Abstract:
According to an embodiment, a gas insulation apparatus (e.g., a gas circuit breaker) includes a high-voltage unit, a zeolite and an insulation gas in a closed vessel. The insulation gas is CO 2  gas or a gas including CO 2  gas as the main component. The zeolite is contained in a zeolite case and is placed under an insulation gas atmosphere. CO 2  is adsorbed on the zeolite before use of the gas insulation apparatus.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part (CIP) application based upon the International Application PCT/JP2010/003954, the International Filing Date of which is Jun. 15, 2010, the entire content of which is incorporated herein by reference, and is based upon and claims the benefits of priority from the prior Japanese Patent Application No. 2009-144383, filed in the Japanese Patent Office on Jun. 17, 2009, the entire content of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Embodiments described herein relate to a gas insulation apparatus using an insulation gas containing CO 2 . 
       BACKGROUND 
       [0003]    A power transmission/transformation system includes a gas insulation transmitter/transformer apparatus(hereinafter, referred to as “gas insulation apparatus”) such as a switchgear (such as a gas circuit breaker or a gas insulation disconnector), a gas insulation transformer, and a gas insulation pipe. A vessel of a gas insulation apparatus is filled with an insulation gas. The insulation gas serves as an electric insulation medium for preventing discharge between the vessel of the gas insulation apparatus and the electrical circuit in the vessel and as a cooling medium for suppressing temperature rise due to electric current. In addition, in a switchgear, the insulation gas serves as an arc-extinguishing medium for extinguishing arc discharge occurring at the switching operation. Currently, as an insulation gas filled in a high-voltage/large capacity gas insulation apparatus, a sulfur hexafluoride gas (hereinafter, referred to as “SF 6  gas”) is widely used. 
         [0004]    SF 6  gas is an inactive gas having considerably high stability and is harmless and noncombustible. Further, SF 6  gas is significantly excellent in the abovementioned insulation performance and the arc-extinguishing performance. Therefore, SF 6  gas is suitably used for a high voltage gas insulation apparatus, contributing to size reduction of the gas insulation apparatus. However, SF 6  gas has a global warming effect 23,900 times greater than CO 2  gas, so that the use of CO 2  gas as the insulation gas is now proposed. 
         [0005]    As described above, accidental discharge may occur between the vessel and the electrical circuit at the time of use of the gas insulation apparatus. Further, in the switchgear, arc discharge may occur at the switching operation. It is known that when such discharge occurs, the insulation gas is changed into plasma to cause dissociation of the insulation gas molecules. 
         [0006]    Even when the dissociation occurs due to discharge in the case where SF 6  gas is used as the insulation gas, the majority of the SF 6  molecules are recombined due to its high stability. It should be noted that there may be a case where a few sulfur (S) ions and a few fluorine (F) ions generated by the dissociation of the SF 6  molecules react with a small amount of water existing in the vessel to generate a very small amount of cracked gas such as HF or SOF 2  gas. However, the influence of the reaction is not strong enough to reduce the insulation performance, arc-extinguishing performance, and electric conducting performance of the gas insulation apparatus. 
         [0007]    In the case where CO 2  gas is used as the insulation gas, some oxygen (O) ions generated by dissociation of CO 2  molecules react with metal constituting the most part of the gas insulation apparatus to generate CO molecules as a cracked gas without involving recombination. Thus, the amount of CO 2  gas filled in the vessel is gradually reduced, while the amount of CO gas as the cracked gas is increased. CO 2  gas is lower than SF 6  gas in terms of the ratio of recombination after dissociation due to discharge. Therefore, in the case where CO 2  gas is used as the insulation gas, the insulation performance or arc-extinguishing performance of the gas insulation apparatus is reduced with the use of the gas insulation apparatus more easily than in the case where SF 6  gas is used. This often requires maintenance of the gas insulation apparatus or replenishment of the insulation gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The above and other features and advantages of the present invention will become apparent from the discussion hereinbelow of specific, illustrative embodiments thereof presented in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  is a partly schematic cross-sectional view of a gas insulation apparatus (gas circuit breaker) according to a first embodiment of the present invention, which illustrates a closed state of the gas circuit breaker; 
           [0010]      FIG. 2  is a partly schematic cross-sectional view of the gas insulation apparatus (gas circuit breaker) according to the first embodiment of the present invention, which illustrates a state where the gas circuit breaker is being opened; 
           [0011]      FIG. 3  is a schematic view for explaining adsorption by zeolite of the gas insulation apparatus according to the first embodiment of the present invention, which illustrates a state where CO 2  is being adsorbed to the zeolite; 
           [0012]      FIG. 4  is a schematic view for explaining adsorption by the zeolite of the gas insulation apparatus according to the first embodiment of the present invention, which illustrates a state where a cracked gas is being adsorbed to the zeolite; and 
           [0013]      FIG. 5  is a partly schematic cross-sectional view of the gas insulation apparatus (gas insulation transformer) according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The embodiments described here have been made to solve the above problem, and an object thereof is to suppress a reduction in the insulation performance or arc-extinguishing performance in a gas insulation apparatus using an insulation gas containing CO 2 . 
