KR101328994B1 - Volume Electrical Resistivity Equipment for Cable in NPPs - Google Patents

Abstract

The present invention is a device for monitoring the state of the cable installed in the nuclear power plant, measuring the volume resistivity of the cable insulation material (polymer) to determine the deterioration degree according to long-term use of the nuclear power cable volume resistivity measuring device and the measurement using the same It is about a method.
The configuration consists of a jig (1) for measuring cable samples, a voltmeter (2), an ammeter (3), and a power supply (4).

Description

Volume electrical resistivity measuring apparatus for nuclear power cables and measuring method using the same {Volume Electrical Resistivity Equipment for Cable in NPPs}

The present invention relates to a nuclear power cable volume resistivity measuring apparatus for monitoring the deterioration state by measuring the volume resistivity of the cable insulation material used in nuclear power plants and a measuring method using the same.

 As a method for monitoring the state of nuclear power cables studied domestically and internationally, methods using the physical, chemical and electrical properties of cable insulation materials have been proposed.

Thermogravimetric analysis (TGA) using dual chemical properties, and elongation at break (EAB) measurement using physical properties are widely used in Korea.

In particular, the EAB method based on the tensile test is internationally standardized, and is generally a useful condition monitoring method and has been recognized as a standard for many condition monitoring methods. However, the EAB method requires a very large number of samples in a destructive manner in terms of cables, and it is difficult to measure when crosslinked polyethylene (XLPE), rubber material and when the test material is a mixture of two or more different layers.

In addition, other state monitoring technologies developed so far are not applicable to all kinds of cables, and only one technology is difficult to accurately monitor the state. In particular, the service life evaluation of cables using chemical or physical properties is affected by the material used in the outer sheath and insulation of the cable and its characteristics, and the methods using the electrical properties are accurate with the measured values and cable degradation. It has a disadvantage of difficult correlation.

Therefore, it is not only applicable to various kinds of cables of nuclear power plant, which is the ideal cable condition monitoring method proposed by the International Atomic Energy Agency, but also it is easy to derive correlation between measured value and deterioration and relatively easy to monitor and measure volume resistivity. It was necessary to develop the monitoring and analysis method of nuclear power cable.

This technology develops analytical methods that can be combined with TGA and EAB methods that are widely used in Korea through continuous research and development. The demand for new condition monitoring technology is expected to increase due to the development of materials.

In Korean Patent Publication No. 1003304690000 (20020315), a one-side side inspection circuit board having a plurality of connecting electrodes disposed on one side of an inspection target electrode and having a plurality of connecting electrodes on the surface thereof, and the one side side inspection A connector layer member formed on a surface of a circuit board for a circuit and made of a conductive elastomer, the connector layer member having one surface of each of a plurality of connection electrode groups adjacent to each other in the connection electrodes. The electrodes are connected to and electrically connected to the connecting electrodes at the same time, and at the same time, the other surfaces of the electrodes to be tested are composed of a plurality of electrodes that are adjacent to each other among the electrodes to be tested on one surface of the circuit board to be tested. In contact with these and electrically connected to the measurement state, and for the connection belonging to the connection electrode group in the measurement state. By measuring one of two of the poles as an electrode for supplying current and the other as an electrode for voltage measurement, the measurement of the electrical resistance with respect to one designated to-be-tested electrode specified from belonging to the said to-be-tested electrode group is performed. An electric resistance measuring apparatus of a circuit board is disclosed,

Korean Patent Publication No. 1008390390000 (20080611) includes a current applying unit for generating a continuously changing input current and applying the same to a power terminal of an electrochemical cell; detecting a voltage response signal of the electrochemical cell with respect to the analog input current. A voltage detector detecting at a predetermined time interval for a time; And linearly approximating the detected voltage response signal to obtain a voltage response function with respect to time, and calculating an internal resistance value of the electrochemical cell based on a change rate with respect to time of the input current, a slope and an offset of the voltage response function. And an internal resistance measuring unit for determining the detection time, wherein the detection time is set smaller than a time point when the magnitude of the voltage response signal with respect to the input current exceeds a predetermined threshold voltage. Listed,

