CN111830381B - Watchband-adjustable full-attached cable partial discharge ultrasonic sensor and online monitoring method - Google Patents

Abstract

The invention relates to a watchband adjustable full-fitting cable partial discharge ultrasonic sensor, which belongs to the field of on-line monitoring and intelligent diagnosis of power equipment, and comprises a thin metal sheet lining and a rubber watchband, wherein a watchband buckle head is arranged at the end part of the rubber watchband, a grounding metal sealing box is arranged in the middle of the rubber watchband, and grounding polar plates are arranged on the upper surface and the lower surface of the grounding metal sealing box; an ultrasonic signal sensing system, a signal acquisition and processing system, a data analysis and storage system, a device self measurement and control system, a communication system and a power supply system are arranged in the grounding metal sealing box. The size of the watchband can be adjusted according to the size of the power cable, and the watchband is installed and fastened, so that the thin metal sheet is tightly attached to the outer surface of the cable to be tested, the loss of ultrasonic signals during transmission is reduced, and the reliability and the accuracy of measurement data are ensured; the invention can be widely applied to the on-line monitoring scene of the partial discharge of the power cable, in particular to a watchband type design structure, is convenient to install and is suitable for power cables of various types.

Description

An adjustable full-fit cable partial discharge ultrasonic sensor with watch strap and online monitoring method

technical field

The invention belongs to the field of on-line monitoring and intelligent diagnosis of electric power equipment, and relates to an adjustable strap full-fit cable partial discharge ultrasonic sensor and an on-line monitoring method.

Background technique

In the power system, high-voltage and extra-high-voltage power cables will have partial discharges at the cable insulation defects during operation, and partial discharges will further cause insulation degradation of the power cables, and in severe cases will cause damage to the cables, which will lead to large areas. Accidents caused by power outages occur. Therefore, detection of cable partial discharge is one of the important measures to reduce cable failures. Partial discharge inside the cable will generate ultrasonic waves, and the ultrasonic waves will propagate to the on-line monitoring device on the cable surface. When the ultrasonic wave propagates in the device, it will cause slight deformation on the surface of the device, which will generate mechanical stress on the PVDF piezoelectric film attached to the surface of the device, and convert it into a charge signal. The charge signal passes through the charge amplifier, trap circuit and voltage amplifier circuit. function, and then sent to the computer to analyze and process the signal, so as to evaluate the degree of cable degradation.

According to the nature of ultrasonic waves, the attenuation in the gas medium is very serious when it propagates, and the attenuation is weak in metal and liquid media, and even the attenuation can be ignored when propagating in short-distance metal media. Therefore, when receiving ultrasonic signals, use It is very important to remove the air between the cable and the metal medium and remove the air between the cable and the metal. The surface of the cable is a circular arc, while the surface of most ultrasonic sensors is flat, so it is difficult to fit well with the surface of the cable, and the ultrasonic signal cannot be received in the most effective way. Usually, when receiving ultrasonic signals, the ultrasonic sensor is exposed in the air and is easily interfered by other signals in the external environment. Therefore, it is very important to get a more accurate result by eliminating the influence of external interference signals when receiving ultrasonic signals.

Contents of the invention

In view of this, the purpose of the present invention is to propose an ultrasonic on-line monitoring method based on partial discharge of cables, aiming at the problems that the existing ultrasonic on-line monitoring method is easily interfered by external environmental signals, resulting in weak ultrasonic signals being covered up and inaccurate monitoring results. Device and structure optimization method. The present invention uses a metal box to package the ultrasonic sensor, trap circuit, amplifier circuit, power supply module and A/D conversion module, and smears the metal box with a material that reflects and absorbs sound waves to eliminate the interference of the external environment. At the same time, a thin-film ultrasonic sensor is attached to the metal outer circle, and there is an ultrasonic coupling layer between the metal outer circle and the sensor to enhance the ultrasonic signal. The purpose of the present invention is to improve the anti-interference ability of the online monitoring device, eliminate external interference and maximize the reception of ultrasonic signals, thereby improving the accuracy and precision of the ultrasonic sensor.

