KR20220084496A - Cable having real-time monitoring - Google Patents

Abstract

A cable having a real-time monitoring function according to the present invention includes a conductor; at least one insulator surrounding the conductor; a shell surrounding the insulator; and monitoring means for monitoring the state of the insulator or the outer shell in real time, wherein the monitoring means is disposed adjacent to the conductor, is symmetrically provided in the cable, and is composed of at least one optical cable.

Description

Cable with real-time monitoring function {CABLE HAVING REAL-TIME MONITORING}

The present invention relates to a cable, and more particularly, to a cable having a real-time monitoring function that can check the state of the cable in real time without physical destruction or chemical change.

In general, a cable is a conductive conductor coated with insulation for the safety of the user, and is used for transmitting electrical signals to various electrical devices including communication devices or for signals or instrumentation to control machines, and is used for various purposes in various places. is being used

In particular, such a cable is also used in a nuclear power plant, and when a nuclear power plant is used, a cable for transmitting power and electrical signals to various facilities of a nuclear power plant is one of the most important facilities. This is because, unlike other facilities in a nuclear power plant, cables are installed as basic infrastructure, and after installation, it is impossible to separate, dismantle and move without stopping the operation of the nuclear power plant. Therefore, it is necessary to continuously monitor the status and evaluate the lifespan of cables in nuclear power plants even after their installation in order to ensure continuous safety.

As described above, various methods are disclosed for monitoring the state of a nuclear power cable provided in a nuclear power plant.

For example, there is a method using the chemical properties of the cable first. In other words, it is a method to check the correlation between the change in the chemical properties of the cable insulation material and the deterioration. Specifically, there are infrared spectrophotometer, oxidation induction time, thermogravimetric analysis (TGA), and the like. Second, there is a method using mechanical properties. That is, there is a method of measuring changes in the compressibility, density, and elastic modulus of the cable. In particular, the EAB (Elongation at break) method using elongation among mechanical methods is commonly used as a method for evaluating the lifespan of a cable. However, the above-described chemical/mechanical methods have a disadvantage in that their use is limited depending on the cable material and they are all destructive methods.

On the other hand, an electric method of detecting the degree of change due to deterioration of the characteristics of the insulating material of the cable by applying power is also used. That is, methods such as insulation resistance, withstand voltage, dielectric loss, dielectric loss tangent, and partial discharge are used as electrical methods. However, the electrical method can be used for all materials, but has a disadvantage in that it is difficult to quantitatively and accurately display the correlation with deterioration.

After all, in order to predict the lifespan of a cable by the method according to the prior art described above, it is necessary to remove and disassemble the existing cable and check whether the insulation of the cable is damaged. However, it is difficult to carry out the test by removing the cable over the entire area of the nuclear power plant as described above. On the other hand, the method of testing cables only in some areas of a nuclear power plant entails a problem that all areas do not show the same aging due to the characteristics of a nuclear reactor from which radiation is emitted. In addition, in order to apply these cable removal and evaluation methods, it is necessary to stop the operation of the nuclear power plant. can be a huge burden on In addition, new cables need to be installed in old cables that have reached the end of their lifespan or are damaged and need replacement among cables already installed in existing nuclear power plants. It is difficult and costly.

In order to solve the above problems, the present invention provides a cable having a real-time monitoring function capable of monitoring the state of the cable without disassembling, dismantling, or disassembling the cable by detecting the damage and lifespan of the cable in real time.

In one embodiment, a cable having a real-time monitoring function includes a conductor; at least one insulator surrounding the conductor; a shell surrounding the insulator; and monitoring means for monitoring the state of the insulator or the outer shell in real time, wherein the monitoring means is disposed adjacent to the conductor, is symmetrically provided in the cable, and is composed of at least one optical cable.

The monitoring means of the cable having a real-time monitoring function further includes a monitoring device for monitoring the cable by receiving the monitoring tube reflected by the monitoring light incident on the optical cable.

The optical cable of the cable having a real-time monitoring function includes an optical fiber and an optical fiber protection unit surrounding the optical fiber.

The cable having a real-time monitoring function according to the present invention can evaluate the damage and lifespan of the cable without removing the cable already installed in a special place such as a nuclear power plant. Such evaluation can be performed in real time, and in particular, test evaluation is possible without any operation interruption of a nuclear power plant operating for a long period of time. Therefore, it has the effect of preventing a significant increase in cost due to the removal of the cable and the suspension of the operation of the nuclear reactor.

