Non-contact live detection device and live detection method

Abstract

A non-contact live detection device and a live detection method. The device comprises a processing unit (4), and a detection unit and an image acquisition unit (3) which are both communicatively connected to the processing unit (4); the detection unit comprises an electromagnetic wave sensor (2) and at least three ultrasonic sensors (1); the image acquisition unit (3) is configured to acquire an insulation defect picture of an overhead line detected by the detection unit; and the processing unit (4) is configured to obtain spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity and ultrasonic intensity of an insulation defect position on the basis of a detection result of the detection unit, and identify the insulation defect picture.

Description

Non-contact charged detection device and charged detection method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 25, 2023, with application number 202310750084.X. The entire contents of this application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of distribution network fault location, for example, to a non-contact live detection device and live detection method. Background Art

[0003] Overhead distribution lines are the arteries of power system operation, connecting transmission lines with end users. Within the power distribution system, overhead lines are widely used in medium-voltage distribution grids, traversing urban roads and wooded areas in farmlands to distribute and transmit electricity to users. These lines are characterized by long mileage and a diverse array of equipment along the lines. Because overhead distribution lines are widely used in rural, suburban, and some urban areas, they are exposed to the elements year-round, subjecting insulators and cable transfer terminals along the lines to a range of adverse conditions, such as bird damage, environmental pollution, and severe weather. If insulation defects in insulators and cable transfer terminals are not promptly addressed, they can lead to serious power outages and significant economic losses. Therefore, detecting insulation defects in insulators and cable transfer terminals on distribution overhead lines is of great practical significance.

[0004] Ultrasonic testing instruments are primarily used to inspect insulation defects in overhead distribution line insulators and cable transfer terminals. The two main ultrasonic testing devices employed are wave condenser-type testing devices and ultrasonic imagers. Wave condenser-type testing devices use a wave condenser to focus ultrasonic waves, which can improve the sensitivity and directionality of ultrasonic testing. However, when a large number of electrical equipment are present in the testing area, they cannot locate equipment with insulation defects. Ultrasonic imagers, based on the theory of acoustic imaging, utilize a microphone array to detect the sound field distribution across the entire acoustic plane, enabling precise identification of insulation defects. However, due to limitations in the system structure, ultrasonic imagers have poor sensitivity. Furthermore, both types of testing devices are sensitive to detection distance. When the device is close to the insulation defect, the ultrasonic detection intensity is high, while when the device is far away from the insulation defect, the ultrasonic detection intensity is low. Therefore, these ultrasonic testing devices are significantly affected by detection distance, and there is no unified reference for determining the severity of insulation defects.

[0005] CN111443267A discloses an enhanced 10kV overhead insulated line partial discharge inspection device and inspection method, comprising an ultrasonic sensor, a UHF antenna sensor, an ultrasonic amplifying and filtering circuit, a UHF amplifying and filtering circuit, a detection circuit, a dual-channel analog-to-digital (A / D) converter, an Advanced RISC Machine (ARM) microprocessor, and a memory card. This device primarily addresses the poor anti-interference capability and low efficiency of single ultrasonic detection devices. By adding a UHF antenna sensor, it implements overhead line partial discharge detection using both ultrasonic and electrical signal detection methods. However, the following shortcomings remain. First, the aforementioned disclosed solution only provides a general qualitative description of the shape of the wave condenser, without analyzing the design of the ultrasonic wave condenser or providing an optimal design for the wave condenser's shape and size. Consequently, the detection device's ability to resist external interference cannot be significantly improved. Second, the aforementioned disclosed solution does not provide a method for calculating the distance of the defect, making it impossible to locate the spatial coordinates of the defect, nor to visualize the defect and its corresponding defect parameters. This results in the aforementioned disclosed solution being less intuitive and inefficient for field application. Third, the aforementioned disclosed solution directly uses the original ultrasonic detection intensity. However, due to the attenuation of ultrasonic waves, the discharge intensity of insulation defects assessed at different detection distances varies. Ultimately, the aforementioned disclosed solution is significantly affected by the detection distance, and it is impossible to establish a unified reference standard for determining the discharge intensity of insulation defects.

[0006] Therefore, studying the insulation defect detection technology of distribution overhead line insulators and cable transfer terminals to achieve efficient, flexible, accurate and visual insulation defect detection and evaluation is an urgent problem to be solved in the field of such technology research, product design and application.

[0007] Summary of the Invention

[0008] The present application provides a non-contact live detection device and live detection method, which can locate the spatial coordinates of insulation defects, improve the accuracy of evaluating the discharge intensity of insulation defects, and realize the visualization of insulation defects.

[0009] In a first aspect, the present application provides a non-contact charged detection device, comprising a processing unit, and a detection unit and an image acquisition unit both communicatively connected to the processing unit;

[0010] The detection unit includes an electromagnetic wave sensor and at least three ultrasonic sensors;

[0011] The image acquisition unit is configured to acquire images of insulation defects of the overhead line detected by the detection unit;

[0012] The processing unit is configured to obtain the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity and ultrasonic wave intensity of the insulation defect position according to the detection results of the detection unit, and mark the insulation defect image.

[0013] In one embodiment, the detection device includes a detection base plate, the detection unit and the image acquisition unit are fixed on the detection base plate, the image acquisition unit is located at the geometric center of all ultrasonic sensors, and the acquisition direction of the image acquisition unit is the same as the detection direction of the ultrasonic sensor.

[0014] In one embodiment, the detection device includes a data acquisition unit communicatively connected to the processing unit, which converts the ultrasonic signal and the electromagnetic wave signal of the ultrasonic sensor and the electromagnetic wave sensor into digital signals.

[0015] In one embodiment, an ultrasonic wave condenser is fixed on the ultrasonic sensor. The ultrasonic wave condenser is in a parabolic shape, and the ratio of the focal length of the parabola to the radius of the ultrasonic sensor is 1:2.

[0016] In one embodiment, the detection device includes an ultrasonic conditioning circuit that matches the number of ultrasonic sensors. The ultrasonic conditioning circuit includes a noise amplification circuit and an amplification filtering circuit that are interconnected. The input end of the noise amplification circuit is connected to the ultrasonic sensor and is configured to amplify the signal of the detection result of the ultrasonic sensor. The output end of the amplification filtering circuit is connected to the processing unit and is configured to amplify and filter the signal output by the noise amplification circuit.

[0017] In one embodiment, the noise amplification circuit includes an instrumentation amplifier, a first positive power supply circuit, and a first negative power supply circuit;

[0018] The positive input pin and the negative input pin of the instrumentation amplifier are connected to the ultrasonic sensor, the positive input pin is connected to the first resistor and then to ground, the positive input pin and the negative input pin are connected through the second resistor, the negative input pin is connected to the third resistor and then to ground, and a fourth resistor is connected between the two gain setting pins of the instrumentation amplifier;

[0019] The first positive power supply circuit includes a first anti-interference device and a first grounding capacitor, two sides of the first anti-interference device are respectively connected to the positive power supply and the positive power supply pin of the instrumentation amplifier, and two sides of the first grounding capacitor are respectively connected to the ground and the positive power supply pin of the instrumentation amplifier;

[0020] The first negative power supply circuit includes a second anti-interference device and a second grounding capacitor, two sides of the second anti-interference device are respectively connected to the negative power supply and the negative power supply pin of the instrumentation amplifier, and two sides of the second grounding capacitor are respectively grounded and connected to the negative power supply pin of the instrumentation amplifier;

[0021] The output pin of the instrumentation amplifier is connected to the fifth capacitor and then to the amplification and filtering circuit.

