Valve regulating means disposed between HV switching apparatus and over voltage arresting mechanism maintaining pressure differential therebetween
Unlted States Patent 11 1 1111 3,881,138 Luxa et al. 1 1 Apr. 29, 1975 VALVE REGULATING MEANS DISPOSED 3.280.376 I 10/1966 Person 317/70 x BETWEEN Hv SWITCHING APPARATUS 3.378.731 4/1968 Whitehead... 317/103 3.566.062 2/1971 Meier et 200/145 R X AND OVER VOLTAGE ARRESTING 3.566.183 2/1971 Olsen et 111.... 317/70 x MECHANISM MAINTAINING PRESSURE 3.622.725 11/1971 McConnc|l.... 200/148 B x DIFFERENTIAL THEREBETWEEN 3.733.521 5/1973 Kalb 317/70 3.743.804 7/1973 Frowcin 317/103 X I75] &#34;Vemors: Werner Jaksz&#34; both 3.777.218 12/1973 Kesslcr 317/71 x of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,  
  Germany Primary E.\&#39;am1&#39;nerlames R. Scott Attorney, Agent, or FirmKenyon &amp; Kenyon Reilly [22] Filed. July 2, 1973 c &amp; Chapin [21] Appl. No.: 375,518  
 [30] Foreign Application Priority Data July 14, 1972 Germany 2235514 [57] ABSTRACT [52] U.S. Cl. 317/59; 200/148 B; 200/148 E; An improved voltage Overload arresting apparatus for 317/71; 317/103 a high-voltage switching system in which the housings [51] Int. Cl H02h 1/00; H01h 33/80 of the ing pp ratus nd he switching system [58] Field of Search 317/69, 70, 103, 59, 60, are coupled by a reduction valve which maintains the 317/71; 200/145 R, 146 A, 146 AA 148 B, pressure of a dense gaseous insulating medium in the 148 E 148 R arresting apparatus housing at a constant pressure which is less than the gas pressure in the switching sys- [56] References Cited tem housing.  
 UNITED STATES PATENTS 3.072.828 1/1963 Goffaux 317/70 X 10 Claims, 4 Drawing Figures PATENTEflAFazsiazs 3,881,138  
 SHEET 20F 2 Fig. 2  
 FILTEEI Z4 III- Fig.3  
 FILTE Fly SPARK GAP l VALVE REGULATING MEANS DISPOSED BETWEEN HV SWITCHING APPARATUS AND OVER VOLTAGE ARRESTING MECHANISM MAINTAINING PRESSURE DIFFERENTIAL THEREBETWEEN BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to high-voltage switching systems, and in particular, to a high-voltage switching system of the type utilizing a dense, gaseous insulating medium which includes an improved voltage overload arresting apparatus.  
 2. Description of the Prior Art German Auslegeschrift Pat. No. 1,241,514 discloses a high-voltage switching system which is encapsulated in a metal housing and includes a spark gap. The housing is filled with a dense, insulating gas, such as. for example. sulfur hexafluoride, in which gaseous insulating medium the spark gap operates. Improved switching systems of the type described above generally include voltage overload arresting apparatus which comprise both a spark gap and an arrangement of voltage dependent resistors which limit current surges. It is known, as taught by US Pat. No. 2,757,26l, that improved performance of a voltage overload arresting apparatus can be obtained by filling the housing thereof with sulfur hexafluoride. The correlation between the pressure of the gas in the voltage overload arresting apparatus housing, and the ratio of the breakdown voltage to the quenching voltage, especially when sulfur hexafluoride is usedas the insulating medium. has. however, not been appreciated by the prior art.  
 SUMMARY OF THE INVENTION It is therefore an object of the invention to provide an improved high-voltage switching system voltage overload arresting apparatus in which the pressure of a gaseous insulating medium in the arresting apparatus housing is controlled with respect to the pressure of the same gaseous insulating medium in the switching system housing.  
  Accordingly, the invention provides, in a highvoltage switching system of the type described above, regulating means, coupled to the housing of the switching apparatus at one end, and to the housing of the voltage overload arresting apparatus at the other end thereof, for regulating the pressure within the housing of the arresting apparatus so as to maintain the pressure of a gaseous insulating medium therein at a constant pressure which is less than the pressure of the same gaseous insulating medium in the housing of the switching system. In one embodiment of the invention, the regulating means comprises a reduction valve coupled to the switching system housing and the voltage overload arresting apparatus housing. A filtering means and pump may also be coupled to a line connecting the housings, for purifying the gaseous insulating medium flowing from the switching system housing to the voltage overload arresting apparatus housing. In another embodiment of the invention, the arresting apparatus housing includes a separate sealed chamber fora spark gap, and another sealed chamber for a voltage dependent resistor arrangement thereof. The chambers in which the resistors are disposed may also be separately coupled to the housing of the switching system by means of a suitable connecting line. and preferably includes a check valve which prevents contaminated gas from flowing into the switching system housing. In still another embodiment of the invention, the spark gap of the arresting apparatus is divided into a pair of spark gaps. one of which comprises an ignition spark gap, disposed in separate sealed chambers. A contact breaker device is coupled to the ignition spark gap for triggering the apparatus when a voltage overload occurs.  
