CA1257185A - Gas decomposition detector for gas-insulated electrical apparatus - Google Patents
Gas decomposition detector for gas-insulated electrical apparatusInfo
- Publication number
- CA1257185A CA1257185A CA000490129A CA490129A CA1257185A CA 1257185 A CA1257185 A CA 1257185A CA 000490129 A CA000490129 A CA 000490129A CA 490129 A CA490129 A CA 490129A CA 1257185 A CA1257185 A CA 1257185A
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- Canada
- Prior art keywords
- gas
- detector
- tube
- electrical apparatus
- pressure regulator
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B17/00—Insulators or insulating bodies characterised by their form
- H01B17/36—Insulators having evacuated or gas-filled spaces
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
- G01N31/223—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1254—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of gas-insulated power appliances or vacuum gaps
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- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biophysics (AREA)
- Molecular Biology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Dispersion Chemistry (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
Abstract Decomposition of SF6 gas in gas-filled electrical apparatus, indicative of electrical faults, is detected employing a chemically-reducible color-change detector material which is reduced and changes color on contact with SO2.
The detector is much more sensitive than known pH change indicators.
The detector is much more sensitive than known pH change indicators.
Description
Recently, in the construc,ion of electrical power distribution systems, there has been a tendency toward the use of SF6 gas-filled electrical apparatus, wherein the electrical apparatus is maintained in a sealed enclosure which is filled, usually under 5 high pressure, with SF6 gas. SF6 gas has excellent insulative properties and the SF6 gas-filled apparatus offers advantages such as reduced power losses, better reliability, and increased length of service, over conventional air-insulated apparatus.
A typical SF6 gas-insulated substation may comprise gas-insulated components such as circuit breakers, switches, transformers and metering apparatus, each component having its own gas-filled enclosure, and the various components being interconnected by several hundred meters of buses also having compart~entalised gas-filled enclosures.
In the event of a fault occurring, causing an electrical dis-charge within the apparatus, detection and location of the fault is made difficult by the enclosures which conceal the site of the discharge. The electrical discharge causes decomposition of the ~F6 into gaseous decomposition products, and it is known to extract samples of gas filling and to subject these to analysis through gas chromato~raphy-mass spectroscopy to determine the presence of SF6 decomposition products such as SOF2. However, this procedure is time-consuming and expensive. Detection and location of the fault in a large substation may require that tens of gas samples be withdrawn from the various parts of the system and returned to the laboratory for analysis.
A typical SF6 gas-insulated substation may comprise gas-insulated components such as circuit breakers, switches, transformers and metering apparatus, each component having its own gas-filled enclosure, and the various components being interconnected by several hundred meters of buses also having compart~entalised gas-filled enclosures.
In the event of a fault occurring, causing an electrical dis-charge within the apparatus, detection and location of the fault is made difficult by the enclosures which conceal the site of the discharge. The electrical discharge causes decomposition of the ~F6 into gaseous decomposition products, and it is known to extract samples of gas filling and to subject these to analysis through gas chromato~raphy-mass spectroscopy to determine the presence of SF6 decomposition products such as SOF2. However, this procedure is time-consuming and expensive. Detection and location of the fault in a large substation may require that tens of gas samples be withdrawn from the various parts of the system and returned to the laboratory for analysis.
- 2 - ~257~ ~
There are also known fault detector devices which comprise an indicator responsive to changes in p~l. The gaseous decomposition products of arced SF6 include acids such as HF. Thus, passa~e of the insulatin~ fill gas through a basified pH indicator contain-in~ a certain amount of moisture can provide a color change inresponse to a pH change from basic to neutral or acidic, indica-tive of the presence of aci~ic decomposition products. The acid dissolves to form an acid solution which effects the color change of the indicator. These devices are relatively small and inexpensive, but the solutions resulting from contact of the arced gas with moisture are only very weak solutions and so the detection method is not sensitive. The devices of which the in-ventors are aware have poor sensitivity and require large volumes of usually 10 to 30 litres of arced gas to be withdrawn from the apparatus and passed to the indicator before a readily percep-tible color chanqe takes place. This necessitates long hook up times to the apparatus, and renders the test device inapplicable to the testing oE relatively small gas-filled compartments.
Withdrawal of large volumes of gas can deplete the gas fill to such an extent that the insulative property is impaired and a fault is thereby induced in the apparatus undergoing test.
A quicker and simpler way of locatiny a fault is to sniff the insulating gas, since the decomposition products have a distinctive odor. This practice is highly undesirable, since the decomposition products are toxic.
The present inventors have found that SF6 insulation gas fills, when exposed to a fault, provide, along with other products, a substantial concentration of sulfur dioxide (SO2), whereas SO2 is substantially completely absent from SF6 gas which is not exposed to a fault, and, on the basis of the observation that SO2 is a powerful reducinq agent, have found that the presence o~ SF6 decomposition products indicative of exposure of the SF6 to fault conditions can be readily determined employing a chemically-reduci~le detector material which provides a color change on chemical reduction on exposure to SO2. Accordingly the present invention provides a metho~ of detecting decomposition of an SF6 _ 3 - ~2~7~
~as filling in gas-insulated electrical apparatus comprising withdrawing gas from the apparatus, contacting it with a chemically-reducible detector material which is chemically reduced and changes color on contact with SO2, and observing the color chanqe of the detector material.
Without wishing to be bound by any theory, to the best of applicant's understandingl when an arc passes through SF6 gas in SF6 gas insulated electrical apparatus, a number of gaseous and solid by-products are formed, reflecting the materials, such as conductors and insulator materials which are adjacent to and are effected by the arc. It appears that SOF2 and SO2F2 are the most abundant hy-products formed. On contact with moisture SO2F2 remains stable~ However, for SOF2, a further breakdown occurs:
SOF2 + H2O ~ SO2 ~ 2HF
It appears that sufficient moisture is present, even in the dry industrial grafles of SF6, having a dew point of -40C, to permit for~ation of SOF2 and its conversion, under appropriate conditions, to SO2 in quantities adequate to permit detection of the occurrence of the arc through detection of the SO2 formed thereby.
In view of the relatively powerful properties of SO2 as a reducing agentr and the only relatively weakly acidic nature of solutions formed from dissolution of the arced gas, the chemically-reducible detector system offers much greater sensitivity than the pH indicator-based arrangements.
Thus, the chemically-reducible detector material is much more sensitive to small concentrations of SO2 than the pH indicator materials are toward the acid components of correspondingly decomposed SF6 gas fills, and therefore requires much smaller withdrawals of insulating gas and shorter hook up times, and the detection procedure can be carried out more quickly. It has been found that, surprisingly, and for reasons which are presently not fully understood, the preferre~ so2-reducible detector material ~.25'7~
has much greater sensitivity toward SF6 decomposition products than toward gas mixtures containing SO2 as the only reactive com-ponent. The material is thus outstandingly useful for detecting SF6 decomposition products caused by electrical discharge and for location of electrical discharge faults in complex and ex~ensive SF6-insulated systems.