The principle of the present invention is: the device of the present invention mainly realizes signal reception and information acquisition based on ultrasonic sensing. The device is mainly composed of signal receiving, signal processing modules and device accessories. Among them, the modular ultrasonic sensor is the core structure of the device, which mainly consists of two parts: an ultrasonic signal acquisition structure and a signal conversion structure. The ultrasonic signal acquisition structure is composed of PVDF polyvinylidene fluoride piezoelectric film sensor. PVDF polyvinylidene fluoride piezoelectric film has the following advantages: high piezoelectric voltage constant, high sensitivity when used as a sensor; small density, light weight, When pasted on the surface of the object, it has little effect on the original structure; the dielectric constant is high, and it can withstand the action of a strong electric field; it has good flexibility and processing performance, and can be made into films with different thicknesses and shapes according to needs; wide frequency response, can be used in The response ranges from 10 ^-5 to 10 ⁹ ; at the same time, its chemical stability and fatigue resistance are high, and it has good thermal stability. Based on the above advantages, the present invention uses a PVDF polyvinylidene fluoride piezoelectric film sensor as a sensor for receiving ultrasonic signals. The PVDF piezoelectric film sensor transmits ultrasonic information through the deformation of its surface when the ultrasonic wave passes through the device and the degree of force and strain on the film. When the applied electric field is zero, the piezoelectric equation of the PVDF piezoelectric film is:

D _i = d _ij T _j (1)

In the formula: D _i is electric displacement; d _ij is piezoelectric constant; T _j is stress (i=1,2,3; j=1,2,3,···,6).

The output charge of the PVDF piezoelectric film is the response of the strain in all directions acting on the polarization direction, that is:

Q＝∑d _ij Eε _j S (2)

In the formula: Q is the output charge; E is the elastic modulus of the PVDF piezoelectric film; _εj is the strain (j=1,2,3); S is the area covered by the PVDF piezoelectric film.

When the PVDF piezoelectric film is under one-dimensional force, the output charge can be expressed as:

Q＝d ₃₁ Eε ₁ S (3)

When the PVDF piezoelectric film is used for the sensing function, it is a charge generator, and the charge generated by it must be converted into a voltage signal through a signal conversion structure before subsequent processing. The signal conversion structure is the charge amplifier, which is actually a high-gain operational amplifier with deep capacitive negative feedback. The charge signal becomes a voltage signal after passing through the signal conversion structure, and the voltage signal can be obtained as:

Where: C _f is the feedback capacitance of the charge amplifier.

Therefore, the voltage output of the charge amplifier has a linear relationship with the strain of the measured structure. At the same time, the larger the area covered by the piezoelectric sensor on the cable, the larger its voltage and the easier it is to measure.

Since the PVDF piezoelectric film itself is susceptible to electromagnetic interference, the 50Hz power frequency interference is the most obvious, and the existence of power frequency interference is likely to cause signal distortion. Therefore, a notch circuit is used to eliminate the influence of power frequency interference. T band-stop filter circuit is realized. After the charge signal output by the PVDF piezoelectric film is processed by the charge amplifier and the trap circuit, the voltage detection signal is obtained through the voltage amplifier circuit.

At the same time, the optimized structure of the present invention encapsulates all components susceptible to interference in a metal box, and the metal box is grounded to shield external electromagnetic interference, forming a relatively independent space inside, and coating the surface of the metal box with an absorbing Materials that reflect sound waves further enhance the anti-interference level of the device.

To achieve the above object, the present invention provides the following technical solutions:

On the one hand, there is provided an adjustable full-fit cable partial discharge ultrasonic sensor with a watch strap, which includes a thin metal sheet lining and a rubber watch strap, and the rubber watch strap covers the metal sheet inner lining, and at the end of the rubber watch strap There is a watch strap buckle on the top, and the other end of the rubber strap passes through the strap buckle and can be locked by the watch strap buckle;

The middle part of the rubber strap is provided with a grounded metal sealed box, the outer surface of the grounded metal sealed box is covered with a layer of paint that absorbs and reflects electromagnetic waves, and the upper and lower surfaces of the grounded metal sealed box are provided with grounding plates;

The grounded metal sealed box is equipped with an ultrasonic signal sensing system, a signal acquisition and processing system, a data analysis and storage system, a device's own measurement and control system, a communication system, and a power supply system;

The ultrasonic signal sensing system is used to collect cable ultrasonic waves and convert them into voltage signals; the signal acquisition and processing system is used to receive voltage signals and perform filter amplification and time-frequency conversion processing; the data analysis and storage system is used for The received data is analyzed to obtain the fluctuation characteristics of the ultrasonic signal and the operating conditions of the cable, and the data is stored; the measurement and control system of the device itself is used for abnormal situation detection and alarm, and is also used for man-machine communication regulation; the communication system is used for Communicate with the host computer; the power supply system is used to supply power to each module.