[0022] In one embodiment, the amplifying and filtering circuit may include an operational amplifier, a second positive power supply circuit, and a second negative power supply circuit;

[0023] The first signal negative input pin of the operational amplifier is connected to the output end of the noise amplification circuit through a sixth resistor, the first signal positive input pin of the operational amplifier is connected to the seventh resistor and then to ground, the first output pin of the operational amplifier is connected to the first signal negative input pin through a sixth capacitor, the first output pin of the operational amplifier is connected to the output end of the noise amplification circuit through a fifth resistor, the first output pin of the operational amplifier is connected in series with the seventh capacitor, the ninth resistor, and the eighth capacitor in sequence, and then connected to the second output pin of the operational amplifier, the second output pin of the operational amplifier is connected between the seventh capacitor and the ninth resistor through an eighth resistor, the second signal negative input pin of the operational amplifier is connected between the ninth resistor and the eighth capacitor, the second signal positive input pin of the operational amplifier is connected to the tenth circuit and then to ground, and the second output pin of the operational amplifier is connected to the processing unit;

[0024] The second positive power supply circuit includes a fourth anti-interference device and a third grounded capacitor, two sides of the fourth anti-interference device are respectively connected to the positive power supply and the positive power supply pin of the operational amplifier, and two sides of the eleventh capacitor and the twelfth capacitor after being connected in parallel are respectively grounded and connected to the positive power supply pin of the operational amplifier;

[0025] The second negative power supply circuit includes a third anti-interference device and a fourth grounding capacitor. The two sides of the third anti-interference device are respectively connected to the negative power supply and the negative power supply pin of the operational amplifier. The two sides of the ninth capacitor and the tenth capacitor after being connected in parallel are respectively grounded and connected to the negative power supply pin of the operational amplifier.

[0026] In one embodiment, the detection device includes an electromagnetic conditioning circuit, an input end of the electromagnetic conditioning circuit is connected to the electromagnetic wave sensor, and an output end of the electromagnetic conditioning circuit is connected to the processing unit, and is configured to filter the detection result of the electromagnetic wave sensor.

[0027] In one embodiment, the input end of the electromagnetic conditioning circuit includes a first AC input end and a second AC input end, and the output end of the electromagnetic conditioning circuit includes a first AC output end and a second AC output end, the first AC input end and the first AC output end are connected via a first resistor, a first capacitor, a first inductor, a third capacitor, a third inductor, a fifth capacitor, a fifth inductor, a seventh capacitor, and a seventh inductor connected in series in sequence, the second AC input end is connected to the second AC output end, the second AC input end is connected between the first inductor and the third capacitor via the second inductor and the second capacitor in parallel, the second AC input end is connected between the third inductor and the fifth capacitor via the fourth inductor and the fourth capacitor in parallel, and the sixth inductor and the sixth capacitor are connected between the fifth inductor and the seventh capacitor in parallel, and the first AC output end and the second AC output end are connected via a second resistor.

[0028] In one embodiment, obtaining the spatial coordinates and two-dimensional pixel coordinates of the insulation defect position according to the detection result of the detection unit includes:

[0029] Obtain the distance between the insulation defect location and each ultrasonic sensor based on the detection results of the electromagnetic wave sensor and all ultrasonic sensors;

[0030] The spatial coordinates of the insulation defect position are obtained according to the distance between the insulation defect position and each ultrasonic sensor, and the distance between adjacent ultrasonic sensors;

[0031] The spatial coordinates of the insulation defect position are transformed into pixel coordinates according to the parameters of the image acquisition unit.

[0032] In one embodiment, obtaining the distance between the insulation defect location and each ultrasonic sensor based on the detection results of the electromagnetic wave sensor and all ultrasonic sensors includes:

[0033] Acquire electromagnetic signals and ultrasonic signals detected by electromagnetic wave sensors and all ultrasonic sensors;

[0034] Extract the electromagnetic signal and ultrasonic signal to obtain the corresponding arrival time respectively;

[0035] Determining the time delay between the electromagnetic signal and the ultrasonic signal based on the discharge characteristics at the insulation defect location and the arrival times of the electromagnetic signal and the ultrasonic signal;

[0036] Based on the time delay between the electromagnetic signal and the ultrasonic signal, the distance between the insulation defect location and each ultrasonic sensor is obtained.

[0037] In one embodiment, extracting the ultrasonic signal to obtain the corresponding arrival time includes:

[0038] Obtaining average energy of the ultrasonic signal according to the ultrasonic signal detected within the duration;

[0039] dividing the duration into a plurality of first preset time periods;

[0040] Obtaining an ultrasonic signal energy curve according to the average energy of the ultrasonic signal and the energy of the ultrasonic signal in a first preset time period;

[0041] Screening out the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve within the first preset time period according to the ultrasonic signal energy curve;

[0042] Obtaining the arrival time of the ultrasonic signal according to the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve;

[0043] Extracting the electromagnetic signal to obtain the corresponding arrival time includes:

[0044] Obtaining a threshold expansion coefficient of the electromagnetic wave sensor for detecting electromagnetic signals according to a signal-to-noise ratio of the electromagnetic wave sensor;

[0045] The electromagnetic detection threshold is obtained according to the threshold expansion coefficient and the electromagnetic signal within the duration;

[0046] dividing the duration into a plurality of second preset time periods;

[0047] Screening out the electromagnetic signal that reaches the electromagnetic detection threshold for the first time within the second preset time period according to the second preset time period and the electromagnetic detection threshold;

[0048] The corresponding arrival time is determined according to the electromagnetic signal that reaches the electromagnetic detection threshold for the first time.

[0049] In one embodiment, determining the time delay between the electromagnetic signal and the ultrasonic signal based on the discharge characteristics at the insulation defect location and the arrival times of the electromagnetic signal and the ultrasonic signal includes:

[0050] Obtaining a correlation accumulation factor based on arrival times of the electromagnetic signal and the ultrasonic signal, propagation speed of the electromagnetic signal, and a preset minimum resolution of the time delay;

[0051] By calculating the maximum value of the correlation accumulation factor, the delay estimation value is obtained;

[0052] According to the arrival times of the electromagnetic signal and the ultrasonic signal, and the preset minimum delay resolution, multiple delay increase interval ranges are obtained;

[0053] Determining, based on a plurality of delay increase intervals, a delay increase interval in which the delay estimate value lies;

[0054] Determining the arrival times of the corresponding electromagnetic signals and ultrasonic signals according to the determined time delay increase interval range;

[0055] According to the given arrival times of the electromagnetic signal and the ultrasonic signal, the time delay between the electromagnetic signal and the ultrasonic signal is obtained.

[0056] In one embodiment, obtaining the spatial coordinates of the insulation defect location based on the distance between the insulation defect location and the ultrasonic sensor and the detection results of all ultrasonic sensors includes:

[0057] Based on the high-order cumulant method and the ultrasonic signals detected by all ultrasonic sensors, the time delay between different ultrasonic signals is obtained;

[0058] The distances between all ultrasonic sensors and the insulation defect locations are obtained based on the time delays between different ultrasonic signals;

[0059] Establish a three-dimensional spatial coordinate system and obtain the spatial coordinate relationship of the insulation defect position based on the distance between adjacent ultrasonic sensors;

[0060] The spatial coordinates of the insulation defect position are determined based on the distances between all ultrasonic sensors and the insulation defect position and the spatial coordinate relationship.

[0061] In one embodiment, based on a high-order cumulant method and ultrasonic signals detected by all ultrasonic sensors, the time delay between different ultrasonic signals is obtained, including:

[0062] All ultrasonic sensors are combined in pairs to form multiple ultrasonic sensor groups;

[0063] Constructing a cumulative coefficient for the ultrasonic signal detected by each ultrasonic sensor group;

[0064] By calculating the maximum value of all the cumulative coefficients, the time delay between the ultrasonic signals detected by the two ultrasonic sensors in each ultrasonic sensor group is obtained.

[0065] In one embodiment, transforming the spatial coordinates of the insulation defect location into pixel coordinates according to the parameters of the image acquisition unit includes:

[0066] The three-dimensional space coordinate system where the insulation defect is located is transformed by rotation and translation to obtain the camera coordinate system;

[0067] The camera coordinate system is converted into the image plane coordinate system based on the principle of similar triangles;

[0068] According to the geometric relationship between the image plane coordinate system and the pixel coordinate system, the image plane coordinate system is converted into the pixel coordinate system;

[0069] According to the pixel coordinate system and the spatial coordinates of the insulation defect position, the two-dimensional pixel coordinates are obtained.

[0070] In one embodiment, obtaining the ultrasonic intensity at the insulation defect location based on the detection result of the detection unit includes:

[0071] Collect the temperature and humidity of the current environment;

[0072] Get the attenuation coefficient of ultrasound in the current environment based on temperature and humidity;

[0073] According to the obtained arrival time of the ultrasonic signal, the signal amplitude corresponding to different arrival time is obtained;

[0074] The maximum value of the signal amplitude corresponding to different arrival times is screened to obtain the ultrasonic detection intensity;

[0075] The ultrasonic intensity at the insulation defect location is obtained according to the distance between the insulation defect location and the ultrasonic sensor, the ultrasonic detection intensity and the attenuation coefficient.