In addition, it is possible to take immediate action in case of damage by grasping the state of the cable in real time throughout the entire area of the nuclear power plant, and furthermore, by predicting the lifespan in advance, it prevents operation interruption, fire and explosion accidents caused by damage. has the effect of

1 is a cross-sectional view illustrating an internal configuration of a cable according to an embodiment of the present invention.
2 is a cross-sectional view illustrating an internal configuration of a cable according to another embodiment of the present invention.
3 is a cross-sectional view showing the internal configuration of cables having a monitoring means according to an embodiment of the present invention.
4 is a cross-sectional view showing the internal configuration of cables having a monitoring means according to another embodiment of the present invention.
5 is a schematic diagram showing the configuration of a monitoring system using a cable having a real-time monitoring function according to an embodiment of the present invention.

The present invention described below can apply various transformations and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, terms such as first, second, etc. may be used to distinguish and describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

In addition, when at least two different embodiments are described in the present application, all or part of the components may be used by merging and mixing with each other, even if there is no particular description within the scope not departing from the technical spirit of the present invention. .

The cable and its monitoring system described in the present invention have the purpose of being able to grasp the state of the cable in real time, and can be applied to, for example, a cable for nuclear power plants used in a nuclear power plant. That is, a cable for nuclear power plants used in a nuclear power plant, etc. must be able to provide not only radiation resistance, heat resistance, and chemical resistance, but also reliability according to long-term use. In particular, when a nuclear power plant is used for a long period of time, a cable for transmitting power and electrical signals to various facilities of the nuclear power plant is one of the most important facilities. This is because, unlike other facilities in a nuclear power plant, cables are installed as basic infrastructure, and after installation, it is impossible to separate, dismantle and move without stopping the operation of the nuclear power plant. Therefore, it is necessary to continuously monitor the status and evaluate the lifespan of cables in nuclear power plants even after their installation in order to ensure continuous safety.

However, in order to predict the lifespan of a nuclear power cable by the method according to the prior art, it is necessary to remove and disassemble the existing cable and check whether the insulation of the cable is damaged. However, it is difficult to carry out the test by removing the cable over the entire area of the nuclear power plant as described above. To avoid this, the method of testing cables in only some areas of a nuclear power plant entails a problem that all areas do not show the same aging due to the nature of the nuclear reactor from which radiation is emitted. In addition, in order to apply these cable removal and evaluation methods, it is necessary to stop the operation of the nuclear power plant. can be a huge burden on In addition, new cables need to be installed in old cables that have reached the end of their lifespan or are damaged and need replacement among cables already installed in existing nuclear power plants. It is difficult and costly. Therefore, in the following, a cable for nuclear power plants and a sensing system thereof for solving the above problems will be described.

1 is a cross-sectional view showing the internal configuration of a cable according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the internal configuration of a cable according to another embodiment of the present invention, and FIG. 3 is an embodiment of the present invention A cross-sectional view showing the internal configuration of cables having a monitoring means according to an example, FIG. 4 is a cross-sectional view showing the internal configuration of cables having a monitoring means according to another embodiment of the present invention, and FIG. It is a schematic diagram showing the configuration of a monitoring system using a cable having a real-time monitoring function according to an embodiment.

1 and 2 show the configuration of a cable used in a nuclear power plant and the like. The cable to be described below will be described by taking as an example a control cable capable of transmitting a control signal for controlling various devices of a nuclear power plant.

Referring to FIG. 1 , a cable 1 includes a conductor 10 therein, an insulator 20 surrounding the conductor 10 , and a sheath (sheath) 30 surrounding the insulator 20 . do. Here, when the cable 1 is a cable for a nuclear power plant, the outer shell 30 may be made of a radiation-resistant material in order to reduce damage and exposure to the conductor 10 due to radiation generated in a nuclear power plant, etc. On the other hand, the cable 1 having the real-time monitoring function corresponds to a so-called 'two-core' control cable having two conductors 10 .

Meanwhile, FIG. 2 has a structure similar to that of FIG. 1 , except for the number of conductors 10 . That is, the cable 3 according to FIG. 2 corresponds to a so-called 'seven core' control cable having seven conductors 10 . The cables shown in FIGS. 1 and 2 are merely illustrative, and for example, the number of conductors and the configuration surrounding the conductors provided in the cable can be appropriately modified.

Hereinafter, a monitoring means and a monitoring system capable of grasping the state of a cable having the above structure in real time will be described with reference to the drawings.

3 is a cross-sectional view showing the configuration of a cable having two cores provided with monitoring means.

Referring to FIG. 3 , since the conductor 10 , the insulator 20 , and the sheath 30 of the cable 100 having a real-time monitoring function have already been described, a repetitive description will be omitted.

