JP2001228195A - Light emission measuring sample, its manufacturing method, and light emission measurement method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make measurable a light-emission phenomenon based on electric field impression under a condition including a water-tree in an insulating material. SOLUTION: The tip of a metallic needle is previously inserted into a block 1 make of an insulating material from the upper face, and in a vacuum, the metallic needle is pulled out for forming a needle-shaped space 5, and then, the block 1 is shifted into the atmospheric pressure environment with the insertion port of the metallic needle immersed in water. In this way, the inside of the needle-shaped space 5 is filled with water and a water needle electrode 5a is formed. On the lower faced of the block 1, a flat electrode 2 is formed. In the atmospheric pressure environment, an electric field is impressed between the water needle electrode 5a and the flat electrode 2 for measuring the light- emission phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample used for evaluating an insulating material used for a power cable or the like, and more particularly to a sample capable of measuring a light emission phenomenon caused by application of an electric field in the presence of a water tree. The present invention relates to a luminescence measurement method using

[0002]

2. Description of the Related Art Conventionally, a water tree has been known along with an electric tree as a cause of insulation deterioration of a cable insulating material of a power cable. The tree is a branch-like breakdown portion generated in the solid insulator, and the water tree is formed by generating a local high electric field in the insulating material and supplying water to the portion. The form of water tree is a fine tree-like passage or space with room to be filled with water, and it is possible to observe the water tree when it is filled with moisture, but it can be seen when dried. It is known that it disappears and reappears when water is filled again.

[0006] It is known that a weak light emission phenomenon occurs in an insulator immediately before a partial discharge which is a precursor stage of generation of an electrical tree. This light emission phenomenon is called electroluminescence, and is considered to be a precursor to the premature breakdown of the cable insulating material. Therefore, since such electroluminescence can be effectively used for evaluation of durability of an insulating material, etc., much research has been conducted on a method of measuring an electroluminescence phenomenon related to an electric tree.

[0004]

However, almost no research has been conducted on whether or not luminescence phenomena such as electroluminescence or other chemiluminescence occur during the precursor stage before the generation of water trees or during the growth after the generation of water trees. No effective means and method have been established for measuring the luminescence phenomenon in the presence of water trees. The present invention has been made in view of such circumstances, and it is an object of the present invention to measure a light emission phenomenon caused by application of an electric field in the presence of a water tree.

[0005]

In order to solve the above-mentioned problems, a luminescence measurement sample according to the present invention is a luminescence measurement sample having two electrodes arranged to face each other with an insulating material interposed therebetween.
One of the electrodes is a water needle electrode formed by filling water into a needle-shaped space formed in the insulating material. The sample for luminescence measurement of the present invention, after removing the metal needle under vacuum from the insulating material into which the tip of the metal needle has been inserted, the insulating material is immersed in the insertion port of the metal needle. It is preferably manufactured by a method of forming a water needle electrode formed by filling a needle-like space in the insulating material with water by shifting to an atmospheric pressure atmosphere. Further, a luminescence measurement method according to the present invention is characterized in that an electric field is applied between the two electrodes in an atmospheric pressure atmosphere using the luminescence measurement sample according to claim 1.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIGS. 1A and 1B show an embodiment of a sample for luminescence measurement (hereinafter, also simply referred to as a sample) 21 of the present invention, wherein FIG. 1A is a perspective view and FIG. Reference numeral 1 denotes a rectangular parallelepiped block made of an insulating material, and a flat electrode 2 is provided on the lower surface of the block 1. As the constituent material of the block 1, for example, low-density polyethylene, cross-linked polyethylene, uncross-linked low-density polyethylene, or the like is preferably used, and as the material of the flat electrode 2, a carbon-containing conductive paste is preferably used. A lead wire 3 extending from an AC power source (not shown) is connected to an end of the flat electrode 2, and the lead wire 3 is fixed to the flat electrode 2 by an adhesive 4 such as an epoxy resin.