[0076] In one embodiment, marking an insulation defect image includes:

[0077] Mark the insulation defect location in the insulation defect image according to the two-dimensional pixel coordinates of the insulation defect location;

[0078] matching the distances between the plurality of ultrasonic sensors and the insulation defect location, the plurality of electromagnetic wave intensities, and the plurality of ultrasonic wave intensities with the marked insulation defect location;

[0079] The distance between the matched ultrasonic sensor and the insulation defect position, the electromagnetic wave intensity, and the ultrasonic wave intensity are displayed at the insulation defect position in the insulation defect image.

[0080] In a second aspect, the present application further provides a method for detecting a charged object, which is applied to the above-mentioned non-contact charged object detection device, comprising:

[0081] The overhead line is inspected by a detection unit of the detection device, and an image acquisition unit of the detection device is used to acquire an image of the overhead line in a predetermined direction to obtain an insulation defect image;

[0082] Obtaining the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity of the insulation defect location based on the detection results of the detection unit;

[0083] Insulation defect images are marked according to spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] FIG1 is a schematic diagram of a non-contact charge detection device provided in an embodiment of the present application;

[0085] FIG2 is a circuit diagram of a noise amplification circuit provided in an embodiment of the present application;

[0086] FIG3 is a circuit diagram of an amplifying and filtering circuit provided in an embodiment of the present application;

[0087] FIG4 is a circuit diagram of an electromagnetic conditioning circuit provided in an embodiment of the present application;

[0088] FIG5 is a flow chart of obtaining the spatial coordinates and two-dimensional pixel coordinates of an insulation defect position provided by an embodiment of the present application;

[0089] FIG6 is a flow chart of obtaining the distance between the insulation defect location and the ultrasonic sensor according to an embodiment of the present application;

[0090] FIG7 is a flow chart of a time delay between an electromagnetic signal and an ultrasonic signal provided by an embodiment of the present application;

[0091] FIG8 is a flow chart of obtaining the spatial coordinates of an insulation defect location according to an embodiment of the present application;

[0092] FIG9 is a schematic diagram of constructing a three-dimensional space coordinate system based on a detection device according to an embodiment of the present application;

[0093] FIG10 is a schematic diagram of converting a three-dimensional space coordinate system into a camera coordinate system according to an embodiment of the present application;

[0094] FIG11 is a schematic diagram of converting a camera coordinate system into an image plane coordinate system according to an embodiment of the present application;

[0095] FIG12 is a schematic diagram of converting an image plane coordinate system into a pixel coordinate system according to an embodiment of the present application;

[0096] FIG13 is a flow chart of a non-contact live detection method for insulation defects of a power distribution overhead line provided by an embodiment of the present application;

[0097] FIG14 is a schematic diagram of an application of a non-contact charged detection device provided in an embodiment of the present application.

[0098] Explanation of the accompanying symbols: 1-ultrasonic sensor, 2-electromagnetic wave sensor, 3-image acquisition unit, 4-processing unit, 5-ultrasonic conditioning circuit, 6-electromagnetic conditioning circuit. DETAILED DESCRIPTION

[0099] The above technical solution will be described below with reference to the accompanying drawings and specific implementation methods. The described embodiments are only part of the embodiments of this application.

[0100] As shown in Figure 1, the present application provides a non-contact live detection device, including a processing unit 4, and a detection unit and an image acquisition unit 3, both of which are communicatively connected to the processing unit 4; the detection unit includes an electromagnetic wave sensor 2 and at least three ultrasonic sensors 1; the image acquisition unit 3 is configured to acquire insulation defect images of the overhead line detected by the detection unit; the processing unit 4 is configured to obtain the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity and ultrasonic wave intensity of the insulation defect position according to the detection results of the detection unit, and mark the insulation defect image.

[0101] The detection device of the present application may include a detection base plate, a detection unit and an image acquisition unit 3 fixed to the detection base plate. The image acquisition unit 3 is located at the geometric center of all ultrasonic sensors 1, and the acquisition direction of the image acquisition unit 3 is the same as the detection direction of the ultrasonic sensor 1. This improves the appearance of the detection device and allows the camera coordinate system and the spatial coordinate system to coincide, facilitating subsequent coordinate transformation and solution. The detection unit is equipped with three ultrasonic sensors 1, which form an equilateral triangle. In practical applications, an ultrasonic wave condenser is fixed to the ultrasonic sensor 1. The ultrasonic wave condenser is in the shape of a parabola, with the focal length of the parabola and the radius of the ultrasonic sensor 1 in a ratio of 1:2. This can better achieve wave focusing and shielding, thereby improving the ultrasonic sensitivity and directionality of long-range detection. Taking into account the wave focusing effect and directionality of the wave condenser, the ultrasonic sensor 1 is placed in the plane where the parabola's focus is located, and the diameter of the ultrasonic sensor 1 is equal to four times the focal length. At this point, the ultrasonic sensor 1 completely occupies the entire plane of the parabola's focus. The opening size of the wave condenser is minimized as much as possible without affecting the wave focusing effect to enhance the wave condenser's directionality.

[0102] The ultrasonic sensor 1 has a center frequency of 40 kHz, a bandwidth of 38-42 kHz, and a sensitivity of -75 ubar, and can detect ultrasonic signals generated by insulation defects.

[0103] The detection device of the present application may include an ultrasonic conditioning circuit 5 that matches the number of all ultrasonic sensors 1. The ultrasonic conditioning circuit 5 includes a noise amplification circuit and an amplification filtering circuit that are interconnected. The input end of the noise amplification circuit is connected to the ultrasonic sensor 1 and is configured to amplify the signal of the detection result of the ultrasonic sensor 1. The output end of the amplification filtering circuit is connected to the processing unit 4 and is configured to amplify and filter the signal output by the noise amplification circuit.

[0104] In an actual application scenario, as shown in Figure 2, the noise amplification circuit includes an instrumentation amplifier, a first positive power supply circuit and a first negative power supply circuit; the positive input pin and the negative input pin of the instrumentation amplifier are connected to the ultrasonic sensor 1, the positive input pin is connected to the first resistor and then grounded, the positive input pin and the negative input pin are connected through the second resistor, the negative input pin is connected to the third resistor and then grounded, and a fourth resistor is connected between the two gain setting pins of the instrumentation amplifier; the first positive power supply circuit includes a first anti-interference device and a first grounding capacitor, the two sides of the first anti-interference device are respectively connected to the positive power supply and the positive power supply pin of the instrumentation amplifier, and the two sides of the first grounding capacitor are respectively grounded and connected to the positive power supply pin of the instrumentation amplifier; the first negative power supply circuit includes a second anti-interference device and a second grounding capacitor, the two sides of the second anti-interference device are respectively connected to the negative power supply and the negative power supply pin of the instrumentation amplifier, and the two sides of the second grounding capacitor are respectively grounded and connected to the negative power supply pin of the instrumentation amplifier; the output pin of the instrumentation amplifier is connected to the fifth capacitor and then connected to the amplification and filtering circuit.

[0105] In one embodiment, the first grounding capacitor includes a first capacitor and a second capacitor connected in parallel, and the second grounding capacitor includes a third capacitor and a fourth capacitor connected in parallel.

