KR101220460B1 - Method and system for aged deterioration of cable using variation ratio of propagation coefficient - Google Patents

Abstract

PURPOSE: A cable aged deterioration measuring system and a method thereof are provided to measure aged deterioration of a cable by a relatively simple method of using the variation ratio of a propagation coefficient. CONSTITUTION: A cable aged deterioration measuring system(1000) comprises a cable(100), a load(200), a first device(300), and a second device(400). One end of the cable is connected to the load. The first device, by applying DC voltage and AC voltage to the load, determines the kinds, values, and serial/parallel connection relations of elements included in the load, and calculates a time constant generated by the elements. As impulse voltage is applied to the load through the other end of the cable, the second device checks reflective voltage of the load and comes up with the variation ratio of a propagation coefficient.

Description

Measurement system and method of cable aging using propagation coefficient variation ratio {Method and system for aged deterioration of cable using variation ratio of propagation coefficient}

The present invention relates to a cable aging change measurement system and a method thereof, and more particularly, to a system and a method for measuring the cable aging change using a propagation coefficient change ratio with a load connected to the cable.

Aged Deterioration of a cable refers to degradation of cable performance or function due to corrosion, abrasion, changes in physical properties, including natural deterioration, over a long period of time.

As the cable ages, the cable may fail, and the propagation speed of the cable may also change as compared with cable manufacturing.

Background Art Conventionally, in underground cables for ultra-high voltage transmission, cables used in nuclear power plants, submarine cables, etc., it is not possible to grasp secular changes of cables, or it is somewhat difficult to grasp secular changes of cables.

Specifically, in the related art, the degree of secular variation of a cable can be grasped based on the value provided when the cable is manufactured, or the degree of secular variation of a cable can be grasped only for a cable whose length is known.

Therefore, conventionally, there was a limit in grasping the degree of secular variation of a cable, and there was also inconvenience.

The present invention has been made to solve the above-mentioned inconvenience, and an object of the present invention is to provide a cable aging change measurement system and method that can grasp the degree of aging change of the cable while the cable is connected to the load.

In the cable aging measurement system according to an embodiment of the present invention, a load, a cable connected to one end of the load, by applying a DC voltage and an AC voltage to the load, the type of elements included in the load, the value of the elements And a first device for determining a connection relationship of the elements and for calculating a time constant by the elements, and when an impulse voltage is applied to the load through the other end of the cable, reflection from the load And a second device for checking the voltage to calculate the propagation coefficient change ratio.

The first device and the second device may calculate the time constant and the propagation coefficient change ratio, respectively, with the load connected to the cable.

The propagation coefficient change ratio may be a propagation coefficient confirmed through the reflection voltage with respect to an arbitrarily set propagation coefficient.

The second apparatus may improve the accuracy of calculating the propagation coefficient change ratio by repeatedly performing the reflection voltage check according to the application of the impulse voltage more than a predetermined number of times.

The apparatus may further include a user input unit configured to receive the randomly set propagation factor.

The display apparatus may further include a display configured to display the identified reflected voltage.

The load may be any one of an RL load including a resistor and an inductor and an RC load including a resistor and a capacitor.

The connection relationship between the elements is a difference between a first resistance value determined when the load is determined as an RL load and applied when a DC voltage is applied to the first device, and a second resistance value measured when an AC voltage is applied to the first device. If is greater than or equal to a predetermined value, it may be a parallel connection of a resistor and an inductor.

The connection relationship between the devices may be a parallel connection of a resistor and an inductor when the load is determined as an RL load and the first resistance value is substantially zero.

The connection relationship between the elements may include a difference between a first resistance value measured when the load is determined as an RC load and a second resistance value measured when an AC voltage is applied to the first device and a second resistance value measured when an AC voltage is applied to the first device. If is greater than or equal to a predetermined value, it may be a series connection of a resistor and a capacitor.

The connection relationship between the elements may be a series connection of a resistor and a capacitor when the load is determined as an RC load and the first resistance value is infinite.

The second device may analyze the noise component of the reflected voltage and apply the analyzed noise component to the propagation coefficient change ratio calculation.

The cable age change measurement system may perform fault point diagnosis using the calculated propagation coefficient change ratio.

