JPH10322823A - Method and device for diagnosing insulation of electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To find out internal insulation abnormality in its early stage from the outside of an apparatus, by detecting the electromagnetic waves caused by partial discharge from an earth lead terminal connected to an earth device. SOLUTION: An opening of a container 1 is blocked with an insulating material 9 such as epoxy or the like, and a lead terminal 2 is passed through this insulating material 9, and an earth lead 12 is connected to the lead terminal 2, and the end of the earth lead 12 is earthed. Moreover, for a coaxial cable 3, a core 3a is connected to the lead terminal 2 and the shield cable 3 to an earth part 13 of the container 1. Then, external noise is detected together with the electromagnetic waves by the partial discharge within the container 1 by a rod antenna 10 made of the lead terminal 2, an earth wire 8', and an earth device 8, and a loop antenna 11 made of a shield wire 3b, the core 3a, and the earth lead 12, and the earth. As a result, the internal insulation abnormality can be found out in its early stage from outside the apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for diagnosing insulation of electric equipment having a grounding device such as a gas insulated switchgear (GIS) and a cubicle.

[0002]

2. Description of the Related Art For example, if there is a poor contact portion or a metallic foreign substance inside a GIS, an electric field concentrates there and a partial discharge occurs, which may lead to dielectric breakdown to ground fault or short circuit accident. It is important to detect such a situation before an accident occurs. Conventionally, in GIS, as shown in FIG.
A slot antenna 103 for partial discharge detection is mounted on an insulating spacer 102 sandwiched between flanges of a conduit 101 through which a bus conductor 100 passes, and connected to an insulation diagnostic device 105 via a coaxial cable 104.
6 was connected to the electromagnetic wave receiving device 105 by a coaxial cable.

In this conventional example, a slot antenna 10 in which an electromagnetic wave generated by a partial discharge inside a conduit 101 is attached to a bare insulating spacer 102 serving as an opening for the electromagnetic wave.
At 3, it is detected from outside the device, and received by the insulation diagnosis device 105. The noise detection antenna 106 is used to distinguish external noise detected simultaneously with the internal partial discharge by the slot antenna 103 from electromagnetic waves due to the internal partial discharge.

[0004]

However, since this conventional example is a system for detecting electromagnetic waves leaking from the insulating spacer, when the insulating spacer 102 is shielded by metal, the insulating spacer 102 is not opened with respect to the electromagnetic wave. In addition, it was impossible to detect electromagnetic waves due to internal partial discharge. Even when the insulating spacer 102 is not shielded by metal, attaching the slot antenna 103 to the insulating spacer 102 is dangerous because it involves work at a high place. Furthermore, slot antennas were expensive.

The present invention focuses on the fact that, in an electric device having a grounding device, the grounding device is released from the circuit except when the circuit is grounded, and utilizes this as an antenna for detecting partial discharge. Features. ADVANTAGE OF THE INVENTION According to this invention, without using a slot antenna like the conventional one, the external insulation diagnosis can be performed at a portion other than the insulating spacer, thereby reducing the cost for detecting the insulation abnormality and performing the insulation diagnosis of the electric device in consideration of the safety. Methods and apparatus can be provided.

[0006]

According to a first aspect of the present invention, there is provided a method for diagnosing electrical equipment insulation, comprising detecting an electromagnetic wave due to partial discharge from a ground wire lead-out terminal connected to the grounding apparatus in an electrical equipment having a grounding apparatus. Features. According to the method for diagnosing electrical equipment insulation according to the first aspect, since the grounding device is used as it is as the internal antenna, external insulation diagnosis of the electrical equipment can be performed regardless of the presence or absence of the insulating spacer. Further, a slot antenna is not required, and the ground wire lead-out terminal is provided at a relatively low place, so that a diagnosis operation is easy and safe.

According to a second aspect of the present invention, there is provided an insulation diagnostic apparatus for an electric device, comprising an earthing device, an earthing wire lead-out terminal connected to the grounding device, a coaxial cable and a ground lead connected to the lead-out terminal. It is a thing. Claim 2
According to the insulation diagnosis apparatus for an electric device, the same effect as that of the first aspect is obtained. According to a third aspect of the present invention, in the insulation diagnostic apparatus for an electric device, the ground lead connected to the ground line lead terminal is inserted through a ring-shaped ferrite core having a high impedance with respect to a high frequency.

