JP2005241623A - Discharge detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge detector capable of further accurately detecting corona discharge with a further simple structure. <P>SOLUTION: UV-C ultraviolet ray images from an object 10 are acquired while alternately performing irradiation and interruption of ultraviolet ray to the object. Even in the daytime, presence of corona discharge and the position of corona discharge in the object can be specified by the two kinds of alternately acquired images. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge detection device for detecting the occurrence of corona discharge in an object capable of generating corona discharge, such as electrical equipment such as a power transmission tower.

In electrical equipment, a minute corona discharge may occur as electrical insulation deteriorates. That is, by detecting corona discharge, electrical insulation deterioration can be detected at an early stage.
As an apparatus for detecting this corona discharge, for example, there is a detection apparatus described in Patent Document 1. In this detection apparatus, ultrasonic sound when corona discharge occurs is detected, and the presence and position of corona discharge is detected by specifying the direction of sound generation based on the detection.
JP-A-9-233679

However, in the detection method using sound at the time of discharging, it is necessary to move the acoustic detection unit so as to scan the inspection target, so that the larger the target, the longer the inspection takes.
Further, since the magnetostrictive vibration sound or the like approximates the discharge sound, it may be erroneously detected that the corona discharge is detected even though there is no corona discharge.
The present invention has been made paying attention to the above points, and an object of the present invention is to provide a discharge detection device that can detect corona discharge more accurately and with a simpler configuration.

  In order to solve the above problems, the invention described in claim 1 of the present invention is a discharge detection device for detecting corona discharge from a target capable of generating corona discharge, and irradiates the target with ultraviolet rays. Ultraviolet irradiation means, a shutter capable of blocking irradiation to the object from the ultraviolet irradiation means, an optical filter that allows passage of only ultraviolet rays in the UV-C region of light rays from the object, and ultraviolet light after passing through the optical filter A visualization conversion unit that visualizes an image; and an image acquisition unit that acquires an ultraviolet image visualized by the visualization conversion unit, and the image acquisition unit acquires both images of an ultraviolet blocking state and an irradiation state by the shutter. Thus, the presence / absence and position of corona discharge in the object is specified.

According to a second aspect of the present invention, in the configuration described in the first aspect, the shutter is repeatedly opened and closed in predetermined time units, and the image acquisition unit is a camera that continuously captures images. It is characterized by that.
Next, according to a third aspect of the present invention, in the discharge detection apparatus according to the first or second aspect, the optical filter has one or more Ne (neon) emission lines existing in a wavelength range of 240 nm to 280 nm. It is characterized by being a narrow-band pass filter that passes through.

According to the present invention, with the same image acquisition means, the corona discharge-only image and the target image with the optical path being coaxial are alternately acquired, and the corona discharge is compared by comparing the two types of images acquired alternately. It becomes possible to specify the presence or absence and position.
Moreover, since it is an image, it is possible to inspect a wide area at a time.
Furthermore, by acquiring ultraviolet images in the UV-C region that do not exist in the sunlight that has been actively irradiated with ultraviolet rays and that has reached the ground, the presence or absence of corona discharge can be achieved with a simple configuration even during the daytime. The position can be detected.

Embodiments of the present invention will be described below with reference to the drawings.
First, the discharge phenomenon and ultraviolet rays will be described.
It is known that the discharge phenomenon involves emission of ultraviolet rays in addition to electromagnetic waves and ultrasonic waves. Discharge is caused by gas atoms in an excited state under the influence of an electric field emitting free electrons and being ionized. At this time, light is emitted in the process in which the ionized atom receives free electrons and returns from the excited state to the ground state.
Here, the wavelength of light emitted when the electron trajectory transitions from n = i to n = j is given by the following equation (1).

Where λ: wavelength of emitted light, m: kinetic mass of electron, e: charge of electron (1.602 × 10 ⁻¹⁹ C), ε ₀ : dielectric constant of vacuum (8.854 × 10 ⁻¹² F) / M), h: Planck's constant (6.624 × 10 ⁻³⁴ J · sec), c: speed of light (3 × 10 ⁸ m / sec)
Here, the inventor of the present application pays attention to the fact that the ionization voltage of each atom is given by the following equation (2), and the emission wavelength of the gas whose ionization voltage is known from the equations (1) and (2) is I thought that it can be obtained in (3).

  FIG. 1 shows an emission spectrum of a typical gas obtained by the equation (3). From the figure, it can be seen that the wavelength of light generated by the discharge is discretely distributed in the ultraviolet region of 400 nm or less. On the other hand, ultraviolet rays are classified into UV-A from 400 nm to 315 nm, UV-B from 315 nm to 280 nm, and UV-C from 280 nm to 100 nm depending on the wavelength.