Further, the ultrasonic signal sensing system includes a PVDF piezoelectric film sensor and a charge amplifier, the PVDF piezoelectric film surface of the PVDF piezoelectric film sensor is also provided with a protective film, and also includes a charge amplifier for converting the generated charge signal converted to a voltage signal.

Further, the signal acquisition and processing system includes a notch circuit, a voltage amplification circuit, a voltage conversion circuit, an A/D converter and a signal reading module, and the notch circuit eliminates power frequency interference on the voltage signal, and then The voltage detection signal is obtained through the voltage amplification circuit, and then the actual voltage amplitude is converted to the effective range of the signal collector through the voltage conversion circuit, and the voltage signal acquisition and storage is realized by using the A/D converter and the signal reading module.

Further, the data analysis and storage system includes a high-frequency programmable processor core with FPU, which is equipped with parameter feature recognition, time-domain correlation calculation, and state evaluation algorithms for mining ultrasonic signal fluctuation characteristics and cable operating conditions. Synchronously collect ultrasonic signal data of cable partial discharge, provide real-time reference information for cable working condition identification, operation and maintenance and protection; also expand memory through external expansion SDRAM, expand local data storage capacity through external expansion NAND-FLASH To meet the storage of local long-term original data, secondary data and identification results.

Further, the device's own measurement and control system includes a device abnormal alarm system and a man-machine communication control system; the device abnormal alarm system includes a digital distributed temperature sensor for measuring the multi-point temperature inside the device, and is used for the transmission of multi-point temperature information. 1. The collected IIC gating chip judges and alarms abnormal temperature; the abnormal alarm system of the device also includes an abnormal power supply alarm system, which uses a real-time voltage acquisition circuit to collect port signal voltage, and inputs it into the comparison circuit with the set threshold Voltage comparison, when the output voltage is lower than the threshold voltage, it will trigger the abnormal voltage alarm circuit;

The man-machine communication control system includes a display screen, control buttons and indicator lights for man-machine interaction.

Further, the communication system includes a standard optical fiber interface, an Ethernet interface, an RS232/485 interface, and a back-end connection line, and uses the DMA mode of the central processing unit to directly transmit the information in the storage unit to the communication port, matching the IEC61850 protocol in the station, and realizing communication with Information uploading, real-time information calling, and remote control functions between IDE devices and communication servers in the station.

Further, the power supply system includes an external power supply system, an uninterruptible power supply system, a voltage stabilization system, and a digital-to-analog isolation system; the external power supply system includes a sequentially connected AC and DC power interface, a rectifier circuit, an inverter frequency conversion circuit, a filter circuit, multi-stage voltage divider circuit; the uninterruptible power supply system includes a storage battery pack, which is used to ensure the continuous supply of electric energy in abnormal situations; the voltage stabilization system includes a voltage protection circuit to avoid damage to the device under the action of a large voltage; the digital-analog The isolation system is used to realize the isolation of digital power supply and analog power supply to avoid mutual interference between signals.

Furthermore, this device can realize the measurement of the transient value of the cable ultrasonic signal, the local data storage period is 72h, and the extended storage depth is 128G; the standard 220V/50Hz AC source or the 15V constant DC source can supply power for the device.

Further, the fixing device is an elastic strap. The watch strap is inlaid with a metal sheet lining structure and a rubber exterior structure. The metal lining structure is tightly fitted together with a thin metal sheet and a rubber exterior. Its size can be adjusted according to the size of the cable. When installing, it can be Loosen the watch strap, install and fix the monitoring device on the cable to be tested, and then tighten the watch strap, so that the thin metal lining and the cable to be tested are tightly attached together, so as to reduce the ultrasonic signal during the propagation process. loss.

