JPH04290957A - Insulating oil deterioration sensing device - Google Patents

Abstract

PURPOSE:To selectively sense the acetilene contained in an insulating oil. CONSTITUTION:At a window 3 installed in the wall surface of a vessel 2 a working electrode 4 is furnished, in which a metal 4b is formed on a diaphragm 4a consisting of a porous insulative film, while a reference electrode 7 is arranged at a window 5 installed in the other side wall surface, and therein dilute sulfuric acid is accommodated as an electrolyte 8. By a constant voltage circuit 10 a potential is impressed between these working electrode 4 and reference electrode 7, which is higher than the oxidating potential than acetylene and lower than the oxidating potential of ethylene. The acetylene having passed through the diaphragm 4a is oxidated and generates an oxidative current between the electrodes which is proportioned to the concentration. No electrolytic current will be generated even though ethylene passes the diaphragm 4a. Hydrogen, ethane, methane, CO, and CO2 are also contained in insulating oil, but a gas sensor 1 of constant voltage electrolysis type exhibits a very low sensitivity to these components, and therefore the acetylene in the insulating oil can be sensed with high sensitivity as long as the ethylene sensitivity is set low relative to the acetylene.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device suitable for inspecting the degree of deterioration of insulating oil sealed in transformers, circuit breakers, etc.

0002

[Prior Art] Transformers, circuit breakers, etc. that are filled with insulating oil to increase insulation voltage deteriorate due to partial discharge or local overheating that occurs during long-term use, which can lead to accidents. Insulating oil is being tested. This test usually involves separating gaseous components from insulating oil sampled from electrical equipment, and separating this gas into components such as hydrogen, carbon monoxide, carbon dioxide, methane, ethane, ethylene, and acetylene using a gas chromatography analytical column. This is done by measuring the concentration of each component using a gas chromatograph detector such as a hydrogen flame ionization detector.

[0003] However, such an apparatus requires the same structure and operation as a gas chromatograph, and has the problem that the apparatus is large and complicated, making it inconvenient to handle outdoors. In order to solve this problem, at least acetylene is selected because insulating oil undergoes high-temperature thermal decomposition and specifically produces acetylene when a fatal failure such as arc discharge or partial discharge occurs. A device with a simplified structure that can be used outdoors has been proposed so that it can be detected visually, but since it essentially uses the same principle as a gas chromatograph, it still has a complex structure and is large in size. I have a problem with becoming.

0004

[Problems to be Solved by the Invention] The present invention has been made in view of these problems, and its purpose is to eliminate gases contained in insulating oil without the need for gas separation means. An object of the present invention is to provide a novel insulating oil deterioration detection device that can selectively detect the presence or absence of acetylene.

[0005]

[Means for Solving the Problems] In order to solve such problems, in the present invention, a window provided on the wall of the container,
A working electrode in which a gold layer is formed on a porous electrical insulating film and a counter electrode in which a counter electrode material is formed are provided to accommodate an electrolytic solution, and the oxidation potential is greater than that of acetylene and ethylene is present between the working electrode and the counter electrode. A potential smaller than the oxidation potential was applied.

[0006]

[Operation] Acetylene passing through the porous electrical insulating film is oxidized by the potential applied to the working electrode and the counter electrode, producing an oxidation current between the two electrodes. The ethylene that has passed through the porous electrical insulating film has only a lower potential applied between the working electrode and the counter electrode than the one that would oxidize the ethylene.
It is not oxidized, has an extremely small oxidation current, and also has a small oxidation current due to the inflow of carbon monoxide, hydrogen, etc., which have a higher oxidation potential than ethylene. As a result, only acetylene among the gas components contained in the insulating oil can be detected with high selectivity.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below based on illustrated embodiments. FIG. 1 shows an embodiment of the present invention, and reference numeral 1 in the figure is a constant potential electrolysis type gas detector, in which a working electrode 4 is installed in a window 3 formed in the side wall of a container 2. A counter electrode 6 and a reference electrode 7 are arranged in a window 5 formed in the other side wall, and dilute sulfuric acid is contained as an electrolytic solution 8.

The above-mentioned working electrode 4 uses a synthetic resin membrane having gas permeability and water repellency, for example, a porous fluororesin membrane, as the diaphragm 4a, and gold (Au) is deposited on the surface of the membrane to form a gold layer. 4b, and is attached to the window 3 of the container 2 so that the gold layer 4b is immersed in the electrolyte 8. The counter electrode 6 and the reference electrode 7 are also constructed by printing a thick layer of platinum black on a gas-permeable resin film and firing it.Similarly to the working electrode 4, the platinum black layer is brought into contact with the electrolyte 8, and a window is formed. It is attached to 5. A constant voltage circuit 10 is connected to the working electrode 4 and the counter electrode 6 via a load resistor 9.