         [0015]    According to an aspect of the present invention, a gas insulation apparatus includes a closed vessel, a high-voltage unit arranged inside the closed vessel, an insulation gas containing CO 2  filled in the closed vessel, and a zeolite arranged in the insulation gas. 
       First Embodiment 
       [0016]    A first embodiment of a gas insulation apparatus according to the present invention will be described below with reference to  FIGS. 1 to 4 . A gas insulation apparatus according to the present embodiment is a puffer type gas circuit breaker. 
         [0017]    A structure of the gas insulation apparatus (gas circuit breaker) according to the present embodiment will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a partly schematic cross-sectional view of the gas insulation apparatus (gas circuit breaker) according to the present embodiment, which illustrates a closed state of the gas circuit breaker.  FIG. 2  is a partly schematic cross-sectional view of the gas insulation apparatus (gas circuit breaker) according to the present embodiment, which illustrates a state where the gas circuit breaker is being opened. 
         [0018]    The gas circuit breaker includes, in a closed vessel  10 , a high-voltage unit, a zeolite  20 , and an insulation gas. 
         [0019]    The closed vessel  10  is formed into substantially a cylindrical shape. The closed vessel  10  is made of metal or insulator. The closed vessel  10  is grounded. 
         [0020]    The gas insulation apparatus according to the present embodiment is a gas circuit breaker and has a function of shutting off large current applied in the high-voltage unit. In order to suppress discharge from the high-voltage unit to the closed vessel  10 , the high-voltage unit is arranged in the closed vessel  10  away from the closed vessel  10  by an interval  11 . The closed vessel  10  is filled with an insulation gas. 
         [0021]    The high-voltage unit includes a fixed part  30 , a movable part  40 , and electric conductive parts  61  and  62 . 
         [0022]    The fixed part  30  and the movable part  40  are arranged along the axis of the closed vessel  10  so as to face each other. The fixed part  30  and the movable part  40  are fixed to the closed vessel  10  by supports  71  and  72  each made of an insulating body. 
         [0023]    The electric conductive parts  61  and  62  are fixed to the closed vessel  10  by spacers  73  and  74  each made of an insulating body. The spacers  73  and  74  each also play a role of preventing the insulation gas filled in the closed vessel  10  from leaking outside. 
         [0024]    In the closed state ( FIG. 1 ) of the gas circuit breaker, large current flows into the gas circuit breaker through a bushing (not illustrated). The large current flows in the electric conductive part  61 , the fixed part  30 , the movable part  40 , and the electric conductive part  62 . After that, the large current flows out from the gas circuit breaker through a bushing (not illustrated). 
         [0025]    The fixed part  30  includes a fixed arc contact  31 , a fixed conductive contact  32 , and a fixed conductive plate  33 . 
         [0026]    The fixed arc contact  31  is formed into a rod-like shape and extends along the axis of the closed vessel  10 . The fixed conductive contact  32  is formed into a cylindrical shape and extends along the axis of the closed vessel  10  so as to surround the fixed arc contact  31 . The fixed conductive plate  33  is formed into a plate-like shape and is arranged inside the fixed conductive contact  32  so as to extend perpendicular to the axis of the closed vessel  10 . The fixed conductive plate  33  makes the fixed arc contact  31  and fixed conductive contact  32  conductive. 
         [0027]    The movable part  40  includes a movable arc contact  41 , a movable conductive contact  42 , a driving rod  43 , a puffer cylinder  44 , a connecting plate  45 , an insulation nozzle  46 , a piston  47 , and the like. 
         [0028]    The driving rod  43  is formed into a cylindrical shape and extends along the axis of the closed vessel  10 . The end portion of the driving rod  43  on the opposite side to the fixed part  30  is connected to a driving unit  75 , and the driving rod  43  is moved in the axial direction (left-right direction of  FIGS. 1 and 2 ) of the closed vessel  10  by a driving unit  75 . 
