CN112526284A - High-voltage cable fault transient voltage waveform initial characteristic moment extraction method and device - Google Patents
High-voltage cable fault transient voltage waveform initial characteristic moment extraction method and device Download PDFInfo
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Abstract
The application relates to a method and a device for extracting the starting characteristic moment of a high-voltage cable fault transient voltage waveform, computer equipment and a storage medium. The method comprises the following steps: acquiring transient voltage waveform and preset cut-off frequency generated by high-voltage cable faults and acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of a high-voltage cable terminal and a GIS; performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve; extracting local maximum values and maximum values of the wavelet accumulation curves; screening local maximum values larger than a threshold value to obtain a screening result, and determining the initial characteristic moment of the transient voltage waveform according to the screening result; the threshold is determined according to the maximum value. By adopting the method, the initial characteristic moment of the transient voltage waveform of the high-voltage cable fault can be accurately extracted.
Description
Technical Field
The application relates to the technical field of cable fault detection, in particular to a method, a device, computer equipment and a storage medium for extracting the initial characteristic moment of a transient voltage waveform of a high-voltage cable fault.
Background
With the wide use of high-voltage cables, due to the problems of the production process and the installation quality of the high-voltage cables, system capacity increase, long running time and the like, the high-voltage cables have insulation breakdown faults at the high-voltage cable terminals, intermediate joints and high-voltage cable bodies. However, the high-voltage cable is usually installed in an underground cable tunnel, so that inspection and observation by manpower and machines are inconvenient, and in order to shorten the rush-repair time and restore the power supply of the high-voltage cable as soon as possible, the fault position of the high-voltage cable is required to be quickly positioned.
At present, a traveling wave fault location method is generally adopted in a power system in China to obtain the fault position of a high-voltage cable by monitoring the time delay of a transient voltage generated by the fault of the high-voltage cable reaching a monitoring point. However, the transient voltage waveform monitored by the conventional method not only contains reflected waves formed by the transient voltage at a fault point, but also mixes complex reflected waves formed by the transient voltage in a GIS internal component connected with the high-voltage cable, so that the transient voltage waveform is distorted, and finally, the initial characteristic moment of the transient voltage waveform of the high-voltage cable fault cannot be accurately extracted.
Disclosure of Invention
In view of the above, it is necessary to provide a method, an apparatus, a computer device and a storage medium capable of accurately extracting the starting characteristic time of the transient voltage waveform of the high-voltage cable fault in view of the above technical problems.
In a first aspect, a method for starting characteristic time of a transient voltage waveform of a high-voltage cable fault is provided, and the method comprises the following steps:
acquiring transient voltage waveform and preset cut-off frequency generated by high-voltage cable faults and acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of a high-voltage cable terminal and a GIS; performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve; extracting local maximum and maximum of the wavelet accumulation curve; screening local maximum values larger than a threshold value to obtain a screening result, and determining the initial characteristic moment of the transient voltage waveform according to the screening result; the threshold is determined according to the maximum value.
In one embodiment, the starting characteristic time of the transient voltage waveform is the time t when the transient voltage waveform firstly reaches the voltage monitoring point1And the moment t when the transient voltage waveform reaches the voltage monitoring point again after passing through the high-voltage cable terminal and the fault point for the first time2。
In one embodiment, the effective frequency band range of the voltage monitoring point is 10Hz-100MHz, the sampling rate of the voltage monitoring point is not lower than 250Ms/s, and the sampling bandwidth of the voltage monitoring point is not lower than 100 MHz.
In one embodiment, the wavelet accumulation curve is denoted as a (t), and the step of extracting local maxima of the wavelet accumulation curve includes: acquiring the sampling rate of a voltage monitoring point; calculating a sampling time interval delta t according to the sampling rate of the voltage monitoring point; for any time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is a local maximum.
In one embodiment, the expression of the wavelet transform coefficients is:
wherein, CWT (f, t) is a wavelet transform coefficient; u (τ) is the transient voltage waveform; f is the frequency of the transient voltage waveform; τ is the time migration scale; t is time;
as a function of mother wavelet
The function obtained after the stretching and translation transformation is carried out,
is a Morlet function in the mother wavelet function and
c is a normalization constant upon reconstruction.
In one embodiment, the step of performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve includes:
a wavelet accumulation curve is obtained based on the following expression:
wherein, A (t) is a wavelet accumulation curve; p1Is the preset cut-off frequency; CWT (f, t) is the wavelet transform coefficient.
