ADSORPTION DEVICE FOR GAS INSULATED ELECTRIC APPARATUS

Abstract: An adsorption device is provided for adsorbing decom­ posed gas and the like produced in a gas-insulated electric apparatus. The adsorption device has an enclosed casing for encasing an adsorbent, which is secured internally, exter­ nally, or outwardly in a spaced apart relation to one wall of said apparatus housing. Valve means are provided in inlet and outlet portions of said casing, and an access port for replacing the adsorbent is provided for said casing to be normally closed by a detachable cover plate.

Description: ABSORPTION DEVICE FOR GAS INSULATED ELECTRIC APPARATUS BACKGROUND OF THE INVENTION This invention relates to a gas insulated electric apparatus, and more particularly to an adsorption device for the gas insulated electric apparatus capable of adsorbing moisture and decomposed gases of, for instance, a halogen containing gas filled in the apparatus is provided at a suitable position of the apparatus. Recently, halogen containing gases such as sulfur hexafluoride gas (SF6) are widely used in gas insulated electric apparatus, such as circuit interrupter and enclosed type switchboards for improving insulation and reducing sizes. However, the gases of the afore-mentioned type entails the following disadvantages. (1) The gas easily reacts with moisture remaining in the apparatus or intruded therein from outside through a mechanical connecting portion to thereby produce chemical compounds that deteriorate the insulation or metal parts of the apparatus. (2) By the arcs of arc discharge, the gas is easily decomposed into sulfur fluoride (SF2) gas and sulfur tetrafluoride (or4) gas which deteriorate insulation and metal parts of the apparatus. In order to eliminate such drawbacks, an adsorbent such as activated alumina or synthetic zeolite has been utilized for the apparatus in a state encased in one or more casings and placed in suitable positions of the apparatus. Such arrangement as described above, however, tends to cause the following difficulties. (1) It is difficult to decide the amount of the adsorbent to be used because the required amount thereof is varied depending on the amount of moisture contained in the apparatus, intensity and frequency of the occurrence of arc-discharge, and time interval between periodical inspections carried out on the apparatus. Furthermore, where the apparatus is an enclosed switchboard, unpredictable troubles in the relevant power system must be considered. (2) Each time when the adsorbent placed in the apparatus is replaced, electric power supplied thereto must be interrupted. (3) When a large amount of adsorbent is beforehand placed in the apparatus so that the operation stop other than the periodical inspection time is made unnecessary, the size of the casing or casings in which the adsorbent is stored becomes large, thus increasing the space required for providing the adsorbent containing device in the apparatus. SUMMARY OF THE INvENmIo\ An object of this invention is to provide an adsorption device for a gas-insulated electric apparatus wherein the above described difficulties in the conventional application of the adsorbent can be substantially eliminated. A more specific object of this inventIon is to provide an adsorption device for a aas-insulated electric apparatus wherein the adsorbent fcr removing decompose gas and the like can be replaced wit. iring interruption of electric power, and the guantity of the adsorbent and hence the space required r the Installation of the apparatus can be economized. These and other objects of the present invention can be achieved by the provision of a gas-insulated electric apparatus filled with a halogen containing gas, wherein an adsorbing device for adsorbing decomposed gases of the halogen containing gas and moisture is secured to an outer wall of the apparatus. According to another feature of the invention, the adsorbing device secured to the outer wall of the apparatus is so constructed that an adsorbing agent encased therein can be replaced without interrupting the power supply to the apparatus. According to still andther feature of the invention, the adsorption device for the electric apparatus further comprises a self-contained gas circulating device which forcibly circulates the halogen contained gas through the adsorbing device. More specifically, according to this invention, there is provided an adsorption device provided for a gas- insulated electric apparatus having a gas-tight housing filled with a halogen containing gas for eliminating decomposed gases of the gas and moisture, and the adsorption device comprises an enclosed type casing secured to one wall of the housing for storing an adsorbent, inlet and outlet provided for the casing to permit circulation of the gas between the housing and the casing therethrough, valve means provided in the inlet and outlet for penitti:.g or interrupting the circulation of the gas, the cain having an access port through which the adsorbent can be replaced, and a cover plate detachably secured to a suitable portion for closing the access port in a gas tight manner. