JPH0815364A - Gas insulatd electric apparatus - Google Patents

Abstract

PURPOSE:To detect an electromagnetic wave being generated when an apparatus is abnormal accurately without disturbing the internal field of the apparatus and with no influence of external noise. CONSTITUTION:A high voltage conductor 2 is arranged in a cylindrical grounded metal enclosure 1 and sealed with an insulating gas 5. A receiving ring antenna 12 of an abnormality detector 11 is fixed integrally to the inner face of an antenna flange 14 through an insulating cover 13 and inserted between a coupling flange 1a at an end in the axial direction of the enclosure 1 and an insulating spacer 4. The receiving ring antenna 12 and the coupling flange 14 have a diameter substantially equal to that of the enclosure 1 and arranged coaxially with the enclosure 1. The antenna ring 12 is coupled with a detector amplifier 9 through a coaxial connector 15 fixed to the antenna coupling flange 14 and an external coaxial cable 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage gas-insulated electric device, and more particularly to a gas-insulated electric device equipped with an abnormality detecting device for detecting an electromagnetic wave generated in a metal container.

[0002]

2. Description of the Related Art In recent years, as a switchgear for a high-voltage circuit used in a substation, a gas-insulated switchgear in which a high-voltage conductor and a switchgear are housed in a grounded metal container and an insulating gas is sealed in the container. The device is being used. Here, as the insulating gas sealed in the grounded metal container, SF ₆ gas having high stability, inertness, incombustibility, odorless, and harmless, and having a dielectric strength 2-3 times that of air is used. Gas is used.

In a high-voltage gas-insulated electric device such as such a gas-insulated switchgear, when there is an abnormality such as a protrusion inside the device, a contact failure, or the presence of a conductive foreign substance,
Partial discharge occurs and electromagnetic waves and high frequencies are generated. This phenomenon is a well known fact. If such partial discharge continues to occur for a long time, the deterioration of the device may progress to cause a ground fault or a dielectric breakdown accident. Therefore, in order to maintain the reliability of the high-voltage gas-insulated electric equipment, it is important to detect such partial discharge at an early stage and take measures against the abnormal portion. Conventionally, various devices have been developed as abnormality detection devices for such gas-insulated electrical equipment.

FIG. 5 shows a gas-insulated switchgear as an example of a high-voltage gas-insulated electrical equipment equipped with such an abnormality detection device. In FIG. 5, reference numeral 1 is a grounding metal container, and in this grounding metal container 1, a high-voltage conductor 2 for energization and an opening / closing part 3 are arranged and are held in an insulating state by an insulating spacer 4. An insulating gas 5 such as SF ₆ gas is enclosed in the grounded metal container 1, and a bushing 6 is used for connection with an external device. Then, the receiving antenna 7 is provided at a position near the outside of the gas insulated switchgear having such a configuration.
And an anomaly detection device 10 including a detection amplifier 9 connected to the receiving antenna 7 via a coaxial cable 8.

When a partial discharge occurs at an abnormal place inside the gas insulated switchgear and an electromagnetic wave is generated, a part of this electromagnetic wave leaks to the outside through the inside of the insulating spacer 4 and the bushing 6. Then, the abnormality detection device 10
Detects the electromagnetic wave leaked to the outside of the gas-insulated switchgear by the receiving antenna 7 in this manner, and the subsequent detection amplifier 9
The signal is taken out by and the presence or absence of abnormality is judged from this detection signal.

[0006]

By the way, in the conventional gas-insulated electric equipment as shown in FIG. 5, the receiving antenna 8 is installed outside the equipment. However, the intensity of the electromagnetic wave is considerably reduced when it passes through an insulator such as the insulating spacer 4 or when the distance from the generation site to the detection site is long. For this reason, the electromagnetic waves generated during internal abnormalities of the target high-voltage equipment may become weak signals compared to external noise.In this case, electromagnetic waves caused by internal abnormalities and external noise May be difficult to identify and the abnormal part may not be detected.

In addition, as a method of solving such a problem, it may be considered to incorporate the receiving antenna 7 into the grounded metal container 1 of the high-voltage equipment. However, when this method is adopted, the receiving antenna 8 may disturb the internal electric field in the grounded metal container 1 and act similarly to a conductive foreign substance, and thus the reliability of the high-voltage equipment is high. It creates new problems in terms of sex.