On the other hand, this aspect provides an online monitoring method, based on the above-mentioned strap-adjustable full-fit cable partial discharge ultrasonic sensor, comprising the following steps:

(1) Initialization

After the watchband adjustable full-fitting cable partial discharge ultrasonic sensor is powered on, the system enters the initialization setting according to the preset settings, starts its own measurement and control system to detect the power system and operating conditions, and enters the ultrasonic signal acquisition and measurement after passing the self-inspection state;

(2) Regular signal collection and processing

Entering the cycle of signal acquisition and data analysis, first collect the ultrasonic signal, and use the charge amplifier to convert the charge signal output by the film sensor into a voltage signal, and input it to the filter circuit and amplification circuit for processing, and then transmit the signal to the A/D for high-speed acquisition The high-frequency central processor is used for digital filtering, and the processed data is stored in the local memory according to the date and feature type for subsequent processing;

(3) Data analysis and working condition identification

Call and analyze the stored data, obtain ultrasonic features based on ultrasonic signal feature recognition, state evaluation and other algorithms, including amplitude, frequency and rate of change, and compare such feature quantities with historical data, or mine out based on intelligent algorithms The partial discharge of the cable is used to fully identify the current operating conditions of the cable, and early detection of internal overheating and excessive instantaneous overvoltage faults in the cable; when the fault or abnormal operating condition is identified, the early warning system is activated and the communication function is activated at the same time. Send abnormal instructions to the station-level server to realize accurate early warning of cable abnormal conditions; when there is no fault and the station-level server regularly or specifies the command to issue information call, the communication interface accepts the call command and starts the data call in the central processing unit. Commands are issued, and the required data sets are called out from the memory for packet processing and transmission, so as to realize the uploading of historical monitoring data, during which the sampler continues to perform real-time data sampling;

(4) end

When the reset period of the device is reached, the device will start refreshing as a whole, vacate the memory and body storage, and enter step (1); when receiving the shutdown command from the station control terminal or the near-ground terminal is closed, the device will interrupt the operation and enter the shutdown state.

The beneficial effects of the present invention are:

1. The present invention is the first to design an adjustable watch strap full-fitting cable partial discharge ultrasonic sensor. The size of the designed device strap can be adjusted according to the size of the power cable. The strap-type installation and fastening can make the thin metal sheet and The outer surface of the cable to be tested is tightly bonded, which reduces the loss of the ultrasonic signal during propagation and ensures the reliability and accuracy of the measurement data;

2. The electromagnetic shielding structure formed by applying electromagnetic absorption and reflection materials on the surface of the metal box proposed by the present invention and grounding can enhance the resistance of the internal measurement and control devices to external interference signals, so that the device can be used in various harsh environments;

3. The power cable ultrasonic signal synchronous sensing system proposed by the present invention has functions such as intelligent data processing, remote communication, and automatic regulation, which can realize local processing and analysis of raw data, rely on hardware programs to complete information mining, and utilize The remote communication module and the station control layer server realize data transmission, and the developed automatic control function can realize the diagnosis and control of the device's own operating status, and avoid the problem of unreliable monitoring caused by the unreliable device itself;

4. The device and system of the present invention are easy to use, and the method of the present invention is simple to operate.

The invention can be widely used in the scene of on-line monitoring of partial discharge of power cables, especially the strap design structure, which is convenient for installation and is suitable for various types of power cables.

Other advantages, objects and features of the present invention will be set forth in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the investigation and research below, or can be obtained from It is taught in the practice of the present invention. The objects and other advantages of the invention may be realized and attained by the following specification.

Description of drawings

In order to make the purpose of the present invention, technical solutions and advantages clearer, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is the three-dimensional and plane structural representation of device of the present invention;

Fig. 2 is a schematic diagram of device data acquisition of the present invention;

Fig. 3 is the package schematic diagram of the device metal box of the present invention;

Fig. 4 is the functional block diagram of device of the present invention;

Fig. 5 is the structural block diagram of the power supply system of the device of the present invention;

Fig. 6 is a flowchart of the device of the present invention.

Reference signs: 1—thin metal sheet lining; 2—rubber watch strap; 3—watch strap buckle head; 4—grounded metal sealing box; 5—sealing ear cap; 6—PVDF piezoelectric film sensor; 7—charge transmission line ;8—charge amplifier; 9—voltage signal acquisition line; 10—voltage acquisition system; 11—data analysis hardware module; 12—storage module; 13—communication system; 14—power supply system; 15—battery; 16—external AC power supply Supply system; 17—the upper plate of the metal box; 18—the lower plate of the metal box; 19—the grounding circuit of the metal box; 20—anti-interference coating.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments are only schematically illustrating the basic concept of the present invention, and the following embodiments and the features in the embodiments can be combined with each other in the case of no conflict.