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is an elevational view in section showing a gas insulated electric apparatus in the form of an enclosed type switchboard including a gas absorption device, which constitutes a preferred embodiment of the invention; ana FIGS. 2 and 3 are similar views as FIG. 1 showing further embodiments of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail with reference to FIGS. 1, 2 and 3 all showing a case wherein the gas insulated electric apparatus is in the form of an enclosed type switchboard. As shown in FIG. 1, the enclosed type switchboard comprises a housing 1 having a top wall through which a connector 2 is extended. The outer end of the connector 2 is connected to a power source bus, while the internal end of the connector 2 is connected through an arrester 3, a potential transformer 4, a disconnector 5A, to the upper terminal of a circuit breaker 6. The lower terminal of the circuit breaker 6 is connected through another disconnector 5B and a cable head 7 to a load-side cable 8. The internal space within the housing 1 is filled with a halogen containing gas such as sulfur hexafluoride SF6, which is introduced into the housing 1 through a valve 9A while air therein is exhausted outside through another valve 9B. When the density of the halogen containing gas becomes a predetermined value, the valves 9A and 9B are closed. According to the present invention, an adsorption device 10 is pro-':'icea internally along a side wall of the housing 1. The device 10 comprises a box-like casing 11, one side wall of wi is substantially removed. The casing 11 is secures, or instance, b welding to the internal surface of one side wal c the hcusing 1 formed with an access port 1a. A cover plate 12 of a size sufficient to cover the access port la is detachably secured to the outer surface portion of the housing 1 surrounding the port la by means of, for instance, bolts and nuts, with a gasket 13 interposed between the cover plate 12 and the surroundinc portion of the housing 1. Valves 14A and 14B are provided for an inlet and outlet portion of the casIng 11 to permit or interrupt the circulation of the gas mixed with moisture and else through the interior of the casing 11. Hoods 15A and 15B are further provided upwardly and downwardly of the valves 14A and 14B, respectively, for guiding the flow of the mixed gas through the casing 11. Internally of the casing 11, there are provided a number of shelves 16, on which adsorbent 17 such as activated alumina or synthetic zeolite is stored An axial flow fan 18 is further provided below the shelves 16 for forcing the mixed gas to flow downward out of the casing 11 for facilitating the gas circulation therein. In the enclosed type switchboard constructed as described above, the halogen containing gas containing moisture and decomposed gases is warmed by heat generated in the switchboard to cause the mixed gas to flow, by thermal convection through the casing 11 downwardly. The fan 18 provided in the adsorption device 10 accelerates the circulation of the gas so as to improve the adsorption of the decomposed gases and moisture by the adsorption device 10. When it is required to replace the adsorbent, the cover plate 12 is removed out of the side wall of the housing 1 of the switchboard while the valves 14A and 14B are closed, and the old adsorbent is replaced with new adsorbent through the access port of the casing 11 without interrupting electric power in the apparatus. Whenever the operational life of the adsorbent is not sure after frequent unpredictable operations of the circuit breaker 6, a part of the gas may be saripled through the valve 9B or else for detecting the degree of contamins- tion or decomposition of the gas. Furthermore, the fan 18 provided in the adsorption device 10 may be operated to improve the decomposed gas removing capability of the device 10 in a case where a large amount of the decomposed gas is created by frequent operations of the circuit breaker 6. FIG. 2 illustrates another emnoci-;ent o the invention also applied to an enclosed type s-witchboar. In this embodiment, an adsorption device 30 is provided outside of the switchboard housing 21 to be secured thereto directly-. The adsorption device 30 comprises a box-like casing 31 of a construction substantially similar to the casing 11 of the embodiment shown in FIG. 1, with a left side wall as viewed in FIG. 2 thereof secured to the outside of a side wall of the housing 21 by, for instance, welding. A substantial part of one side wall, i.e. right side wall as viewed in FIG. 2 of the box-like casing 31 is removed for providing an access part. A cover plate 32 of a size sufficient to close the access port formed through the casing 31 is detachably secured to an edge portion of the casing 31 surrounding the access port by, for instance, bolts and nuts with a gasket 33 interposed between the cover plate 32 and the portion surrounding the access port. Valves 34A and 34B are provided in upper and lower parts of the casing 31 to permit or interrupt the flow of the halogen containing gas containing moisture and decomposed gases through the interior of-the casing 31. Hoods 35A and 35B of a frustum shape and semicircular as view from an upper position are also provided upwardly and downwardly of the valves 34A and 34B, respectively, for guiding the flow of the mixed gas through the casing 31 of the adsorption device 30. Internally of the casing 31, a number of shelves 36 are provided for storing adsorbent 37 such as activated alumina or synthetic zeolite on the shelves 36. An axial flow fan 38 is also provided below the shelves 36 for forcing the mixed gas to flow downward through the casing 31. In the embodiment shown in FIG. 2, since the adsorp ticn device 30 is provided outside of the switchboard housing 21 at a position closely adjacent to one side wall thereof, the production and the installation of the adsorption device 30 are facilitated. In FIG. 3 there is illustrated still another embodi ment of this invention, wherein an adsorption device 50 having a casing 51 is provided outside of the switchboard housing 41 at a position spaced apart from a side wall of the housing 41. The casing 51 of the device 50 is coupled with the housing 41 through upper and lower valves 54A and 54B rigidly secured to the housing 41, and flange connections 55A and 55B coupling the upper and lower portions of the casing 51 to the valves 54A and 54B, respectively. A valve 49B having a function similar to that of the valves 9B and 29B in the embodiments shown in FIGS. 1 and 2 is connected outwardly of the valve 54A in communication with the upper portion of the casing 51. A fan 52 is also provided in the casing 51 of the adsorption device 50 for circulating the gas in the switchboard housing 41 through the adsorption device 50. An access port, not numbered, is provided for the casing 51 on a side thereof remote from