The present invention has been proposed in order to solve the above problems of the prior art, and its purpose is to:
Electromagnetic waves generated when the device is abnormal, without disturbing the internal electric field of the device and without being affected by external noise,
It is an object of the present invention to provide highly reliable and practical gas-insulated electrical equipment that can be detected with high accuracy, has a simple configuration, and is easy to install.

[0009]

In order to achieve the above object, the present invention provides a gas-insulated electric machine which is configured by arranging a conductor for energization in a cylindrical metal container containing an insulating medium. In the equipment, the arrangement of receiving antennas is characterized.

First, the invention according to claim 1 provides a ring-shaped receiving antenna, which has an inner diameter substantially the same as the inner diameter of the metal container and detects an electromagnetic wave generated in the metal container. It is characterized in that it is arranged coaxially and comprises signal transmission means for transmitting the detection signal from the receiving antenna to the outside of the metal container, and signal processing means for processing the detection signal received via the signal transmission means. There is. The invention according to claim 2 is characterized in that, in the invention according to claim 1, the receiving antenna is configured as follows. That is, in the invention according to claim 2, the receiving antenna is arranged at the end portion in the axial direction of the metal container.

Next, a third aspect of the present invention provides a branch space portion projecting to the outside on a circumferential side surface of the metal container, and a receiving antenna for detecting an electromagnetic wave generated in the metal container in the branch space portion. It is characterized in that it is provided with a signal transmission means for accommodating and transmitting the detection signal from the receiving antenna to the outside of the metal container, and a signal processing means for processing the detection signal received via the signal transmission means.

Further, the invention according to claims 4 and 5 is characterized in that, in the invention according to claim 3, the receiving antenna is constructed as follows. That is, in the invention described in claim 4, the receiving antenna is a planar antenna arranged substantially flush with the inner peripheral surface of the metal container. In the invention of claim 5,
The receiving antenna is characterized in that it has a coil-like shape so that its inner end face is substantially aligned with the inner peripheral face of the metal container.

On the other hand, the invention according to claim 6 is the invention according to claim 3, wherein a waveguide filter for selectively passing electromagnetic waves in a high frequency band is arranged on the branch point side in the branch space portion, and the waveguide filter is arranged. It is characterized in that the receiving antenna is arranged on the tip side of the wave filter. The invention according to claim 7 is characterized in that, in the invention according to claim 6, the waveguide filter is further configured as follows. That is, in the invention according to claim 7,
The waveguide filter is arranged so that the inner end surface thereof substantially coincides with the inner peripheral surface of the metal container.

[0014]

In the present invention having the above structure,
Since the receiving antenna is placed in the metal container, the electromagnetic waves generated in the metal container when the device malfunctions propagates in the metal container and does not pass through the insulating material such as the insulating spacer. Will be received by.
Therefore, the receiving antenna can efficiently and highly accurately receive this electromagnetic wave without being greatly attenuated and without being disturbed by external noise.

According to the first aspect of the invention, since the ring-shaped receiving antenna having an inner diameter substantially equal to the inner diameter of the metal container is arranged in the metal container, the electric field of the electric field in the metal container is reduced. No disturbance will occur.

According to the second aspect of the invention, since the ring-shaped receiving antenna is arranged at the end of the metal container in the axial direction, the receiving antenna is arranged at the end of the metal container. It will be arranged in the vicinity of the insulating spacer.
Therefore, since the receiving antenna can be arranged in the vicinity of the insulating spacer, it is possible to accurately perform the insulation diagnosis of the insulating spacer having a weak point in the insulation especially to the conductive foreign matter. Further, since the receiving antenna can be arranged in the vicinity of the insulating spacer in this way, the insulating coating provided on the receiving antenna can be made sufficiently thin, and electromagnetic waves generated in the metal container are hardly attenuated by the receiving antenna. Can be received efficiently and with high accuracy.

According to the third aspect of the invention, since the receiving antenna is housed in the branch space provided in the metal container, the electric field is not disturbed in the metal container. Moreover, the electromagnetic wave generated in the metal container can be directly received efficiently and highly accurately without being attenuated by the receiving antenna housed in the branch space in this way.

