Ultrasonic sensor area array positioning system and method of Fabry-Perot interferometer

Abstract

The invention relates to the technical field of transformer partial discharge positioning, in particular to an ultrasonic sensor area array positioning system and method for a Fabry-Perot interferometer, and the system consists of a Fabry-Perot laser, an optical fiber coupler, an optical fiber circulator, an optical fiber ultrasonic sensor area array, a photoelectric detector, a data collector and a host terminal. A first port of the optical fiber coupler and a first port of the optical fiber circulator are sequentially connected along the transmission direction of emergent light of the Fabry-Perot laser, a second port of the optical fiber circulator is connected with the optical fiber ultrasonic transmission area array, and a third port of the optical fiber circulator is connected with the photoelectric detector. A plurality of optical fiber ultrasonic sensors are integrated in a stainless steel probe, the construction process of an ultrasonic sensor array is simplified, the time difference of signal receiving of an ultrasonic sensor area array positioning system is converted into a nonlinear equation set for solving, and coordinate positioning of a partial discharge position is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of transformer partial discharge positioning, and in particular to an ultrasonic sensor array positioning system and method of a Fabry-Perot interferometer. Background Art

[0002] With the development of power grid construction, the application of high-voltage power equipment has become more and more extensive. As a core component of the high-voltage power system, if a power transformer fails, it may cause a large-scale power outage, causing huge losses to social production and life. Therefore, accurate monitoring of partial discharge has become an indispensable technical support for ensuring the stable operation of the power system.

[0003] At present, the monitoring of partial discharge of power transformers relies on various physical phenomena that occur during partial discharge, including ultrasonic waves, electric pulses, electromagnetic radiation, local overheating, gas generation, etc. Based on the above phenomena, a variety of partial discharge detection technologies have been developed, including ultrasonic detection, electric pulse detection, gas chromatography detection, electromagnetic wave detection, etc. Conventional partial discharge detection elements are electrical components, but they are easily affected by electromagnetic interference during the detection process.

[0004] At present, the common ultrasonic sensors are electrical sensors. In the application of partial discharge detection, both high-voltage power equipment and sensors are energized, with poor insulation and susceptibility to electromagnetic interference, resulting in greater danger. In recent years, some researchers have proposed ultrasonic sensors based on interference fiber structures, which can effectively avoid problems such as poor insulation and electromagnetic interference. However, the commonly used light source is a single-wavelength laser, which is easily interfered by external factors during use. In addition, when using the intensity-based demodulation method, working point drift is prone to occur, resulting in a decrease in the sensitivity of the ultrasonic sensor, and the stability of the monitoring system cannot be guaranteed. At the same time, a single ultrasonic sensor sometimes cannot meet the needs of partial discharge positioning. Some researchers have built ultrasonic sensor arrays, but building sensor arrays is relatively complex and requires calibration during deployment, which increases the difficulty of installation and maintenance. Summary of the invention

[0005] In order to solve the above problems, the present invention provides, on one hand, a Fabry-Perot interferometer ultrasonic sensor array positioning system, which is composed of a Fabry-Perot laser, a fiber coupler, a fiber circulator, a fiber ultrasonic sensor array, a photoelectric detector, a data collector and a host terminal; along the transmission direction of the output light of the Fabry-Perot laser, the first ports of the fiber coupler and the fiber circulator are connected in sequence, the second port of the fiber circulator is connected to the fiber ultrasonic transmission array, and the third port thereof is connected to the photoelectric detector, the photoelectric detector is electrically connected to the input end of the data collector, and the output end of the data collector is electrically connected to the host terminal; The fiber optic ultrasonic sensor array is used to detect ultrasonic signals during partial discharge and generate interference light intensity signals carrying ultrasonic characteristic information according to the vibration of the ultrasonic signal; the fiber optic ultrasonic sensor array includes a stainless steel probe, a stainless steel diaphragm and an optical fiber assembly, the stainless steel probe is penetrated with a plurality of jacks along the axial direction, a plurality of stainless steel diaphragms are fixedly bonded to one side of the stainless steel probe at the jack position, a plurality of optical fiber assemblies are fixedly installed to the jack on the side of the stainless steel probe away from the stainless steel diaphragm, and the insertion depth of the optical fiber assembly is less than the axial length of the stainless steel probe.

