CN107942198A - A kind of apparatus and method of the cable local defect assessment based on impedance spectrum analysis - Google Patents

A kind of apparatus and method of the cable local defect assessment based on impedance spectrum analysis Download PDF

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Publication number
CN107942198A
CN107942198A CN201711154670.9A CN201711154670A CN107942198A CN 107942198 A CN107942198 A CN 107942198A CN 201711154670 A CN201711154670 A CN 201711154670A CN 107942198 A CN107942198 A CN 107942198A
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China
Prior art keywords
mrow
signal
cable
msub
tested
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Inventor
惠兆宇
刘韬
魏巍
池志远
王春晖
安英辉
李晓蔚
张涛
刘士立
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China General Nuclear Power Corp
CGN Power Co Ltd
Daya Bay Nuclear Power Operations and Management Co Ltd
Guangdong Nuclear Power Joint Venture Co Ltd
Suzhou Nuclear Power Research Institute Co Ltd
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China General Nuclear Power Corp
CGN Power Co Ltd
Daya Bay Nuclear Power Operations and Management Co Ltd
Guangdong Nuclear Power Joint Venture Co Ltd
Suzhou Nuclear Power Research Institute Co Ltd
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Application filed by China General Nuclear Power Corp, CGN Power Co Ltd, Daya Bay Nuclear Power Operations and Management Co Ltd, Guangdong Nuclear Power Joint Venture Co Ltd, Suzhou Nuclear Power Research Institute Co Ltd filed Critical China General Nuclear Power Corp
Priority to CN201711154670.9A priority Critical patent/CN107942198A/en
Publication of CN107942198A publication Critical patent/CN107942198A/en
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08Locating faults in cables, transmission lines, or networks
    • G01R31/081Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/083Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)

Abstract

Measurement and analysis technical field the present invention relates to transmission line impedance frequency spectrum, the apparatus and method assessed more particularly to a kind of cable local defect based on impedance spectrum analysis, described device includes at least signal generating unit, signal gathering unit, analysis controlling unit and data storage cell, launch incoming signal and there is identical amplitude and phase for transmitted reference signal, the incoming signal and the reference signal in one end that signal generating unit is used for tested cable;The signal gathering unit is used for synchronous the collection incoming signal and reflected signal, the reflected signal is the signal by tested cable back reflection by the incoming signal, the present invention measures and calculates the frequency spectrum that cable resistance is tested in frequency sweep section by frequency sweeping method, and spectral function is converted in frequency domain, the positioning to defect is realized in neofield after the conversion and assesses its order of severity, it is of the invention compared with existing cable fault location technology, noise immunity is strong, applicability is wide, can be achieved qualitative assessment.

Description

A kind of apparatus and method of the cable local defect assessment based on impedance spectrum analysis
Technical field
Measurement and analysis technical field the present invention relates to transmission line impedance frequency spectrum, and in particular to one kind is surveyed by frequency spectrum The apparatus and method that amount, frequency-domain transform and analysis are assessed so as to fulfill cable local defect.
Background technology
Transmission line is the linear structure for conveying electromagnetic energy, and between signal source and load, cable is a kind of typical biography Defeated line.Transmission line theory is the theory of a set of comparative maturity, more applied to professional domains such as communication engineering, electronic circuits. The characteristic of transmission line depends on the difference between its length and the wavelength of carried electric signal, when length of transmission line is much smaller than letter During number wavelength, transmission line hardly influences the behavior of electric loop, at this time in terms of signal source, line impedance ZinWith load Impedance is equal;But when length of transmission line is more than electric signal wavelength, transmission line will produce shadow to the behavior of electric loop Ring, at this time in terms of signal source, except some special circumstances, line impedance is different from load impedance.
