Partial discharge signal detection system and method based on optical fiber acoustic emission sensor

Abstract

The present invention discloses a partial discharge signal detection system based on an optical fiber acoustic emission sensor, comprising a laser light source, a coupled optical fiber acoustic emission sensor, a photodetector, an I / U converter, a conditioning circuit I, a conditioning circuit II for signal conditioning, a low-speed ADC acquisition circuit, a high-speed ADC acquisition circuit, and an FPGA control circuit module. The laser light source is connected to the coupled optical fiber acoustic emission sensor, the two output paths of the coupled optical fiber acoustic emission sensor are connected to the photodetector, the photodetector is connected to the I / U converter, the I / U converter is connected to the conditioning circuit I and conditioning circuit II, the conditioning circuit I is connected to the low-speed ADC acquisition circuit, and the conditioning circuit II is connected to the high-speed ADC acquisition circuit. The present invention has the characteristics of low cost, strong anti-interference ability, and the ability to record acoustic emission signals over a wide intensity range.

Description

Technical Field

[0001] The present invention belongs to the field of automated detection, and in particular relates to a partial discharge signal detection system and method based on an optical fiber acoustic emission sensor. Background Art

[0002] Primary power equipment failures can be categorized as mechanical, conductor, and insulation failures, with insulation-related failures accounting for the largest proportion. Partial discharge detection is considered an effective testing method in the International Electrotechnical Commission (IEC) standards for primary equipment insulation testing. Acoustic emission (AE) can detect the occurrence and intensity of PD by detecting transient elastic waves released during PD, enabling instantaneous detection of insulation failures in primary equipment. Coupled fiber optic sensors offer advantages such as small size, electrical insulation, corrosion resistance, electromagnetic interference resistance, and minimal impact on the test environment. For equipment with complex internal structures, such as high-voltage transformers, these fiber optic sensors can be attached to the power equipment casing or fixed inside to perform dynamic nondestructive testing of PD. Acoustic emission signal detection methods based on fiber optic sensors can assess the potential for insulation damage and aging in operating equipment within the power grid, enabling maintenance before significant equipment damage occurs, reducing the likelihood of major disasters and minimizing economic losses.

[0003] CN202372611U discloses a fiber optic acoustic emission sensor and an online monitoring system for transformer partial discharge and positioning. It proposes an online monitoring and positioning system for partial discharge within a transformer based on an over-coupled fiber optic sensor with a fused taper. The patent mentions a method for detecting partial discharge in power transformers with low acoustic emission detection efficiency, capable of detecting only acoustic signals within a certain intensity range. Therefore, it is difficult to detect acoustic emission signals at defect locations far from the sensor, and it is also difficult to fully record discharge signals of varying intensities throughout the entire process of insulation aging and breakdown.

[0004] CN201269916Y discloses a gas-insulated combination electrical appliance partial discharge detection system, proposing a gas-insulated combination electrical appliance (GIS) partial discharge detection system. This system uses a comprehensive detection system that combines ultra-high frequency detection with acoustic emission detection to monitor, locate, and process data for partial discharge within the GIS. The patent's method for performing acoustic emission re-detection within a fixed area after initial detection of ultra-high frequency characteristic data is relatively complex. Furthermore, the acoustic emission detection has low sensitivity, limiting signal detection to a relatively small, set area. Furthermore, the piezoelectric sensor is susceptible to electromagnetic interference, affecting detection accuracy. Summary of the Invention

[0005] Purpose of the Invention: To address the key technical issues of existing acoustic emission partial discharge detection systems, such as susceptibility to electromagnetic interference, low sensitivity, and low detection efficiency, this invention proposes a partial discharge detection method based on a fiber-optic acoustic emission sensor. By sensing the acoustic emission signal with a fiber-optic sensor and adjusting the detection range through FPGA control, this method offers low cost, strong anti-interference capabilities, and the ability to record acoustic emission signals over a wide intensity range.

[0006] Technical solution:

[0007] The partial discharge signal detection system based on the optical fiber acoustic emission sensor comprises a laser light source, a coupled optical fiber acoustic emission sensor, a photodetector, an I / U conversion, a conditioning circuit I, a conditioning circuit II, a low-speed ADC acquisition circuit, a high-speed ADC acquisition circuit, and an FPGA control module. The laser light source is connected to the coupled optical fiber acoustic emission sensor, two output routes of the coupled optical fiber acoustic emission sensor are connected to the photodetector, the photodetectors are respectively connected to the I / U conversion, the first output signal is connected to the conditioning circuit I after the I / U conversion, the second output signal is connected to the conditioning circuit II after the I / U conversion, the conditioning circuit I is connected to the low-speed ADC acquisition circuit, and the conditioning circuit II is connected to the high-speed ADC acquisition circuit. The FPGA control module is used to control the amplification gain, ADC acquisition, waveform recognition, and data processing of the two output signals of the two output routes.