In a second aspect, there is provided a device for extracting the starting characteristic time of a transient voltage waveform of a high-voltage cable fault, the device comprising:
the data acquisition module is used for acquiring transient voltage waveform and preset cut-off frequency which are acquired by a voltage monitoring point and are generated due to high-voltage cable faults, and the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the joint of a high-voltage cable terminal and a GIS; the coefficient acquisition module is used for carrying out continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; the curve acquisition module is used for carrying out frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulated curve; the extreme value acquisition module is used for extracting the local maximum value and the maximum value of the wavelet cumulative curve; the initial characteristic acquisition module is used for screening local maximum values larger than a threshold value to obtain a screening result and determining the initial characteristic moment of the transient voltage waveform according to the screening result; the threshold is determined according to the maximum value.
In one embodiment, the extreme value obtaining module comprises a local maximum value extracting submodule for extracting a local maximum value of the wavelet cumulative curve; the local maximum extraction submodule comprises: a sampling rate acquisition unit: the sampling rate is used for acquiring the voltage monitoring point; the calculating unit is used for calculating a sampling time interval delta t according to the sampling rate of the transient voltage waveform; an analysis unit for analyzing for an arbitrary time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is a local maximum.
In a third aspect, a computer device is provided, which comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the following steps when executing the computer program:
acquiring transient voltage waveform and preset cut-off frequency generated by high-voltage cable faults and acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of a high-voltage cable terminal and a GIS; performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve; extracting local maximum and maximum of the wavelet accumulation curve; local maxima greater than a threshold are screened to determine onset characteristic moments of the transient voltage waveform, the threshold being determined from the maxima.
In a fourth aspect, a computer-readable storage medium is provided, having stored thereon a computer program which, when executed by a processor, performs the steps of:
acquiring transient voltage waveform and preset cut-off frequency generated by high-voltage cable faults and acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of a high-voltage cable terminal and a GIS; performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve; extracting local maximum and maximum of the wavelet accumulation curve; local maxima greater than a threshold are screened to determine onset characteristic moments of the transient voltage waveform, the threshold being determined from the maxima.
Based on the method, the device, the computer equipment and the storage medium for the starting characteristic time of the high-voltage cable fault transient voltage waveform, the starting characteristic time of the high-voltage cable fault transient voltage waveform can be accurately extracted, and the time delay of the transient voltage reaching a voltage monitoring point when the high-voltage cable is in fault can be accurately acquired so as to realize accurate positioning of the cable fault.
Drawings
FIG. 1 is a schematic flow chart illustrating a method for extracting the starting characteristic time of a transient voltage waveform of a fault of a high-voltage cable according to an embodiment;
FIG. 2 is a diagram of an exemplary voltage monitoring point application environment;
FIG. 3 is a schematic diagram of an exemplary transient voltage waveform in one embodiment;
FIG. 4 is a flowchart illustrating a local maximum extraction method for a wavelet accumulation curve according to another embodiment;
FIG. 5 is a schematic diagram of an exemplary onset characteristic of a transient voltage waveform;
FIG. 6 is a block diagram of an exemplary high voltage cable fault transient voltage waveform start feature time extraction device;
FIG. 7 is a block diagram of a local maximum extraction submodule in 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.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items.
In an electric power system, with the wide use of high-voltage cables, because of the problems of the production process and the installation quality of the high-voltage cables, system capacity increase, long running time and other factors, insulation breakdown faults of the high-voltage cables at the high-voltage cable terminals, the middle joints and the high-voltage cable body can be caused, and therefore the power supply of users is interrupted. However, the problems of occupied space and safety of the overhead line are increasingly obvious, the high-voltage cable above 110KV is generally installed in an underground cable tunnel, so that inspection and observation by workers and machines are inconvenient, and in order to shorten the power failure time of a user and reduce the loss caused by power failure, the high-voltage cable fault position is required to be quickly positioned so as to complete the rush repair of the high-voltage cable and the recovery of power supply of the user.
