CN105137283B - A kind of cable operating status diagnostic system - Google Patents

Abstract

The invention discloses a kind of cable operating status diagnostic systems, belong to electrical system technical field, existing diagnostic instrments cannot realize that the quick positioning after permanent fault occurs for cable overall operation status assessment, cable part latency defect location and cable simultaneously, the diagnostic system of offer provided by the invention, it include: cable initial characteristic parameter management module, cable resistance spectrometry module, impedance spectrum Data Analysis Services module, cable operating status diagnostic module, above-mentioned function is realized simultaneously, provides a kind of reliable diagnostic instrments.

Description

A cable running state diagnosis system

technical field

The invention belongs to the field of electrical systems, and more specifically relates to a cable running state diagnosis system.

Background technique

Cables play an extremely important role in the transmission of electric energy and communication signals in modern large-scale electrical systems. Cables in operation are prone to permanent faults. Once a cable fault occurs, it will cause a large electrical system to shut down or even go out of control, causing serious economic losses and social impact.

The power cables in the urban power supply system are laid in cable trenches or directly buried underground. The laying environment and usage status will greatly affect the life of the cables. Power cables operate under different soil, moisture, moisture, and temperature environments for a long time, and the insulation is susceptible to corrosion and penetration, resulting in partial insulation aging; underground power cables often suffer from insulation damage due to external mechanical forces, and eventually lead to permanent failure of the cable. According to the survey, the insulation damage accidents of high-voltage power insulated cables account for about 40% of the accidents of high-voltage electrical equipment.

Large-scale electrical transportation systems such as aircraft, rail transit, and ships put forward stricter requirements for the safe operation of cables. In these electrical systems, cables play a leading role in the transmission of electrical energy and control signals. In July 1996, the fuel tank exploded due to electric sparks generated by local overheating and aging of the aircraft cables, killing all 230 passengers on board a Boeing 747.

There are a large number of cables with short length and high voltage level in nuclear power plants. The occurrence of nuclear power accidents often begins with local nuclear leakage. Under high-dose nuclear radiation, the organic polymer structure of cables will be destroyed and rapid aging will occur, which will lead to cable Failure and the loss of control of the reactor will eventually lead to a major safety accident in the nuclear power plant.

It can be seen that it is of great significance to realize the diagnosis of cable operation status. The diagnosis of cable operation status includes the evaluation of the overall operation status of the cable, the location of local latent defects of the cable, and the rapid location of the cable after a permanent fault. The existing instruments cannot realize the above functions at the same time. , especially for the positioning of latent defects in cables, there is still a lack of very reliable diagnostic instruments.

Contents of the invention

Aiming at the problems existing in the prior art, what this application provides is a cable running state diagnosis system and its diagnosis method, in which through the research and involvement of its key components, the cable impedance spectrum measurement module and the impedance spectrum data analysis and processing module, A reliable diagnostic instrument is provided.

In order to achieve the above object, according to one aspect of the present invention, a cable running state diagnosis system is provided, characterized in that the system includes:

The cable initial characteristic parameter management module realizes the management of various types of cable initial characteristic parameter databases, and calculates the initial cable characteristic parameters by inputting the measured cable geometric parameters and the dielectric function of the insulating material;

The cable impedance spectrum measurement module automatically selects the measurement frequency range according to the length of the cable under test. By inputting a low-voltage variable-frequency sinusoidal signal source between the core wire of the cable under test and the ground wire, it measures the curve of the input impedance of the sample under test as a function of frequency, and obtains Cable impedance spectroscopy;

The impedance spectrum data analysis and processing module performs data analysis on the measured cable impedance spectrum data to extract relevant information about cable electrical parameters;

The cable operation state diagnosis module uses the processing results of the impedance spectrum data analysis and processing module to realize the functions of overall cable operation state evaluation, cable local defect location and cable permanent fault location, and gives cable operation state evaluation opinions and cable maintenance suggestions.

Preferably, the parameters include characteristic impedance, propagation coefficient, and cable broadband impedance spectrum.

Preferably, the analysis of the impedance spectrum data adopts an intelligent optimization search algorithm and a generalized orthogonal integral transformation algorithm.

