JPH02167466A - Metallic foreign matter detecting device for gas insulation equipment - Google Patents

Abstract

PURPOSE:To detect metallic foreign matter contaminated in a gas insulation equipment with high sensitivity by interposing a pedestal between an AE (ultrasonic) sensor and the contact surface of a metallic container. CONSTITUTION:When the metallic foreign matter P is contaminated in the metallic container 1 and a specific voltage is applied to a high voltage conductor 2, the foreign matter P bounds on the internal surface of the container 1 at random with an electric force to generate an ultrasonic wave W. The wave is propagated spreading in the container 1 where insulation gas is charged and when it reaches the position where the AE sensor 4 is fitted, the sensor 4 detects the wave through the pedestal 8 fitted between the contact surface 9 of the container 1 and the sensor 4. The signal quantity of the ultrasonic wave W sent to the sensor 4 is larger and larger as the contact surface 9 is wider and wider. Then the energy density of the ultrasonic wave W is increased by passing the wave through the pedestal 8 which decreases in sectional area gradually to the sectional area of the sensor 4. Consequently, the ultrasonic wave W generated by the foreign matter P is easily detected by the sensor 4 with good sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a device for detecting metal foreign matter inside gas-insulated equipment using a gas with excellent insulating performance such as SF6 gas as an insulating medium.

(Prior art) A high-voltage conductor is placed in a metal container at ground potential, and a gas with excellent insulation performance, such as S, is placed in the metal container.
In recent years, gas insulated equipment that is compressed and filled with F6 gas to ensure insulation has been increasingly used. by the way,
Although this SF6 gas exhibits very excellent insulating properties under an equal electric field, the insulating performance is extremely degraded under an unequal electric field.

There are many possible factors that can disrupt the electric field distribution within gas-insulated equipment and create an unequal electric field, but the main ones include defects such as dents on the surface of high-voltage conductors, and defects that get mixed into the interior during assembly or transportation. Examples include metallic foreign matter. Of course, in addition to this, poor contact in the high voltage section due to an assembly error, and defects in the insulating spacer such as voids may also occur.

If an unequal electric field is formed in gas-insulated equipment due to the above-mentioned defects, partial discharge will occur during operation.
In the end, there is a possibility that the entire road will be destroyed.

Therefore, it is necessary to reliably detect an abnormality in the gas insulated equipment before it leads to total circuit breakdown, and to prevent dielectric breakdown. For this reason, gas-insulated equipment is usually subjected to careful commercial frequency and impulse withstand voltage tests, as well as partial discharge tests, at the factory.Through these tests, internal defects can be detected in advance. It has been devised. In other words, these factory tests detect various defects such as protrusions caused by dents on the surface of the high voltage conductor, metal foreign objects mixed inside, poor contact in the high voltage part due to assembly errors, and even voids in the insulating spacer. can be detected.

Incidentally, such factory tests for gas insulated equipment are generally performed on a unit-by-unit basis. After factory testing, each transport unit is sent to the site, where a large number of divided units are assembled. Therefore, defects may occur during this process after passing the factory test, that is, during transportation or on-site assembly. Therefore, in order to improve the reliability of gas insulated equipment, it is necessary to detect such defects on-site before the start of operation.

Defects that may occur during transportation or on-site assembly include, among the various defects mentioned above, protrusions caused by dents on the surface of high-voltage conductors, poor contact in high-voltage parts due to assembly errors, and metal foreign objects inside. Contamination is an example of this. Of these defects, the first two usually cause a large partial discharge, so the presence or absence of the defect can be determined by partial discharge measurement after on-site assembly. However, with regard to metal foreign matter mixed inside gas-insulated equipment, it is extremely difficult to detect it in an on-site partial discharge test, since the amount of electric charge of partial discharge caused by this type of defect is generally small.

For this reason, several methods have been proposed to detect metal foreign objects that have entered the device during transportation or on-site assembly. One of them is the AE method. This is an ultrasonic sensor (hereinafter referred to as "ultrasonic sensor") that makes contact with the bottom of a metal container and uses the ultrasonic waves generated when a foreign metal object mixed inside gas-insulated equipment bounces on the metal container due to electric force and collides with the metal container. A
It is intended to be measured using an E-sensor.

