Device and method for detecting partial discharge in gas chamber of switch cabinet through closed-loop fluorescent optical fiber

Abstract

The invention discloses a device and a method for detecting partial discharge in a gas chamber of a switch cabinet by using a closed-loop fluorescent optical fiber, and the device comprises a closed-loop fluorescent optical fiber transmission module and a photomultiplier, and the closed-loop fluorescent optical fiber transmission module comprises a fluorescent optical fiber. The two ends of the fluorescent optical fiber are connected with one end of the first transmission optical fiber and one end of the second transmission optical fiber through the first optical fiber adapter and the second optical fiber adapter respectively, and the other ends of the first transmission optical fiber and the second transmission optical fiber are connected with the input end of the photomultiplier. According to the invention, a closed-loop fluorescent optical fiber detection mode is provided, all-in-one signal processing and conversion can be carried out through the light beam coupling device, and the sensitivity and accuracy of partial discharge detection are effectively improved; the invention provides closed-loop fluorescent optical fiber detection to improve the sensitivity of fluorescent optical fiber detection so as to compensate the defects of normal open-loop fluorescent optical fiber detection. Interference received by fluorescent optical fiber detection is smaller than that received by other devices, and the device is suitable for remote or weak-signal partial discharge detection in equipment such as a switch cabinet and a transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of partial discharge detection in power systems, and in particular to a device and method for detecting partial discharge inside a switch cabinet air chamber using a closed-loop fluorescent optical fiber. Background Art

[0002] With the modernization of power systems, the reliability and safety of power equipment are receiving increasing attention. Switchgear, as key control and protection equipment in power systems, is responsible for the distribution and conversion of electricity. The air chamber within the switchgear, as the core operating area of the equipment, withstands high voltages and complex current loads. While ensuring the normal operation of the equipment, it plays a vital role in the safety of the power system. However, as equipment ages and the operating environment changes, partial discharge within the air chamber has gradually become a significant factor affecting equipment safety and stability.

[0003] Partial discharge (PD) refers to electrical discharges that occur in a localized area within or on the surface of the insulating material of electrical equipment. It often occurs due to aging, contamination, structural defects, or flaws in the manufacturing process. When operating in a high-voltage environment within a gas chamber, if these defects exist on or within the insulator, the local electric field strength may be concentrated in these tiny areas, forming a high-voltage field and triggering PD. PD not only damages the insulating material, generating heat and noise, leading to material aging and performance degradation, but can also cause complete equipment failure and, in severe cases, even fire or system failure.

[0004] While traditional partial discharge detection methods, such as high-frequency current sensors and electric field sensors, can detect partial discharge to a certain extent, their susceptibility to external electromagnetic interference, difficulty in installation, and spatial limitations make the accuracy and reliability of detection results insufficient to meet the requirements for real-time monitoring of power equipment. In particular, under high voltage and complex environments, traditional sensors struggle to provide high-sensitivity, low-noise signal capture. Therefore, the power industry urgently needs a new, more sensitive, and stable partial discharge detection technology.

[0005] Fluorescent fiber optic detection technology emerged in this context. Fluorescent fiber optic detection technology captures and transmits optical signals generated during partial discharge (PD) through optical fibers, enabling real-time and accurate monitoring of PD without electromagnetic interference. Partial discharge is often accompanied by the release of optical signals with specific characteristics and spectral properties. Fluorescent fiber optic detection technology captures these optical signals using fluorescent materials embedded in the optical fibers, converts them into electrical signals via photoelectric converters, and then analyzes and processes them. Compared to traditional electrical signal acquisition methods, fluorescent fiber optic technology offers greater sensitivity and interference resistance, enabling real-time acquisition of discharge information and improving the monitoring accuracy of power equipment.

[0006] One of the advantages of this technology is its high resistance to interference. Because optical signals are not subject to interference from external electromagnetic fields during transmission, fluorescent fiber can operate stably in complex electromagnetic environments, making it particularly suitable for those with high voltages and strong electromagnetic interference. Furthermore, fluorescent fiber can achieve long-distance signal transmission and detect partial discharge signals independently of contact sensors, thus avoiding signal errors caused by poor contact or mechanical damage to traditional sensors.

[0007] However, despite its numerous advantages, fluorescent fiber optic detection technology still faces several challenges in practical application. First, traditional open-loop fluorescent fiber optic detection methods suffer from signal attenuation. The optical signal gradually attenuates during transmission, especially over long distances. This decrease in signal strength can lead to reduced detection sensitivity. Second, the location of the fluorescent fiber's photosensitivity point and the method of fiber installation also significantly influence detection accuracy and sensitivity. If the optical fiber photosensitivity points are not properly laid out, the partial discharge signal may not be captured in a timely manner, affecting the detection effect.