Wherein, the accompanying drawings are for illustrative purposes only, and represent only schematic diagrams, rather than physical drawings, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, Enlargement or reduction does not represent the size of the actual product; for those skilled in the art, it is understandable that certain known structures and their descriptions in the drawings may be omitted.

In the drawings of the embodiments of the present invention, the same or similar symbols correspond to the same or similar components; , "front", "rear" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred devices or elements must It has a specific orientation, is constructed and operated in a specific orientation, so the terms describing the positional relationship in the drawings are for illustrative purposes only, and should not be construed as limiting the present invention. For those of ordinary skill in the art, the understanding of the specific meaning of the above terms.

As shown in Figure 1-5, an adjustable wristband full-fit cable partial discharge ultrasonic sensor mainly includes a wristband device structure, an ultrasonic signal sensing structure, a signal acquisition and processing system, a data analysis and storage system, and a device Its own measurement and control system, communication system and power supply system are characterized in that:

The strap-type device structure is composed of a strap and a closed metal box. The strap is inlaid with a thin metal lining 1 and a rubber strap 2. The size of the strap can be adjusted according to the size of the cable. The fastening of the buckle head 3 can ensure that the thin metal sheet and the cable to be tested are tightly attached to the cable body or joint of different sizes; due to the strong propagation of ultrasonic waves in metal, the full-fit structure meets the requirements of ultrasonic waves during measurement. The signal is directly transmitted to the thin metal sheet through the couplant on the surface of the cable with low loss, and then quickly transmitted to the sensor through the ring-shaped thin metal sheet, which greatly reduces the loss of the ultrasonic signal during the propagation process and realizes partial discharge ultrasonic sensing at all angles; A grounded metal sealing box 4 is installed in the center of the strap. The sealing box is entirely made of metal. During installation, the metal box is closed and fastened with screws. The metal box is equipped with a sealing ear cap for better sealing. The outer surface of the metal box is coated with a layer of coating that can absorb and reflect electromagnetic waves, that is, the anti-interference coating 20, and also includes the metal box grounding circuit 19, which is used to ground the metal box. At the same time, the upper and lower surfaces are equipped with grounding plates. The upper plate 17 of the metal box and the lower plate 18 of the metal box make the metal shell present zero potential, thereby constructing an independent space of electromagnetic shielding between the inside of the metal box and the external environment, and reducing the influence of external interference signals on the inside.

The ultrasonic signal sensing system mainly includes a PVDF piezoelectric film sensor 6 and a charge amplifier 8 connected through a charge transmission line 7 . In order to avoid damaging and polluting the PVDF piezoelectric film during use, a protective film is added on the surface of the PVDF piezoelectric film; secondly, since the PVDF piezoelectric film is a polymer material, the electrodes cannot be directly welded, but riveted on the PVDF piezoelectric film. The electrodes are drawn out from the electric film. When the ultrasonic wave propagates in the device, it will cause slight deformation on the surface of the device, which will generate mechanical stress on the PVDF piezoelectric film attached to the surface of the device, and convert it into a charge signal. The charge signal is converted into a voltage signal by the charge amplifier, and the voltage signal is transmitted again. to the signal acquisition and processing module for processing.

The signal acquisition and processing system 10 includes a voltage signal acquisition line 9, signal filtering, signal amplification and signal time-frequency conversion. In order to avoid the ultrasonic signal from electromagnetic interference, a notch circuit is designed to eliminate the influence of power frequency interference. The notch circuit is realized by a double-T band-stop filter circuit. The charge signal output by the PVDF piezoelectric film is processed by the charge amplifier and the trap circuit, and then the voltage detection signal is obtained through the voltage amplifier circuit. At the same time, a voltage conversion circuit is designed to convert the actual voltage amplitude to the effective range of the signal collector, and The high-resolution A/D converter and high-speed signal reading module are used to realize the acquisition and storage of voltage signals. After acquisition, they are directly transmitted to the central controller to realize data inspection and transmission.

