KR20100070813A - Degradation diagnosis system for cable and method thereof - Google Patents

Abstract

PURPOSE: A diagnosis system for a cable and method thereof is provided to secure reliability of power supply by diagnosing the deterioration of a device by using the frequency characteristic of the diagnostic signal. CONSTITUTION: A signal generator(150) creates a diagnostic signal which is inputted to one side of a target cable. A measuring unit(120) measures the diagnostic signal which is outputted to the second side of the measuring cable or the diagnostic signal which is reflected from the end of the target cable and is outputted to the first side. A diagnostic unit(130) diagnoses the deterioration of the target cable by using the diagnostic signal which is generated from the signal generator and the frequency characteristic of the diagnostic signal which measured by the measuring unit. A matching unit(140) matches the impedance of the measuring cable and the signal generator. The signal generator generates the pulse signal.

Description

Cable deterioration diagnostic system and its method {DEGRADATION DIAGNOSIS SYSTEM FOR CABLE AND METHOD THEREOF}

The present invention relates to a cable degradation diagnosis, and more particularly, a cable capable of reliably diagnosing an insulation degradation state of a cable by using a frequency characteristic of an output signal or a reflected signal that has passed through a measurement cable of a diagnostic signal, which is a pulse signal. A deterioration diagnostic system and method are provided.

Power Cable Insulation Diagnosis is intended to diagnose deterioration that may lead to an accident. The entire cable system including the main insulation layer is used as a diagnostic range to evaluate the deterioration status and location of the cable and ultimately evaluate the cable life. It is aimed at.

In addition, for the utility company and the user to achieve this objective economically, the main goal can be to reduce the cost of the line maintenance and to ensure the reliability of the power supply.

As climate change and the energy crisis have emerged as a global problem, the distribution of distributed power sources such as renewable energy has been expanding. The rapid increase in electric power demand resulting from economic development has led to the high pressure and high capacity in the global power industry. In addition, due to the rapid spread of sensitive loads such as information devices such as computers, the necessity of supplying uninterrupted and high-quality power gradually increases. Accordingly, the establishment of efficient measurement, transmission, and monitoring technologies for a large number of information in power systems worldwide At the same time, research on the development of intelligent automatic diagnosis systems to prevent accidents is increasing day by day.

Most cable failure accidents are due to electrical, mechanical, thermal and chemical degradation during manufacture, assembly or use, and the major causes of degradation are due to tree and manufacturing defects. Most of power cable live diagnosis devices that are currently commercialized or under development are based on partial discharge (PD) measurement method, and many devices are being developed and commercialized at home and abroad.

However, although the reliability of power cable degradation diagnosis by partial discharge measurement has been recognized in the case of a connecting material, especially an ultra high voltage junction box, the reliability of the cable main insulation layer has not been proved despite the difficulty of measurement and diagnosis. This is because the partial discharge (PD) discharge due to deterioration of the cable main insulation layer is so small that it is extremely difficult to distinguish it from noise, and the generation of the measurable partial discharge signal is likely to lead to an accident, and thus the meaning as a preventive diagnosis is faded. In particular, it is known that there is no at least measurable partial discharge in case of tree deterioration.

Therefore, there is a need for a power cable live diagnosis method based on a completely different principle rather than a partial discharge measurement method.

An object of the present invention, which was devised to solve the above problems, is to provide a cable degradation diagnosis system and method for improving the reliability of a diagnosis result in diagnosing a degradation state of a cable.

Another object of the present invention is to provide a cable degradation diagnosis system and method capable of reliably diagnosing an insulation state of a cable, thereby ensuring reliability of power supply and reducing maintenance costs of the cable. .

In order to achieve the above object, a cable degradation diagnostic system according to an aspect of the present invention includes a signal generator for generating a diagnostic signal input to the first side of the measurement cable; A measuring unit measuring the diagnostic signal output to the second side of the measuring cable or the diagnostic signal reflected from the end of the measuring cable and output to the first side; And a diagnosis unit for diagnosing a deterioration state of the measurement cable using frequency characteristics of the diagnostic signal generated by the signal generator and the diagnostic signal measured by the measurement unit.