On the other hand, the cable age change measurement method according to an embodiment of the present invention, when the DC voltage is applied to the load of the cable is connected, detecting the first load voltage and the first load current according to the DC voltage applied, When an AC voltage is applied to the load while the cable is connected, determining whether the reactance X of the load R is 1, and the reactance X of the load R is 1. In this case, detecting a second load voltage and a second load current, and confirming the size and type of the load based on the first load voltage, the first load current, the second load voltage, and the second load current. Calculating a time constant of the load according to the confirmation; storing and inputting an arbitrary propagation coefficient; checking an reflected voltage reflected from the load after applying an impulse voltage to the load through the cable; And calculating a propagation coefficient change ratio using the arbitrary propagation coefficient and the identified reflection voltage, wherein the propagation coefficient change ratio is a propagation identified through the reflection voltage with respect to an arbitrarily set propagation coefficient. May be a coefficient.

The method may further include repeating the reflected voltage check according to the application of the impulse voltage more than a predetermined number of times.

The method may further include analyzing a noise component of the reflected voltage, and analyzing the noise component may apply the analyzed noise component to the propagation coefficient change ratio.

According to the present invention, since the cable age change can be measured using the propagation coefficient change ratio with the load connected to the cable, the cable age change can be measured by a relatively simple method.

1 is a view showing a aging change measurement system of a cable according to an embodiment of the present invention.
2 to 4b are diagrams for explaining the size, type, and time constant calculation method of the load.
5 is a graph showing a load curve of a circuit in which a resistor and an inductor are connected.
6 is a graph illustrating a load curve of a circuit in which resistance and capacitance are connected.
7 is a flowchart for explaining a method for measuring aging change of a cable.
8 is a flowchart illustrating a method for measuring the secular change of a cable by reflecting the noise actually occurring.
9 is a flowchart for explaining a method for diagnosing a failure point using a propagation coefficient change ratio.
10A is a diagram showing propagation coefficients actually calculated in a second device.
FIG. 10B is an enlarged view of region B of FIG. 10A;

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a view showing a aging change measurement system of a cable according to an embodiment of the present invention.

Referring to FIG. 1, the secular variation measuring system 1000 of a cable includes a cable 100, a load 200, a first device 300, a second device 400, a display unit 500, and a controller 600. ).

The cable 100 includes various types of cables, such as coaxial cables.

One end of the cable 100 is connected to the load 200. With one end of the cable 100 connected to the load 200, various characteristic values to be described below may be measured, such as load voltage, load current, and reflected voltage.

The load 200 may be various elements that can be connected to the cable 100, but preferably, an RL series load in which a resistor and an inductor are connected in series, an RL parallel load in which a resistor and an inductor are connected in parallel, and a resistor and a capacitor are in series. It may be any one of the RC series load connected to, and the RC parallel load connected in parallel with a resistor and a capacitor. In order to emphasize that the cable is connected to the load, the load and the cable are shown in a single box as shown in FIG.

The first device 300 is connected to at least one of the cable 100 and the load 100, and determines the type of the plurality of elements included in the load 200, the value of the elements, and the connection relationship between the elements, Calculate the time constant by

The first device 300 includes a DC / AC generator 330, a voltage / current detector 350, and an analyzer 370.

The DC / AC generator 330 generates DC or AC and applies the generated DC or AC to the load 200.

When a direct current or alternating current is applied to the load 300, the voltage / current detector 350 detects a current flowing through each element included in the load (eg, a resistor, an inductor, and a capacitor) and a voltage across each element. do.

The analyzing unit 370 is based on the results of the DC / AC generating unit 330 and the voltage / current detecting unit 350, and the types of the plurality of elements included in the load 200, the values of the elements, and the connection relationship between the elements. (Serial / Parallel) is determined to calculate the time constant generated by the elements.

The analyzer 370 is determined to be the RL load of the resistor and the inductor, and the first resistance value measured when the direct current voltage is applied to the first device 300 and the second measured value when the AC voltage is applied to the first device 300. If the difference from the resistance is greater than or equal to a predetermined value or the first resistance is substantially zero, it is determined that the resistor and the inductor are RL loads connected in parallel.