[0106] In an actual application scenario, as shown in FIG3 , the amplifying and filtering circuit may include an operational amplifier, a second positive power supply circuit and a second negative power supply circuit; the first signal negative input pin of the operational amplifier is connected to the output end of the noise amplifying circuit through a sixth resistor, the first signal positive input pin of the operational amplifier is connected to the seventh resistor and then to ground, the first output pin of the operational amplifier is connected to the first signal negative input pin through a sixth capacitor, the first output pin of the operational amplifier is connected to the output end of the noise amplifying circuit through a fifth resistor, the first output pin of the operational amplifier is connected in series with the seventh capacitor, the ninth resistor and the eighth capacitor in sequence and then connected to the second output pin of the operational amplifier, the second output pin of the operational amplifier is connected between the seventh capacitor and the ninth resistor through an eighth resistor, and the operational amplifier is connected to the seventh capacitor and the ninth resistor in sequence. The second signal negative input pin of the operational amplifier is connected between the ninth resistor and the eighth capacitor, the second signal positive input pin of the operational amplifier is connected to the tenth circuit and then grounded, and the second output pin of the operational amplifier is connected to the processing unit 4; the second positive power supply circuit includes a fourth anti-interference device and a third grounded capacitor, and the two sides of the fourth anti-interference device are respectively connected to the positive power supply and the positive power supply pin of the operational amplifier, and the two sides of the eleventh capacitor and the twelfth capacitor are respectively grounded and connected to the positive power supply pin of the operational amplifier; the second negative power supply circuit includes a third anti-interference device and a fourth grounded capacitor, and the two sides of the third anti-interference device are respectively connected to the negative power supply and the negative power supply pin of the operational amplifier, and the two sides of the ninth capacitor and the tenth capacitor are respectively grounded and connected to the negative power supply pin of the operational amplifier.

[0107] The third grounding capacitor includes an eleventh capacitor and a twelfth capacitor connected in parallel, and the fourth grounding capacitor includes a ninth capacitor and a tenth capacitor connected in parallel.

[0108] The noise amplification circuit is set up to use the low-noise instrumentation amplifier AD8429 to perform low-noise amplification on small signals with a gain of about 10 times. The amplification and filtering circuit is set up to use the low-noise operational amplifier LT6231 to amplify and filter the signal output by the noise amplification circuit. The filtering is to filter out the interference sound signals other than the ultrasonic signal generated by the insulation defect. The passband frequency is 35-45kHz. The LT6231 chip integrates a two-stage operational amplifier. The gain of the two-pole circuit is about 100 times, the center frequency is about 40kHz, and the bandwidth is about 5kHz. The passband gain of the ultrasonic conditioning circuit 5 obtained by cascading the two circuits is about 60dB, and the passband frequency corresponding to the -3dB bandwidth is about 38-42kHz, which can achieve low-noise amplification of the insulation defect ultrasonic signal.

[0109] The electromagnetic wave sensor 2 of the present application utilizes an electromagnetic antenna operating at a frequency of 20-100 MHz and a gain of 3 dBi, capable of detecting electromagnetic signals generated by insulation defects. The detection device may include an electromagnetic conditioning circuit 6 , the input of which is connected to the electromagnetic wave sensor 2 , and the output of which is connected to the processing unit 4 , configured to filter the detection results of the electromagnetic wave sensor 2 .

[0110] In an actual application scenario, as shown in Figure 4, the input end of the electromagnetic conditioning circuit 6 includes a first AC input end and a second AC input end, and the output end of the electromagnetic conditioning circuit 6 includes a first AC output end and a second AC output end. The first AC input end and the first AC output end are connected in series through a first resistor, a first capacitor, a first inductor, a third capacitor, a third inductor, a fifth capacitor, a fifth inductor, a seventh capacitor and a seventh inductor. The second AC input end is connected to the second AC output end. The second AC input end is connected between the first inductor and the third capacitor after being connected in parallel through the second inductor and the second capacitor, and is connected between the third inductor and the fifth capacitor after being connected in parallel through the fourth inductor and the fourth capacitor. It is connected between the fifth inductor and the seventh capacitor after being connected in parallel through the sixth inductor and the sixth capacitor. The first AC output end and the second AC output end are connected through a second resistor.

[0111] The electromagnetic conditioning circuit 6 adopts a 7th-order Butterworth passive bandpass filter circuit design. The operating frequency corresponding to the -3dB bandwidth is approximately 25-75MHz. The attenuation of broadcast and radio interference signals with common frequencies below 20MHZ and above 90MHz can reach more than 40dB, which can realize the filtering processing of insulation defect electromagnetic signals.

[0112] The detection device of the present application may also include a data acquisition unit in communication with the processing unit 4, which converts the ultrasonic and electromagnetic wave signals from the ultrasonic sensor 1 and the electromagnetic wave sensor 2 into digital signals. Four-channel data can be sampled in real time with 14-bit resolution, with a sampling rate of up to 1G / s. Since the ultrasonic sensor 1 and the electromagnetic wave sensor 2 only detect and output analog signals, the signal analysis and processing performed by the processing unit 4 is all done on digital signals. The data acquisition unit can convert the analog signals output by the ultrasonic sensor 1 and the electromagnetic wave sensor 2 into digital signals, thereby enabling the processing unit 4 to perform signal analysis and processing.

[0113] As shown in FIG5 , the processing unit 4 obtains the spatial coordinates and two-dimensional pixel coordinates of the insulation defect position according to the detection results of the detection unit, which may include:

[0114] The distance between the insulation defect location and each ultrasonic sensor 1 is obtained based on the detection results of the electromagnetic wave sensor 2 and all ultrasonic sensors 1; the spatial coordinates of the insulation defect location are obtained based on the distance between the insulation defect location and each ultrasonic sensor 1, as well as the distance between adjacent ultrasonic sensors 1; and the spatial coordinates of the insulation defect location are transformed into pixel coordinates based on the parameters of the image acquisition unit 3.

[0115] As shown in FIG6 , the distance between the insulation defect position and the ultrasonic sensor 1 is obtained based on the detection results of the electromagnetic wave sensor 2 and the ultrasonic sensor 1 , including:

[0116] Acquire the electromagnetic signals and ultrasonic signals detected by the electromagnetic wave sensor 2 and all ultrasonic sensors 1; extract the electromagnetic signals and ultrasonic signals to obtain corresponding arrival times, respectively; wherein the arrival time represents the time when the electromagnetic signal and ultrasonic signal arrive at the corresponding electromagnetic wave sensor 2 and ultrasonic sensor 1, respectively, from the insulation defect location; determine the time delay between the electromagnetic signal and the ultrasonic signal based on the discharge characteristics of the insulation defect location and the arrival times of the electromagnetic signal and the ultrasonic signal; wherein the time delay represents the time it takes for the electromagnetic signal and ultrasonic signal generated by the insulation defect to reach the electromagnetic wave sensor 2 and ultrasonic sensor 1, respectively; based on the time delay between the electromagnetic signal and the ultrasonic signal, obtain the distance between the insulation defect location and each ultrasonic sensor 1.

[0117] In order to effectively estimate the time delay between acoustic and electrical signals (ultrasonic signals and electromagnetic signals), it is first necessary to extract the arrival time of the ultrasonic signal and the electromagnetic signal. Considering that the oscillation duration of the ultrasonic detection waveform is long, similar to a sinusoidal oscillation wave, gradually increasing from zero, the energy method is used to extract the arrival time of the ultrasonic signal. The energy method obtains the arrival time of the ultrasonic signal by calculating the inflection point of the ultrasonic signal energy curve. Assume that the collected ultrasonic signal sequence is U ult,n, with a duration of T, the average energy E0 of the ultrasonic signal can be calculated and the discriminant of the signal energy curve can be established. By calculating the minimum value of the discriminant of the signal energy curve, the time corresponding to the inflection point of the ultrasonic signal energy curve is obtained, which is the arrival time of the ultrasonic signal.

[0118] The average energy is:

[0119] The established signal energy curve discriminant is:

[0120] Since insulation defect discharge is generated periodically under the action of power frequency voltage, there will be multiple ultrasonic signal arrival times. The corresponding arrival times are obtained by extracting the ultrasonic signal, including:

[0121] The average energy of the ultrasonic signal is obtained according to the ultrasonic signal detected during the duration; the duration is divided into a plurality of first preset time periods; and an ultrasonic signal energy curve is obtained according to the average energy of the ultrasonic signal and the energy of the ultrasonic signal during the first preset time period, satisfying the following relationship:

[0122] Where, P j represents the ultrasonic signal energy curve within the first preset time period, represents the energy of the mth ultrasonic signal within the first preset time period, represents the energy of the i-th ultrasonic signal within the duration, j is the number of ultrasonic signals detected within the first preset time period, j≤n, m represents the sequence number of the ultrasonic signal in the j ultrasonic signals, n represents the number of ultrasonic signals detected within the duration, i represents the sequence number of the ultrasonic signal in the n ultrasonic signals, and T is the duration; wherein, the signal detected by the ultrasonic sensor 1 is an analog signal, and the processing unit 4 can only process digital signals during signal analysis, so the data acquisition device converts the analog signal into a discrete digital signal, and at this time n is the number of ultrasonic signals detected after the analog signal is converted into a digital signal; the duration is the duration of the ultrasonic signal obtained by the ultrasonic sensor 1 each time, that is, the total time of a single detection by the ultrasonic sensor 1; according to the ultrasonic signal energy curve, the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve within the first preset time period is screened out; according to the ultrasonic signal energy curve, the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve is obtained. The arrival time of the ultrasonic signal is obtained.