A specific example is shown in FIG. A high voltage conductor 3 is insulated and supported approximately at the center of the metal container 1 by a disc-shaped insulating spacer 2 in a metal container 1 which is placed approximately horizontally on the ground and is at ground potential. Roughly speaking, an AE sensor 4 is attached to the bottom of the outer surface of the metal container 1. The output of this sensor 4 is guided through a preamplifier 5 and a main amplifier 6 to an indicator 7, where a predetermined display is performed.

Thereby, the presence of metal foreign matter P mixed into the metal container 1 can be known.

(Problems to be Solved by the Invention) However, such conventional AE methods have the following problems.

First, in the gas insulated equipment shown in FIG. 5, when a gas insulated switch (not shown), for example, a disconnector, opens or closes, a surge voltage is generated.

At this time, a surge voltage also occurs in the metal container 1, and its peak value reaches several thousand volts. Therefore, this surge voltage is also applied to the AE sensor 4 attached to the metal container 1. Therefore, the preamplifier 5, the main amplifier 6, and the rough indicator 7 are connected to the AE sensor 4.
are exposed to such high surge voltages. For this reason, phenomena such as malfunction or failure of the measuring instrument occurred, and detection by the AE sensor 4 could not be performed. This is a serious problem especially when the AE sensor 4 is used for constant continuous monitoring.

Further, although such conventional AE methods have higher detection sensitivity than partial discharge measurement, it is difficult to say that it is sufficient for practical use. That is, although the metal container 1 and the AE sensor 4 are attached as closely as possible, the acoustic impedance inevitably becomes discontinuous at the contact surface Q, and a portion of the ultrasonic waves are rejected.

Therefore, the amount of ultrasonic waves reaching the AE sensor 4 decreases, and the detection sensitivity decreases.

Furthermore, the dog marks of the △E sensor that can be manufactured are very small compared to the size of the metal container 1, so only a small portion of the ultrasonic waves that are distributed and propagated throughout the metal container reach the AE sensor. There were also problems such as low detection sensitivity.

Such problems are not limited to detection devices using AE sensors, but apply to all foreign object detection devices that detect internal abnormalities by bringing a sensor into contact with the outer surface of a metal container.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art as described above, and to provide a metal foreign object detection device for gas-insulated equipment that can easily detect metal foreign objects, has a simple configuration, and is highly reliable.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the invention as set forth in claim 1 provides a method in which a high voltage conductor is placed in a metal container filled with an insulating gas. In the gas insulated equipment installed, there is a gap between the outer surface of the metal container and the sensor, where the adhesive area with the metal container is A.
, is equipped with a seat that is larger than the contact area with the E sensor.

In addition, the invention described in claim 2 forms a detection surface of a sensor that detects elastic waves generated when a metal container collides with a metal foreign object through a seat made of hard glass having a silicon dioxide content of 80% or more. This is what I did.

(Function) In the invention set forth in claim 1, since the seat is installed so that the contact area with the metal container is larger than the contact area with the sensor, the seat is perceived as having a larger area than the sensor area. The generated ultrasonic vibrations can be condensed and transmitted to the AE sensor, allowing larger vibration energy to reach the sensor.

Thereby, the ultrasonic waves generated by the collision between the metal foreign object and the inner wall of the metal container can be detected by the sensor extremely efficiently.

In the invention set forth in claim 2, since the sensor is attached through hard glass, which is an excellent insulating material, the sensor is not directly exposed to surge voltage. Furthermore, since attenuation of elastic waves by hard glass is almost negligible, detection sensitivity does not decrease.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

First, FIGS. 1 and 2 are embodiments corresponding to the invention set forth in claim 1. In FIG. , a high voltage conductor 3' is insulated and supported by an insulating spacer 2. This metal container 1 contains a gas with excellent insulation performance,
For example, SF6 is compressed and filled at a predetermined pressure. An AE sensor 4 is attached to the outer surface of the metal container 1 via a pedestal 8 whose acoustic impedance is approximately the same as that of the metal container, and the output of this sensor is transmitted to a preamplifier 5 and a main amplifier 6. It is led to the indicator 7 through the.