According to the third aspect of the present invention, in addition to the effects of the second aspect, since the ferrite core eliminates the loop antenna portion and only the rod antenna portion, noise is not detected from the loop of the ground lead. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 to 5 taking a gas insulated switchgear (GIS) as an example. As shown in FIG. 1, although not shown, devices such as a circuit breaker, a disconnector, and a grounding device are housed inside the container 1 and are filled with an insulating gas. The ground wire lead-out terminal 2 is connected to a movable contact of a grounding device in the container 1 via a ground wire. During charging of the circuit, the movable contact is separated from the fixed contact. Conversely, when grounding the circuit, a ground lead may be connected to the lead terminal 2 and the grounding device may be turned on. Reference numeral 3 denotes a coaxial cable, one end of which is a ground wire lead-out terminal 2.
The other end is connected to the insulation diagnostic device 5. Further, a noise receiving antenna 4 for detecting external noise such as partial discharge of a transmission line or a broadcast wave is connected to an insulation diagnostic device 5 by a coaxial cable 6.
It is connected to the.

FIG. 2 shows a configuration of a portion serving as an antenna.
As shown in FIG. 2A, the portion serving as an antenna includes a ground wire 8 'of the grounding device 8, a ground wire lead-out terminal 2, and a coaxial cable 3
And a ground lead 12. The opening of the container 1 is closed with an insulating material 9 such as epoxy, the lead-out terminal 2 penetrates the insulating material 9, the ground lead 12 is connected to the lead-out terminal 2, and the end of the ground lead 12 is grounded. The coaxial cable 3 has its core wire 3a connected to the lead-out terminal 2 and its shield wire 3b connected to the ground portion 13 of the container 1.

FIG. 2 (b) shows an antenna circuit of a portion serving as the antenna of FIG. 2 (a).
A rod antenna unit 10 formed by the grounding device 8,
It comprises a shield wire 3b, a core wire 3a, a ground lead 12, and a loop antenna section 11 formed by grounding. Thus, external noise as well as electromagnetic waves due to partial discharge in the container 1 are detected.

FIG. 3 shows a schematic configuration of an example of an insulation diagnosis device. The insulation diagnostic device 5 is provided with a noise receiving antenna 4 near the object to be measured in order to distinguish between external noise and internal partial discharge, and is provided with a noise removing device 14 to be connected to a portion serving as an antenna for detecting partial discharge. The differential output between the input unit 7 and the noise receiving antenna 4 is obtained.

The noise removing device 14 includes tuners 15 and 16 connected to the input unit 7 and the noise receiving antenna 4 connected to a portion serving as an antenna for detecting partial discharge and tuning the same frequency. Amplifiers 17 and 18 whose gains are set so that the output of the noise receiving antenna 4 is increased while amplifying the output of the noise receiving antenna 4.
And differential amplifier 1 that creates the difference between the outputs of amplifiers 17 and 18
9 and a rectifier 20 for rectifying the output signal of the differential amplifier 19
Having.

Reference numeral 13 denotes a determination unit which determines the presence or absence of an abnormal electromagnetic wave from the output of the rectifier 20 and outputs an alarm signal when the abnormal electromagnetic wave is present to operate an alarm device or the like. 2
Reference numeral 1 denotes a pseudo reference signal source that generates an external noise 22. FIG. 4 is a waveform diagram when a pseudo external noise 22 is generated from the reference signal source 21 in a state where no abnormal electromagnetic wave is leaked. 5A shows the output waveform of the amplifier 17 on the internal partial discharge detection side, and FIG. 5B shows the output waveform of the amplifier 18 of the antenna 4 for noise reception. In this case, the amplifier 1
8, the signal level of the noise receiving antenna 4 becomes higher than the signal of the ground line lead-out terminal 2. When a signal representing the difference between the output signals of the amplifiers 17 and 18 is generated by the differential amplifier 19 as shown in FIG. FIG. 3D shows an output waveform after rectification by the rectifier 20, and there is no output because the signal of the difference between the external noises is on the negative side.

On the other hand, when a partial discharge occurs in the container 1, the electromagnetic wave is detected by the ground line lead-out terminal 2, so that the antenna circuit has an external noise component P and an abnormal electromagnetic component Q as shown in FIG. Since the noise receiving antenna 4 is not connected to the ground line lead terminal 2 and is separated from the ground line lead terminal 2 in terms of distance, FIG.
As shown in (a), the signal of the abnormal electromagnetic wave does not appear, and only the external noise P is output. The difference signal of the abnormal electromagnetic wave component Q appears on the positive side at the output of the differential amplifier 19, and the external noise component P
(C) of FIG. 2 appears on the negative side, but the negative side is rectified by the rectifier 12, so that a signal of the difference of the abnormal electromagnetic wave component Q is output as shown in FIG. 5 (b). .

According to this embodiment, it is possible to receive an electromagnetic wave due to internal partial discharge from the ground line lead-out terminal 2 in a state of circuit charging and to detect an internal insulation abnormality from outside the device at an early stage. Therefore, regardless of the presence or absence of the insulating spacer, the external insulation diagnosis of the gas insulated device can be performed. Further, since the ground wire lead-out terminal 2 is located relatively low, there is little danger in work.