Further, according to the inventions of claims 4 and 5, a flat receiving antenna is used which matches the inner peripheral surface of the metal container, or the end face of the coil-like receiving antenna is placed inside the metal container. By adjusting to the peripheral surface, it is possible to more surely prevent the disturbance of the electric field in the metal container. On the other hand, according to the invention of claim 6, since the electromagnetic wave in a high frequency band can be selected by the waveguide filter, the electromagnetic wave thus selected can be received more efficiently and highly accurately by the receiving antenna. You can Also,
According to the invention of claim 7, by aligning the end surface of the waveguide filter with the inner peripheral surface of the metal container, it is possible to more reliably prevent the disturbance of the electric field in the metal container.

[0019]

EXAMPLES Examples of gas-insulated electrical equipment according to the present invention will be specifically described below with reference to FIGS.
Note that the same parts as those of the conventional example shown in FIG.

[1] First Embodiment FIG. 1 FIG. 1 is a diagram showing an embodiment of a gas-insulated electric equipment to which the inventions of claims 1 and 2 are applied. As shown in FIG. 1, a high-voltage conductor 2 and an opening / closing part 3 (not shown) are arranged in a horizontally arranged cylindrical grounded metal container 1, and an insulating gas 5 such as SF ₆ is sealed therein. ing. Then, in this grounded metal container 1, the ring-shaped receiving antenna 12 of the abnormality detecting device 11 of the present embodiment is arranged.

That is, as shown in FIG. 1, the ring-shaped receiving antenna 12 of the abnormality detecting apparatus 11 of this embodiment is integrally formed on the inner surface of the antenna connecting flange 14 via the insulating coating 13 provided around the ring-shaped receiving antenna 12. It is installed. And this antenna connection flange 14 is the ground metal container 1
It is inserted between the connection flange 1a provided at the axial end of the and the insulating spacer 4, and is fixed in an airtight state. In this case, the antenna connection flange 14 including the ring-shaped receiving antenna 12 is configured to have an inner diameter that is substantially the same as the inner diameter of the grounded metal container 1, and the inner peripheral surface thereof is the inner peripheral surface of the grounded metal container 1. Is arranged coaxially with the grounded metal container 1 so as to be continuous on substantially the same plane. Further, the ring-shaped receiving antenna ring 12 is connected to the detection amplifier 9 via the coaxial connector 15 attached to the antenna connection flange 14 and the external coaxial cable 8. In this case, the coaxial connector 15 and the coaxial cable 8 correspond to the signal transmission means of the present invention, and the detection amplifier 9
Corresponds to signal processing means.

The operation of the gas-insulated electric equipment of this embodiment constructed as described above is as follows. That is, when an electromagnetic wave is generated in the grounded metal container 1 when the device is abnormal, the electromagnetic wave propagates in the grounded metal container 1 and does not pass through an insulator such as the insulating spacer 4 and passes through a short distance and the insulating coating is applied. The signal is received by the ring-shaped receiving antenna 12 via 13. Therefore, the ring-shaped reception antenna 12 of the abnormality detection device 11 of the present embodiment does not greatly attenuate the electromagnetic wave propagating in the grounded metal container 1 in this way,
In addition, it is possible to efficiently and accurately receive without being disturbed by external noise.

Further, the insulating spacer 4 has a weak point that its insulating property is deteriorated with respect to a conductive foreign substance, but in the present embodiment, the ring-shaped receiving antenna 12 is arranged in the vicinity of this insulating spacer 4. Therefore, the insulation diagnosis of the insulation spacer 4 can be performed with high accuracy. Further, since the ring-shaped receiving antenna 12 is arranged in the vicinity of the insulating spacer 4 as described above, the insulating coating 13 of the ring-shaped receiving antenna 12 can be made as thin as possible. It is possible to efficiently and highly accurately receive the generated electromagnetic waves with little attenuation. Therefore, it is possible to perform highly reliable abnormality detection.

On the other hand, in this embodiment, since the ring-shaped receiving antenna 12 is arranged at the end of the grounded metal container 1, no disturbance of the electric field occurs inside the grounded metal container 1. Therefore, the reliability of the high-voltage equipment can be improved. Further, again, the abnormality detection device 11 of this embodiment using such a ring-shaped receiving antenna 12
As is apparent from FIG. 1, the structure is simple in structure and configuration and can be easily applied to existing high-voltage equipment, and is therefore highly practical.