The publication No. 1007759160000 (20071106) is a device for measuring the conductivity of a metal specimen, the specimen support 32 is installed on the upper side of the base 10 of the flat form and the specimen is placed; A specimen holder 30 which is moved along the width of the specimen, is installed at the center of the pedestal 10, and fixes both sides in the width direction of the specimen; A specimen fixing rod moving lever 31 which moves the specimen fixing table 30 to both sides in the width direction and is installed at one side of the specimen fixing table 30; An application electrode portion 40 which is formed of a metal capable of applying a current and is in contact with both ends of the longitudinal direction of the specimen, and is moved in the left and right directions; An applying electrode portion moving lever 43 for moving the applying electrode portion 40 to the left and right in the longitudinal direction of the specimen; A measuring electrode transfer part 20 which is coupled to a fixing column on an upper side of the pedestal 10 and moves up and down; A measurement electrode transfer part moving lever 21 for moving the measurement electrode transfer part 20 up and down; A measurement electrode 50 installed below the measurement electrode transfer part 20 and moved left and right, and having a lower end formed of a metal material to measure a voltage applied to the specimen anode; Measuring the electrical conductivity using the four-terminal resistance measurement method comprising the; moving the measurement electrode 50 to the left and right, the measurement electrode moving lever 51 provided on one side of the measuring electrode transfer unit 20 Device is described,

Korean Laid-Open Patent Publication No. 2020090008245 (20090818) discloses a resistance meter control unit for measuring position and resistance of heater wires and an NG signal monitoring, and an PLC control control unit for NG position tracking and an extruder that controls the NG position. It can be seen that the electric resistance measurement and inspection device of the heater wire, characterized in that the control and the control unit by monitoring and tracking the measured value made by including the extrusion stop.

As a method of monitoring the state of nuclear power cables studied domestically and internationally, methods of using physical, chemical and electrical properties of cable insulation materials have been proposed, but the volume resistivity of cable insulation materials used in nuclear power plants This is a problem that the present invention has to solve the problem that there is no case applied to the country as necessary equipment to monitor the deterioration state by measuring the.

In order to solve the above problems, in the present invention, the microcurrent (nA or pA) flowing inside the high-resistance (10 ¹⁴ Ω · m or more) material with respect to the degraded insulation material of the nuclear power cable is precisely minimized while minimizing external noise and errors. By developing the measuring equipment, the state of the cable can be accurately measured by measuring the change in the insulation performance of the cable insulation material and the shell which changes with time in various environmental conditions of the nuclear power plant as the change in the volume resistivity, which is an electrical variable. It is an object of the present invention to provide an apparatus for measuring volume electrical resistivity of a nuclear power cable to be monitored and a measuring method using the same.

The present invention is a method of using the volume resistivity, which is an absolute value inherent to a material that does not change under any measurement conditions or properties, such as the shape, dimensions, and location of an insulating material. Used as a measure of the volume resistivity of insulating materials,

In the future, it will help to ensure the safest and most scientific management of nuclear power cable life expectancy through the monitoring and deterioration evaluation of nuclear power cables and contribute to improving the cable degradation management evaluation system of nuclear power plants in Korea.

1 is a flow chart of a nuclear power cable volume resistivity measuring apparatus of the present invention
Figure 2 detailed view of the jig for measuring the volume resistivity of the present invention
Figure 3 Jig plane detail view for measuring the volume resistivity of the present invention
Figure 4 jig picture for measuring the volume resistivity of the present invention
5 is a photograph of the apparatus for measuring the volume resistivity of a nuclear power cable of the present invention
Figure 6 is a state photograph experiment of the apparatus for measuring the volume resistivity of the nuclear power cable of the present invention

The present invention accurately measures the change in the insulation performance of the cable insulation and the outer sheath that changes over time in various environmental conditions of a nuclear power plant by measuring the change in volume resistivity, which is an electrical variable, to monitor the state of the cable. It relates to a cable volume resistivity measuring apparatus and a measuring method using the same.

 This method is applicable to various types of cables used in nuclear power plants, and it is relatively convenient to measure compared to other methods and can be performed in a short time (within 30 seconds). For this purpose, it is necessary to develop a unique volume resistivity measuring device considering the characteristics of the insulation material of nuclear power cables.

The present invention is mainly used to study the condition monitoring method of the nuclear power cable and to evaluate the degradation of the cable acquired at the nuclear power plant site, and if the current flowing inside the nuclear power cable insulation material is measured, the volume resistivity is automatically adjusted through a program using the following formula. Is calculated. This automatically calculated volumetric electrical resistivity is a material-specific absolute value that does not change under any measurement conditions or properties, such as the shape, dimensions, and location of the insulating material.

Where ρ is the volume resistivity, V is the value of the voltmeter, I is the value of the ammeter, S is the electrode area, t is the cable sample thickness, and R is the volume resistance . This measuring device is a device that can accurately measure the micro measurement current (nA or pA) flowing inside the high-resistance material of more than 10 ¹⁴ [Ω · m] and strengthens the size and insulation of upper and lower electrodes and minimizes external noise. The width of the measurement voltage was adjusted (up to 1,000 V) to allow electrode size selection according to the area of the cable sample.