[0123] The present application obtains the arrival time of the ultrasonic signal by continuously calculating the minimum values ​​within different first preset time periods. The minimum value can be determined by comparing the minimum value within the first preset time period with the values ​​at the left and right endpoints of the first preset time period. When the minimum value is less than the values ​​at the two endpoints, the minimum value is the minimum value, and the corresponding moment is the arrival time of the ultrasonic signal. When the minimum value is greater than or equal to any of the values ​​at the two endpoints, there is no minimum value within the first preset time period.

[0124] Since the waveform of the electromagnetic signal is similar to a pulse sequence, the signal energy does not increase from zero, so the threshold method is used to extract the arrival time of the electromagnetic signal. The corresponding arrival time is obtained by extracting the electromagnetic signal, including:

[0125] The threshold expansion coefficient for electromagnetic wave sensor 2 to detect electromagnetic signals is obtained based on the signal-to-noise ratio of the current detection environment. When the electromagnetic interference on site is large, the detection threshold can be increased to correspondingly improve the signal-to-noise ratio. If the detection threshold adjustment function is not set, the threshold expansion coefficient is taken as 5. The electromagnetic detection threshold is obtained based on the threshold expansion coefficient and the electromagnetic signal within the duration, satisfying the following relationship:

[0126] Where U thr represents the electromagnetic detection threshold, k represents the threshold expansion coefficient, and its value range is 1-10, n' represents the number of electromagnetic signals detected within the duration, and i' represents the sequence number of the electromagnetic signals sorted by the detection time. Represents the energy of the i'th electromagnetic signal; divides the duration into multiple second preset time periods; filters out the electromagnetic signal that reaches the electromagnetic detection threshold for the first time within the second preset time period based on the second preset time period and the electromagnetic detection threshold; determines the corresponding arrival time based on the electromagnetic signal that reaches the electromagnetic detection threshold for the first time.

[0127] The first preset time period and the second preset time period can have the same width or different widths, which can be selected according to actual needs. For example, in this application, the width of the first preset time period and the second preset time period is 5ms.

[0128] When a real insulation defect discharge occurs, it is accompanied by a series of pulses with random time and amplitude. It is impossible to identify the matching pulses between the ultrasonic signal arrival time and the electromagnetic signal arrival time based solely on the detection results of a single pulse. Considering the temporal randomness of the pulses, there is no temporal correlation between any two pulses in the same time series, while each pulse in the ultrasonic arrival time series can find a pulse in the electromagnetic arrival time series with a fixed time difference T. AE According to this statistical characteristic, a statistical correlation cumulative factor Q(t) is defined to calculate the time delay T between the acoustic and electrical signals.AE .

[0129] As shown in FIG7 , based on the discharge characteristics at the insulation defect location and the arrival times of the electromagnetic signal and the ultrasonic signal, the time delay between the electromagnetic signal and the ultrasonic signal is determined, including:

[0130] Based on the arrival times of the electromagnetic signal and the ultrasonic signal, the propagation speed of the electromagnetic signal, and the preset minimum resolution of the time delay, the correlation accumulation factor is obtained, which satisfies the following relationship:

[0131] Where Q(t) represents the correlation accumulation factor, a represents the number of ultrasonic signal arrival times, b represents the number of electromagnetic signal arrival times, i" represents the ultrasonic signal number sorted by detection time, j" represents the electromagnetic signal number sorted by detection time, Δt represents the preset minimum delay resolution, v' represents the propagation speed of the electromagnetic signal, and T ult,i" represents the i-th arrival time of the ultrasonic signal, T ele,j" represents the j'th arrival time of the electromagnetic signal, and t represents the estimated time delay between the electromagnetic signal and the ultrasonic signal; the estimated time delay is obtained by calculating the maximum value of the correlation accumulation factor; multiple delay increase intervals are obtained based on the arrival times of the electromagnetic signal and the ultrasonic signal and a preset minimum delay resolution; based on the multiple delay increase intervals, the delay increase interval in which the estimated time delay lies is determined; based on the determined delay increase interval, the corresponding arrival times of the electromagnetic signal and the ultrasonic signal are determined; and based on the determined arrival times of the electromagnetic signal and the ultrasonic signal, the time delay between the electromagnetic signal and the ultrasonic signal is obtained.

[0132] In one embodiment, the delay T can be obtained by the correlation accumulation factor AE The key is: when calculating the correlation accumulation factor Q(t), the delay increases with a step size of Δt. When t reaches (T AE -Δt,T AE +Δt) range, the maximum value of Q(t) can be obtained. max Therefore, the maximum value Q of Q(t) can be obtained by max Calculate the time delay T between the acoustic and electrical signals AE .

[0133] As shown in FIG8 , the spatial coordinates of the insulation defect location are obtained based on the distance between the insulation defect location and each ultrasonic sensor 1 and the detection results of all ultrasonic sensors 1 , including:

[0134] Based on the high-order cumulant method and the ultrasonic signals detected by all ultrasonic sensors 1, the time delay between different ultrasonic signals is obtained; the distance between all ultrasonic sensors 1 and the insulation defect position is obtained according to the time delay between different ultrasonic signals; a three-dimensional spatial coordinate system is established, and the spatial coordinate relationship of the insulation defect position is obtained according to the distance between adjacent ultrasonic sensors 1; the spatial coordinates of the insulation defect position are determined according to the distance between all ultrasonic sensors 1 and the insulation defect position in combination with the spatial coordinate relationship; as shown in Figure 9, establishing the three-dimensional spatial coordinate system includes: the three-dimensional spatial coordinate system is established with the optical center of the camera as the origin O, the axes parallel to the X and Y axes of the image captured by the camera as the x-axis and y-axis, and the optical axis of the camera as the z-axis.

[0135] Based on the distances between all ultrasonic sensors 1 and their corresponding coordinates, a spatial coordinate relationship can be constructed. This application takes three ultrasonic sensors 1 as an example, and the three ultrasonic sensors 1 form an equilateral triangle with a side length of D. Here, the detection unit may include a first ultrasonic sensor A, a second ultrasonic sensor B, and a third ultrasonic sensor C; the spatial coordinate relationship includes:

[0136] Where (x, y, z) represents the spatial coordinates of the insulation defect location, D represents the distance between adjacent ultrasonic sensors 1, L1 represents the distance from the insulation defect location P to the first ultrasonic sensor A, L2 represents the distance from the insulation defect location P to the second ultrasonic sensor B, and L3 represents the distance from the insulation defect location P to the third ultrasonic sensor C.

[0137] This application can obtain the distance between the ultrasonic sensor 1 and the insulation defect location through the detection results of the ultrasonic sensor 1 and the electromagnetic wave sensor 2. If the ultrasonic sensor 1 corresponding to the obtained distance is the first ultrasonic sensor, that is, L1 is calculated, L2 and L3 need to be calculated. If the detection results of the ultrasonic sensor 1 and the electromagnetic wave sensor 2 are combined for calculation, it will be susceptible to interference such as noise when calculating the arrival time of the signals of different ultrasonic sensors 1, and the redundant information between the sensors is not fully utilized, which will cause a large calculation error. This application takes into account that the signals detected by different ultrasonic sensors 1 are all generated by the same insulation defect discharge, and there is a correlation between the ultrasonic signals. The time delay estimation algorithm based on correlation has a higher calculation accuracy. Therefore, this application calculates L2 and L3 by calculating the signal delay between adjacent ultrasonic sensors 1, which can be calculated using the following formula: L2 = L1-T AB v′ L3=L1-T AC v′

[0138] Where: v' is the speed of sound, T AB is the time delay of the signal between the first ultrasonic sensor and the second ultrasonic sensor; T ACis the time delay of the signal between the first ultrasonic sensor and the third ultrasonic sensor; when T is calculated AB and T AC L2 and L3 can then be calculated using the above formula. By solving the above spatial coordinate relationships, the three-dimensional spatial coordinates of the insulation defect can be calculated.