Generally, fault location methods fall into two categories: one is an impedance method based on measuring the impedance of the faulty line and the other is a traveling wave method based on measuring the traveling wave generated by the fault. The impedance method is greatly influenced by factors such as path impedance, line load, power supply parameters and the like, and the high-voltage cable is characterized by a plurality of branches, and the impedance method cannot eliminate false fault points, so the method is not suitable for fault positioning of the high-voltage cable. However, the traveling wave rule is to utilize the transient voltage that will change steeply when the high-voltage cable is in the insulation breakdown fault, and to locate the fault position of the high-voltage cable by utilizing the time delay when the transient voltage waveform generated when the high-voltage cable is in the fault reaches the monitoring point. However, the transient voltage waveform generated when the high-voltage cable obtained in the conventional traveling wave method fails is mixed with the refracted wave generated by the transient voltage among the components of the GIS, so that the transient voltage waveform monitored by the monitoring point is severely distorted, the initial characteristic moment of the transient voltage waveform cannot be accurately determined, and the determined position error of the cable failure is large.
Therefore, the embodiment of the application provides a method and a device for extracting the initial characteristic time of the transient voltage waveform of the high-voltage cable, computer equipment and a storage medium, by which the initial characteristic time of the transient voltage waveform generated when the high-voltage cable has a fault can be accurately obtained, and the method and the device can be used for accurately positioning the fault of the high-voltage cable.
In one embodiment, as shown in fig. 1, a method for extracting starting characteristic time of a transient voltage waveform of a high-voltage cable is provided, and this embodiment is exemplified by applying the method to a terminal, it is to be understood that the method may also be applied to a server, and may also be applied to a system including the terminal and the server, and is implemented by interaction between the terminal and the server. In this embodiment, the method includes the steps of:
and 102, acquiring a transient voltage waveform generated due to a high-voltage cable fault and a preset cut-off frequency acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the joint of a high-voltage cable terminal and a GIS.
As shown in fig. 2, the voltage monitoring point is arranged in the high-voltage cable terminal air chamber at the connection position of the high-voltage cable terminal and the GIS; gis (gas insulated switchgear) is an english abbreviation of gas insulated fully-enclosed switchgear, and is composed of a circuit breaker, a disconnecting switch, an earthing switch, a mutual inductor, a lightning arrester, a bus, a connecting piece, an outgoing line terminal and the like, all of the above devices or components are enclosed in a metal grounded shell, and SF6 insulating gas with a certain pressure is filled in the metal grounded shell, so the gas insulated fully-enclosed switchgear can also be called as SF6 fully-enclosed switchgear.
The voltage monitoring point is used for acquiring transient voltage waveform generated by the high-voltage cable due to faults; the high-voltage cable can be a power cable with transmission voltage not lower than 110KV, and the fault refers to insulation breakdown of the high-voltage cable at a high-voltage cable terminal, a high-voltage cable intermediate joint or a high-voltage cable body caused by problems of a high-voltage cable production process, high-voltage cable installation quality, overlong high-voltage cable operation time, power system capacity increase and the like. When the high-voltage cable has insulation breakdown fault, the transient voltage with steep change edge is generated at the fault point. Because the transmission impedance range of the high-voltage cable is 30-50 omega, and the transmission impedance range of the GIS is 70-100 omega, the transient voltage is obviously refracted and reflected when being transmitted to the high-voltage cable terminal air chamber from a fault point for the first time, and the reflected wave is transmitted back to the fault point; when propagating to the fault point, a full negative reflection in the short circuit situation will occur; the reflected waves will propagate again towards the high voltage cable termination plenum, forming a series of transient voltage traveling waves. Because the transient voltage will have some invasion in GIS and will appear catadioptric phenomenon in the propagation between each component part in GIS when propagating to high tension cable terminal air chamber for the relatively serious distortion of transient voltage waveform of high tension cable trouble that voltage monitoring point gathered.
In one embodiment, the effective frequency band range of the voltage monitoring point is 10Hz-100MHz, the sampling rate of the voltage monitoring point is not lower than 250Ms/s, and the sampling bandwidth of the voltage monitoring point is not lower than 100 MHz. In an alternative embodiment, the voltage monitoring point comprises a broadband voltage sensor. For example, when the voltage detection point satisfies the above condition and the recording length of the single trigger is set to not less than 150us, the voltage detection point may acquire a typical transient voltage waveform as shown in fig. 3; in the embodiment, the accuracy of the transient voltage waveform acquired by the voltage monitoring point is high.
And 104, performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform.