[0008] Therefore, improving the sensitivity and accuracy of fluorescent fiber optic detection and minimizing the effects of signal attenuation are key areas of current research. Through the adoption of new fiber optic materials, optimized fiber layouts, and improved signal processing algorithms, the sensitivity and stability of fluorescent fiber optic detection technology are continuously improving. These technological advances will significantly enhance the accuracy of partial discharge detection, thereby more effectively ensuring the safe operation of power equipment and the stability of power systems. Summary of the Invention

[0009] The purpose of the present invention is to make up for the defects of the existing technology in the partial discharge monitoring inside the switch cabinet air chamber, such as insufficient accuracy and susceptibility to interference, and to provide a device and method for detecting partial discharge inside the switch cabinet air chamber by using a closed-loop fluorescent optical fiber. The present invention utilizes light beam coupling technology to achieve all-in-one signal acquisition and transmission, effectively improving the accuracy and sensitivity of partial discharge detection. Through the optimized design of the closed-loop optical fiber structure, the ability to capture partial discharge signals is enhanced, and the influence of external electromagnetic interference is reduced, thereby significantly improving the limitations of traditional methods in the detection of partial discharge inside the switch cabinet air chamber. The application of this technology can not only accurately identify weak discharge signals, but also improve the reliability of power equipment status monitoring, providing a strong guarantee for the safe and stable operation of the power system.

[0010] The present invention is achieved through the following technical solutions:

[0011] A device for detecting partial discharge inside a switch cabinet air chamber using a closed-loop fluorescent optical fiber includes a closed-loop fluorescent optical fiber transmission module and a photomultiplier tube. The closed-loop fluorescent optical fiber transmission module includes a fluorescent optical fiber, the two ends of which are connected to one end of a transmission optical fiber 1 and one end of a transmission optical fiber 2 via an optical fiber adapter 1 and an optical fiber adapter 2, respectively. The other ends of the transmission optical fiber 1 and the transmission optical fiber 2 are connected to the input end of the photomultiplier tube.

[0012] The photomultiplier tube is a Hamamatsu R928 high-sensitivity photomultiplier tube.

[0013] The photomultiplier tube is also connected to a high-speed oscilloscope with a bandwidth of 500 MHz and a sampling rate of 5 GS / s.

[0014] The fluorescent optical fiber has a diameter of 1 mm and a length of 20 cm.

[0015] The transmission optical fiber 1 and the transmission optical fiber 2 are both low-loss optical fibers with a diameter of 3 mm and a length of 2 m.

[0016] A closed-loop fluorescent optical fiber method for detecting partial discharge inside a switchgear chamber comprises the following steps: using a fluorescent optical fiber to capture a light signal generated during partial discharge, exciting the fluorescent optical fiber to generate a fluorescent optical fiber signal, transmitting the fluorescent optical fiber signal into a photomultiplier tube via a first transmission optical fiber and a second transmission optical fiber at both ends of the fluorescent optical fiber, the photomultiplier tube converting the light signal into an electrical signal, and then analyzing and processing the electrical signal to detect partial discharge inside the switchgear chamber.

[0017] The steps are detailed as follows: Assume that the light intensity signal generated by the fluorescent optical fiber due to partial discharge inside the switch cabinet gas chamber is I, I=I1+I2, I1 represents the light intensity signal transmitted through one end of the fluorescent optical fiber, I2 represents the light intensity signal transmitted through the other end of the fluorescent optical fiber, the light intensity signal attenuates as the transmission length of the fluorescent optical fiber increases, the light intensity signal I1 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I1', and the light intensity signal I2 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I2'. The relationship is as follows:

[0018]

[0019]

[0020] d1 represents the distance that the light intensity signal I1 is transmitted through one end of the fluorescent fiber, d2 represents the distance that the light intensity signal I2 is transmitted through the other end of the fluorescent fiber, and μ is the linear attenuation coefficient of light in the medium;

[0021] The light intensity signal I1' obtained after being transmitted through the transmission optical fiber is I 1T The light intensity signal I2' is obtained after being transmitted through the transmission optical fiber 2. 2T , the relationship is as follows:

[0022] I 1T =η1I1' (3)

[0023] I 2T =η2I2' (4)

[0024] Where η1 and η2 represent the transmission efficiency from the fluorescent fiber to the transmission fiber 1 and the transmission fiber 2, respectively;

[0025] Light intensity signal I 1T and light intensity signal I 2T The light is input into the photomultiplier tube, which converts the received light signal into an electrical signal to obtain the total signal S. The expression of signal S is as follows:

[0026] S∝β T a1I 1T +β T a2I 2T (5)

[0027] Among them, β T is the photomultiplier tube conversion coefficient, α1 and α2 represent the coupling coefficients between the transmission fiber 1 and the transmission fiber 2 and the photomultiplier tube, respectively;

[0028] The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of discharge times and average amplitude.

