CN105137283A - Cable running state diagnosis system - Google Patents

Abstract

The invention discloses a cable running state diagnosis system, belonging to the electric system field. The prior art cannot simultaneously realize the evaluation of the cable operation state, cable local latency flaw positioning and fast positioning after the cable is permanently faulted. The cable running state diagnosis system comprises a cable initial characteristic parameter management module, a cable impedance spectrometry module, an impedance spectrum data analyzing-processing module, and a cable operation state diagnosis module. The cable running state diagnosis system realizes the said functions and provides a reliable diagnosis instrument.

Description

A kind of cable running status diagnostic system

Technical field

The invention belongs to electrical system field, more specifically, relate to a kind of cable running status diagnostic system.

Background technology

Cable plays an important role in the electric energy and communication signal transmission of modern large electric system.Easily there is permanent fault in operating cable, cable fault, once occur, will cause large electric system shutdown even out of control, and cause serious economic loss and social influence.

Power cable layer in power supply system is at cable duct or be directly embedded in underground, lays environment and using state can affect cable life greatly.Power cable runs for a long time under different soils, moisture, moisture, temperature environment, and insulation is vulnerable to corrosion penetration and the local ageing that occurs to insulate; Often can there is insulation breakdown because of mechanical external force in underground power cable, finally cause cable permanent fault.According to investigations, the insulation damages accident of high-voltage power insulation cable accounts for about 40% of high voltage electric equipment accident.

The safe operations of large electric traffic system to cable such as aircraft, track traffic, naval vessel propose more strict requirement, and in these electrical systems, the leading role of electric energy and control signal transmission served as by cable.In July, 1996, because the aging generation electric spark of Aircraft Cables local overheating causes fuel tank explosion, none survived for 230 passengers making on a frame Boeing-747 aircraft.

Shorter and the cable that electric pressure is higher of a large amount of length is there is in nuclear power station, the generation of Nuclear Power Accident often starts from the nuclear leakage of local, cable its organic polymer structure under high dose nuclear radiation will go to pot and quick aging will occur, to cable fault be caused and make with reactor out of hand, cause nuclear power station serious accident the most at last.

Visible, the diagnostic significance realizing cable running status is great, the diagnosis of cable running status comprises the quick position after the assessment of whole cable running status, cable local latency defect location and cable generation permanent fault, existing instrument still can not realize above-mentioned functions simultaneously, particularly for the location of cable latency defect, still lack very reliable diagnostic instrments.

Summary of the invention

For problems of the prior art, the application provides a kind of cable running status diagnostic system and diagnostic method thereof, wherein by studying the carrying out of its key component cable resistance spectrometry module, impedance spectrum Data Analysis Services module and relate to, provide a kind of diagnostic instrments reliably.

For achieving the above object, according to one aspect of the present invention, provide a kind of cable running status diagnostic system, it is characterized in that, this system comprises:

Cable initial characteristic parameter management module, realizes the management of all kinds of cable initial characteristic parameter database, and calculates cable initial characteristic parameter by the tested cable geometric parameter of input and insulating material dielectric function;

Cable resistance spectrometry module, automatically survey frequency scope is selected according to tested cable length, by inputting low-voltage variable frequency sine signal source between tested cable core and ground wire, measuring by the curve of test agent input impedance with frequency change, obtaining cable resistance spectrum;

Impedance spectrum Data Analysis Services module, carries out data analysis to surveyed cable resistance modal data, to extract cable electrical parameter relevant information;

Cable running status diagnostic module, utilize the result of impedance spectrum Data Analysis Services module, realize the function that the assessment of whole cable running status, cable local defect location and cable permanent fault are located, provide cable running status comments and cable maintenance suggestion.

Preferably, described parameter comprises characteristic impedance, propagation coefficient, cable wideband impedance spectrum.

Preferably, described impedance spectrum data analysis adopts intelligent optimization searching algorithm and generalized orthogonal integral transformation algorithm.