Further, since the coaxial cable 3 is connected to the ground wire lead-out terminal 2 and the grounding device in the gas-insulated equipment is used as an internal antenna, a slot antenna is not required and the cost can be reduced. Also, the core wire 3a of the coaxial cable 3 is connected to the ground wire lead-out terminal 2, and the coaxial cable 3
Since the shield wire 3b is connected to the grounding portion 13 of the container 1, the loop antenna portion 11 formed by the loop of the grounded ground lead 12, the core wire 3a of the coaxial cable 3 and the grounded shielded wire 3b, Ground wire lead-out terminal 2
The rod antenna section 10 formed by the above is mixed, and the external noise is detected together with the internal partial discharge.

FIG. 6 shows a second embodiment of the present invention. That is, in the first embodiment, the ground lead 12 connected to the ground wire lead-out terminal 2 is connected to the ring-shaped ferrite core 23 having a high impedance with respect to a high frequency.
Is inserted. Reference numeral 24 denotes a stray capacitance between the core wire 3a of the coaxial cable 3 connected to the ground wire lead-out terminal 2 and the shield wire 3b.

According to this embodiment, the loop antenna section 11 is eliminated by the ferrite core 23, and only the rod antenna section 10 is provided. Therefore, external noise is not detected from the loop of the ground lead 12. Others are the same as in the first embodiment. FIG. 7 shows a third embodiment of the present invention.
Shown in That is, in the second embodiment, the container 1
And a conductive material 25 approaching the ground wire lead-out terminal 2 of the container 1. The shielded wire 3 b of the coaxial cable 3 is connected to the conductive material 25. The conductive material 25 has a hole 25 in the center.
a, the outer surface of the insulating material 9 is covered with the hole 25a through the ground wire lead-out terminal 2, and the peripheral portion is the container 1
Is installed electrically and mechanically. Shield wire 3b is hole 2
5a.

FIG. 2B shows the antenna circuit.
Reference numeral 6 denotes a stray capacitance between the core wire 3a and the shield wire 3b. According to this embodiment, since the shielded wire 3b of the coaxial cable 3 is connected to the conductive material 25 close to the ground wire lead-out terminal 2, the core wire 3a of the coaxial cable 3 and the shielded wire 3b are connected.
The influence of the stray capacitance 26 between the first and second electrodes b and b can be reduced, and the electromagnetic waves resulting from the internal partial discharge can be detected with high sensitivity.

The other points are the same as in the second embodiment.
Note that, as an example of the insulation diagnostic device 5, a method of obtaining the difference between the output of the electromagnetic wave due to the internal partial discharge and the output of the external noise has been described, but the present invention is not limited to this. For example, in an apparatus for diagnosing insulation of an electric device by detecting an electromagnetic wave generated by a partial discharge generated inside the electric device as already filed by the same applicant (Japanese Patent Application No. 7-333513). A plurality of data at a plurality of frequency points are obtained from a signal detected by the noise detection antenna, and based on low-level data among the plurality of data, low noise used to search for a noise-free frequency point. Of course, a method of automatically setting the level determination value may be used.

[0022]

According to the insulation diagnosing method and apparatus of the present invention, it is possible to receive an electromagnetic wave from the ground wire lead-out terminal by internal partial discharge and to detect an internal insulation abnormality from outside the device at an early stage. Therefore, regardless of the presence or absence of the insulating spacer, the external insulation diagnosis of the electric device can be performed. Further, since the ground wire lead-out terminal is located at a relatively low place, diagnosis work is easy and safe. Further, since a slot antenna is not required, the cost is low.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a portion serving as an antenna.

FIG. 3 is a block diagram of an electromagnetic wave receiving device including a noise removing device.

FIG. 4 is a waveform diagram when only external noise occurs.

FIG. 5 is a waveform diagram when an electromagnetic wave is generated in the gas insulating device.

FIG. 6 is an explanatory diagram of a portion serving as an antenna according to a second embodiment.

FIG. 7 is an explanatory diagram of a portion serving as an antenna according to a third embodiment.

FIG. 8 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Ground wire lead-out terminal 3 Coaxial cable 3a Core wire 3b Shield wire 5 Insulation diagnostic device 8 'Ground wire 12 Ground lead 13 Ground part 23 Ferrite core 25 Conductive material

Claims (3)

[Claims] 1. An insulation diagnosis method for an electric device having a grounding device, wherein an electromagnetic wave due to partial discharge is detected from a ground wire lead-out terminal connected to the grounding device. 2. An insulation diagnostic apparatus for an electric device having a grounding device, comprising: a ground wire lead-out terminal connected to the grounding device; and a coaxial cable and a ground lead connected to the lead-out terminal. 3. The apparatus according to claim 2, wherein a ground lead connected to the ground wire lead-out terminal is inserted through a ring-shaped ferrite core having a high impedance with respect to a high frequency.