[0029] The transmission efficiency η1 of the transmission optical fiber 1 is calculated as follows:

[0030]

[0031] Where NA1 and NA2 represent the numerical apertures of the fluorescent fiber and transmission fiber 1, respectively, which determine the incident and transmission angles of light; D1 and D2 represent the core diameters of the fluorescent fiber and transmission fiber 1, respectively;

[0032] The transmission efficiency η2 of the second transmission optical fiber is calculated as follows:

[0033]

[0034] Where NA3 represents the numerical aperture of the second transmission optical fiber; D3 represents the core diameter of the second transmission optical fiber.

[0035] The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of the number of discharges and the average amplitude, specifically as follows: first, the signal S is converted to the frequency domain through a fast Fourier transform, and low-frequency noise is suppressed using digital filtering technology; then, a high-quality time domain signal is reconstructed through an inverse Fourier transform; then, an adaptive threshold and minimum interval parameters are set to accurately identify independent discharge events; and finally, the characteristic indicators of the number of discharges and the average amplitude are extracted.

[0036] The photomultiplier tube processes and analyzes the signal S to obtain the characteristic indicators of discharge times and average amplitude. The calculation process is as follows: First, the original time domain signal S(t) is converted to the frequency domain through fast Fourier transform to obtain S(f)=FFT{S(t)}, and a digital filter H(f) is designed to suppress low-frequency noise. The filtered frequency domain signal S filtered (f)=S(f)H(f), and then reconstruct the high-quality time domain signal S through inverse fast Fourier transform processed (t) = IFFT{S filtered (f)}; Then, by calculating the sliding window statistical characteristics of the signal, the adaptive threshold is set as T(t) = μ(t) + kσ(t), where T(t) represents the adaptive threshold, the adaptive threshold changes with time t, μ(t) represents the mean of the signal in the sliding window, σ(t) represents the standard deviation of the signal in the sliding window, k represents the proportional coefficient, and the minimum discharge event interval Δt is set. min , ensuring that adjacent discharge pulses are not misjudged as the same event; then, traverse the processed signal S processed (t), according to Count the number of independent discharge events exceeding the threshold, N, where M represents the total number of sampling points in the time series, (t i ) represents the timestamp of the i-th sampling point, event_detected}(t i )) represents the event detection function, which is used to determine the time (t i) whether a discharge event occurs; finally, for each identified discharge event j, calculate its peak amplitude A j =max(S processed (t)|t∈event_window j ), where S processed (t) represents the processed signal, event_window represents the event window, which is a time interval used to define the time range occupied by a specific event, and then through Calculate the average amplitude of all discharge events .

[0037] The advantages of the present invention are: (1) the present invention proposes a closed-loop fluorescent fiber optic detection method, which can perform all-in-one signal processing and conversion through a beam coupling device, effectively improving the sensitivity and accuracy of partial discharge detection;

[0038] (2) The present invention proposes closed-loop fluorescent fiber detection to improve the sensitivity of fluorescent fiber detection to compensate for the shortcomings of normal open-loop fluorescent fiber detection;

[0039] (3) The present invention accurately extracts partial discharge features by fusing and analyzing different defect signals, especially processing early and weak signals and multi-signal cross-validation;

[0040] (4) The present invention captures fault signals earlier and, combined with multi-dimensional data analysis, can accurately locate the discharge position, facilitating timely maintenance and repair.

[0041] (5) The present invention uses fluorescent optical fiber to detect partial discharge. When partial discharge occurs, it will generate optical signals, which can ensure that the signals can be effectively captured, thereby improving the detection coverage;

[0042] (6) The interference received by the fluorescent fiber detection in the present invention is relatively small compared with other methods, and is suitable for long-distance or weak signal partial discharge detection in equipment such as switch cabinets and transformers.

[0043] (7) The present invention is highly efficient and can determine the intensity and nature of partial discharges in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of an open-loop fluorescent optical fiber detection device in the prior art;

[0045] Figure 2 This is a structural diagram of a device for detecting partial discharge inside a switch cabinet air chamber using a closed-loop fluorescent optical fiber according to the present invention;

[0046] Figure 3 Schematic diagram of the defect structure inside the air chamber;

[0047] Figure 4 This is a schematic diagram of partial discharge detection inside the switchgear gas chamber;

[0048] Figure 5 Comparison diagram of open-loop and closed-loop fluorescent fiber ( Figure 5 (a) is a closed-loop fluorescent fiber; Figure 5 (b) is an open-loop fluorescent fiber). DETAILED DESCRIPTION

[0049] Regarding the detection of partial discharge inside the switchgear gas chamber, we proposed and used a closed-loop fluorescent fiber optic detection method to improve the inaccurate and insensitive detection of partial discharge inside the switchgear gas chamber and improve the overall operating performance of the power system.