The data analysis and storage system mainly includes a data analysis hardware module 11, a storage module 12, and a data processing algorithm. Among them, ① data analysis hardware module 11 has a high-frequency programmable processor core of FPU, which can realize high-precision, high-speed floating-point processing, and builds a multi-data processing unit by programming and program burning, and can support multiple Type communication interface; ② Use externally expanded SDRAM12 to expand memory, increase processor computing capacity, and meet the needs of complex data processing algorithms; select large-capacity, long-cycle, industrial-grade externally expanded NAND-FLASH to expand local data storage capacity to meet Local long-period raw data, secondary data, and identification results are stored to provide a target database for later remote calls; ③Data processing algorithms include parameter feature identification, time-domain correlation calculation, and state evaluation algorithms to fully mine out Ultrasonic signal fluctuation characteristics, cable operating conditions and other information realize the synchronous collection of ultrasonic signal data of cable partial discharge, and provide real-time reference information for the identification, operation and maintenance and protection of cable working conditions.

The device's own measurement and control system mainly includes a device abnormality alarm system and a man-machine communication control system. Among them, ①In the actual operation situation, in order to prevent the external fire source from causing serious damage to the monitoring device, the high temperature early warning system of the device is designed. Use the digital distributed temperature sensor to measure the multi-point temperature inside the device, and use the high-speed IIC gating chip to realize the transmission and collection of multi-point temperature information, realize the judgment of abnormal temperature based on the internal temperature early warning method, and control the early warning of high temperature abnormality The circuit realizes the characterization of temperature abnormal state; ②In actual operation, due to insufficient energy of the independent power supply or failure of the power supply circuit, the output voltage signal will be unstable and the detection signal will be inaccurate. In this regard, a real-time voltage acquisition with low energy consumption, a comparison circuit and an abnormal power supply alarm system for the early warning system are proposed. The real-time voltage acquisition circuit is used to collect the port signal voltage, and input to the comparison circuit for comparison with the set threshold voltage. When the output voltage When the voltage is lower than the threshold value, the abnormal voltage alarm circuit will be triggered; ③The man-machine communication system includes a liquid crystal display, indicator lights and buttons. Commands are sent to the measurement and control system to complete the selection of corresponding functions and equipment debugging, and the measurement and control system sends the device's working conditions and parameter information to the liquid crystal display to realize man-machine communication.

The communication system 13 includes the standard optical fiber interface of the device, the Ethernet interface, the RS232/485 interface, the connecting wire at the back end, etc., and uses the DMA mode of the central processing unit to directly transmit the information in the storage unit to the communication port, matching the internal The IEC61850 protocol realizes the functions of information upload, real-time information call, remote control and other functions between the device and the IDE equipment in the station and the communication server in the station.

The power supply system 14 includes an uninterruptible power supply system, which in this embodiment is a storage battery 15, an external power supply system 16, a voltage stabilizing system, and a digital-analog isolation system. Among them, AC and DC power interfaces are provided, which can meet the AC or DC power supply of devices under different backgrounds. The rectification circuit, inverter frequency conversion circuit, voltage stabilization circuit, filter circuit, and multi-stage voltage divider circuit are designed to achieve ±5V and ±3V. The stable output of digital and analog power supply voltage and 200Hz AC voltage, and built a voltage protection circuit to avoid damage to the device under the action of high voltage; and designed an uninterruptible power supply system for the device using batteries and voltage stabilizing circuits to meet the poor quality of external power supply or The power supply of the device is continuous under fault conditions; a large ground plane and a digital-analog isolation circuit are designed to realize the isolation of digital power and analog power, which can avoid mutual interference between signals and ensure the signal integrity of the monitoring system.

Furthermore, this device can realize the measurement of the transient value of the cable ultrasonic signal, the local data storage period is 72h, and the extended storage depth is 128G; the standard 220V/50Hz AC source or the 15V constant DC source can supply power for the device.

Further, the fixing device is an elastic strap. The watch strap is inlaid with a metal sheet lining structure and a rubber exterior structure. The metal lining structure is tightly fitted together with a thin metal sheet and a rubber exterior. Its size can be adjusted according to the size of the cable. When installing, it can be Loosen the watch strap, install and fix the monitoring device on the cable to be tested, and then tighten the watch strap, so that the thin metal lining and the cable to be tested are tightly attached together, so as to reduce the ultrasonic signal during the propagation process. loss.