Through the development of measuring devices, it was possible to study the method of monitoring the status of nuclear power cables using the volumetric electrical resistivity. This will help you to be the safest and most scientifically managed.

It will also contribute to improving the cable degradation management evaluation system in Korea's nuclear power plants.

The invention consists of a jig (1), a voltmeter (2), an ammeter (3) and a power supply (4) for measuring cable samples.

The jig (1) is for measuring the current flowing inside the cable sample is composed of three electrodes by adding two electrodes at the top and bottom center of the cable sample and a guard ring type electrode to remove the leakage current on the sample surface. have.

  Jig is the core technology of this equipment and it is necessary to remove the contact resistance between the electrode and the sample when measuring. Here, the surface is treated with silver or copper paste.

The electrode design of the jig for measuring the volume resistivity of a nuclear power plant cable is designed to reduce the size of the upper electrode diameter by 50mmΦ and to mitigate the effects of noise caused by the very small size and thickness measurement current (nA or pA) of the test cable sample. Made of 100mm Φ. In addition, by using a back light (Bakelite) with high insulation and mechanical strength to maintain the same distance between the upper electrode and the guard ring electrode, and to insulate the role between the guard ring and the upper electrode. Voltage application was designed so that the upper electrode was the cathode and the lower electrode was the anode. This can not only facilitate the insulation of the grounded guard ring electrode in a way that can limit the current flowing to the upper electrode small, but also reduce the size of the electrode, even in the event of an accident such as a short circuit or breakdown. Since it is small, it is a method that can significantly improve the safety of the device.

In relation to the measured temperature, the nuclear power plant cable has a unique resistance temperature coefficient, so the volume resistivity can be measured differently according to the ambient temperature. To prevent this, the ambient temperature must be kept constant. In addition, because the temperature of the specimen itself may increase due to the application of voltage in addition to the ambient temperature, check the temperature before measuring the volume resistivity and the specimen temperature after the measurement, and make sure that the temperature difference does not occur. The measuring device was devised and installed a cap for maintaining a constant temperature.

 When the voltage is applied, the current gain is generated according to the time when the DC is charged for more than 1 minute, which affects the volume resistivity, and sufficient time for stabilization of the specimen by residual charge after the end of the measurement (voltage interruption). Should be placed. When measuring the volume resistivity of the cable, measure the voltage 30 seconds after applying the voltage, and keep the power off time more than 1 minute.

In terms of shielding, it is important not to be influenced by the external power because the influence of external power change and noise caused by electromagnetic waves is large when measuring the volume resistivity. This equipment adopts the method of using a shield of aluminum material and a power filter to receive a constant power supply.

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1

The test cable sample 20 is connected to the jig 1, and at this time, the diameter of the negative electrode plate 12 is 50 mm Φ, and when power is supplied from the power supply 4, the voltmeter 2 connected to the power supply 4. ), Power is supplied to the ammeter (3) and the jig (1) to measure the current flowing inside the test cable sample 20,

 Measured 30 seconds after the voltage is applied, the power off time is maintained for more than 1 minute, the cover 30 is a rectangular parallelepiped outside the transparent resin and the inside is made of aluminum shielding material to prevent the external influence,

The temperature was maintained at the same temperature, and the measured signal was transferred to a central processor (not shown), and the volume resistivity was automatically calculated through a program using the following formula to measure the volume resistivity of the nuclear power cable.

next

ρ = R × S / t

R (volume resistance) = V / I

Where ρ is the volume resistivity, V is the value of the voltmeter, I is the value of the ammeter, S is the electrode area, and t is the cable sample thickness.

Example 2

The test cable sample 20 is connected to the jig 1, and at this time, the diameter of the negative electrode plate 12 is set to 100 mm Φ, and when the power is supplied from the power supply 4, the voltmeter 2 connected to the power supply 4. ), Power is supplied to the ammeter (3) and the jig (1) to measure the current flowing inside the test cable sample 20,

 Measured 30 seconds after the voltage is applied, the power off time is maintained for more than 1 minute, the cover 30 is a rectangular parallelepiped outside the transparent resin and the inside is made of aluminum shielding material to prevent the external influence,

The temperature was maintained at the same temperature and the measured signal was transferred to a central processor (not shown), and the volume resistivity was automatically calculated through a program using the following formula to measure the volume resistivity of the nuclear power cable.

next

ρ = R × S / t

R (volume resistance) = V / I

Where ρ is the volume resistivity, V is the value of the voltmeter, I is the value of the ammeter, S is the electrode area, and t is the cable sample thickness.