[0050] Fluorescent fiber optic detection technology is an emerging method for partial discharge (PD) monitoring. Leveraging the high sensitivity and electromagnetic interference resistance of fiber optic sensors, it enables real-time monitoring of partial discharge (PD) activity within power equipment. Its principle is based on the properties of photosensitive fluorescent materials: these materials undergo changes in the intensity or lifetime of their fluorescent signals in response to ultraviolet light, electric field fluctuations, or temperature increases generated by partial discharge. By analyzing the characteristics of these changing fluorescence signals, the occurrence of PD can be accurately determined, providing important evidence for assessing the condition of power equipment. During PD, the insulating medium is subjected to high electric fields, releasing ultraviolet light and localized heat, while also experiencing changes in the electric field. When a fluorescent fiber optic sensor is placed near the device under test, the fluorescent material is sensitive to these changes and responds as changes in the intensity, wavelength, or lifetime of the fluorescent signal. Using spectral analysis or time-resolved techniques, the characteristics of these signals can be extracted for further analysis of the intensity, frequency, and location of the PD. Fluorescent fiber optic detection offers the advantages of non-contact and remote monitoring, making it particularly suitable for PD detection in power equipment such as high-voltage cables, transformers, and gas-insulated switchgear (GIS).

[0051] The attenuation of fluorescent fiber signals is not only affected by scattering loss and coupling efficiency, but is also closely related to the characteristics of the excitation source, the optical response characteristics of the fiber, and the performance of the detector. The attenuation process of the fluorescence signal can be mathematically characterized by the following equation.

[0052]

[0053] Where E0(t') represents the pulse intensity of the excitation source at time t', which determines the initial signal energy entering the optical fiber. When the light signal propagates in the optical fiber, it excites the internal fluorescent molecules, thereby generating a fluorescent signal, whose response characteristics are given by I i (t-t') description. g i(t') is the instrument response function, which primarily reflects factors such as detector time resolution, timing errors, and delays or noise introduced by electronic components, significantly impacting the quality of the final recorded signal. By performing a convolution operation on these factors, the attenuation mechanism of the fluorescence signal in the optical fiber can be comprehensively characterized. In practical applications, the attenuation of the fluorescence signal is affected by both the properties of the optical fiber material and external factors such as the excitation source intensity and the detector response characteristics. The final detected signal intensity is the result of the interaction of these factors. This convolution formula provides a method for systematically analyzing these influencing factors, contributing to a more comprehensive understanding of the transmission and attenuation of fluorescence fiber signals.

[0054] While optical power loss in transmission fibers is negligible, fluorescence signals inevitably experience transmission loss (approximately 300 dB / km) when transmitted through fluorescent fibers, limiting their usable length. The power attenuation caused by this loss is defined as follows.

[0055] A(λ)=a(λ)·L=-10lg(P0 / P i )

[0056] Where α(λ) represents the wavelength-dependent attenuation coefficient, L is the probe length, P0 and Pi correspond to the output and input optical powers, respectively. The mathematical expression for the transmission efficiency η is as follows.

[0057] η=P0 / P i

[0058] In this system, we innovatively adopted a closed-loop fluorescent fiber optic sensing architecture. Compared with the traditional single-ended output open-loop structure, this design uses fiber fusion technology to efficiently fuse two fluorescent fibers, achieving an optimized combination of dual-end signal acquisition and single-end output, significantly improving the system sensitivity. Specifically, the closed-loop structure uses precise beam coupling technology to enable both ends of the fluorescent fiber to receive the light signal generated by partial discharge, and ultimately couple it into a single-channel output. This design increases the signal sensitivity by about 40% compared to traditional solutions. The core innovation of this system lies in the use of high-precision fiber fusion technology to seamlessly connect the two fluorescent fibers with the transmission fiber. The transmission fiber efficiently converges the dual-channel signals to the photomultiplier tube (PMT) through a fiber optic adapter. This unique dual-channel signal fusion design not only optimizes the signal transmission path, but also significantly enhances the detection capability of weak partial discharge signals through the signal superposition effect. The details are as follows:

[0059] like Figure 2As shown, a closed-loop fluorescent fiber optic device for detecting partial discharge inside the air chamber of a switch cabinet includes a closed-loop fluorescent fiber optic transmission module and a photomultiplier tube 1. The closed-loop fluorescent fiber optic transmission module includes a fluorescent fiber 2. The two ends of the fluorescent fiber 2 are respectively connected to one end of a transmission fiber 1 5 and one end of a transmission fiber 2 6 via a fiber optic adapter 1 3 and a fiber optic adapter 2 4. The other ends of the transmission fiber 1 5 and the transmission fiber 2 6 are connected to the input end of the photomultiplier tube 1.

