JP4094249B2 - Gas detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to gas detection equipment, especially such as when such internal discharge of insulated electrical devices sulfur hexafluoride gas is sealed as an insulating gas abnormality occurs, produced by decomposition of sulfur hexafluoride gas those concerning the gas detection equipment for detecting a decomposed gas.
[0002]
[Prior art]
In high-voltage electrical equipment such as GIS, sulfur hexafluoride gas or a mixed gas of sulfur hexafluoride gas and nitrogen gas is generally used as an insulating medium, and regular maintenance is performed for its safe operation. Management is done. In this maintenance and management, sulfur hexafluoride gas is partially decomposed by discharge and generates fluorine-containing gas such as sulfur tetrafluoride gas or hydrogen fluoride gas. The presence or absence of fluorine-containing gas or the amount of fluorine-containing gas generated is detected.
[0003]
Japanese Patent Laid-Open No. 2000-105216 proposes a gas sensor for detecting the above-mentioned fluorine-containing gas, and FIG. 4 is a schematic explanatory diagram thereof. In FIG. 4, 1 is a detection electrode, 2 is a fluorine ion conductive solid electrolyte such as fluoride solid electrolysis, 3 is a counter electrode, 4 is a lead wire, 5 is a DC power source, and 6 is an ammeter. The detection electrode 1 and the counter electrode 3 are provided in close contact with the surface of the solid electrolyte 2 so as to face each other with the solid electrolyte 2 interposed therebetween. The lead wire 4 includes a lead wire portion 41 that connects the detection electrode 1 and the ammeter 6, and a lead wire portion 42 that sequentially connects the counter electrode 3, the DC power source 5, and the ammeter 6. When the gas sensor is used, it is installed in the atmosphere of the gas to be detected so that the detection electrode 1 is in contact with the fluorine-containing gas.
[0004]
The DC power supply 5 has a function of applying a DC voltage between the detection electrode 1 and the counter electrode 3 via the lead wire portions 41 and 42, and an electrode reaction occurs in the detection electrode 1 by the application of the DC voltage, and the above described The fluorine-containing gas is electrolyzed, and the electrolysis current at this time is taken out as a sensor output by the ammeter 6. Therefore, the amount of fluorine-containing gas can be known from the current value detected by the ammeter 6. FIG. 4 shows an example of hydrogen fluoride gas (HF) as an example of the fluorine-containing gas.
[0005]
FIG. 5 is a graph showing the change over time of the current value in the conventional gas sensor, where the vertical axis shows the current value appearing on the ammeter 6 and the horizontal axis shows the energization time. As is apparent from FIG. 5, a very large current flows immediately after application of the DC voltage, and then the amount of current gradually decreases and settles to a constant value. A phenomenon in which a large current flows immediately after application of a DC voltage is due to the accumulation of charges in the solid electrolyte 2. That is, the solid electrolyte 2 has a property that a capacitor and a resistor are connected in parallel as an electric circuit element. When a DC voltage is applied, a charging current is charged in the circuit until a constant charge is accumulated in the capacitor. Flowing. The charge accumulation in the solid electrolyte 2 requires a relatively long time of about several minutes.
[0006]
Therefore, since the conventional gas sensor applies a DC voltage as described above, there is a problem that accurate measurement cannot be performed until a certain amount of electric charge is accumulated in the solid electrolyte 2. FIG. 5 shows changes in current values for both cases with and without hydrogen fluoride gas (HF) as an example of a fluorine-containing gas. In either case, a large charge is applied to the circuit immediately after voltage application. Since current flows, accurate measurement cannot be performed. Therefore, in the conventional gas sensor, when a DC voltage is applied for several minutes and the charging current flowing through the circuit becomes a sufficiently small value, the current value is measured and the presence or absence of cracked gas is investigated.
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems in the prior art, and eliminates the influence of the charging current immediately after the voltage application, and can detect the fluorine-containing gas in a short time. it is an object of the present invention to provide a equipment.
[0008]
[Means for solving problems]
The gas detection device of the present invention includes (1) a solid electrolyte, a detection electrode provided on one surface of the solid electrolyte and in contact with a fluorine-containing gas generated by decomposition of sulfur hexafluoride gas as a detection gas, the solid A counter electrode provided on the other surface of the electrolyte, an ammeter for measuring a current value flowing in a closed circuit including the detection electrode and the counter electrode, and applying an AC voltage between the detection electrode and the counter electrode An AC power supply is provided.
[0009]
(2) In the above (1), the solid electrolyte is a fluoride solid electrolyte.
[0010]
(3) In the above (1) or (2), the detection electrode is made of a reaction promoting metal that promotes an electrode reaction in the detection electrode .
[0011]
(4) In the above (1), the frequency of the AC voltage is 1-1000 Hz.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the following embodiments, the same parts as those shown in the prior art of FIG. 4 are denoted by the same reference numerals, and the description of each content is referred to the description in FIG. Is omitted.
[0013]
Embodiment 1.
1 to 2 are diagrams for explaining the first embodiment of the gas detection apparatus of the present invention. FIG. 1 is a schematic explanatory view of the first embodiment, and FIG. 2 shows the gas detection apparatus of FIG. It is a graph which shows a time-dependent change of the electric current value in the case of using. In FIG. 1, reference numeral 7 denotes an AC power source. In the first embodiment, an AC power source 7 is used instead of the DC power source 5 in the prior art of FIG. 4, and the other points are the same as those of the prior art.
[0014]
As the forming material and forming method of the detection electrode 1, the solid electrolyte 2, and the counter electrode 3 in the first embodiment, techniques that are conventionally known or practically used in this field can be adopted without limitation. Now, some examples of preferable ones in the prior art will be described.
[0015]