[2] Second Embodiment ... FIG. 2 FIG. 2 is a diagram showing an embodiment of a gas-insulated electric apparatus to which the inventions of claims 3 and 4 are applied. As shown in FIG. 2, in this embodiment, a cylindrical branch space portion 1b projecting downward is provided on the bottom surface near the end of the horizontally arranged cylindrical ground metal container 1. Then, the mesh plane receiving antenna 22 of the abnormality detecting device 21 of the present embodiment is housed in the branch space portion 1b. In this case, the mesh plane portion 22a of the mesh plane receiving antenna 22 is arranged on substantially the same plane as the bottom surface of the grounded metal container 1. The size of the mesh plane portion 22a of the mesh plane receiving antenna 22 is determined by the branch space portion 1b.
It is smaller than the inner diameter of
2a is arrange | positioned coaxially so that it may not contact the branch space part 1b. Further, the mesh planar receiving antenna 22 is connected to the detection amplifier 9 via the coaxial connector 15 and the external coaxial cable 8.

The operation of the gas-insulated electric equipment of this embodiment constructed as described above is as follows. That is, when an electromagnetic wave is generated in the grounded metal container 1 when the device is abnormal, this electromagnetic wave propagates in the grounded metal container 1 and passes through a short distance without passing through an insulator such as the insulating spacer 4 and the mesh plane. It is directly received by the antenna 22. Therefore, the mesh planar receiving antenna 22 of the anomaly detection device 21 of the present embodiment efficiently and efficiently attenuates the electromagnetic waves propagating in the grounded metal container 1 without being disturbed by external noise. It can be received directly with high accuracy. In particular, in the present embodiment, since the mesh planar receiving antenna 22 is used, it is possible to directly receive the electromagnetic wave with high accuracy and with almost no attenuation, so that highly reliable abnormality detection can be performed. it can. Further, in this embodiment, since the mesh planar receiving antenna 22 is arranged in the vicinity of the insulating spacer 4 having a weak point in insulation against a conductive foreign substance,
Similar to the embodiment, the insulation diagnosis of the insulation spacer 4 can be performed with high accuracy.

On the other hand, in this embodiment, the mesh plane receiving antenna 22 is housed in the branch space portion 1b provided in the grounded metal container 1, and more particularly, the mesh plane portion 22a of the mesh plane receiving antenna 22 is provided. Is disposed substantially on the same plane as the bottom surface of the grounded metal container 1, it is possible to reliably prevent the occurrence of disturbance of the electric field inside the grounded metal container 1. Therefore, the reliability of the high-voltage equipment can be improved. Further, in this embodiment, an extremely low electric field region is formed in the branch space portion 1b having the above-mentioned configuration. Therefore, when a conductive foreign substance exists in the grounded metal container 1, the conductive foreign substance causes the mesh flat portion 22b of the mesh planar receiving antenna 22.
Passing through the branch space portion 1b which is an extremely low electric field region
Trapped inside. And in this way the branch space part 1
Since the conductive foreign matter once trapped in b is electrically held in the branch space portion 1b and cannot be re-floated,
Practically disabled. That is, in this embodiment,
By combining the branch space portion 1b and the mesh planar receiving antenna 22, it is possible to remove conductive foreign matter and further improve the reliability of the high-voltage equipment. Further, as is apparent from FIG. 2, the abnormality detection device 21 of the present embodiment using such a mesh plane receiving antenna 22 is excellent in practicality because its structure and configuration are simple.

[3] Third Embodiment FIG. 3 FIG. 3 is a diagram showing an embodiment of a gas-insulated electric apparatus to which the inventions of claims 3 and 5 are applied. As shown in FIG. 3, in this embodiment, the bottom surface of the horizontally arranged cylindrical ground metal container 1 in the vicinity of the end portion thereof has a cylindrical shape protruding downward as in the second embodiment. Branch space 1b
Is provided. Then, in the branch space portion 1b, the coil-shaped receiving antenna 32 of the abnormality detecting device 31 of the present embodiment.
Are stored coaxially. In this case, the upper end surface of the coil-shaped receiving antenna 32 is arranged so as to substantially coincide with the bottom surface of the grounded metal container 1. The length of the coil-shaped receiving antenna 32 is set according to the frequency band to be detected. Further, the coiled reception antenna 32 is connected to the detection amplifier 9 via the coaxial connector 15 and the external coaxial cable 8.