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

1 is a flow chart of the electric power cable volume resistivity measuring apparatus of the present invention, FIG. 2 is a detailed view of the jig for measuring the volume resistivity of the present invention, FIG. 3 is a plan detailed view of the jig for measuring the volume resistivity of the present invention, and FIG. Photograph of jig for resistivity measurement, FIG. 5 is a photograph of the apparatus for measuring the volumetric electrical resistivity of a nuclear power cable of the present invention, and FIG. 6 is a photograph showing a state photograph for experimenting with the apparatus for measuring the volumetric electrical resistivity of a nuclear power cable of the present invention. , Ammeter (3), power supply (4), connecting line (7), positive electrode plate (11), negative electrode plate (12), guide ring (13), lower insulator (14), upper insulator (15), test cable sample 20, the upper and lower wire connection portions 21 and 22, the cover 30 is shown.

Looking at the structure of the nuclear power cable volume electrical resistivity measuring apparatus of the present invention, as shown in Figure 1 to Figure 3, is composed of a power supply 4 and the voltmeter (2) and ammeter (3) connected to the power supply example, It consists of an ammeter and a voltmeter and a jig (1) connected to the power supply (4),

  The jig 1 has a rectangular parallelepiped shape, the outside of which is made of a transparent resin, and the inside of the jig 1 is installed in a cover 30 formed of a shield of aluminum, and a test cable sample 20 coated with silver or copper paste. ), Upper and lower wire connection portions 21 and 22 extending upward and downward in the center of the test cable sample 20, a positive electrode plate 11 disposed below the test cable sample 20, and the positive electrode plate ( A lower insulator 14 installed under the 11;

The negative electrode plate 12 disposed on the center of the test cable sample 20, the upper insulator 15 formed to surround the top and the outside of the negative electrode plate 12, and the outside of the upper insulator 15. Guide ring (13),

It can be seen that the structure consisting of the connecting wires 7 connected to one side of the upper and lower wire connection parts 21 and 22 and the guide ring 13.

Jig (1), voltmeter (2), ammeter (3), power supply (4), connecting line (7), positive electrode plate (11), negative electrode plate (12), guide ring (13), lower insulator (14), Upper insulator (15), test cable sample (20), vertical wire connection (21, 22), cover (30).

Claims (3)

delete In the volumetric electrical resistivity measuring apparatus for nuclear power cables,
Jig (1) for measuring resistivity, voltmeter (2) for measuring voltage across the sample, ammeter (3) for measuring current flowing inside the nuclear power cable insulation material, voltage for test voltage supply Consisting of a feeder (4),
The jig 1 has a rectangular parallelepiped shape, the outside of which is made of a transparent resin, and the inside of the jig 1 is installed in a cover 30 formed of a shield of aluminum, and a test cable sample 20 coated with silver or copper paste. ), Vertical wire connecting portions 21 and 22 extending upward and downward in the center of the test cable sample 20, a positive electrode plate 11 disposed below the test cable sample 20, and the positive electrode plate ( A lower insulator 14 installed under the 11;
The negative electrode plate 12 disposed on the center of the test cable sample 20, the upper insulator 15 formed to surround the top and the outside of the negative electrode plate 12, and the outside of the upper insulator 15. Guide ring (13),
Volume electrical resistivity measuring device for a nuclear power cable, characterized in that it comprises a connecting line (7) connected to one side of the upper and lower wire connection portion (21, 22) and the guide ring (13).
In the measuring method using the volumetric electrical resistivity measuring apparatus for nuclear power cables,
After connecting the test cable sample 20 to the jig 1, and when power is supplied from the power supply 4, the voltmeter 2, the ammeter 3 and the jig 1 connected to the power supply 4 are connected. While the power is supplied to measure the current flowing in the test cable sample (2),
Measured 30 seconds after the voltage is applied, the power off time is maintained for more than 1 minute, the cover 30 is a rectangular parallelepiped outside the transparent resin and the inside is made of aluminum shielding material to prevent the external influence,
The temperature is maintained at the same temperature and the measured signal is transferred to a central processor (not shown), and the volume resistivity measuring device for nuclear power cable is characterized by automatically calculating and measuring the volume resistivity through a program using the following formula. Measurement method

next

ρ = R × S / t
R (volume resistance) = V / I

Where ρ is the volume resistivity, V is the value of the voltmeter, I is the value of the ammeter, S is the electrode area, and t is the cable sample thickness.

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