Cable as transmission line, along its length on voltage vector V and current phasor I obey the following differential equation:
Wherein ω is the radial frequency of signal, and R is conductor resistance, and L is inductance, and C is capacitance, and G is insulated electrical conductivity, rear four A electric parameter is numerical value of the cable under unit length.Cable, which can be completely portrayed, using this four electric parameters is passed through height Behavioural characteristic during frequency signal.In transmission line theory, the behavior of transmission line described usually using two complex functions, first It is equation of transfer:
Usually write a Chinese character in simplified form into following form:
γ=α+j β (0-04)
Wherein real part α is known as attenuation constant, and imaginary part β is known as transmission constant, phase velocity ν, the radial frequency ω of β and signal and The relation of wavelength X is as follows:
Second is characteristic impedance:
(0-03)~(0-06) formulas are substituted into differential equation group (0-01) and (0-02), can must be from cable one end along length side It is to the relevant impedance expressions of d:
Wherein ΓdIt is as follows for GENERALIZED REFLECTION COEFFICIENT, expansion:
ΓdL·e-2γd (0-08)
Wherein ΓLIt is as follows for load reflection coefficient, expansion:
Wherein ZLFor cable termination load impedance.
It is any in random length from equation (0-07)~(0-09) it can be seen that when load matches with characteristic impedance Under frequency, there is ΓLd=0, Zd=Z0=ZL.Transmission line impedance can be described by formula (0-07), it is a complex variable, The curve that amplitude and phase change with signal frequency is as shown in Figure 1.
The existing method that positioning cable local defect is attempted based on transmission line theory, using the incoming signal of fixed frequency, By measure the voltage vector V in equation (0-01) change with time determine between incoming signal and reflected signal when Prolong.But at the scene under the conditions of, signal decay in the cable and ambient noise are (especially for length more than 1000 meters Cable) limit the sensitivity of this method, it is difficult to the A-stage of cable local defect is detected, it is even more impossible to reflect part The development trend of defect.
Cable local defect appraisal procedure based on impedance spectrum analysis lacks related work at home, still lacks dedicated Research device and technology.
The content of the invention
The present invention provides a kind of device of the cable local defect assessment based on impedance spectrum analysis, using modular construction Design, for completing the measurement, calculating and analysis of cable resistance frequency spectrum, so as to position the local defect in tested cable and assessment Its order of severity.
To reach above-mentioned purpose, the technical solution adopted by the present invention is:A kind of cable based on impedance spectrum analysis is local The device of defect estimation, described device include at least:
Signal generating unit, it is used for the sine wave signal for producing assigned frequency, wherein being used as all the way to tested cable one The incoming signal of transmitting is held, for another way as signal is referred to, the incoming signal and the reference signal have identical amplitude And phase;
Signal gathering unit, it, which has, is used to gathering the first acquisition channel of the reference signal and anti-for synchronous acquisition The second acquisition channel of signal is penetrated, wherein, the reflected signal is to pass through the tested cable back reflection by the incoming signal Signal;
Analysis controlling unit, it communicates be connected respectively with the signal generating unit and the signal gathering unit, bag The control module being controlled to the signal frequency of the incoming signal and the reference signal and duration is included, and it is right The data analysis module that the reflected signal that the signal gathering unit collects is handled with the reference signal;
Analysis controlling unit, it communicates be connected respectively with the signal generating unit and the signal gathering unit, bag The control module being controlled to the launch time of the incoming signal and the reference signal and signal frequency is included, and it is right The data analysis module that the reflected signal that the signal gathering unit collects is handled with the reference signal;
Data storage cell, it communicates to connect with the analysis controlling unit and is got with storing the analysis controlling unit Signal data and analyzing and processing result data.
Further, described device is further included is used to send and receive data with data storage cell communication connection Communication unit.
Further, described device further include respectively with the analysis controlling unit, the data storage cell and described The man-machine interaction unit that communication unit communicates to connect respectively, the man-machine interaction unit have human-computer interaction interface and display circle Face, for receiving the information of input and showing information by the display interface.
Further, the incoming signal and the reference signal are the frequency-swept sine wave signal not higher than 100MHz, institute It is two-channel digital oscillograph to state signal gathering unit.
