CN111273129A - Cable defect detection method and device based on composite test signal - Google Patents
Cable defect detection method and device based on composite test signal Download PDFInfo
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
Abstract
The application relates to a cable defect detection method, a device, computer equipment and a storage medium based on composite test signals, when cable defect detection is needed, a cable detection algorithm model adopted at this time and N parameter modes of the test signals corresponding to the model are obtained firstly, corresponding test signals are sent respectively according to different parameter modes, reflection signals of cables under different test signals can be obtained, the most significant reflection signals are selected for cable defect positioning, the reflection signals for cable defect positioning are made to be most consistent with the current application scene, and cable defect positioning accuracy can be improved remarkably.
Description
Technical Field
The present application relates to the field of defect detection technologies, and in particular, to a cable defect detection method and apparatus based on a composite test signal, a computer device, and a storage medium.
Background
Distribution cables are important components of a power grid system, and due to the fact that different cables are different in quality, service environment, service life and the like, some defects may exist in some cables, and therefore cable defect detection is of great significance for guaranteeing safe and reliable operation of a power grid.
At present, methods for online detection of cable defects mainly include a noise Reflectometry (NDR), a carrier test method, a direct Sequence Time Domain Reflectometry (STDR), a Spread Spectrum Time Domain Reflectometry (SSTDR), and the like, where SSTDR is used as a main technical stream, and SSTDR is a cable fault detection and positioning technology developed on the basis of TDR, and can more accurately detect cable defects. The early research on the SSTDR method is mainly used for detecting impedance mismatching points in telephone twisted-pair wires, and the further research is applied to the fault online detection of aircraft communication cables, so that the SSTDR method can still obtain a good positioning effect even under the condition of a low signal-to-noise ratio.
Although the conventional SSTDR method has a good cable defect detection effect, the conventional SSTDR method is influenced by complex detection environment factors in practical application, and has the defect of low defect detection precision, so that a cable defect detection scheme needs to be further researched to improve the defect detection precision.
Disclosure of Invention
In view of the above, it is necessary to provide a cable defect detection method, apparatus, computer device and storage medium based on a composite test signal, which have high defect localization accuracy.
A method for cable defect detection based on a composite test signal, the method comprising:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the non-selected parameter mode exists in the N parameter modes, returning the randomly selected parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of a cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals, and positioning the positions of the cable defects.
In one embodiment, the collecting the reflected signals of the cable to obtain a reflected signal set, and selecting the most significant reflected signal in the reflected signal set includes:
collecting a reflection signal of the cable, and constructing a reflection signal set;
detecting whether a reflected signal with the significance larger than a preset threshold exists in the reflected signal set or not;
if the reflection signals exist, stopping sending the test signals, and taking the reflection signals with the significance greater than a preset threshold value as the most significant reflection signals;
and if not, selecting the most significant reflected signal in the reflected signal set.
In one embodiment, the significance of the reflected signal is processed by:
acquiring a reflection signal and a corresponding test signal;
performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal;
extracting the amplitude and width of the output signal;
and determining the significance of the reflected signal according to the amplitude and the width of the output signal.
In one embodiment, the collecting the reflected signals of the cable and obtaining the reflected signal set includes:
collecting a reflected signal of the cable;
and isolating and collecting different reflection signals to obtain a reflection signal set.
In one embodiment, the method for detecting a cable defect based on a composite test signal further includes:
and when the unselected parameter mode does not exist in the N parameter modes and the reflected signal is not collected, judging that the cable has no defect.
In one embodiment, the parameter pattern of the test signal includes corresponding patterns of different combinations of carrier frequency, modulation mode, signal duration, type of PN sequence, symbol duration and period of the symbol.
In one embodiment, the randomly selected parameter pattern is used as a test parameter pattern, and the sending of the test signal based on the test parameter pattern comprises;
and randomly selecting a parameter mode as a test parameter mode, and sending a test signal by adopting time division multiplexing, frequency division multiplexing or code division multiplexing based on the test parameter mode.
A composite test signal based cable defect detection apparatus, the apparatus comprising:
the data acquisition module is used for identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
the test sending module is used for randomly selecting a parameter mode as a test parameter mode and sending a test signal based on the test parameter mode;
a cycle test module, configured to control the test sending module to execute the randomly selected parameter mode again as a test parameter mode and send a test signal based on the test parameter mode when an unselected parameter mode exists in the N parameter modes;
the reflection acquisition module is used for acquiring reflection signals of the cable to obtain a reflection signal set, and selecting the most obvious reflection signal in the reflection signal set;
and the defect positioning module is used for detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals and positioning the positions of the cable defects.
A computer device comprising a memory and a processor, the memory storing a computer program, the processor implementing the following steps when executing the computer program:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the non-selected parameter mode exists in the N parameter modes, returning the randomly selected parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of a cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals, and positioning the positions of the cable defects.