         [0029]    The movable arc contact  41  is formed into an annular shape and protrudes from the fixed part  30  side end portion of the driving rod  43  toward the fixed part  30 . In the closed sate ( FIG. 1 ), the inner peripheral surface of the movable arc contact  41  contacts the outer peripheral surface of the fixed arc contact  31 . 
         [0030]    The puffer cylinder  44  is formed into a cylindrical shape and extends along the axis of the closed vessel  10 . The puffer cylinder  44  is arranged around the outer periphery of the driving rod  43  so as to be spaced apart from the driving rod  43 . The connecting plate  45  is formed into a plate-like shape and extends, perpendicular to the axis of the closed vessel  10 , from the fixed part  30  side end portion of the puffer cylinder  44  to the outer peripheral surface of the driving rod  43 . The connecting plate  45  connects the driving rod  43  and the puffer cylinder  44 . 
         [0031]    The movable conductive contact  42  is formed into an annular shape and protrudes from the fixed part  30  side surface of the connecting plate  45  toward the fixed part  30 . The movable conductive contact  42  is arranged around the outer periphery of the movable arc contact  41  so as to be spaced apart from the movable arc contact  41 . In the closed state ( FIG. 1 ), the outer peripheral surface of the movable conductive contact  42  contacts the inner surface of the fixed conductive contact  32 . 
         [0032]    The insulation nozzle  46  is formed into an annular shape and protrudes from the fixed part  30  side surface of the connecting plate  45  toward the fixed part  30 . The insulation nozzle  46  is arranged between the movable arc contact  41  and the movable conductive contact  42 . The insulation nozzle  46  is arranged spaced apart from the movable arc contact  41  and surrounds the outer periphery and distal end of the movable arc contact  41 . The insulation nozzle  46  is an insulating body made of, e.g., fluorine resin such as polytetrafluoroethylene. 
         [0033]    The above movable arc contact  41 , the movable conductive contact  42 , the driving rod  43 , the puffer cylinder  44 , the connecting plate  45 , and the insulation nozzle  46  are integrally formed and thus are integrally moved in the axial direction (left-right direction of  FIGS. 1 and 2 ) of the closed vessel  10  by the driving unit  75 . 
         [0034]    The piston  47  has a double-pipe structure composed of an inner pipe  48  and an outer pipe  49 . The inner pipe  48  and the outer pipe  49  extend along the axis of the closed vessel  10  and are spaced apart from each other. The puffer cylinder  44  is slidably arranged between the inner pipe  48  and the outer pipe  49 . A flange  50  extending toward the axial center of the closed vessel  10  is formed at the fixed part  30  side end portion of the inner pipe  48 . A through hole  51  corresponding to the outer diameter of the driving rod  43  is formed in the flange  50 . The driving rod  43  is inserted through the through hole  51  and arranged inside the inner pipe  48  so as to be spaced apart from the inner pipe  48 . The driving rod  43  is slidable with respect to the piston  47 . 
         [0035]    A first communicating hole  52  and a second communicating hole  53  are formed respectively in the inner pipe  48  and the outer pipe  49 . The insulation gas is filled in a space (hereinafter referred to “piston chamber”)  54  surrounded by the driving rod  43 , the inner pipe  48 , and the flange  50  through the first and the second communicating holes  52  and  53 . 
         [0036]    A third communicating hole  55  is formed in the flange  50 , and a check valve  56  is provided in the third communicating hole  55 . Thus, a space (hereinafter referred to “cylinder chamber”)  57  surrounded by the driving rod  43 , the puffer cylinder  44 , the flange  50 , and the connecting plate  45  communicates with the piston chamber  54  through the third communicating hole  55  and the check valve  56 . The insulation gas is prevented from flowing from the cylinder chamber  57  to the piston chamber  54  by the check valve  56 , while when the inner pressure of the cylinder chamber  57  is lower than that of the piston chamber  54 , the insulation gas flows from the piston chamber  54  to the cylinder chamber  57 . 
         [0037]    In the present embodiment, the insulation gas is CO 2  gas or a mixed gas mainly containing CO 2  gas (mixed gas in which the mass mixing ratio of CO 2  gas is 50% or more). 