The cable having a real-time monitoring function according to this embodiment is provided with a monitoring means for monitoring the state of the insulator 20 or the outer shell 30 in real time. The monitoring means is provided to grasp the state of the cable 100 in real time without accompanying any physical/chemical deformation of the cable, and furthermore, without accompanying disassembly, separation, and removal of the cable.

In the present invention, as described above, an optical cable is used to determine the status of a cable having a real-time monitoring function in real time.

That is, the monitoring means includes at least one optical cable 70 inside the cable 100 having a real-time monitoring function, and injects the monitoring light into the optical cable 70 and receives the reflected monitoring light. A monitoring device 310 (refer to FIG. 5) for monitoring a dedicated cable may be provided. The monitoring device 310 causes the monitoring light to be incident on the optical cable 70 and receives the scattered and/or reflected monitoring light to monitor whether the cable 100 having a real-time monitoring function is damaged.

Here, the reason for providing the optical cable 70 is to determine the aging degree, that is, the lifespan of the cable 100 having a real-time monitoring function. If the insulator is damaged due to aging of the cable, leakage current occurs, which may cause discharge. When the insulator or the outer shell is damaged by the electric discharge, the temperature rises locally in the damaged area. Therefore, if a portion in which the temperature is locally increased in the cable can be detected, the temperature increase area is detected as a damaged area or a shortened area, and immediate replacement and repair of the area is possible. Hereinafter, a configuration of a cable having a real-time monitoring function provided with an optical cable will be first examined, and then a monitoring system for monitoring a cable having a real-time monitoring function using the optical cable will be examined.

As shown in Figure 3 (A), the cable 100 having a real-time monitoring function is provided with at least one optical cable 70 therein. The optical cable 70 is provided on the outer shell 30 of the cable 100 having a real-time monitoring function, and may be preferably disposed adjacent to the conductor 10 .

The monitoring means uses the optical cable 70 and the monitoring device 310 to monitor the damage and lifespan of the insulator 20 and the sheath 30 of the cable 100 having a real-time monitoring function, and in particular, the conductor 10 The insulator 20 surrounding the is monitored. Whether or not the sheath 30 of the cable 100 having a real-time monitoring function is damaged is also important, but whether the insulator 20 surrounding the conductor 10 through which the actual control signal is transmitted is damaged and the lifespan is relatively more important. Therefore, the optical cable 70 is preferably provided adjacent to the insulator 20 of the conductor 10 when provided inside the cable 100 having a real-time monitoring function.

In addition, the optical cable 70 may be symmetrically provided in the cable 100 having a real-time monitoring function. When the cable 100 having a real-time monitoring function is damaged, looking at the damaged portion, both sides of the cable may be damaged, but damage tends to occur only on one side of the cable. Therefore, in the present embodiment, when the optical cable 70 is provided, a plurality of cables may be provided inside the cable 100 having a real-time monitoring function, and further, it is provided symmetrically in the cable to monitor the degree of damage in several places of the cable. can be When the optical cable 70 is symmetrically provided in the cable, it is easy to manufacture the cable 100 having a real-time monitoring function by preventing the center of gravity of the cable 100 having a real-time monitoring function from being tilted to one side, and furthermore, in real time Transport and installation of the cable 100 having a monitoring function can be made easily.

On the other hand, looking at the configuration of the optical cable 70, the optical fiber 40 and the optical fiber protection parts 50 and 60 surrounding the optical fiber 40 are provided. A plurality of optical fibers 40 are provided in order for the monitoring light to be incident by the monitoring device 310 to be described later, and further, an optical fiber protection unit is provided to prevent damage caused by radiation and various causes generated in a nuclear power plant.

The optical fiber protection unit prevents the optical fiber 40 from being damaged by various causes, such as radiation and dents occurring in a nuclear power plant. In this embodiment, the optical fiber protection unit may include at least one of a metal thin film and a polymer fiber.

Here, the metal thin film may be made of aluminum or copper in consideration of the radiation shielding effect. Radiation generated in the vicinity of the nuclear reactor of a nuclear power plant, especially β-ray, is shielded by dissipating a lot of energy by a thin metal film such as copper or aluminum. For example, when judging the radiation shielding effectiveness, HVL (Half Value Layer) is generally used. 'HVL' is defined as the thickness of the shielding member required to halve the intensity of radiation-induced energy. That is, the smaller the 'HVL', the better the shielding effect. Conversely, the higher the 'HVL', the lower the shielding effect. If you look at the HVL value of copper for gamma ray energy that can be generated in a nuclear power plant, it corresponds to approximately 210 mm, and it can be said that it has somewhat superior characteristics compared to the HVL value of 216 mm of stainless steel used in conventional optical cables.