A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, carries out the steps of:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the non-selected parameter mode exists in the N parameter modes, returning the randomly selected parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of a cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals, and positioning the positions of the cable defects.
According to the cable defect detection method and device based on the composite test signal, the computer equipment and the storage medium, when the cable defect detection is needed, the cable detection algorithm model adopted at this time and the N parameter modes of the test signal corresponding to the model are obtained firstly, the corresponding test signals are sent according to different parameter modes respectively, the reflection signals of the cables under different test signals can be obtained, the most obvious reflection signal is selected for cable defect positioning, the reflection signal for cable defect positioning is made to be the most consistent with the current application scene, and the cable defect positioning precision can be improved remarkably.
Drawings
FIG. 1 is a diagram illustrating an exemplary embodiment of a method for detecting defects in a cable based on a composite test signal;
FIG. 2 is a schematic flow chart illustrating a method for detecting cable defects based on composite test signals according to an embodiment;
FIG. 3 is a schematic diagram of an SSTDR cable fault detection model in one embodiment;
FIG. 4 is a schematic flow chart illustrating a cable defect detection method based on composite test signals according to another embodiment;
FIG. 5 is a schematic diagram of m-sequence generation;
FIG. 6 is a schematic diagram of Gold sequence generation;
FIG. 7 is a block diagram of a cable defect detecting apparatus based on composite test signals according to an embodiment;
FIG. 8 is a diagram illustrating an internal structure of a computer device according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The cable defect detection method based on the composite test signal can be applied to the application environment shown in fig. 1. Wherein, the cable defect detecting device 102 is connected with the cable 104 (cable to be detected), the cable defect detecting device 102 obtains the loaded cable detection algorithm model and the N parameter modes of the test signals corresponding to the cable detection algorithm model, randomly selects the parameter mode as the test parameter mode, sends the test signals to the cable 104 based on the test parameter mode, returns to the randomly selected parameter mode as the test parameter mode when the unselected parameter modes exist in the N parameter modes, sends the test signals to the cable 104 based on the test parameter mode, the cable defect detecting device 102 captures the reflection signals fed back by the cable 104 to obtain a reflection signal set, selects the most significant reflection signals in the reflection signal set, and performs cable defect detection according to the cable detection algorithm model, the most significant reflection signals and the test signals corresponding to the most significant reflection signals, the defect location of the cable 104 is located.
In one embodiment, as shown in fig. 2, a cable defect detection method based on composite test signals is provided, which is described by taking the cable detection apparatus 102 in fig. 1 as an example, and includes the following steps:
s100: and identifying the cable detection algorithm model and acquiring N parameter modes of the cable detection algorithm model corresponding to the test signals, wherein N is a positive integer.
The cable detection algorithm model refers to a model for running a cable detection algorithm, and the model can be a model constructed based on a cable defect detection algorithm such as a noise reflection method, a carrier wave test method, a direct sequence time domain reflection method or a spread spectrum time domain reflection method, and preferentially, a cable detection algorithm model constructed based on a spread spectrum time domain reflection method can be selected. Different cable detection algorithm models generally have different test signal parameter modes, the parameter modes refer to corresponding modes under different combinations of carrier frequency, modulation mode, signal duration, type of PN sequence, symbol duration and period of symbol, that is, the test signals generated under different parameter modes have single or multiple differences in the aspects of carrier frequency, modulation mode, signal duration, type of PN sequence, symbol duration and period combination of symbol, etc. Here, the cable defect detecting device identifies a current cable detection algorithm model corresponding to itself, and obtains N parameter patterns of the test signal corresponding to the current cable detection algorithm model, for example, the cable defect detecting device identifies that the current cable defect detecting device is an SSTDR cable fault detecting algorithm model, and obtains N parameter patterns of the test signal corresponding to the SSTDR cable fault detecting algorithm model.
In practical application, the server can load a cable detection algorithm model, and simulate hardware equipment to execute a cable defect detection process in a software simulation mode; in addition, the cable detection algorithm model may also be an electronic device implanted with a cable detection algorithm, the electronic device may include a parameter mode selection module, a PN sequence generator, a signal modulation module, a signal transmission module, reflected signal acquisition, defect signal processing, defect type determination, and defect point positioning, a specific structural schematic diagram of the electronic device may be shown in fig. 3, and these components cooperate to execute the cable detection algorithm of the present application to position a defect position of a cable.
S200: and randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode.