In the block 1, the upper surface 1a of the block 1
A needle-shaped space 5 is formed which extends in a direction perpendicular to the flat electrode 2 from the bottom to the bottom, and the inside of the needle-shaped space 5 is filled with water. The tip of the needle-shaped space 5 is located at a position separated from the surface of the flat electrode 2 by a predetermined length. A container 6 made of an insulating material is arranged above the block 1 so that the inside of the container 6 and the inside of the needle-shaped space 5 communicate with each other. The container 6 is also filled with water. In the present embodiment, a funnel-shaped inlet 6 a
The tip of the injection port 6a and the block 1 are provided.
Is joined to the opening of the needle-like space 5 on the upper surface 1a of the
It is bonded and fixed with an adhesive (not shown) such as an epoxy resin. Further, one end of a copper wire 7 is inserted into water in the container 6, and the other end of the copper wire 7 is connected to an AC power supply (not shown). Thereby, the container 6 and the needle-like space 5
The water inside is electrically connected to an AC power supply via a copper wire 7. Therefore, since the water in the needle space 5 acts as an electrode, the water in the needle space 5 may be hereinafter referred to as a water needle electrode 5a.

In designing the sample 21, there is no particular adverse effect if the width and height of the block 1 are too large, but it is useless if it is larger than necessary. If it is too small, creeping discharge is likely to occur when an electric field is applied. , For example, a width of 30 to 40 mm,
The height is preferably set within a range of 30 to 40 mm. The thickness of the block 1 is preferably set within a range of, for example, 3 to 5 mm.
If the distance between the tip of the water needle electrode 5a and the flat electrode 2 is too large, the light emission starting voltage increases, and if it is too small, dielectric breakdown easily occurs. If the distance from the tip of the water needle electrode 5a to the water surface in the container 6 is too short, water in the water needle electrode may evaporate during measurement, and if it is too long, creeping discharge occurs when an electric field is applied. Since it is easy, it is preferable to set it to about 70 to 80 mm.

The sample 21 of this embodiment can be manufactured by the following procedure. First, the block 1 in which the tip of the metal needle is inserted to a predetermined depth is formed. Specifically, since the insulating material forming the block 1 is a resin material, the block 1 may be cured with the tip of the metal needle embedded therein during molding. The metal needle is preferably made of, for example, stainless steel (steel) and has an outer diameter of 1.0 to 1.5 other than the tip.
mm is preferably used. Next, the needle-shaped space 5 is formed by removing the metal needle inserted into the block 1, and the needle-shaped space 5 is filled with water to form the water needle electrode 5a. Specifically, first, the container 6 is arranged on the surface of the block 1 on which the metal needle is inserted, and is adhesively fixed.
At this time, the container 6 is arranged so that the other end of the metal needle protruding from the block 1 passes through the inside of the injection port 6a of the container 6, and the tip of the injection port 6a is inserted into the metal needle insertion port on the surface of the block 1. To join. Then, after the container 6 is filled with water, the container 6 is placed in a vacuum dryer to start evacuation. When the inside of the vacuum dryer reaches a predetermined degree of vacuum, the metal needle is gradually pulled out to form a needle-shaped space 5. At this time, it is preferable that the block 1 is softened. For example, when the block 1 is made of cross-linked polyethylene, it is preferable to remove the metal needle while the block 1 is heated to about 90 ° C. After vacuuming for a certain time even after completely removing the metal needle,
The evacuation is stopped, and the vacuum dryer is immediately opened to bring the inside of the vacuum dryer to atmospheric pressure. In this manner, the needle-shaped space 5 is formed under vacuum, and the atmosphere in the container 6 is shifted to the atmospheric pressure atmosphere while the opening of the needle-shaped space 5, that is, the insertion port of the metal needle is submerged. Is pressed into the needle space 5,
The water needle electrode 5a is formed. The degree of vacuum of the atmosphere when the metal needle is removed is set to, for example, about 75 cmHg because a minute void is generated at the tip of the water needle formed when the metal needle is too low.