Alternatively, the analysis unit 370 is determined to be the RC load of the resistor and the capacitor, and is measured when the first resistance value measured when the DC voltage is applied to the first device 300 and the AC voltage is applied to the first device 300. If the difference from the second resistance value is greater than or equal to a predetermined value or the first resistance value is infinity, it is determined that the resistor and the capacitor are RC loads connected in series.

Here, the predetermined value is a value that is quite large, and is a value that the person skilled in the art can recognize that the difference between each resistance value is quite large.

As an example, the first device 300 may be an LCR meter. The first device 300 is a device for observing the electrical characteristics of the electronic component and the sample is an equipment for automatically measuring and analyzing the electrical characteristics according to the frequency.

Using the first device 300, the inductance (L), which is the amount representing the counter electromotive force generated by the electromagnetic induction by the change of the current flowing through the circuit, the amount of charge stored (or separated) at a constant voltage Capacitance (C: Capacitance), the resistance of a conductor to pass current, resistance (R: Resistance), which is the value obtained by dividing voltage by current, and impedance (Z: Impedance), which is the ratio of the AC voltage applied to an AC circuit with the AC current flowing through the circuit. At least one of) can be calculated.

In addition, the first device 300 includes Q: quality factor (quality of circuit), D: dissipation factor, G: parallel conductance, X: series reactance, and impedance phase angle. angle of impedance) and the like can be calculated.

As a connection method between the first device 300 and the load to be calculated, there are a two terminal method, a three terminal method, a four terminal method, a five terminal method, a four terminal method. In the two-terminal method, the connection is simple, but the error is large due to the contact resistance, the series impedance (r) of the cable, and the stray capacitance (Cs) between the cable and the terminal. The three-terminal method reduces the measurement error of high impedance by suppressing stray capacitance by electrostatic shielding on cables or samples, and is mainly used when measuring small capacitance. The four-terminal method eliminates the influence of voltage drop and connection resistance due to the series impedance of the cable by installing the voltage detecting cable independently, and reduces the measurement error of low impedance, and considers the effect of mutual inductance (M) between cables. There is a need. In the four-terminal method, Kelvin clips having two electrodes insulated on one clip allow easy four-terminal connection with two clips. The five-terminal method reduces the measurement error in impedance. In the four-terminal method, AC impedance measurement is not affected by thermal power unlike DC, but the low impedance measurement becomes more difficult as the frequency increases due to electromagnetic induction between the current cable and the voltage cable. Therefore, the four-terminal alternative method uses a shield of the cable to superimpose the current path and the return path, thereby suppressing magnetic flux generation and reducing residual impedance due to electromagnetic induction.

Meanwhile, the first device 300 automatically calculates the type and value of elements included in the load 200 by pressing a button provided in the aging change measuring system 1000 or the first device 300, and further, The time constant of the load 200 may also be preprogrammed to automatically calculate it. The first device 300 may be programmed in advance to display the calculated value and the time constant of the load 200 on the display unit 500 to be described later.

When the impulse voltage is applied to the load 200 through the other end of the cable 100, the second device 400 checks the reflected voltage from the load 200 to calculate the propagation coefficient change ratio k.

The second device 400 includes a pulse generator 430 and a measurement unit 450.

The pulse generator 430 generates a pulse signal and applies the pulse signal to the other end of the cable 100. The pulse generator 430 may apply a pulse having a constant voltage to the cable 100 at an arbitrary period. As an example, the pulse may be in the form of an impulse, a surge wave, a square wave, a sinusoidal wave, or the like, but is preferably an impulse. The type and period of the pulse may be selected by the user and are not limited to those described.

The measuring unit 450 measures the pulse signal applied from the pulse generator 430 to the cable 100. In addition, the measurement unit 450 measures the reflected pulse signal when the pulse signal applied to the cable 100 has been reflected. The measured pulse signals may be transferred to the display unit 500 under the control of the controller 600 and displayed on the display unit 500. The measuring unit 450 may be implemented with an oscilloscope.

The second device 400 may further include a connector having three terminals for connecting the pulse generator 430 and the measurement unit 450 to the other end of the cable 100. The connector may be, for example, an auxiliary cable having a resistance value of 50 Ω.