[0139] Based on the similarity between different ultrasonic signal delays, the cumulative coefficient between the two ultrasonic signals at different shift values ​​is calculated. The shift value corresponding to the maximum cumulative coefficient is the time delay between the signals. J(D') is calculated for different time delays D', and the D' corresponding to the maximum value is the time delay between the ultrasonic signals to be determined.

[0140] Based on the high-order cumulant method and the ultrasonic signals detected by all ultrasonic sensors 1, the time delays between different ultrasonic signals are obtained, including:

[0141] All ultrasonic sensors 1 are combined in pairs to form multiple ultrasonic sensor groups. For the ultrasonic signals detected by each ultrasonic sensor group, a cumulative coefficient is constructed to satisfy the following relationship:

[0142] Where J(D') represents the cumulative coefficient, c' 4N {} represents a fourth-order cumulant function, x1 represents an ultrasonic signal detected by one ultrasonic sensor 1, x2 represents an ultrasonic signal detected by another ultrasonic sensor 1, n1 represents the number of ultrasonic signals detected by the ultrasonic sensor 1, and D' represents the time delay between the ultrasonic signals detected by the two ultrasonic sensors 1.

[0143] By calculating the maximum value of all cumulative coefficients, the time delay between the ultrasonic signals detected by the two ultrasonic sensors 1 in each ultrasonic sensor group is obtained. When the cumulative coefficient takes the maximum value, the corresponding D' is the signal delay to be calculated.

[0144] In order to improve the efficiency of on-site detection, the image acquisition unit 3 of the present application uses a high-definition camera to shoot the detection screen in real time, and uses marks on the screen to mark the position of the insulation defect to achieve visual positioning of the defect. Therefore, it is necessary to convert the three-dimensional spatial coordinates of the insulation defect into two-dimensional pixel coordinates on the shooting screen.

[0145] The spatial coordinate system, also called the world coordinate system, is a coordinate system established with the detection device as the reference. The pixel coordinate system is the two-dimensional coordinate system of the camera shooting picture. The defect coordinates obtained by solving the spatial positioning equation are the coordinates in the world coordinate system. In order to mark the defects with the camera in the shooting picture, a coordinate transformation is required to convert the three-dimensional world coordinates into two-dimensional pixel coordinates, which mainly includes three coordinate system transformations: the transformation between the world coordinate system and the camera coordinate system, the transformation between the camera coordinate system and the image plane coordinate system, and the transformation between the image plane coordinate system and the pixel coordinate system. Among them, the camera coordinate system takes the center of the camera lens as the origin, and the perpendicular lens plane outward is z c Axis, horizontal to the right is x c Axis, vertically downward is y c The coordinate system established by the axis.

[0146] In actual application scenarios, the spatial coordinates of the insulation defect position are transformed into pixel coordinates according to the parameters of the image acquisition unit 3, including:

[0147] As shown in Figure 10, the three-dimensional space coordinate system where the insulation defect location is located is transformed by rotation and translation to obtain the camera coordinate system, which satisfies the following relationship:

[0148] Where x w ,y w , z w is the three-dimensional space coordinate system, x c ,y c , z c is the camera coordinate system, R is the 3×3 rotation matrix of the image acquisition unit 3, and T is the 3×1 translation matrix of the image acquisition unit 3; wherein, the rotation matrix and the translation matrix are used to represent the transformation between the camera coordinate system and the world coordinate system. The camera coordinate system and the world coordinate system of this application coincide with each other, and the translation matrix T and the rotation matrix R are both unit matrices. If the camera coordinate system and the world coordinate system do not coincide, they can be obtained by mathematical transformation between the coordinate systems; as shown in Figure 11, the camera coordinate system is converted to the image plane coordinate system based on the principle of similar triangles, satisfying the following relationship:

[0149] Where x and y are the image plane coordinate system, and f is the focal length of the camera. The image plane coordinate system is the coordinate system of the two-dimensional imaging plane of the camera, and the distance between the origins of the camera coordinate system and the image plane coordinate system is the focal length of the camera.

[0150] As shown in FIG12 , according to the geometric relationship between the image plane coordinate system and the pixel coordinate system, the image plane coordinate system is converted into the pixel coordinate system to satisfy the following relationship:

[0151] Where u, v are pixel coordinates, f xIndicates the horizontal focal length of the camera, which is f / dx. dx is the physical size of a pixel point in the u-axis direction in the pixel coordinate system, and f y represents the vertical focal length of the camera, which is f / dy. dy is the physical size of a pixel point in the v-axis direction in the pixel coordinate system, and (u0, v0) is the coordinate of the origin of the image plane coordinate system in the pixel coordinate system. The two-dimensional pixel coordinates are obtained based on the pixel coordinate system and the spatial coordinates of the insulation defect position.

[0152] According to the geometric relationship between the image plane coordinate system and the pixel coordinate system, the image plane coordinate system is converted to the pixel coordinate system, including:

[0153] The following formula can be obtained from the geometric relationship between the image plane coordinate system and the pixel coordinate system:

[0154] Where: dx represents the physical size of a pixel on the photosensitive chip in the u-axis direction; dy represents the physical size of a pixel on the photosensitive chip in the v-axis direction. Writing the above formula in matrix form yields the following formula:

[0155] Combining the above formulas, the conversion formula between the world coordinate system and the pixel coordinate system is as follows:

[0156] Where: The intrinsic parameter matrix of the camera is an inherent property of the camera and does not change after leaving the factory. The parameters of the intrinsic parameter matrix can be calculated and calibrated based on the Zhang Zhengyou calibration method. Represents the extrinsic parameter matrix of the camera, which consists of the translation matrix T and the rotation matrix R. The camera coordinate system of the detection device of this application coincides with the world coordinate system, and the translation matrix T and the rotation matrix R are both unit matrices. Therefore, the pixel coordinate system can be obtained as:

[0157] When the coordinates of the insulation defect in the world coordinate system (x w ,y w ,z w ), the two-dimensional pixel coordinates (u, v) on the camera screen can be calculated using the following formula. After obtaining the pixel coordinates, the location of the partial discharge (insulation defect) can be marked on the camera image using a marker.

[0158] In order to achieve the conversion between the three-dimensional spatial coordinates and two-dimensional pixel coordinates of the insulation defect, it is necessary to obtain the intrinsic parameter matrix of the camera used. The detection device of this application uses a Sony IMX415 autofocus distortion-free camera, which supports up to 8 million high-definition pixel shooting. Due to the limited size of the display screen of the detection device, using an excessively large resolution cannot achieve a better display effect. Therefore, in order to reduce the burden of large pixel data processing, a resolution of 640x480 is used for the detection screen shooting and display.

[0159] The intrinsic parameter matrix of a camera describes the inherent properties of the camera, which are not affected by the external environment and will not change after the camera leaves the factory, such as the pixel size, the distance between the target object and the optical center, etc. The intrinsic parameter matrix of a camera can be obtained through camera calibration. The Zhang Zhengyou calibration method is the most commonly used camera calibration method. It has low requirements on the accuracy of the calibration object. It uses a flat chessboard to shoot multiple images at different angles, and the calibration parameters of the camera can be determined by the corresponding algorithm. This application uses the Zhang Zhengyou calibration method to calibrate the parameters of the camera, calculates the intrinsic parameter matrix of the camera, and converts the insulation defect coordinates in the world coordinate system into the two-dimensional pixel coordinate system, so that the insulation defects can be visually identified on the camera display.

[0160] The calibration process of Zhang Zhengyou's calibration method is based on the feature points of a plane chessboard. By adjusting the relative position of the camera and the plane chessboard, 10-20 groups of images at different angles and distances are taken, and the calibration parameters of the camera are solved using matrix decomposition and maximum likelihood method. OpenCV is a cross-platform computer vision and machine learning software library. It is lightweight and efficient. It consists of a series of C functions and a small number of C++ classes, and implements many general algorithms in image processing and computer vision. In the actual camera calibration process, after taking 10-20 camera calibration pictures, the Zhang Zhengyou camera calibration function library in OpenCV is used to calibrate the camera. For the camera of the detection device of this application, by using OpenCV for camera calibration multiple times and taking the average value, the multiple parameters of the internal parameter matrix of the camera used at a resolution of 640x480 are f, f, and f respectively. x =1483,f y =1488, u0=337 and v0=245.

