GIS withstand voltage test breakdown positioning method and system based on distributed optical fibers

Abstract

The invention relates to the field of GIS withstand voltage test breakdown positioning, in particular to a GIS withstand voltage test breakdown positioning method and system based on distributed optical fibers. A continuous distributed optical fiber is linearly arranged along a main loop metal shell of a tested GIS, a laser light source continuously outputs optical pulse signals with preset power, frequency and pulse width to the starting end of the distributed optical fiber, and the principle that vibration generated by GIS breakdown can cause the change of the refractive index of the optical fiber so as to change the waveform of backscattering light is utilized. The photoelectric detection unit collects backscattered light in real time and performs coherent average noise reduction processing, and the signal processing unit timely discovers and extracts backscattered light signal waveform distortion points caused by GIS breakdown vibration through comparison on the basis of constructing backscattered light reference signals in a normal state. And finally, accurately reading a corresponding time unit through a fault point positioning module, and accurately calculating a GIS breakdown fault point. The method is suitable for GIS withstand voltage test breakdown positioning.

Description

Technical Field

[0001] The invention relates to the field of GIS (Gas Insulated Switchgear) withstand voltage test breakdown positioning, and in particular to a GIS withstand voltage test breakdown positioning method and system based on distributed optical fiber. Background Art

[0002] The AC withstand voltage test is used to check whether the internal insulation strength of GIS meets the standard requirements. It also helps to find defects such as internal foreign matter, poor conductor contact, abnormal mechanical vibration, etc. It is a major test to determine whether the GIS meets the conditions for commissioning. During the GIS withstand voltage test, breakdown failures caused by equipment defects often occur. In order to repair the equipment as quickly as possible, avoid repeated pressurization as much as possible, and effectively improve the test efficiency, it is very necessary to find the GIS breakdown point in a timely and accurate manner.

[0003] Over the past decade, various types of technologies and devices for GIS pressure withstand test breakdown locating have been researched and developed at home and abroad. Representative methods and devices include multi-point ultrasonic amplitude locating, multi-point vibration amplitude locating, multi-point ultrasonic time delay locating, acoustic and electrical combined locating, and multi-point acoustic signal locating. These methods have promoted the GIS pressure withstand test breakdown locating point search method from inefficient and extensive means such as "listening to the sound to identify the location", repeated pressurization after changing the state, detection of gas decomposition products of each gas chamber, and disassembly inspection of multiple gas chambers to scientific calculation and accurate positioning.

[0004] However, based on a large amount of field application experience, the existing ultrasonic amplitude positioning devices, multi-point vibration amplitude positioning devices, and multi-point acoustic signal positioning devices have low positioning accuracy, and there is a considerable possibility of misjudgment due to the oscillation superposition or refraction and reflection of the signal in the special tubular cavity structure of GIS. On the one hand, the multi-point ultrasonic time-delay positioning device and the acoustic-electric combined positioning device have complex principles, time-consuming layout, and high cost. On the other hand, the sensor layout has a great influence on the positioning results, and the uncertainty of the signal transmission path restricts the scientific and reasonable layout of sensors before the test, which may lead to positioning failure due to the sensor coverage range. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a GIS withstand voltage test breakdown positioning method and system based on distributed optical fiber, thereby improving the accuracy of GIS breakdown fault point calculation.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose. In the first aspect, the present invention provides a GIS withstand voltage test breakdown location method based on distributed optical fiber, comprising: S1, continuously outputting optical pulse signals of preset power, frequency and pulse width to distributed optical fibers through a laser light source, collecting backscattered light in real time and converting it into an electrical signal, and performing coherent averaging noise reduction processing on the collected backscattered light signal; S2, evenly divide the electrical signal converted from the backscattered light after noise reduction, select the maximum signal amplitude sampled during the signal amplitude corresponding to each time unit, complete the continuous signal discretization processing, and obtain a list of backscattered light signal amplitudes for each time unit; S3, starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, and taking the average of the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis to construct a backscattered light reference signal; S4. During the withstand voltage test, the backscattered light signal is continuously collected in real time. After a breakdown fault occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, and the list is compared with the backscattered light reference signal under a unified time axis. The waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted; S5. Extract a list of multiple backscattered light signal amplitudes after GIS breakdown, and compare them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the unified time axis. If it meets the breakdown vibration characteristics, it is determined that the waveform distortion is caused by the GIS breakdown fault; S6. Extract the maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault, and calculate the GIS position corresponding to the maximum waveform distortion point, which is the GIS breakdown fault point.