  By the way, ultraviolet rays are short-wave electromagnetic waves having a wavelength of 400 nm or less, which are emitted from artificial lighting such as the sun and high-intensity lamps. In particular, in the case of solar radiation reaching the ground surface, the emission distribution shown in FIG. Thus, the shorter the wavelength, the smaller the occupation ratio in solar radiation. In particular, the electromagnetic wave in the UV-C region is absorbed by the ozone layer in the atmosphere, and therefore hardly reaches the ground surface. On the other hand, the light emission distribution by corona discharge is as shown in FIG. 2 and radiates over the entire ultraviolet region. Therefore, by detecting ultraviolet rays in the UV-C region that do not exist in the solar radiation that reaches the ground surface, it is not affected by solar radiation, and even weak discharge light is not affected by sunlight, such as corona discharge. Ultraviolet rays accompanying light emission from the subject itself due to the occurrence can be detected.

Next, the structure of the discharge detection device of this embodiment will be described. FIG. 3 is a schematic configuration diagram of the apparatus.
In the cylindrical case 1, the UV filter 2, the UV lens 3, the UV image intensifier 4, the UV lens 3, the UV image intensifier 4, and UV are arranged so that the optical path L is coaxial from the object 10 side. The lens 3 and the video camera 5 are arranged in this order.
Each of the UV image intensifiers 4 is a device for detecting and multiplying a weak ultraviolet image to convert it into a contrasted image, that is, a visualized image. In addition, since a normal CCD camera does not have sensitivity to ultraviolet rays, the discharge phenomenon cannot be imaged.

Each UV image intensifier 4 doubles photoelectrons by processing countless thin holes (channels) of φ12μm on a light-receiving surface that converts received light into electrons and a thin glass plate with a diameter of 25mm and a thickness of 0.48mm. MCP (multi-channel plate) and a fiber plate that converts the doubled electrons into light again and transmits them to the subsequent stage. In the present embodiment, Ce-Te having sensitivity to ultraviolet rays is selected as the material for the light receiving surface of each UV image intensifier 4. The Ce-Te light-receiving surface is suppressed in sensitivity to light having a wavelength of 320 nm or more and has maximum sensitivity in the vicinity of 250 nm. And MCP made the electron multiplication rate 10 ⁶ times by considering the weak discharge light and making it two steps. Here, since each UV image intensifier 4 has a high amplification factor, even a small amount of light is imaged and obstructs discrimination of the discharge light that is originally desired to be observed. Therefore, a UV filter 2 that allows only UV-C light to pass through is installed in front of the UV image intensifier 4 to block unnecessary light.

  By the way, normally, the filter includes a band pass filter that passes a specific wavelength band and a narrow band pass filter that passes only a specific wavelength (see, for example, FIG. 1). A filter that passes only UV-C ultraviolet rays in the range of 280 nm is preferred. In particular, in the filter selection in this embodiment, as a result of laboratory tests using five types of narrow band pass filters, as shown in FIG. 4, the narrow band pass filter that passes 249.7 nm has the best S / N ratio. It was suitable for visualization of discharge. In the example of the figure, discharge is generated at the bottom center of the screen, but it can be seen that it is difficult to discriminate between the discharge light and the background sunlight with a filter other than 260BP and 249.7NB7.

Here, in the image that has passed through the 249.7NB7 filter shown in FIG. 4, Ne (neon) emission lines are mainly observed as can be seen with reference to FIG. Neon nitrogen (volume ratio 78.088% in air), oxygen (up 20.949%), argon volume ratio in the atmosphere subsequent to (the same 0.93%) larger gas (the 1.8 × 10 ^{- 3} %), and the volume ratio is the largest among gases having bright lines in the UV-C region. Therefore, it is preferable to discriminate the Ne (neon) emission line because the amount of emitted light is large. Further, in the present embodiment, a narrow band pass filter that passes one or more emission lines of 249.7 nm, that is, Ne (neon) among UV-C ultraviolet rays existing in a wavelength range of 240 to 280 nm is provided. It is adopted as the UV filter 2. Therefore, by adopting such a narrow band pass filter, the discrimination between the discharge light and the background sunlight can be made more reliable.

Here, each of the UV lenses 3 is a lens having sensitivity to ultraviolet rays (particularly, preferably UV-C is sensitive). The video camera 5 is a recording medium that constitutes an image acquisition unit and continuously acquires and records a visualized ultraviolet image that passes through the UV filter 2 and is visualized.
The plurality of UV lenses 3 and the UV image intensifier 4 constitute a visualization conversion unit. In view of the fact that UV-C ultraviolet radiation due to corona discharge is weak, in this embodiment, a case where a plurality of UV lenses 3 and UV image intensifiers 4 are arranged is illustrated.