The present invention also provides a kind of method of the cable local defect assessment based on impedance spectrum analysis, including following step Suddenly:
(1) incoming signal and the reference signal are produced using the signal generating unit, the incoming signal from One end of the tested cable is injected, and the incoming signal is gathered using first acquisition channel of the signal gathering unit Reflected signal after the tested cable, it is synchronous, adopted using second acquisition channel of the signal gathering unit Collect the reference signal;
(2) impedance of the tested cable in frequency sweep section is calculated according to the reflected signal and the reference signal;
(3) a new domain conversion is defined, the frequency spectrum function for the impedance that step (2) is calculated is transformed to along the quilt Survey the power spectrum function in cable length direction;
(4) by power spectrum function described in step (3) more than 0dB point be considered as along the tested cable length direction because Echo discontinuously is generated there are electric property, the discontinuous position of electric property is the part of the tested cable Defective locations.
Further, in the step (2), the impedance computation method of the tested cable is as follows:
Wherein, ZDUTIt is the impedance of the tested cable, Z1It is to lead to for gathering described the first of the reflected signal and gathering The impedance in road, V1For the voltage vector value measured at first acquisition channel, V0For the electricity measured at second acquisition channel Press vector value.
Further, in the step (3), the frequency spectrum function being calculated is transformed to the method for power spectrum function such as Under:
f→t′ (1-02)
Wherein, νr=ν/ν0
F is the frequency of the incoming signal, and f is independent variable;
D is the length of tested cable;
ν is the phase velocity that the incoming signal is propagated in the tested cable;
νrIt is relative phase velocity of the incoming signal in the tested cable;
ν0It is the spread speed of light in a vacuum.
Further, the localization method of defective locations is as follows in the step (4):
The frequency f ' of the function in t ' domains is calculated,
F ' is the fundamental frequency of phase function in t ' domains, and the incoming signal is passed from the incidence point of the tested cable Cast to after the terminal of the tested cable and return again to the time of the incidence point;
When, to produce echo there are during local defect, at this at x, making the power of impedance phase apart from incidence point distance A new frequency component is produced in spectrum, this frequency is:
By identifying the f ' in the impedance phase power spectrum and f " in t ' domains, calculate since electric parameter is discontinuous and Produce the position of echo:
The distance of the defects of above-mentioned x being calculated is tested cable incidence point described in positional distance.
Further, when the tested cable has multiple local defects along its length, each defective locations are right A frequency component in power spectrum has been answered, has passed through frequency component fnCalculate the defects of corresponding position xn
The above-mentioned x being calculatednAs frequency component fnThe distance between the defects of corresponding and the incidence point.
Further, the appraisal procedure further includes following steps:(5) rejected region is found out in power spectrum chart in the quilt The mirror image peak that the opposite side of cable termination produces is surveyed, wherein, position where the mirror image peak to the tested cable termination Distance is equal with the distance of rejected region to the tested cable termination, and the summit of rejected region and mirror image peak summit are used Straight line is connected the Trendline to decay as echo-signal along the tested cable length direction, the Trendline with described There is an intersection point in tested cable termination position between longitudinal auxiliary line of abscissa, uses the intersection point and terminal peak peak The distance between value is used for the order of severity for assessing the cable local defect.
After the above technical solution is adopted, the present invention has the following advantages that compared with prior art:
1st, Non-Destructive Testing.The usable voltage as low as incoming signal of 5V of the present invention is detected, and will not damage tested cable And terminal load.
2nd, noise immunity is strong.The impedance computation method that the present invention uses is filtered by window function, can be effectively eliminated existing Influence of the field noise to measurement result.
3rd, range of applicability is wide.The present invention is suitable for various types of cables, particularly coaxial cable and metal armouring list Core power cable.The present invention is suitable for cable of the length from 20 meters to thousands of meters, can be the electric power enterprises such as power plant and power transmission and distribution Technical support is provided.
4th, assembling is simple, suitable for live adverse circumstances.The present invention uses Modular Structure Design, and signal therein occurs The commercial product module such as vector network analyzer and digital oscilloscope, system control sum number can be used in unit and signal gathering unit It can realize that device integrated level is higher, can be used under condition more rugged environment in PC machine by being programmed according to analysis.
5th, assessment result quantification.The present invention can be accurately positioned cable local defect, while can qualitative assessment defect The order of severity, has high application value in cable aging management and prospective maintenance activity.