And randomly selecting some parameter modes as test parameter modes, and sending test signals to the cable (the cable to be tested) based on the test parameter modes. In the process of random selection, only one parameter mode can be selected at a time, namely, only a single test signal is generated and sent to the cable at a time, and a plurality of parameter modes can be selected at a time, namely, a certain number of test signals are generated and sent to the cable at a time. It can be understood that if the test signal is sent based on the time division multiplexing mode when the test signal is sent, the collected reflection signal is detected based on the corresponding time division multiplexing during the subsequent defect detection; if the test signal is sent based on the frequency division multiplexing mode when the test signal is sent, detecting the acquired reflection signal after demultiplexing the corresponding frequency division during the subsequent defect detection; if the test signal is sent based on the code division multiplexing mode during the sending of the test signal, the acquired reflection signal is detected after being demultiplexed based on the corresponding code division during the subsequent defect detection. Furthermore, in order to reduce the repeated transmission of test signals under the same test parameter pattern, a non-repeated random selection mode may be adopted in the selection process, that is, a single parameter pattern may be selected only once as a test parameter pattern. In practical application, different test signals can be generated based on the parameter mode, a test signal list and a corresponding test signal set are constructed, and based on the sequence of the test signal list, single or multiple test signals are sent to the cable from the test signal set in one selection.
S300: and returning to S200 when the unselected parameter mode exists in the N parameter modes.
When there is still a parameter pattern that has not been selected, indicating that a new test signal is not used, the process returns to step S200 to continue sending test signals to the cable. When all the N parameter modes have been selected, step S400 is entered. For example, if N is 5 and A, B, C, D, E5 parameter patterns are respectively present, in the first round, the a parameter pattern is selected to generate a test signal a to be sent to the cable, and it is determined that an unselected parameter pattern B, C, D, E still exists in the current 5 parameter patterns, the procedure returns to step S200 to continue selecting the B parameter pattern, generate a test signal B to be sent to the cable … …, the E parameter pattern is selected to generate a test signal E to be sent to the cable, and it is determined that all the current 5 parameter patterns are selected and an unselected parameter pattern does not exist, the procedure proceeds to the next step S400. It is understood that the embodiment for single selection of multiple parameter modes is similar to the above embodiments and will not be described herein.
S400: and collecting the reflected signals of the cable to obtain a reflected signal set, and selecting the most obvious reflected signal in the reflected signal set.
The method comprises the steps of collecting reflected signals of a cable while sending a test signal to the cable to obtain a reflected signal set, and selecting the most significant reflected signal in the reflected signal set. If the cable has defects, generally, each test signal corresponds to one reflection signal, and different reflection signals can be isolated and collected to obtain a reflection signal set while the transmission signal of the cable is collected. The most significant reflected signal may specifically refer to a reflected signal with the most significant time domain correlation deviation from the corresponding test signal, that is, a reflected signal with the largest amplitude and width of the signal after the time domain correlation processing is performed on the corresponding test signal. It can be understood that the most significant reflected signal can most accurately represent the cable defect position, and therefore, the cable defect position is selected to be positioned in the next step.
S500: and detecting the cable defects according to the cable detection algorithm model, the most obvious reflected signals and the test signals corresponding to the most obvious reflected signals, and positioning the positions of the cable defects.
And detecting the cable defects according to the selected most significant reflected signal, the corresponding test signal and the cable algorithm model, and positioning the positions of the cable defects. Specifically, the reflected wave significance is calculated for each parameter mode, the reflected signal with the maximum significance is selected as the optimal reflected signal, and the cable defect position is located. When a defect point exists in the cable, the transmission signal is reflected at the impedance mismatch position, and according to the basic principle of the time domain reflection method, the relative distance between the defect point and the measuring point is as follows:
in the above formula, v0Representing the propagation velocity, v, of an incident wave in the cable0Is the delay value of the defect signal and dis is the relative distance of the defect point and the measurement point.
According to the cable defect detection method based on the composite test signal, when the cable defect detection is needed, the cable detection algorithm model adopted at this time and the N parameter modes of the test signal corresponding to the model are obtained firstly, the corresponding test signals are sent according to different parameter modes respectively, the reflection signals of the cable under different test signals can be obtained, the most significant reflection signal is selected for cable defect positioning, the reflection signal for cable defect positioning is made to be the most consistent with the current application scene, and the cable defect positioning precision can be significantly improved.
As shown in fig. 4, in one embodiment, step S400 includes:
s420: and collecting the reflection signals of the cable to construct a reflection signal set.
S440: and detecting whether the reflected signals with the significance larger than a preset threshold exist in the reflected signal set.
S462: and if so, stopping sending the test signal, and taking the reflection signal with the significance greater than the preset threshold value as the most significant reflection signal.
S464: if not, selecting the most significant reflected signal in the reflected signal set.
