CN113589121A

CN113589121A - Distributed optical fiber sensing partial discharge positioning and detecting method

Info

Publication number: CN113589121A
Application number: CN202111079504.3A
Authority: CN
Inventors: 周正仙; 刘浩; 郑贤锋; 张大伟; 崔执凤; 屈军; 余瑞兰; 徐晓峰; 朱晶晶; 冯小蔚; 陶天宝
Original assignee: Anhui Normal University
Current assignee: Anhui Normal University
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2021-11-02

Abstract

The invention realizes a high-precision distributed optical fiber sensing partial discharge positioning and detecting method based on the phase sensitive optical time domain reflection principle. The specific technical scheme is as follows: 1) the acquisition card converts an analog signal output by the detector into a digital signal, and then carries out transverse sliding average pretreatment on a Rayleigh backscattering signal along a curve direction to reduce a noise signal; 2) calculating an accumulation average curve and a difference curve of the original partial discharge signal, performing difference mean square calculation on the difference curve in a subsection mode to obtain a difference mean square curve, and performing accumulation average processing on the difference mean square curve to obtain a partial discharge signal positioning curve. 3) And performing sliding subtraction processing on the time domain signal at the positioning point, and then performing filtering processing to obtain a demodulated partial discharge signal.

Description

Distributed optical fiber sensing partial discharge positioning and detecting method

Technical Field

The invention relates to a distributed optical fiber partial discharge sensing method, in particular to a signal positioning and processing algorithm of a distributed optical fiber partial discharge sensing system based on a phase sensitive optical time domain reflection principle.

Background

A good insulation state is a prerequisite for ensuring safe operation of the power cables and the power equipment. Partial discharge is an early symptom and a main expression of cable insulation degradation, and effective detection and positioning of partial discharge behaviors of cables have important practical significance. Compared with the traditional method, the optical fiber sensor has the unique advantages of small volume, light weight, high sensitivity, low transmission loss, strong corrosion resistance, inherent electrical insulation property, electromagnetic interference resistance and the like, and becomes a research hotspot at home and abroad in recent years. Currently, the optical fiber sensing technologies available for partial discharge detection are: optical fiber Fabry-Perot interference sensing technology, optical fiber Bragg grating sensing technology and distributed optical fiber sensing technology. The patent refers to the field of 'optical elements, systems, or AN _ SNparatus'. The optical fiber Fabry-Perot interference sensing technology and the optical fiber Bragg grating sensing technology are commonly used for monitoring local points, and the distributed optical fiber sensing technology is commonly used for long-distance multipoint continuous monitoring.

The distributed optical fiber sensing system structure is shown in fig. 1. The narrow linewidth laser emits stable continuous light, and the stable continuous light is output as pulse light by the acousto-optic modulator. After being subjected to primary amplification by the erbium-doped fiber amplifier 1, the pulse is injected into the sensing fiber from the output end of the circulator. The backward scattered light generated in the sensing fiber returns through the return end of the circulator and is input to the erbium-doped fiber amplifier for amplification. The self-interference effect occurs in the backscattered light within one pulse width. When an external disturbance signal acts on the sensing optical fiber, the phase of the backward scattering light at the corresponding position of the sensing optical fiber changes, so that the light intensity of the self-interference signal also changes. The amplified signal light is input into a photoelectric detector to be converted into an analog electric signal after passing through a filter and an attenuator, then is input into an acquisition card to be converted into a digital signal, and finally enters a data processing system to obtain partial discharge position information and a discharge signal.

The distributed optical fiber vibration sensing technology realizes long-distance and multi-point distributed positioning and measurement, but the positioning performance of the distributed optical fiber vibration sensing technology is influenced by pulse width and sampling precision, and high-precision positioning and extraction of signals are difficult to realize. On the basis of the phase sensitive optical time domain reflection principle, the invention designs a high-precision positioning and extracting algorithm, and greatly improves the positioning performance of the system on the premise of not increasing the complexity and the cost of the system.

