Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-06-09
2002-08-20
Tung, T. (Department: 1743)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S432000, C429S006000
Reexamination Certificate
active
06436257
ABSTRACT:
The present invention relates generally to a means for monitoring the presence of acetylene (i.e. acetylene gas) in a fluid such as, for example, a dielectric fluid (e.g. a dielectric liquid or a dielectric gas).
More especially, this invention relates to a detecting device in which the concentration of acetylene dissolved in a fluid is determined by the measure of an electric current generated by electrochemical oxidation of the gaseous acetylene at a detection electrode.
The present invention may in particular, for example, be exploited as part of a means for the monitoring (e.g. detection) of acetylene in fluid insulated electrical equipment, e.g. to monitor incipient failure conditions. The dielectric fluid may be a dielectric liquid (e.g. oil) or a dielectric gas. More particularly, the present invention relates to an apparatus and method for monitoring acetylene in a dielectric fluid disposed in an interior of an electrical system wherein the dielectric fluid may be subjected to analysis.
BACKGROUND OF THE INVENTION
The following will deal, by way of example only, with the detection of a gas in a fluid which is a dielectric fluid.
Electrical systems are well known in the art which use a dielectric fluid as an insulating substance; these systems include for example transformers, circuit breakers and the like.
It is known that, in the event of a disturbance or malfunction of an above mentioned type of device or system, the result may be the production of one or more gases in the insulating fluid; this may occur for example if a device is working at high temperature or high conditions of electrical stress therein. Such conditions may also produce undesired moisture and/or one or more breakdown products of the dielectric material of the insulating system (i.e. insulating fluid). If such abnormal conditions are allowed to continue uncorrected, this may lead to irreparable damage to the electrical system. A timely (e.g. more or less immediate) detection and/or diagnosis of any such abnormal operation of an electrical apparatus is thus advantageous in order to be able to avoid irreparable harm to such a system.
Accordingly, various monitoring devices and systems have been proposed for the detection of any incipient failure conditions such as for example any undesired increase of the concentration of a fault gas (e.g. a combustible gas such as for example, hydrogen gas, carbon monoxide gas, methane gas, ethane gas, ethylene gas, acetylene gas and the like or a non-combustible gas such as for example, carbon dioxide), moisture (e.g. water), a breakdown product, contaminant substance, and/or the like contained (e.g. dissolved) in the insulating fluid.
Some such detection and/or monitoring systems are, for example, described in Canadian Patent no. 1,054,223 (Bélanger), U.S. Pat. No. 4,112,737 (Morgan), U.S. Pat. No. 4,293,399 (Bélanger et al), U.S. Pat. No. 4,271,474 (Bélangeret al), U.S. Pat. No. 5,070,738 (Morgan) and U.S. Pat. No. 5,271,263 (Gibeault). The entire contents of these patent references as well as any other patent or other types of references which are mentioned therein are incorporated herein by reference.
U.S. Pat. No. 5738773 for example illustrates a fuel cell arrangement for detecting oxidisable components of a gas or vapour. The fuel cell comprises first electrode means and second counter electrode means which are connected by an acidic electrolyte. The electrochemical oxidation of a fuel component in the gas results in the formation of a potential difference between the first and second electrode means; the resultant current and/or potential difference can be detected and associated with the presence and /or concentration of combustible gas detected thereby.
U.S. Pat. No. 4,293,399, for example, describes how the concentration of gaseous hydrogen dissolved in a fluid may be determined by a measure of an electric current generated by electrochemical oxidation of the gaseous hydrogen at an electrode of the detector; i.e. by a measure of a current generated in response to the presence of hydrogen (in a gas). The prior art detecting and measuring means described in this U.S. patent comprises a polymeric membrane permeable to hydrogen gas for contact with a fluid containing dissolved hydrogen gas; an electrolyte capable of facilitating oxidation of the hydrogen gas diffused through the polymeric membrane at a first electrode and reduction of an oxygen-containing gas such as air at a second electrode; and a measuring device connected to the fuel cell for measuring the intensity of the electrical current generated by the electrochemical reaction of oxidation of the hydrogen gas, this intensity being proportional to the concentration of hydrogen in the fluid. See also Canadian Patent no. 1,054,223 (Bélanger) mentioned above.
It is advantageous for such monitoring (e.g. detection) devices, as described above, to be able to provide an accurate as possible detection and/or diagnosis of the incorrect operation of systems such as, for example, transformers, circuit breakers, shunt reactors or any electro-apparatuses using a dielectric fluid as an insulating substance such as a dielectric liquid (e.g. a dielectric oil) or a dielectric gas (e.g. SF
6
gas).
A number of the above mentioned prior art monitoring devices or systems have the drawback that the sample gas received by the detector may have a relatively low concentration of a target gas which it is desired to detect or monitor; e.g. a low concentration of acetylene gas relative to hydrogen gas. In such case, the low concentration of a target gas relative to the other gases present in a sample gas may be such that one or more of the other gases may interfere with the measurement of a predetermined target gas(es). In other words, the precision of the results of the detecting or monitoring device may thus be less than is desired; i.e. due to that fact that one or more extraneous gases may interfere with the reading of the target gas (e.g. acetylene).
The presence, concentration and evolution of even very low concentrations of acetylene dissolved in a dielectric fluid, such as for example a dielectric oil, is a particularly useful indicator of the processes occurring (e.g. default gas production) in the insulated electrical equipment. As mentioned, in addition to acetylene, the dielectric fluid may contain other dissolved gases, such as hydrogen, carbon monoxide, ethylene, ethane, methane, etc.. A reliable analysis of acetylene thus requires a detector having an enhanced selectivity for acetylene at very low concentrations in the presence of other such dissolved gases.
Accordingly, it would be advantageous to have a detector for the specific detection and monitoring of acetylene dissolved in a dielectric fluid such as for example a dielectric oil
It would, in particular, be advantageous to be able to perform the analysis (e.g. detection) of a target gas such as acetylene which forms part of a sample gas mixture.
It is to be understood herein that the expression “sensor component” as well as the words “sensor”, “sensing” and the like include, but are not limited to, activities which involve checking for a substance, detecting a substance, determining the presence of a substance, etc..
It is also to be understood herein that the expression “analysing means for monitoring” as well as the words “monitor”, “monitoring” and the like include, but are not limited to, one or more activities which involve checking for a substance, detecting a substance, keeping track of a substance, determining the presence of a substance, the continuous measurement of a substance, the intermittent measurement of a substance, etc..
SUMMARY OF THE INVENTION
The present invention in accordance with one aspect provides an electrochemical cell (e.g. fuel cell), for generating a current in response to the presence of acetylene in a fluid (e.g. in a gas such as for example a gas sample), said fuel cell comprising first and second gas porous electrode means, and acidic electrolyte means interconnecting said first and second electrode means for facilitat
Babas-Dornea Elena
Noirhomme Bernard
Cusick Ernest G.
Freedman Philip D.
General Electric Company
Tung T.
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