  An ultraviolet lamp 6 is attached to the outside of the case 1. The ultraviolet lamp 6 is an ultraviolet irradiation means for irradiating the object 10 with ultraviolet rays. For example, a high-intensity lamp 6 such as a high-intensity UV lamp using quartz glass may be used. In particular, an ultraviolet lamp capable of mainly emitting ultraviolet rays having a wavelength in the UV-C region that can pass through the UV filter 2 is preferable. The irradiation direction of the ultraviolet lamp 6 can be adjusted with respect to the case 1.

An openable / closable shutter 7 is attached in front of the ultraviolet lamp 6, and the shutter 7 is opened and closed by a shutter actuator 8 made of a drive motor, an electromagnet or the like.
Reference numeral 9 denotes a controller, which turns on the ultraviolet lamp 6 when the operation switch (not shown) is turned on, and repeatedly opens and closes the shutter 7 at predetermined time intervals through the shutter actuator 8. . Although the opening / closing speed of the shutter 7 is not particularly limited, for example, the opening / closing speed is set to be repeated at intervals of 1 second.

Next, an example of usage and actions / effects in the discharge detection apparatus having the above configuration will be described.
The optical path L such as the UV filter 2 disposed in the case 1 is directed toward the target 10, and the radiation direction of the ultraviolet lamp 6 is also directed toward the same target 10, and an operation switch (not shown) is turned on. Then, ultraviolet rays are irradiated from the ultraviolet lamp 6 toward the object 10, but the irradiation of ultraviolet rays is periodically blocked by the shutter 7 that repeatedly opens and closes. In this state, the video camera 5 is also in the recording state. The video may be controlled by the controller 9 as well.

  By setting in this way, the reflected light from the object 10 by irradiating the ultraviolet rays and the light emitted from the object 10 by blocking the ultraviolet rays are incident on the UV filter 2 alternately. Then, only the reflected light from the object 10 by the ultraviolet lamp 6 and the ultraviolet light emitted from the object 10 pass through the UV filter 2 alternately, thereby removing the influence of sunlight reaching the ground surface.

  The two kinds of ultraviolet images that alternately pass through the UV filter 2 are doubled and emphasized by two sets of UV lens 3 and UV image intensifier 4, respectively, and converted into a visualization state. Captured and recorded. FIG. 5 shows an image diagram of the two types of ultraviolet images. (A) is the figure of the object by ultraviolet irradiation, (b) is the figure by the light emission of the object by corona discharge. Actually, in the figure of (b), only the corona discharge portion A is an white image.

  Then, when the recorded image is reproduced, in the state where there is no corona discharge, only a black image and a black and white image of the object 10 are displayed alternately. However, in the object 10 where the corona discharge occurs, the corona discharge The two types of images, that is, the ultraviolet image in which only the light emitting portion of white is white and the black-and-white image of the object 10 are alternately displayed. Thereby, the presence or absence of corona discharge is detected, and the position of the corona discharge in the object 10 is visually recognized by alternately displaying the ultraviolet image in which only the light emission part of the corona discharge is white and the entire image of the object 10. Can do. In particular, by adjusting the playback speed etc. and projecting two types of images alternately, if the afterimage of one image and the next projected image appear to overlap completely in appearance, corona discharge can be more easily performed. It becomes easy to specify the position. It should be noted that the adjustment of the appearance of the afterimage can be adjusted by adjusting the reproduction speed, for example, by extending the video display time of the ultraviolet image by light emission.

At this time, by acquiring the image of the object 10 as an ultraviolet image, the image of the object 10 itself is naturally suppressed to be dark. Therefore, when the image is alternately displayed with the whitened image by the light emission of the corona discharge, the light emission is caused. The white parts are emphasized naturally.
Here, without actively irradiating from the ultraviolet lamp 6, an image of light emission by corona discharge is acquired by the apparatus, and an image of the object 10 is taken with another camera in synchronization, It is also conceivable to detect the discharge position by superimposing images. However, since not only another camera that captures the image of the object 10 is required, but also the position where the image is received is different, superposition processing is required.

  On the other hand, in the present application, only one camera is required, and both the image by discharge and the image of the target 10 are acquired at a position where the optical path L is coaxial, so that the apparatus configuration is simplified. Further, in the present embodiment, the two images are not directly overlapped by the image processing unit, but are alternately displayed, and the position of the corona discharge is specified by using, for example, a visual afterimage phenomenon. The process of overlapping is also unnecessary.

