A Method for Testing and Calibrating the Sensitivity Directivity of a Fiber Optic Sensor in Transformer Oil

Abstract

The present invention relates to a method for testing and calibrating the sensitivity directionality of a Fabry-Perot sensor in transformer oil. The method obtains sensitivity response values under different conditions by adjusting the distance and angle between the Fabry-Perot sensor and the sound source. The testing steps include setting the initial frequency and spacing, adjusting the angle and distance, and recording the response values under various conditions, and then drawing a sensor sensitivity diagram through normalization calculation. The calibration method uses a standard microphone for comparative testing and calibrates in combination with the attenuation coefficient to ensure the accuracy of the sound pressure sensitivity of the Fabry-Perot sensor. The present invention provides an efficient and reliable testing and calibration scheme that can significantly improve the application effect of the Fabry-Perot sensor in transformer oil, has high accuracy, and is suitable for complex environments.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor testing and calibration, and in particular to a sensitivity directionality testing and calibration method for a Fabry-Perot sensor in transformer oil. Background Art

[0002] As modern power systems expand and become increasingly complex, transformers, as core equipment in power transmission and distribution systems, have a direct impact on the safety and stability of the entire power grid through their operational reliability. Partial discharge (PD) in transformers is one of the main factors leading to insulation failure and serves as an early warning sign of potential transformer failure. Therefore, the detection and assessment of PD is crucial for ensuring the safe operation of transformers. Ultrasonic Fabry-Perot (Fabry-Perot) sensors, due to their high sensitivity, good frequency response, and strong resistance to electromagnetic interference, are increasingly being used for monitoring and diagnosing PD. However, the acoustic properties of transformer oil, the sensor's detection environment, differ significantly from those of air, posing new challenges to the Fabry-Perot (Fabry-Perot) sensor's acoustic pressure sensitivity and directivity.

[0003] To ensure the detection accuracy of Fabry-Perot (FPP) sensors in transformer oil, specialized sensitivity and directivity testing and calibration are required. This not only helps accurately assess the sensor's ability to receive acoustic signals in transformer oil but also provides precise acoustic field models and data support for fault diagnosis and partial discharge detection. However, due to significant differences between the physical properties of transformer oil, such as density, viscosity, and acoustic impedance, and those in air, directly using calibration results in air can result in significant errors. Therefore, developing a sensitivity and directivity testing and calibration method for Fabry-Perot (FPP) sensors specifically for transformer oil environments can effectively address this challenge in sensor performance evaluation and provide reliable technical support for sensor application under actual operating conditions. The development of this method will not only improve the sensor's application in the complex environment of oil but also promote the further development of ultrasonic detection technology based on Fabry-Perot (FPP) sensors in power equipment fault diagnosis. Summary of the Invention

[0004] The present invention provides a method for testing and calibrating the sensitivity and directionality of a Fabry-Perot sensor in transformer oil. The device applicable to the method includes: a host computer; a motor control module; an optical demodulator; a Fabry-Perot sensor; a transformer oil tank model; silencer cotton; a sound source; a slide supporting the precise movement and positioning of the Fabry-Perot sensor and the sound source; a signal generator for generating a stable sound source signal, the slide including a Fabry-Perot sensor transverse travel motor; a guide rail, the internal thread of which cooperates with the external thread of the slider to ensure the smooth movement of the slider in the slide rail groove; a Fabry-Perot sensor rotating motor, which rotates the slide rail to move the slider through the slide rail. The block is connected to the turntable; the slider; the turntable is connected to the Fabry-Perot sensor through the Fabry-Perot sensor connecting rod; the sound source rotation motor; the sound source lateral travel motor; the sound source fixing inverted Ω clamp, connected to the sound source connecting rod, used to stabilize the sound source; the connecting rod, including the Fabry-Perot sensor connecting rod and the sound source connecting rod, respectively used to connect the Fabry-Perot sensor and the sound source to their corresponding turntables; the slide rail groove; the limit block; the Fabry-Perot sensor fixing L-shaped inverted Ω clamp, connected to the Fabry-Perot sensor connecting rod, used to clamp the Fabry-Perot sensor; the slide holder, used to firmly clamp the slide on the transformer mailbox model;

[0005] S1: Power on the device, set the initial frequency of the sound source to f0, and the initial distance between the sound source and the Fabry-Perot sensor to X0, where X0 is greater than the minimum distance and less than the maximum distance.