On the other hand, since the flat electrode 2 has a planar shape, it can be easily formed using a paste-like conductive material. For example, it can be formed by applying a paste-like conductive material to the lower surface of the block 1 with a spatula or the like. The flat electrode 2 may be formed before or after the water needle electrode 5a is formed. It is preferable that carbon is blended in the conductive paste constituting the flat electrode 2. In this case, fine powder having various particle sizes is used as long as the smoothness of the flat electrode 2 surface is not affected. And the production method is not particularly limited. Further, the content of carbon in the paste can be appropriately determined within a range in which the viscosity of the paste is not extremely increased to a degree that is inconvenient for forming an electrode. Note that the carbon-containing conductive paste may be mixed with various additives other than carbon. The flat electrode 2 may be formed using a conductive material such as a conductive silver paste containing no carbon. However, if the flat electrode 2 is formed using a carbon-containing material, the light emission phenomenon occurs on the surface of the flat electrode 2 when an electric field is applied. This is preferable for accurately measuring the light emission phenomenon caused by the application of the electric field between the two electrodes in the sample 21 because the occurrence of the light emission can be prevented.

FIG. 2 is a schematic view showing an embodiment of a measuring apparatus suitable for measuring a light emission phenomenon when an electric field is applied using the sample 21. As shown in FIG. This apparatus comprises a sample 21 and a condenser lens 1
3, a photomultiplier tube 18 optically connected to the case 16 via a monochromator (spectroscope) 17, and the relationship between applied voltage and emission intensity or emission wavelength and emission intensity. It basically includes a digital oscilloscope 19 for displaying and a photon counting system 10, and is configured to be able to measure a light emission phenomenon by a photon counting method (photon counting method). The case 16 is provided with a wiring mechanism for connecting wiring connected to each electrode of the sample 21 to an AC power supply (not shown). Further, this apparatus has a CCD camera 1 for observing the sample 21 in the case 16.
1, and a measurement system including a computer 12 for image-processing a signal from the CCD camera 11 is attached, and the light emission position of the sample can be measured.

The measurement must be performed in a state where the needle-shaped space 5 inside the block 1 is filled with water. In addition, since the water in the needle space 5 may flow backward to the container 6 under vacuum, the measurement is performed under atmospheric pressure. Specifically, first, the sample 21 to be measured is arranged at a predetermined position in the case 16 and the two electrodes of the plate-like electrode 2 and the water needle electrode 5a of the sample 21 are respectively connected to an AC power supply (not shown). . Case 1
The inside of 6 is set to the atmospheric pressure. Next, an AC voltage is applied between the two electrodes of the sample 21. When a light emission phenomenon occurs due to the application of a high electric field, the photons generated in the sample 21
The light is condensed by 3 and split by a monochromator (spectroscope) 17, and the emission intensity is measured by a photocounting method using a photomultiplier tube 18 and a photocounting system 10. Thus, the intensity of light generated in the sample 21 can be measured. Then, the relationship between the applied voltage and the light emission intensity can be obtained by measuring the light emission intensity of the sample 21 while changing the voltage value applied from the AC power supply continuously or discontinuously.

FIG. 3 shows a sample 21 of this embodiment, and FIG.
5 is a graph showing a result of measuring a light emission phenomenon by the measuring device shown in FIG. In this graph, the horizontal axis is the applied voltage (unit: kV). The vertical axis indicates light intensity, and indicates a value obtained by integrating the count value of the number of voltage pulses in the photo counting system every 10 seconds of the gate time. The material of the block 1 was a crosslinked polyethylene.
As shown in this graph, light emission was not observed when the applied voltage was 5 kV or less, but it was recognized that light emission occurred when the applied voltage was 5.5 kV or more.