The operation of the gas-insulated electric equipment of this embodiment constructed as described above is as follows. That is, when an electromagnetic wave is generated in the grounded metal container 1 when the device is abnormal, the electromagnetic wave propagates in the grounded metal container 1 and does not pass through an insulator such as the insulating spacer 4 and passes through a short distance to form a coil shape. It is directly received by the receiving antenna 32. Therefore, the coil-shaped receiving antenna 32 of the abnormality detection device 31 of the present embodiment, the electromagnetic wave propagating in the grounded metal container 1,
It is possible to directly receive the signal efficiently and with high accuracy without greatly attenuating it and without being disturbed by external noise. In particular, in the present embodiment, since the coil-shaped receiving antenna 32 is used, electromagnetic waves can be directly received with high accuracy and almost no attenuation, so that highly reliable abnormality detection can be performed. . Also,
Since the coiled receiving antenna 32 can also support a relatively low frequency band, it can detect electromagnetic waves in a wider frequency band.

Further, in this embodiment, the coil-shaped receiving antenna 32 is arranged in the vicinity of the insulating spacer 4 which has a weak point in the insulation against the conductive foreign matter. Similarly, the insulation diagnosis of the insulation spacer 4 can be performed with high accuracy. Further, in this embodiment, the coiled reception antenna 32 is housed in the branch space 1b provided in the grounded metal container 1, and in particular, the upper end surface of the coiled reception antenna 32 is the bottom surface of the grounded metal container 1. Ground metal container 1 because it is placed so that it almost coincides with
It is possible to reliably prevent the occurrence of disturbance of the electric field inside. Therefore, the reliability of the high-voltage equipment can be improved. Further, by combining the branch space portion 1b and the coil-shaped receiving antenna 32 as described above, the second
Similar to the embodiment, since the conductive foreign matter can be removed by the branch space portion 1b, the reliability of the high voltage device can be further improved.

[4] Fourth Embodiment ... FIG. 4 FIG. 4 is a view showing an embodiment of a gas-insulated electric apparatus to which the invention described in claims 3, 6, and 7 is applied. As shown in FIG. 4, in this embodiment, the bottom surface near the end of the horizontally arranged cylindrical grounded metal container 1 projects downward as in the second and third embodiments. A cylindrical branch space portion 1b is provided. The waveguide filter 42 of the abnormality detection device 41 of the present embodiment is arranged above the branch space portion 1b on the branch point side. This waveguide filter 42 has a function of selectively passing an electromagnetic wave in a high frequency band, and its upper end surface is arranged substantially flush with the bottom surface of the grounded metal container 1. That is, the waveguide filter 42 includes a flat plate 43 arranged to cover the opening surface of the branch space portion 1b, a single or plural holes 43a provided in the flat plate 43, and the hole 43a.
And the same number of waveguides 44 mounted below. In the figure, a state in which a plurality of waveguides 44 are attached is shown. Further, a planar receiving antenna 45 is arranged below the waveguide 44, and the planar receiving antenna 45 is connected to the detection amplifier 9 via the coaxial connector 15 and the external coaxial cable 8.

The operation of the gas-insulated electric equipment of this embodiment constructed as described above is as follows. That is, when an electromagnetic wave is generated in the grounded metal container 1 when the device is abnormal, the electromagnetic wave propagates in the grounded metal container 1 and is guided through a short distance without passing through an insulator such as the insulating spacer 4. The waveguide filter 42 reaches the tube filter 42, and electromagnetic waves in a high frequency band are selected by the waveguide filter 42. Then, the selected electromagnetic wave is received by the planar receiving antenna 45. Therefore, the abnormality detection device 4 of the present embodiment
1, the electromagnetic wave propagating in the grounded metal container 1 can be received without being greatly attenuated and without being disturbed by external noise, and the electromagnetic wave selected by the waveguide filter 42 is received in a planar manner. The antenna 45 enables more efficient direct reception with high accuracy.
Therefore, the sensitivity is higher than that when only the planar receiving antenna 45 is used, and more reliable abnormality detection can be performed.

Further, in this embodiment, since the planar receiving antenna 45 is arranged in the vicinity of the insulating spacer 4, the insulation diagnosis of the insulating spacer 4 can be performed with high accuracy as in the first to third embodiments. It can be carried out. Further, in this embodiment, the branch space portion 1b provided in the grounded metal container 1 is also provided.
The waveguide filter 42 is housed in the
Since the upper end surface of 2 is arranged on substantially the same plane as the bottom surface of the grounded metal container 1, it is possible to reliably prevent the occurrence of the disturbance of the electric field inside the grounded metal container 1. Therefore, the reliability of the high-voltage equipment can be improved. Furthermore, by combining the branch space portion 1b and the waveguide filter 42 as described above, conductive foreign matter can be removed by the branch space portion 1b, as in the second and third embodiments, so that the reliability of high-voltage equipment is improved. Can be further improved.