The second device 400 is a time domain reflectometer (TDR) that attempts to identify a cable connection state and a defect by measuring information about a reflection point object from a reflection waveform in which an electrical signal transmitted through a cable is reflected back to an object. Can be. The second device 400 measures the length of the cable in the manner described above.

On the other hand, the second device 400 is pressed by a button provided in the aging change measurement system 1000 or the second device 400, by the propagation coefficient preset in the storage unit (not shown) and the second device 400 By comparing the measured actual propagation factor, it can be set to automatically calculate the propagation coefficient change ratio k of the cable.

The display unit 500 may display various signals, graphs, values, and the like. The various signals include an applied pulse signal and a reflected pulse signal measured by the measuring unit 450. The signal may be displayed as a waveform on the display unit 500. The graph may be, for example, a graph of FIGS. 5 and 6 to be described later. The value may be a value of various elements constituting the load 200 or a value of a time constant.

The secular variation measuring system 1000 may include a single display unit 500, but each of the first device 300 and the second device 400 may include a separate display unit.

The controller 600 controls the respective components included in the aging change measurement system 1000 of the cable as a whole.

The control unit 600 displays the display unit 500 to display the type of the load 200 calculated by the first device 300, the type and value of elements constituting the load 200, and the time constant of the load 200. Can be controlled. In this case, the controller 600 may control the display unit 500 to display the calculated type of the load 200, the types and values of elements constituting the load 200 in a GUI environment. As an example, the controller 600 may display a circuit diagram connected in series with a resistor and an inductor, and control the display 500 to further display values and time constants of the resistor and the inductor on one side of the circuit diagram.

When the control unit 600 calculates the propagation coefficient change ratio k of the cable in the second device 400, the controller 600 displays a voltage waveform according to distance to represent a preset propagation coefficient, and displays the actual measured propagation coefficient. The display unit 500 may be controlled to display a voltage waveform according to a distance in order to produce a display.

The controller 600 may control the display 500 to display the calculated propagation coefficient change ratio k.

Although not shown in FIG. 1, the secular change measuring system 1000 of the cable may further include a storage unit (not shown). The storage unit (not shown) stores a program, data, etc. for automatically calculating or displaying various values of the first device 300 and the second device 400.

In addition, the storage unit (not shown) stores the propagation coefficient. Accordingly, the controller 600 may calculate the propagation coefficient change ratio k by comparing the propagation coefficient prestored in the storage unit with the actual measured propagation coefficient.

In addition, although not shown in FIG. 1, the secular variation measuring system 1000 of the cable may further include a user input unit (not shown). The user input unit (not shown) may include an operation panel for receiving numbers, letters, symbols, and the like. The user input unit (not shown) may receive various commands of the user in the form of a touch screen through the LCD screen. The user input unit (not shown) may receive an arbitrary propagation factor from the user, which may be stored in a storage unit (not shown). The arbitrary propagation coefficient means a propagation coefficient arbitrarily input by the user in consideration of this since the range of the propagation coefficient is roughly predictable as the cable is used.

Aged Deterioration of a cable refers to degradation of cable performance or function due to corrosion, abrasion, changes in physical properties, including natural deterioration, over a long period of time. According to the present invention, the degree of aging change of the cable can be confirmed using the propagation coefficient change ratio k of the cable. Since the propagation speed of the cable changes according to the aging change of the cable, by checking the aging change of the cable, the propagation speed of the cable can also be confirmed.

Although the aging change measurement system 1000 of the cable is described as being implemented in a single product form, the aging change measurement system 1000 of the cable may be a form in which separate products are combined with each other. As an example, the first device 300 and the second device 400 are separate products from each other, and the display unit 500 and the control unit 600 may be any of the first device 300 and the second device 400. It may be included in one or in a form that is separated from each other.

2 to 4B are diagrams for explaining the size, type, and time constant calculation method of the load.

Referring to FIG. 2, a connection relationship between the cable 100 and the load 200 is shown.