 DESCRIPTION OF THE DRAWINGS In the drawings, wherein similar reference numerals denote similar elements throughout the several views thereof:  
  FIG. 1 is a schematic side view, partially in section, of a high-voltage switching system, including an improved voltage overload arresting apparatus constructed according to the invention;  
  FIG. 2 is a schematic illustration of one embodiment of an improved voltage overload arresting apparatus constructed according to the invention;  
  FIG. 3 is a schematic illustration of another embodiment of an improved arresting apparatus constructed according to the invention, wherein the arresting apparatus housing is divided into separate chambers for containing the voltage dependent resistors and the spark gap of the arresting apparatus; and  
  FIG. 4 is a schematic illustration of still another embodiment of an improved arresting apparatus constructed according to the invention, which utilizes an ignition spark gap as part of the arresting apparatus.  
 DETAILED DESCRIPTION Referring now to the drawings, FIG. 1 illustrates a high-voltage switching system having a metal housing and a voltage overload arresting apparatus coupled thereto. The system includes a three-phase dual bus bar system (which may be, for example, I I0 kV) including bus bars 1 and 2 and circuit breakers 3 and 4 coupled thereto. The circuit breakers are coupled to each other by a feed line 5. Terminal 7, which may be connected to an electrical cable distribution line, is coupled by feed line 6 to the circuit breakers and bus bars. Conductor 8 is coupled to the feed line 5 and connects terminal 7 to circuit breakers 3 and 4. A voltage overload arresting apparatus 9 is disposed beneath the housing 10 of the high-voltage switching system and is coupled thereto by a pressure resistant line 13. The arresting apparatus is also electrically connected to conductor 8 in housing 10 by another conductor.  
  Interior space 11 of switching system housing 10, and interior space 14 of arresting apparatus housing 12, are also coupled to each other by means of a line 15. Regulating means 16 is coupled to the line and regulates the pressure of the gaseous insulating medium in housing 12 of the arresting apparatus relative to the pressure in housing 10 of the switching system. The regulating means may, for example, comprise a reduction valve which may simultaneously prevent backflow of gas from housing 12 to housing 10 when an overload occurs and the pressure in housing 12 rapidly increases.  
  One embodiment of the improved arresting apparatus is illustrated in FIG. 2. In this embodiment, housing 10 is coupled to housing 12 by means of a line 23, and a filtering means shown as filter 24, is disposed between the housings and coupled to the line. The gaseous insulating medium flows through line 23 from housing 10 to housing 12 through filter 24 which, in combination with a pump 21, ensures that the gas is purified before it is admitted to the arresting apparatus housing: This filtering process carried out by pump 21 and filter 24 ensures that the breakdown voltage of the spark gap of the arresting apparatus is maintained at a constant voltage level. Reduction valve 22 operates to maintain the pressure inthe arresting apparatus housing 12 at a constant pressure which is slightly below that of the pressure in the switching system housing 10. Pump 21 and valve 22 are coupled to housing by line 20.  
  Inthe embodiment of the invention illustrated in FIG. 3, arresting apparatus includes a separate chamber 31 in which spark gap 32 is disposed, and an additional chamber 33 in which the voltage dependent resistors 34 are disposed. The spark gap utilized throughout the various embodiments of the invention comprises a known series connection of individual spark gaps, and the voltage dependent resistors are formed &#39;bya column of individual resistor elements. The separation of the housing into sealed chambers in this embodiment prevents decomposition products,  
 which are formed when a voltage overload occurs by the burning of the insulating gas, from flowing into the &#34;switching system housing Y10 and contaminating the gaseous atmosphere therein. As in the previously described embodiment of the invention, a pump and a reduction valve are coupled by means of line 35 to the arresting apparatushousing and the switching system housing. ln thisembodiment, chamber 31 is sealed, and  
 the pressure is regulated as previously described by the reduction valve. A filtering means is also coupled by a line 36 to the switching system housing and arresting apparatus chamber 31. Chamber 33, in which the voltage dependent resistors 34 are disposed, is sealed and is-filled with the same gas utilized as a gaseous insulating medium in housing 10, namely, sulfur hexafluoride,  
 . at a pressure which is higher than the pressure in chamber 31. The dielectric strength of the arresting apparatus is thus improved, especially under large pulse currents, since the insulating capacity of the gas increases as the gas pressure increases. Flashover is thus prevented. Chamber 33 is coupled by means of line 37 to housing 10 of the switching system, which line includes a check valve 38 coupled thereto. The line equalizes the pressure in chamber 33 and in housing 10, and the check valve prevents contaminated gas from being forced into housing 10 upon the occurence ofa voltage overload.  
