Patent Publication Number: US-8522817-B1

Title: Apparatus and method for fast recovery and charge of insulation gas

Description:
The United States government may have certain rights to this invention under Management and Operating Contract No. DE-AC05-06OR23177 from the Department of Energy 
    
    
     FIELD OF INVENTION 
     The present invention relates to an apparatus and method for fast recovery and charge of insulation gas in an electronic device. 
     BACKGROUND OF THE INVENTION 
     Sulfur hexafluoride (SF 6 ) has been used as a gaseous dielectric (insulator) in electrical equipment since the 1950s. It is now known that SF 6  is a potent greenhouse warming gas with one of the highest global warming potentials (GWP) known. The basic physical and chemical properties of SF 6 , its behavior in various types of gas discharges, and its uses in electrical equipment have been broadly investigated. 
     Besides its good insulating and heat transfer properties, SF6 has a relatively high pressure when contained at room temperature. It is easily liquefied under pressure at room temperature allowing for compact storage in gas cylinders. However, the liquefaction process can be time consuming, inefficient and relatively expensive. 
     SF 6  has some other undesirable properties: it is an efficient infrared (IR) absorber and due to its chemical inertness, is not rapidly removed from the earth&#39;s atmosphere. Both of these properties make SF 6  a potent greenhouse gas. The strong infrared absorption of SF 6  and its long lifetime in the environment are the reasons for its extremely high global warming potential which for a 100-year time horizon is estimated to be more than 22,000 times greater (per unit mass) than that of CO 2 , the predominant contributor to the greenhouse effect. 
     Accordingly, many in the electrical equipment industry have spent substantial time and effort seeking suitable replacement gases to reduce the use of SF 6  in electrical equipment. To date, the possible replacement gases have been identified as (i) mixtures of SF 6  and nitrogen for which a large amount of research results are available; (ii) gases and mixtures (e.g., low concentrations of SF 6  in N 2 , and SF 6 —He mixtures) for which a smaller yet significant amount of data is available; and (iii) other potential gases for which little experimental data is available, e.g., Arsenic pentafluoride; Arsine; diboron tetrafluoride; diborane, etc. 
     These compounds, including SF 6 , are useful in the gas phase for electrical insulation and for arc quenching and current interruption equipment used in the transmission and distribution of electrical energy. Generally, there are four major types of electrical equipment devices where these gases can be employed for insulation and/or interruption purposes: (1) gas-insulated circuit breakers and current interruption equipment, (2) gas-insulated transmission lines, (3) gas-insulated transformers, and (4) gas-insulated substations. Such gas-insulated equipment is a major component of power transmission and distribution systems all over the world. 
     Regardless, of which insulation gas is used, including SF 6 ; all of the insulation gases have some amount of global warming potential. When the various types of electrical equipment discussed above require maintenance or when the electrical equipment is used under laboratory or experimental conditions there is a need for an apparatus and method for fast recovery and charge of the insulation gas. Particularly, methods that avoid time consuming and inefficient liquefaction steps. The present invention addresses these problems by avoiding liquefaction of the gas reducing the recovery and charge time of insulation gas from electrical equipment; reducing the cost of maintenance activity; and reducing the amount of escaped gas, thereby reducing the environmental impact of insulation gas recovery and charge in electrical equipment. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an insulation gas recovery and charge apparatus comprising a pump, a connect, an inflatable collection device and at least one valve. 
     In another embodiment the insulation gas recovery and charge apparatus has at least one valve having a collection state and a charge state. 
     In another embodiment the insulation gas recovery and charge apparatus has at least one valve in communication with the inflatable collection device and the connect, where the connect is capable of connecting an electrical equipment device insulated with gas to the insulation gas recovery and charge apparatus. 
     In yet another embodiment of the invention the insulation gas recovery and charge apparatus has a connect capable of connecting to an electrical equipment device, the pump is capable of directing gas from the electrical equipment device to the inflatable collection device when the at least one valve is in the collection state and directs gas from the inflatable collection device to the electrical equipment device when the at least one valve is in the charge state. 
     In still another embodiment of the invention the insulation gas recovery and charge apparatus has a second pump in communication with the electrical equipment. 
     In another embodiment the insulation gas recovery and charge apparatus includes a filter. 