The source impedance of the cable 100 is fixed at 50 [Ω]. The secular variation of the cable 100 according to the present invention can be measured only when the load 200 is a load composed of a resistor and an inductor or a load composed of a resistor and a capacitor, and a load of only a resistor, a load of an inductor only, and a capacitor only. In the case of a load, it is not possible to check the secular variation of the cable according to the invention. The inductor-capacitor load is the same because either the inductor alone or the capacitor alone. According to the present invention, the secular variation of the cable can be measured using the propagation coefficient change ratio while the load is connected.

3A and 3B, an example of a load composed of a resistor and an inductor is described. When a resistor and an inductor are connected in series as shown in FIG. 3A, the time constant is expressed by Equation 1 below.

When a resistor and an inductor are connected in parallel as shown in FIG. 3B, the time constant is expressed by Equation 2 below.

The analysis of the type of the load 200, that is, whether the resistor and the inductor are connected in series or in parallel with each other, is performed when the DC voltage is applied to the first device 300 and when the AC voltage is applied. If the resistance value is significantly different, or if the resistance of the DC voltage is close to zero, the resistance and the inductor are considered to be connected in parallel.

4A and 4B, an example of a load composed of a resistor and a capacitor is described. When a resistor and a capacitor are connected in series as shown in FIG. 4A, the time constant is expressed by Equation 3 below.

When a resistor and a capacitor are connected in parallel as shown in FIG. 4B, the time constant is expressed by Equation 4 below.

The identification of the type of the load 200, that is, whether the resistor and the capacitor are connected in series or in parallel with each other, is performed when the direct current voltage is applied to the first device 300 and when the AC voltage is applied. If the resistance values are significantly different, or if the resistance of the DC voltage is near infinity, the resistors and capacitors can be considered in series.

As such, the first device 300 may calculate the size of the load 200, the type of the load 200, and the time constant of the load 200.

Next, a method of calculating a propagation factor using the second device 400 will be described.

The cable length that can be calculated by the second device 400 is as shown in Equation 5 below.

Here, D is the length of the cable 100, the propagation coefficient (V _π ) is the propagation coefficient of the cable 100 set in the second device (400). Specifically, the propagation coefficient V _π represents a ratio relative to the speed of light in a vacuum, and has a value less than one. V _L is 3 * 10 ⁸ [m / s], which is the speed of light in a vacuum. t _L is the time it takes for the cable signal to bounce back to the origin, and it takes t _L / 2 for the signal to reach the actual distance. Referring to Equation 5, since it is known that the length of the cable, that is, the distance, is determined according to the propagation coefficient V _π set in the second device 400, it is necessary to confirm the accurate propagation coefficient V _π .

As described above, the load curve of the second device 400 is determined by the load characteristics (size and type of load), and the propagation speed, that is, the propagation coefficient of the second device 400 may be obtained using the load curve.

In the case of a load 200 in which a resistor and an inductor are connected, the load curve decreases with a negative slope, and the ratio of the amount decreased after 1 τ elapses at any point after the reduction starts and the amount decreased after 2 τ elapses Is always the same.

Similarly, for a load 200 in which a resistor and a capacitor are connected, the load curve increases with a positive slope, and increases after an amount of 1 τ elapsed at any point after the start of the load curve and after 2 τ elapsed. The ratio of quantities is always the same.

5 is a graph illustrating a load curve of a circuit in which a resistor and an inductor are connected.

Referring to FIG. 5, the horizontal axis D represents the length of the cable, that is, the distance, and the vertical axis ρ represents the voltage.

In FIG. 5, a graph section that decreases exponentially is defined by Equation 6 below.

As described above, the ratio of the change of ρ of D ₁₂ and D ₂₃ according to 1τ interval is always expressed by Equation 7 below.

If the actual propagation factor is k times larger than the propagation factor set in the second device 400, the ratio of the amount of change of ρ measured on the same distance, that is, the cable having the same length is expressed by Equation 8 below.

Here, k represents a propagation coefficient change ratio and may be calculated by Equation 9 below.

6 is a graph showing a load curve of a circuit in which resistance and capacitance are connected.

Referring to FIG. 6, a graph section that increases exponentially is represented by Equation 10 below.

Similarly, as described above, the ratio of the amount of ρ change between D ₁₂ and D ₂₃ according to the 1τ interval is always expressed by Equation 11 below.