[0008] The laser light source is a tunable high-narrow linewidth DFB semiconductor laser.

[0009] The coupled optical fiber acoustic emission sensor uses a single-mode fused-tapered optical fiber coupler, and the interior of the sensor adopts a substrate-plus-tube double-layer packaging structure.

[0010] The photodetector adopts a PIN-Si photodiode, and the frequency response can reach 3 GHz.

[0011] The conditioning circuit I includes a filter circuit, a programmable adjustable gain operational amplifier, and a detector; the conditioning circuit II includes a filter circuit and an analog switch-controlled feedback resistor amplifier circuit.

[0012] The coupled optical fiber acoustic emission sensor can be attached to the housing or interior of the electrical equipment by epoxy resin adhesive, and the laser light source and the circuit board can be remotely installed in the control room of the equipment site by optical fiber.

[0013] The detection method of the partial discharge signal detection system based on the optical fiber acoustic emission sensor comprises the following steps:

[0014] (1) Installing a coupled optical fiber acoustic emission sensor on or inside the housing of an electrical device to sense the acoustic emission signal generated by partial discharge of the electrical device;

[0015] (2) Fix the gain of conditioning circuit II and adjust the gain of conditioning circuit I through the FPGA control module so that the output voltages V1 and V2 of the two output signals after conditioning are equal;

[0016] (3) The conditioning circuit 1 converts the acoustic emission signal containing multiple frequency components into a low-frequency envelope signal and sends it to the low-speed ADC acquisition circuit for acquisition, which is used for initial judgment of signal validity and automatic range selection;

[0017] (4) After conditioning circuit II conditions the acoustic emission signal, the signal is collected by a high-speed ADC acquisition circuit for subsequent partial discharge signal recording and analysis and fault defect location;

[0018] (5) Based on the V1 data recorded by the low-speed ADC acquisition circuit, it is preliminarily determined whether the waveform is an acoustic emission signal: if it is not an acoustic emission signal, the V2 data recorded by the high-speed ADC acquisition circuit will not be output externally; if it is an acoustic emission signal, it is determined whether the gain of the conditioning circuit II during the recording of the partial discharge signal can make the range of the high-speed ADC acquisition circuit meet the effective recording of the V2 data. If not, the feedback resistor of the operational amplifier is selected through the FPGA control analog switch to select the appropriate gain for the next partial discharge signal recording.

[0019] Beneficial effects:

[0020] ①The detection frequency bandwidth of the system is 22.45k~300kHz, which fully meets the spectrum detection range of partial discharge of electrical equipment;

[0021] ②FPGA control adjusts the detection range and can record partial discharge signals with a wide intensity range of 100 to 10,000 pC;

[0022] ③The system has high sensitivity, reaching -70dB at 150kHz (reference V / μbar);

[0023] ④ It can be protected from the influence of high power density electromagnetic interference of power equipment on site;

[0024] ⑤ A single sensor can achieve reliable detection and recording of partial discharge signals at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall structure of the partial discharge signal detection system based on optical fiber acoustic emission sensor;

[0026] Figure 2 This is a diagram of the conditioning circuit I;

[0027] Figure 3 This is the diagram of the conditioning circuit II;

[0028] Figure 4This is a waveform diagram of the recorded output signal of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0030] The partial discharge detection system based on fiber optic acoustic emission sensor mainly includes laser light source, coupled fiber optic sensor, photoelectric detector, I / U conversion, signal conditioning, ADC acquisition circuit and FPGA control circuit, such as Figure 1 As shown:

[0031] (1) The laser light source is a tunable high-narrow linewidth DFB semiconductor laser with an output center wavelength of 1550nm.

[0032] (2) The core of the fiber optic acoustic emission sensor is a single-mode fused-tapered fiber optic coupler. Considering the presence of liquid inside some electrical equipment and at the same time making the sensor have a higher stress resistance strength, the sensor adopts a double-layer packaging structure of "substrate type + tube type" as a whole.

[0033] (3) The photodetector uses a PIN-Si photodiode with a frequency response of up to 3 GHz.

[0034] (4) Figure 2 As shown in the figure, the conditioning circuit I of one output arm of the sensor includes a filter circuit, a programmable adjustable-gain operational amplifier, and a detector. The filter circuit has a passband range of 20k to 300kHz, which can be adjusted based on the bandwidth of the test signal and interference conditions. The programmable adjustable-gain operational amplifier is a type with fine-tunable gain.

[0035] (5) Figure 3 As shown in Figure 1, the conditioning circuit II for the sensor's other output arm includes a filter circuit and an analog switch-controlled feedback resistor amplifier circuit. The filter circuit has a passband range of 20k to 300kHz, which can be adjusted based on the signal bandwidth and interference conditions in the field.