In one aspect, the invention provides a gas decomposition detector for SF6 gas-insulated electrical apparatus, comprising a pressure-reducing gas pressure regulator, having an inlet for connection to the electrical apparatus and an outlèt for providing a relatively reduced pressure flow, and connected to a detector tube containing a chemically-reducible detector material providing a color change when chemically reduced on contact with S2 present in the gas passed therethrough.
Further advantages and preferred features oE the present detector and method are described hereinafter with reference to the accompanying drawings which show, by way of example only, preferred embodiments of the present invention.
Figure 1 shows partially schematically one form of gas decompo-sition detector apparatus in accordance with the invention.
Figure 2 shows schematically a second form of detector apparatus in accordance with the invention.
~eferring to Figure 1, this shows a detector device employed for detecting SF6 gas decomposition in apparatus which in this instance is an insulated bus comprising a conductor 10, enclosed in a metal casing 11. The casing 11 is compartmentalised in gas-tight fashion by insulating spacers 12 which define between them an SF6 gas-filled compartment 13. The interior of this compartment is accessible, for gas-filling or testing purposes, through a port 14, controlled by a valve 16~ The port 14 is provided with a standard connector 17 with which other standard connectors may be engaged.
~257~
In the preferred form, the detector device is a relatively small, portable device which has its components ~ounted within a hous-ing, indicated schematically in broken lines by the rectangle 13.
The detector device comprises two glass tubes 19 and 21, each containing a chemically-reducible detector material which under-goes a color change on chemical reduction on contact with SO2.
Each tube is supported at its opposite ends in connector blocks 22 and 23, and each connector block has inset in it a pair of resilient plugs 24, each formed with a central bore. Each end of each tube 19 and 21 has a tapering tip which is cushioned and located by the bore through the plug 24. The block 23 at one end is fixed to one end of a rod 26. The block 22 at the other end is slidable longitudinally on the rod 26, which is threaded in this region, and, above the block 22, the rod 26 has threaded on it a collar 27. The collar 27 can be unscrewed to permit the tubes 19 and 21 to be disengaged from the plugs 24, and removed or replaced. On tightening up the collar 27, the peripheries of the tapered ends of the tubes 19 ar1d 21 are urged firmly into positivet sealingl location within the central bores in the plugs 24. A transverse bore 28 passes through the block 22, and similarly a transverse bore 29 passes through the block 23~
Longitudinal bores 31 connect with each transverse bore 28 and 29 and to the interior bore through the plugs 24.
The device further includes a connector 32 connecting through a conduit 33 to a three-position valve 34. Connected to the valve 34 is a vent conduit 36, provided at the opposite end with a con-nector 37. The valve 34 also connects with a main conduit 38 which passes to a pressure~reducing pressure regulator 39. By operation of the three-way valve 34, the conduit 33 can be connected selectively to the vent conduit 36 or to the inlet of the pressure regulator 39. In a third position, the valve 34 closes the conduit 33, and the conduits 36 and 38. The outlet of the pressure regulator 39 connects through a conduit 40 to the transverse bore 28 in the connector block 22. The trans~erse bore 29 in the connector block 23 is connected to an outlet conduit 41 and through a gas flow meter 42 to a connector 43.
~ ~7 ~
In use, one of the detector tubes, e.g. the tube 13, may act as a color-comparison standard or reference, and the gas is passed through only the other tube 21. In the preferre~ form, the detector tubes 19 and 21 are supplied in a sealed condition which protects the detector material inside from contact with S2 which may be present in the ambient atmosphere. Before performing the test, it is necessary to remove the tube 21 from the detector device, and to open the ends of the tube by breaking off its glass tips in a conventional form of tip-breaking device. The opened tube 21 is then replaced between the connect~r blocks 22 and 23, as shown, so that its interior is in communication with the bores through the connector blocks 22 and 23, and the plugs 24, and hence also with the conduits 40 and 41. The intact tapering glass tips of the other tube 19, which remains sealed, serve as obturators closing the bores in the plugs 24 in which the tube 19 is received.
The detector device may in use be positioned adjacent to or may be spaced remotely from the electrical apparatus which is to undergo test. In a typical example, the bus 11 as illustrated may be situa~ed some 2 or 3 meters above ground level, and it will be convenient to place the detector device on or adjacent the ground. In order to conduct the test, it is therefore necessary to connect the connector 17 on the bus 11 to the connector 3~ on the detector device using a lengthy flexible conduit 44. Before conducting the test, air needs to be purged from the conduit 44 so that air or air-diluted fill gas is not passed to the tube 21, which could lead to a false result being obtained. The three-way valve 34 is initially in the position closing the conduit 33. The valve 16 on the bus is opened, and then the valve 34 is operated to connect the conduit 44 to the vent conduit 36, to release gas from the compartment 13 through the vent conduit 36 for a brief period sufficient to purge substantially all air from the conduit 44.
Once the purging operation has been completed, the valve 34 is operated to connect the conduit 44 to the conduit 38 which connects to the pressure-reducing regulator 39, which facilitates ~L 2~7 ~ 3à~
controlled withdrawal of only a relatively small amount of gas from the electrical apparatus undergoing test, and permits gas to be flowed through the detector tu~e 21 at a relatively low and substantially uniform flow rate, so that the quantity of gas passed through the tube can be at least approximately metered by control of the time for which the flow is permitted to continue.
This can permit at least approximately quantitative measurement of the content of SO2 in the fill gas. Commonly, the SF6 gas in the electrical apparatus is at a fill pressure between about ~5 and about 8 atmospheres, more usually about 3.5 atmospheres.
Advantaqeously, the pressure regulator 39 provides at its outlet 40 a flow at a reduced pressure which provides through the detec-tor tube 21 a gas flow at a rate of about 0.1 to about 1 l/min, more preferably about 130 to 600 ml/min. This rate of flow is sufficiently low that an at least approximately measured volume of gas can be passed by timing the gas flow, while the rate of flow is sufficient that, within a conveniently short period of a few minutes, or less, a sufficient volume of gas can be passed through the detector tube to provide a visually perceptible color change in the detector material present in the tube. Usually, the pressure regulator 39 will provide at its outlet a pressure which is just slightly above normal atmospheric pressure.
Normally, the pressure regulater is pre set and the flow meter 42 is used merely to verify that the proper flow is being maintained during the course of the test.
In the preferred form, the detector tube is a length of stain SO2 detector tube, i.e. a tube which provides a change in color, or a stain, from its end adjacent the gas inlet, and for a distance extending along the tube which is dependent upon the absolute quantity of SO2 gas which has been passed through the tube.
Thus, where the volume of gas passed through the tube is known, the concentration of SO2 in the gas can be determined by measuring the length of the stain within the detector tube. In the preferred form, the wall of each tube is provided with a scale 46, which permits the length of the stain to be measured by direct observation.