[0007] Furthermore, the method further comprises: Before the voltage test, the continuously distributed optical fiber is arranged in a straight line along the metal shell of the main circuit of the tested GIS. The continuously distributed optical fiber is in close contact with the metal shell. The laser light source is connected to the input end of the circulator, the isolation end of the circulator is connected to the starting end of the continuously distributed optical fiber, and the output end of the circulator is connected to the photoelectric detection unit.

[0008] Furthermore, the frequency of the optical pulse signal of the preset power satisfy , where c The speed of light is 3×10 8 m / s, is the refractive index of the distributed optical fiber used under normal conditions, is the straight length of the metal shell of the main circuit of the tested GIS, i.e. the total length of the continuously distributed optical fiber, and the pulse width of the optical pulse signal with the preset power W Should meet ,△ Lis the distance resolution, the power P Should meet , P R is the minimum backscattered light power that the photoelectric detection unit can identify, S L It is the comprehensive backscattering coefficient that takes into account the scattering coefficient, backscattering factor, and distance attenuation coefficient.

[0009] Furthermore, the coherent average noise reduction process is to add and average multiple groups of stable backscattered light under the same time axis. The signal-to-noise ratio (SNR) after noise reduction is expressed as: ; Where M is the number of backscattered light signals involved in the coherent average denoising process, is the average value of the amplitude coefficients of the backscattered light signals of group M participating in the coherent average denoising process, P r is the power of the backscattered light signal with unit amplitude, K is the total number of sampling points of a single backscattered light signal, and σ is the variance of the background noise of the M groups of backscattered light signals participating in the coherent average denoising process.

[0010] Furthermore, step S3 specifically includes: S301, starting from the initial signal, extract multiple groups of backscattered light signal amplitude lists, and perform discrete signal cross-correlation on a unified time axis R mn Analysis, the expression is: ; In the formula, R mn For the m The signal and n The cross-correlation of the signals, T i m For the m Signal No. i The amplitude per unit time, T i n For the n Signal No. i The amplitude per unit time, m ≤N, n ≤N; S302, until the cross-correlations of the extracted multiple groups of backscattered light signals are not less than the set value, it is determined that the initial state signal after the continuous distributed optical fiber is combined with the metal shell of the main circuit of the tested GIS is stable, and a reference signal is constructed; S303, under the same time axis, a list of multiple backscattered light amplitudes whose cross-correlations are not less than the set value is extracted, and then the average value of the amplitude in the same time unit is taken to construct a backscattered light reference signal. The amplitude expression of each time unit of the backscattered light reference signal is: ; Where, T rei is the backscattered light reference signal i The signal amplitude per time unit; S304: The constructed backscattered light reference signal is used as the initial signal for this voltage withstand test.

[0011] Furthermore, the waveform distortion rate is calculated as follows: ; In the formula, S B1i is the first backscattered light signal collected after breakdown. i The signal distortion rate per time unit, T i B1 is the first backscattered light signal collected after the breakdown i The signal amplitude per time unit.

[0012] Furthermore, the breakdown vibration characteristics specifically include: like Alarm value and , then it meets the breakdown vibration characteristics; In the formula, S Bmi The first m The backscattered light signal i The signal distortion rate per time unit, S Bni The first n The backscattered light signal i The signal distortion rate per time unit, m Greater than n and less than or equal to the number of lists of backscattered light signal amplitudes extracted after GIS breakdown.

[0013] Furthermore, the GIS position corresponding to the maximum waveform distortion point is calculated as follows: ; In the formula, L The calculated distance between the breakdown fault point and the starting end of the optical fiber is the fault breakdown point position. t i is the time unit corresponding to the point of maximum waveform distortion of the backscattered light signal, t N is the Nth backscattered light signal time unit divided.