the housing 41 of the apparatus. A cover plate 52 is detachably secured to the casing 51 to close the access port by means of bolts and nuts with a gasket 53 interposed between the cover plate 52 and the casing 51 as in the previous embodiments shown in FIGS. 1 and 2. Furthermore, adsorbent storing shelves 56 ac an axial flow fan 58 are provided in the casing 51 as in the previous embodiments. With the above described construction anc arrangement of the enclosed type switchboard and associate members, the halogen containing gas, such as SF6, is filled into the apparatus while a valve 49A similar to the valves 9 and 29A in the previous embodiments, and the valves 54A and 49B are held open, whereas the valve 543 is close^. After the interior of the switchboard housing 41 is filled with the gas, te valves 49A, 493, are closed, while the valve 543 is opened. Alternatively, the valve 493 may be provided at a position indicated by dot and dash lines in FIG. 3 that it is connected outwardly o te valve 543 in communi- cation wit the lower portion of the casing 51. In tis case, the halogen containing gas is filled with the valve 54B closed while the valves 49A, 54A-and 49B are opened, so that the halogen containing gas mixed with air is delivered through the valve 49B into an apparatus, not shown, which is provided separately for substituting the gas. During the operation, when the density of the halogen containing gas in the housing 41 increases in excess of a required value, but the moisture therein is not yet reduced to a predetermined value, the valves 49A and 49B may be closed while the valves 54A and 54B are opened, so that the gas is circulated back into the housing 41 through the adsorption device 50 for removing the moisture out of the gas. According to this embodiment, since the adsorption device 50 can be secured to the switchboard housing 41 simply by the addition of the valves 54A and 54B, the production and installation of the adsorption device 50 can be further simplified. In the above described embodiment, although the fan 58 has been provided in the casing 51 of the device 50, it may be provided within the housing 41 at a position near the valve 54B. Since the gas insulated electric apparatus such as enclosed type switchboard is constructed as described above, the following advantages would be expected. (1) The adsorbent can be replaced without opening the housing, so that the electric apparatus can be operated continuously except the periodical inspection periods. (2) Because of the simple replacement of the adsorbent, there is no necessity o storing a large amount of adsorbent in the casing, thus enabling to reduce the floor area required for the apparatus. (3) Since the adsorbent can be replaced upon detection of a predetermined density of the decomposed gases, a high insulation reliability o the apparatus can be assured. In the foregoing embodiments shown in FIGS. 1 through 3, the vertical type gas adsorption device is disposed on the side wall of the housing of an gas insulated electric apparatus, but the adsorption device of this invention may be provided for the upper or lower wall thereof by the manner similar to that described with reference to the embodiments shown in FIGS. 1 through 3. Moreover, a fan for facilitating the circulation of gas in the adsorption device may also be located at the upper portion, i.e. upstream side, of the adsorption device.

Claims: WHAT IS CLAIMED IS: 1. An adsorption device provided for a gas-insulated electric apparatus having a gas-tight housing filled with a halogen containing gas for eliminating decomposed gases of said halogen containing gas and moisture, characterized in that said adsorption device comprises an enclosed type casing secured to one wall of said housing for storing an adsorbent, inlet and outlet provided for the casing to permit circulation of said halogen containing g gas between the housing and the casing therethrough, valve means provided in said inlet and outlet for permitting or inter- rupting the circulation of said halogen containing gas, said casing having an access port through which said adsorbent can be replaced, and a cover slate detachably secured to a suitable portion for closing said access crt in a gastight manner. 2. An absorption device as set forth in car. 1 which further comprises a fan provided near the outlet of casing or enhancing the circeiaticn c said halogen containing gas. 3. An adsorption device as set forth in claim 1 wherein said casing is secured to ons side wall of said housing so that the casing is disposed vertically, and said casing includes a number or shelves for storing the absorbent on said shelves. 4. An adsorption device as set forth in claim 1 wherein said casing is provided internally of said housing so that said casing is secured to one wall of said housing internally, and said cover plate is detachably secured to a portion of said housing formed with a port overlying said port. 5. An adsorption device as set forth in claim 1 wherein said casing is provided outwardly of said housing so that a wall of said casing facing to the housing is secured to one wall of said, housing externally. 6. An adsorption device as set forh in claim 1 wherein said casing is provided outwardly of said housing in a spaced apart relation from the housing, and said casing is secured to one wall of said housing through said valve means provided in said inlet and outlet of said casing. 7. An adsorption device as set forth in claim 1 wherein said halogen containing gas is sulfur hexafluoride SF6. 8. An adsorption device as set forth in claim 1 wherein said adsorbent includes activated alumIna. 9. An adsorption device as set forth in claim 1 wherein said adsorbent includes synthetic zeolite. 10. An adsorption device as set forth in claim 1 wherein said gas-insulated electric apparatus is an enclosed type switchboard.

Inventors: MATSUZAWA, KIKUO, TAKAGI, KUNIHIKO
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1984
Main classification: H02B13
IPC codes: H02B1, H02B13