Brief description of the drawings
Attached drawing 1 is transmission line (cable) impedance schematic diagram in the technical background of the present invention;
Attached drawing 2 is the construction module figure of detection device in the present invention;
Attached drawing 3 measures wiring diagram to be tested cable resistance in the present invention;
Attached drawing 4 is the tested power spectrum chart of cable along its length;
Attached drawing 5 is the computational methods schematic diagram of the tested cable local defect order of severity.
Wherein, 1, signal generating unit;2nd, signal gathering unit;3rd, analysis controlling unit;4th, data storage cell;5th, lead to Interrogate unit;6th, man-machine interaction unit;7th, it is tested cable.
Embodiment
The invention will be further described with reference to the accompanying drawings and embodiments.
A kind of device of the cable local defect assessment based on impedance spectrum analysis, as shown in Figure 2, including at least signal Generating unit 1, signal gathering unit 2, analysis controlling unit 3 and data storage cell 4.
Signal generating unit 1 is used for the sine wave signal for producing assigned frequency, which is divided into two-way, wherein All the way as the incoming signal CH0 ' launched to tested cable one end, another way as referring to signal CH0, incoming signal CH0 ' and Reference signal CH0 has identical amplitude and phase.
Signal gathering unit 2 is anti-with the first acquisition channel for being used to gather reference signal CH0 and for synchronous collection The second acquisition channel of signal CH1 is penetrated, reflected signal CH1 is the signal by 7 back reflection of tested cable by incoming signal CH0 '.
Analysis controlling unit 3 communicates respectively with signal generating unit 1 and signal gathering unit 2 to be connected, analysis and Control list Member 3 includes the control module being controlled to the signal frequency of reference signal CH0 and incoming signal CH0 ' and duration, with And the data analysis module that the reference signal CH0 collected to signal gathering unit 2 and reflected signal CH1 is handled.
Data storage cell 4 is used to store data with the communication connection of analysis controlling unit 3.In the present embodiment, data storage Unit 4 is tested information, the data detected and the analysis result of cable 7 using rational data structure storage, and has history Data retrieval function.
In the present embodiment, reference signal CH0 and incoming signal CH0 ' are that frequency-swept sine wave of the frequency not higher than 100MHz is believed Number.
In the present embodiment, signal gathering unit 2 is two-channel digital oscillograph.
In the present embodiment, which further includes communication unit 5 and man-machine interaction unit 6, the association between each unit module Referring to shown in attached drawing 2.
Communication unit 5 is communicated to connect with data storage cell 4, for sending and receiving data so that the device of the application Data exchange and sharing can be realized with other devices.
Man-machine interaction unit 6 communicates to connect respectively with analysis controlling unit 3, data storage cell 4 and communication unit 5, people Machine interactive unit 6 has human-computer interaction interface and display interface, for receiving information and the detection of tested cable 7 input by user Instruction, and show the analysis data such as the power spectrum chart of the impedance spectrum figure of tested cable 7, tested cable 7, and provide currently with going through The data comparative result of history.
During practical operation, the swept frequency range and number of scan points of reference signal CH0 and incoming signal CH0 ' are specified by operator, Such as 1~100MHz of swept frequency range is set, frequency sweep points are 1000000, then the stepping of incoming signal CH0 ' and reference signal CH0 Frequency is followed successively by 1Hz, and each frequency of 100Hz, 200Hz, 300Hz, 400Hz ... ... at least continues the sine of 10 complete cycles Ripple.In order to ensure the precision of testing result, sample frequency should be greater than 100 times of reference signal frequency.