The preset threshold is a preset threshold representing obvious significance, and can be set according to historical experience data, expert data and the like, if the significance is greater than the preset threshold, the transmitted signal is indicated to meet the requirement of defect detection precision, at the moment, a subsequent test signal is not required to be transmitted, and the reflected signal with the significance greater than the preset threshold is used as the most significant reflected signal; and if the reflected signals with the significance larger than the preset threshold value do not exist, selecting the most significant reflected signals from the reflected signal set. The step of stopping sending the test signal means that if the reflected signal with the significance greater than the preset threshold value is detected, the test signal is stopped to be continuously sent to the cable, the cable defect detection equipment stops sending the test signal, and the next-stage defect positioning operation is started.
For further explanation, the description continues with the above application example, after the test signal a is sent, the cable defect detection device collects the reflected signal a for significance detection; after the test signal B is sent, a reflected signal B is collected to carry out significance detection; after the C test signal is sent, collecting a C reflection signal for significance detection; constructing a current reflection signal set comprising an A reflection signal, a B reflection signal and a C reflection signal, stopping sending a D test signal and an E test signal when detecting that the C reflection signal is a reflection signal with the significance greater than a preset threshold value, and directly entering the next defect positioning operation by using the C reflection signal; and if no reflected signal with the significance greater than the preset threshold value is detected in the received E reflected signals, selecting the reflected signal with the maximum significance from the reflected signal set to enter the next defect positioning operation.
In one embodiment, the significance of the reflected signal is processed by:
acquiring a reflection signal and a corresponding test signal; performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal; extracting the amplitude and width of the output signal; the significance of the reflected signal is determined from the amplitude and width of the output signal.
Generally, the larger the amplitude and width of the output signal, the better the significance of the reflected signal, and further, the significance can be directly quantified by means of a formula. In practical application, the reflection signal and the corresponding test signal can be sent to the time domain correlator, the amplitude and the width of the output signal of the time domain correlator are extracted, and the significance of the reflection signal is obtained according to a preset significance calculation formula. The preset significance calculation formula is as follows:
L＝w1(A-A0)+w2(K-K0)
in the above formula, A and K are the amplitude and width of the output signal of the time domain correlator, respectively, A0And K0Is a preset threshold value, w1And w2Is a predetermined weight, A0And K0，w1And w2The values of (a) are given according to the expert's experience.
In one embodiment, collecting the reflected signals of the cable, and obtaining the reflected signal set comprises:
collecting a reflected signal of the cable; and (4) isolating and collecting different reflection signals to obtain a reflection signal set.
And collecting and isolating the reflected signal of the transmitted signal passing through the cable. In practical application, the high-speed analog-to-digital converter can be used for completing discretization collection of a reflected signal, signal isolation refers to the fact that a signal of a fault point can be superposed with a forward-propagating test signal in the reflection process, therefore, the test signal needs to be isolated, namely, the forward-propagating signal is separated, a network transformer can be designed to achieve the signal isolation, the network transformer has the functions of electrical isolation, common mode and differential mode noise suppression, the high-voltage signal isolation, electromagnetic interference signal suppression and signal coupling, the basic structure of the network transformer comprises a common mode choke coil, an autotransformer and other two large components, and the signal isolation can be effectively achieved.
In one embodiment, the method for detecting a cable defect based on a composite test signal further includes:
and when the unselected parameter mode does not exist in the N parameter modes and the reflected signal is not collected, judging that the cable has no defect.
When the reflected signal is not received when the test signal is continuously sent, the current cable is normal, and no defect exists.
In order to further explain the technical scheme, technical principle and effect of the composite test signal-based cable defect detection method of the present application in detail, the SSTDR cable fault detection algorithm model is taken as an application example, and the whole process is derived and described in detail through a strict mathematical formula.
An SSTDR cable fault detection algorithm model is shown in FIG. 3, and comprises the following parts: the system comprises a parameter mode selection part, an oscillator, a pulse generator, a PN sequence generator, a signal modulation module, a phase delayer, a reflected signal acquisition and signal isolation module, a time domain correlator, a defect type judgment part, a defect point positioning part and the like.
The algorithm shown in fig. 3 selects a corresponding parameter mode (including different combinations of carrier frequencies, modulation modes, signal durations, types of PN sequences, symbol durations, symbol periods, and the like), generates a pulse signal through an oscillator to drive a PN sequence generator, and modulates a cosine wave with the generated PN sequence to form a transmission signal to be injected into a cable to be tested. Meanwhile, after the other path of oscillation signal is delayed, a reference signal is formed in the same way as the transmission signal. If the transmitted signal encounters a defect point during the propagation in the cable, the transmitted signal is reflected, after the reflected signal is received, the system sends the delayed reference signal and the collected reflected signal to a time domain correlator to obtain the delay time of the signal, calculates the defect position by combining the reflection principle, judges the type of the cable defect according to the peak point characteristic of the signal output by the correlator, and finally outputs a corresponding result.