The constant voltage circuit 10 operates at a potential higher than the potential at which acetylene is oxidized and lower than the potential at which ethylene is oxidized, for example, at least minus 0.3 volts or more at plus zero.
．． It is configured to generate a potential of 1 volt or less. Further, a measuring circuit 11 is connected to both ends of the load resistor 9 to detect the electrolytic current flowing through the working electrode 4 and the counter electrode 6. Note that reference numerals 12 and 13 in the figure indicate membrane fixing members.

First, standard gases are prepared by diluting hydrogen with air to a concentration of 300 PPM, carbon monoxide to 200 PPM, ethylene to 50 PPM, and acetylene to a concentration of 20 PPM. The electrolytic voltage is varied while air as a carrier gas is supplied, and the electrolytic current, so-called dark current, at each voltage is measured (I in FIG. 2). In addition, by gradually lowering the potential of the working electrode while flowing a standard gas made of ethylene diluted with air, we obtained the highest current that corresponds to the same current as when air was supplied, that is, the dark current (I in Figure 2). The potential, in other words, the potential Ve at which the electrolytic current caused by ethylene disappears (plus 0.1 volt in the example shown in FIG. 2) is measured (II in FIG. 2). Further, a standard gas prepared by diluting acetylene with air is flowed, and the potential applied to the working electrode 4 is gradually increased to the lowest potential Va (shown in FIG. 2) at which an electrolytic current greater than the dark current (I in FIG. 2) is generated. In the example shown in FIG.
II). Any value between the two potentials Va and Vb thus obtained (from minus 0.3 to plus 0.1 volts), for example minus 0.1 volt, is applied to the working electrode 4. The potential of the constant voltage circuit 10 is set.

When a standard gas prepared by diluting acetylene with air is supplied to the detector 1 after completing such preparations, acetylene passes through the diaphragm 4a of the working electrode 4 together with the air, dissolves in the electrolytic solution 8, and becomes active. Oxidation occurs due to the potential applied between the gold layer 4b of the electrode 4 and the counter electrode 6. As a result, an electrolytic current proportional to the acetylene concentration is generated, and a measurement signal is generated at the load resistor 9. Similarly, when a standard gas prepared by diluting ethylene with air is supplied to the detector 1, the ethylene passes through the diaphragm 4a of the working electrode 4 together with the air and dissolves in the electrolyte 8, but the gold layer 4b of the working electrode 4 and the counter electrode 6 Since the potential applied between is lower than the potential that would oxidize ethylene, no electrolysis occurs and no measurement signal is generated.

Furthermore, similar measurements were carried out for ethane, methane, hydrogen, carbon monoxide, and carbon dioxide contained in insulating oil, and it was found that regardless of the type of metal constituting the working electrode, the constant potential electrolysis method Gas detectors generally cannot redox saturated carbon, so they are not sensitive to ethane and methane, and they are not sensitive to carbon dioxide at all, and their sensitivity to carbon monoxide is extremely low ( IV in Figure 2). Furthermore, it has no sensitivity to hydrogen, and outputs a signal almost at the same level as air (V in the same figure). Needless to say, these ethane, methane, carbon dioxide, carbon monoxide, and hydrogen are contained in deteriorated insulating oil, but they are not important factors in deterioration inspection of insulating oil, so these components are not included. Lack of sensitivity is not an obstacle to deterioration testing of insulating oil. By the way,
In the potentiostatic electrolytic gas detector 1 of this embodiment, in the above-mentioned set potential range (Va to Ve), when the measurement sensitivity of acetylene is taken as the standard, the measurement sensitivity ratio of ethylene is 1.4.
×10 to the minus cube power (I in Figure 3), and the hydrogen measurement sensitivity ratio is 4 × 10 to the minus cube power (I in the figure).
I), and the measurement sensitivity ratio for carbon monoxide was 1.6×10 to the minus fourth power (III in the same figure). In particular, ethylene, which is detected with almost the same sensitivity as acetylene with other types of detectors such as thermal conduction detectors and hydrogen flame ionization detectors, has a measurement sensitivity of approximately 1/2 with the potentiostatic gas detector 1. It is extremely low, 1000 or less, and acetylene can be selectively detected. When the set potential is deviated from these set potentials, the ethylene measurement sensitivity increases rapidly as the set potential increases.