After the transient voltage waveform acquired by the voltage monitoring point and generated due to the fault of the high-voltage cable is acquired, the frequency information of the transient voltage waveform is contained in the transient voltage waveform. And then, performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform. The continuous wavelet transform is a linear transform and has the properties of superposition, time-shift invariance, expansion covariance, self-similarity, redundancy and the like. The expression of the wavelet transform coefficients of the transient voltage waveform is:
wherein, CWT (f, t) is a wavelet transform coefficient; u (τ) is the transient voltage waveform; f is the frequency of the transient voltage waveform; τ is the time migration scale; t is time;
as a function of mother wavelet
And performing stretching and translation transformation to obtain the function.
In one embodiment, a mother wavelet function in a continuous wavelet transform
Is a Morlet wavelet function. Wherein the expression of Morlet wavelet function is
C is a normalization constant during reconstruction; in the present embodiment, the Morlet wavelet function is a single-frequency negative sine modulation gaussian wave, and is also a non-orthogonal wavelet and replica wavelet, which has no scale function, has the characteristics of fast attenuation but not tight support, and has good locality in the time-frequency two-domain.
106, performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulated curve;
and performing frequency domain analysis according to the acquired preset cut-off frequency and the wavelet transform coefficient to obtain a wavelet accumulation curve. In one embodiment, the step of performing frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulation curve includes: the wavelet accumulation curve is obtained based on the following expression:
wherein, A (t) is a wavelet accumulation curve; p1Is a preset cut-off frequency; CWT (f, t) is the wavelet transform coefficient. In a preferred embodiment, the preset cut-off frequency P1Is 20 MHz.
And step 108, extracting local maximum values and maximum values of the wavelet accumulation curve.
When a mathematical analysis method is adopted to process the wavelet accumulation curve, if the function corresponding to the expression wavelet accumulation curve has a certain value in a neighborhood of a certain point, and the value at the point is the maximum, the value of the function corresponding to the expression wavelet accumulation curve at the point is a local maximum. The maximum value of the wavelet accumulation curve is the maximum value in the function value domain corresponding to the wavelet accumulation curve.
In one embodiment, as shown in fig. 4, this embodiment provides a technical process for extracting local maxima of a wavelet accumulation curve, which may include the following steps:
step 402, acquiring the sampling rate of a voltage monitoring point;
acquiring the sampling rate of a voltage monitoring point; the sampling rate, also referred to as the sampling rate or sampling frequency, generally refers to the number of samples per second that are extracted from a continuous signal and constitute a discrete signal.
Step 404, calculating a sampling time interval delta t according to the sampling rate of the voltage monitoring point;
calculating a sampling time interval delta t according to the obtained sampling rate of the voltage monitoring point; wherein the sampling time interval Δ t is related to the sampling rate of the voltage monitoring points. In one embodiment, the expression for the sample interval Δ t is:
wherein, F is the sampling rate of the voltage monitoring point.
Step 406, for any time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is the local maximum of the wavelet accumulation curve.
At any time t in the wavelet accumulation curveiWhile satisfying A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), a (t) can be determinedi) Is the local maximum of the wavelet accumulation curve.
In this embodiment, the sampling time interval Δ t of the voltage monitoring point is calculated according to the obtained sampling rate of the voltage monitoring point, and the local maximum of the wavelet accumulation function can be automatically and accurately determined through a series of comparison processes.
Step 110, screening local maximum values larger than a threshold value to obtain a screening result, and determining an initial characteristic moment of the transient voltage waveform according to the screening result; wherein, the threshold value is determined according to the maximum value of the wavelet accumulation curve.
Screening the local maximum values which are larger than the threshold value to determine the initial characteristic moment of the transient voltage waveform; the threshold is determined according to the maximum value of the wavelet accumulation curve, and is generally in direct proportion to the maximum value of the wavelet accumulation curve. In one embodiment, the threshold may be 0.2 times the maximum of the cumulative wavelet curve, as measured by theoretical experiments.
In one embodiment, the starting characteristic time of the transient voltage waveform is the time t when the transient voltage waveform first reaches the voltage monitoring point1And the moment t when the transient voltage waveform firstly passes through the high-voltage cable terminal and the fault point and then reaches the voltage monitoring point again2. For example, as shown in FIG. 5, M11、M12、M13、M21、M22And M23The initial characteristic moment of the transient voltage waveform can be determined for the retained local maximum value of the wavelet accumulated curve which is larger than the threshold value through screening and analysis; wherein the first point M11 in fig. 5 corresponds to the time t at which the transient voltage waveform first reaches the voltage monitoring point1Fourth point M in FIG. 521Correspondingly, the transient voltage waveform reaches the voltage monitoring point again after passing through the high-voltage cable terminal and the fault point for the first time at the moment t2. In this embodiment, the local maximum values larger than the threshold are filtered to obtain the filtering result, and the initial characteristic time t of the transient voltage waveform can be accurately obtained according to the filtering result1And t2By obtaining the starting characteristic time t of the transient voltage waveform1And t2And calculating to accurately obtain the time delay of the transient voltage reaching the voltage monitoring point when the high-voltage cable has a fault so as to realize the accurate positioning of the cable fault.