The detection electrode 1 is preferably made of a material that can electrolyze the fluorine-containing gas by an electrode reaction under as low a voltage as possible. Examples of such a material include transitions such as platinum, palladium, iridium, ruthenium, and rhodium. Those formed from at least one of metals or those formed from a metal material containing or containing the above metal material as a main component are preferable. The material for forming the counter electrode 3 is not particularly limited. If it is the same as that of the detection electrode 1, the industrial production of Embodiment 1 is facilitated. As the solid electrolyte 2, a solid electrolyte having good fluorine ion conductivity is generally preferable, and as such a solid electrolyte, for example, a single crystal of LaF ₃ to which about 0.3 mol% of eurobium is added can be exemplified.
[0016]
The detection electrode 1 and the counter electrode 3 can be formed on the surface of the solid electrolyte 2 by vacuum vapor deposition, sputtering vapor deposition, or the like. If the detection electrode 1 is slit-shaped, it can be formed by photolithography and photoetching. .
[0017]
In FIG. 2, the operation of the first embodiment is shown in comparison with that of the conventional gas sensor shown in FIG. 4, where the vertical axis represents the current value appearing on the ammeter and the horizontal axis represents the energization time. As is clear from FIG. 2, in the conventional gas sensor that applies a DC voltage, a very large charging current flows immediately after the voltage application, whereas in Embodiment 1 in which an AC voltage is applied, the current obtained is immediately after the voltage application. It is stable and does not change with time. This is because charge accumulation in the solid electrolyte 2 that occurs when a DC voltage is applied does not occur when an AC voltage is applied. Therefore, in the conventional gas sensor that applies a DC voltage, it takes several minutes to detect the fluorine-containing gas. However, according to the first embodiment, since the influence of the charging current does not occur, immediately after the AC voltage is applied. Accurate detection of fluorine-containing gas becomes possible.
[0018]
Embodiment 2.
FIG. 3 is a graph showing the relationship between the frequency and the current value of the applied AC voltage for explaining Embodiment 2 in the gas detection method of the present invention. In the second embodiment, the gas detection device of the first embodiment is used, and the detection electrode 1 is exposed to an atmosphere in which hydrogen fluoride gas (HF) as an example of a fluorine-containing gas is present and has various frequencies. The current value is compared between the case where the AC voltage is applied and the case where the AC voltage is applied in a state where the gas is exposed to an atmosphere where no hydrogen fluoride gas (HF) or other fluorine-containing gas exists. .
[0019]
As is clear from FIG. 3, the current value obtained is constant regardless of the frequency in an atmosphere in which no fluorine-containing gas such as hydrogen fluoride gas exists, but in the atmosphere in which hydrogen fluoride gas exists, the current value is the frequency. The current value obtained is the same regardless of the presence or absence of hydrogen fluoride gas in a high frequency range of 1000 Hz or higher. This phenomenon shows the frequency characteristics of the mobility of fluorine ions that contribute to the generation of current, and it can be seen that the movement of fluorine ions hardly occurs under a high frequency range higher than 1000 Hz.
[0020]
Therefore, the alternating voltage applied in the gas detection method of the present invention is about 1 to 1000 Hz, particularly about 1 to 500 Hz, and further about 1 to 100 Hz, particularly when the ions to be detected are fluorine ions. It is preferable that
[0021]
【The invention's effect】
As described above, the gas detection device of the present invention is in contact with (1) a solid electrolyte and a fluorine-containing gas that is provided on one surface of the solid electrolyte and generated by decomposition of sulfur hexafluoride gas as a detection gas. A detection electrode, a counter electrode provided on the other surface of the solid electrolyte, an ammeter for measuring a current value flowing in a closed circuit including the detection electrode and the counter electrode, and between the detection electrode and the counter electrode With an AC power supply that applies AC voltage, when ac voltage is applied, charge accumulation in the solid electrolyte that occurs when DC voltage is applied does not occur. This has the effect of enabling detection of fluorine-containing gas.
[0022]
(2) In (1), the solid electrolyte is a fluoride solid electrolyte. (3) In (2), the detection electrode is composed of a reaction promoting metal that promotes an electrode reaction in the detection electrode. In this case, the detection speed and detection sensitivity of the fluorine-containing gas are further improved.
[0023]
(4) In (1) above, if the frequency of the AC voltage is 1 to 1000 Hz, the mobility of fluorine ions contributing to current generation is good. There is an effect that the fluorine gas can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of Embodiment 1 in a gas detection device of the present invention.
FIG. 2 is a graph showing a change with time of a current value in the first embodiment.
FIG. 3 is a graph showing the relationship between frequency and current value of applied AC voltage in Embodiment 2 in the gas detection method of the present invention.
FIG. 4 is a schematic explanatory diagram of a conventional gas sensor.
FIG. 5 is a graph showing a change in current value with time in the prior art.
[Explanation of symbols]
1 detection electrode, 2 solid electrolyte, 3 counter electrode, 4 lead wire, 6 ammeter,
7 AC power supply.

Claims (4)

A solid electrolyte, a detection electrode provided on one surface of the solid electrolyte and in contact with a fluorine-containing gas generated by decomposition of sulfur hexafluoride gas as a gas to be detected; a counter electrode provided on the other surface of the solid electrolyte A gas comprising an ammeter for measuring a current value flowing in a closed circuit including the detection electrode and the counter electrode, and an AC power source for applying an AC voltage between the detection electrode and the counter electrode Detection device. The gas detection apparatus according to claim 1 , wherein the solid electrolyte is a fluoride solid electrolyte. 3. The gas detection device according to claim 1 , wherein the detection electrode is made of a reaction promoting metal that promotes an electrode reaction in the detection electrode. The gas detection device according to claim 1 , wherein the frequency of the AC voltage is 1-1000 Hz.

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