     In another embodiment the insulation gas recovery and charge apparatus includes a gas drying system. 
     In another embodiment the present invention relates to an insulation gas recovery and charge apparatus comprising a pump, a connect for connecting the insulation gas recovery and charge apparatus to an electrical equipment device insulated with a gas, an inflatable collection device, at least one valve having a collection state and a charge state, wherein the at least one valve is in communication with the inflatable collection device and the electrical equipment device when the connect is connected to an electrical equipment device, and wherein the pump is capable of directing the gas from the electrical equipment device to the inflatable collection device when the at least one valve is in the collection state and directing a gas from the inflatable collection device to the electrical equipment device when the at least one valve is in the charge state. 
     In still another embodiment, the present invention relates to a system for recovering and charging insulation gas comprising, connecting a gas recovery and charge apparatus as described previously through the connect to an electrical equipment device containing an insulation gas and removing the insulation gas from the electrical equipment device by operating the pump wherein the insulation gas is collected in the inflatable collection device. 
     In yet another embodiment the system for recovering and charging insulation gas further includes, returning the insulation gas into the electrical equipment device by operating the pump wherein the insulation gas is removed from the collection device and returned to the electrical equipment device. 
     In another embodiment of the system for recovering and charging insulation gas the insulation gas recovery and charge apparatus has at least one valve having a collection state and a charge state. 
     In another embodiment of the system for recovering and charging insulation gas the at least one valve is in selected communication with the gas collection device and an electrical equipment device. 
     In another embodiment of the system for recovering and charging insulation gas the pump is capable of directing a gas from the electrical equipment device to the gas collection device when the at least one valve is in the collection state and directing a gas from the collection device to the electrical equipment device when the at least one valve is in the charge state. 
     In another embodiment of the system for recovering and charging insulation gas the insulation gas recovery and charge apparatus further comprises a second pump in communication with the electrical equipment. 
     In yet another embodiment of the system for recovering and charging insulation gas the insulation gas recovery and charge apparatus includes a filter. 
     In yet another embodiment of the system for recovering and charging insulation gas the insulation gas recovery and charge apparatus includes a gas drying system. 
     In yet another embodiment of the system for recovering and charging insulation gas the insulation gas is selected from the group consisting of, arsenic pentafluoride; arsine; diboron tetrafluoride; diborane; perchloric acid, 2-chloro-1,1,2,2-tetrafluoroethyl ester (9Cl); perchloric acid, 1,2,2-trichloro-1,2-difluoroethyl ester; trifluoroacetyl chloride; trifluoromethylisocyanide (CF 3 —NC); trifluoromethyl isocyanide; trifluoro-nitro so-ethene//trifluor-nitroso-aethen; tetrafluoroethene; 3,3,4,4-tetrafluoro-3,4-dihydro-[1,2]diazete; (difluoramino)difluoracetonitril; tetrafluorooxirane; trifluoroacetyl fluoride; sulfur hexafluoride; Nitrogen; and mixtures thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become apparent from the discussion below of specific, illustrative embodiments thereof presented in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic block diagram showing an embodiment of a fast recovery and charge system according to the present invention. 
         FIG. 2  is a schematic block diagram illustrating an embodiment of a fast recovery and charge system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to an apparatus and method for fast recovery and charge of insulation gas in various electronic devices.  FIG. 1  illustrates schematically the basic components of the invention. 
     Referring to  FIG. 1 , the insulation gas recovery and charge apparatus is connected through connect  35  to electrical equipment device  5 . The connect  35  can be any type of connection means, such as a threaded male or female connection or a quick-connect device. The electrical equipment device  5  is typically a high voltage power supply and may include gas-insulated circuit breakers and current interruption equipment, gas-insulated transmission lines, gas-insulated transformers, and gas-insulated substations. When the gas recovery and charge apparatus is connected to the electrical equipment device  5 , pump  10  is in communication with the electrical equipment device  5  and is capable of evacuating the electrical equipment device  5 . 