Next, without causing arc discharge or partial discharge,
Hydrogen 150PM and carbon monoxide 100P so that the composition ratio is the same as that of the gas components contained in insulation oil that has simply deteriorated over time.
The first sample gas prepared by mixing PM and 25 PPM of ethylene into air was used as a sample, and when this sample was measured using the potentiostatic electrolytic gas detector 1, the relative output was found.
A signal of 1" was obtained.Next, when a second sample gas prepared by mixing acetylene, which is specifically generated by electric discharge, into the first sample gas at a concentration of 2 PPM was measured, the relative output was "2". I got a signal of .5”. As a result,
Acetylene concentration is approximately 1/275 compared to other components
Despite this being extremely low, there was a difference of approximately two and a half times in the signal level between the two depending on the presence and absence of acetylene, making it clear that acetylene contained in insulating oil could be specifically detected.

[0014] From this, the output of the gas sampled from the insulating oil of a transformer that has been used for a long time but has not caused arc discharge or local discharge, such as the above-mentioned first sample gas, is set as the threshold value. By doing so, it is possible to determine whether the measured value of the gas in the insulating oil collected from the transformer exceeds the set threshold, and if the measured value exceeds the threshold, it is determined whether or not it contains acetylene. It can be determined that there is a high possibility that the electrical equipment from which the insulating oil was collected is causing arc discharge or local discharge.

FIG. 4 shows an embodiment of an insulating oil deterioration determination device using the above-mentioned constant potential electrolytic gas detection device. A first tube 21 whose one end is immersed in insulating oil and a second tube 22 whose one end is located in the space B of the container 20 are inserted into the sample container. The other ends of these pipes 21 and 22 are connected to an air pump 25 and a metering tube 26 via a switching valve 23, and during sampling, the air in the flow path is connected to the sampling container 20, the air pump 25, and the metering tube 26. A first flow path (the flow path indicated by a solid line in the figure) is formed to allow circulation. The aforementioned detection device 29 is connected to the switching valve 23 via an air intake port 27 and an oil removal filter 28, and during measurement, external air taken in by a pump 25 from the air intake port 27 is sent into a measuring tube 26. ,
The detection device 2 detects the sample gas stored in the measuring tube 26.
A second flow path (the flow path indicated by a dotted line in the figure) is formed so that the liquid is discharged to 9.

In this embodiment, when the insulating oil A collected from the transformer is stored in the container 20, the switching valve 23 is switched to the first flow path, and the air pump 25 is operated, the air in the flow path is removed from the pipe. 21 into the insulating oil A, the gas component dissolved in the insulating oil A is liberated and discharged into the space B of the container 20. The air in the space B is sucked out by the pump 25 via the other pipe 22, passes through the metering pipe 26, and is discharged again from the pipe 21 into the insulating oil. Thereafter, air circulates through such a path, and the gas component dissolved in the insulating oil A is discharged to the air in the flow path. After performing bubbling for a predetermined time in this manner, when the switching valve 23 is switched to the second flow path (the flow path indicated by the dotted line in the figure), the air contained in the metering tube 26 passes through the filter 28. and is discharged to the detection device 29. As a result, as described above, the detection device 29
A measurement signal corresponding to the gas component contained in the air in the metering tube 26 is output.

[Example] Acetylene, ethylene, hydrogen,
In order to investigate the detection sensitivity for acetylene when carbon monoxide is mixed, measurements were made using 5 ml of each of these gases mixed with air to a concentration of 100 PPM and the gas from which acetylene was removed. However, detection peaks as shown by P1 and P2 in FIG. 5 were obtained. As a result, although all the gases had the same concentration, the peak height was about 1/17 when acetylene was not included. Next, in order to investigate the detection limit of acetylene in the presence of ethylene, hydrogen, and carbon monoxide, hydrogen 150PM and carbon monoxide 10PM were tested.
The above-mentioned first sample gas in which 0 PPM and 25 PPM of ethylene are mixed in air and the gas in which 5 PPM of acetylene is mixed are each stored in 5 ml measuring tubes, and are sent to the gas detection device 29 at time intervals using dry air. And, as shown in FIG. 6, the unimodal peak outputs P3, P
I got 4. As is clear from the figure, acetylene is 5P
Peak P4 caused by PM-containing gas has a peak height 3.2 times that of peak P3 of the first sample gas, even though it contains only about 5/275 of acetylene as other components. became. Furthermore, in order to investigate the concentration of acetylene contained in the first sample gas, it was possible to identify it even in the presence of other gases.
．． When a sample gas containing 5 PPM and 1 PPM of acetylene was measured, the measurement results shown in P5 and P6 of the figure were obtained. From this, if the amount of acetylene is approximately 1/275 of that of other gases, the signal will be approximately twice that of a gas that does not contain acetylene, so this is simply the output level of insulating oil that has deteriorated over time. By setting L to the alarm level, you can easily and reliably distinguish on-site between insulating oil that has simply deteriorated over time and insulating oil that has caused arcing or local discharge in addition to aging. It turns out that you can get it.