On the other hand, the aforementioned monitoring device 310 monitors a cable having a real-time monitoring function by using a monitoring light, and in particular, monitors the cable 100 having a real-time monitoring function using an OTDR (312, see FIG. 5). do. Specifically, a point at which heat is locally elevated in the cable 100 having a real-time monitoring function is identified through the monitoring waveform of the OTDR 312 . A monitoring system using the OTDR and its operation will be described in detail later. Therefore, it is preferable that the optical fiber protection unit surrounding the optical fiber 40 of the optical cable 70 is made of a material having excellent radiation shielding effect as well as excellent external heat conduction.

In this embodiment, looking at the thermal conductivity of copper and aluminum used as the material of the metal thin film constituting the optical fiber protection unit, they correspond to approximately 400 W/m K and 240 W/m K, respectively, which is the thermal conductivity of stainless steel used for conventional optical cables, etc. 15 It can be seen that it has a relatively high value compared to ~ 20W/m K.

In order to confirm the difference in thermal conductivity as described above, the present inventor conducted an experiment to find a local heat rise area of the cable 100 having a real-time monitoring function by providing an optical fiber protection unit with a metal thin film layer 50 composed of copper and stainless steel, respectively. carried out. As a result, when the temperature is sensed by the monitoring device with an optical fiber protection unit made of copper, it shows an error of approximately ±1°C or less from the actual cable temperature, but is provided with an optical fiber protection unit made of stainless steel to protect the monitoring device. When the temperature was sensed by means of a temperature sensor, the result was derived to indicate an error of approximately ±5°C from the actual cable temperature. After all, in order to determine the local heat rise point of the cable 100 having a real-time monitoring function by the monitoring device 310 having the OTDR 312, copper or aluminum having higher thermal conductivity than the conventional stainless steel is used. it is advantageous to do Preferably, since copper has a low HVL value for shielding radiation, it also has an excellent radiation shielding effect, and thus can be utilized as the metal thin film layer 50 of the optical fiber protection unit in this embodiment.

Meanwhile, the polymer fiber may be made of a polymer material including an aromatic group.

As described above, as the life expectancy of a nuclear power plant increases, the life of a cable also increases. In this case, the radiation dose required for the cable once installed in the nuclear power plant is also increasing. Therefore, it may not be possible to shield the entire amount of radiation by the above-described shielding by the metal thin film, and accordingly, by coating or taping a polymer material containing an aromatic ring in the molecule, radiation energy is further lost, and further, the polymer Oxidation can be suppressed by the film of the material.

Specifically, a polymer material including an aromatic group, including polyimide, has high heat resistance and radiation resistance that a general linear structure does not have due to a resonance structure. Therefore, if the optical cable is provided with a film made of a polymer material including an aromatic group, it is possible to protect the optical fiber from radiation as well as to prevent the optical fiber from aging due to high temperature. Furthermore, the film excellent in radiation durability serves as an oxygen barrier layer that prevents an oxidation reaction in which a polymer is oxidized by radiation. As a result, the film made of the polymer material including the aromatic group serves to prevent the optical fiber from being exposed to radiation, and furthermore, to prevent oxidation by the radiation that has once penetrated.

In this embodiment, the optical fiber protection unit may include at least one of a metal thin film and a polymer fiber.

In FIG. 3(A), the optical cable 70 has a metal thin film layer 50 as an optical fiber protection part, and in FIG. 3(B), the optical cable 72 is an optical fiber protection part, and a polymer layer 60 made of a polymer material including an aromatic group. will be provided Furthermore, in FIG. 3(C), the optical cable 74 shows a case in which both the metal thin film layer 50 and the polymer layer 60 made of a polymer material including an aromatic group are provided as an optical fiber protection part. In this case, the metal thin film layer 50 is provided to surround the optical fiber 40 , and the polymer layer 60 is provided on the outer periphery of the metal thin film 50 .

Meanwhile, FIG. 4 is a cross-sectional view showing the configuration of a cable 200 having seven cores provided with a monitoring means. In FIG. 4 , since the conductor 10 , the insulator 20 , and the sheath 30 of the cable 200 have already been described, a repetitive description will be omitted.

In this embodiment, although it is shown that the optical cable 70 is provided with four, it is not limited thereto, and for example, it is of course also possible to include less than two or more than six optical cables. In this case, as described above, the optical cable 70 may be symmetrically provided on the outer shell 30 .

