US 3424884 A
Description (OCR text may contain errors)
D. r-*LolassralfA ETAL.
INVENTORS D/eer 4/oessel. Gerhard. Maui/*xe n ATroRNEYs Jan. 28, 1969 D. FLoEssi-:L ETAL 3,424,884
CONTACT ARRANGEMENT FOR GAS-BLAST CIRCUIT BREAKERS Filed Nev. 24, 1965 sheet Z ef e INVETORS Die? fer F/oessel. Gerhard /Yauhe ATTORNEYS United States Patent O 16,555/ 64 U.S. Cl. 200-148 Int. Cl. H01h 33 82 4 Claims ABSTRACT OF THE DISCLOSURE A contact arrangement for a gas blast circuit breaker comprises two coaxially arranged nozzle tubes located at a fixed distance apart and a slidable contact bridge which serves to make and break the electrical connection between the fixed nozzle tubes. The contact bridge is provided with a cylindrical array of Contact ngers and also a ring electrode located in advance of the leading ends of the contact fingers which functions as a temporary anchor point for one end of the arc prior to reaching its ultimate anchor point on the nozzle tube, the arc end shifting from the moving contact fingers to the ring electrode and thence to the nozzle tube.
The invention relates to gas blast circuit breakers of the type in which the actual switching takes place between two slotted nozzle tubes arranged at a fixed distance from one another and provided with a common bloweout valve, and in which there is a movable bridging contact in the form of a tulip contact sleeve for connecting the two nozzle tubes, the sleeve being composed of cylindrical array of contact fingers arranged in a tubular body open at one end which forms the movable part of the blow-out valve.
In such gas blast circuit breakers, for breaking the circuit, the movable bridging contact is moved back over a first nozzle tube so that the arc resulting from the break ing of the circuit is drawn first between the second nozzle tube and a contact finger of the movable bridging contact, and is then driven into the interior of the nozzle tubes by the resulting gas blast, the foot of the arc springing from the contact finger onto the first nozzle tube. The contact fingers are arranged inside a tubular body which constitutes the movable blowout valve part and cooperates with a valve seat on the opposite nozzle tube. This contact arrangement allows the blowing of the resulting arc to begin at once and creates very favorable conditions for the extinction of the arc resulting from the opening of the contact arrangement in a given nominal breaking current range. However, at network and super network voltages there are requirements for contact arrangements capable of dealing with yet higher currents. Thus, as soon as the effective value of the current to be swtiched reaches or exceeds 60 ka., care must be taken that the geometry of the parts through which the current ows does not have any undesired effect on the arc so that, for instance, instead of the arc being forced inside the nozzle tube it is thrown radially outwards. A prior proposal has also been made to provide nozzle-shaped hollow contacts with radial slits in order to compel the current, when the arc has taken footing on a segment between two slits, to flow radially inward against the arc so that the magnetic effect is increased and causes the arc to move inwards. This effect only occurs, however, with a double nozzle arrangement if both feet of the arc are already on the nozzle tubes.
It is proposed in accordance with the invention that a ring electrode with radial slits should be fixed on the tu- Patented Jan. 28, 1969 bular body of the bridging contact towards its open end in front of the contact lingers, the internal diameter of the ring electrode being greater than the outer diameter of the nozzle tubes. This has the advantage that the arc is subjected to magnetic blowing towards the axis of `the nozzle tubes while during the formation of the arc it is subjected to a high velocity gas ow. Outward movement of the arc is thus reliably prevented.
The invention will now be further described by way of example with reference to the accompanying drawings, in which:
FIG. l is a longitudinal section through a contact arrangement, in accordance with the invention, in an intermediate position;
FIG. 2 shows the contact arrangement of FIG. l in the fully open position;
FIG. 3 is a side View of the contact arrangement on line A in FIG. 2;
FIG. 4 shows a second embodiment of the invention.
In FIGS. l to 3, reference numerals 1 and 2 denote two fixed nozzle tubes whose adjacent portions have radial slits 3 and 4 which, owing to the provision of axial slots 5 and 6 produced by machining, have a U-shaped crosssection. The nozzle tube 1 has a plate-like widened flanged portion 7 for receiving the blow-out valve seat 8. The nozzle tube 2 is surrounded by a tubular body 9 open at one end. A piston-like part 10 of this tubular body slides in a cylinder 11. Mounted within the tubular body 9 there are a number of contact lingers 12 acted upon by leaf springs 13 to produce the radially inward pressure necessary for contact. Towards the open end of body 9 a ring electrode 14 is placed in advance of the leading ends 12a of the contact fingers 12. This ring electrode is firmly connected with the tubular body 9 and is provided with 'a number of radial slits 15. The inner diameter of the ring electrode 14 is greater than the outer diameter of the nozzle tubes so that a ring-shaped channel results.