  Here, in the above-described embodiment, the images acquired alternately are reproduced so as to appear to overlap each other by the afterimage phenomenon, but the afterimage phenomenon does not necessarily have to be used. It may be played back slowly in a frame feed. Since the ultraviolet image by corona discharge can be easily identified, when the ultraviolet image by corona discharge is detected, the approximate position of the light emission is stored (see FIG. 5B) and the object to be projected next. The position of the corona discharge can be specified by looking at the corresponding position in the ten images (see FIG. 5A). However, it is easier to visually recognize the image after reproducing it so as to overlap using the afterimage phenomenon.

Moreover, although the video camera 5 is illustrated as the image acquisition unit, a digital camera or the like may be used. In the case of a digital camera, a still image is captured in synchronization with opening and closing of the shutter 7, and an ultraviolet image reflected by ultraviolet irradiation and an ultraviolet image emitted by corona discharge (a dark image if there is no light emission) May be obtained alternately.
In the above-described embodiment, a camera is exemplified as the image acquisition unit, and the case where the presence or absence of corona discharge is confirmed after shooting is described. However, the present invention is not limited to this. For example, the image acquisition means is a display device such as a display, and on the spot, an ultraviolet image by corona discharge and an ultraviolet image by reflection from the object 10 are alternately displayed, and the presence or absence of corona discharge and The discharge position may be specified when corona discharge is occurring.

Further, color conversion processing may be performed only on the ultraviolet image by corona discharge by image processing, that is, the white portion may be converted to red or the like to emphasize the corona discharge portion. In this case, since the ultraviolet image resulting from the reflection from the object 10 is a black and white image, the position of the corona discharge can be visually recognized more easily.
Further, the case 1 and the ultraviolet lamp may be separate.

In the example of the above embodiment, the UV filter 2 employs a narrow band pass filter that passes a bright line of 249.7 nm Ne (neon), but is not limited thereto, and the narrow band pass filter has a wavelength of You may observe by the narrow-band pass filter which passes the bright line of 1 or 2 or more Ne (neon) of another wavelength among UV-C ultraviolet rays which exists in the range of 240-280 nm.
As described above, in the discharge detection device of the present embodiment, it is possible to detect the discharge location even during the daytime, and the device configuration can be simplified.

Next, examples of the present invention will be described.
The discharge detection device of the above embodiment was brought into the open inspection of the generator, and partial discharge was photographed.
The generator in this example is a generator that has been operating for about 15 years, and since an increase in partial discharge has been observed in recent years, an open inspection was performed with the discharge detection device of the above embodiment. Prior to the inspection, a partial discharge test was conducted while monitoring with a discharge detector, and an attempt was made to identify the discharge site. As a result, the partial discharge that occurred at the coil end could be detected. Partial discharge was spot-generated near the slot exit at the coil end.

After completion of the partial discharge test, the occurrence site was inspected, and a gap of about 0.2 mm was generated between the coil and the slot. Therefore, repair was performed by inserting a conductive material into the gap generated in the slot and solidifying with resin, and in the partial discharge test conducted after the repair, no visible image of discharge was observed.
As described above, the discharge detection device of the present invention can be easily applied to a partial discharge test of, for example, a generator or an electric motor, so that the discharge site can be easily identified and whether or not the repair is successful can be easily confirmed. It was confirmed that can be done.

It is explanatory drawing which shows the emission spectrum of typical gas. It is a figure explaining light emission distribution. 1 is a schematic configuration diagram of a discharge detection device according to an embodiment of the present invention. It is a figure explaining the result of the laboratory test for filter selection. It is a figure explaining the image of two types of ultraviolet images.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 UV filter 3 UV lens 4 Image indentifier 5 Video camera 6 Ultraviolet lamp 7 Shutter 8 Actuator 9 Controller 10 Target L Optical path

Claims (3)

  A discharge detection device for detecting corona discharge from a target capable of generating corona discharge, an ultraviolet irradiation means for irradiating the target with ultraviolet light, and a shutter capable of blocking irradiation from the ultraviolet irradiation means to the target, An optical filter that passes only ultraviolet rays in the UV-C region among the light rays from the object, a visualization conversion unit that visualizes an ultraviolet image after passing through the optical filter, and an ultraviolet image visualized by the visualization conversion unit are acquired. A discharge detection device comprising: an image acquisition unit, wherein the image acquisition unit acquires images of both an ultraviolet blocking state and an irradiation state by the shutter to identify the presence and position of a corona discharge in the target. .   2. The discharge detection apparatus according to claim 1, wherein the shutter is repeatedly opened and closed in predetermined time units, and the image acquisition unit is a camera that continuously captures images.   3. The discharge detection device according to claim 1, wherein the optical filter is a narrow-band pass filter that passes one or more Ne (neon) emission lines existing in a wavelength range of 240 nm to 280 nm. .