         [0038]    In the case where the insulation gas is the mixed gas mainly containing CO 2  gas, the gas other than CO 2  gas is preferably a gas having a non-polar molecular structure, such as N 2  gas, O 2  gas, or He gas. Alternatively, the gas other than CO 2  gas is preferably a gas having a larger molecular diameter than that of CO 2  gas, such as CF 4  gas. 
         [0039]    The gas circuit breaker according to the present embodiment has, in the closed vessel  10 , the zeolite  20  housed in a zeolite case  21 . In the zeolite case  21 , a bead-shaped or pellet-shaped zeolite of, e.g., several mm is housed. A large number of air holes  22  are formed in the zeolite case  21 , and CO 2  gas filled in the closed vessel  10  contacts the zeolite in the zeolite case  21  through the air holes  22 . 
         [0040]    The zeolite case  21  is arranged above the high-voltage unit. Further, the zeolite case  21  is arranged in the flow passage (e.g., in the vicinity of a sixth communicating hole  35 ) of the insulation gas that has been blown to arc-discharge  81  to be described later. 
         [0041]    The zeolite  20  is, e.g., synthetic zeolite and, particularly, synthetic zeolite having pore diameters between 0.2 nm and 0.5 nm (e.g., A-type zeolite) is preferably used. 
         [0042]    Preferably, CO 2  molecules are adsorbed to the zeolite  20  in advance before use of the gas circuit breaker. For example, the gas circuit breaker according to the present embodiment is produced as follows. The high-voltage unit and zeolite case  21  are arranged at predetermined positions inside the closed vessel  10 , and the closed vessel  10  is vacuumed. Subsequently, CO 2  gas is enclosed with high pressure in the closed vessel  10  to adsorb CO 2  gas to the zeolite  20 . After that, predetermined insulation gas is filled in the closed vessel  10 . 
         [0043]    The opening operation of the gas insulation apparatus (gas circuit breaker) according to the present embodiment will be described with reference to  FIGS. 1 and 2 . 
         [0044]    In the closed state ( FIG. 1 ), the fixed arc contact  31  and the movable arc contact  41  contact each other, and the fixed conductive contact  32  and the movable conductive contact  42  contact each other, whereby electrical conduction is established between the fixed part  30  and the movable part  40 . 
         [0045]    To shut off current, the driving unit  75  is used to move the driving rod  43  in the direction (left direction of  FIG. 1 ) away from the fixed part  30 . Accordingly, the fixed arc contact  31  and the movable arc contact  41 , as well as, the fixed conductive contact  32  and the movable conductive contact  42  are separated from each other. As a result, as illustrated in  FIG. 2 , arc discharge  81  is generated between the fixed arc contact  31  and the movable arc contact  41 . 
         [0046]    The puffer cylinder  44  is housed in the piston  47  in association with the opening operation, so that the volume of the cylinder chamber  57  is reduced. Then, the insulation gas filled in the cylinder chamber  57  passes through the fourth communicating hole  58  formed in the connecting plate  45  and a gap  59  between the movable arc contact  41  and the insulating nozzle  46  to be blown to the arc discharge  81 . As a result, the arc discharge  81  loses its conductivity, whereby the current is shut off. In general, in order to obtain high arc-extinguishing performance, high blowing pressure and high flow rate of the insulation gas are required. 
         [0047]    The insulation gas that has been blown passes through a fifth communicating hole  34  formed in the fixed conductive plate  33  and a sixth communicating hole  35  formed in the fixed conductive contact  32  for convection inside the closed vessel  10 , as a flow passage  83  illustrated in  FIG. 2 . 
         [0048]    Effects of the gas insulation apparatus (gas circuit breaker) according to the present embodiment will be described with reference to  FIGS. 3 and 4 .  FIG. 3  is a schematic view for explaining adsorption by the zeolite of the gas insulation apparatus according to the first embodiment of the present invention, which illustrates a state where CO 2  is being adsorbed to the zeolite.  FIG. 4  is a schematic view for explaining adsorption by the zeolite of the gas insulation apparatus according to the first embodiment of the present invention, which illustrates a state where a cracked gas is being adsorbed to the zeolite. 
         [0049]    CO 2  gas is inferior to SF 6  gas but far superior to air in terms of the insulation performance and arc-extinguishing performance. In addition, CO 2  gas is far less significant than SF 6  gas in the global warming. Thus, according to the present embodiment, it is possible to provide a gas circuit breaker having high insulation performance and arc-extinguishing performance and less significant in the global warming. 