  ln the embodiment of the invention illustrated in FIG. 4, voltage arresting apparatus 40 includes a separately sealed chamber 41 for the voltage dependent resistors of the arresting apparatus. The spark gap of the gap in a known manner. Chamber 41, in which the voltage dependent resistors are disposed, may be connected to the interior of housing 10 of the switching system as described in the previous embodiments of the invention. Chamber 45, in which spark gap 43 is disposed, contains a gaseous insulating medium which is [different than that used as an insulating medium in switching apparatus housing 10, such as, for example,  
 nitrogen. The breakdown voltage of spark. gapi, 43 is thus lower than the breakdown voltage of sparkgfap 42,  
 and, as a result, automatic triggering of&#39;the spark gap is achieved. Controlled firing of the voltage&#39;arresting apparatus, and precise control of the voltage breakdown levels, are obtained. 1  
  It should be noted that the several illustrated divisions of the voltage arresting apparatus housing into separate chambers can be combined with&#39; feature&#39;s of the other embodiments of the inventionflt isirnportant only that the main portion of the spark gap of the apparatus be surrounded with the insulating gaseous medium utilized in the high-voltage switching system housing at a constant and at a reduced pressure, so that the desired breakdown voltage/quenching&#34;voltage ratio is obtained.  
 While there have been described herein what are I considered to be preferred embodiments of the invention, it will be clear to those persons skilled in the art that many changes and modifications may be made thereunto without departing from the invention, and it is therefore intended in the appended claims to include all such changes and modifications as fall within the true spirit and scope thereof.  
 What is claimed is:  
  1. In a high voltage switching system, of the type including a switching system housing in which a dense gaseous insulating medium is disposed under pressure, and a voltage overload arresting apparatus including a housing, having at least one first sealed chamber coupled to the switching system housing,also containing said dense gaseous insulating medium, and at least one spark gap, and voltage dependent resistance means, disposed in said arresting apparatus housing, the improvement comprising regulating means including valve means, coupled to the switching system housing and to said arresting apparatus housing, for maintaining the pressure of said gaseous insulating medium in said chamber at a constant pressure which is less than the pressure of said gaseous insulating medium in the switching system housing.  
  2. The apparatus as recited in claim 1, wherein said regulating means valve means comprises a reduction valve coupled to the switching system housing and said chamber of said arresting apparatus housing.  
  3. The apparatus as recited in claim 2, wherein said regulating means comprises said reduction valve in combination with a check valve for preventing the flow of said gaseous insulating medium from said arresting I apparatus housing to the switching system housing.  
  4. The apparatus as recited in claim 2, further comprising filtering means, and a pump, coupled to the switching system and said arresting apparatus housings, for purifying gas flowing from the switching&#39;system housing into said arresting apparatus housing.  
  5. The apparatus as recited in claim 4, wherein said arresting apparatus housing further comprises a second sealed chamber in which said voltage dependent resistance means is disposed, said spark gap being disposed in said first housing chamber, and said pump, valve, and filtering means being coupled to said first chamber.  
  6. The apparatus as recited in claims, wherein said second housing chamberis coupled t&#39;othe&#34; switching system housing by aline for filling said sec o nd&#39;c har nber with the gaseous insulating medium in the switching system housing to &#34;a pressure equal to &#39;the pressure in the switching system housing. J  
  7. The apparatus as recited in claim 6, further comprising valve means, coupled to said line, for preventing flow of the gaseous insulating medium from said second chamber to the switching system housing.  
  8. The apparatus as recited in claim 1, wherein said arresting apparatus housing includes a second sealed chamber, first and second spark gaps being disposed in said first and second chambers. respectively. and a third sealed chamber in which said voltage dependent resistance means is disposed, and further comprising a line coupled to the switching system housing and one of said first and second chambers, filtering means coupled to said line for purifying said gaseous insulating medium flowing through said line into said arresting ap paratus housing, said other of said first and second chambers containing a gaseous insulating medium which is different than the gaseous insulating medium in the switching system housing.  
  9. The apparatus as recited in claim 8, wherein said spark gap disposed in said other of said first and second chambers comprises an ignition spark gap.  
  10. The apparatus as recited in claim 9, further comprising contact breaker means, coupled to said ignition spark gap, for triggering said spark gap upon the occurrence of a voltage overload.