The present invention also provides, to carry out the method for cable local defect assessment, included the following steps using above device:
(1) using signal generating unit 1 launch incoming signal CH0 ' and reference signal CH0, incoming signal CH0 ' from be tested One end of cable 7 is injected, using the first acquisition channel collection incoming signal CH0 ' of signal gathering unit 2 by tested cable 7 Reflected signal CH1 afterwards, it is synchronous, using the second acquisition channel collection reference signal CH0 of signal gathering unit 2;
(2) impedance that cable 7 is tested in frequency sweep section is calculated according to reflected signal CH1 and reference signal CH0;
(3) a new domain conversion is defined, the frequency spectrum function for the impedance that step (2) is calculated is transformed to along tested electricity The power spectrum function of 7 length direction of cable;
(4) point of the power spectrum function in step (3) more than 0dB is considered as along tested 7 length direction of cable because there is electricity Gas performance is discontinuous and generates echo, and the discontinuous position of electric property is the local defect position of tested cable.
Reference signal CH0 is selected from ω1To ω2Swept-frequency signal, ω2Determine depend on the length of tested cable 7, one As, tested cable 7 is shorter, ω2Value is bigger;Reflected signal CH1 is impedances of the incoming signal CH0 ' by tested cable 7 ZDUTSignal afterwards, its amplitude and phase are changed;The tested electricity calculated using reflected signal CH1 and reference signal CH0 The impedance Z of cable 7DUT, it is the function of the frequency of incoming signal CH0 ', and calculation formula is as follows:
Wherein, ZDUTIt is the impedance of tested cable 7, Z1It is the resistance for gathering the first acquisition channel of reflected signal CH1 It is anti-, 20 ohm or 50 ohm can be selected according to tested 7 characteristic impedance of cable;V1For the voltage vector measured at the first acquisition channel Value;V0For the voltage vector value measured at the second acquisition channel.
As shown in Figure 3, wherein Rb is the internal resistance of signal generating unit 1 to measuring circuit schematic diagram, and Rg is posting on circuit Raw impedance.Above formula (1-01) shows ZDUTIt is unrelated with resistance Rb and Rg, ZDUTOnly it is a V0To V1Transmission function.
By selecting appropriate window function (such as Hamming window) to eliminate noise, can be calculated in frequency sweep section according to formula (1-01) ω1To ω2Between be tested the frequency spectrum of cable 7 impedance.
According to the impedance spectral function of tested cable 7, following parameter can be calculated:
(1) resonant frequency, is the frequency values at zero in impedance phase angle.
(2) impedance Z of tested cable 7 is calculatedDUT, at any local maximum (or minimum value) place pair of impedance phase angle Answer the amplitude of impedance.
The present invention also provides one kind by being tested 7 impedance Z of cableDUTTo position the side of tested 7 local defect position of cable Method.
Formula (0-07) is the complex function expression formula of attached drawing 1, shown in figure impedance amplitude and phase with incoming signal The change of CH0 ' frequencies.The pseudo-periodicity of impedance spectral function is derived from ΓdPeriodicity, ΓdEquation (0-08) can also be write For:
ΓdL·e-2γdL·e-2αd·e-2jβd (0-10)
Due to attenuation coefficient α, the amplitude of impedance declines along cable length d.If during using d as independent variable, ΓdPseudoperiod For 1/2 β.
Equation (0-05) is substituted into equation (0-10) has
Wherein f is the frequency of incoming signal CH0 ', and ν is the phase velocity that signal is propagated in tested cable 7.F is set to be independent Variable, defines a new conversion:
f→t′ (1-02)
Wherein νr=ν/ν0, νrThe relative phase velocity for being incoming signal CH0 ' in tested cable 7, ν0Be light in a vacuum Spread speed.
By ΓL·e-2αdA is set to, then equation (0-11) is transformed to through t ':
Γd=Ae-jω′t′ (0-12)
Formula (0-12) gives the pseudo-periodic function that a radial frequency is ω ' and amplitude is A.In actual lossy quilt Survey in cable 7, the attenuation coefficient α A that to shake successively decrease with t ', so as to produce such as the damped oscillation in attached drawing 1.In t ' domains, the letter Several frequency f ' are:
Wherein f ' is the fundamental frequency of phase function in t ' domains, and incoming signal CH0 ' propagates to tested electricity from incidence point The time of incidence point is returned again to after 7 terminal d of cable, therefore f ' also has time dimension.As shown in Figure 4, in t ' domains, impedance phase The fundamental frequency f ' provided in equation (1-04) has been corresponded at the terminal d of Fourier transformation (power spectrum) transverse axis of position.