The manner of operation of the arrangement is as follows: In the closed position of the contact arrangement, the left end (as seen in FIGS. 1 and 2) of the tubular body 9 rests firmly against the valve seat 8 under the action of a spring 16. In this position the switch chamber 17, which surrounds the. contact arrangement and is always kept filled with gas under pressure, is not in communication with the `bores of the nozzle tubes 1 and 2, which are connected with the atmosphere; that is, the tubular body 9 serves simultaneously as a movable blowout valve part. The leaf springs 13 acting against the outer `faces of the contact fingers 12 press the latter against the left-hand nozzle tube 1. For opening the circuit, the space 18 above the channel 19 is evacuated using a control valve which is not shown since it is of a known type. The tubular body 9 is thereby moved to the right due to the action of the gas under pressure in the space 17 on the left side of the piston 10. At the beginning of the movement the tubular body 9 moves and its left end face is lifted from the seat 8 so that gas under pressure from the space .17 reaches the points of contact between the contact fingers 12 and the nozzle tube 1 before the contact fingers leave the latter. Subsequently, as the opening movement continues, the contact fingers 12 break contact with the nozzle tube 1, and an arc 20 is formed, for example, as shown in FIG. l, between the upper segment of the nozzle tube and the neighboring contact fingers. The path of the current is shown by broken line 21 and has a slightly curved path in the region of the parts that have been separated. Simultaneously the arc 20 is Iblown in a longitudinal direction by high velocity gas blowing through the ring-shaped channel between the parts 1 and 14. While the distance between the parts 1 and 12 steadily increases as the arrangement is moved to break the circuit, the distance between the parts 1 and 14 remains for a substantial period substantially constant so that approximately in the position shown in FIG. l, or somewhat before, the arc end which had been Aanchored on the contact fingers 12 jumps to the ring electrode 14. The path of the current then is in accord-ance with the broken line 22 so that there is a strong magnetic influence on the arc 23 urging it towards the axis of the nozzle tubes. Owing to this the arc rapidly switches so that its righthand footing moves to the nozzle tube 2. This switching of the arc is facilitated by the clearance between the two nozzle tubes 1 and 2 which, owning to ionization of the gas used in the switching arrangement, becomes strongly conducting. The ring electrode 14 also has the advantage of preventing undesired spreading of metal vapor in an outward direction and thus protecting the parts 8 and 9 of the blow-out valve.
FIG. 2 shows how the arc, after it has been moved to the nozzle tube 2, is caused by the magnetic blow-out to pass quickly through the intermediate phases 24, 25, and 26 into the interior of the nozzle tubes where finally it is cooled and extinguished by the now fully effective pressure gas blast.
As shown in FIG. 4, the ring electrode 14 can, on the side away from the contact lingers, be provided with a ring 27 of insulating material in order to `achieve better screening of the flow-out valve parts and to extend the annular gas channel 28 so that the blowing effect of the pressurized gas is more effective in the axial direction. Also for improving the resistance of the nozzle tubes 1 and 2 to burning, the inner faces turned towards one another can be coated with arc-resistant material 29, 30. These coatings 29 and 30 can, provided they are of a material such as tungsten with a substantially greater electrical resistance than the material of the nozzle tubes themselves, for example copper, be unslotted without the magnetic blowing effect being substantially reduced.
1. A contact arrangement for a gas blast circuit breaker comprising first and second slotted coaxially positioned electrically conductive metallic nozzle tubes arranged at la fixed distance from each other, a contact bridge structure including a tubular body surrounding said nozzle tubes and which also forms part of a blow-out valve for the circuit breaker, a cylindrical array of contact fingers secured within said tubular body and which fare spring loaded to engage said nozzle tubes, said tubular body and the Contact fingers therein being mounted on said first nozzle tube for movement towards and away from said second nozzle tube thereby to establish land interrupt, respectively the electrical connection between said nozzle tubes, and a radially slotted ring electrode mounted on said tubular body in advance of the leading ends of said contact fingers, said ring electrode serving as a temporary anchoring point for one end of the arc drawn from said second nozzle tube and which is transferred to said ring electrode from said contact fingers during movement of said contact bridge prior to ultimate anchoring of said -arc end upon said first nozzle tube.
2. A contact arrangement as defined in claim 1 and which further includes a ring of insulating material mounted upon said ring electrode Aat the side thereof facing said second nozzle tube.
3. A contact arrangement as defined in claim 1 and wherein said first and second metallic nozzle tubes are provided on their inner faces and their adjacent end faces with -a non-slotted coating of a metallic arc-resistant material having a substantially greater ohmic resistance characteristic than the metal from which said nozzle tubes `are made.
4. A contact arrangement as defined in claim 3 wherein said nozzle tubes are made from copper and said metallic arc-resistant coating material is tungsten.
References Cited UNITED STATES PATENTS 3,240,910 3/1966 Floessel 20G- 148.2
FOREIGN PATENTS 1,147,649 4/ 1963 Germany.
ROBERT S. MACON, Primary Examiner.