[0006] S2: Control the Fabry-Perot sensor rotation motor and the sound source rotation motor so that the angle between the Fabry-Perot sensor sensitive diaphragm plane and the sound source plane is 0°;

[0007] S3: Control the motor of the Fabry-Perot sensor to change the turntable angle in steps of 10° or 30°. The turntable angle is in the range of [0, 360°), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane. The response values Yd00, Yd01, Yd02, ..., at different angles when the spacing is X0 are recorded.

[0008] S4: Control the lateral travel motor of the Fabry-Perot sensor and the lateral travel motor of the sound source, change the distance X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, repeat step S3, and record the response values at different angles:

[0009] Yd10, Yd11, Yd12,…;

[0010] Yd20, Yd21, Yd22,…;

[0011] Yd30, Yd31, Yd32,…;

[0012] …;

[0013] Ydn0, Ydn1, Ydn2,…;

[0014] S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test:

[0015] Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……;

[0016] Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…;

[0017] Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…;

[0018] ...;

[0019] Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,…;

[0020] Based on the calculation results, draw the sensor directional sensitivity diagram;

[0021] S6: Change the sound source frequency, repeat steps S2-S5, and draw a directional sensitivity diagram of the sensor at different frequencies.

[0022] Beneficial effects:

[0023] The present invention provides an efficient and reliable testing and calibration solution, which can significantly improve the application effect of Fabry-Perot sensors in transformer oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A diagram of a device used for directivity testing according to an embodiment of the present invention;

[0025] Figure 2 A structural diagram of a slide according to an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the minimum distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0027] Figure 4 A schematic diagram of an arbitrary distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0028] Figure 5 Schematic diagram of the maximum distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0029] Figure 6 Schematic diagram of the angle change between the Fabry-Perot sensor and the sound source plane according to an embodiment of the present invention;

[0030] Figure 7 Flow chart of a test process in a method for testing and calibrating the sensitivity directivity of a Fabry-Perot sensor in transformer oil according to an embodiment of the present invention;

[0031] Figure 8 This is a flow chart of the calibration process in the sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil;

[0032] Figure 9 1 is a sensitivity directivity test diagram of a Fabry-Perot sensor in transformer oil according to an embodiment of the present invention.

[0033] Figure numerals: 1-host computer; 2-motor control module; 3-optical demodulator; 4-Fabry-Perot sensor; 5-transformer oil tank model; 6-silence cotton; 7-sound source; 8-slide; 9-signal generator; 801-Fabry-Perot sensor lateral travel motor; 802-guide rail; 803-Fabry-Perot sensor rotation motor; 804-slide; 805-turntable; 806-sound source rotation motor; 807-sound source lateral travel motor; 808-sound source fixed inverted Ω clamp; 809-connecting rod; 810-slide rail groove; 811-limiting block; 812-Fabry-Perot sensor fixed L-shaped inverted Ω clamp; 813-slide holder. DETAILED DESCRIPTION

[0034] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0035] Figure 1 FIG. 1 is a diagram of a device used for directivity testing according to an embodiment of the present invention. Figure 1 As shown in the figure, the test device mainly includes the following components: a host computer 1, which is used to control the test process and process data; a motor control module 2, which is responsible for controlling the movement and rotation of the Fabry-Perot sensor and the sound source; an optical demodulator 3, which is used to receive and demodulate the sound signal detected by the Fabry-Perot sensor; a Fabry-Perot sensor 4, which performs testing by sensing the changes in the sound signal; a transformer tank model 5, which simulates the working environment of the transformer; a sound-absorbing cotton 6, which is used to reduce the reflection of sound waves; a sound source 7, which provides a sound signal with adjustable frequency; a slide 8, which supports the precise movement and positioning of the Fabry-Perot sensor and the sound source; and a signal generator 9, which is used to generate a stable sound source signal.