[0036] (6) The signal processed by conditioning circuit I is collected by a low-speed ADC; the signal processed by conditioning circuit II is collected by a high-speed ADC.

[0037] (7) FPGA control circuit is used to control the two-way output signal amplification gain, ADC acquisition, waveform recognition and data processing.

[0038] Among them, the fiber optic acoustic emission sensor can be tightly attached to the casing or interior of the electrical equipment through epoxy resin glue, and the light source and circuit board can be remotely installed in the control room at the equipment site through optical fiber.

[0039] Through the above system, the entire process of sensing, detecting and recording signals in a wide intensity range of partial discharge signals is realized.

[0040] In the experiment, the ball plate surface discharge model was used to simulate the local discharge source of electrical equipment. Under the condition of continuous discharge of different intensities, the output signal waveform of the device was recorded as follows: Figure 4 shown.

[0041] The filter circuit parameters in the present invention can be adjusted according to actual engineering application conditions.

[0042] The resistance values R1, R2, R3, and R4 of the reverse amplifier circuit in the conditioning circuit II of the present invention can be adjusted according to actual engineering application conditions.

[0043] The amplifying circuit of the conditioning circuit in the present invention should be adjusted to a multi-stage amplifying circuit in due time for measuring weak acoustic emission signals.

Claims

1. A method for detecting partial discharge signals based on an optical fiber acoustic emission sensor, characterized in that: The following steps are involved: (1) Install the coupled fiber optic acoustic emission sensor on the housing or inside of the electrical equipment to sense the acoustic emission signal generated by partial discharge of the electrical equipment; (2) Fix the gain of conditioning circuit II and adjust the gain of conditioning circuit I through the FPGA control module so that the output voltages V1 and V2 of the two output signals after conditioning are equal; (3) The conditioning circuit I converts the acoustic emission signal containing multiple frequency components into a low-frequency envelope signal and sends it to the low-speed ADC acquisition circuit for acquisition, which is used for initial judgment of signal validity and automatic range selection; (4) After conditioning circuit II conditions the acoustic emission signal, the signal is collected by the high-speed ADC acquisition circuit for subsequent partial discharge signal recording and analysis and fault defect location; (5) Based on the V1 data recorded by the low-speed ADC acquisition circuit, preliminarily determine whether the waveform is an acoustic emission signal: if it is not an acoustic emission signal, the V2 data recorded by the high-speed ADC acquisition circuit will not be output externally; if it is an acoustic emission signal, determine whether the gain of the conditioning circuit II during the partial discharge signal recording makes the range of the high-speed ADC acquisition circuit meet the effective recording of V2 data. If not, the FPGA controls the analog switch to select the feedback resistor of the operational amplifier to select the appropriate gain for the next partial discharge signal recording; The device used in the method includes a laser light source, a coupled fiber optic acoustic emission sensor, a photodetector, an I / U conversion, a conditioning circuit I, a conditioning circuit II, a low-speed ADC acquisition circuit, a high-speed ADC acquisition circuit, and an FPGA control module; the laser light source is connected to the coupled fiber optic acoustic emission sensor, two output routes of the coupled fiber optic acoustic emission sensor are connected to the photodetector, the photodetectors are respectively connected to the I / U conversion, the first output signal is connected to the conditioning circuit I after the I / U conversion, the second output signal is connected to the conditioning circuit II after the I / U conversion, the conditioning circuit I is connected to the low-speed ADC acquisition circuit, the conditioning circuit II is connected to the high-speed ADC acquisition circuit, and the FPGA control module is used to control the amplification gain, ADC acquisition, waveform recognition, and data processing of the two output signals of the two output routes; The conditioning circuit I includes a filter circuit, a programmable adjustable gain operational amplifier, and a detector; the conditioning circuit II includes a filter circuit and an analog switch controlled feedback resistor amplifier circuit.

2. The method for detecting partial discharge signals based on an optical fiber acoustic emission sensor according to claim 1, wherein: The laser light source is a tunable high-narrow linewidth DFB semiconductor laser.

3. The method for detecting partial discharge signals based on an optical fiber acoustic emission sensor according to claim 1, wherein: The coupled optical fiber acoustic emission sensor uses a single-mode fused-tapered optical fiber coupler, and the interior of the sensor adopts a substrate-plus-tube double-layer packaging structure.

4. The method for detecting partial discharge signals based on an optical fiber acoustic emission sensor according to claim 1, wherein: The photodetector adopts a PIN-Si photodiode, and the frequency response is up to 3 GHz.

5. The method for detecting partial discharge signals based on an optical fiber acoustic emission sensor according to claim 1, wherein: The coupled optical fiber acoustic emission sensor is tightly attached to the housing or interior of the electrical equipment through epoxy resin adhesive, and the laser light source and the circuit board are remotely installed in the control room of the equipment site through optical fibers.

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