In this case, the signal generator may generate a pulse signal, and the diagnostic unit is a reference based on the frequency characteristic change value of the diagnostic signal generated by the signal generator and the diagnostic signal measured by the measurement unit at a preset frequency If it is more than the change value it can be diagnosed that the measuring cable is degraded.

The diagnosis unit measures the measurement by using a frequency characteristic change of attenuation and dispersion of the diagnostic signal caused by an insulator equivalent conductance (G) per unit length and an insulator equivalent capacitance (C) per unit length among the distribution circuit parameters of the measurement cable. Diagnose cable degradation.

Cable degradation diagnostic method according to an aspect of the present invention comprises the steps of generating a diagnostic signal for diagnosing cable degradation and inputting it to the first side of the measurement cable; Measuring the diagnostic signal output to the second side of the measurement cable or the diagnostic signal reflected from the end of the measurement cable and output to the first side; And diagnosing a deterioration state of the measurement cable by using the generated diagnostic signal and the measured frequency characteristic of the diagnostic signal.

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, a cable degradation diagnosis system and a method thereof according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Figure 1 shows a cable degradation diagnostic system according to an embodiment of the present invention.

Referring to FIG. 1, the cable degradation diagnosis system includes a transmission measuring unit 120, a diagnosis unit 130, a matching unit 140, and a signal generation unit 150.

The transmission measuring unit 120 measures the diagnostic signal input to the first side of the measuring cable 110 in the live state or the diagonal state on the second side of the measuring cable 110.

That is, the transmission measuring unit 120 changes the distribution circuit variable according to the degradation state and the insulation state of the measurement cable 110 when the diagnostic signal inputted to the first side of the measurement cable 110, for example, per unit length of the cable. Measure the diagnostic signal according to the change of line resistance (R), line inductance (L) per unit length, insulator equivalent conductance (G) per unit length and insulator equivalent capacitance (C) per unit length.

In this case, the diagnostic signal may be a predetermined pulse, that is, a pulse signal, and thus the transmission measuring unit 120 measures the pulse signal output through the measurement cable 110. Here, the transmission measurement unit 120 may measure the frequency characteristic of the diagnostic signal output to the second side of the measurement cable 110 and provide it to the diagnosis unit 130.

Of course, the diagnostic signal may be input through any one of the inner conductor and the outer conductor when the inner and outer conductors of the measuring cable 110 are provided, and the place where the diagnostic signal is input may vary according to circumstances.

The signal generator 150 generates a diagnostic signal for diagnosing a deterioration state and an insulation state of the measurement cable 110, for example, a pulse signal, and inputs the pulse signal to the first side of the measurement cable 110.

In this case, the signal generator 150 may be a pulse generator for generating a pulse signal, and elements such as a width, a period, and an amplitude of the pulse signal may vary depending on a situation. The factors for can vary depending on various environments such as the type of diagnostic cable.

The matching unit 140 functions to match the impedance of the signal generator 150 and the measurement cable 110.

The diagnosis unit 130 diagnoses the deterioration state of the measurement cable 110 by using the frequency characteristic change of the diagnosis signal generated by the signal generator 150 and the diagnosis signal measured by the transmission measurement unit 120. .

That is, the diagnosis unit 130 changes the distribution circuit variable according to the deterioration state and the insulation state of the cable through the conceptual diagram and the equivalent circuit diagram of the coaxial transmission line illustrated in FIG. 2, that is, the line resistance per unit length (R), the unit. Changes in the frequency characteristics of the pulse signal due to variations in line inductance (L) per length, insulator equivalent conductance per unit length (G) and insulator equivalent capacitance per unit length (e.g., for attenuation and dispersion) By diagnosing the change, when the change value is equal to or greater than the preset reference conversion value, the measurement cable 110 may be diagnosed as deteriorated.

In this case, the diagnosis unit 130 may diagnose that the measurement cable 110 is deteriorated when the characteristic change value at the preset frequency is equal to or greater than the reference change value.

In the case of the power cable, as shown in FIG. 3, tree tree degradation is known as a major deterioration factor. When the insulator is polyethylene (PE), the conductivity (σ) and the dielectric constant (ε) in the tree region are sound. It is known to reach 10 to ¹⁰ times and 1 to 2 times the area (normal area), respectively.