In FIG. 1, it is assumed that a small metal foreign object P is mixed into the metal container 1. In this state, when a predetermined commercial frequency voltage is applied to the high voltage conductor 2, the metal foreign matter P repeatedly bounces randomly on the inner surface of the metal container 1 due to the electric force. At this time, that is, when the metal foreign object P collides with the inner surface of the metal container 1, an ultrasonic wave W is generated. This ultrasonic signal @W spreads and propagates through the metal container 1, and when it reaches the position where the AE sensor 4 is attached, the E sensor is attached to the AE sensor through the contact surface 9 between the base 8 and the metal container. Propagates and is detected. Therefore, the amount of ultrasonic signal transmitted to the AE sensor is
The wider the contact surface 9 between the pedestal 8 and the metal container 1, the more sensors can be attached. When the ultrasonic signal W captured at the contact surface 9 with the wide metal container is transmitted to the AE sensor 4 through the pedestal 8 whose cross-sectional area gradually decreases to the cross-sectional area of the AE sensor, the energy density of the ultrasonic signal increases. is condensed. As a result, the ultrasonic signal caused by the metal foreign object P can be easily detected with high sensitivity by the AE sensor.

In this way, by installing the AE sensor via a pedestal whose contact area with the metal container is larger than the contact area with the AE sensor, it is possible to increase the energy density of the ultrasonic signal transmitted to the AE sensor. Even minute metal foreign substances that could not be detected using conventional methods can be easily detected with good sensitivity.

In addition, in FIG. 1, the case where the AE sensor is attached to the outer surface of a linear metal container is explained as an example, but
FIG. 2 shows a case where the E-sensor is attached to a bent part of a metal container.

In this case, the ultrasonic signal generated by the metal foreign object P propagates along the metal container 1 and reaches the AE sensor 4 without changing its propagation direction.

Therefore, even if the contact surface of the pedestal 8 with the metal container is small, a large detection output can be obtained, and the effects of the present invention can be increased.

Next, an embodiment of the invention of claim 2 will be described with reference to FIGS. 3 and 4. In FIG. 3, a metal seat 12 is fixed by welding to the bottom of a metal container 11 placed substantially horizontally on the ground. Further, a cylindrical metal case 13 is fixed to the seat 12 by welding. This metal case 1
A metal lid 14 is attached to the other end of 3 with bolts 15.

Further, a plug 16 with a cap 17 is attached to the metal i14. Further, an AE sensor 18 is pressed into the metal wooce 13 via an insulating material 19 by a spring 20. As a result, the AE sensor 18
is fixed in close contact with the metal container 11 via a hard glass seat 21. The seat 21 made of hard glass contains 80% or more of silicon dioxide. The upper surface of this seat 21 made of hard glass is finished to have the same curvature as the metal container 11, and is in close contact with the outer peripheral surface of the metal container 11. On the other hand, the bottom surface is flat, and is shaped like a to the detection surface 22 of the AE sensor 18. Further, an output terminal 23 of the AE sensor 18 is connected to the rear plug 16 via a lead wire 24. Therefore,
By removing the cap 17 and connecting a measurement cable (not shown) here, the output of the AE sensor 18 can be easily taken out to the outside.

In the metal foreign object detection device for gas insulated equipment having such a configuration, when the metal foreign object P shown in FIG. 3 collides with the metal container 11, an elastic wave is generated. This elastic wave propagates within the hard glass seat 21 with almost no attenuation, and the AE
The detection surface 22 of the sensor 18 is reached. Here, the elastic waves are converted into electrical signals.