[0161] The ultrasonic intensity at the insulation defect location is obtained based on the detection results of the detection unit, including:

[0162] The temperature and humidity of the current environment are collected; based on the temperature and humidity, the attenuation coefficient of the ultrasonic wave in the current environment is obtained; based on the arrival time of the obtained ultrasonic signal, the signal amplitude corresponding to different arrival times is obtained; the signal amplitude corresponding to different arrival times is screened for the maximum value to obtain the ultrasonic detection intensity; based on the distance between the insulation defect location and the ultrasonic sensor 1, the ultrasonic detection intensity, and the attenuation coefficient, the ultrasonic intensity at the insulation defect location is obtained, satisfying the following relationship:

[0163] Where V0 represents the ultrasonic intensity at the insulation defect location, x' represents the distance between the insulation defect location and the ultrasonic sensor 1, α represents the attenuation coefficient, and U x' represents the ultrasonic detection intensity, and V represents the speed of sound. 20 is the standard mathematical formula for expressing discharge intensity in decibels (dB) and is a unique value.

[0164] In this application, after obtaining the attenuation coefficient of ultrasonic waves in the current environment, the propagation characteristics of ultrasonic waves can be simulated by COMSOL finite element analysis software, and data fitting can be performed with MATLAB software to indirectly calculate the attenuation coefficient α of ultrasonic waves in different environments (temperature and humidity). An inversion method is established to invert and convert the ultrasonic detection intensity at different distances to the discharge source (insulation defect location), so as to reduce the difference in the evaluation of insulation defect discharge intensity at different detection distances. The ultrasonic wave generated by the insulation defect discharge is generated by point source vibration, and the detection distance is far, so it can be regarded as a spherical wave. During the propagation process, the spherical wave has both dielectric attenuation and diffusion attenuation. The sound pressure attenuation equation can be calculated using the following formula:

[0165] Where: P x' represents the sound pressure at the detection position and the distance x' between the wave source; P0 represents the initial sound pressure when the sound wave contacts the medium; α represents the attenuation coefficient of the medium.

[0166] Once the attenuation coefficient α of the medium is determined, the propagation characteristics of the ultrasonic wave can be obtained. However, the attenuation coefficient α is related to factors such as the medium sound velocity, viscosity, density, specific heat capacity, thermal conductivity and medium particle size at a specific temperature and humidity, and no research has conducted a complete theoretical analysis of it. Therefore, this application uses COMSOL finite element analysis software to simulate the propagation characteristics of ultrasonic waves, and uses MATLAB software for data fitting to indirectly calculate the attenuation coefficient α of ultrasonic waves under different environments (temperature and humidity). Finally, the ultrasonic detection intensity inversion formula is used to calculate the ultrasonic detection intensity dB value V0 at the discharge source:

[0167] When the ultrasonic detection voltage U at the distance x' is obtained x'After determining the detection distance x' and the ultrasonic attenuation coefficient α, the ultrasonic detection intensity V0 at the sound source can be calculated. By inverting the ultrasonic detection intensity at different detection distances back to the sound source, the differences caused by different detection distances are reduced, providing a unified reference for evaluating the discharge intensity of insulation defects.

[0168] In an application scenario, the environmental factors that affect the propagation characteristics of ultrasonic waves are mainly temperature and humidity. In addition, the different frequencies of ultrasonic waves will also affect the propagation characteristics. The center frequencies of the ultrasonic sensor 1 and the conditioning circuit used in the detection device of this application are both 40kHz, so the frequency of the simulated ultrasonic signal is set to 40kHz. Since the temperature and humidity of the actual environment vary greatly, the propagation characteristics of ultrasonic waves under different temperature and humidity combinations are simulated and studied, and the corresponding attenuation coefficient α is calculated using the above formula.

[0169] Since the typical range for defect detection on distribution overhead lines is approximately 6-12 meters, a sphere with a radius of 15 meters was constructed as the simulation geometry. A transient study was conducted using the Ray Acoustics module. The simulation time range was set to 0-40 milliseconds, with a time step of 0.01 milliseconds. The acoustic fluid model was set to atmospheric attenuation. Ultrasonic signals were emitted from a point source with a frequency of 40 kHz and radiated as spherical waves. The source power was set to 1 watt, and the model was accurately solved using conventional meshing within the simulation software. The simulation model's medium was set to air, and the boundary condition was set to "pass through" (i.e., no reflection). The changes in sound pressure at different propagation distances were investigated.

[0170] By setting the ultrasonic propagation distance to 0-12m, with a 1m interval, and adjusting the temperature and humidity, we can determine the sound pressure variations at different propagation distances. Taking a temperature of 25°C and a relative humidity of 60% as an example, we used the MATLAB curve fitting toolbox, cftool, to fit the simulated sound pressure data. The fitting function uses the following formula, which conforms to the sound pressure attenuation formula for spherical wave propagation. The resulting attenuation coefficient, α, is approximately 0.15. The fitting results are shown in Table 1.

[0171] Table 1 Fitting results at different temperatures and relative humidity

[0172] After completing the insulation defect detection, this application also needs to mark the insulation defect on the image to achieve visualization. Marking the insulation defect image can include:

[0173] The insulation defect position is marked in the insulation defect image according to the two-dimensional pixel coordinates of the insulation defect position; the distances between the multiple ultrasonic sensors 1 and the insulation defect position, the multiple electromagnetic wave intensities, and the multiple ultrasonic wave intensities are matched with the marked insulation defect position; and the matched distances between the ultrasonic sensors 1 and the insulation defect position, the electromagnetic wave intensities, and the ultrasonic wave intensities are displayed at the insulation defect position in the insulation defect image.

[0174] As shown in FIG13 , the present application further provides a method for detecting a charged object using the non-contact charged object detection device, comprising:

[0175] The overhead line is inspected by a detection unit, and an image acquisition unit is used to acquire an image of the overhead line in a predetermined direction to obtain an insulation defect image; the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity of the insulation defect position are obtained based on the detection results of the detection unit; and the insulation defect image is marked based on the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity.

[0176] During the actual on-site inspection process, the non-contact live detection device is pointed towards the direction of the overhead line insulator. If there is a defect, an abnormal signal can be detected; if no abnormal signal can be detected, the insulator is normal and there is no defect.

[0177] In actual application, as shown in FIG14 , the distribution overhead line does not need to be powered off, and workers on the ground use detection devices to achieve long-distance, non-contact detection and location of insulation defects in the distribution overhead line insulators and cable transfer terminals.

[0178] The non-contact live-charge detection device and live-charge detection method provided by this application have at least the following effects:

[0179] (1) By configuring the detection unit and processing unit 4, the two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity of the insulation defect location can be obtained based on the detection results. By cooperating with the image acquisition unit 3, the detection unit, and the processing unit 4, the obtained two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity of the insulation defect location can be visualized on the insulation defect image.

[0180] (2) This application realizes the positioning of insulation defects based on the combined acoustic and electrical method and the TDOA algorithm, converting the three-dimensional spatial positioning problem into a two-dimensional positioning problem, thereby improving the positioning accuracy of insulation defects.

[0181] (3) The present application improves the ultrasonic sensitivity of long-distance detection by designing an ultrasonic wave condenser and a high-gain ultrasonic signal conditioning circuit 5 to pre-amplify the ultrasonic signal generated by the insulation defect; and by designing a suitable shape and size of the wave condenser, the ability of the detection device to resist external interference is enhanced.

[0182] (4) The ultrasonic conditioning circuit 5 and the electromagnetic conditioning circuit 6 process the discharge signals of the insulation defects detected by the ultrasonic sensor 1 and the electromagnetic sensor 2, respectively. Since there will be interference signals in the actual detection process, which will affect the detection effect. Therefore, the ultrasonic conditioning circuit 5 and the electromagnetic conditioning circuit 6 of the present application will filter the discharge signals of the insulation defects, filter out the interference signals, and retain the effective abnormal discharge signals. In addition, since the attenuation of the ultrasonic signal is large when it propagates through the air, the ultrasonic conditioning circuit 5 can filter the ultrasonic signal while amplifying it. The electromagnetic signal has a smaller attenuation, so it is filtered by the electromagnetic conditioning circuit 6.