[0060] The photomultiplier tube 1 is a Hamamatsu R928 high-sensitivity photomultiplier tube.

[0061] The photomultiplier tube 1 is also connected to a high-speed oscilloscope with a bandwidth of 500 MHz and a sampling rate of 5 GS / s.

[0062] The fluorescent optical fiber 2 has a diameter of 1 mm and a length of 20 cm.

[0063] Transmission optical fiber 1 5 and transmission optical fiber 2 6 can use the same optical fiber or different optical fibers. In this embodiment, transmission optical fiber 1 5 and transmission optical fiber 2 6 use the same optical fiber. Both transmission optical fiber 1 5 and transmission optical fiber 2 6 use low-loss optical fibers with a diameter of 3 mm and a length of 2 m.

[0064] A closed-loop fluorescent optical fiber method for detecting partial discharge inside a switchgear chamber comprises the following steps: using a fluorescent optical fiber to capture a light signal generated during partial discharge, exciting the fluorescent optical fiber to generate a fluorescent optical fiber signal, transmitting the fluorescent optical fiber signal into a photomultiplier tube via a first transmission optical fiber and a second transmission optical fiber at both ends of the fluorescent optical fiber, the photomultiplier tube converting the light signal into an electrical signal, and then analyzing and processing the electrical signal to detect partial discharge inside the switchgear chamber.

[0065] The steps are detailed as follows: Assume that the light intensity signal generated by the fluorescent optical fiber due to partial discharge inside the switch cabinet gas chamber is I, I=I1+I2, I1 represents the light intensity signal transmitted through one end of the fluorescent optical fiber, I2 represents the light intensity signal transmitted through the other end of the fluorescent optical fiber, the light intensity signal attenuates as the transmission length of the fluorescent optical fiber increases, the light intensity signal I1 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I1', and the light intensity signal I2 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I2'. The relationship is as follows:

[0066]

[0067]

[0068] d1 represents the distance that the light intensity signal I1 is transmitted through one end of the fluorescent fiber, d2 represents the distance that the light intensity signal I2 is transmitted through the other end of the fluorescent fiber, and μ is the linear attenuation coefficient of light in the medium;

[0069] The light intensity signal I1' obtained after being transmitted through the transmission optical fiber is I 1T The light intensity signal I2' is obtained after being transmitted through the transmission optical fiber 2. 2T , the relationship is as follows:

[0070] I 1T =η1I1' (3)

[0071] I 2T =η2I2' (4)

[0072] Where η1 and η2 represent the transmission efficiency from the fluorescent fiber to the transmission fiber 1 and the transmission fiber 2, respectively;

[0073] Light intensity signal I 1T and light intensity signal I 2T The light is input into the photomultiplier tube, which converts the received light signal into an electrical signal to obtain the total signal S. The expression of signal S is as follows:

[0074] S∝β T a1I 1T +β T a2I 2T (5)

[0075] Among them, β T is the photomultiplier tube conversion coefficient, α1 and α2 represent the coupling coefficients between the transmission fiber 1 and the transmission fiber 2 and the photomultiplier tube respectively; compared with the open-loop structure (such as Figure 1 As shown), the closed-loop structure additionally introduces β T α2I 2T This theoretically proves that the optical fiber sensing system under the closed-loop configuration should have stronger signal output capability.

[0076] The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of discharge times and average amplitude.

[0077] The transmission efficiency η1 of the transmission optical fiber 1 is calculated as follows:

[0078]

[0079] Where NA1 and NA2 represent the numerical apertures of the fluorescent fiber and transmission fiber 1, respectively, which determine the incident and transmission angles of light; D1 and D2 represent the core diameters of the fluorescent fiber and transmission fiber 1, respectively;

[0080] The transmission efficiency η2 of the second transmission optical fiber is calculated as follows:

[0081]

[0082] Where NA3 represents the numerical aperture of the second transmission optical fiber; D3 represents the core diameter of the second transmission optical fiber.

[0083] The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of the number of discharges and the average amplitude, specifically as follows: first, the signal S is converted to the frequency domain through a fast Fourier transform, and low-frequency noise is suppressed using digital filtering technology; then, a high-quality time domain signal is reconstructed through an inverse Fourier transform; then, an adaptive threshold and minimum interval parameters are set to accurately identify independent discharge events; and finally, the characteristic indicators of the number of discharges and the average amplitude are extracted.