There are local defect at the tested 7 incidence point x of cable of distance (it is discontinuous to be usually expressed as electric parameter, such as absolutely Minor variations occur for the dielectric property of edge) when, another echo will be produced at this, this can be produced in the power spectrum of impedance phase One new frequency component, according to equation (1-04), this frequency is:
If it is known that 7 length d of tested cable, by identifying the f ' in impedance phase power spectrum and f " in t ' domains, according to Equation (1-04) and (1-05), can calculate position of the cable there are electric discontinuity (i.e. at x):
It can be calculated by above method and any the position of echo, transmission line be produced due to electric parameter discontinuity The frequency component outside place's fundamental frequency in impedance spectral function all characterizes some position and generates echo.As shown in Figure 4, In t ' domains, at the x of the power spectrum transverse axis of impedance phase (i.e. at incidence point x) because tested cable 7 there are electric parameter not It is continuous and there occurs echo.
When carrying out status monitoring to tested cable 7, it will usually calculate the discontinuous position of some electric parameters, each Position has all corresponded to a frequency component f in power spectrumn, the defects of corresponding position x is calculated according to following methodsn
The above-mentioned x being calculatednAs frequency component fnThe distance between the defects of corresponding and the incidence point.
The present invention also provides a kind of method for assessing the 7 local defect order of severity of tested cable.Power as shown in Figure 4 Any spike higher than 0dB can assert that there are local defect for its position in spectrum.But the peak value at this cannot be used directly In the order of severity of assessment local defect, because peak value can also be by defect point and the distance of incidence point, signal in tested cable 7 Decay and swept-frequency signal bandwidth influence.
A state index DNORM (degree of normalized degradation) is defined to be used to assess tested electricity The order of severity of 7 defect of cable.Attached drawing 5 gives the definition of DNORM using power spectrum:Spike at any local defect is all A mirror image peak can be produced in the opposite side of tested 7 terminal of cable, this mirror image peak be by fault location and tested 7 terminal of cable it Between secondary reflection produce, the distance between position and tested 7 terminal of cable where the mirror image peak and local defect and quilt It is equal to survey the distance between 7 terminal of cable, it is known that tested 7 length of cable is d, and the position of local defect is x, then this mirror image peak The distance of distance 7 incidence point of tested cable is 2 × d-x.The summit at peak that defective locations produce passes through one with the summit at mirror image peak Bar straight line is connected, and the slope of the straight line is for characterizing the variation tendency of the amplitude of echo peak longitudinally along the cable.If TP is quilt Survey 7 terminal of cable peak value, DNORM be defined as defect peak along Trendline to terminal peak at and TP difference.This method can have Attenuation of the echo produced at compensating defective along 7 length direction of tested cable is imitated, the absolute value of DNORM is bigger, then shows to lack The echo that sunken place produces is stronger, and defect is more serious.DNORM absolute values are usually more than 10 as tested 7 local defect of cable Criterion.To same root cable, the DNORM that different time detects can be used for the degradation trend for tracking rejected region.
Referring to attached drawing 4 and attached drawing 5, in the present embodiment, the length for being tested cable 7 is d=30.5 meters, measures local defect Position and incidence point x=22.3 meters of distance, then the position at mirror image peak be 2 × d-x=38.7 meter, connect power spectrum chart in horizontal stroke Coordinate is that the summit at two peaks at 22.3 meters and 38.7 meters forms Trendline, and DNORM is defined as at abscissa is 30.5 meter, should The difference of the peak value of Trendline and cable termination on the vertical scale.
The present invention measures and calculates the frequency spectrum that 7 impedance of cable is tested in frequency sweep section by frequency sweeping method, and right in frequency domain Spectral function is converted, and the positioning to defect is realized in neofield, of the invention compared with existing cable fault location technology, is resisted Making an uproar property is strong, applicability is wide, and can assess the order of severity of 7 defect of tested cable.