[0183] (5) This application establishes an inversion method for ultrasonic detection intensity, and inverts and converts the ultrasonic detection intensity at different distances to the sound source, thereby reducing the difference in the evaluation of insulation defect discharge intensity at different detection distances.

Claims

1. A non-contact type live detection device, comprising a processing unit (4), and a detection unit and an image acquisition unit (3) both of which are communicatively connected to the processing unit (4); The detection unit comprises an electromagnetic wave sensor (2) and at least three ultrasonic sensors (1); The image acquisition unit (3) is configured to acquire insulation defect images of the overhead line detected by the detection unit; The processing unit (4) is configured to obtain the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity and ultrasonic wave intensity of the insulation defect position according to the detection result of the detection unit, and mark the insulation defect image.

2. The detection device according to claim 1, further comprising an ultrasonic conditioning circuit (5) matching the number of the at least three ultrasonic sensors (1), wherein the ultrasonic conditioning circuit (5) comprises a noise amplification circuit and an amplification filter circuit connected to each other; The input end of the noise amplifying circuit is connected to the ultrasonic sensor (1) and is configured to amplify the signal of the detection result of the ultrasonic sensor (1); the output end of the amplifying and filtering circuit is connected to the processing unit (4) and is configured to amplify and filter the signal output by the noise amplifying circuit.

3. The detection device as described in claim 1 or 2, further comprising an electromagnetic conditioning circuit (6), the input end of the electromagnetic conditioning circuit (6) being connected to the electromagnetic wave sensor (2), the output end of the electromagnetic conditioning circuit (6) being connected to the processing unit (4), and being configured to filter the detection result of the electromagnetic wave sensor (2).

4. The detection device according to claim 1, wherein: The processing unit (4) is configured to mark the insulation defect image in the following manner: Marking the insulation defect position in the insulation defect image according to the two-dimensional pixel coordinates of the insulation defect position; Matching the distances between a plurality of ultrasonic sensors (1) and the insulation defect position, a plurality of electromagnetic wave intensities and a plurality of ultrasonic wave intensities with the marked insulation defect position; The distance between the matched ultrasonic sensor (1) and the insulation defect position, the electromagnetic wave intensity and the ultrasonic wave intensity are displayed at the insulation defect position in the insulation defect picture.

5. The detection device according to claim 1, wherein: The processing unit (4) is configured to obtain the spatial coordinates and the two-dimensional pixel coordinates of the insulation defect position according to the detection result of the detection unit in the following manner: Obtaining the distance between the insulation defect position and each ultrasonic sensor (1) according to the detection results of the electromagnetic wave sensor (2) and the at least three ultrasonic sensors (1); According to the distance between the insulation defect position and each ultrasonic sensor (1), and the distance between adjacent ultrasonic sensors The distance between the devices (1) is used to obtain the spatial coordinates of the insulation defect position; The spatial coordinates of the insulation defect position are transformed into pixel coordinates according to the parameters of the image acquisition unit (3).

6. The detection device according to claim 5, wherein: The processing unit (4) is configured to obtain the distance between the insulation defect position and each ultrasonic sensor (1) according to the detection results of the electromagnetic wave sensor (2) and the at least three ultrasonic sensors (1) in the following manner: Acquiring electromagnetic signals and ultrasonic signals detected by the electromagnetic wave sensor (2) and the at least three ultrasonic sensors (1); Extracting the electromagnetic signal and the ultrasonic signal to obtain corresponding arrival times respectively; Determining a time delay between the electromagnetic signal and the ultrasonic signal based on the discharge characteristics of the insulation defect position and the arrival times of the electromagnetic signal and the ultrasonic signal; Based on the time delay between the electromagnetic signal and the ultrasonic signal, the distance between the insulation defect position and each ultrasonic sensor (1) is obtained.

7. The detection device according to claim 6, wherein: The processing unit (4) is configured to extract the ultrasonic signal to obtain the corresponding arrival time in the following manner: Obtaining average energy of the ultrasonic signal according to the ultrasonic signal detected within the duration; Dividing the duration into a plurality of first preset time periods; Obtaining an ultrasonic signal energy curve according to the average energy of the ultrasonic signal and the energy of the ultrasonic signal in the first preset time period; Filtering out the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve within the first preset time period according to the ultrasonic signal energy curve; Obtaining the arrival time of the ultrasonic signal according to the ultrasonic signal corresponding to the minimum value of the ultrasonic signal energy curve; The processing unit (4) is configured to extract the electromagnetic signal to obtain the corresponding arrival time in the following manner: Obtaining a threshold expansion coefficient for the electromagnetic wave sensor (2) to detect electromagnetic signals according to the signal-to-noise ratio of the current detection environment; Obtaining an electromagnetic detection threshold according to the threshold expansion coefficient and the electromagnetic signal within the duration; dividing the duration into a plurality of second preset time periods; The second preset time period is selected according to the second preset time period and the electromagnetic detection threshold. The electromagnetic signal that reaches the electromagnetic detection threshold for the first time within a period of time; The corresponding arrival time is determined according to the electromagnetic signal that reaches the electromagnetic detection threshold for the first time.

8. The detection device according to claim 6 or 7, wherein: The processing unit (4) is configured to determine the time delay between the electromagnetic signal and the ultrasonic signal based on the discharge characteristics of the insulation defect position and the arrival times of the electromagnetic signal and the ultrasonic signal in the following manner, including: Based on the arrival time of the electromagnetic signal and the ultrasonic signal, the propagation speed of the electromagnetic signal, and the preset minimum resolution of the delay, the correlation accumulation factor is obtained, which satisfies the following relationship: Wherein, Q(t) represents the correlation accumulation factor, a represents the number of ultrasonic signal arrival times, b represents the number of electromagnetic signal arrival times, i" represents the ultrasonic signal sequence number sorted by detection time, j" represents the electromagnetic signal sequence number sorted by detection time, Δt represents the preset minimum delay resolution, v' represents the propagation speed of the electromagnetic signal, T ult,i" represents the i"th arrival time of the ultrasonic signal, T ele,j" represents the j'th arrival time of the electromagnetic signal, and t represents the estimated time delay between the electromagnetic signal and the ultrasonic signal; Obtaining a delay estimation value by calculating a maximum value of the correlation accumulation factor; According to the arrival times of the electromagnetic signal and the ultrasonic signal, and the preset minimum delay resolution, a plurality of delay increase interval ranges are obtained; Based on the multiple delay increase interval ranges, determine the delay increase interval range in which the delay estimate value is located; Determining the arrival time of the corresponding electromagnetic signal and ultrasonic signal according to the determined time delay increase interval range; According to the determined arrival times of the electromagnetic signal and the ultrasonic signal, a time delay between the electromagnetic signal and the ultrasonic signal is obtained.

9. The detection device according to claim 6 or 7, wherein: The processing unit (4) is configured to obtain the ultrasonic intensity at the insulation defect position according to the detection result of the detection unit in the following manner, including: Collect the temperature and humidity of the current environment; Obtaining an attenuation coefficient of ultrasonic waves in the current environment based on the temperature and humidity; According to the obtained arrival time of the ultrasonic signal, the signal amplitude corresponding to different arrival time is obtained; The signal amplitudes corresponding to the different arrival times are screened for the maximum value to obtain the ultrasonic detection intensity. Spend; The ultrasonic intensity at the insulation defect position is obtained according to the distance between the insulation defect position and the ultrasonic sensor (1), the ultrasonic detection intensity and the attenuation coefficient.

10. A method for detecting a charge, applied to the non-contact type charge detection device according to any one of claims 1 to 9, comprising: The overhead line is detected by the detection unit of the detection device, and the image acquisition unit of the detection device is used to acquire an image of the overhead line in a predetermined direction to obtain an insulation defect image; Obtaining the spatial coordinates, two-dimensional pixel coordinates, electromagnetic wave intensity, and ultrasonic wave intensity of the insulation defect position according to the detection results of the detection unit; The insulation defect image is marked according to the spatial coordinates, the two-dimensional pixel coordinates, the electromagnetic wave intensity and the ultrasonic wave intensity.

Images