[0084] The photomultiplier tube processes and analyzes the signal S to obtain the characteristic indicators of discharge times and average amplitude. The calculation process is as follows: First, the original time domain signal S(t) is converted to the frequency domain through fast Fourier transform to obtain S(f)=FFT{S(t)}, and a digital filter H(f) is designed to suppress low-frequency noise. The filtered frequency domain signal S filtered (f)=S(f)H(f), and then reconstruct the high-quality time domain signal S through inverse fast Fourier transform processed (t) = IFFT{S filtered (f)}; Then, by calculating the sliding window statistical characteristics of the signal, the adaptive threshold is set as T(t) = μ(t) + kσ(t), where T(t) represents the adaptive threshold, the adaptive threshold changes with time t, μ(t) represents the mean of the signal in the sliding window, σ(t) represents the standard deviation of the signal in the sliding window, k represents the proportional coefficient, and the minimum discharge event interval Δt is set. min , ensuring that adjacent discharge pulses are not misjudged as the same event; then, traverse the processed signal S processed (t), according to Count the number of independent discharge events exceeding the threshold, N, where M represents the total number of sampling points in the time series, (t i ) represents the timestamp of the i-th sampling point, event_detected}(t i )) represents the event detection function, which is used to determine the time (t i ) whether a discharge event occurs; finally, for each identified discharge event j, calculate its peak amplitude A j =max(S processed (t)|t∈event_window j ), where S processed (t) represents the processed signal, event_window represents the event window, which is a time interval used to define the time range occupied by a specific event, and then through Calculate the average amplitude of all discharge events .

[0085] The signal processing link of the present invention uses high-sensitivity PMT such as Hamamatsu R928, whose multi-stage dynode structure can amplify the photon signal by 10 6 The system, combined with a high-speed oscilloscope with a 500MHz bandwidth and 5GS / s sampling rate, can accurately capture nanosecond-level partial discharge transient signals. Experimental data shows that this closed-loop system improves the signal-to-noise ratio for pC-level partial discharge detection by 35%, fully demonstrating the superiority of the dual-terminal signal fusion design.

[0086] By combining advanced data processing algorithms, characteristic patterns of partial discharge can be further extracted, improving the accuracy of fault diagnosis. With its high sensitivity, anti-interference capabilities, and non-contact detection characteristics, fluorescent fiber optic detection technology has shown broad application prospects in power systems, especially in partial discharge monitoring of high-voltage cables, GIS, and transformers, providing reliable protection for the safe and stable operation of power equipment.

[0087] The present invention is applied to the gas chamber of a switch cabinet, and experiments are conducted to verify the feasibility of the present invention, as follows: Figure 3 As shown. Create fine burrs 8 on the metal parts inside the air chamber. These burrs need to be fine enough to simulate the irregular surfaces encountered in actual operation. Slightly loosen the bolts 7, contacts, or connectors inside the air chamber. Ensure that the connection is still in contact, but not tight, to simulate a loose condition. For the contact parts of the busbar or terminal, a certain degree of contact loss can be artificially created. For example, slightly lift or slightly offset the contact surface to simulate poor contact caused by loosening. The loosening operation must be carried out with care to ensure that it does not cause complete separation.

[0088] like Figure 4 As shown, the constructed partial discharge detection experimental platform primarily relies on a voltage regulator 9 to control the transformer to provide high voltage, and transmits the high-voltage signal to the detection circuit via coupling capacitors and protective resistors. The detection circuit consists of a fluorescent fiber, a transmission fiber, and a PMT. The fluorescent fiber and the transmission fiber work together to efficiently transmit the optical signal generated by the partial discharge to the photomultiplier tube. The photomultiplier tube converts the received optical signal into an electrical signal and transmits it to an oscilloscope for signal processing and waveform analysis. The high-voltage power supply for this experiment has a rated voltage of 50kV, and the initial voltage required for the experiment is adjusted by the voltage regulator. The signal acquisition section uses a 5-series oscilloscope. Using an all-in-one beam coupling device combined with a photoelectric converter, the optical signal acquired by the fluorescent fiber is converted into an electrical signal. The partial discharge signal is ultimately displayed in real time on the oscilloscope, enabling precise detection and analysis.

[0089] In order to intuitively evaluate the detection effect of fluorescent fiber optic detection on partial discharge inside the switchgear gas chamber, a specific experiment will be carried out. The specific test steps are as follows.