.~ - 8 - ~ ~7~ .
In this case, the test is conducted by permitting gas to flow through the tube 21 under control of the valve 34 for a predeter-mined time, sufficient to pass a predetermined volume of gas through the tube 21. The test is then terminated by closing the valve 34, and reading off, on the scale 46, the length of the stain which appears in the tube 21. This c~n provide an at least approximately quantitative indication of the concentration of SO2 in the fill gas, and can provide an indication of a fault causing an electrical discharge through the fill gas.
In order to avoid exposing those carrying out the test to toxic decomposition products, a discharge conduit 47 may be connected ; to the connector 43 of the outlet conduit 41, to divert the gases a safe distance away from the apparatus. Similarly, the connector 37 of the vent conduit 36 may be connected to a like discharge conduit, or, through a branch fitting, to the discharge conduit 47.
In the preferred form, the length of stain detector tubes are sufficiently sensitive that they will provide a perceptible color change indication when less than about 100 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed through them, at a temperature of 20C and at a : pressure of 760 mm ~g. If the tube is significantly lesS: sensitive, conducting the test will tend to require withdrawal from the electrical apparatus an excessively large ~uantity of the SF6 fill gas, since, under typical fault conditions such as produce a power arc in the gas-filled apparatus, the fill gas will contain about 30 to about 1000 ppm of SO2. Thus, in order to provide a sample of gas at 20C and 1 atmosphere pressure con-taining 100 microlitres of SO2, it would be necessary to withdraw about 3 litres of fill gas at 20C and 1 atmosphere pressure, if the fill gas contains 30 ppm SO2, or about 0.1 litres if the gas contains 1000 ppm. These correspond to withdrawals of gas of about 0.75 litres or about 0.025 litres, respectively, at 20C
and 4 atmospheres (system) pressure, in the event that the elec-trical apparatus contains SF6 gas at a system or Eill pressure ofabout 4 atmospheres. More preferably, the detector tube provides - - 9 - ~
a perceptible color change indication when less than about 30 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed therethrough at 20C and 760 mm Hg.
As one form of detector tube suitable for ~se in the present invention may be mentioned the sulfur dioxide length of stain detector tubes available under the trade mark KITAGAWA from Matheson Gas Products Canada Inc., Whitby, Ontario, Canada LlN 5R9. These tubes contain a blue-colored reagent which, on passage of gas containing SO2 therethrough become stained white.
It has been found that when gaseous SF6 decomposition products containing a certain volume of S~2 are passed throu~h the tube, the detector material becomes stained for a distance along its length which is greater than that which would be obtained on passing the same volume of SO2 through the tube in a mixture with air or other gas inert with respect to the detector material.
Without wishing to be bound by any theory, it is suggested that the reducible detector material present in the KITAGAWA tubes is additionally reactive toward some decomposition product of SF6 other than SO2, or that the detector material in the KITAGAWA
tubes promotes decomposition of SOF2, or some other SF6 decomposition product, to yield further quantities of SO2.
To the best of applicant's information, the KITAGAWA tubes con-tain as the active ingredient, or reducible material, a ~4-~p-(dimethylamino)phenyl methylene]-2,5-cyclohexadien-1-ylidine~-N-methylmethanaminium salt, which is blue-coloured. On reduction with SO2j this undergoes reduction to tetramethyldiaminodiphenyl-methane, which is white. The active ingredient is dispersed on a granular inert diluent, for example powdered silica. As far as applicants are aware, the KITAGAWA tubes have been used up to the present time for detection of sulfur dioxide as an atmospheric pollutant in samples of air. United States Patent 2,736,638 dated February 28, 1956 in the na~e P.Wq McConnaughey describes a method for determining the presence of sulfur dioxide in gases, particularly air, employing the blue reaction product of tetra-methyldiaminodiphenylmethane and an oxidizing agent, which 1 - ~25~
product ~pon contact with sulfur dioxide is bleached to white.
According to applicant's information, the blue reaction product is a [4-[p-(dimethylamino)phenylmethylene]-2,5 cyclohexadien-1-ylidine]-N-methylmethanaminium salt, which, according to applicant's information, is employed in the KITAGAWA tubes~
The invention in its broadest embodiments is, however, by no means limited to the use of the KITAGAWA tubes, or to the use of the blue-colored reducible detector material employed therein.
Generally, there may be employed any chemically-reducible detec-tor material known to those skilled in the art which provides acolor change when chemically reduced on contact with SO2.
Apart from the types of electrical fault which result in a power arc within the apparatus, electrical apparatus insulated with a fill of SF6 gas is subject to a form of fault known as "partial discharge". Typically, a partial discharge fault will result in the presence of contents of sulfur dioxide in the gas fill in concentrations of less than 1 to about 30 ppm. In the use of the apparatus for detection of partial discharge faults, it is desirable to employ a lenqth of stain detector tube which provides a perceptible color change indication when less than about 10 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed therethrough at 20C and 760 mm Hg, more preferably less than about 1 microlitre of SO~
contained in said volume and at said temperature and pressure.
One form of the above-mentioned KITAGAWA tubes preferred for use in the present invention, particularly for use in detection of power arc faults, comprise the KITAGAWA tubes Type 103 Sc. These tubes are adapted to measure sulfur dioxide in a concentration of from a minimum of about 20 ppm to a maximum of about 300 ppm when 100 ml of SO2-containing gas at 20C and 760 mm Hg are passed through the tubeO A further form of the above-mentioned KITAGAWA
tubes preferred for use in the present apparatusl particularly for use in detection of partial discharges, comprise Type 103 Sd tubes, which are adapted to measure concentrations of SO2 ranging from a minimum of about 1 ppm to a maximum of about 30 ppm when 57~
300 ml of SO2-containing gas at 20C and 760 mm Hg are passed through the tube.
In one form of the present apparatus, instead of flowing the gas through one of the detector tubes, for example the detector tube 21, and employing the other tube, t9, as a reference tube and as an obturator, one of the tubes may be a detector tube selected to indicate the presence o~ relatively high concentrations of SO2, such as result ~rom a power arc fault in the electrical appara-tus, while the other may be selected to indicate the presence of a relatively low content of SO2 in the gas) such as is obtained in the presence of a partial discharge in the electrical equip-ment, e.g. one tube may be a KITAGAWA 103 Sd tube and the other a K~TAGAWA 103 Sc tube. In such case, the above-described testing procedure would be followed, except that the ends of both tubes would be broken and the broken-ended tubes would be clamped in the apparatus before starting the test.
Figure 2 shows schematically an alternative form of detector apparatus, which may be particularly useful for detection of partial discharge faults in live, energised electrical apparatus, where it is desired to minimize the time for which the detector apparatus is hooked up to the live equipment. In Figure 2, like reference numerals indicate parts similar to those employed in the apparatus of Figure 1. In the apparatus of Figure 2, the inlet conduit 33 connects to a two-position valve 51 which is connected through a tee conduit 52 to a gas reservoir 53 and to a two-way valve 54. The valve 54 is connected through a conduit 56 to the pressure regulator 39, which connects through a conduit 40 and flow meter 42 to the detector tubes 19 and 21. The opposite ends of the detector tubes 19 and 21 are connected through a tee conduit 57 to the suction side of a vacuum pump 58 and to a two-position valve 59. The valve 59 is connected through a conduit 61 to the gas reservoir 53.