Generally speaking, compared with the prior art, according to the above-mentioned technical concept of the present invention, it mainly possesses the following technical advantages:

1. Provide a reliable diagnostic instrument, and at the same time realize the evaluation of the overall operation status of the cable, the location of local latent defects of the cable, and the rapid location of the cable after a permanent fault occurs;

2. Measure the curve of the input impedance of the cable head end changing with frequency within a certain frequency range (ie broadband impedance spectrum), analyze the measured impedance spectrum through intelligent analysis algorithms, and realize the evaluation of the overall aging state of the cable, the diagnosis of local latent defects of the cable and Cable permanent fault quick location function.

Description of drawings

Fig. 1 is main component of the present invention;

Fig. 2 is each module functional block diagram of the present invention;

Fig. 3 is the evaluation curve of the cable overall aging state in the embodiment of the present invention;

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

Fig. 5 is a cable fault location curve in the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Fig. 2 is each module functional block diagram of the present invention;

(1) Cable initial characteristic parameter management module

The initial characteristic parameters of the cable are the key parameters in the diagnosis of the cable operation status, which need to be obtained in advance. This module calculates the initial characteristic parameters (characteristic impedance, propagation coefficient) of the cable by inputting the geometric parameters of the measured cable and the dielectric function of the insulating material. The geometric parameters of the cable are passed The dielectric function of the cable insulation material is obtained by measurement, and the dielectric function of the cable insulation material is obtained by taking part of the insulation sample and measured in advance with a network analyzer and entered into the database. The module database realizes the management of the dielectric parameters of various cable insulation materials and the management of various initial characteristic parameters of cables.

(2) Cable Impedance Spectrum Measurement Module

The module automatically selects the measurement frequency range according to the length of the cable under test. By inputting a low-voltage variable-frequency sinusoidal voltage signal source between the core wire of the cable under test and the ground wire, the current signal is measured, and the curve of the cable input impedance changing with frequency is calculated to obtain the cable impedance. Spectrum. The module measures the lower limit of the frequency range f _low and the upper limit of the frequency f _up by the following formula:

(1)

Where r=e ^-2αl , α is the cable attenuation coefficient, which is the real part of the propagation coefficient, and the propagation coefficient is obtained through the cable initial characteristic parameter management module, and l is the cable length, which is obtained through the cable operation management department.

(3) Impedance spectrum data analysis and processing module

This module analyzes the measured cable impedance spectrum data and extracts the relevant information of cable electrical parameters. The algorithm mainly includes intelligent optimization search algorithm and generalized orthogonal integral transformation algorithm.

The basic principle of the intelligent optimization search algorithm is: within a certain frequency range, the impedance spectrum is a function of the cable characteristic parameters (characteristic impedance Z ₀ , propagation coefficient γ). When the cable operating state changes, the characteristic parameters change, so that the impedance The spectrum changes. The intelligent optimization search algorithm deciphers the cable characteristic parameters from the measured impedance spectrum, and further uses the characteristic parameters to calculate the dielectric loss tanδ that characterizes the cable insulation state, so as to evaluate the overall operation status of the cable. The relationship between cable dielectric loss and characteristic parameters is:

The basic principle of the generalized orthogonal integral transformation algorithm is: carry out generalized orthogonal integral transformation on the measured impedance spectrum, so that the integral transformation value has a significant difference when the local defect or fault is in good condition, and realizes the location of the local latent defect or fault of the cable. Generalized orthogonal integral transformation algorithm is described with following formula among the present invention:

Among them, F(x) is the integral transformation function, Z(f) is the impedance spectrum measured by the cable impedance spectrum measurement module, γ is the cable propagation coefficient obtained by the cable initial characteristic parameter management module, l _d is the cable local defect or fault location. When x=l _d , the above-mentioned product integral values a and b are very different from x≠l _d . Comparing the integral transformation function of the impedance spectrum after a local defect occurs in the cable with the integral transformation function in the intact state can further highlight the difference between the defective section and the intact section, and the function VA(x) is defined as:

Among them, F _d (x) is the integral transformation function of the cable impedance spectrum after local defects occur, F _h (x) is the integral transformation function of the impedance spectrum of the intact cable under the same load, and VA (x) is called the integral transformation diagnostic function, It characterizes how the cable propagation coefficient varies with position. Under normal circumstances, the propagation coefficient of the cable is equal everywhere, and does not change with the position. Therefore, if VA(x) is equal to 1.0, it indicates that the propagation coefficient at different positions of the cable is the same, that is, the cable is in good condition, and no local defects appear in the cable. or malfunction.