[0090] (1) Ensure that the fluorescent fiber optic sensor can work normally and the detection environment is free of interference, and ensure that the staff wear appropriate safety equipment and follow the operating procedures of high-voltage equipment;

[0091] (2) Install the closed-loop fluorescent optical fiber at the location where partial discharge occurs, and create burrs and loose defects inside the air chamber;

[0092] (3) Turn on the power supply and use the voltage regulator to change the output voltage until a partial discharge signal appears on the oscilloscope;

[0093] (4) Observe the oscilloscope to see if there is a similar partial discharge signal, perform spectrum analysis on the electrical signal, identify the frequency characteristics of the partial discharge, analyze the signal waveform and amplitude, and determine the intensity and location of the partial discharge.

[0094] The present invention systematically evaluates the performance differences between open-loop and closed-loop fluorescent fiber systems in partial discharge detection through a comparative experimental system. The experiment innovatively uses high-precision fiber fusion technology to efficiently fuse two fluorescent fibers into a closed-loop detection circuit, achieving a breakthrough improvement in signal acquisition capabilities. The collected signals were systematically analyzed using a data processing program developed based on Matlab. Its core processing flow includes: first, converting the time domain signal to the frequency domain through fast Fourier transform (FFT), and using digital filtering technology to effectively suppress low-frequency noise; then reconstructing the high-quality time domain signal through inverse Fourier transform (IFFT); then setting adaptive thresholds and minimum interval parameters to accurately identify independent discharge events; and finally extracting key characteristic indicators such as the number of discharges and average amplitude.

[0095] The experimental results show that (such as Figure 5 As shown in the figure, thanks to innovative dual-fiber fusion technology and a closed-loop signal acquisition architecture, the closed-loop system's detection sensitivity is significantly improved. Specifically: 1) Dual-channel signal fusion, achieved through a precision fusion process, increases the effective signal acquisition area by 200%; 2) The closed-loop design's optimized optical path improves signal transmission efficiency by 150%; 3) The resulting system's average amplitude detection capability is improved by 300% compared to traditional open-loop systems, and its maximum amplitude detection capability is increased by 280%. These data fully demonstrate the superior signal enhancement performance of the proposed closed-loop fluorescent fiber detection method, providing a new technical solution for partial discharge monitoring in power equipment.

Claims

1. A closed-loop fluorescent optical fiber device for detecting partial discharge inside a switchgear chamber, characterized in that: The invention comprises a closed-loop fluorescent fiber optic transmission module and a photomultiplier tube. The closed-loop fluorescent fiber optic transmission module comprises a fluorescent fiber. The two ends of the fluorescent fiber optic are respectively connected to one end of the transmission fiber 1 and the transmission fiber 2 through the optical fiber adapter 1 and the optical fiber adapter 2. The other ends of the transmission fiber 1 and the transmission fiber 2 are connected to the input end of the photomultiplier tube.

2. The closed-loop fluorescent optical fiber device for detecting partial discharge inside a switch cabinet air chamber according to claim 1, characterized in that: The photomultiplier tube is a Hamamatsu R928 high-sensitivity photomultiplier tube.

3. The closed-loop fluorescent optical fiber device for detecting partial discharge inside a switch cabinet air chamber according to claim 1, characterized in that: The photomultiplier tube is also connected to a high-speed oscilloscope with a bandwidth of 500 MHz and a sampling rate of 5 GS / s.

4. The closed-loop fluorescent optical fiber device for detecting partial discharge inside a switch cabinet air chamber according to claim 1, characterized in that: The fluorescent optical fiber has a diameter of 1 mm and a length of 20 cm.

5. The closed-loop fluorescent optical fiber device for detecting partial discharge inside a switch cabinet air chamber according to claim 1, characterized in that: The transmission optical fiber 1 and the transmission optical fiber 2 are both low-loss optical fibers with a diameter of 3 mm and a length of 2 m.

6. A closed-loop fluorescent optical fiber method for detecting partial discharge inside a switchgear chamber, characterized in that: Specifically, the method includes the following steps: using fluorescent optical fiber to capture the light signal generated during the partial discharge process, exciting the fluorescent optical fiber to generate a fluorescent optical fiber signal, transmitting the fluorescent optical fiber signal into the photomultiplier tube through the transmission optical fiber 1 and the transmission optical fiber 2 at both ends of the fluorescent optical fiber respectively, the photomultiplier tube converts the light signal into an electrical signal, and then analyzes and processes the electrical signal to realize the detection of partial discharge inside the gas chamber of the switch cabinet.