[0006] In a specific embodiment, the optical fiber assembly includes a single-mode optical fiber, an optical fiber ceramic ferrule and a stainless steel sleeve. The single-mode optical fiber is fixedly connected to one end of the optical fiber ceramic ferrule, the single-mode optical fiber is externally sleeved with a stainless steel sleeve, and the stainless steel sleeve is fixedly connected to the optical fiber ceramic ferrule.

[0007] In order to meet the interference condition of the laser beam, the end face of the optical fiber ceramic ferrule away from the end of the single-mode optical fiber is parallel to and directly faces the inner surface of the stainless steel diaphragm.

[0008] The end face of the optical fiber ceramic ferrule away from one end of the single-mode optical fiber and the plane of the stainless steel diaphragm are perpendicular to the axial direction of the stainless steel probe.

[0009] The central axes of the single-mode optical fiber and the optical fiber ceramic ferrule pass through the center of the stainless steel diaphragm.

[0010] In a specific implementation, a plurality of optical fiber circulators and photoelectric detectors are provided, and the number of the optical fiber circulators is equal to the number of the jacks of the stainless steel probe.

[0011] On the other hand, a method for positioning an ultrasonic sensor array of a Fabry-Perot interferometer is provided, which is applied to the ultrasonic sensor array positioning system of the Fabry-Perot interferometer as described above, and comprises: S1. According to the position and spacing of each array element of the optical fiber ultrasonic sensor array, select any array element as the coordinate origin to establish a three-dimensional rectangular coordinate system, and determine the three-dimensional coordinates of each array element; S2, obtaining the interference light intensity signal of each array element of the optical fiber ultrasonic sensor, and performing photoelectric conversion on the interference light intensity signal to obtain a voltage value; S3. Based on the voltage value of each array element, determine the occurrence time of the voltage value change of each array element; according to the occurrence time of each array element, determine the time delay difference between the coordinate origin array element and other array elements; S4. Based on the medium propagation speed of ultrasonic waves, a set of equations is constructed according to the three-dimensional coordinates of each array element, the array element spacing and the time delay difference to calculate the coordinates of the target sound source, which is the partial discharge position.

[0012] In S4, the equation group is constructed according to the three-dimensional coordinates of each array element, the array element spacing and the delay difference: , Where x, y, z are the spatial coordinates of the target sound source; x i , y i , z i , i=1,2,…5, represents the three-dimensional coordinates of the i-th array element; c Indicates the propagation speed of ultrasonic waves; d i is the spatial distance from the target sound source to the i-th array element; τ i is the time delay difference between the ith array element and the array element at the origin of the coordinate system. Beneficial Effects

[0013] (1) The ultrasonic sensor array positioning system of the present invention can effectively avoid the problems of traditional electrical ultrasonic sensors being susceptible to electromagnetic interference and poor insulation in partial discharge detection of high-voltage power equipment, thereby reducing safety risks and improving the stability of ultrasonic detection.

[0014] (2) The ultrasonic sensor array positioning system of the present invention effectively avoids the phenomenon of serious sensitivity reduction caused by working point drift when the light source of the interference fiber optic ultrasonic sensor system is a single-wavelength laser using the intensity demodulation method, thereby enhancing the stability of the system.

[0015] (3) The present invention innovatively integrates several fiber optic ultrasonic sensors into a stainless steel probe, which not only reduces costs but also greatly simplifies the process of building an ultrasonic sensor array. The spacing between fiber optic ultrasonic sensor array elements is fixed and does not require recalibration, which simplifies the positioning process and deployment process.