An example of experimental results showing that elastic waves propagate through hard glass with almost no attenuation is shown in Part 4.
As shown in the figure. This is what was sought by the inventor. Three types of insulating materials including hard glass are inserted between the metal container 11 and the AE sensor 18, and the output voltages of the AE sensors 1 and 8 at that time are shown. The vertical axis indicates the case where there is no insulating material, that is, the metal container 11 and the AE sensor 1.
The output when 8 is in direct contact is expressed as 1.0. This shows that hard glass transmits elastic waves extremely efficiently with almost no attenuation.

The output of the AE sensor 18 obtained in this way can be obtained by removing the cap 17 and connecting a measurement cable (not shown) to the output terminal 23 and the lead wire 2.
4. The signal is further led to an indicator (not shown) via a plug 16, where the signal is processed and displayed. Also,
Since the AE sensor] 8 is insulated from the metal container 11 by the hard glass seat 21 and the insulating material 19,
Even if a high surge voltage occurs in the metal container 11, there will be no problem.
Able to perform functions.

In this way, in this embodiment, the seat 21 is made of hard glass, which transmits elastic waves without attenuation and is a good insulator.
The AE sensor 18 is attached to the metal container via.

Therefore, it is possible to provide a method for detecting metal foreign matter that is not affected by surges and has high detection sensitivity.

As shown in the above embodiments, the inventions according to claims 1 and 2 both improve the detection sensitivity by interposing a seat on the contact surface between the sensor and the metal container, and each of the above embodiments improves the detection sensitivity. In the examples, explanations have been made using gas insulated equipment in which a high voltage conductor is disposed in a metal container, or whether this is other gas insulated equipment, such as a gas insulated transformer or a gas insulated zyristor valve device. Of course, the effects of the present invention are not lost. Further, even if a sensor other than the AE sensor is used, for example, a type of sensor that detects acceleration, the same effect can be obtained.

[Effects of the Invention] As described above, according to the present invention, metal foreign matter mixed into gas-insulated equipment can be detected with high sensitivity using a simple configuration in which a seat is interposed on the contact surface between the sensor and the metal container. It is possible to provide a highly reliable metal foreign object detection device in gas-insulated equipment that is ideal for constant monitoring.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of a metal foreign object detection device for cass insulation equipment according to the present invention, FIG. 2 is a cross-sectional view showing a modification of the embodiment shown in FIG. 1, and FIG. FIG. 4 is a graph illustrating its operation, and FIG. 5 is a sectional view illustrating a conventional metal foreign object detection device. DESCRIPTION OF SYMBOLS 1... Metal container, 2... High voltage conductor, 3... Insulating spacer, 4... AE sensor, 5... Preamplifier,
6... Main amplifier, 7... Indicator, 8... Pedestal,
9... Contact surface between pedestal and metal container,] 1... Metal container, 12... Metal seat, 13... Metal case, 14
...metal lid, 15...bolt, 16...connection, 1
7...Cap, 18...AE sensor, 19...
Insulating material, 20... Spring, 21... Hard glass seat, 22... Detection surface, 23... Output terminal, 24...
Lead wire, P...Metal foreign object, W...Ultrasonic wave.

Claims (2)

[Claims] (1) A sensor is placed in close contact with the outer surface of the metal container of gas-insulated equipment, in which a high-voltage conductor is placed inside a metal container at ground potential filled with an insulating gas, and the sensor is placed in close contact with the outer surface of the metal container to detect metal foreign objects inside the container. In a metal foreign object detection device that detects elastic waves generated at the time of a collision, the metal container and the sensor are mounted in close contact with each other via a seat whose contact area with the metal container is larger than the contact area with the sensor. A metal foreign object detection device for gas insulated equipment characterized by: (2) A sensor is placed in close contact with the outer surface of the metal container of gas-insulated equipment in which a high-voltage conductor is placed inside a metal container at ground potential filled with insulating gas, and the sensor is placed in close contact with the outer surface of the metal container to detect metal foreign objects inside the container. In a metal foreign object detection device that detects elastic waves generated during a collision, the outer surface of the metal container has a silicon dioxide content of 80%.
A metal foreign object detection device for gas insulated equipment, characterized in that the metal container and the sensor are attached in close contact with each other via the hard glass seat.