In operation, the connector 32 is connected through a lengthy conduit 44 to a connector on a valve, such as the valve 16, initially closed, on a port, such as the port 14, of a gas-filled ~5~
apparatus to be tested. With the valves 51 and 59 open, the vacuum pump 5~ is operated to evacuate the gas reservoir 53 and the conduits connected thereto, including the conduit 44 extending to the valve 16. The valve 59 is then closed, and the valve on the apparatus, for example the valve 16, is then opened, and the valve 51 is opened, so that the pressllre of gas in the gas-filled apparatus forces the SF6 fill gas into the evacuated gas reservoir 53. Typically, the gas reservoir 53 will have a capacity of about 0.5 to about 1 litres, in order to collect sufficient of the fill gas, at approximately the pressure of the gas filling of the apparatus (typically between 1.5 and 8 atmospheres) to permit detection of the SO2 content thereof. The valve 51 is then closed, and the valve 16 on the port of the gas-filled apparatus is then closed. The conduit 44 may then be disconnected from the electrical apparatus, and the remainder of the detection procedure may be conducted without having the detector apparatus hooked up to the electrical apparatus.
In order to conduct the test, the valve 54 is opened and the pump 58 is operated so that gas is passed from the reservoir 53, through the regulator 39, and through the tubes 19 and 21, or through one of them, the gas being dischar~ed from the positive pressure side of the pump 58. As before, the valve 54 may be opened for a measured period, so that a predetermined volume of gas is passed through the tube or tubes 19 and 21, at constant, known pressure, whereby a repeatable or quantitative result is obtainedO
Although it is believed that the above description provides ample information to permit one skilled in the art to carry out the present detection method, for the avoidance of doubt, a detailed example will be given.
Example A fill of SF6 gas was maintained in an arcing chamber. The fill gas was subjected to a high current power arc at a level of energy per unit volume as indicated in Table 1, below. ProviSion _ 13 _ ~ ~57~ 8~
was made to sample the arced gas, and part of the sample was subjected to conventional gas chromatography/mass spectrometry analysis, to determine its contents of SO2, S~F2 and SO2F2.
A further porti~n of the arced gas was subjected to a detection procedure, using the apparatus as described above in detail with reference to Figure 1 of the drawings. The tuhe 21 was a KITAGAWA length of stain detector tube Type 103 Sc, having a measuring range of 20 to 300 ppm sulfur dioxide in 100 ml of gas at 20~C and 700 mm Hg. The arced gas was flowed through the detector tube 21 for a timed period under a low pressure and at a fixed, predetermined flow rate regulated by the pressure regulator 39. The quantity of gas passed in 20 seconds ~as such that a reading of 300 ppm on the KITAGAWA tube corresponded to an actual content of SO2 of 1000 ppm. Thus, 30 ml of the arced gas, measured at 20C and 760 mm Hg, was passed through the tube.
The procedure was repeated using high voltage sparks instead of the high current arc, simulating a partial discharge. The detector tube was a Type 103 5d KITAGAWA tube, having a normal measuring range of 1 to 30 ppm S2 in 300 ml of gas. The arced gas was passed through the tube for a timed period so as to pass 300 ml of gas through the tube, measured at 20C and 760 mm ~g, so that the readings from graduations on the tube corresponded to the actual content of SO2.
The energy expended in the arcs, per unit volume of the fill gas, and the concentrations of various gaseous decomposition products, as measured by conventional gas analysis, and as by the detector in accordance with the invention, are indicated in Table 1 below.
- 14 - ~ ~57~8~
. .. _ . . _ _ pp~ measured by gas chromatography/
mass spectrometry ppm measured Arc Energy per Unit ----I . by detector of conditions Volume kJ/L SO2 SOF2 S2F2 the invention _ _ _ _ _ . _ ._ Power Arc _ 22s 2700 11 980 Sparks 0.1 3 2 2 _ _ , - .. _ The results obtained with the high current arc indicate that the quantity of SO2 as measured by the detector device is elevated as compared with the actual SO2 eontent, possibly for the reasons discussed above.
The results show that, at both high and low concentrations of SO2, the deteetor in aecordanee with the invention shows a broad range of applicability for detection of SF6 decomposition products indicative of arcing faults within the gas insulated apparatus.
There are also known fault detector devices which comprise an indicator responsive to changes in p~l. The gaseous decomposition products of arced SF6 include acids such as HF. Thus, passa~e of the insulatin~ fill gas through a basified pH indicator contain-in~ a certain amount of moisture can provide a color change inresponse to a pH change from basic to neutral or acidic, indica-tive of the presence of aci~ic decomposition products. The acid dissolves to form an acid solution which effects the color change of the indicator. These devices are relatively small and inexpensive, but the solutions resulting from contact of the arced gas with moisture are only very weak solutions and so the detection method is not sensitive. The devices of which the in-ventors are aware have poor sensitivity and require large volumes of usually 10 to 30 litres of arced gas to be withdrawn from the apparatus and passed to the indicator before a readily percep-tible color chanqe takes place. This necessitates long hook up times to the apparatus, and renders the test device inapplicable to the testing oE relatively small gas-filled compartments.
Withdrawal of large volumes of gas can deplete the gas fill to such an extent that the insulative property is impaired and a fault is thereby induced in the apparatus undergoing test.
A quicker and simpler way of locatiny a fault is to sniff the insulating gas, since the decomposition products have a distinctive odor. This practice is highly undesirable, since the decomposition products are toxic.
The present inventors have found that SF6 insulation gas fills, when exposed to a fault, provide, along with other products, a substantial concentration of sulfur dioxide (SO2), whereas SO2 is substantially completely absent from SF6 gas which is not exposed to a fault, and, on the basis of the observation that SO2 is a powerful reducinq agent, have found that the presence o~ SF6 decomposition products indicative of exposure of the SF6 to fault conditions can be readily determined employing a chemically-reduci~le detector material which provides a color change on chemical reduction on exposure to SO2. Accordingly the present invention provides a metho~ of detecting decomposition of an SF6 _ 3 - ~2~7~
~as filling in gas-insulated electrical apparatus comprising withdrawing gas from the apparatus, contacting it with a chemically-reducible detector material which is chemically reduced and changes color on contact with SO2, and observing the color chanqe of the detector material.