[0016] (4) Based on the characteristics of the acoustic wave signal in the air environment, the characteristics of the acoustic wave signal transmitted by the optical fiber and the geometric relationship of the optical fiber ultrasonic sensor array, the present invention uses the TDOA (Time Difference of Arrival) method to convert the time difference of the received signal of the ultrasonic sensor array positioning system into a nonlinear equation group, and then solves the nonlinear equation group to realize the coordinate positioning of the partial discharge position. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of the ultrasonic sensor array positioning system of the present invention; Figure 2 It is a structural schematic diagram of the optical fiber ultrasonic sensor array; Figure 3This is the assembly diagram of the fiber optic ultrasonic sensor array; Figure 4 It is a schematic flow chart of the ultrasonic sensor array positioning method of the Fabry-Perot interferometer of the present invention; 1. Stainless steel casing; 2. Single-mode optical fiber; 3. Optical fiber ceramic ferrule; 4. Stainless steel probe; 5. Stainless steel diaphragm. DETAILED DESCRIPTION

[0018] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0019] See also Figure 1 This embodiment provides a Fabry-Perot interferometer ultrasonic sensor array positioning system, which is composed of a Fabry-Perot laser (FP laser for short), a fiber coupler, a fiber circulator, a fiber ultrasonic sensor array, a photodetector, a data collector, and a host terminal. The FP laser is located at the initial end of the optical path of the entire system, and is connected to the first ports of the fiber coupler and the fiber circulator in sequence along the transmission direction of the FP laser output light. The second port of the fiber circulator is connected to the fiber ultrasonic transmission array, and its third port is connected to the photodetector. The photodetector is electrically connected to the input end of the data collector, and the output end of the data collector is electrically connected to the host terminal.

[0020] The optical fiber ultrasonic sensor array is used to detect the ultrasonic signal during partial discharge, and generates an interference light intensity signal carrying ultrasonic characteristic information according to the vibration of the ultrasonic signal. In order to realize the detection of ultrasonic signals by the optical fiber ultrasonic sensor array, Figure 2 , Figure 3 As shown, the fiber optic ultrasonic sensor array includes a stainless steel probe 4, a stainless steel diaphragm 5 and an optical fiber assembly. The stainless steel probe 4 is provided with a plurality of insertion holes along the axial direction. One side of the stainless steel probe 4 is located at the position of the insertion holes and fixedly bonded with a plurality of stainless steel diaphragms 5. The insertion holes on the side of the stainless steel probe 4 away from the stainless steel diaphragm 5 are fixedly installed with a plurality of optical fiber assemblies. The insertion depth of the optical fiber assembly is less than the axial length of the stainless steel probe 4.

[0021] The optical fiber ultrasonic sensor array is composed of a plurality of optical fiber ultrasonic sensor array elements. The optical fiber assembly and the stainless steel diaphragm 5 together form a single optical fiber ultrasonic sensor. Specifically, the optical fiber assembly includes a single-mode optical fiber 2, an optical fiber ceramic ferrule 3 and a stainless steel sleeve 1. The single-mode optical fiber 2 is fixedly connected to one end of the optical fiber ceramic ferrule 3. The stainless steel sleeve 1 is sleeved on the outside of the single-mode optical fiber 2, and the stainless steel sleeve 1 is fixedly connected to the optical fiber ceramic ferrule 3. By inserting the optical fiber assembly into any one of the jacks of the stainless steel probe 4, a gap is provided between the end of the optical fiber ceramic ferrule 3 away from the single-mode optical fiber 2 and the stainless steel diaphragm 5, and the end face of the optical fiber ceramic ferrule 3 at this end is parallel and facing the inner surface of the stainless steel diaphragm 5, so that the reflected light beam on the inner surface of the stainless steel diaphragm 5 and the light beam reflected by the end face of the optical fiber ceramic ferrule 3 can meet the interference condition. When the stainless steel probe 4 of the optical fiber ultrasonic sensor array receives the ultrasonic signal emitted by the local discharge inside the power transformer box, the ultrasonic wave acts on the front surface of the stainless steel diaphragm 5 on one side of the stainless steel probe 4. The stainless steel diaphragm 5 is vibrated by the ultrasonic wave, and the optical path difference between the two light beams reflected by its inner surface and the optical fiber ceramic ferrule 3 changes, thereby causing the output light intensity to change.