[Comparative Example] Instead of the above-mentioned working electrode with a gold layer formed thereon, a working electrode with platinum black formed on a porous synthetic resin film by vapor deposition, which is often used in constant potential electric field type gas sensors, was used. , we performed measurements on acetylene, ethylene, hydrogen, and carbon monoxide while changing the set potential between the working electrode and the counter electrode, and found that the potential can be set essentially, that is, practically, as shown in Figure 7. It was found that the measurement sensitivity for ethylene is higher than the measurement sensitivity for acetylene in the above range. $ In this example, the case where gas components separated from insulating oil were directly measured was explained, but conventional gas chromatography method, that is, separating gas components contained in insulating oil into individual components using a separation column, By using the potentiostatic electrolytic gas detector shown in the above example as a gas chromatograph detector in which the separated gas is detected using a hydrogen flame ionization detector or a thermal conduction detector, extremely low concentrations of acetylene can be detected. It is clear that it is possible to realize a gas chromatograph that can detect with high sensitivity.

Furthermore, in this example, the case was explained in which the gold layer of the working electrode was formed by vapor deposition, but gold black was mixed with a binder, thick film was printed on a porous synthetic resin film, and this was baked. It is clear that the same effect can be achieved even if a method of sputtering gold (Au) onto a porous synthetic resin film is applied. Of course, depending on the method of forming the gold layer formed on the working electrode and the platinum layer formed on the counter electrode, their activity changes slightly and the oxidation-reduction potential of the gas to be measured changes.As mentioned above, the oxidation potential of ethylene and acetylene is It is clear that the potential must be measured and appropriately changed to the optimum potential corresponding to the method of forming the gold layer of the working electrode and the platinum layer of the counter electrode.

Furthermore, although the above embodiments have been explained using air as an example of the carrier gas, even if a gas such as nitrogen or argon to which a constant potential electrolysis type gas detector is insensitive is used, It is clear that similar effects can be achieved.

[0021]

[Effects of the Invention] As explained above, in the present invention,
A working electrode with a gold layer formed on a porous electrical insulating film and a counter electrode with a counter electrode material are provided in a window provided on the wall of the container to accommodate the electrolyte, and acetylene is placed between the working electrode and the counter electrode. Since we applied a potential greater than the oxidation potential of ethylene and smaller than the oxidation potential of ethylene, the acetylene contained in the insulating oil has a 100
It can detect with such high sensitivity and easily determine the deterioration of insulating oil with the same configuration and handling as a normal electrochemical gas measuring device, without the need for any special gas separation means such as columns. be able to. In addition, when used as a gas chromatography method gas detection means that uses an analytical column to separate sample gas into components, it is possible to not only detect trace amounts of acetylene, but also to detect the amount of acetylene that is emitted from the analytical column. By changing the potential setting of the working electrode in accordance with the retention time of a specific component, it is possible to realize a device that can measure the concentration of each component.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the potential of the working electrode and measurement sensitivity in the same device.

FIG. 3 is a diagram showing the ratio of the measurement sensitivity of acetylene to the measurement sensitivity of other gases in the same device as a reference.

FIG. 4 is a configuration diagram showing an embodiment of a deterioration inspection device using the detection device shown in FIG. 1;

FIG. 5 is a diagram showing the results of measurements of a sample in which acetylene, ethylene, carbon monoxide, and hydrogen were each adjusted to 100 PPM, and a sample that did not contain acetylene.

FIG. 6 is a diagram showing measurement results when the concentration of acetylene in a gas mixture of ethylene, carbon monoxide, and hydrogen is extremely low.

FIG. 7 is a diagram showing the settings of the working electrode and the measurement sensitivity of each gas when platinum is used for the working electrode.

[Explanation of symbols]

1 Constant potential electric field type gas detector 2 Container 3. Window 4 Working electrode 4a Diaphragm 4b gold layer 5 Window 6. Opposite 7 Reference pole 8 Electrolyte 9 Load resistance 10 Constant voltage circuit 11 Measurement circuit 20 Sampling container 21, 22 tube 23　Switching valve 25 Air pump 26 Metering tube 28 Oil removal filter 29 Constant potential electric field type gas detector

Claims (1)

[Claims] Claim 1: A working electrode in which a gold layer is formed on a porous electrical insulating film, a counter electrode and a reference electrode in which a counter electrode material is formed are provided in a window provided on the wall of the container, and an electrolytic solution is accommodated therein. An insulating oil deterioration detection device in which a potential greater than the oxidation potential of acetylene and smaller than the oxidation potential of ethylene is applied between an electrode and a reference electrode.