     In order to evacuate the electrical equipment device  5 , valve  20  must be selected to operate in a collection state. When valve  20  is in a collection state, pump  10  evacuates the insulation gas from the electrical equipment device  5 , through an optional gas drying system  30  and an optional filter  25  into an inflatable collection device  15 . The inflatable collection device  15  can be made from any gas impermeable material; however the material should be flexible to aid in the transfer of the collection device  15  both when the inflatable collection device  15  is empty and full of insulation gas. Because the inflatable collection device  15  is able to hold all or substantially all of the insulation gas contained in the electrical equipment device  5  in a gas state, the insulation gas can be quickly transferred to a second electrical equipment device without first converting the gas into a liquid storage state. Another advantage of having the insulation gas held in the gas state in collection device  15  is that routine maintenance can be performed on the electrical equipment device  5 , or any instrument where the insulation gas in the electrical equipment device  5  is in communication with the instrument, without converting the insulation gas into a liquid storage state. 
     When the bulk of the insulation gas is removed to the collection device  15 , valve  20  can be closed so that a second pump  40  can more fully evacuate the electrical device  5  to outside vent  45 . 
     In the event the insulation gas is ready to be re-charged into the electrical equipment device  5 , valve  20  is selected to operate in a charge state and pump  10  is used as a pressure pump to return the gas in the collection device  15  back to the electrical equipment device  5 . When the gas recovery and charge apparatus are no longer needed the apparatus can be disconnected from electrical equipment device  5  and moved to a second electrical equipment device. 
       FIG. 2  represents schematically a second embodiment of the invention comprising additional valves and a relief system. Referring now to  FIG. 2 , initially the system can be considered to have electrical equipment device  5  fully charged with insulation gas, e.g., 10 psig of SF 6 , and where all valves are closed and the pumps are off. 
     Gas recovery is initiated when valves  67 ,  64 ,  63 ,  62  and  61  are opened equalizing pressure between the electrical equipment device  5  and the inflatable collection device  15 . When the electrical equipment device  5  is at or near 0 psig, valve  67  is closed and valves  66  and  65  are opened. When valves  66 ,  65 ,  64 ,  63 ,  62  and  61  are open the insulation gas recovery and charge apparatus is in a recovery or collection state. When pump  10  is activated insulation gas is directed from the electrical equipment device  5  to the inflatable collection device  15 . The electrical equipment device  5  is evacuated to approximately 10 Torr and all valves are closed. 
     The electrical equipment device  5  is typically in communication with an instrument  50  that receives electrical power from the electrical equipment device  5 . The instrument  50  will also contain some amount of insulation gas. Instrument valve  69  can optionally be opened to back fill the electrical equipment device  5  with instrument air. As the electrical equipment device  5  equilibrates to near 0 psig with the instrument air, the instrument valve  69  can be closed and the electrical equipment device  5  can be safely opened to the atmosphere for inspection. The electrical equipment device  5  can be optionally vented by having all valves closed and opening valves  66  and  68 . Pump  10  when activated will evacuate the electrical equipment device  5  venting to the outside  45 . 
     As the electrical equipment device  5  reaches sub-atmospheric conditions, e.g., 10 Torr, valves  66  and  68  can be closed and pump  10  can be turned off. If desired, the electrical equipment device  5  can now be recharged with insulation gas. The insulation gas recovery and charge apparatus can be selected to operate in a fill or charge state by opening valves  67 ,  64 ,  63 ,  62 , and  61 . This will cause the insulation gas in the inflatable collection device  15  to equilibrate with the electrical equipment device  5  returning the electrical equipment device  5  to near atmospheric pressure, approximately 700 Torr. At this time valves  62  and  63  can be closed, leaving open valves  67 ,  64  and  61 , a second pump  40  can be used to evacuate the inflatable collection device  15  and thereby recharge the electrical equipment device  5  with insulation gas. When the electrical equipment device  5  reaches super-atmospheric conditions, e.g., 10 psig, all the valves can be closed, the pump can be turned off and the electrical equipment device  5  is insulated and ready for high voltage conditions. In the event the electrical equipment device  5  is overcharged, e.g., exceeding 12 psig, the system can optionally contain a relief valve  60  that can be used to return insulation gas back to the inflatable collection device  15 . 
     Details hereinabove recited are provided to enable a fuller understanding of the invention. It will be understood, however, that such details except as required by the expressions in the claims should not be construed as a limitation of the invention.