That is, it can be seen that the increase in conductivity is very remarkable. In other words, the distribution circuit variable for the cable shown in FIG. 4, that is, the line resistance (R) per unit length, the line inductance (L) per unit length, the insulator equivalent conductance (G) per unit length, and the insulator equivalent capacitance (C) per unit length ) Can be expressed as in Equation 1.

Where ε and μ ₀ are the dielectric constant and permeability of the dielectric, a and b are the inner and outer conductor radius of the cable, σ is the conductivity of the dielectric, and σ _c and μ _c are the conductivity of the conductor And permeability, δ means skin depth.

As described above, the tree, which is the main deterioration factor of the cable, the projections and the electric tree, thereby causing a significant change in the conductivity and a predetermined change in the dielectric constant of the insulator, and the distribution circuit shown in Equation 1 As can be seen from the parametric equation, the conductivity and permittivity of the dielectric material changed by cable deterioration have a significant effect on the insulator equivalent conductance (G) per unit length among the distribution circuit variables, and somewhat influence the insulator equivalent capacitance (C) per unit length. You can see that.

On the other hand, it can be seen that the line resistance (R) per unit length and the line inductance (L) per unit length are not related to the deterioration of the insulator.

In other words, the change in the insulator properties due to the deterioration of the cable causes a change in the insulator equivalent conductance (G) per unit length and the insulator equivalent capacitance (C) per unit length among the distribution circuit variables, and among these, the insulator equivalent conductance per unit length ( The impact on changes in G) is absolute.

The diagnostic unit 130 calculates and calculates a frequency characteristic change value of an attenuation and dispersion of an input diagnostic signal, that is, a traveling wave with respect to an input pulse signal, due to a change in G and C caused by cable degradation. By comparing the changed value with the reference change value, the cable degradation can be diagnosed.

That is, the diagnosis unit 130 may cause a change in the G and C values in the corresponding portion due to deterioration occurring in a portion of the entire cable, and the specific frequency characteristic of the pulse signal may be changed due to the change in the generated G and C values. A change such as attenuation or dispersion occurs, and the change of the measured frequency at the specific frequency is used to diagnose whether the measurement cable 110 is deteriorated.

In this case, the diagnosis unit 130 may diagnose cable degradation using a plurality of reference change values. For example, the diagnosis unit 130 may use the first reference change value and the second reference change value (< When the first reference change value is set, if the calculated frequency-specific change value is equal to or greater than the first reference change value, the measurement cable is diagnosed to be deteriorated. If the change value is less than the second reference change value, it may be diagnosed that the measurement cable is in a normal state.

The diagnostic unit 130 is a communication interface unit (not shown) that receives the diagnostic signal measured by the transmission measuring unit 120, a database management unit (not shown) for managing the database of diagnostic data and determination results, accident history And a cable database unit (not shown) that integrates and manages cable management data such as a laying environment and a diagnosis result, and an analysis unit (not shown) that analyzes, determines, and processes the diagnosis result.

As described above, the cable degradation diagnosis system according to an exemplary embodiment of the present invention applies a pulse signal, which is a diagnostic signal, to a measurement cable to diagnose whether the degradation state is determined by using a frequency characteristic change of a pulse signal corresponding to the degradation state of the cable. It is easy to eliminate the noise effect, has high reproducibility of measurement, and can monitor the insulation status at all times, and it is possible to derive the optimal diagnostic parameter by detecting the decrease in insulation resistance of the cable which has a decisive effect on the life regardless of the degradation type. have.

Figure 5 shows a cable degradation diagnostic system according to another embodiment of the present invention.

Referring to FIG. 5, the cable degradation diagnosis system includes a reflection measuring unit 520, a diagnosis unit 540, a matching unit 530, and a signal generator 550.

The signal generator 550 performs the same function as the signal generator shown in FIG. 1. That is, the signal generator 550 generates a pulse signal, which is a diagnostic signal for diagnosing a deterioration state of the measurement cable 510, and inputs the pulse signal to the first side of the measurement cable 510 through the matching unit 530.

The matching unit 530 functions to match the impedance of the signal generator 550 and the measurement cable 510.