[0022] In a specific implementation, in order to ensure the accuracy of ultrasonic signal detection, the end face of the optical fiber ceramic ferrule 3 away from one end of the single-mode optical fiber 2 and the plane of the stainless steel diaphragm 5 are perpendicular to the axial direction of the stainless steel probe 4, forming a non-intrinsic Fabry-Perot cavity with a certain cavity length; the central axis of the single-mode optical fiber 2 and the optical fiber ceramic ferrule 3 passes through the center of the stainless steel diaphragm 5, ensuring that the laser light beam transmitted by the single-mode optical fiber 2 is vertically incident on the center position of the stainless steel diaphragm 5, and in the absence of the influence of ultrasonic signal vibration, the interference light intensity signal between the optical fiber ceramic ferrule 3 and the stainless steel diaphragm 5 is a constant value.

[0023] In order to realize the positioning detection of partial discharge and meet the detection quantity of the optical fiber ultrasonic sensor array, the optical fiber circulator and the photoelectric detector are provided in a plurality, and the number of the optical fiber circulator is the same as the number of the jacks of the stainless steel probe 4. The optical fiber coupler can split the outgoing light emitted by the FP laser, and respectively connect it to the first port of the optical fiber circulator through the optical fiber. The optical fiber circulator can carry out directionally propagation of the connected laser, and input it to the optical fiber ultrasonic sensor array through the second port. On the one hand, the laser signal is transmitted to the optical fiber ultrasonic sensor array to improve the light source; on the other hand, the detection light signal fed back by the optical fiber ultrasonic sensor array is received through the second port. At the same time, the third port of each optical fiber circulator is connected to a photoelectric detector separately, and the detection light signal transmitted from the second port can be transmitted to the photoelectric detector. The photoelectric detector can convert the light signal into an electrical signal, and transmit it to the data collector for digital conversion and collection of the electrical signal.

[0024] The working principle of the ultrasonic sensor array positioning system is as follows: the FP laser is used as a light source, which is located at the initial end of the optical path and emits an outgoing laser to the optical fiber coupler. The optical fiber coupler splits the outgoing laser, and inputs the splitted laser beams through the first port of the optical fiber circulator, and the laser beams are directionally propagated inside the optical fiber circulator; the second ports of the optical fiber circulators are input to the optical fiber ultrasonic sensor array for ultrasonic signal detection, and the interference light intensity signal carrying ultrasonic characteristic information is transmitted to the corresponding photoelectric detector through the third port of the optical fiber circulator for photoelectric conversion. The photoelectric detector transmits the converted voltage signal to the data collector, and the data collector uniformly transmits the collected multi-channel voltage signals to the host terminal for data processing and analysis to determine the positioning information of partial discharge of the power transformer.

[0025] In addition, this embodiment also provides a Fabry-Perot interferometer ultrasonic sensor array positioning method, which is applied to the above-mentioned Fabry-Perot interferometer ultrasonic sensor array positioning system, such as Figure 4 As shown, the specific implementation steps of the method are as follows: S1. According to the position and spacing of each array element of the optical fiber ultrasonic sensor array, select any array element as the coordinate origin to establish a three-dimensional rectangular coordinate system, and determine the three-dimensional coordinates of each array element; This application takes five optical fiber ultrasonic sensor array elements as an example. A optical fiber ultrasonic sensor is arranged at the center of the front end of the stainless steel probe 4 of the optical fiber ultrasonic sensor array, and the remaining optical fiber ultrasonic sensors are symmetrically distributed around the center of the circle. The array element spacing of each optical fiber ultrasonic sensor to the center of the circle is equal. The optical fiber ultrasonic sensor array at the center of the circle is selected as the coordinate origin to establish a three-dimensional rectangular coordinate system. The three-dimensional coordinate values ​​of each array element are determined based on the array element spacing: , in, x i , y i , z i , i =1,2,…5, indicating the i The three-dimensional coordinates of the array elements; d is the array element spacing.