[0014] In a second aspect, the present invention provides a GIS withstand voltage test breakdown positioning system based on distributed optical fiber, which is used to implement the above-mentioned GIS withstand voltage test breakdown positioning method based on distributed optical fiber, and the system comprises: The optical pulse generation module continuously outputs optical pulse signals of preset power, frequency and pulse width to the distributed optical fiber through a laser light source; The signal acquisition module collects the backscattered light in real time through the photoelectric detection unit and converts it into an electrical signal, and at the same time performs coherent averaging noise reduction processing on the collected backscattered light signal; The signal processing module evenly divides the backscattered light conversion signal after noise reduction, selects the maximum signal amplitude sampled during the signal amplitude corresponding to each time unit, completes the continuous signal discretization processing, and obtains the backscattered light signal amplitude list of each time unit; Starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, and constructing a backscattered light reference signal after averaging the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis; During the withstand voltage test, the backscattered light is continuously collected in real time. After a breakdown fault occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, which is compared with the backscattered light reference signal under a unified time axis, the waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted; The fault location module extracts a list of multiple backscattered light signal amplitudes after GIS breakdown, and compares them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the same time axis. If it meets the breakdown vibration characteristics, it is judged to be the waveform distortion caused by the GIS breakdown fault. The maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault is extracted, and the GIS position corresponding to the maximum waveform distortion point is calculated, and the position is the GIS breakdown fault point.

[0015] Furthermore, the waveform distortion rate alarm value set by the signal processing module is used to construct the backscattered light reference signal, and then the GIS metal shell is vibrated by knocking and the vibration sensor is used to detect the vibration value of the GIS metal shell, and the vibration acceleration is calculated to be 5m / s. 2 The waveform distortion rate of the backscattered light per unit time corresponding to the vibration position is set as the waveform distortion rate alarm value during this GIS withstand voltage test.

[0016] The beneficial effects of the present invention are: The present invention overcomes the problems of existing GIS withstand voltage test breakdown positioning methods, such as either too many points, low positioning accuracy, and susceptibility to interference leading to positioning errors, or complex principles, high costs, and point layout being greatly affected by GIS structure constraints on positioning results. Continuous distributed optical fibers are arranged in a straight line on the surface of the metal shell of the GIS main circuit, and a laser light source continuously outputs an optical pulse signal to the starting end of the distributed optical fiber. A photoelectric detection unit collects backscattered light signals in real time. The vibration generated by GIS breakdown causes the refractive index of the optical fiber to change, thereby changing the backscattered light waveform. The distortion points of the backscattered light signal waveform caused by the GIS breakdown vibration are timely discovered and extracted through comparison, the corresponding time units are accurately read, and the GIS breakdown fault points are accurately calculated.

[0017] The present invention presets the optimal optical pulse signal power, frequency, and pulse width according to actual working conditions before each GIS withstand voltage test, so as to obtain the best backscattered light resolution, anti-interference ability and positioning accuracy, collects the backscattered light in real time and performs coherent averaging noise reduction processing to further improve the signal-to-noise ratio of the backscattered light signal. On the basis of constructing a backscattered light reference signal under normal conditions, the waveform distortion rate alarm value is scientifically set through vibration calibration, and the maximum waveform distortion point of the backscattered light signal when the GIS withstand voltage test is broken down is extracted, so as to perform accurate positioning calculation.