According to the high-voltage cable fault transient voltage waveform starting characteristic time method, the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of the high-voltage cable terminal and the GIS, and the transient voltage waveform generated due to the high-voltage cable fault and collected by the voltage monitoring point and the preset cut-off frequency are obtained; performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform; then, carrying out frequency domain analysis according to a preset cut-off frequency and a wavelet transform coefficient to obtain a wavelet accumulated curve; and finally, extracting local maximum values and maximum values of the wavelet accumulation curve, screening the local maximum values larger than a threshold value to obtain a screening result, and determining the initial characteristic moment of the transient voltage waveform according to the screening result. Based on the method, the device, the computer equipment and the storage medium for the initial characteristic time of the high-voltage cable fault transient voltage waveform, under the condition that the acquired high-voltage cable fault transient waveform is mixed with complex reflected waves formed by transient voltages in GIS internal components connected with a high-voltage cable, the initial characteristic time of the high-voltage cable fault transient voltage waveform can be accurately extracted and used for accurately acquiring the time delay of the transient voltages reaching voltage monitoring points when the high-voltage cable is in fault so as to realize accurate positioning of cable faults.
It should be understood that although the steps in the flowcharts of fig. 1 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. 1 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. 6, there is provided a high voltage cable fault transient voltage waveform start characteristic time extracting apparatus 1000, including: a data acquisition module 1100, a coefficient acquisition module 1200, a curve acquisition module 1300, an extremum acquisition module 1400, and an initial characteristic acquisition module 1500, wherein:
the data acquisition module 1100 is configured to acquire a transient voltage waveform and a preset cut-off frequency, which are acquired by a voltage monitoring point and are generated due to a high-voltage cable fault, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at a connection position of a high-voltage cable terminal and a GIS.
And the coefficient acquisition module 1200 is configured to perform continuous wavelet transform on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transform coefficient of the transient voltage waveform.
And the curve obtaining module 1300 is configured to perform frequency domain analysis according to the preset cut-off frequency and the wavelet transform coefficient to obtain a wavelet accumulation curve.
And an extreme value obtaining module 1400, configured to extract local maximum values and maximum values of the wavelet cumulative curve.
An initial characteristic obtaining module 1500, configured to screen local maxima greater than a threshold to obtain a screening result, and determine an initial characteristic time of the transient voltage waveform according to the screening result; the threshold value is determined according to the maximum value of the wavelet accumulation curve.
In one embodiment, as shown in fig. 7, the extremum obtaining module 1400 includes a local maximum extracting submodule 1410 and is configured to extract local maxima of the wavelet accumulation curve; the local maximum extraction submodule 1410 includes: sample rate acquisition unit 1411: the sampling rate is used for acquiring the voltage monitoring point; a calculating unit 1412, configured to calculate a sampling time interval Δ t according to the sampling rate of the transient voltage waveform; an analysis unit 1413 for any time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is a local maximum.
For specific definition of the device for extracting the initial characteristic time of the high-voltage cable fault transient voltage waveform, reference may be made to the above definition of the method for extracting the initial characteristic time of the high-voltage cable fault transient voltage waveform, and details are not described herein again. The modules in the device for extracting the initial characteristic moment of the transient voltage waveform of the high-voltage cable fault 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 terminal, and its internal structure diagram may be as shown in fig. 8. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device 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 and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless communication can be realized through WIFI, an operator network, NFC (near field communication) or other technologies. The computer program is executed by a processor to realize a high-voltage cable fault transient voltage waveform starting characteristic time extraction method. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
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 further provided, which includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method embodiments when executing the computer program.
In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method embodiments.