In general, according to above-mentioned technical conceive of the present invention compared with prior art, following technological merit is mainly possessed:

1, provide a kind of diagnostic instrments reliably, achieve the quick position after the assessment of whole cable running status, cable local latency defect location and cable generation permanent fault simultaneously;

2, the curve (i.e. wideband impedance spectrum) of the input impedance of cable head within the scope of certain frequency with frequency change is measured, analyze institute by intelligent analysis process and surveys impedance spectrum, realize that whole cable ageing state is assessed, cable locally latency defect diagonsis and cable permanent fault fast positioning function.

Accompanying drawing explanation

Fig. 1 is chief component of the present invention;

Fig. 2 is each functions of modules block diagram of the present invention;

Fig. 3 is whole cable ageing state assessment curve in the embodiment of the present invention;

Fig. 4 is local defect diagnosis curve in the embodiment of the present invention;

Fig. 5 is cable fault auditory localization cues in the embodiment of the present invention.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.In addition, if below in described each embodiment of the present invention involved technical characteristic do not form conflict each other and just can mutually combine.

Fig. 2 is each functions of modules block diagram of the present invention;

(1) cable initial characteristic parameter management module

Cable initial characteristic parameter is the key parameter in the diagnosis of cable running status, need to obtain in advance, this module calculates cable initial characteristic parameter (characteristic impedance, propagation coefficient) by the tested cable geometric parameter of input and insulating material dielectric function, cable geometric parameter obtains by measuring, cable insulation material dielectric function then utilizes network analyzer to measure acquisition in advance and input database by intercepting SI semi-insulation sample, and this module database realizes the management of all kinds of cable insulation material dielectric parameter and the management of all kinds of cable initial characteristic parameter.

(2) cable resistance spectrometry module

This module selects survey frequency scope automatically according to tested cable length, by inputting low-voltage variable frequency sine voltage signal source between tested cable core and ground wire, measure current signal, calculate the curve of cable input impedance with frequency change, obtain cable resistance spectrum.This module survey frequency range lower limit f _lowand upper frequency limit f _updetermined by following formula:

(1)

Wherein r=e ^{-2 α l}, α is cable attenuation coefficient, is the real part of propagation coefficient, and propagation coefficient is then obtained by cable initial characteristic parameter management module, and l is cable length, and by cable operation management, department obtains.

(3) impedance spectrum Data Analysis Services module

This module carries out data analysis to surveyed cable resistance modal data, and extract cable electrical parameter relevant information, algorithm mainly comprises intelligent optimization searching algorithm and generalized orthogonal integral transformation algorithm.

The ultimate principle of intelligent optimization searching algorithm is: within the scope of certain frequency, and impedance spectrum is cable properties parameter (characteristic impedance Z ₀, propagation coefficient γ) function, when cable running status changes, cause characterisitic parameter to change, thus impedance spectrum changed.Intelligent optimization searching algorithm solves cable properties parameter by counter from surveyed impedance spectrum, and further utilization level parameter can the dielectric loss tan δ of computational representation cable insulation state, thus assesses whole cable running status.The relational expression of cable dielectric loss and characterisitic parameter is:

$tan\mathrm{\δ}=\left|\frac{\mathrm{Re}\[\frac{\mathrm{\γ}}{Z_0}\]}{\mathrm{Im}\[\frac{\mathrm{\γ}}{Z_0}\]}\right|---\left(2\right)$

The ultimate principle of generalized orthogonal integral transformation algorithm by: being carried out generalized orthogonal integral transformation to surveying impedance spectrum, making integral transformation value be in intact place in local defect or fault and occurring significant difference, realize the location of cable local latency defect or fault.In the present invention, generalized orthogonal integral transformation algorithm following formula describes:

$F\left(x\right)={\∫}_{f_{low}}^{f_{up}}Z\left(f\right)\·e^{-2\mathrm{\γ}x}df=\left\{\begin{array}{cc}a& \left(x\≠l_d\right)\\ b& \left(x=l_d\right)\end{array}\right.,(0\≤x\≤l)---\left(3\right)$