[0018] The present invention has simple layout, easy debugging and clear judgment criteria. The GIS breakdown positioning accuracy does not exceed 1 meter. The breakdown time is used to eliminate the interference caused by external force hitting the GIS metal shell. The positioning result has high credibility. The sampling rate required for the system to collect backscattered light signals is not high, and the computing power required for signal processing is not high. The price of optical fiber used as a sensor and signal transmission cable is relatively low, and the total length is usually no more than 1 km, taking into account both engineering application effect and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of a GIS withstand voltage test breakdown location method based on distributed optical fiber provided in an embodiment of the present invention; Figure 2 Schematic diagram of the backscattered light reference signal of the distributed optical fiber and the backscattered light signal affected by the vibration of the GIS shell; Figure 3 It is a structural block diagram of a GIS withstand voltage test breakdown positioning system based on distributed optical fiber provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0021] The present invention provides a GIS withstand voltage test breakdown positioning method based on distributed optical fiber, such as Figure 1 As shown, specifically including: S1. Before the withstand voltage test, the continuously distributed optical fiber is arranged in a straight line along the metal shell of the main circuit of the tested GIS. The continuously distributed optical fiber is in close contact with the metal shell. The laser light source is connected to the input end of the circulator, the isolation end of the circulator is connected to the starting end of the continuously distributed optical fiber, and the output end of the circulator is connected to the photoelectric detection unit.

[0022] S2. The laser light source continuously outputs optical pulse signals of preset power, frequency, and pulse width to the distributed optical fiber through a circulator. The photoelectric detection unit collects the backscattered light in real time at a sampling rate of not less than 200 MS / s through the output end of the circulator and converts it into an electrical signal. At the same time, the collected backscattered light signal is subjected to coherent averaging noise reduction processing.

[0023] The optical pulse signal with preset power, frequency and pulse width shall meet the comprehensive requirements of anti-interference capability, resolution and positioning accuracy. satisfy , where c The speed of light is 3×10 8 m / s, is the refractive index of the distributed optical fiber used under normal conditions, is the straight length of the metal shell of the main circuit of the tested GIS, i.e. the total length of the continuously distributed optical fiber, and the pulse width of the optical pulse signal with the preset power W Should meet ,△ L is the distance resolution, the power P Should meet , P R is the minimum backscattered light power that the photoelectric detection unit can identify, S L It is the comprehensive backscattering coefficient that takes into account the scattering coefficient, backscattering factor, and distance attenuation coefficient.

[0024] Specifically, the coherent average noise reduction process is to add and average multiple groups of stable backscattered light under the same time axis. The signal-to-noise ratio (SNR) after noise reduction is expressed as: ; Where M is the number of backscattered light signals involved in the coherent average denoising process, is the average value of the amplitude coefficients of the backscattered light signals of group M participating in the coherent average denoising process, P ris the power of the backscattered light signal with unit amplitude, K is the total number of sampling points of a single backscattered light signal, and σ is the variance of the background noise of the M groups of backscattered light signals participating in the coherent average denoising process.

[0025] S3, the backscattered light conversion signal after noise reduction is evenly divided into time units not greater than 10 ns, and the signal amplitude corresponding to each time unit is selected from the maximum signal amplitude sampled during the period, so as to complete the continuous signal discretization processing, and the N backscattered light signal time units divided are t ={ t 1, t 2, ..., t i , t i+1 , ..., t N}, the list of backscattered light signal amplitudes for each time unit T = {T1, T2, ..., T i , T i+1 , ..., T N}.

[0026] S4, starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, taking the average of the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis to construct a backscattered light reference signal T re ={T re1 , T re2 , ..., T rei , T re（i+1） , ..., T reN}; Specifically include: S401, starting from the initial signal, extract multiple groups of backscattered light signal amplitude lists, and perform discrete signal cross-correlation on a unified time axis R mn Analysis, the expression is: ; In the formula, R mn For the m The signal and n The cross-correlation of the signals, T i m For the m Signal No. i The amplitude per unit time, T i n For the n Signal No. i The amplitude per unit time, m ≤N, n≤N; S402, until the cross-correlations of the extracted multiple groups of backscattered light signals are not less than the set value, it is determined that the initial state signal after the continuous distributed optical fiber is combined with the metal shell of the main circuit of the tested GIS is stable, and a reference signal is constructed; S403, under the same time axis, taking the average value of the multiple groups of backscattered light amplitude lists whose cross-correlations are not less than the set value in the same time unit amplitude to construct a backscattered light reference signal T re ={T re1 , T re2 , ..., T rei , T re（i+1） , ..., T reN}, the amplitude expression of the backscattered light reference signal at each time unit is: ; Where, T rei is the backscattered light reference signal i The signal amplitude per time unit; S404: The constructed backscattered light reference signal is used as the initial signal of this withstand voltage test. When the backscattered light signal monitored in real time is not affected by severe external vibration, the backscattered light reference signal T re resemblance.