In this application example, the implementation process of the cable defect detection method based on the composite test signal according to the present application is described in detail as follows:
step 1: and establishing an SSTDDR cable fault detection model of the composite measurement signal, setting an N parameter mode of the test signal, and initializing i to be 0.
The method comprises the following specific steps:
step 1-1: different combinations of carrier frequencies, modulation schemes, signal durations, types of PN sequences, symbol durations, and symbol periods are set. In the detection of the SSTDR method, the selection methods of carrier frequencies, modulation modes, signal duration, types of PN sequences, symbol duration and symbol periods of different combinations are as follows:
for carrier frequencies, selecting total five carrier frequencies which are 0.25 times, 0.5 times, 1 time, 2 times and 4 times of PN sequence code element rate, namely f1 is 0.25 RB; f2 ═ 0.5 RB; f3 ═ RB; f4 ═ 2 RB; f 5-4 RB, where RB is the symbol rate of the PN sequence, and RB-Tc-1, where Tc is the symbol duration. For the modulation modes, the modulation modes include binary amplitude keying (2ASK), binary frequency shift keying (2FSK), and binary phase shift keying (2PSK), and the three modulation modes are defined as follows: binary amplitude keying (2ASK) uses digital signals of '0' and '1' to key a continuous carrier respectively, controls the amplitude change of the carrier according to binary information, and has the expression:
in the above formula, p2ASK(T) is a 2ASK modulated signal, s (T) is a unipolar non-return-to-zero rectangular pulse sequence, ω is the angular velocity of the carrier, T is the time, TcFor the duration of a PN sequence symbol, g (T) is of width TcAmplitude of anPulse of (a)n∈[0,1]And a is anThe probability of 1 is taken as p, and the probability of 0 is taken as 1-p.
Binary frequency shift keying (2FSK) uses the frequency of the carrier to correspond to different digital information, 2FSK carrier frequencyAt two different frequencies f1And f2The expression is:
p2FSK(t)＝s1(t)cos(2πf1t)+s2(t)cos(2πf2t)
in the above formula, p2FSK(t) is the signal after 2FSK modulation, s1(t) is a unipolar non-return-to-zero rectangular pulse sequence, s2(t) is for s1(T) a pulse sequence formed by symbol-by-symbol inversion, g (T) being of width TcAmplitude of anPulse of (a)1∈[0,1]And a is a1 Taking 1 probability as p and 0 probability as 1-p, a2Is a1The complement of (2).
Binary phase shift keying (2PSK) uses carrier phase variation to convey different information, and its time domain can be expressed as:
wherein p is2PSK(t) is a 2PSK modulated signal, s (t) is a bipolar non-return-to-zero rectangular pulse sequence, an∈[-1,1]And a is anThe probability of 1 is taken as p, and the probability of-1 is taken as 1-p.
For the type of PN sequence, m-sequence, Gold code, Kasami code, Barker code, Legendre sequence, etc. are included. The various sequence introduction and generation methods described above are as follows:
the m-sequence is a sequence generated by a multi-stage linear shift register, and the basic generation principle is shown in fig. 5;
the Gold sequence is generated by adding a pair of m sequences with equal clock rate and same code length and modulo 2, and the generation principle is shown in fig. 6.
Kasami sequences are also derived from m-sequences and are divided into large and small sets of Kasami sequences, where a small set of Kasami sequences is a subset of a large set of Kasami sequences. The small sequence set can be obtained by sampling m sequences with the period of N-2N-1, and the large sequence set is obtained by constructing one m sequence and preferably a pair of m sequences and a third sequence.
The Barker code is a non-periodic binary code group with a special rule, and the sequence code element can only take +1 or-1. Only 7 groups are currently known, as follows:
2-bit Barker code: +1,+1
3-bit Barker code: +1,+1, -1
4-bit Barker code: +1, +1, +1, -1 and +1, +1, -1, +1
5-bit Barker code: +1,+1,+1, -1,+1
7-bit Barker code: +1,+1,+1, -1, -1,+1, -1
11-bit Barker code: +1,+1,+1, -1, -1, -1,+1, -1, -1,+1, -1
13-bit Barker code: +1,+1,+1,+1,+1, -1, -1,+1,+1, -1,+1, -1,+1
The Legendre sequence is also referred to as the quadratic residue sequence, which is defined as: specifying an odd number p, if an integer x can be found within 1 to p such that the equation x2 ≡ i (mod p) holds (where i is some integer and mod is the remainder operator), then i is considered to be the quadratic residue modulo p, otherwise i is called the quadratic non-residue modulo p. The Legendre sequence is defined as follows:
in the above equation ai is the symbol sequence value. Selecting the duration Tc and the period N of the code element according to expert experience values; for the signal duration, an integer multiple of the PN sequence period may be selected, e.g., N, 2N, 3N …, where N is the period of the PN sequence.