Furthermore, the matching unit 530 may perform a function of matching the impedance of the measurement cable 510 and the reflection measurement unit. The matching unit and the reflection measurement matching the impedance of the signal generator 550 and the measurement cable 510 may be performed. A matching part for matching the impedance of the part and the measurement cable may be provided separately.

The reflection measuring unit 520 measures a reflection signal with respect to a pulse signal which is a diagnostic signal input to the first side of the measurement cable 510.

That is, the reflection measuring unit 520 is a line resistance (R) per unit length, line inductance (L) per unit length of the cable that is a distribution circuit variable input to the first side of the measurement cable 510, reflected and output to the first side For measuring the pulse signal of the change of the insulation equivalent conductance (G) per unit length and the insulation equivalent capacitance (C) per unit length, the distribution circuit variable changes according to the degradation state and insulation state of the measuring cable. 520 measures a pulse signal including the changed distribution circuit variable.

The diagnosis unit 540 diagnoses the deterioration state of the measurement cable 510 by using the frequency characteristic change of the pulse signal generated by the signal generator 550 and the pulse signal measured by the reflection measuring unit 520. .

In this case, the diagnosis unit 540 deteriorates the measurement cable 510 when a change in frequency characteristic between the input pulse signal and the reflected pulse signal at a preset frequency is greater than or equal to a preset reference change value. Can be diagnosed.

Of course, the frequency for diagnosing the deterioration state and the reference change value for the frequency may vary depending on the ambient temperature and the cable temperature change in the live state, but this may be considered using a method of converting the relative change amount.

As described above, the cable degradation diagnosis system according to an exemplary embodiment of the present invention diagnoses the cable degradation by using a frequency characteristic change with an output signal or a reflected signal with respect to an input pulse signal using a pulse signal, and thereby, a pulse signal. Depending on the use, it is easy to eliminate the influence of external noise, which makes it possible to carry out reliable deterioration diagnosis, and to diagnose the deterioration state of live measuring cable to secure the reliability of power supply and increase the cost of line maintenance. Can be saved.

6 is a flowchart illustrating a cable degradation diagnostic method according to an embodiment of the present invention.

Referring to FIG. 6, the method for diagnosing cable degradation generates a pulse signal that is a diagnostic signal and inputs the generated pulse signal to a first side of a measurement cable to be measured (S610 and S620).

In this case, the generated pulse signal preferably has a pulse width, a period, and a magnitude which does not affect the power supplied to the measurement cable, and the measurement cable to be measured may be in a live state in which power is being supplied, and power is supplied. It may be in a diagonal state.

The pulse signal input to the first side of the measuring cable passes through the measuring cable and outputs the pulse signal output to the second side or propagates through the measuring cable and is then reflected at a specific position, for example at the end of the measuring cable and output to the first side. The pulse signal is measured (S630).

At this time, the pulse signal passing or reflected through the measuring cable is distributed circuit variable corresponding to the measuring cable, that is, the line resistance (R) per unit length, the line inductance (L) per unit length, and the unit according to the deterioration state and the insulation state of the cable. The insulator equivalent conductance (G) per length and insulator equivalent capacitance (C) per unit length are changed, and a passed pulse signal or a reflected pulse signal containing these changed parameters can be measured.

When the pulse signal passed or reflected through the measuring cable is measured, the pulse deterioration state can be diagnosed using the pulse signal inputted to the measuring cable and the measured pulse signal.

That is, the frequency characteristic change value of the pulse signal inputted to the measuring cable and the measured pulse signal is calculated, and the calculated frequency characteristic change value is compared with a preset reference change value (S640 and S650).

In this case, the change in the frequency characteristics of the attenuation, dispersion and reflection of the traveling wave, which is the change in the frequency characteristics of the input pulse signal due to the change of G and C caused by the cable deterioration, is calculated, and the calculated change value is compared with the reference change value. Can be.

As a result of the determination in step S650, it is diagnosed that the measurement cable is deteriorated when the frequency characteristic change value is more than the reference change value, and when the frequency characteristic change value is less than the reference change value, the measurement cable is diagnosed as normal (S660 and S670).

Of course, the compared frequency characteristic change value may mean a characteristic change value at at least one preset frequency.