[0027] S5. During the voltage test, the backscattered light is continuously collected in real time. After a breakdown failure occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, which is compared with the backscattered light reference signal on a unified time axis, the waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted.

[0028] Specifically, the waveform distortion rate is calculated as follows: ; In the formula, S B1i is the first backscattered light signal collected after breakdown. i The signal distortion rate per time unit, T i B1 is the first backscattered light signal collected after the breakdown i The signal amplitude per time unit.

[0029] S6. Extract a list of at least D backscattered light signal amplitudes after GIS breakdown, and compare them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the same time axis. If it meets the breakdown vibration characteristics, it is determined to be the waveform distortion caused by the GIS breakdown fault.

[0030] Specifically, the breakdown vibration characteristics include: like Alarm value and , then it meets the breakdown vibration characteristics; In the formula, S Bmi The first m The backscattered light signal i The signal distortion rate per time unit, S Bni The first n The backscattered light signal i The signal distortion rate per time unit, m Greater than n and less than or equal to the number of lists of backscattered light signal amplitudes extracted after GIS breakdown.

[0031] S7. Extract the maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault, and calculate the GIS position corresponding to the maximum waveform distortion point. The position is the GIS breakdown fault point.

[0032] Specifically, the GIS position corresponding to the maximum waveform distortion point is calculated as follows: ; In the formula, L The calculated distance between the breakdown fault point and the starting end of the optical fiber is the fault breakdown point position. t i It is the time unit corresponding to the point of maximum waveform distortion of the backscattered light signal.

[0033] like Figure 3 As shown, the present invention also provides a GIS withstand voltage test breakdown positioning system based on distributed optical fiber, the system comprising: The optical pulse generating module includes a laser light source and a circulator input end, which is used to continuously output an optical pulse signal of preset power, frequency and pulse width to the starting end of the continuous distributed optical fiber; based on the calculation according to the length of the distributed optical fiber, the optical pulse signal parameters such as power, frequency, pulse width, etc. should be comprehensively optimized and determined according to the actual conditions such as anti-interference ability, resolution, positioning accuracy, etc. during the debugging of the positioning system.

[0034] The optical pulse generation module continuously outputs optical pulse signals of preset power, frequency and pulse width to the distributed optical fiber through a laser light source; The signal acquisition module collects the backscattered light in real time through the photoelectric detection unit and converts it into an electrical signal, and at the same time performs coherent averaging noise reduction processing on the collected backscattered light signal; The signal processing module evenly divides the backscattered light conversion signal after noise reduction, selects the maximum signal amplitude sampled during the signal amplitude corresponding to each time unit, completes the continuous signal discretization processing, and obtains the backscattered light signal amplitude list of each time unit; Starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, and constructing a backscattered light reference signal after averaging the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis; During the withstand voltage test, the backscattered light is continuously collected in real time. After a breakdown fault occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, which is compared with the backscattered light reference signal under a unified time axis, the waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted; The fault location module extracts a list of multiple backscattered light signal amplitudes after GIS breakdown, and compares them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the same time axis. If it meets the breakdown vibration characteristics, it is judged to be the waveform distortion caused by the GIS breakdown fault. The maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault is extracted, and the GIS position corresponding to the maximum waveform distortion point is calculated, and the position is the GIS breakdown fault point.

[0035] Specifically, the waveform distortion rate alarm value set by the signal processing module is used to construct the backscattered light reference signal, and then the GIS metal shell is vibrated by knocking and the vibration sensor is used to detect the vibration value of the GIS metal shell, and the vibration acceleration is calculated to be 5m / s. 2 The waveform distortion rate of the backscattered light per unit time corresponding to the vibration position is set as the waveform distortion rate alarm value during this GIS withstand voltage test. The distributed optical fiber backscattered light reference signal and the backscattered light signal affected by the GIS shell vibration are as follows: Figure 2 shown.