Wherein, F (x) is integral transformation function, and Z (f) is surveyed impedance spectrum by cable resistance spectrometry module, and γ is the cable distribution coefficient that cable initial characteristic parameter management module obtains, l _dfor cable local defect or abort situation.Work as x=l _dtime, with x ≠ l _da and b is widely different for Shi Shangshu product integral value.Impedance spectrum integral transformation function after cable generation local defect and the integral transformation function under serviceable condition are carried out contrasting the difference that can highlight defective section and intact part further, defined function VA (x) is:

$VA\left(x\right)=\left|\frac{F_h\left(x\right)}{F_d\left(x\right)}\right|---\left(4\right)$

Wherein, F _dfor there is the cable resistance spectral integral transforming function transformation function after local defect, F in (x) _hx () is the impedance spectrum integral transformation function of intact cable under same load, claim VA (x) to be integral transformation diagnosis function, and it characterizes the situation of cable distribution coefficient with change in location.Under normal circumstances cable everywhere propagation coefficient be equal, do not change with position, therefore, if show when VA (x) is constantly equal to 1.0, the propagation coefficient at cable diverse location place is identical, namely cable is in serviceable condition, does not occur local defect or fault in cable.

(4) cable running status diagnostic module

This module utilizes impedance spectrum Data Analysis Services resume module result, draws whole cable dielectric loss curve, assessment whole cable ageing state.Draw diagnosis function VA (x) image, realize cable local defect location or cable permanent fault location, provide cable running status comments and cable maintenance suggestion.

Embodiment

For making content of the present invention more clear and intuitive, respectively the assessment of overall ageing state, local defect location and permanent fault location test are implemented respectively to three twisted polyethylene cables (being numbered A, B, C respectively).Test specimen is typical coaxial structure, its heart yearn radius r _cfor 6.3mm, insulation thickness a is 9.6mm, outer conductor radius r _sfor 15.8mm.

Cable A length is 20m, overall by thermal-electrical aging case aging 240h at 135 DEG C.Cable B length is 50m, heats 240 hours respectively, the long local ageing section of each formation 1cm in local, 20m and 35m place at 135 DEG C.Cable C length is 60m, arranges short trouble at 30m place.

Figure 3 shows that the cable A overall dielectric loss frequency spectrum obtained in the embodiment of the present invention, normal crosslinking polyethylene-insulated cable insulation dielectric loss is 10 ^-3the order of magnitude, becomes 10 by dielectric loss after heating accelerated deterioration in 240 hours at 135 DEG C ^-2the order of magnitude, belongs to slight ageing state.

Fig. 4 is the cable B local defect auditory localization cues obtained in the embodiment of the present invention, and curve occurs two oscillation peak at 20m and 35 places, shows that this place's electric parameter changes.Therefore, two place's local defects of the reliable positioning cable B of curve energy are diagnosed.

Fig. 5 is the cable C localization of fault curve obtained in the embodiment of the present invention, and curve occurs remarkable peak value at 30m place, located the trouble spot at this place.

Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (3)

1. a cable running status diagnostic system, is characterized in that, this system comprises:

Cable initial characteristic parameter management module, realizes the management of all kinds of cable initial characteristic parameter database, and calculates cable initial characteristic parameter by the tested cable geometric parameter of input and insulating material dielectric function;

Cable resistance spectrometry module, automatically survey frequency scope is selected according to tested cable length, by inputting low-voltage variable frequency sine signal source between tested cable core and ground wire, measuring by the curve of test agent input impedance with frequency change, obtaining cable resistance spectrum;

Impedance spectrum Data Analysis Services module, carries out data analysis to surveyed cable resistance modal data, to extract cable electrical parameter relevant information;

Cable running status diagnostic module, utilize the result of impedance spectrum Data Analysis Services module, realize the function that the assessment of whole cable running status, cable local defect location and cable permanent fault are located, provide cable running status comments and cable maintenance suggestion.

2. the system as claimed in claim 1, is characterized in that, described parameter comprises characteristic impedance, propagation coefficient, cable wideband impedance spectrum.

3. the system as claimed in claim 1, is characterized in that, described impedance spectrum data analysing method adopts intelligent optimization searching algorithm and generalized orthogonal integral transformation algorithm.