Similarly, if the actual propagation coefficient is k times larger than the propagation coefficient set in the second device 400, the ratio of the amount of change of ρ measured on the same distance, that is, the cable of the same length is expressed by Equation 12 below.

Here, k represents the propagation coefficient change ratio, and likewise, it can be calculated by the above equation (9).

As shown in FIG. 5 and FIG. 6, according to the present invention, a propagation coefficient change ratio k representing how much a change in propagation coefficient calculated by the second apparatus 400 is compared with a known propagation coefficient. By confirming, the degree of secular variation of the cable 100 can be grasped. In addition, since the propagation speed of the cable 100 varies according to the degree of secular variation of the cable 100, according to the present invention, the propagation speed of the cable 100 can also be confirmed.

On the other hand, unlike in FIGS. 5 and 6, if the interval of 1τ is very large and it is difficult to check the waveform on the display unit 500, the interval of 1τ may be reduced by a predetermined scale. In this case, the equation is as shown in Equation 13 below.

As described above, the propagation coefficient change ratio k is expressed by Equation 14 below.

Where S is the reduction scaling factor.

Meanwhile, although the propagation coefficient may be calculated using the equation as described above, noise may be mixed in the actually calculated propagation coefficient. Therefore, it is necessary to consider the noise component generated for more accurate calculation of the propagation coefficient. That is, by analyzing the noise component in the data for calculating the actual propagation coefficient and reflecting it in the actual data value, it is possible to compensate for the error due to the noise.

The noise component to be actually generated may be modeled as in Equation 15 below.

Where m is a positive integer greater than 100 and at least 100 times

It averages more than 100 data and extracts the noise with the difference between the waveform where the noise is collected to a certain level and the actual data where the noise is intact, and extracts the magnitude and phase of each order by developing the Discrete Fourier Tranform (DFT). The equation is shown in Equation 16 below.

Inverse Discrete Fourier Tranform (IDFT) is converted to time value again. The formula is as follows.

The result calculated by Equation 17 is corrected by reflecting the error (Equation (18)) at the origin and 1 with Equation (19).

7 is a flowchart illustrating a method of measuring the secular variation of a cable.

Referring to FIG. 7, the method for measuring the secular variation of the cable may be performed by calculating the time constant of the load in the first apparatus 300 (S705 to S740) and the time constant calculated by the second apparatus 400. Steps S745 to S765 are performed to calculate the propagation coefficient change ratio k using.

In the method for measuring the aging change of the cable, the following steps are performed in a state in which the cable 100 is connected to the load 200, that is, embedded.

 In the method for measuring the secular change of the cable, a DC voltage is applied to the first device 300 connected to the cable 100 (S705) and the voltage and current of the load 200 are detected (S710).

An AC voltage is applied to the first device 300 connected to the cable 100 (S715). When an AC voltage is applied to the load 200, it is determined whether the Q value is 1 (S720). Here, Q represents the reactance component X of the load 200 with respect to the resistance component R of the load 200.

If the Q value of the load 200 is not 1, the frequency of the AC voltage to be applied is varied (S725), and then the AC voltage is applied to the load 200 again to determine whether the Q value is 1 (S720).

As such, if the Q value of the load 200 is not 1, the frequency of the alternating voltage to be applied is repeatedly changed until the Q value of the load 200 is 1 (S715, S720, S725).

However, even if the Q value of the load 200 is not 1, the controller 600 may be set to determine that the Q value of the load 200 is 1 if it is within a threshold range preset based on 1.

If the Q value of the load 200 is 1, the voltage and current of the load 200 at this time are detected (S730).

Meanwhile, steps S715, S720, and S725 may be performed first, and then steps S705 and S710 may be performed.

Based on the values previously performed in the steps, the size and type of the load 200 are analyzed (S735). Specifically, it is analyzed whether the load 200 is a series / parallel connection of a resistor and an inductor, or a series / parallel connection of a resistor and a capacitor, and calculates a value of each element included in the load 200.

Based on this, the time constant of the load 200 is calculated (S740). The calculated time constant is a parameter for obtaining the propagation coefficient change ratio k.

Thereafter, the second device 400 receives an arbitrary propagation factor (S745).