[0036] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A GIS withstand voltage test breakdown location method based on distributed optical fiber, characterized in that: include: S1, continuously outputting optical pulse signals of preset power, frequency and pulse width to distributed optical fibers through a laser light source, collecting backscattered light in real time and converting it into an electrical signal, and performing coherent averaging noise reduction processing on the collected backscattered light signal; S2, evenly divide the electrical signal converted from the backscattered light after noise reduction, select the maximum signal amplitude sampled during the signal amplitude corresponding to each time unit, complete the continuous signal discretization processing, and obtain a list of backscattered light signal amplitudes for each time unit; S3, starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, and taking the average of the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis to construct a backscattered light reference signal; S4. During the withstand voltage test, the backscattered light signal is continuously collected in real time. After a breakdown fault occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, and the list is compared with the backscattered light reference signal under a unified time axis. The waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted; S5. Extract a list of multiple backscattered light signal amplitudes after GIS breakdown, and compare them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the unified time axis. If it meets the breakdown vibration characteristics, it is determined that the waveform distortion is caused by the GIS breakdown fault; S6. Extract the maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault, and calculate the GIS position corresponding to the maximum waveform distortion point, which is the GIS breakdown fault point.

2. The GIS withstand voltage test breakdown location method based on distributed optical fiber according to claim 1 is characterized in that: The method further includes: Before the voltage test, the continuously distributed optical fiber is arranged in a straight line along the metal shell of the main circuit of the tested GIS. The continuously distributed optical fiber is in close contact with the metal shell. The laser light source is connected to the input end of the circulator, the isolation end of the circulator is connected to the starting end of the continuously distributed optical fiber, and the output end of the circulator is connected to the photoelectric detection unit.

3. The GIS withstand voltage test breakdown location method based on distributed optical fiber according to claim 1 is characterized in that: Frequency of optical pulse signal with preset power satisfy , where c The speed of light is 3×10 8 m / s, is the refractive index of the distributed optical fiber used under normal conditions, is the straight length of the metal shell of the main circuit of the tested GIS, i.e. the total length of the continuously distributed optical fiber, and the pulse width of the optical pulse signal with the preset power W Should meet ,△ L is the distance resolution, the power P Should meet , P R is the minimum backscattered light power that the photoelectric detection unit can identify, S L It is the comprehensive backscattering coefficient that takes into account the scattering coefficient, backscattering factor, and distance attenuation coefficient.

4. The GIS withstand voltage test breakdown location method based on distributed optical fiber according to claim 1 is characterized in that: The coherent average noise reduction process is to add and average multiple groups of stable backscattered light under the same time axis. The signal-to-noise ratio (SNR) after noise reduction is expressed as: ; Where M is the number of backscattered light signals involved in the coherent average denoising process, is the average value of the amplitude coefficients of the backscattered light signals of group M participating in the coherent average denoising process, P r is the power of the backscattered light signal with unit amplitude, K is the total number of sampling points of a single backscattered light signal, and σ is the variance of the background noise of the M groups of backscattered light signals participating in the coherent average denoising process.

5. The GIS withstand voltage test breakdown location method based on distributed optical fiber according to claim 1 is characterized in that: Step S3 specifically includes: S301, starting from the initial signal, extract multiple groups of backscattered light signal amplitude lists, and perform discrete signal cross-correlation on a unified time axis R mn Analysis, the expression is: ; In the formula, R mn For the m The signal and n The cross-correlation of the signals, T i m For the m Signal No. i The amplitude per unit time, T i n For the n Signal No. i The amplitude per unit time, m ≤N, n ≤N; S302, until the cross-correlations of the extracted multiple groups of backscattered light signals are not less than the set value, it is determined that the initial state signal after the continuous distributed optical fiber is combined with the metal shell of the main circuit of the tested GIS is stable, and a reference signal is constructed; S303, under the same time axis, a list of multiple backscattered light amplitudes whose cross-correlations are not less than the set value is extracted, and then the average value of the amplitude in the same time unit is taken to construct a backscattered light reference signal. The amplitude expression of each time unit of the backscattered light reference signal is: ; Where, T rei is the backscattered light reference signal i The signal amplitude per time unit; S304: The constructed backscattered light reference signal is used as the initial signal for this voltage withstand test.