Without wishing to be bound by any theory, to the best of applicant's understandingl when an arc passes through SF6 gas in SF6 gas insulated electrical apparatus, a number of gaseous and solid by-products are formed, reflecting the materials, such as conductors and insulator materials which are adjacent to and are effected by the arc. It appears that SOF2 and SO2F2 are the most abundant hy-products formed. On contact with moisture SO2F2 remains stable~ However, for SOF2, a further breakdown occurs:
SOF2 + H2O ~ SO2 ~ 2HF
It appears that sufficient moisture is present, even in the dry industrial grafles of SF6, having a dew point of -40C, to permit for~ation of SOF2 and its conversion, under appropriate conditions, to SO2 in quantities adequate to permit detection of the occurrence of the arc through detection of the SO2 formed thereby.
In view of the relatively powerful properties of SO2 as a reducing agentr and the only relatively weakly acidic nature of solutions formed from dissolution of the arced gas, the chemically-reducible detector system offers much greater sensitivity than the pH indicator-based arrangements.
Thus, the chemically-reducible detector material is much more sensitive to small concentrations of SO2 than the pH indicator materials are toward the acid components of correspondingly decomposed SF6 gas fills, and therefore requires much smaller withdrawals of insulating gas and shorter hook up times, and the detection procedure can be carried out more quickly. It has been found that, surprisingly, and for reasons which are presently not fully understood, the preferre~ so2-reducible detector material ~.25'7~
has much greater sensitivity toward SF6 decomposition products than toward gas mixtures containing SO2 as the only reactive com-ponent. The material is thus outstandingly useful for detecting SF6 decomposition products caused by electrical discharge and for location of electrical discharge faults in complex and ex~ensive SF6-insulated systems.
In one aspect, the invention provides a gas decomposition detector for SF6 gas-insulated electrical apparatus, comprising a pressure-reducing gas pressure regulator, having an inlet for connection to the electrical apparatus and an outlèt for providing a relatively reduced pressure flow, and connected to a detector tube containing a chemically-reducible detector material providing a color change when chemically reduced on contact with S2 present in the gas passed therethrough.
Further advantages and preferred features oE the present detector and method are described hereinafter with reference to the accompanying drawings which show, by way of example only, preferred embodiments of the present invention.
Figure 1 shows partially schematically one form of gas decompo-sition detector apparatus in accordance with the invention.
Figure 2 shows schematically a second form of detector apparatus in accordance with the invention.
~eferring to Figure 1, this shows a detector device employed for detecting SF6 gas decomposition in apparatus which in this instance is an insulated bus comprising a conductor 10, enclosed in a metal casing 11. The casing 11 is compartmentalised in gas-tight fashion by insulating spacers 12 which define between them an SF6 gas-filled compartment 13. The interior of this compartment is accessible, for gas-filling or testing purposes, through a port 14, controlled by a valve 16~ The port 14 is provided with a standard connector 17 with which other standard connectors may be engaged.
~257~
In the preferred form, the detector device is a relatively small, portable device which has its components ~ounted within a hous-ing, indicated schematically in broken lines by the rectangle 13.
The detector device comprises two glass tubes 19 and 21, each containing a chemically-reducible detector material which under-goes a color change on chemical reduction on contact with SO2.
Each tube is supported at its opposite ends in connector blocks 22 and 23, and each connector block has inset in it a pair of resilient plugs 24, each formed with a central bore. Each end of each tube 19 and 21 has a tapering tip which is cushioned and located by the bore through the plug 24. The block 23 at one end is fixed to one end of a rod 26. The block 22 at the other end is slidable longitudinally on the rod 26, which is threaded in this region, and, above the block 22, the rod 26 has threaded on it a collar 27. The collar 27 can be unscrewed to permit the tubes 19 and 21 to be disengaged from the plugs 24, and removed or replaced. On tightening up the collar 27, the peripheries of the tapered ends of the tubes 19 ar1d 21 are urged firmly into positivet sealingl location within the central bores in the plugs 24. A transverse bore 28 passes through the block 22, and similarly a transverse bore 29 passes through the block 23~
Longitudinal bores 31 connect with each transverse bore 28 and 29 and to the interior bore through the plugs 24.
The device further includes a connector 32 connecting through a conduit 33 to a three-position valve 34. Connected to the valve 34 is a vent conduit 36, provided at the opposite end with a con-nector 37. The valve 34 also connects with a main conduit 38 which passes to a pressure~reducing pressure regulator 39. By operation of the three-way valve 34, the conduit 33 can be connected selectively to the vent conduit 36 or to the inlet of the pressure regulator 39. In a third position, the valve 34 closes the conduit 33, and the conduits 36 and 38. The outlet of the pressure regulator 39 connects through a conduit 40 to the transverse bore 28 in the connector block 22. The trans~erse bore 29 in the connector block 23 is connected to an outlet conduit 41 and through a gas flow meter 42 to a connector 43.
~ ~7 ~
In use, one of the detector tubes, e.g. the tube 13, may act as a color-comparison standard or reference, and the gas is passed through only the other tube 21. In the preferre~ form, the detector tubes 19 and 21 are supplied in a sealed condition which protects the detector material inside from contact with S2 which may be present in the ambient atmosphere. Before performing the test, it is necessary to remove the tube 21 from the detector device, and to open the ends of the tube by breaking off its glass tips in a conventional form of tip-breaking device. The opened tube 21 is then replaced between the connect~r blocks 22 and 23, as shown, so that its interior is in communication with the bores through the connector blocks 22 and 23, and the plugs 24, and hence also with the conduits 40 and 41. The intact tapering glass tips of the other tube 19, which remains sealed, serve as obturators closing the bores in the plugs 24 in which the tube 19 is received.
The detector device may in use be positioned adjacent to or may be spaced remotely from the electrical apparatus which is to undergo test. In a typical example, the bus 11 as illustrated may be situa~ed some 2 or 3 meters above ground level, and it will be convenient to place the detector device on or adjacent the ground. In order to conduct the test, it is therefore necessary to connect the connector 17 on the bus 11 to the connector 3~ on the detector device using a lengthy flexible conduit 44. Before conducting the test, air needs to be purged from the conduit 44 so that air or air-diluted fill gas is not passed to the tube 21, which could lead to a false result being obtained. The three-way valve 34 is initially in the position closing the conduit 33. The valve 16 on the bus is opened, and then the valve 34 is operated to connect the conduit 44 to the vent conduit 36, to release gas from the compartment 13 through the vent conduit 36 for a brief period sufficient to purge substantially all air from the conduit 44.
Once the purging operation has been completed, the valve 34 is operated to connect the conduit 44 to the conduit 38 which connects to the pressure-reducing regulator 39, which facilitates ~L 2~7 ~ 3à~
controlled withdrawal of only a relatively small amount of gas from the electrical apparatus undergoing test, and permits gas to be flowed through the detector tu~e 21 at a relatively low and substantially uniform flow rate, so that the quantity of gas passed through the tube can be at least approximately metered by control of the time for which the flow is permitted to continue.
This can permit at least approximately quantitative measurement of the content of SO2 in the fill gas. Commonly, the SF6 gas in the electrical apparatus is at a fill pressure between about ~5 and about 8 atmospheres, more usually about 3.5 atmospheres.