[0036] Figure 2 FIG. 1 is a structural diagram of a slide according to an embodiment of the present invention. Figure 2As shown, the slide mainly includes a Fabry-Perot sensor transverse travel motor 801, which is used to control the precise horizontal movement of the Fabry-Perot sensor to ensure that the displacement of the sensor is controllable during the test. The external thread of the guide rail 802 cooperates with the internal thread of the slider 804 to ensure the smooth movement of the slider 804 in the slide rail groove 810. The Fabry-Perot sensor rotation motor 803, connected to the slider 804 and the turntable 805 through the slider 804, is responsible for adjusting the rotation angle of the sensor, enabling multi-angle testing and thus achieving directivity measurement of sensitivity. The slider 804 is located on the slide and is used to support and guide the movement of the Fabry-Perot sensor, ensuring that the slide system has good stability and vibration resistance during operation. Its diameter is smaller than the slide rail groove 810, and its travel range is between the Fabry-Perot sensor transverse travel motor 801 and the limit block 811. The turntable 805 is connected to the Fabry-Perot sensor rotation motor 803, supporting the angle adjustment of the Fabry-Perot sensor during rotation, ensuring that it can operate stably at different angles. The sound source rotation motor 806 is connected to the turntable through the corresponding slider, which is used to control the rotation of the sound source, thereby adjusting the incident direction of the sound wave and cooperating with the Fabry-Perot sensor to perform sensitivity tests in different directions. The sound source transverse travel motor 807 adjusts the distance between the sound source and the sensor by moving the sound source horizontally, so that the test can cover different distance ranges. The sound source fixed inverted Ω clamp 808 is connected to the sound source connecting rod and is used to stabilize the sound source to ensure that it remains stable during movement or rotation and prevent test errors caused by offset. The connecting rod 809 includes a Fabry-Perot sensor connecting rod and a sound source connecting rod, which are respectively used to connect the Fabry-Perot sensor and the sound source to their respective corresponding turntables to ensure the stability of the overall structure. The Fabry-Perot sensor fixed L-shaped inverted Ω clamp 812 is connected to the Fabry-Perot sensor connecting rod and is used to clamp the Fabry-Perot sensor 4 so that the plane of its sensitive diaphragm coincides with the axis of the Fabry-Perot sensor connecting rod to ensure that when the sensor rotates, the distance between the response sensitive area and the sound source remains unchanged. The slide holder 813 is used to firmly clamp the slide on the transformer mailbox model 5 to ensure the stability of the equipment during the test.

[0037] When the sliders on both sides (slider 804 and the slider corresponding to the sound source rotating motor 806) are close to the limit blocks, there is a minimum distance Xmin between the Fabry-Perot sensor 4 and the sound source 7. When the sliders on both sides are close to the motors at both ends, there is a maximum detection Xmax between the Fabry-Perot sensor 4 and the sound source 7. This structure limits the stroke of the slider 804, and the specific value is determined according to actual detection needs.

[0038] Figure 3 Schematic diagram of the minimum distance between the Fabry-Perot sensor and the sound source according to an embodiment of the present invention. Figure 3As shown, the minimum distance Xmin is set between the Fabry-Perot sensor 4 and the sound source 7. This ensures that the sensor can effectively receive the acoustic signal without interference during sensitivity testing. Setting this minimum distance helps prevent signal distortion caused by close proximity and ensures optimal data acquisition. By adjusting the slide system, the distance between the Fabry-Perot sensor and the sound source can be precisely controlled, ensuring that it remains above this minimum value throughout the test.

[0039] Figure 4 Schematic diagram of arbitrary distance between Fabry-Perot sensor and sound source according to an embodiment of the present invention. Figure 4 As shown, the Fabry-Perot sensor can be set at any distance from the sound source. This flexibility allows testing to adapt to a variety of experimental conditions. In practical applications, the distance between the Fabry-Perot sensor and the sound source can be freely adjusted to meet different test requirements, enabling a comprehensive evaluation of sensor performance. This arbitrary spacing setting provides greater convenience for subsequent testing and calibration.

[0040] Figure 5 Schematic diagram of the maximum distance between the Fabry-Perot sensor and the sound source according to an embodiment of the present invention. Figure 5 The figure shows the maximum distance Xmax set between the Fabry-Perot sensor 4 and the sound source 7. This distance is designed to ensure the effectiveness of the acoustic signal during propagation and the sensor's reception capability. During sensitivity testing, this maximum distance is set to prevent the acoustic signal from attenuating to the point where it cannot be effectively captured by the sensor. Precise control of the slide maintains the Fabry-Perot sensor and sound source within the maximum detection range, ensuring the accuracy and reliability of test data.