         [0050]    When the insulation gas is blown to the arc discharge  81 , CO 2  gas is dissociated to generate CO gas, as described above. Then, when the concentration of CO gas in the closed vessel  10  is increased, the insulation performance and the arc-extinguishing performance of the gas circuit breaker are deteriorated. However, according to the present embodiment, the CO molecules are adsorbed to the zeolite  20 , thereby suppressing the increase in the concentration of CO gas in the closed vessel  10 . Thus, it is possible to suppress the insulation performance and the arc-extinguishing performance of the gas circuit breaker from being deteriorated. 
         [0051]    Further, as described above, CO gas is generated in the closed vessel  10  in association with the dissociation of CO 2  gas, and the amount of CO 2  gas in the closed vessel  10  is reduced, with the result that the insulation performance and the arc-extinguishing performance of the gas circuit breaker are deteriorated. However, when the CO 2  molecules are adsorbed to the zeolite  20  before use of the gas circuit breaker as in the present embodiment, the generated CO molecules are adsorbed to the zeolite  20 , and the CO 2  molecules that have been adsorbed to the zeolite  20  are released. Therefore, the increase in the amount of CO gas in the closed vessel  10  can be suppressed, and also the reduction in the amount of CO 2  gas can be suppressed. This can suppress the deterioration in the insulation performance and the arc-extinguishing performance of the gas circuit breaker. 
         [0052]    As schematically illustrated in  FIG. 3 , CO 2  molecules  84  adsorbed to the zeolite  20  are physically and electrically trapped in a pore  23  of the zeolite  20 . The CO 2  molecules  84  have non-polar molecular structures and thus are less electrically constrained. On the other hand, CO molecules  85  are more subject to electrical constraint than the CO 2  molecules  84  due to their polar molecular structures and are thus easily adsorbed to the zeolite  20 . In addition, the CO molecules  85  are physically more easily adsorbed to the zeolite  20  as compared with the CO 2  molecules  84  due to their smaller molecular size than the CO 2  molecules  84 . Thus, as schematically illustrated in  FIG. 4 , the CO molecules  85  force the CO 2  molecules  84  out of the pore  23  and, instead, go into the pore  23 . Therefore, according to the present embodiment, “molecular exchanges” are effectively achieved, in which the CO molecules  85  are adsorbed to the zeolite  20  and the CO 2  molecules  84  that have been adsorbed to the zeolite  20  are released. This suppresses an increase in the amount of CO gas in the closed vessel  10  and a reduction in the amount of CO 2  gas. 
         [0053]    The abovementioned “molecular exchanges” are preferably performed in one-to-one correspondence manner in order to maintain the gas filling pressure in the closed vessel  10  constant. To this end, the pore diameter of the zeolite  20  is preferably designed such that one of the CO 2  molecules (molecular diameter: about 0.35 nm)  84  and the CO molecules (molecular diameter: about 0.28 nm)  85  can fit into the pore  23 . Thus, as in the present embodiment, the average pore diameter of the zeolite  20  is preferably set to a range between 0.2 nm and 0.5 nm. It should be noted that a molecule having a molecular diameter smaller than the average pore diameter can be adsorbed due to thermal motion of the zeolite  20 , the CO 2  molecules  84  and the CO molecules  85  or the like. 
         [0054]    The gas circuit breaker according to the present embodiment has the insulation nozzle  46  made of fluorine resin. This may cause a case where the insulation nozzle  46  is sublimated by the arc discharge  81  to generate fluorine (F) ion, which reacts with water in the closed vessel  10  to generate a hydrogen fluoride (HF) gas. According to the present embodiment, as schematically illustrated in  FIG. 4 , this HF molecule  86  can be adsorbed to the zeolite  20 . The HF molecule  86  has a polar molecular structure and has a smaller molecule diameter than that of the CO 2  molecule and is thus more easily adsorbed to the zeolite  20  as compared to the CO 2  molecule. 
         [0055]    When the average pore diameter of the zeolite  20  is between 0.2 nm and 0.5 nm as in the present embodiment, there may be a case where one CO molecule  85  and one HF molecule  86  are adsorbed to one pore  23  at the same time, as illustrated in  FIG. 4 . 