(4) Cable running status diagnostic module

This module uses the impedance spectrum data to analyze the processing results of the processing module, draw the overall dielectric loss curve of the cable, and evaluate the overall aging state of the cable. Draw the diagnostic function VA(x) image to realize the location of local cable defects or permanent cable faults, and give evaluation opinions on cable operation status and suggestions on cable maintenance.

Example

In order to make the content of the present invention clearer and more intuitive, three cross-linked polyethylene cables (respectively numbered as A, B, and C) were subjected to overall aging state evaluation, local defect location and permanent fault location tests. The test sample is a typical coaxial structure, the core wire radius r _c is 6.3mm, the insulation thickness a is 9.6mm, and the outer conductor radius r _s is 15.8mm.

The length of cable A is 20m, and the whole is aged at 135°C for 240h through an electric aging box. Cable B is 50m in length, and is heated locally at 135°C for 240 hours at 20m and 35m respectively to form a 1cm-long local aging section. The length of cable C is 60m, and a short-circuit fault is set at 30m.

Figure 3 shows the overall dielectric loss spectrum of cable A obtained in the embodiment of the present invention. The dielectric loss of normal XLPE cable insulation is on the order of 10 ^-3 , and the dielectric loss becomes It is on the order of 10 ^-2 and belongs to the mild aging state.

Fig. 4 is the local defect location curve of cable B obtained in the embodiment of the present invention. Two oscillation peaks appear in the curve at 20m and 35m, indicating that the electrical parameters change there. Therefore, the diagnostic curve can reliably locate the two local defects of cable B.

Fig. 5 is the fault location curve of cable C obtained in the embodiment of the present invention, the curve has a significant peak at 30 m, and the fault point there is located.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (2)

1. a kind of cable operating status diagnostic system, which is characterized in that the system includes:

Cable initial characteristic parameter management module, realizes the management of all kinds of cable initial characteristic parameter databases, and passes through input Tested cable geometric parameter and insulating materials dielectric function calculate cable initial characteristic parameter；

Cable resistance spectrometry module automatically selects measurement frequency range according to subject cable length, by subject cable core Low-voltage variable frequency sine signal source is inputted between line and ground wire, measurement subject sample input impedance curve varying with frequency obtains Cable resistance spectrum；

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

Cable operating status diagnostic module realizes that cable is integrally transported using the processing result of impedance spectrum Data Analysis Services module The function that row status assessment, the positioning of cable local defect and cable permanent fault position, provides the assessment of cable operating status Opinion and cable maintenance are suggested；

Wherein, the impedance spectrum data analysing method uses intelligent optimization searching algorithm and generalized orthogonal integral transformation algorithm, Specific processing step is as follows:

It is counter from surveyed impedance spectrum to solve cable properties parameter, utilization level parameter can computational representation cable insulation status dielectric Tan δ, the relational expression of cable dielectric loss and characterisitic parameter is lost are as follows:

In formula, Z0 is characterized impedance, γ is propagation coefficient；

Generalized orthogonal integral transformation is carried out to surveyed impedance spectrum, generalized orthogonal integral transformation algorithm is expressed as follows:

Wherein, F (x) is integral transformation function, and Z (f) surveys impedance spectrum by cable resistance spectrometry module, and γ is that cable is initially special Property parameter management module obtain cable distribution coefficient, l_dFor cable local defect or abort situation, l is cable length；

Impedance spectrum integral transformation function after cable to that local defect occur and the integral transformation function under serviceable condition carry out pair Than for highlighting the difference of defective section Yu intact part, defining integration transforming function transformation function VA (x) are as follows:

Wherein, F_dIt (x) is the cable resistance spectral integral transforming function transformation function after generation local defect, F_hIt (x) is intact cable same negative Impedance spectrum integral transformation function under carrying characterizes the case where cable distribution coefficient is with change in location；

If VA (x) shows that the propagation coefficient at cable different location is identical when being constantly equal to 1.0, i.e., cable is in serviceable condition.

2. the system as claimed in claim 1, which is characterized in that the cable initial characteristic parameter includes characteristic impedance, propagates Coefficient and cable wideband impedance spectrum.