example, the following describes how to achieve defect degree grading analysis through the present invention:

[0066] Mount the above detection device disclosed in the present invention on a power line inspection UAV system. The UAV flies to near the high-voltage line insulator by remote control and hovers at the optimal distance, and aligns the detection unit with the insulator target through the ground-end preview method. See Figure 2 as shown. Figure 2 is an example of using a UAV-mounted detection device to detect the defects of an on-site insulator string.

[0067] Calculate the area S of the detection object area as 0.18 m 2 , set the control unit to set the peak power P of the ultraviolet short-wave light source optical pulse to P = a·S = 1500×0.18 = 270 W, the pulse width w = 200×10 -9 (unit: s), the repetition frequency f = b / P = 5×10 3 ÷270 = 18.5 (unit: Hz);

[0068] Adjust the attitude and detection distance of the detection device by remote control, cover the detection object with the irradiation area of the ultraviolet short-wave light source, start the solar-blind ultraviolet photon detection unit to continuously pre-detect the detection target area, obtain the background solar-blind ultraviolet photons under the condition of no irradiation, and its continuous detection duration T is 2 s. Cumulatively count the switching quantity output by the solar-blind ultraviolet photon detection unit through the data acquisition and processing unit, and record the counting result as N 0 = 315;

[0069] Start the ultraviolet short-wave light source to irradiate the detection target with optical pulses. The irradiation intensity F is calculated as follows: F = 0.5·P·w·f·t = 0.5×270×200×10 -9 ×18.5×2≈1×10 -5 J, the total irradiation time t = 2 s, and F satisfies the adaptation condition: 0.8≤F≤1.5, (unit: 10 -5 J);

[0070] Set the detection waiting time after each adjacent ultraviolet short-wave optical pulse to be = 0.105÷18.5 = 5.7 ms;

[0071] The data acquisition and processing unit accumulatively counts the digital signals output by the solar-blind ultraviolet photon detection unit, and the counting result is recorded as N = 95;

[0072] Calculate the relative intensity n of the solar-blind ultraviolet photons excited by the net irradiation, where n = N / (f·t) - N 0 / (f·T) = (315÷(18.5×2)) - (95÷(18.5×2)) = 8.51 - 2.57 = 5.95;

[0073] According to the rating method for the severity of defects under the condition of composite insulators, exemplarily, the rating result of this time is Grade II.

[0074] In summary, through external irradiation and combined with the high-gain characteristics of the solar-blind sensor, the present invention solves the problems of weak and random signals of micro-defects, so that the present invention has the ability to detect early faults; in addition, the light expansion / condensation design and solar-blind band selection of the present invention improve the effective signal capture rate and reduce environmental interference, so that the present invention has the ability to detect all-weather and with high reliability; in addition, through the solutions of UAV adaptation and miniaturization, the present invention also realizes the simplification of the structure and lightweight design, which is obviously beneficial to efficient large-scale inspection and complex environment coverage, breaking through the space limitation of traditional detection. Therefore, through means such as active irradiation excitation, solar-blind photon detection, optical path optimization design, control algorithm and UAV adaptation, the present invention upgrades the traditional passive detection to an active controllable, highly sensitive and quantitatively rated insulator defect diagnosis system, directly solving the pain points of high misjudgment rate, strong environmental interference, low detection efficiency and high cost in the prior art, and providing an efficient and innovative solution for the early warning and precise operation and maintenance of insulation defects in the power system.

[0075] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manners. Any other implementation manners obtained by those skilled in the art according to the technical solutions of the present invention also belong to the scope of protection of the present invention.

Claims

1. An insulator defect classification method based on external radiation and solar blind detection, characterized in that: The method irradiates the surface of the insulator through a short-wave external light source pulse, performs day-blind ultraviolet photon detection during the discharge active period after irradiation, and rates defects through ultraviolet photon number measurement results, so as to transform traditional passive discharge detection into active controllable detection.

2. The insulator defect classification method based on external radiation and solar blind detection according to claim 1 is characterized in that: Preferably, the method is based on a detection device consisting of an active short-wave external light source and a day-blind ultraviolet photon detection unit.

3. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device comprises: a controllable ultraviolet short-wave light source.

4. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device also includes: 1 light-expanding light guide.

5. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device comprises: 1 solar-blind UV photon detection unit.

6. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device also includes: 1 focusing light guide.

7. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device also includes: 1 control unit.

8. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The detection device also includes: 1 data acquisition and processing unit.

9. The insulator defect classification method based on external radiation and solar blind detection according to claim 2 is characterized in that: The method adjusts the posture and detection distance of the detection device, covers the detection object with the irradiation area of ​​the ultraviolet short-wave light source, starts the day-blind ultraviolet photon detection unit to perform continuous pre-detection on the detection target area, and obtains background day-blind ultraviolet photons under non-irradiation conditions. The continuous detection time is T .

10. The insulator defect classification method based on external radiation and solar blind detection according to claim 9 is characterized in that: T Not less than 1s.

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