[5] Other Embodiments The present invention is not limited to the above embodiments, and various other modified examples can be implemented.
First, in each of the above-described embodiments, a single-phase high-voltage device is illustrated, but the present invention is similarly applicable to a three-phase high-voltage device. For example, the ring-shaped receiving antenna can be provided not only in the vicinity of the insulating spacer for single phase as in the first embodiment, but also in the vicinity of the insulating spacer for three phases. The same effect as that of the first embodiment can be obtained.

Further, in the second embodiment, the case where the mesh plane receiving antenna is used is shown, but the same effect can be obtained when the helical plane receiving antenna is used. Furthermore, in the fourth embodiment, the case where a plurality of waveguides are used alone has been shown, but the same applies when a plurality of waveguides of the same shape are bundled to form a honeycomb waveguide. The effect of is obtained.

[0036]

As described above, according to the present invention,
By arranging the receiving antenna inside the metal container, the electromagnetic waves generated when the internal abnormality of the device is disturbed without disturbing the internal electric field of the device, and without being affected by external noise,
It is possible to provide a highly reliable and highly practical gas-insulated electrical device that can be detected with high accuracy, has a simple configuration, and is easy to install.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a gas-insulated electric device according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the gas insulated electric device according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the gas-insulated electric device according to the present invention.

FIG. 4 is a sectional view showing a fourth embodiment of the gas-insulated electric device according to the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional gas-insulated switchgear.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ground metal container 1a ... Connection flange 1b ... Branch space part 2 ... High voltage conductor 3 ... Opening / closing part 4 ... Insulating spacer 5 ... Insulating gas 6 ... Bushing 7 ... Receiving antenna 8 ... Coaxial cable 9 ... Detection amplifier 10, 11, 21, 31, 41 ... Abnormality detection device 12 ... Ring-shaped receiving antenna 13 ... Insulation coating 14 ... Antenna connecting flange 15 ... Coaxial connector 22 ... Mesh plane receiving antenna 22a ... Mesh plane part 32 ... Coil receiving antenna 42 ... Waveguide Tube filter 43 ... Flat plate 43a ... Hole 44 ... Waveguide 45 ... Planar receiving antenna

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01Q 7/00

Claims (7)

[Claims] 1. A gas-insulated electric device comprising a conductive metal conductor arranged in a cylindrical metal container containing an insulating medium, wherein the metal container has substantially the same inner diameter as the inner diameter of the metal container. A signal transmitting means having an inner diameter of a diameter, coaxially arranging a ring-shaped receiving antenna for detecting an electromagnetic wave generated in the metal container, and transmitting a detection signal from the receiving antenna to the outside of the metal container, A gas-insulated electric device comprising: a signal processing unit that processes a detection signal received through the signal transmission unit. 2. The gas insulated electric device according to claim 1, wherein the reception antenna is arranged at an end portion of the metal container in the axial direction. 3. A gas-insulated electric device comprising an electrically conductive conductor arranged in a cylindrical metal container enclosing an insulative medium, and a branch projecting to the outside on a circumferential side surface of the metal container. A space is provided, a reception antenna for detecting an electromagnetic wave generated in the metal container is housed in the branch space, and a signal transmission means for transmitting a detection signal from the reception antenna to the outside of the metal container, and the signal transmission means. And a signal processing means for processing a detection signal received via the gas-insulated electric device. 4. The gas-insulated electric device according to claim 3, wherein the receiving antenna is a flat-shaped one that is arranged substantially flush with the inner peripheral surface of the metal container. 5. The gas-insulated electric device according to claim 3, wherein the receiving antenna is a coil-shaped antenna arranged so that an inner end surface thereof substantially coincides with an inner peripheral surface of the metal container. . 6. A waveguide filter for selectively passing an electromagnetic wave in a high frequency band is arranged on a branch point side in the branch space portion, and the receiving antenna is arranged on a tip side of the waveguide filter. The gas-insulated electric device according to claim 3. 7. The gas-insulated electric device according to claim 6, wherein the waveguide filter is arranged such that an inner end surface thereof substantially coincides with an inner peripheral surface of the metal container.