The second device 400 applies the pulse generated by the pulse generator 430 to the load 200 through the cable 100 (S750). In this case, the pulse may be an impulse, and the impulse may be a source for detecting the reflection voltage required for calculating the actual propagation coefficient.

The second device 400 measures the reflected voltage at the measuring unit 450 (S755). In detail, the second device 400 measures the reflected voltage by extracting the reflected voltage curve of the load 200.

The second device 400 repeatedly measures the reflected voltage at least 100 times, and averages the reflected voltage at least 100 times to calculate the average reflected voltage (S760). This is for the accuracy of the measurement, the second device 400 may increase the number of measurements and then filter the average value.

The second device 400 receives the input from the user and compares the propagation coefficient previously stored in the storage unit (not shown) with the propagation coefficient actually measured through the reflected voltage to calculate the propagation coefficient change ratio k (S765).

According to the method, since the propagation coefficient can be calculated using the propagation coefficient change ratio k while the load is connected to the cable 100, it is not necessary to cut the cable, and the secular variation of the cable is relatively easy, Fault points can be diagnosed.

On the other hand, the method for measuring the secular variation of the cable may not perform step S760, unlike shown in FIG.

8 is a flowchart illustrating a method of measuring the secular change of a cable by reflecting the noise actually generated.

Referring to FIG. 8, in the method for measuring the secular variation of the cable, the steps S805 to S860 are the same as the steps S705 to S760 of FIG. 7, and thus redundant description will be omitted.

The second device 400 calculates an average reflection voltage (S860), and extracts a noise component by subtracting the average waveform of the average reflection voltage from a source waveform of an arbitrarily set propagation coefficient (S865).

The second device 400 performs frequency analysis through a Fourier transform (S870). In this case, both Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT) are possible.

The second device 400 analyzes the noise component generated on the time axis in consideration of the noise component in the measured reflected voltage (S875).

The second device 400 reflects the analyzed noise component, compares the propagation coefficient pre-stored in the storage unit (not shown) with the input from the user, and the propagation coefficient actually measured through the reflected voltage, and thus the propagation coefficient change ratio (k). ) Is calculated (S880).

9 is a flowchart for explaining a method for diagnosing a failure point using a propagation coefficient change ratio.

Referring to FIG. 9, in the method for diagnosing a failure point using a propagation coefficient change ratio, a failure point of a cable is measured using a predetermined predetermined propagation factor (S910).

The propagation coefficient change ratio k is calculated by comparing the predetermined propagation coefficient with the measured propagation coefficient (S915).

The actual failure point is calculated by multiplying the determined failure point by using the predetermined random propagation coefficient by the calculated propagation coefficient change ratio k, in operation S920.

According to the present invention, the failure point of the cable can be easily calculated by calculating the propagation coefficient change ratio k.

FIG. 10A is a diagram illustrating propagation coefficients actually calculated using a coaxial cable of LPMS in the second apparatus, and FIG. 10B is an enlarged view of region B of FIG. 10A.

In FIG. 10A, the region where the waveform is distorted in the middle, that is, the region A becomes the through portion of the cable 100, and the portion where the graph increases exponentially is the region B, that is, the load end. If the load stage is enlarged, the shape as shown in Fig. 10b can be obtained.

Referring to the shape of the load stage of FIG. 10A, it can be seen that the load shown in FIG. 10A is a load to which a resistor and a capacitor are connected.

The load characteristics of the LPMS V-106 cable are shown in Table 1 below.

TagNo PNLNo Measuring frequency R C V-106 LPMS 1000 [Hz] 38792000 [Ω] 3.5342 [nF]

TagNo denotes a model name and PNLNo denotes a cable type, respectively. When an AC voltage is applied to the load 200, the measured frequency of the AC voltage when the Q value is 1 is 1000 Hz. The values of the resistance and capacitance calculated by the first device 300 of the system 1000 are shown in Table 1.

When the resistance values and the capacitor values of Table 1 are applied to the equations described in FIG. 6, the results of Table 2 may be calculated.