Step 1-2: for each type of parameter pattern in step 1-1, N parameter patterns of the test signal are selected and set, followed by initializing i to 0.
Step 2: the test signal is transmitted in an ith parameter mode and the reflected signal is recorded.
Step 2-1: the principle diagram of the SSTDR cable defect detection is shown in fig. 6, and for a certain parameter mode, the specific detection process is as follows:
the emission signal s (t) for SSTDR detection can be expressed as:
s(t)＝mod[c·cosωt]
in the above formula, c ═ c0,c1,c2,...cN-1]Representing a bipolar binary sequence of length N (i.e., c) generated by a PN sequence generatornE { -1,1}), and the symbol mod () represents the modulation of a carrier, and mainly comprises three types of 2ASK, 2FSK and 2 PSK;
step 2-2: after the signal is modulated, the system injects the signal into the cable to be tested, mainly changes the discrete sequence generated by the signal generator into a continuous signal after passing through a digital-to-analog converter and injects the continuous signal into the cable to be tested, if the cable has defects, the signal is reflected by the defect and then is received by a signal receiving device;
step 2-3: the method mainly utilizes a high-speed analog-to-digital converter to finish discretization acquisition of the reflected signal, wherein signal isolation refers to superposition of a signal of a fault point and a forward-transmitted test signal in a reflection process, so that the test signal needs to be isolated, namely the forward-transmitted signal is separated, and a network transformer can be designed to realize the signal isolation;
step 2-4: after collecting the reflected signal and taking signal isolation measure, sending it and the delayed reference signal into the correlator, and obtaining the correlator output as:
in the above formula, Rsr(t) represents the output signal of the time-domain correlator; t represents a time variable; τ represents an integral variable; r (t) ═ Σ aks(t-Tk) + n (t) is the output of the received signal after signal isolation, and s (τ) is the integral of the transmitted signal s (t) over τ; s (T-T)k) Is a time delay TkThe latter transmitted signal, i.e. the reference signal; t isk( k 1,2, 3.) denotes a delay time of the reflected signal, and a represents a delay time of the reflected signalk(t-τ-Tk) Is the attenuation coefficient akFor (tau + T)k) The intermediate amount after the delay, n (T-tau), is the intermediate amount after the noise signal n (T) is delayed tau, where the integral of T means the integral over the entire reflected signal time.
If the noise signal is white gaussian noise:
thus, the expected values of the correlator outputs are:
in the above formula, E { Rsr(T) represents the expected value of the correlator output, τ is the integration variable, Tk( k 1,2, 3.) is the delay time of the reflected signal, ak(t-τ-Tk) Is the attenuation coefficient akFor (tau + T)k) The intermediate amount after the delay, where the integral of T means the integral of the entire reflected signal time. For E { RsrAnd (t) detecting the peak value of the (t) as a characteristic by combining with expert experience to obtain the type of the cable defect.
And step 3: if i is equal to i +1, if i < N, go to step 2. Namely, after collecting the corresponding reflection signal, switching to the next parameter mode, and collecting the reflection signal by the method of step 2.
And 4, step 4: and (3) if the reflected signals are not detected in all the reflected signals obtained in the step (2), judging that the cable is free of defects, otherwise, selecting the reflected signal with the most obvious reflected wave from all the reflected signals to position the defects.
In step 4, the significance of the reflected wave is measured by the following formula.
L＝w1(A-A0)+w2(K-K0)
Where A and K are the amplitude and width of the time domain correlator output signal, respectively, A0And K0Is a preset threshold value, w1And w2Is a predetermined weight, A0And K0，w1And w2The values of (a) are given according to the expert's experience.
And 4, calculating the significance of the reflected wave of each parameter mode, selecting the reflected signal with the maximum significance as the optimal reflected signal, and positioning the defect position of the cable. The positioning method comprises the following steps:
when a defect point exists in the cable, the transmission signal is reflected at the impedance mismatch position, and according to the basic principle of the time domain reflection method, the relative distance between the defect point and the measuring point is as follows:
in the above formula, v0Representing the propagation velocity, v, of an incident wave in the cable0Is the delay value of the defect signal and dis is the relative distance of the defect point and the measurement point. In the SSTDR cable defect detection method based on the composite test signal, if the significance of the detected reflection signal in the ith parameter mode is greater than a preset value, the reflection signal is used for positioning the defect, and the test signals in the (i + 1) th to (N-1) th parameter modes are not transmitted.
It should be understood that although the steps in the flowcharts of fig. 2 and 4 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 2 and 4 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed in turn or alternately with other steps or at least some of the other steps.