[0041] Figure 6 Schematic diagram of the angle change between the Fabry-Perot sensor and the sound source plane according to an embodiment of the present invention. Figure 6 As shown, the initial angle between the Fabry-Perot sensor 4 and the sound source 7 is 0°. During the test, the Fabry-Perot sensor rotates clockwise to detect sensitivity at different angles. While the sound source position remains unchanged, the Fabry-Perot sensor plane rotates clockwise. The detection accuracy can be customized based on actual needs, with steps of 10° or 30°. In this diagram, the angles between the axis of the Fabry-Perot sensor's sensitive diaphragm and the horizontal axis are 30° and 270°, respectively, illustrating the sensor's position at different angles.

[0042] Figure 7 FIG1 is a flow chart of the test process of the sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil according to an embodiment of the present invention. Figure 7 As shown, the main steps are:

[0043] S1: Power on the device, set the initial frequency of the sound source to f0, and the initial distance between the sound source and the Fabry-Perot sensor to X0 (Xmin≤X0≤Xmax).

[0044] S2: Control the Fabry-Perot sensor rotation motor 803 and the sound source rotation motor 806 so that the angle between the plane of the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source is 0°;

[0045] S3: Control the Fabry-Perot sensor to rotate the motor 803, changing the turntable angle by 10° or 30° (range [0, 360°)), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, and recording the response values Yd00, Yd01, Yd02, ... measured by the optical demodulator at different angles when the spacing X0 is set;

[0046] S4: Control the lateral travel motor 801 of the Fabry-Perot sensor and the lateral travel motor 807 of the sound source, change the distances X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, repeat step S3, and record the response values at different angles:

[0047] Yd10, Yd11, Yd12, ...;

[0048] Yd20, Yd21, Yd22, ...;

[0049] Yd30, Yd31, Yd32, ...;

[0050] …;

[0051] Ydn0, Ydn1, Ydn2, ...;

[0052] X1, X2, ..., Xn are set in increments of 50mm or 100mm between the minimum and maximum distances, such as X1=Xmin+50mm, X2=X1+50mm, ..., Xn=Xmin+n. 50mm.

[0053] S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test:

[0054] Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……;

[0055] Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…;

[0056] Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…;

[0057] ...;

[0058] Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,….

[0059] Based on the calculated results, a sensor directional sensitivity diagram is plotted. This diagram uses the maximum value of the optical interrogator response obtained from actual testing as the normalized denominator (generally, the response value Yd00, when the angle between the closest Fabry-Perot sensor's sensitive diaphragm and the sound source plane is 0°). Other values at different distances and angles are used as the normalized numerators. The resulting normalized values are then plotted on the radar chart as a directional sensitivity diagram.

[0060] S6: Change the sound source frequency, such as 20kHz, 40kHz, 60kHz. The specific step is determined according to the actual measurement requirements, including but not limited to 20kHz step. Repeat steps S2-S5 to draw the sensor directional sensitivity diagram at different frequencies.

[0061] Figure 8 This is a flow chart of a calibration process of a sensitivity directivity test and calibration method of a Fabry-Perot sensor in transformer oil according to an embodiment of the present invention. The calibration method comprises the following steps:

[0062] T1: Replace the Fabry-Perot sensor in the test method with a standard microphone that can be used in oil;

[0063] T2: Repeat S1-S4 of the test method, and the standard microphone recording value is Y' under different conditions in the corresponding test method;

[0064] T3: Considering the differences in attenuation effects of different sensors in transformer oil, the calibration coefficient k=(Y'-b) / Y, where Y is the response value of the optical demodulator measured under different conditions, and b is a constant term determined by the calibration test. The relationship between the Fabry-Perot sensor and the standard microphone includes but is not limited to a linear relationship.

[0065] T4: After calibration is completed, the true value kY of the sensor's sound pressure sensitivity is obtained.

[0066] Figure 9This is a sensitivity directivity test chart according to an embodiment of the present invention, showing the normalized response values of the sensor over an angular range of 0° to 360°. During the test, the initial angle between the Fabry-Perot sensor and the sound source was set to 0°. The angle between the Fabry-Perot sensor's sensitive diaphragm and the sound source plane was gradually adjusted in steps of 10° or 30°. At each angle, the response value was recorded and normalized, with the normalized baseline being the sensor's response value at an angle of 0° and the initial distance. This yielded a sequence of normalized response values at different angles. The horizontal axis of the result chart represents the angle, ranging from 0° to 360°, and the vertical axis represents the normalized response value. The chart clearly shows that the sensor's response exhibits specific trends at different angles. At certain angles, the response value reaches a peak, indicating the sensor's highest sensitivity at those angles; at other angles, the response value decreases, indicating lower sensitivity in those directions. This test chart effectively evaluates the sensor's sensitivity and directivity, helping to determine its optimal operating conditions at different angles. This sensitivity directivity test chart provides intuitive data for analyzing sensor performance, allowing for optimized sensor placement based on angular requirements in applications.