As shown in Fig. 6, the present invention also provides a kind of monitoring method, utilizes above-mentioned device, carry out the measurement of cable partial discharge ultrasonic wave programmatically, it is characterized in that specific method steps are as follows:

(1) Initialization

After the above-mentioned device is powered on, the device system enters the initialization setting according to the preset setting, and the device starts its own measurement and control system to detect the power system 14 and the operating conditions, and enters the ultrasonic signal acquisition and measurement state after passing the self-test;

(2) Regular signal collection and processing

After step (1) is completed, enter the signal acquisition and data analysis cycle, first collect the ultrasonic signal, and use the charge amplifier (7) to convert the charge signal output by the film sensor into a voltage signal, and input it to the filter circuit and amplifier circuit for processing , then the signal is transmitted to the A/D high-speed collector, and the high-frequency central processing unit 11 is used to perform digital filtering, and the processed data is stored in the local memory 12 according to the date and feature type to wait for subsequent processing;

(3) Data analysis and working condition identification

After step (2) is completed, the stored data is called and analyzed, and ultrasonic features are obtained based on algorithms such as ultrasonic signal feature recognition and state evaluation, including amplitude, frequency, and rate of change, etc. Compare the data, or dig out the partial discharge of the cable based on the intelligent algorithm, so as to fully identify the current operating conditions of the cable, and detect faults such as internal overheating and excessive instantaneous overvoltage in the cable in advance. When faults or abnormal operating conditions are identified, the device will activate the early warning system and at the same time start the communication function 13 to send abnormal instructions to the station-level server to realize accurate early warning of cable abnormal conditions; when there is no fault, the station-level server regularly Or when specifying a command to issue information call, the communication interface accepts the call command, and starts the data call command in the central processing unit 11, and calls the required data set from the memory 12 for subpackage processing and transmission, thereby realizing historical monitoring data upload, during which the sampler continues to sample real-time data;

(4) end

After steps (1)(2)(3) are completed, when the reset cycle of the device is reached, the device will start to refresh as a whole, empty the internal memory and the storage of the body, and enter step (1); When the ground terminal is closed, the device will interrupt the operation and enter the closed state.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should be included in the scope of the claims of the present invention.

Claims (3)