The above embodiments merely illustrate the technical concept and features of the present invention, and its object is to allow person skilled in the art Scholar can understand present disclosure and implement according to this, and it is not intended to limit the scope of the present invention.It is all according to the present invention The equivalent change or modification that Spirit Essence is made, should be covered by the protection scope of the present invention.

Claims (10)

1. a kind of device of the cable local defect assessment based on impedance spectrum analysis, it is characterised in that described device is at least wrapped Include:
Signal generating unit, it is used for the sine wave signal for producing assigned frequency, wherein being sent out all the way as to tested cable one end The incoming signal penetrated, for another way as signal is referred to, the incoming signal and the reference signal have identical amplitude and phase Position;
Signal gathering unit, it, which has the first acquisition channel for being used for gathering the reference signal and is reflected for synchronous acquisition, believes Number the second acquisition channel, wherein, the reflected signal be by the incoming signal pass through the tested cable back reflection letter Number;
Analysis controlling unit, it communicates be connected respectively with the signal generating unit and the signal gathering unit, including right The control module that the signal frequency and duration of the incoming signal and the reference signal are controlled, and to described The data analysis module that the reflected signal that signal gathering unit collects is handled with the reference signal;
Data storage cell, it is communicated to connect with the analysis controlling unit to store the letter that the analysis controlling unit is got The result data of number and analyzing and processing.
2. a kind of device of cable local defect assessment based on impedance spectrum analysis according to claim 1, its feature It is:Described device further includes and communication unit of the data storage cell communication connection for sending and receiving data.
3. a kind of device of cable local defect assessment based on impedance spectrum analysis according to claim 2, its feature It is:Described device further includes to be distinguished with the analysis controlling unit, the data storage cell and the communication unit respectively The man-machine interaction unit of communication connection, the man-machine interaction unit has human-computer interaction interface and display interface, defeated for receiving The information that enters simultaneously shows information by the display interface.
4. a kind of device of cable local defect assessment based on impedance spectrum analysis according to claim 1, its feature It is:The incoming signal and the reference signal are the frequency-swept sine wave signal not higher than 100MHz, the signal acquisition list Member is two-channel digital oscillograph.
It is 5. a kind of using the method for carrying out cable local defect assessment such as Claims 1-4 any one of them device, its feature It is, includes the following steps:
(1) incoming signal and the reference signal are produced using the signal generating unit, the incoming signal is from described One end of tested cable is injected, and gathering the incoming signal using first acquisition channel of the signal gathering unit passes through Reflected signal after the tested cable, it is synchronous, institute is gathered using second acquisition channel of the signal gathering unit State reference signal;
(2) impedance of the tested cable in frequency sweep section is calculated according to the reflected signal and the reference signal;
(3) a new domain conversion is defined, the frequency spectrum function for the impedance that step (2) is calculated is transformed to along the tested electricity The power spectrum function of cable length direction;
(4) point of the power spectrum function described in step (3) more than 0dB is considered as along the tested cable length direction because existing Electric property is discontinuous and generates echo, and the discontinuous position of electric property is the local defect of the tested cable Position.
6. the method for cable local defect assessment according to claim 5, it is characterised in that:It is described in the step (2) The computational methods of tested cable resistance are as follows:
<mrow> <msub> <mi>Z</mi> <mrow> <mi>D</mi> <mi>U</mi> <mi>T</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mo>&amp;CenterDot;</mo> <mrow> <mo>(</mo> <mfrac> <msub> <mi>V</mi> <mn>0</mn> </msub> <msub> <mi>V</mi> <mn>1</mn> </msub> </mfrac> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>01</mn> <mo>)</mo> </mrow> </mrow>
Wherein, ZDUTIt is the impedance of the tested cable, Z1It is first acquisition channel for gathering the reflected signal Impedance, V1For the voltage vector value measured at first acquisition channel, V0For the voltage arrow measured at second acquisition channel Value.