Settings VP Time constant Equidistance Proportional Propagation Factor Calibration Vp 0.6522 1.8E-07 17.27556 1.031323564 0.672629

As can be seen from Table 3, when the cable 100 is measured by setting an arbitrary propagation coefficient (setting Vp) to 0.6522, the propagation coefficient, that is, the propagation coefficient change ratio k, is about 1.031. It can be seen that the calibrated Vp) is about 1.03 times faster.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It goes without saying that the example can be variously changed. Therefore, various modifications may be made without departing from the spirit of the invention as claimed in the claims, and such modifications should not be individually understood from the technical spirit or outlook of the invention.

100: cable 200: load
300: first device 400: second device
500: display unit 600: control unit
1000: cable secular change measuring system

Claims (16)

Load;
A cable connected to one end of the load;
A DC voltage and an AC voltage are applied to the load to determine the types of devices included in the load, the values of the devices, and a connection relationship between the devices, and to calculate a time constant by the devices. A first device; And
And a second device that checks a reflected voltage from the load and calculates a propagation coefficient change ratio when an impulse voltage is applied to the load through the other end of the cable. The method of claim 1,
The first device and the second device,
And calculating the time constant and the propagation coefficient change ratio, respectively, while the load is connected to the cable. The method of claim 1,
The propagation coefficient change ratio is
And a propagation factor ascertained through the reflected voltage with respect to the set propagation factor. The method of claim 3,
The second device,
And repeating the checking of the reflected voltage according to the application of the impulse voltage more than a predetermined number of times, thereby improving the accuracy of calculating the propagation coefficient change ratio. The method of claim 3,
And a user input unit configured to receive the set propagation factor. The method of claim 1,
And a display unit configured to display the identified reflected voltage. The method of claim 1,
The load,
And a RL load comprising a resistor and an inductor and an RC load comprising a resistor and a capacitor. The method of claim 7, wherein
The connection relationship between the elements,
The load is determined as the RL load,
If the difference between the first resistance value measured when the direct current voltage is applied to the first device and the second resistance value measured when the AC voltage is applied to the first device is equal to or greater than a predetermined value, the resistance and the inductor are connected in parallel. Secular change measuring system. The method of claim 7, wherein
The connection relationship between the elements,
The load is determined as the RL load,
If the first resistance value is 0, the cable aging change system, characterized in that the parallel connection of the resistor and the inductor. The method of claim 7, wherein
The connection relationship between the elements,
The load is determined to be an RC load,
When the difference between the first resistance value measured when the direct current voltage is applied to the first device and the second resistance value measured when the AC voltage is applied to the first device is equal to or greater than a predetermined value, the resistor and the capacitor are connected in series. Secular change measuring system. The method of claim 7, wherein
The connection relationship between the elements,
The load is determined to be an RC load,
If the first resistance value is infinity, the cable aging change system, characterized in that the series connection of the resistor and the capacitor. The method of claim 1,
The second device,
And analyzing the noise component of the reflected voltage and applying the analyzed noise component to the propagation coefficient change ratio calculation. The method of claim 1,
The cable aging change measurement system,
Cable aging change measurement system, characterized in that for performing the failure point diagnosis using the calculated propagation coefficient change ratio. In the cable aging measurement method,
Detecting a first load voltage and a first load current according to the DC voltage application when a DC voltage is applied to a load in a state where a cable is connected;
Determining whether a reactance (X) with respect to the resistance (R) of the load is 1 when an AC voltage is applied to the load while the cable is connected;
Detecting a second load voltage and a second load current if the reactance (X) of the resistance (R) of the load is 1;
Checking the size and type of the load based on the first load voltage, the first load current, the second load voltage, and the second load current;
Calculating a time constant of the load according to the confirmation;
Inputting and storing propagation coefficients;
Checking a reflected voltage reflected from the load after applying an impulse voltage to the load through the cable; And
Calculating a propagation coefficient change ratio using the propagation coefficient and the identified reflected voltage;
And the propagation coefficient change ratio is a propagation coefficient confirmed through the reflected voltage with respect to the set propagation coefficient. 15. The method of claim 14,
And repeating the check of the reflected voltage according to the application of the impulse voltage more than a predetermined number of times. 15. The method of claim 14,
Analyzing the noise component of the reflected voltage;
The analyzing of the noise component may include applying the analyzed noise component to the propagation coefficient change ratio calculation.

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