         [0056]    In the case where the insulation gas is the mixed gas mainly containing CO 2  gas, the gas other than CO 2  gas is preferably a gas having a non-polar molecular structure, and the gas other than CO 2  gas is preferably a gas having a larger molecular diameter than that of CO 2  gas. This is because when the gas other than CO 2  gas has a polar molecular structure, it can easily force the CO 2  molecule that has previously been adsorbed to the zeolite  20  out and, instead, be adsorbed to the zeolite  20 . Further, this is because when the gas other than CO 2  gas has a smaller molecular diameter than that of CO 2  gas, it can easily force the CO 2  molecule that has previously been adsorbed to the zeolite  20  out and, instead, be adsorbed to the zeolite  20 . 
         [0057]    Further, CO gas and HF gas generated by the arc discharge  81  are lighter in weight than CO 2  gas constituting the insulation gas, so that they accumulate upward in the closed vessel  10 . Thus, when the zeolite case  21  is arranged above the high-voltage unit, the “molecular exchange” is effectively achieved. When the zeolite case  21  is arranged in the flow passage of the insulation gas that has been blown to arc-discharge  81 , CO gas and HF gas are easily adsorbed to the zeolite  20  immediately after being generated, thereby maintaining the insulation performance and the arc-extinguishing performance of the gas circuit breaker. 
         [0058]    Although the arc discharge  81  has been taken as an example of the discharge in the closed vessel  10  in the above description, CO gas or HF gas is generated also when accidental discharge  82  as illustrated in  FIG. 1  occurs. Also in this case, according to the present embodiment, it is possible to suppress a reduction in the insulation performance and the arc-extinguishing performance of the gas circuit breaker. 
       Second Embodiment 
       [0059]    A second embodiment of the gas insulation apparatus according to the present invention will be described with reference to  FIG. 5 . The gas insulation apparatus according to the present embodiment is a gas insulation transformer. 
         [0060]    First, a structure of the gas insulation apparatus (gas insulation transformer) according to the present embodiment will be described with reference to  FIG. 5 .  FIG. 5  is a partly schematic cross-sectional view of the gas insulation apparatus (gas insulation transformer) according to the second embodiment of the present embodiment. The present embodiment is a modification of the first embodiment, so that overlapping descriptions are omitted. 
         [0061]    The gas insulation transformer contains the high-voltage unit, zeolite  20  and insulation gas in the closed vessel  10  and has a pipe  94 , a blower  97 , and a cooler  98 . 
         [0062]    The high-voltage unit has an iron core  91  and coils  92  and  93  wound around the outer periphery of the iron core  91 . 
         [0063]    The blower  97  and cooler  98  are arranged outside the closed vessel  10 . Insulation gas in the closed vessel  10  is sucked through an inlet  95  by the blower  97 , passed through the pipe  94 , and flows into the cooler  98  for cooling. The cooled insulation gas then is passed through the pipe  94  and returns to the inside of the closed vessel  10  through an outlet  96 . The insulation gas circulates in the gas insulation transformer in this manner. 
         [0064]    Although the gas insulation transformer is a static apparatus that does not involve opening/closing of current, it also has a tap switching unit (not illustrated) for switching between the coils  92  and  93  in accordance with a load. At the tap switching time, discharge occurs in the closed vessel  10 . Further, due to malfunction such as insulation failure, accidental discharge  82  may occur between the coils  92 ,  93  and the closed vessel  10 . 
         [0065]    As described in the first embodiment, such discharge may dissociate the insulation gas to generate a cracked gas such as CO gas to reduce the amount of CO 2  gas, resulting in deterioration of the insulation performance of the gas insulation transformer. 
         [0066]    In order to cope with this, also in the present embodiment, the zeolite case  21  housing the zeolite  20  is arranged in the closed vessel  10 . As illustrated in  FIG. 5 , when the zeolite case  21  is arranged in the middle of the circulation passage of the insulation gas at a portion in the vicinity of the outlet  96 , the cracked gas is effectively adsorbed. Alternatively, the zeolite case  21  may be arranged in the vicinity of the inlet  95  for the same reason. Further, an adsorption chamber housing the zeolite  20  may be arranged in the middle of the pipe  94 . 
       Another Embodiments 
       [0067]    The first and the second embodiments are illustrative only, and the present invention is not limited thereto. 
         [0068]    Although the gas circuit breaker and gas insulation transformer are taken as examples of the gas insulation apparatus of the present invention in the first and the second embodiments, respectively, the present invention may also be applied to a gas insulation switchgear such as a gas insulation disconnector, a gas insulation arrester, and a gas insulation pipe. 
         [0069]    The zeolite  20  need not be a type in which powder thereof is housed in the zeolite case  21  but may be a type using synthetic zeolite film.