JPH01455A - Gas sensor in oil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas-in-oil sensor suitable for detecting hydrogen gas dissolved in oil.

(Prior art) As is well known, in transformers, capacitors, reactors, and other oil-filled electrical equipment, insulating oil is decomposed and hydrogen gas is generated due to abnormalities such as local corona discharge or local heating. It is known to do. Therefore, by detecting hydrogen gas, abnormalities in electrical equipment can be detected.
It will be possible to detect accidents before they occur.

Conventionally, such hydrogen gas has been detected by collecting insulating oil from an electric machine, extracting dissolved gas from this, and analyzing it using a gas chromatograph. However, with this method, there are inconveniences such as the fact that analysis cannot be performed at the site where electrical equipment is installed, and online analysis cannot be performed.

(Problems to be solved by the invention) This invention solves the following problems when measuring hydrogen gas dissolved in oil:
The purpose is to make it possible to measure the insulating oil by simply immersing it in the insulating oil without having to sample the insulating oil or extract the dissolved gas.

(Means for Solving the Problems) The present invention provides a thin film of metal oxide on the surface of an insulating substrate, and forms a sensor body by forming a pair of electrodes facing each other on the surface. The device is characterized in that the main body is sealed inside a bag made of polyimide resin film under reduced pressure.

(Example) An example of the present invention will be described with reference to the drawings. 1 is a film-like substrate made of a resin such as polyethylene terephthalate, or a substrate made of an inorganic insulating material such as Al2O, 5i02, etc., and 2 is a thin film made of a metal oxide provided on the surface of the base Fil.

This is, for example, SnO,, Tie, -〇3, InO2
Other jets or composites of two or more of these can be used.

This type of metal oxide is known to have a surface resistance that changes with hydrogen gas.

Note that the thin film of these metal oxides is appropriately provided by an IVD method, an IBS method, a vacuum evaporation method, a plasma CVD method, or the like.

A pair of electrodes 3 facing each other are formed on the surface of the thin film 2. This is preferably comb-shaped as shown in the figure. The electrode 3 is made of, for example, Au. Note that a lead is connected to the electrode 3 and led out from a bag to be described later.

The sensor main body 4 is constructed as described above, and in the present invention, the sensor main body 4 is sealed inside a bag 5 made of a polyimide resin film under reduced pressure. Polyimide resin has the property of selectively permeating hydrogen gas. Moisture is removed from around the sensor body 4 by reducing the pressure inside the bag 5 and enclosing it together with dry air.

The bag 5 containing the sensor body 4 is immersed as it is in the insulating oil of the electrical equipment to be analyzed. A film made of polyimide resin selectively transmits hydrogen gas compared to insulating oil and other gases.

When the metal oxide thin film 2 comes into contact with and reacts with the permeated hydrogen gas, the surface resistance of the thin film 2 changes depending on the concentration of the hydrogen gas. Therefore, by detecting this surface resistance as the resistance between the electrodes 3,
You will be able to know the concentration of hydrogen gas.

Next, an experimental example of this invention will be explained. Thickness 15μy
a. The surface of the substrate 1 made of a 50 mm square polyethylene terephthalate film is coated with a thickness of 1.0 mm by the IVD method.
A thin film 2 of SnO, which is a metal oxide, is provided on the surface of the thin film 2, and a comb-shaped electrode 3 is formed with Au on the surface of the thin film 2.
A sensor main body 4 was constructed. This is then placed inside a bag 5 made of a polyimide film with a thickness of 5 μm under reduced pressure (10 To
rr) After that, it was sealed together with dry air.

Figure 3 shows the rate of resistance change (resistance value after reacting with hydrogen gas/reaction This is a characteristic curve that is a graph of the previous initial resistance value. According to this, it is clear that the resistance change rate changes approximately linearly with respect to the hydrogen gas concentration.

Figure 4 shows the characteristics showing the correlation between the hydrogen gas concentration in the same pond, measured by the gas sensor according to the present invention, measured value A (concentration in oil equivalent value), and measured value B, measured by a gas chromatograph. It is a curve. According to this, when the hydrogen gas concentration is 50 ppm or more, both sides constant value A
, B have almost the same value.

As a result of the above, when the hydrogen gas concentration is measured by the gas sensor according to the present invention, the resistance changes with high sensitivity in response to the concentration, and the measured value is an accurate value that is almost comparable to the measured value by a gas chromatograph. It is understood that

(Effects of the Invention) As detailed above, according to the present invention, it is possible to measure the concentration of hydrogen gas dissolved in oil with a simple operation of simply immersing it in the oil to be measured. Therefore, it also has the effect of being able to perform on-line analysis.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a front view of the sensor body, Fig. 3 is a characteristic curve diagram showing the rate of change in resistance, and Fig. 4 is a characteristic curve showing the correlation of measured values. It is a curve diagram. 1... Substrate, 2... Thin film, 3... Electrode, 4...
Sensor body, 5... bag, mouth ≧ ”ρ

Claims (1)

[Claims] The sensor body is constructed by providing a thin film of metal oxide on the surface of an insulating substrate and forming a pair of electrodes facing each other on the surface, and the sensor body is placed inside a bag made of a polyimide resin film. A gas-in-oil sensor that is depressurized and sealed together with dry air.