In addition, the reference change value compared with the calculated frequency characteristic change value may be set in plural, which may vary depending on how many diagnosis results are set. For example, when there is one reference change value, the diagnosis result may be separated into normal and bad, but when the reference change value is two, the diagnosis result may be separated into normal, bad, and caution. If the reference change value is three or more, the diagnosis result set according to this may be different.

As described above, the cable degradation diagnosis method according to an embodiment of the present invention is easy to remove the influence on the external noise since the cable degradation is diagnosed using the frequency characteristic change of the pulse signal input to the measurement cable. Regardless of this, reliable deterioration diagnosis can be performed.

As described above, the cable degradation diagnosis system and method according to an embodiment of the present invention can increase the reliability of the bad line determination in selecting and managing a line with a high probability of an accident, and in the field during the insulation state evaluation work. In view of the workability and ease of analysis in Esau, testing and evaluation are possible without the need for technical skills and training.

In addition, it is possible to monitor the target line at all times in a live state, and in principle, it is possible to integrate and reduce weight, thereby providing excellent field applicability.

Therefore, in terms of economics such as test methods, devices, test procedures, and unit cost, the purpose of insulation status evaluation can be efficiently achieved, and deterioration status monitoring of all kinds of coaxial transmission lines such as low voltage signal line, distribution cable, and high voltage cable It may be applicable to diagnosis.

The cable degradation diagnostic system and method thereof according to the present invention can be modified and applied in various forms within the scope of the technical idea of the present invention and are not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the technical spirit of the present invention, it is not limited to the embodiments and the accompanying drawings. And should be judged to include equality.

Figure 1 shows a cable degradation diagnostic system according to an embodiment of the present invention.

2 shows a conceptual diagram and an equivalent circuit diagram of a coaxial transmission line.

3 shows a conceptual diagram for tree deterioration.

4 is an exemplary diagram for describing a distribution circuit variable for a coaxial transmission line.

Figure 5 shows a cable degradation diagnostic system according to another embodiment of the present invention.

6 is a flowchart illustrating a cable degradation diagnostic method according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

120: transmission measurement unit

130, 540: diagnostic unit

140, 530: matching part

150, 550: signal generator

520: reflection measuring unit

Claims (7)

A signal generator for generating a diagnostic signal input to the first side of the measurement cable; A measuring unit measuring the diagnostic signal output to the second side of the measuring cable or the diagnostic signal reflected from the end of the measuring cable and output to the first side; And A diagnosis unit for diagnosing a deterioration state of the measurement cable by using a frequency characteristic of the diagnostic signal generated by the signal generator and the measurement signal Cable degradation diagnostic system comprising a. The method of claim 1, The signal generator Cable degradation diagnostic system for generating pulse signals. The method according to any one of claims 1 and 2, Matching unit for matching the impedance of the signal generator and the measurement cable Cable degradation diagnostic system further comprising. The method according to any one of claims 1 and 2, The diagnostic unit Cable degradation diagnosis system for diagnosing that the measurement cable is degraded when the frequency characteristic change value of the diagnostic signal generated by the signal generator and the diagnostic signal measured by the measurement unit is equal to or greater than a predetermined reference change value at a preset frequency. . The method according to any one of claims 1 and 2, The diagnostic unit Cable degradation for diagnosing the deterioration state of the measurement cable by using the frequency characteristic of the attenuation and dispersion of the diagnostic signal caused by the insulator equivalent conductance per unit length and the insulator equivalent capacitance per unit length among the distribution circuit variables of the measurement cable Diagnostic system. Generating and inputting a diagnostic signal for diagnosing cable degradation to a first side of the measurement cable; Measuring the diagnostic signal output to the second side of the measurement cable or the diagnostic signal reflected from the end of the measurement cable and output to the first side; And Diagnosing a deterioration state of the measurement cable by using the generated diagnostic signal and the measured frequency characteristic of the diagnostic signal Cable degradation diagnostic method comprising a. The method of claim 6, The diagnostic signal is Pulse signal, The diagnosing step And diagnosing that the measurement cable is degraded when a frequency characteristic change value of the generated diagnostic signal and the measured diagnostic signal at a predetermined frequency is equal to or greater than a predetermined reference change value.

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