[0067] Based on the sensitivity directivity test chart, plotting the same distance and different frequencies on the same coordinates can produce the sensor's frequency-dependent sensitivity curve. Furthermore, plotting the calibrated kY values on the same coordinates can produce the sensor's actual sound pressure sensitivity curve.

[0068] Obviously, the above embodiments are merely examples for clarification and are not intended to limit the implementation methods. For those skilled in the art, other variations or modifications can be made based on the above description, and such variations or modifications are still within the scope of protection of the present invention.

Claims

1. A method for testing and calibrating the sensitivity and directionality of a Fabry-Perot sensor in transformer oil, characterized in that: The device applicable to the method includes: a host computer (1); a motor control module (2); an optical demodulator (3); a Fabry-Perot sensor (4); a transformer oil tank model (5); a silencer (6); a sound source (7); a slide (8), which supports the precise movement and positioning of the Fabry-Perot sensor and the sound source; a signal generator (9), which is used to generate a stable sound source signal, and the slide (8) includes a Fabry-Perot sensor transverse travel motor (801); a guide rail (802), the internal thread of which cooperates with the external thread of the slider (804) to ensure the smooth movement of the slider (804) in the slide rail groove (810); a Fabry-Perot sensor rotation motor (803), which is connected to the turntable (805) through the slider (804); and a slider. (804); a turntable (805), connected to the Fabry-Perot sensor via a Fabry-Perot sensor connecting rod; a sound source rotating motor (806); a sound source lateral travel motor (807); a sound source fixing inverted Ω clamp (808), connected to the sound source connecting rod, for stabilizing the sound source; a connecting rod (809), including a Fabry-Perot sensor connecting rod and a sound source connecting rod, for connecting the Fabry-Perot sensor and the sound source to their respective corresponding turntables; a slide rail groove (810); a limit block (811); a Fabry-Perot sensor fixing L-shaped inverted Ω clamp (812), connected to the Fabry-Perot sensor connecting rod, for clamping the Fabry-Perot sensor (4); a slide holder (813), for firmly clamping the slide on the transformer mailbox model (5); S1: Power on the device, set the initial frequency of the sound source to f0, and the initial distance between the sound source and the Fabry-Perot sensor to X0, where X0 is greater than the minimum distance and less than the maximum distance. S2: Controlling the Fabry-Perot sensor rotation motor (803) and the sound source rotation motor (806) so that the angle between the plane of the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source is 0°; S3: Control the Fabry-Perot sensor to rotate the motor (803), and change the turntable angle by 10° or 30°. The turntable angle is within the range of [0, 360°), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, and recording the response values Yd00, Yd01, Yd02, ... measured by the optical demodulator at different angles when the spacing X0 is recorded; S4: Control the Fabry-Perot sensor transverse travel motor (801) and the sound source transverse travel motor (807), change the distances X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, repeat step S3, and record the response values at different angles: Yd10, Yd11, Yd12,…; Yd20, Yd21, Yd22,…; Yd30, Yd31, Yd32,…; …； Ydn0, Ydn1, Ydn2,…; S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test: Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……; Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…; Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…; ……； Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,…; Based on the calculation results, draw the sensor directional sensitivity diagram; S6: Change the sound source frequency, repeat steps S2-S5, and draw a directional sensitivity diagram of the sensor at different frequencies.

2. The sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil according to claim 1, wherein It also includes the calibration process, which includes: T1: Replace the Fabry-Perot sensor in the test method with a standard microphone that can be used in oil; T2: Repeat S1-S4 of the test method, and the standard microphone recording value is Y' under different conditions in the corresponding test method; T3: Considering the differences in attenuation effects of different sensors in transformer oil, the calibration coefficient k=(Y'-b) / Y, where Y is the response value of the optical demodulator measured under different conditions, and b is a constant term determined by calibration tests. The relationship between the Fabry-Perot sensor and the standard microphone includes but is not limited to a linear relationship; T4: After calibration is completed, the true value kY of the sensor's sound pressure sensitivity is obtained.

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