Disclosure of Invention

The invention aims to solve the technical problems of a positioning algorithm and a signal extraction algorithm of a partial discharge signal. Based on the phase sensitive light time domain reflection principle, a high-precision positioning and extracting algorithm is designed. The positioning performance of the system is greatly improved on the premise of not increasing the complexity and the cost of the system, and the high-precision distributed optical fiber partial discharge positioning and detecting system and the sensing method are realized. In order to achieve the above object, the present invention adopts the following technical solutions.

Step 1: the signal is pre-processed. The acquisition card converts the analog signals output by the detector into digital signals, and then performs sliding average processing on the original partial discharge signals along the length direction of the curve so as to reduce the fluctuation noise of the system.

Step 2: and carrying out positioning algorithm processing on the signals. 1) Longitudinally accumulating and averaging the original partial discharge signal curves to obtain an accumulated average curve of the original partial discharge signals, and subtracting the accumulated average curve from each original partial discharge signal curve to obtain a difference curve of the original partial discharge signals; 2) calculating an average value curve in a step length for the original partial discharge signal difference curves according to a fixed step length, and then carrying out subtraction, square and accumulation average calculation on each original partial discharge signal difference curve and the average value thereof in sequence in the same step length to obtain a difference mean square curve; 3) and performing accumulation average processing on the plurality of difference mean square curves obtained by the previous step to obtain a difference mean square curve. The position of the partial discharge signal can be determined by searching the peak position of the difference mean square curve.

And step 3: the signal is extracted and demodulated. And extracting data of the original partial discharge signal curve at the positioning point after the transverse moving average processing to obtain an original partial discharge signal time domain array. And performing sliding subtraction processing on the array to obtain a partial discharge signal time domain waveform curve, and performing band-pass filtering processing on the curve to filter external interference signals.

The invention has the advantages that on the basis of the phase sensitive optical time domain reflection principle, a high-precision positioning and extracting algorithm is designed, the complexity and the cost of the system are not increased, the positioning performance of the system is greatly improved, and the high-precision distributed optical fiber partial discharge positioning and detecting system and the sensing method are realized.

Drawings

The following is a brief description of the contents of each figure in the present specification.

Fig. 1 is a structural diagram of a distributed optical fiber partial discharge sensing system.

Fig. 2 is a flow chart of partial discharge signal localization and processing.

Fig. 3 is a graph of an original partial discharge signal.

Fig. 4 is a graph of partial discharge signal localization.

Fig. 5 is a time domain waveform diagram of a partial discharge signal at two locations.

Detailed Description

On the basis of the phase sensitive optical time domain reflection principle, the invention designs a high-precision positioning and detecting method of a partial discharge signal by using algorithms of sliding average, sliding subtraction, cumulative average, difference mean square and the like. The signal processing algorithm flow for partial discharge localization and detection is shown in fig. 2. The specific calculation method is as follows.

Step 1: and preprocessing a partial discharge signal. The acquisition card continuously acquires N (N = 51200) partial discharge signal original curvest _i,j(t _i,j ={t _i,1 , t _i,2 ,…… t _i,j ,……t _i,N })Each curve has a length i (i = 5400). Then, the original partial discharge signal is processed with the sliding average along the length direction of the curve (

L is the step length of the moving average, L = 3), and a curve after the moving average processing is obtained (L = 3)A _j ={A _m,1 , A _m,2 ,……A _m,j ,……A _m,N }). The curve of the raw partial discharge signal after the moving average processing is shown in fig. 3.

Step 2: and (4) a partial discharge signal positioning algorithm. Calculating an accumulation average curve and a difference curve of the original partial discharge signal, performing difference mean square calculation on the difference curve in a subsection mode to obtain a difference mean square curve, and performing accumulation average processing on the difference mean square curve to obtain a partial discharge signal positioning curve. The specific process is as follows: 1) performing accumulation average calculation on the original partial discharge signal matrix array to obtain an accumulation average value curve:

(ii) a 2) Calculating the difference between each original partial discharge signal curve and the accumulated average value curveΔt _i,j=t _i,j-B, obtaining N difference curves:Δt={Δt _i,1 , Δ t _i,2 ,……Δt _i,j ,……E _i,N }(ii) a 3) The original partial discharge signal curve after the moving average processing is processed by difference mean square processing (

,

) And obtaining a difference mean square curve:E={E _i,1 , E _i,2 ,…… E _i,v ,……E _i,k }(ii) a 4) The difference mean square curve is then subjected to cumulative average calculation to obtain a difference mean square curve, and a peak point on the difference mean square curve is the position of the partial discharge signal, as shown in fig. 4.