7. The method for detecting partial discharge inside the air chamber of a switch cabinet using a closed-loop fluorescent optical fiber according to claim 6, characterized in that: The steps are detailed as follows: Assume that the light intensity signal generated by the fluorescent optical fiber due to partial discharge inside the switch cabinet gas chamber is I, I=I1+I2, I1 represents the light intensity signal transmitted through one end of the fluorescent optical fiber, I2 represents the light intensity signal transmitted through the other end of the fluorescent optical fiber, the light intensity signal attenuates as the transmission length of the fluorescent optical fiber increases, the light intensity signal I1 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I1', and the light intensity signal I2 is transmitted through the fluorescent optical fiber to obtain the light intensity signal I2'. The relationship is as follows: d1 represents the distance that the light intensity signal I1 is transmitted through one end of the fluorescent fiber, d2 represents the distance that the light intensity signal I2 is transmitted through the other end of the fluorescent fiber, and μ is the linear attenuation coefficient of light in the medium; The light intensity signal I1' obtained after being transmitted through the transmission optical fiber is I 1T The light intensity signal I2' is obtained after being transmitted through the transmission optical fiber 2. 2T , the relationship is as follows: I 1T =η1I1' (3) I 2T =η2I2' (4) Where η1 and η2 represent the transmission efficiency from the fluorescent fiber to the transmission fiber 1 and the transmission fiber 2, respectively; Light intensity signal I 1T and light intensity signal I 2T The light is input into the photomultiplier tube, which converts the received light signal into an electrical signal to obtain the total signal S. The expression of signal S is as follows: S∝β T a1I 1T +β T a2I 2T (5) Among them, β T is the photomultiplier tube conversion coefficient, α1 and α2 represent the coupling coefficients between the transmission fiber 1 and the transmission fiber 2 and the photomultiplier tube, respectively; The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of discharge times and average amplitude.

8. The method for detecting partial discharge inside the air chamber of a switch cabinet using a closed-loop fluorescent optical fiber according to claim 7, characterized in that: The transmission efficiency η1 of the transmission optical fiber 1 is calculated as follows: Where NA1 and NA2 represent the numerical apertures of the fluorescent fiber and transmission fiber 1, respectively, which determine the incident and transmission angles of light; D1 and D2 represent the core diameters of the fluorescent fiber and transmission fiber 1, respectively; The transmission efficiency η2 of the second transmission optical fiber is calculated as follows: Where NA3 represents the numerical aperture of the second transmission optical fiber; D3 represents the core diameter of the second transmission optical fiber.

9. The method for detecting partial discharge inside the air chamber of a switch cabinet using a closed-loop fluorescent optical fiber according to claim 7, characterized in that: The photomultiplier tube processes and analyzes the signal S to obtain characteristic indicators of the number of discharges and the average amplitude, specifically as follows: first, the signal S is converted to the frequency domain through a fast Fourier transform, and low-frequency noise is suppressed using digital filtering technology; then, a high-quality time domain signal is reconstructed through an inverse Fourier transform; then, an adaptive threshold and minimum interval parameters are set to accurately identify independent discharge events; and finally, the characteristic indicators of the number of discharges and the average amplitude are extracted.

10. The method for detecting partial discharge inside the air chamber of a switch cabinet using a closed-loop fluorescent optical fiber according to claim 9, characterized in that: The photomultiplier tube processes and analyzes the signal S to obtain the characteristic indicators of discharge times and average amplitude. The calculation process is as follows: First, the original time domain signal S(t) is converted to the frequency domain through fast Fourier transform to obtain S(f)=FFT{S(t)}, and a digital filter H(f) is designed to suppress low-frequency noise. The filtered frequency domain signal S filtered (f)=S(f)H(f), and then reconstruct the high-quality time domain signal S through inverse fast Fourier transform processed (t) = IFFT{S filtered (f)}; Then, by calculating the sliding window statistical characteristics of the signal, the adaptive threshold is set as T(t) = μ(t) + kσ(t), where T(t) represents the adaptive threshold, the adaptive threshold changes with time t, μ(t) represents the mean of the signal in the sliding window, σ(t) represents the standard deviation of the signal in the sliding window, k represents the proportional coefficient, and the minimum discharge event interval Δt is set. min , ensuring that adjacent discharge pulses are not misjudged as the same event; then, traverse the processed signal S processed (t), according to Count the number of independent discharge events exceeding the threshold, N, where M represents the total number of sampling points in the time series, (t i ) represents the timestamp of the i-th sampling point, event_detected}(t i )) represents the event detection function, which is used to determine the time (t i ) whether a discharge event occurs; finally, for each identified discharge event j, calculate its peak amplitude A j =max(S processed (t)|t∈event_window j ), where S processed (t) represents the processed signal, event_window represents the event window, which is a time interval used to define the time range occupied by a specific event, and then through Calculate the average amplitude of all discharge events

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