6. The GIS withstand voltage test breakdown location method based on distributed optical fiber according to claim 1 is characterized in that: The waveform distortion rate is calculated as follows: ; In the formula, S B1i is the first backscattered light signal collected after breakdown. i The signal distortion rate per time unit, T i B1 is the first backscattered light signal collected after the breakdown i The signal amplitude per time unit.

7. The method for GIS withstand voltage test breakdown location based on distributed optical fiber according to claim 5 is characterized in that: The breakdown vibration characteristics include: like Alarm value and , then it meets the breakdown vibration characteristics; In the formula, S Bmi The first m The backscattered light signal i The signal distortion rate per time unit, S Bni The first n The backscattered light signal i The signal distortion rate per time unit, m Greater than n and less than or equal to the number of lists of backscattered light signal amplitudes extracted after GIS breakdown.

8. The method for GIS withstand voltage test breakdown location based on distributed optical fiber according to claim 1 is characterized in that: The GIS position corresponding to the maximum waveform distortion point is calculated as follows: ; In the formula, L The calculated distance between the breakdown fault point and the starting end of the optical fiber is the fault breakdown point position. t i is the time unit corresponding to the point of maximum waveform distortion of the backscattered light signal, t N is the Nth backscattered light signal time unit divided.

9. A GIS withstand voltage test breakdown location system based on distributed optical fiber, used to implement a GIS withstand voltage test breakdown location method based on distributed optical fiber as claimed in any one of claims 1 to 8, characterized in that: The system includes: The optical pulse generation module continuously outputs optical pulse signals of preset power, frequency and pulse width to the distributed optical fiber through a laser light source; The signal acquisition module collects the backscattered light in real time through the photoelectric detection unit and converts it into an electrical signal, and at the same time performs coherent averaging noise reduction processing on the collected backscattered light signal; The signal processing module evenly divides the backscattered light conversion signal after noise reduction, selects the maximum signal amplitude sampled during the signal amplitude corresponding to each time unit, completes the continuous signal discretization processing, and obtains the backscattered light signal amplitude list of each time unit; Starting from the initial signal, extracting multiple groups of backscattered light signal amplitude lists for cross-correlation analysis until it is determined that the extracted multiple groups of signals are similar, and constructing a backscattered light reference signal after averaging the amplitudes of the multiple groups of waveforms in the same time unit on a unified time axis; During the withstand voltage test, the backscattered light is continuously collected in real time. After a breakdown fault occurs in the GIS, a list of backscattered light signal amplitudes at the moment of breakdown is extracted, which is compared with the backscattered light reference signal under a unified time axis, the waveform distortion rate of each time unit is calculated, and the signals of all time units whose waveform distortion rates reach or exceed the alarm value are extracted; The fault location module extracts a list of multiple backscattered light signal amplitudes after GIS breakdown, and compares them with the signal of the time unit when the waveform distortion rate of the backscattered light at the moment of breakdown reaches or exceeds the alarm value under the same time axis. If it meets the breakdown vibration characteristics, it is judged to be the waveform distortion caused by the GIS breakdown fault. The maximum waveform distortion point of the backscattered light signal caused by the GIS breakdown fault is extracted, and the GIS position corresponding to the maximum waveform distortion point is calculated, and the position is the GIS breakdown fault point.

10. The GIS withstand voltage test breakdown positioning system based on distributed optical fiber according to claim 9 is characterized in that: The waveform distortion rate alarm value set by the signal processing module is used to construct the backscattered light reference signal. The GIS metal shell is vibrated by knocking and the vibration sensor is used to detect the vibration value of the GIS metal shell. The vibration acceleration is calculated to be 5m / s 2 The waveform distortion rate of the backscattered light per unit time corresponding to the vibration position is set as the waveform distortion rate alarm value during this GIS withstand voltage test.

Images