And step 3: and extracting and demodulating a partial discharge signal. 1) Extracting time domain data of the partial discharge signal at the positioning point:A _d ={A _d,1 , A _d,2 ,……A _d,j ,……A _d,N }(ii) a 2) Performing sliding subtraction processing on time domain data of the local discharge signal at the positioning point: (ΔA=A _d,q+s-A _d,q) To obtain a curve after sliding subtraction:ΔA={A ₁ ,A ₂ ,……A _N-s }. And then, filtering the demodulated partial discharge signal to obtain a time domain waveform diagram of the partial discharge signal, as shown in fig. 5.

The invention has been described above with reference to the accompanying drawings, it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to apply the inventive concept and solution to other applications without substantial modification.

Claims

1. The utility model provides a distributed optical fiber sensing partial discharge location and detection flow which characterized in that: firstly, preprocessing data acquired by an acquisition card to eliminate interference signals in acquired signals; then positioning the partial discharge signals in the preprocessed data; and finally, extracting the partial discharge signals at the positioning points for demodulation, and completing the positioning and detection of the partial discharge signals.

2. A distributed optical fiber sensing partial discharge positioning and detection algorithm is characterized in that:

step 1: preprocessing a partial discharge signal;the acquisition card continuously acquires N (N = 51200) partial discharge signal original curvest _i,j(t _i,j ={t _i,1 , t _i,2 ,…… t _i,j ,…… t _i,N })Each curve length is i (i = 5400); then, the original partial discharge signal is processed with the sliding average along the length direction of the curve (

L is the step length of the moving average, L = 3), and a curve after the moving average processing is obtained (L = 3)A _j ={A _m,1 , A _m,2 ,…… A _m,j ,…… A _m,N })(ii) a The original partial discharge signal curve after the moving average processing;

step 2: a partial discharge signal positioning algorithm; calculating an accumulation average curve and a difference curve of the original partial discharge signal, performing difference mean square calculation on the difference curve in a subsection manner to obtain a difference mean square curve, and performing accumulation average processing on the difference mean square curve to obtain a partial discharge signal positioning curve; the specific process is as follows: 1) performing accumulation average calculation on the original partial discharge signal matrix array to obtain an accumulation average value curve:

(ii) a 2) Calculating the difference between each original partial discharge signal curve and the accumulated average value curveΔt _i,j=t _i,j-B, obtaining N difference curves:Δt={Δt _i,1 , Δt _i,2 ,…… Δt _i,j ,……E _i,N }；

3) the original partial discharge signal curve after the moving average processing is processed by difference mean square processing (

,

) And obtaining a difference mean square curve:E= {E _i,1 , E _i,2 ,…… E _i,v ,…… E _i,k }(ii) a 4) Performing accumulation average calculation on the difference mean square curve to obtain a difference mean square curve, wherein a peak point on the difference mean square curve is the position of the partial discharge signal;

and step 3: extracting and demodulating a partial discharge signal; 1) extracting time domain data of the partial discharge signal at the positioning point:A _d = {A _d,1 , A _d,2 ,…… A _d,j ,…… A _d,N }(ii) a 2) Performing sliding subtraction processing on time domain data of the local discharge signal at the positioning point: (ΔA=A _d,q+s -A _d,q) To obtain a curve after sliding subtraction:ΔA={A ₁ , A ₂ ,……A _N-s }(ii) a And then filtering the demodulated partial discharge signal to obtain a time domain oscillogram of the partial discharge signal.