Advantaqeously, the pressure regulator 39 provides at its outlet 40 a flow at a reduced pressure which provides through the detec-tor tube 21 a gas flow at a rate of about 0.1 to about 1 l/min, more preferably about 130 to 600 ml/min. This rate of flow is sufficiently low that an at least approximately measured volume of gas can be passed by timing the gas flow, while the rate of flow is sufficient that, within a conveniently short period of a few minutes, or less, a sufficient volume of gas can be passed through the detector tube to provide a visually perceptible color change in the detector material present in the tube. Usually, the pressure regulator 39 will provide at its outlet a pressure which is just slightly above normal atmospheric pressure.
Normally, the pressure regulater is pre set and the flow meter 42 is used merely to verify that the proper flow is being maintained during the course of the test.
In the preferred form, the detector tube is a length of stain SO2 detector tube, i.e. a tube which provides a change in color, or a stain, from its end adjacent the gas inlet, and for a distance extending along the tube which is dependent upon the absolute quantity of SO2 gas which has been passed through the tube.
Thus, where the volume of gas passed through the tube is known, the concentration of SO2 in the gas can be determined by measuring the length of the stain within the detector tube. In the preferred form, the wall of each tube is provided with a scale 46, which permits the length of the stain to be measured by direct observation.
.~ - 8 - ~ ~7~ .
In this case, the test is conducted by permitting gas to flow through the tube 21 under control of the valve 34 for a predeter-mined time, sufficient to pass a predetermined volume of gas through the tube 21. The test is then terminated by closing the valve 34, and reading off, on the scale 46, the length of the stain which appears in the tube 21. This c~n provide an at least approximately quantitative indication of the concentration of SO2 in the fill gas, and can provide an indication of a fault causing an electrical discharge through the fill gas.
In order to avoid exposing those carrying out the test to toxic decomposition products, a discharge conduit 47 may be connected ; to the connector 43 of the outlet conduit 41, to divert the gases a safe distance away from the apparatus. Similarly, the connector 37 of the vent conduit 36 may be connected to a like discharge conduit, or, through a branch fitting, to the discharge conduit 47.
In the preferred form, the length of stain detector tubes are sufficiently sensitive that they will provide a perceptible color change indication when less than about 100 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed through them, at a temperature of 20C and at a : pressure of 760 mm ~g. If the tube is significantly lesS: sensitive, conducting the test will tend to require withdrawal from the electrical apparatus an excessively large ~uantity of the SF6 fill gas, since, under typical fault conditions such as produce a power arc in the gas-filled apparatus, the fill gas will contain about 30 to about 1000 ppm of SO2. Thus, in order to provide a sample of gas at 20C and 1 atmosphere pressure con-taining 100 microlitres of SO2, it would be necessary to withdraw about 3 litres of fill gas at 20C and 1 atmosphere pressure, if the fill gas contains 30 ppm SO2, or about 0.1 litres if the gas contains 1000 ppm. These correspond to withdrawals of gas of about 0.75 litres or about 0.025 litres, respectively, at 20C
and 4 atmospheres (system) pressure, in the event that the elec-trical apparatus contains SF6 gas at a system or Eill pressure ofabout 4 atmospheres. More preferably, the detector tube provides - - 9 - ~
a perceptible color change indication when less than about 30 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed therethrough at 20C and 760 mm Hg.
As one form of detector tube suitable for ~se in the present invention may be mentioned the sulfur dioxide length of stain detector tubes available under the trade mark KITAGAWA from Matheson Gas Products Canada Inc., Whitby, Ontario, Canada LlN 5R9. These tubes contain a blue-colored reagent which, on passage of gas containing SO2 therethrough become stained white.
It has been found that when gaseous SF6 decomposition products containing a certain volume of S~2 are passed throu~h the tube, the detector material becomes stained for a distance along its length which is greater than that which would be obtained on passing the same volume of SO2 through the tube in a mixture with air or other gas inert with respect to the detector material.
Without wishing to be bound by any theory, it is suggested that the reducible detector material present in the KITAGAWA tubes is additionally reactive toward some decomposition product of SF6 other than SO2, or that the detector material in the KITAGAWA
tubes promotes decomposition of SOF2, or some other SF6 decomposition product, to yield further quantities of SO2.
To the best of applicant's information, the KITAGAWA tubes con-tain as the active ingredient, or reducible material, a ~4-~p-(dimethylamino)phenyl methylene]-2,5-cyclohexadien-1-ylidine~-N-methylmethanaminium salt, which is blue-coloured. On reduction with SO2j this undergoes reduction to tetramethyldiaminodiphenyl-methane, which is white. The active ingredient is dispersed on a granular inert diluent, for example powdered silica. As far as applicants are aware, the KITAGAWA tubes have been used up to the present time for detection of sulfur dioxide as an atmospheric pollutant in samples of air. United States Patent 2,736,638 dated February 28, 1956 in the na~e P.Wq McConnaughey describes a method for determining the presence of sulfur dioxide in gases, particularly air, employing the blue reaction product of tetra-methyldiaminodiphenylmethane and an oxidizing agent, which 1 - ~25~
product ~pon contact with sulfur dioxide is bleached to white.
According to applicant's information, the blue reaction product is a [4-[p-(dimethylamino)phenylmethylene]-2,5 cyclohexadien-1-ylidine]-N-methylmethanaminium salt, which, according to applicant's information, is employed in the KITAGAWA tubes~
The invention in its broadest embodiments is, however, by no means limited to the use of the KITAGAWA tubes, or to the use of the blue-colored reducible detector material employed therein.
Generally, there may be employed any chemically-reducible detec-tor material known to those skilled in the art which provides acolor change when chemically reduced on contact with SO2.
Apart from the types of electrical fault which result in a power arc within the apparatus, electrical apparatus insulated with a fill of SF6 gas is subject to a form of fault known as "partial discharge". Typically, a partial discharge fault will result in the presence of contents of sulfur dioxide in the gas fill in concentrations of less than 1 to about 30 ppm. In the use of the apparatus for detection of partial discharge faults, it is desirable to employ a lenqth of stain detector tube which provides a perceptible color change indication when less than about 10 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed therethrough at 20C and 760 mm Hg, more preferably less than about 1 microlitre of SO~
contained in said volume and at said temperature and pressure.
One form of the above-mentioned KITAGAWA tubes preferred for use in the present invention, particularly for use in detection of power arc faults, comprise the KITAGAWA tubes Type 103 Sc. These tubes are adapted to measure sulfur dioxide in a concentration of from a minimum of about 20 ppm to a maximum of about 300 ppm when 100 ml of SO2-containing gas at 20C and 760 mm Hg are passed through the tubeO A further form of the above-mentioned KITAGAWA
tubes preferred for use in the present apparatusl particularly for use in detection of partial discharges, comprise Type 103 Sd tubes, which are adapted to measure concentrations of SO2 ranging from a minimum of about 1 ppm to a maximum of about 30 ppm when 57~
300 ml of SO2-containing gas at 20C and 760 mm Hg are passed through the tube.