The optical cable 70 of FIG. 4(A), the optical cable 72 of FIG. 4(B), and the optical cable 74 of FIG. 4(C) are each provided with a metal thin film layer 50 as an optical fiber protection part, an aromatic group A case in which the polymer layer 60 made of a polymer material including Since the metal thin film layer and the polymer material have been described above with reference to FIG. 3 , a repetitive description will be omitted.

Hereinafter, the configuration of the monitoring system for monitoring the state of the cable using the optical cable as described above will be described with reference to the drawings.

5 is a schematic diagram schematically illustrating a configuration of a sensing system for monitoring cables 100 and 200 having a real-time monitoring function.

Referring to FIG. 5 , the monitoring system 300 receives the monitoring light incident on the cables 100 and 200 and the optical cable 70 having a real-time monitoring function including at least one or more optical cables and receives the reflected monitoring light. A monitoring device 310 for monitoring the cables 100 and 200 having the real-time monitoring function is provided. Furthermore, it may further include a coupler 320 for selectively connecting the optical cable 70 and the monitoring device 310 and a splitter 330 for branching the cable 100 having a real-time monitoring function to be connected to a plurality of equipment. . In FIG. 5, reference numeral '305' corresponds to a control unit that generates a control signal through the cables 100 and 200 having a real-time monitoring function.

Specifically, the optical cable monitoring device 310 includes an optical time domain reflectometer (OTDR) 312 that incidents the monitoring light on the optical cable 70 and receives the reflected monitoring light, and an analysis device that interprets the waveform of the reflected monitoring light ( 314) may be provided.

The OTDR 312 generates monitoring light having a predetermined wavelength, and by making the monitoring light incident on the optical cable, the amount of light reflected and/or scattered at each point along the length direction of the optical cable is received again. Thereby, the analysis device 314 analyzes the distance distribution of the reflected monitoring light to determine the local heat rise area of the optical cable, and furthermore, it is possible to measure the distance to the point of the optical cable where the local heat rise occurs.

Specifically, the OTDR 312 is connected to the optical cable through the coupler 320 . The OTDR 312 may connect to each optical cable periodically, for example, or to each optical cable when damage is suspected. On the other hand, when monitoring light incident along one optical cable is scattered or reflected and received, peaks according to the length of each branched optical cable are shown at different distances from the OTDR. Therefore, the operator can determine which optical cable is the peak by checking the distance of the peak along each optical cable in the OTDR.

On the other hand, the input terminal of each equipment may be provided with a reflection means for reflecting the monitoring light, for example, the reflection filter unit 340 . The reflection filter unit 340 may be provided in an optical connector assembly (not shown) that connects the optical cable and each nuclear power plant equipment. In this way, when the reflection filter unit 340 is provided, the peak signal reflected at the end of the optical cable, that is, the input end of each nuclear power plant equipment, becomes larger, so that peak detection through the OTDR can be made more easily.

As described in detail above, the cable having a real-time monitoring function according to the present invention can evaluate the damage and lifespan of the cable without dismantling the cable already installed in a place such as a nuclear power plant. Such evaluation can be performed in real time, and in particular, test evaluation is possible without any operation interruption of a nuclear power plant operating for a long period of time. Therefore, it has the effect of preventing a significant increase in cost due to the removal of the cable and the suspension of the operation of the nuclear reactor.

In addition, it is possible to take immediate action in case of damage by grasping the state of the cable in real time throughout the entire area of the nuclear power plant, and furthermore, by predicting the lifespan in advance, it prevents operation interruption, fire and explosion accidents caused by damage. has the effect of

On the other hand, the embodiments disclosed in the drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

10: conductor 20: insulator
30: outer shell 50: metal thin film layer
60: high difference layer 70, 72, 74: optical cable
300: monitoring system 310: monitoring device
312: OTDR 314: analysis device

Claims (2)

conductor;
at least one insulator surrounding the conductor;
a shell surrounding the insulator; and
Including; monitoring means for monitoring the state of the insulator or the outer shell in real time;
The monitoring means is disposed adjacent to the conductor, is symmetrically provided in the cable, and includes at least one or more optical cables,
The optical cable is a cable having a real-time monitoring function including an optical fiber and an optical fiber protection unit surrounding the optical fiber. The method of claim 1,
The cable having a real-time monitoring function, wherein the monitoring means further includes a monitoring device for monitoring the cable by incident monitoring light to the optical cable and receiving the scattered and reflected monitoring light.

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