In one embodiment, as shown in fig. 7, there is provided a cable defect detecting apparatus based on a composite test signal, the apparatus including:
the data acquisition module 100 is configured to identify a cable detection algorithm model and acquire N parameter patterns of a test signal corresponding to the cable detection algorithm model, where N is a positive integer;
a test sending module 200, configured to randomly select a parameter pattern as a test parameter pattern, and send a test signal based on the test parameter pattern;
a cycle test module 300, configured to control the test sending module to re-execute an operation of randomly selecting a parameter mode as a test parameter mode and sending a test signal based on the test parameter mode when an unselected parameter mode exists in the N parameter modes;
the reflection acquisition module 400 is used for acquiring the reflection signals of the cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and the defect positioning module 500 is configured to perform cable defect detection according to the cable detection algorithm model, the most significant reflected signal, and the test signal corresponding to the most significant reflected signal, and position a cable defect position.
According to the cable defect detection device based on the composite test signal, when the cable defect detection is needed, the cable detection algorithm model adopted at this time and the N parameter modes of the test signal corresponding to the model are obtained firstly, the corresponding test signals are sent according to different parameter modes respectively, the reflection signals of the cable under different test signals can be obtained, the most significant reflection signals are selected for cable defect positioning, the reflection signals for cable defect positioning are made to be most consistent with the current application scene, and the cable defect positioning precision can be significantly improved.
In one embodiment, the reflection collecting module 400 is further configured to collect reflection signals of the cable to construct a reflection signal set; detecting whether a reflection signal with the significance larger than a preset threshold exists in the reflection signal set or not; if the reflection signals exist, stopping sending the test signals, and taking the reflection signals with the significance greater than a preset threshold value as the most significant reflection signals; if not, selecting the most significant reflected signal in the reflected signal set.
In one embodiment, the significance of the reflected signal is processed by:
acquiring a reflection signal and a corresponding test signal; performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal; extracting the amplitude and width of the output signal; the significance of the reflected signal is determined from the amplitude and width of the output signal.
In one embodiment, the reflection collection module 400 is further configured to collect a reflection signal of the cable; and (4) isolating and collecting different reflection signals to obtain a reflection signal set.
In one embodiment, the defect locating module 500 is further configured to determine that the cable has no defect when the non-selected parameter mode does not exist in the N parameter modes and no reflected signal is collected.
In one embodiment, the parameter pattern of the test signal includes corresponding patterns of different combinations of carrier frequency, modulation mode, signal duration, type of PN sequence, symbol duration and period of the symbol.
In one embodiment, the test transmission module 200 is further configured to randomly select a parameter pattern as the test parameter pattern, and transmit the test signal by time division multiplexing, frequency division multiplexing, or code division multiplexing based on the test parameter pattern.
For specific limitations of the cable defect detecting apparatus based on the composite test signal, reference may be made to the above limitations of the cable defect detecting method based on the composite test signal, and details are not repeated here. The modules in the cable defect detecting device based on the composite test signal can be wholly or partially realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as shown in fig. 8. The computer device includes a processor, a memory, and a network interface connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the computer equipment is used for storing different cable defect detection algorithm models based on the composite test signals, reference modes corresponding to the test signals and other data. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a method for cable defect detection based on a composite test signal.
Those skilled in the art will appreciate that the architecture shown in fig. 8 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
In one embodiment, a computer device is provided, comprising a memory and a processor, the memory having a computer program stored therein, the processor implementing the following steps when executing the computer program:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the unselected parameter mode exists in the N parameter modes, returning to the random parameter mode to be used as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of the cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most obvious reflected signals and the test signals corresponding to the most obvious reflected signals, and positioning the positions of the cable defects.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
collecting a reflection signal of the cable, and constructing a reflection signal set; detecting whether a reflection signal with the significance larger than a preset threshold exists in the reflection signal set or not; if the reflection signals exist, stopping sending the test signals, and taking the reflection signals with the significance greater than a preset threshold value as the most significant reflection signals; if not, selecting the most significant reflected signal in the reflected signal set.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
acquiring a reflection signal and a corresponding test signal; performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal; extracting the amplitude and width of the output signal; the significance of the reflected signal is determined from the amplitude and width of the output signal.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
collecting a reflected signal of the cable; and (4) isolating and collecting different reflection signals to obtain a reflection signal set.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
and when the unselected parameter mode does not exist in the N parameter modes and the reflected signal is not collected, judging that the cable has no defect.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
and randomly selecting a parameter mode as a test parameter mode, and sending a test signal by adopting time division multiplexing, frequency division multiplexing or code division multiplexing based on the test parameter mode.
In one embodiment, a computer-readable storage medium is provided, having a computer program stored thereon, which when executed by a processor, performs the steps of:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the unselected parameter mode exists in the N parameter modes, returning to the random parameter mode to be used as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of the cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most obvious reflected signals and the test signals corresponding to the most obvious reflected signals, and positioning the positions of the cable defects.