7. the method for cable local defect assessment according to claim 6, it is characterised in that:In the step (3), it will count The method that obtained frequency spectrum function is transformed to power spectrum function is as follows:
f→t′ (1-02)
<mrow> <mfrac> <mrow> <mn>4</mn> <mi>&amp;pi;</mi> <mi>d</mi> </mrow> <mrow> <msub> <mi>v</mi> <mi>r</mi> </msub> <msub> <mi>v</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>&amp;RightArrow;</mo> <msup> <mi>&amp;omega;</mi> <mo>&amp;prime;</mo> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>03</mn> <mo>)</mo> </mrow> </mrow>
Wherein, νr=ν/ν0
F is the frequency of the incoming signal, and f is independent variable;
D is the length of tested cable;
ν is the phase velocity that the incoming signal is propagated in the tested cable;
νrIt is relative phase velocity of the incoming signal in the tested cable;
ν0It is the spread speed of light in a vacuum.
8. the method for cable local defect assessment according to claim 7, it is characterised in that:Defect in the step (4) The localization method of position is as follows:
The frequency f ' of the function in t ' domains is calculated,
<mrow> <msup> <mi>f</mi> <mo>&amp;prime;</mo> </msup> <mo>=</mo> <mfrac> <msup> <mi>&amp;omega;</mi> <mo>&amp;prime;</mo> </msup> <mrow> <mn>2</mn> <mi>&amp;pi;</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>d</mi> </mrow> <mrow> <msub> <mi>v</mi> <mi>r</mi> </msub> <msub> <mi>v</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>04</mn> <mo>)</mo> </mrow> </mrow>
F ' is the fundamental frequency of phase function in t ' domains, and the incidence point of the incoming signal from the tested cable propagates to The time of the incidence point is returned again to after the terminal of the tested cable;
, to produce echo there are during local defect, at this at x, make when apart from incidence point distance in the power spectrum of impedance phase A new frequency component is produced, this frequency is:
<mrow> <msup> <mi>f</mi> <mrow> <mo>&amp;prime;</mo> <mo>&amp;prime;</mo> </mrow> </msup> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>x</mi> </mrow> <mrow> <msub> <mi>v</mi> <mi>r</mi> </msub> <msub> <mi>v</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>05</mn> <mo>)</mo> </mrow> </mrow>
By identifying the f ' in the impedance phase power spectrum and f " in t ' domains, calculate since electric parameter is discontinuous and produce The position of echo:
<mrow> <mi>x</mi> <mo>=</mo> <mi>d</mi> <mo>&amp;CenterDot;</mo> <mfrac> <msup> <mi>f</mi> <mrow> <mo>&amp;prime;</mo> <mo>&amp;prime;</mo> </mrow> </msup> <msup> <mi>f</mi> <mo>&amp;prime;</mo> </msup> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>06</mn> <mo>)</mo> </mrow> </mrow>
The defects of above-mentioned x being calculated is the tested cable the distance between incidence point described in positional distance.
9. the method for cable local defect assessment according to claim 8, it is characterised in that:When the tested cable along its When length direction has multiple local defects, each defective locations have corresponded to a frequency component in power spectrum, pass through frequency Component fnCalculate the defects of corresponding position xn
<mrow> <msub> <mi>x</mi> <mi>n</mi> </msub> <mo>=</mo> <mi>d</mi> <mo>&amp;CenterDot;</mo> <mfrac> <msub> <mi>f</mi> <mi>n</mi> </msub> <msup> <mi>f</mi> <mo>&amp;prime;</mo> </msup> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mn>07</mn> <mo>)</mo> </mrow> </mrow>
The above-mentioned x being calculatednAs frequency component fnThe defects of corresponding and the distance of the incidence point.
10. the method for cable local defect assessment according to claim 5, it is characterised in that the appraisal procedure is also wrapped Include following steps:(5) rejected region in power spectrum chart is found out at the mirror image peak that the opposite side of the tested cable termination produces, its In, distance and the rejected region to the tested cable termination of position where the mirror image peak to the tested cable termination Apart from equal, the summit of rejected region and the mirror image peak summit straight line are connected as echo-signal along described tested The Trendline to decay on cable length direction, the Trendline are aided in the longitudinal direction using the tested cable termination position as abscissa There is an intersection point between line, locally lacked using the distance between the intersection point and the terminal peak-to-peak value for assessing the cable The sunken order of severity.
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