[0026] S2, obtaining the interference light intensity signal of each array element of the optical fiber ultrasonic sensor, and performing photoelectric conversion on the interference light intensity signal to obtain a voltage value; A Fabry-Perot interferometer cavity is formed based on the end face of the optical fiber ceramic ferrule 3 and the inner surface of the stainless steel diaphragm 5, and a double-beam interference is generated by transmitting a laser beam through the single-mode optical fiber 2; the stainless steel diaphragm 5 is dynamically deformed based on the action of the sound wave according to the ultrasonic signal received by the detection; and the interference light intensity signal of the change of the Fabry-Perot interferometer cavity length is determined based on the deformed stainless steel diaphragm 5; When the ultrasonic wave acts on the stainless steel diaphragm 5, its surface undergoes dynamic deformation, causing the length of the Fabry-Perot interference cavity of the optical fiber ultrasonic sensor array to change, and the phase shift optical path difference of the interference fringes also changes accordingly. The deformation amount y of the stainless steel diaphragm 5 under the action of sound pressure is: , in, P is the sound pressure acting on the fiber optic ultrasonic sensor array, μ is the Poisson's ratio of the stainless steel diaphragm 5, R is the effective radius of the stainless steel diaphragm 5, E is the Young's modulus of the stainless steel diaphragm 5, h The thickness of the stainless steel diaphragm is 5. f 1 is the vibration frequency of the first-order vibration mode of the stainless steel diaphragm 5, f 00 is the vibration frequency of the ultrasonic signal, is the damping coefficient of the stainless steel diaphragm 5 when it is subjected to forced vibration; According to the interference principle, the interference light intensity signal of the Fabry-Perot interference cavity length change is: , , in, R 1. R 2 respectively represent the reflectivity of the end face of the optical fiber ceramic ferrule 3 and the stainless steel diaphragm 5, Φ is the phase difference of adjacent light beams, n is the refractive index of air in the interference cavity, L is the length of the interference cavity, λ 0 is the wavelength of the FP laser.

[0027] The photodetector converts the transmitted interference light intensity signal into a photocurrent, and then converts the photocurrent into a voltage signal, and the formula is: , , in, I ph is the photocurrent, γ is the photoelectric conversion efficiency, V ph is the voltage value, R is the voltage of the photoelectric conversion module.

[0028] S3. Based on the voltage value of each array element, determine the occurrence time of the voltage value change of each array element; according to the occurrence time of each array element, determine the time delay difference between the coordinate origin array element and other array elements; When local discharge occurs inside the power transformer, the stainless steel probe 4 detects the ultrasonic signal. Under the action of ultrasonic vibration, the stainless steel diaphragm 5 of the optical fiber ultrasonic sensor of each array element vibrates, causing the length of the interference cavity to change, and then the interference light intensity signal changes. The voltage value output by the photoelectric detector also changes. The moment when each array element receives the ultrasonic signal is the moment when the voltage value of each array element changes after photoelectric conversion. Because the optical fiber ultrasonic sensors of different array elements receive the ultrasonic signal at different times, the time when their voltage value changes is also different. The moment when the ultrasonic signal reaches the optical fiber ultrasonic sensor at the center of the circle is taken as the zero point. The remaining optical fiber ultrasonic sensor array elements have a certain time delay when receiving the ultrasonic signal compared to the zero point. The time delay difference is recorded as , , , .

[0029] S4. Based on the medium propagation speed of ultrasonic waves, a set of equations is constructed according to the three-dimensional coordinates of each array element, the array element spacing and the time delay difference to calculate the coordinates of the target sound source, which is the partial discharge position; Assuming that the ultrasonic wave generated at the local discharge position propagates in the medium at a speed of c, and assuming that the spatial coordinates of the target sound source are (x, y, z), then according to the geometric relationship of sound wave propagation, we can obtain: , In the formula, x,y,z is the spatial coordinate of the target sound source; x i , y i , z i , i=1,2,…5, represents the three-dimensional coordinates of the i-th array element; c Indicates the propagation speed of ultrasonic waves; d i is the spatial distance from the target sound source to the i-th array element; τ i is the time delay difference between the ith array element and the array element at the origin of the coordinate system.