According to this embodiment, since the water needle electrode 5a is formed in the block 1 made of an insulating material, a water tree is formed in the insulating material, and water is formed in the water tree. It can be regarded as being filled.
Therefore, by applying an electric field between the water needle electrode 5a of the sample 21 and the flat electrode 2 opposed thereto, it is possible to reproduce a state in which the water tree generated in the insulating material grows by applying the electric field. Is possible. Therefore, by measuring the light emission phenomenon in the sample 21 of the present embodiment, the light emission phenomenon during the growth of the water tree can be investigated. When manufacturing the sample 21, after removing the metal needle under vacuum from the block 1 in which the tip of the metal needle has been inserted in advance, the block 1 is placed in an atmospheric pressure atmosphere with the insertion port of the metal needle submerged. By shifting, the water needle electrode 5a can be preferably formed in the block 1. If the water needle electrode 5a is formed by such a method, a water needle electrode 5a having a preferable shape can be obtained without trapping gas at the tip of the water needle electrode 5a and forming a void or the like. Although the needle-shaped space 5 is filled with water here, other liquids can be filled instead of water, and the present invention can be applied to measurement of a light emission phenomenon related to factors other than the water tree. It is possible.

[0015]

As described above, the sample for luminescence measurement of the present invention is provided with two electrodes which are opposed to each other with an insulating material interposed therebetween, and one of the electrodes is formed as a needle-shaped electrode formed in the insulating material. By forming a water needle electrode formed by filling the space with water, a water tree can be formed in the insulating material, and a state in which the water tree is filled with water can be simulated. Therefore, by applying an electric field to the two electrodes in the sample and measuring the light emission phenomenon in the sample,
It is possible to investigate the light emission phenomenon during water tree growth.
Further, by performing the measurement of the light emission phenomenon in the atmosphere of the atmospheric pressure, it is possible to prevent the water constituting the water needle electrode from flowing out of the block, and to perform an appropriate measurement. Also,
By removing the metal needle under vacuum from the insulating material in which the tip of the metal needle has been inserted in advance, by moving the insulating material into an atmospheric pressure atmosphere with the insertion port of the metal needle submerged. A water needle electrode having a preferable shape can be formed without a void at the tip. As described above, according to the present invention, it is possible to obtain a sample having a state in which water trees are generated in an insulating material, and the method of the present invention for measuring a light emission phenomenon by applying an electric field to such a sample is as follows: It is very effective as a research tool for water tree degradation of insulating materials.

[Brief description of the drawings]

1A and 1B show a luminescence measurement sample according to the present invention, wherein FIG. 1A is a perspective view and FIG. 1B is a sectional view of a main part.

FIG. 2 is a schematic diagram of a measuring device used for measuring a sample according to the present invention.

FIG. 3 is a graph showing a measurement result of a light emission phenomenon according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Block (insulating material), 2 ... Plate electrode, 5 ... Needle space, 5a ... Water needle electrode, 21 ... Sample (sample) for luminescence measurement.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Jun Suzuki 1-5-1, Kiba, Koto-ku, Tokyo F-term in Fujikura Co., Ltd. 2G015 AA05 BA03 CA02 CA20

Claims (3)

[Claims] 1. A luminescence measurement sample having two electrodes arranged to face each other with an insulating material interposed therebetween, wherein one of the electrodes is
A sample for luminescence measurement, being a water needle electrode formed by filling water into a needle-like space formed in the insulating material. 2. The method according to claim 1, further comprising removing the metal needle from the insulating material into which the tip of the metal needle is inserted under vacuum, and then placing the insulating material in an atmospheric pressure atmosphere with the insertion opening of the metal needle submerged. Forming a water needle electrode formed by filling water into a needle-like space in the insulating material. 3. The sample for luminescence measurement according to claim 1,
A method for measuring luminescence, wherein an electric field is applied between the two electrodes in an atmospheric pressure atmosphere.