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 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-mentioned embodiments 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 extracting starting characteristic time of a transient voltage waveform of a high-voltage cable fault is characterized by comprising the following steps:
acquiring transient voltage waveform and preset cut-off frequency generated by high-voltage cable faults and acquired by a voltage monitoring point, wherein the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the connection position of a high-voltage cable terminal and a GIS;
performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform;
performing frequency domain analysis according to the preset cut-off frequency and the wavelet transform coefficient to obtain a wavelet accumulation curve;
extracting local maximum values and maximum values of the wavelet accumulation curves;
screening the local maxima greater than a threshold value to obtain a screening result, and determining an initial characteristic time of the transient voltage waveform according to the screening result; the threshold value is determined according to the maximum value.
2. The method according to claim 1, wherein the start characteristic time of the transient voltage waveform is a time t when the transient voltage waveform first reaches the voltage monitoring point1And the moment t when the transient voltage waveform firstly passes through the high-voltage cable terminal and the fault point and then reaches the voltage monitoring point again2。
3. The method for extracting the initial characteristic moment of the transient voltage waveform of the high-voltage cable fault according to claim 1, wherein the effective frequency band range of the voltage monitoring point is 10Hz-100MHz, the sampling rate of the voltage monitoring point is not lower than 250Ms/s, and the sampling bandwidth of the voltage monitoring point is not lower than 100 MHz.
4. The method according to claim 1, wherein said wavelet accumulation curve is denoted as a (t), and the step of extracting said local maxima comprises:
acquiring the sampling rate of the voltage monitoring point;
calculating a sampling time interval delta t according to the sampling rate of the voltage monitoring point;
for any time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is the local maximum.
5. The method for extracting the starting characteristic time of the transient voltage waveform of the high-voltage cable fault according to claim 1, wherein the expression of the wavelet transformation coefficient is as follows:
wherein CWT (f, t) is the wavelet transform coefficient; u (τ) is the transient voltage waveform; f is the frequency of the transient voltage waveform; τ is the time migration scale; t is time;
as a function of mother wavelet
Function obtained after performing stretching and translation transformation，
Is a Morlet function in the mother wavelet function and
c is a normalization constant upon reconstruction.
6. The method for extracting the initial characteristic time of the transient voltage waveform of the high-voltage cable fault according to claim 1, wherein the step of performing frequency domain analysis according to the preset cut-off frequency and the wavelet transform coefficient to obtain a wavelet accumulation curve comprises:
the wavelet accumulation curve is obtained based on the following expression:
wherein A (t) is the wavelet accumulation curve; p1Is the preset cut-off frequency; CWT (f, t) is the wavelet transform coefficient.
7. A high voltage cable fault transient voltage waveform starting characteristic time extraction device is characterized by comprising:
the data acquisition module is used for acquiring transient voltage waveform and preset cut-off frequency which are acquired by a voltage monitoring point and are generated due to high-voltage cable faults, and the voltage monitoring point is arranged in a high-voltage cable terminal air chamber at the joint of a high-voltage cable terminal and a GIS;
the coefficient acquisition module is used for performing continuous wavelet transformation on the transient voltage waveform according to the frequency of the transient voltage waveform to obtain a wavelet transformation coefficient of the transient voltage waveform;
the curve acquisition module is used for carrying out frequency domain analysis according to the preset cut-off frequency and the wavelet transform coefficient to obtain a wavelet accumulated curve;
the extreme value acquisition module is used for extracting a local maximum value and a maximum value of the wavelet cumulative curve;
and the initial characteristic acquisition module is used for screening the local maximum values larger than a threshold value to obtain a screening result, determining the initial characteristic moment of the transient voltage waveform according to the screening result, and determining the threshold value according to the maximum value.
8. The apparatus according to claim 7, wherein the extreme value obtaining module comprises a local maximum value extracting sub-module for extracting local maximum values of the wavelet cumulative curve;
the local maximum extraction sub-module includes:
a sampling rate acquisition unit: the sampling rate is used for acquiring the voltage monitoring point;
a calculating unit for calculating a sampling time interval Δ t according to a sampling rate of the transient voltage waveform;
an analysis unit for analyzing for an arbitrary time tiIf A (t)i)>A(ti+Δt)>A(ti+2Δt)>A(ti+3Δt)>A(ti+4Δt)>A(ti+5 Δ t) and A (t)i)>A(ti-Δt)>A(ti-2Δt)>A(Ti-3Δt)>A(ti-4Δt)>A(ti-5 Δ t), then a (t) is determinedi) Is the local maximum.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method of any of claims 1 to 6.
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 6.
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