Claims

1. A Fabry-Perot interferometer ultrasonic sensor array positioning system, It is characterized in that It is composed of a Fabry-Perot laser, a fiber coupler, a fiber circulator, a fiber ultrasonic sensor array, a photoelectric detector, a data collector and a host terminal; along the transmission direction of the output light of the Fabry-Perot laser, the first ports of the fiber coupler and the fiber circulator are connected in sequence, the second port of the fiber circulator is connected to the fiber ultrasonic transmission array, and the third port is connected to the photoelectric detector, the photoelectric detector is electrically connected to the input end of the data collector, and the output end of the data collector is electrically connected to the host terminal; The fiber optic ultrasonic sensor array is used to detect ultrasonic signals during partial discharge and generate interference light intensity signals carrying ultrasonic characteristic information according to the vibration of the ultrasonic signal; the fiber optic ultrasonic sensor array includes a stainless steel probe, a stainless steel diaphragm and an optical fiber assembly, the stainless steel probe is penetrated with a plurality of jacks along the axial direction, a plurality of stainless steel diaphragms are fixedly bonded to one side of the stainless steel probe at the jack position, a plurality of optical fiber assemblies are fixedly installed to the jack on the side of the stainless steel probe away from the stainless steel diaphragm, and the insertion depth of the optical fiber assembly is less than the axial length of the stainless steel probe.

2. The ultrasonic sensor array positioning system of Fabry-Perot interferometer according to claim 1, It is characterized in that The optical fiber assembly includes a single-mode optical fiber, an optical fiber ceramic ferrule and a stainless steel sleeve. The single-mode optical fiber is fixedly connected to one end of the optical fiber ceramic ferrule. The single-mode optical fiber is externally sleeved with a stainless steel sleeve, and the stainless steel sleeve is fixedly connected to the optical fiber ceramic ferrule.

3. The ultrasonic sensor array positioning system of Fabry-Perot interferometer according to claim 2, It is characterized in that The end surface of the optical fiber ceramic ferrule away from the end of the single-mode optical fiber is parallel to and directly faces the inner surface of the stainless steel diaphragm.

4. The ultrasonic sensor array positioning system of Fabry-Perot interferometer according to claim 3, It is characterized in that The end face of the optical fiber ceramic ferrule away from one end of the single-mode optical fiber and the plane of the stainless steel diaphragm are perpendicular to the axial direction of the stainless steel probe.

5. The ultrasonic sensor array positioning system of Fabry-Perot interferometer according to claim 2, It is characterized in that The central axes of the single-mode optical fiber and the optical fiber ceramic ferrule pass through the center of the stainless steel diaphragm.

6. The ultrasonic sensor array positioning system of Fabry-Perot interferometer according to claim 1, It is characterized in that A plurality of optical fiber circulators and photoelectric detectors are provided, and the number of the optical fiber circulators is equal to the number of the jacks of the stainless steel probe.

7. A method for positioning an ultrasonic sensor array of a Fabry-Perot interferometer, applied to the ultrasonic sensor array positioning system of a Fabry-Perot interferometer according to any one of claims 1 to 6, It is characterized in that include: S1. According to the position and spacing of each array element of the optical fiber ultrasonic sensor array, select any array element as the coordinate origin to establish a three-dimensional rectangular coordinate system, and determine the three-dimensional coordinates of each array element; S2, obtaining the interference light intensity signal of each array element of the optical fiber ultrasonic sensor, and performing photoelectric conversion on the interference light intensity signal to obtain a voltage value; S3. Based on the voltage value of each array element, determine the occurrence time of the voltage value change of each array element; according to the occurrence time of each array element, determine the time delay difference between the coordinate origin array element and other array elements; S4. Based on the medium propagation speed of ultrasonic waves, a set of equations is constructed according to the three-dimensional coordinates of each array element, the array element spacing and the time delay difference to calculate the coordinates of the target sound source, which is the partial discharge position.

8. The ultrasonic sensor array positioning method of Fabry-Perot interferometer according to claim 7, It is characterized in that In S4, the equation group is constructed according to the three-dimensional coordinates of each array element, the array element spacing and the delay difference: ， In the formula, x,y,z is the spatial coordinate of the target sound source; x i , y i , z i , i=1,2,…5, represents the three-dimensional coordinates of the i-th array element; c Indicates the propagation speed of ultrasonic waves; d i is the spatial distance from the target sound source to the i-th array element; τ i is the time delay difference between the ith array element and the array element at the origin of the coordinate system.

Images