1. An adjustable full-fit cable partial discharge ultrasonic sensor with watch strap, characterized in that: it includes a thin metal sheet lining and a rubber watch strap, and the rubber watch strap covers the metal sheet inner lining, and on the rubber watch strap The end of the strap is provided with a strap buckle, and the other end of the rubber strap passes through the strap buckle and can be locked by the strap buckle; the size of the rubber strap can be adjusted according to the size of the cable , Loosen the watch strap during installation, install and fix it on the cable to be tested, and then tighten the watch strap, so that the thin metal sheet lining and the cable to be tested are bonded together to reduce the loss of ultrasonic signals during the propagation process; The middle part of the rubber strap is provided with a grounded metal sealed box, the outer surface of the grounded metal sealed box is covered with a layer of paint that absorbs and reflects electromagnetic waves, and the upper and lower surfaces of the grounded metal sealed box are provided with grounding plates; The grounded metal sealed box is equipped with an ultrasonic signal sensing system, a signal acquisition and processing system, a data analysis and storage system, a device's own measurement and control system, a communication system, and a power supply system; The ultrasonic signal sensing system is used to collect cable ultrasonic waves and convert them into voltage signals; the signal acquisition and processing system is used to receive voltage signals and perform filter amplification and time-frequency conversion processing; the data analysis and storage system is used for The received data is analyzed to obtain the fluctuation characteristics of the ultrasonic signal and the operating conditions of the cable, and the data is stored; the measurement and control system of the device itself is used for abnormal situation detection and alarm, and is also used for man-machine communication regulation; the communication system is used for Communicating with the host computer; the power supply system is used to supply power to each module; The ultrasonic signal sensing system includes a PVDF piezoelectric film sensor and a charge amplifier, the PVDF piezoelectric film surface of the PVDF piezoelectric film sensor is also provided with a protective film, and also includes a charge amplifier for converting the generated charge signal into voltage signal; The signal acquisition and processing system includes a notch circuit, a voltage amplifying circuit, a voltage conversion circuit, an A/D converter and a signal reading module, the notch circuit eliminates power frequency interference on the voltage signal, and then passes the voltage The amplifying circuit obtains the voltage detection signal, and then converts the actual voltage amplitude to the effective range of the signal collector through the voltage conversion circuit, and uses the A/D converter and the signal reading module to realize the voltage signal acquisition and storage; The data analysis and storage system includes a high-frequency programmable processor core with FPU, equipped with parameter feature recognition, time-domain correlation calculation, and state evaluation algorithms, used to mine ultrasonic signal fluctuation characteristics, cable operating conditions, and cable The ultrasonic signal data of partial discharge is collected synchronously to provide real-time reference information for the identification, operation and maintenance and protection of cables; the memory is also expanded through externally expanded SDRAM, and the local data storage capacity is expanded through externally expanded NAND-FLASH. Meet the storage of local long-term original data, secondary data and identification result data; The device's own measurement and control system includes a device abnormal alarm system and a man-machine communication control system; the device abnormal alarm system includes a digital distributed temperature sensor that measures the temperature of multiple points inside the device, and is used for the transmission and collection of multi-point temperature information. The IIC strobe chip is used to judge and alarm the abnormal temperature; the abnormal alarm system of the device also includes an abnormal power supply alarm system, which uses a real-time voltage acquisition circuit to collect the port signal voltage, and inputs it into the comparison circuit to compare with the set threshold voltage. Comparison, when the output voltage is lower than the threshold voltage, it will trigger the abnormal voltage alarm circuit; The man-machine communication control system includes a display screen, control buttons and indicator lights for man-machine interaction; The communication system includes a standard optical fiber interface, an Ethernet interface, an RS232/485 interface, and a back-end connection line, and uses the DMA mode of the central processor to directly transmit the information in the storage unit to the communication port, matching the IEC61850 protocol in the station, and realizing the integration with the IDE in the station. Information uploading, real-time information calling, and remote control functions between equipment and communication servers in the station; The power supply system includes an external power supply system, an uninterruptible power supply system, a voltage stabilization system and a digital-analog isolation system; the external power supply system includes an AC-DC power interface, a rectifier circuit, an inverter frequency conversion circuit, a filter circuit, multi-stage voltage divider circuit; the uninterruptible power supply system includes a storage battery pack, which is used to ensure the continuous supply of electric energy in abnormal situations; the voltage stabilization system includes a voltage protection circuit to avoid damage to the device under the action of a large voltage; the digital-analog isolation system It is used to realize the isolation of digital power supply and analog power supply to avoid mutual interference between signals. 2. The strap-adjustable full-fit cable partial discharge ultrasonic sensor according to claim 1, characterized in that: the measurement of the transient value of the cable ultrasonic signal is realized, the local data storage period is 72h, and the depth of extended storage is 128G; A standard 220V/50Hz AC source or a 15V constant DC source can power the unit. 3. An online monitoring method based on an adjustable full-fit cable partial discharge ultrasonic sensor according to any one of claims 1-2, comprising the following steps: (1) Initialization Loosen the strap of the fully fitted cable partial discharge ultrasonic sensor with an adjustable strap, install and fix it on the cable to be tested, and then tighten the strap so that the thin metal sheet lining fits the cable to be tested together, After the watchband adjustable full-fitting cable partial discharge ultrasonic sensor is powered on, the system enters the initialization setting according to the preset settings, starts its own measurement and control system to detect the power system and operating conditions, and enters the ultrasonic signal acquisition and measurement after passing the self-inspection state; (2) Regular signal collection and processing Entering the cycle of signal acquisition and data analysis, first collect the ultrasonic signal, and use the charge amplifier to convert the charge signal output by the film sensor into a voltage signal, and input it to the filter circuit and amplification circuit for processing, and then transmit the signal to the A/D for high-speed acquisition The high-frequency central processor is used for digital filtering, and the processed data is stored in the local memory according to the date and feature type for subsequent processing; (3) Data analysis and working condition identification Call and analyze the stored data, obtain ultrasonic features based on parameter feature recognition algorithm, time domain correlation calculation algorithm and state evaluation algorithm, including amplitude, frequency and rate of change, and compare such feature quantities with historical data, Or dig out the partial discharge of the cable based on an intelligent algorithm to fully identify the current operating conditions of the cable, and discover the faults of overheating and excessive instantaneous overvoltage inside the cable in advance; when the fault or abnormal operating condition is identified, the early warning system is activated , start the communication function at the same time, send abnormal instructions to the station-level server, and realize accurate early warning of cable abnormal conditions; The data call-out command in the central processor calls out the required data set from the memory for sub-packet processing and transmission, so as to realize the upload of historical monitoring data, during which the sampler continues to perform real-time data sampling; (4) end When the reset period of the device is reached, the device will start refreshing as a whole, empty the memory and body storage, and enter step (1); When the shutdown command from the station control terminal is received or the near-ground terminal is closed, the device will stop running and enter the shutdown state.