In one form of the present apparatus, instead of flowing the gas through one of the detector tubes, for example the detector tube 21, and employing the other tube, t9, as a reference tube and as an obturator, one of the tubes may be a detector tube selected to indicate the presence o~ relatively high concentrations of SO2, such as result ~rom a power arc fault in the electrical appara-tus, while the other may be selected to indicate the presence of a relatively low content of SO2 in the gas) such as is obtained in the presence of a partial discharge in the electrical equip-ment, e.g. one tube may be a KITAGAWA 103 Sd tube and the other a K~TAGAWA 103 Sc tube. In such case, the above-described testing procedure would be followed, except that the ends of both tubes would be broken and the broken-ended tubes would be clamped in the apparatus before starting the test.
Figure 2 shows schematically an alternative form of detector apparatus, which may be particularly useful for detection of partial discharge faults in live, energised electrical apparatus, where it is desired to minimize the time for which the detector apparatus is hooked up to the live equipment. In Figure 2, like reference numerals indicate parts similar to those employed in the apparatus of Figure 1. In the apparatus of Figure 2, the inlet conduit 33 connects to a two-position valve 51 which is connected through a tee conduit 52 to a gas reservoir 53 and to a two-way valve 54. The valve 54 is connected through a conduit 56 to the pressure regulator 39, which connects through a conduit 40 and flow meter 42 to the detector tubes 19 and 21. The opposite ends of the detector tubes 19 and 21 are connected through a tee conduit 57 to the suction side of a vacuum pump 58 and to a two-position valve 59. The valve 59 is connected through a conduit 61 to the gas reservoir 53.
In operation, the connector 32 is connected through a lengthy conduit 44 to a connector on a valve, such as the valve 16, initially closed, on a port, such as the port 14, of a gas-filled ~5~
apparatus to be tested. With the valves 51 and 59 open, the vacuum pump 5~ is operated to evacuate the gas reservoir 53 and the conduits connected thereto, including the conduit 44 extending to the valve 16. The valve 59 is then closed, and the valve on the apparatus, for example the valve 16, is then opened, and the valve 51 is opened, so that the pressllre of gas in the gas-filled apparatus forces the SF6 fill gas into the evacuated gas reservoir 53. Typically, the gas reservoir 53 will have a capacity of about 0.5 to about 1 litres, in order to collect sufficient of the fill gas, at approximately the pressure of the gas filling of the apparatus (typically between 1.5 and 8 atmospheres) to permit detection of the SO2 content thereof. The valve 51 is then closed, and the valve 16 on the port of the gas-filled apparatus is then closed. The conduit 44 may then be disconnected from the electrical apparatus, and the remainder of the detection procedure may be conducted without having the detector apparatus hooked up to the electrical apparatus.
In order to conduct the test, the valve 54 is opened and the pump 58 is operated so that gas is passed from the reservoir 53, through the regulator 39, and through the tubes 19 and 21, or through one of them, the gas being dischar~ed from the positive pressure side of the pump 58. As before, the valve 54 may be opened for a measured period, so that a predetermined volume of gas is passed through the tube or tubes 19 and 21, at constant, known pressure, whereby a repeatable or quantitative result is obtainedO
Although it is believed that the above description provides ample information to permit one skilled in the art to carry out the present detection method, for the avoidance of doubt, a detailed example will be given.
Example A fill of SF6 gas was maintained in an arcing chamber. The fill gas was subjected to a high current power arc at a level of energy per unit volume as indicated in Table 1, below. ProviSion _ 13 _ ~ ~57~ 8~
was made to sample the arced gas, and part of the sample was subjected to conventional gas chromatography/mass spectrometry analysis, to determine its contents of SO2, S~F2 and SO2F2.
A further porti~n of the arced gas was subjected to a detection procedure, using the apparatus as described above in detail with reference to Figure 1 of the drawings. The tuhe 21 was a KITAGAWA length of stain detector tube Type 103 Sc, having a measuring range of 20 to 300 ppm sulfur dioxide in 100 ml of gas at 20~C and 700 mm Hg. The arced gas was flowed through the detector tube 21 for a timed period under a low pressure and at a fixed, predetermined flow rate regulated by the pressure regulator 39. The quantity of gas passed in 20 seconds ~as such that a reading of 300 ppm on the KITAGAWA tube corresponded to an actual content of SO2 of 1000 ppm. Thus, 30 ml of the arced gas, measured at 20C and 760 mm Hg, was passed through the tube.
The procedure was repeated using high voltage sparks instead of the high current arc, simulating a partial discharge. The detector tube was a Type 103 5d KITAGAWA tube, having a normal measuring range of 1 to 30 ppm S2 in 300 ml of gas. The arced gas was passed through the tube for a timed period so as to pass 300 ml of gas through the tube, measured at 20C and 760 mm ~g, so that the readings from graduations on the tube corresponded to the actual content of SO2.
The energy expended in the arcs, per unit volume of the fill gas, and the concentrations of various gaseous decomposition products, as measured by conventional gas analysis, and as by the detector in accordance with the invention, are indicated in Table 1 below.
- 14 - ~ ~57~8~
. .. _ . . _ _ pp~ measured by gas chromatography/
mass spectrometry ppm measured Arc Energy per Unit ----I . by detector of conditions Volume kJ/L SO2 SOF2 S2F2 the invention _ _ _ _ _ . _ ._ Power Arc _ 22s 2700 11 980 Sparks 0.1 3 2 2 _ _ , - .. _ The results obtained with the high current arc indicate that the quantity of SO2 as measured by the detector device is elevated as compared with the actual SO2 eontent, possibly for the reasons discussed above.
The results show that, at both high and low concentrations of SO2, the deteetor in aecordanee with the invention shows a broad range of applicability for detection of SF6 decomposition products indicative of arcing faults within the gas insulated apparatus.
Claims (20)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A gas decomposition detector for electrical apparatus insulated with a fill of SF6 gas at relatively high pressure, comprising a pressure-reducing gas pressure regulator having an inlet for connection to the electrical apparatus, and an outlet providing a relatively reduced pressure flow and connected to a detector tube containing a chemically-reducible detector material providing a color change when chemically reduced on contact with SO2 present in the gas passed therethrough.
2. A detector as claimed in claim 1 wherein the tube comprises a length of stain detector tube providing a perceptible color change indication when less than about 100 microlitres of SO2, contained in as little as about 1 litre of SO2-containing gas, are passed therethrough at 20°C and 760 mm Hg.
3. A detector as claimed in claim 2 wherein said quantity of SO2, contained in as little as about 1 litre of SO2-containing gas, is less than about 30 microlitres.