In one embodiment, the computer program when executed by the processor further performs the steps of:
collecting a reflection signal of the cable, and constructing a reflection signal set; detecting whether a reflection signal with the significance larger than a preset threshold exists in the reflection signal set or not; if the reflection signals exist, stopping sending the test signals, and taking the reflection signals with the significance greater than a preset threshold value as the most significant reflection signals; if not, selecting the most significant reflected signal in the reflected signal set.
In one embodiment, the computer program when executed by the processor further performs the steps of:
acquiring a reflection signal and a corresponding test signal; performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal; extracting the amplitude and width of the output signal; the significance of the reflected signal is determined from the amplitude and width of the output signal.
In one embodiment, the computer program when executed by the processor further performs the steps of:
collecting a reflected signal of the cable; and (4) isolating and collecting different reflection signals to obtain a reflection signal set.
In one embodiment, the computer program when executed by the processor further performs the steps of:
and when the unselected parameter mode does not exist in the N parameter modes and the reflected signal is not collected, judging that the cable has no defect.
In one embodiment, the computer program when executed by the processor further performs the steps of:
and randomly selecting a parameter mode as a test parameter mode, and sending a test signal by adopting time division multiplexing, frequency division multiplexing or code division multiplexing based on the test parameter mode.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware related to instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile memory may include Read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for cable defect detection based on a composite test signal, the method comprising:
identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
randomly selecting a parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
when the non-selected parameter mode exists in the N parameter modes, returning the randomly selected parameter mode as a test parameter mode, and sending a test signal based on the test parameter mode;
collecting reflection signals of a cable to obtain a reflection signal set, and selecting the most significant reflection signals in the reflection signal set;
and detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals, and positioning the positions of the cable defects.
2. The method of claim 1, wherein collecting the reflected signals from the cable to obtain a reflected signal set, and wherein selecting the most significant reflected signal in the reflected signal set comprises:
collecting a reflection signal of the cable, and constructing a reflection signal set;
detecting whether a reflected signal with the significance larger than a preset threshold exists in the reflected signal set or not;
if the reflection signals exist, stopping sending the test signals, and taking the reflection signals with the significance greater than a preset threshold value as the most significant reflection signals;
and if not, selecting the most significant reflected signal in the reflected signal set.
3. The method of claim 1, wherein the significance of the reflected signal is obtained by processing:
acquiring a reflection signal and a corresponding test signal;
performing time domain correlation processing on the reflection signal and the corresponding test signal to obtain an output signal;
extracting the amplitude and width of the output signal;
and determining the significance of the reflected signal according to the amplitude and the width of the output signal.
4. The method of claim 1, wherein collecting the reflected signals from the cable to obtain a set of reflected signals comprises:
collecting a reflected signal of the cable;
and isolating and collecting different reflection signals to obtain a reflection signal set.
5. The method of claim 1, further comprising:
and when the unselected parameter mode does not exist in the N parameter modes and the reflected signal is not collected, judging that the cable has no defect.
6. The method of claim 1, wherein the parameter pattern of the test signal comprises corresponding patterns for different combinations of carrier frequency, modulation scheme, signal duration, type of PN sequence, symbol duration, and symbol period.
7. The method of claim 1, wherein the randomly selected parameter pattern is used as a test parameter pattern, and wherein sending a test signal based on the test parameter pattern comprises;
and randomly selecting a parameter mode as a test parameter mode, and sending a test signal by adopting time division multiplexing, frequency division multiplexing or code division multiplexing based on the test parameter mode.
8. A cable defect detection apparatus based on composite test signals, the apparatus comprising:
the data acquisition module is used for identifying a cable detection algorithm model and acquiring N parameter modes of a test signal corresponding to the cable detection algorithm model, wherein N is a positive integer;
the test sending module is used for randomly selecting a parameter mode as a test parameter mode and sending a test signal based on the test parameter mode;
a cycle test module, configured to control the test sending module to execute the randomly selected parameter mode again as a test parameter mode and send a test signal based on the test parameter mode when an unselected parameter mode exists in the N parameter modes;
the reflection acquisition module is used for acquiring reflection signals of the cable to obtain a reflection signal set, and selecting the most obvious reflection signal in the reflection signal set;
and the defect positioning module is used for detecting the cable defects according to the cable detection algorithm model, the most significant reflected signals and the test signals corresponding to the most significant reflected signals and positioning the positions of the cable defects.
9. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.
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| CN113253062A (en) * | 2021-06-18 | 2021-08-13 | 广东电网有限责任公司佛山供电局 | Power cable fault inspection system based on risk hidden danger |
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