4. A detector as claimed in claim 3 wherein said quantity is less than about 10 microlitres.
5. A detector as claimed in claim 4 wherein said quantity is about 1 microlitre.
6. A detector as claimed in claim 2 wherein the tube is a KITAGAWA (trade mark) tube.
7. A detector as claimed in claim 1 wherein the detector material comprises a [4-[p-(dimethylamino)phenylmethylene]-2,5-cyclohexadien-1-ylidine]-N-methylmethanaminium salt.
8. A detector as claimed in claim 1 wherein the pressure regulator provides at its outlet a reduced pressure of gas adapted to pass a flow about 0.1 to 1 1/min of gas through the detector tube.
9. A detector as claimed in claim 8 wherein said flow is about 130 to 600 ml/min.
10. A detector as claimed in claim 1 comprising a vent conduit, a gas inlet, and, connected between the gas inlet, the pressure regulator and said vent conduit, valve means for connecting the gas inlet selectively to the vent conduit or to the pressure regulator.
11. A detector as claimed in claim 1 comprising a gas reservoir which is connected through a valve means to the suction side of a vacuum pump, and through a further valve means to the inlet to the pressure regulator, the suction side of said vacuum pump also being connected to an end of the detector tube opposite an end thereof connected to the pressure regulator.
12. A detector as claimed in claim 1 comprising a second detector tube disposed adjacent and parallel to the first mentioned tube.
13. A detector as claimed in claim 11 including a connection between the outlet of the pressure regulator and the second tube whereby gas can be passed through both tubes.
14. A detector as claimed in claim 11 including a connection between the outlet of the pressure regulator and the second tube whereby gas can be passed through both tubes.
15. A method of detecting decomposition of an SF6 gas filling in gas-insulated electrical apparatus comprising withdrawing gas from the apparatus, contacting it with a chemically-reducible detector material which is chemically reduced and changes color on contact with SO2, and observing the color change of the detector material.
16. A method as claimed in claim 15 wherein the detector material is present in a length of stain detector tube providing a measurable color change when less than about 100 microliters of SO2 are passed therethrough at 20°C and 760 mm Hg.
17. A method as claimed in claim 16 wherein the tube is a KITAGAWA (trade mark) tube.
18. A method as claimed in claim 15 comprising connecting a supply conduit to the electrical apparatus, flowing gas from the electrical apparatus through the supply conduit to purge air therefrom, connecting the purged supply conduit to the detector tube, and flowing gas from the purged supply conduit through the detector tube.
19. A method as claimed in claim 15 comprising evacuating a gas reservoir with a vacuum pump, connecting the evacuated reservoir to the electrical apparatus, filling the reservoir with gas from the electrical apparatus, disconnecting the filled reservoir from the electrical apparatus and connecting it to one end of a tube containing said detector material, connecting the opposite end of the tube to the vacuum pump and drawing gas from the reservoir through the tube.
20. A method as claimed in claim 15 wherein the detector material comprises a [4-[p-(dimethylamino)phenylmethylene]-2,5-cyclohexadien-1-ylidine]-N-methylmethanaminium salt.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000490129A CA1257185A (en) | 1985-09-06 | 1985-09-06 | Gas decomposition detector for gas-insulated electrical apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000490129A CA1257185A (en) | 1985-09-06 | 1985-09-06 | Gas decomposition detector for gas-insulated electrical apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1257185A true CA1257185A (en) | 1989-07-11 |
Family
ID=4131327
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000490129A Expired CA1257185A (en) | 1985-09-06 | 1985-09-06 | Gas decomposition detector for gas-insulated electrical apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1257185A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5075544A (en) * | 1989-11-24 | 1991-12-24 | Mitsubishi Denki Kabushiki Kaisha | Optical color change device for detecting electrical abnormality |
| DE4133947A1 (en) * | 1991-10-14 | 1993-04-15 | Asea Brown Boveri | Sensor for decomposition prod. of insulating gas pref. sulphur hexa:fluoride - comprises indicator composed of composite material including a filler in matrix which is chemically inert and permeable to prods. |
| US6126732A (en) * | 1993-06-24 | 2000-10-03 | Dentsply Detrey Gmbh | Dental prosthesis |
| CN108007925A (en) * | 2017-11-16 | 2018-05-08 | 国网福建省电力有限公司泉州供电公司 | SF6Gas decomposition product colorimetric determination instrument |
| CN109342412A (en) * | 2018-11-15 | 2019-02-15 | 成都润道检测技术有限责任公司 | A kind of detection device that polymorphic type gas can detect simultaneously |
| CN110095555A (en) * | 2019-04-26 | 2019-08-06 | 海南电网有限责任公司电力科学研究院 | One kind is based on analysis SF6Chromatographic detection system and detection method |
| EP3839982A1 (en) * | 2019-12-20 | 2021-06-23 | Siemens Aktiengesellschaft | High voltage feedthrough and method for monitoring the operation of same |
-
1985
- 1985-09-06 CA CA000490129A patent/CA1257185A/en not_active Expired
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5075544A (en) * | 1989-11-24 | 1991-12-24 | Mitsubishi Denki Kabushiki Kaisha | Optical color change device for detecting electrical abnormality |
| DE4133947A1 (en) * | 1991-10-14 | 1993-04-15 | Asea Brown Boveri | Sensor for decomposition prod. of insulating gas pref. sulphur hexa:fluoride - comprises indicator composed of composite material including a filler in matrix which is chemically inert and permeable to prods. |
| DE4133947B4 (en) * | 1991-10-14 | 2004-07-29 | Abb Schweiz Ag | Sensor for detecting decomposition products of an insulating gas in an encapsulated electrical system |
| US6126732A (en) * | 1993-06-24 | 2000-10-03 | Dentsply Detrey Gmbh | Dental prosthesis |
| CN108007925A (en) * | 2017-11-16 | 2018-05-08 | 国网福建省电力有限公司泉州供电公司 | SF6Gas decomposition product colorimetric determination instrument |
| CN109342412A (en) * | 2018-11-15 | 2019-02-15 | 成都润道检测技术有限责任公司 | A kind of detection device that polymorphic type gas can detect simultaneously |
| CN110095555A (en) * | 2019-04-26 | 2019-08-06 | 海南电网有限责任公司电力科学研究院 | One kind is based on analysis SF6Chromatographic detection system and detection method |
| CN110095555B (en) * | 2019-04-26 | 2021-02-26 | 海南电网有限责任公司电力科学研究院 | SF based on analysis6Chromatographic detection system and detection method |
| EP3839982A1 (en) * | 2019-12-20 | 2021-06-23 | Siemens Aktiengesellschaft | High voltage feedthrough and method for monitoring the operation of same |
| DE102019220367A1 (en) * | 2019-12-20 | 2021-06-24 | Siemens Aktiengesellschaft | High-voltage bushing and procedures for their operational monitoring |
| US11923107B2 (en) | 2019-12-20 | 2024-03-05 | Siemens Energy Global GmbH & Co. KG | High-voltage bushing and method for monitoring its operation |
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