US2255198A

US2255198A - Multiple break gas blast circuit breaker

Info

Publication number: US2255198A
Application number: US385170A
Authority: US
Inventors: Thommen Hans
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1940-03-09
Filing date: 1941-03-25
Publication date: 1941-09-09
Anticipated expiration: 1958-09-09
Also published as: GB552091A; BE440805A; FR869992A; CH218998A

Description

Sept. 9, 1941. H. THOMMEN MULTIPLE 'BREAK GAS BLAST CIRCUIT BREAKER Filed March 25, 1941 3x1/vanto@ Patented Sept. 9, 1941 MULTIPLE BREAK GAS BLAST CIRCUIT BBEAKEB.

Hans Thommen, Baden,

Aktiengesellschaft Switzerland, assignor to Brown,

Boverl, Cie.,

Baden, Switzerland, a joint-stock company Application March 25, 1941, Serial No. 385,170 In Switzerland March 9, 1940 7 Claims.

'I'his invention relates to circuit breakers and 'y more particularly to multiple break gas blast circuit breakers.

'I'here is a non-uniform voltage distribution along the several current interrupting points of a multiple break circuit breaker-ofy the type having a plurality of arcing contacts electrically and spatially in series. 'I'hls unevenl voltage distribution is particularly disadvantageous in circuit breakers in which the arcing contacts are subjected to a blast of gas under pressure to extinguish they arcs, since it results in a decrease in the rupturing capacity of the circuit breaker and an increase in the consumption of the arcextinguishing medium. In order to overcome these disadvantages and to improve the capacity of the circuit breaker it has already been 'proposed that resistors or capacities be connected in parallel with each arc-f ing contact gap. When the circuit breaker is opened, the residual current through the impedances is quite small and may be interrupted for instance by a voltage isolating switch arranged in series with the multiple interruption points. The aforementioned impedances or damping means are located either inside or outside of the switch chambers enclosing the arcing contacts and can be constructed as integral part of the switch chambers themselves or as separate devices to be iixed to the chambers.

A'n object of the present invention is to improve the rupturing capacity of gas blast circuit breakers with multiple interruption by other very simple means and at the same time to achieve a more economical operation of the apparatus. According to the invention, this is attained by dlmensioning each point of current interruption for a different rupturing capacity, so that those points oi' interruption which are subjected to the highest stresses when opening the circuit are dimensioned for the largest rupturing capacity.

In some cases it is suiiicient if, in circuit breakers having a plurality of switching points arranged in series, only the sets of arcing contacts at each end of the breaker are dimensioned for a higher interrupting capacity than the remaining ones of the series. It is, however, also possible to design the circuit breaker so that at each end the two outer switching points are dimensioned for a higher rupturing capacity than the remaining contact points. The rupturing capacity of the various switching points can also be uniformly graded. This grading is achieved according to the invention by constructing the outer or end points oi' interruption so as to be,

(Cl. 200-148) I capable oi dealing with the highest voltages to,

be interrupted while the remaining points oi interruption are so dimensioned that their rupturing capacity decreases uniformly from both ends towards the center oi the circuit breaker.

The rupturing capacity lat each point of cury rent interruption is determined .by the size oi the arcing contacts and the stroke of the movable contact. For instance, in order to increase the rupturing capacity of an interruption point in a circuit breaker provided with hollow arcing contacts, the bore 'of the hollow contact and/or the contact can be correspondstroke of the movable ingly increased.

By designing the points cl2-interruption in the manner described so as to have dierent -dlmensions, it is possiblev to ensure that when extinguishing the arcs each switch element or point of interruption requires only an amount of pressure gas suiiicient for the rupturing'capacity in question; there is therefore no waste as regards the arc-extinguishing medium. Furthermore, it is also possible to strengthen the insulation of the switch elements in accordance with the power to be interrupted.

- The objects and advantages of the invention will be apparent iromrthe following specication when taken with the accompanying drawing in whichz- Fig. 1 is a somewhat diagrammatic vertical central section through an embodiment of the, invention;

Fig. 2 is a fragmentary vertical section, on an enlarged scale, through the lower arcing chambers oi the Figs. 3 and 4 are diagrammatic central vertical sections through other embodiments of the invention.

As shown in Fig. 1, a multiple break circuit breaker of the general type contemplated by the invention may comprise a series of vertically arranged arcing chambers, identified generally byv reference numberals ia to lg, respectively. that each house a set of gas blast arcing contacts. Hollow insulators 2 form the outer walls of the several chambers, and metal plates or castings 3 each restupon one insulator and support the next higher insulator to form'the transverse walls that separate the chambers from each other. The line connections L, L are made to a terminal 4 of the cap member 5 that rests upon the top plate l, and to the base casting I that forms the lower wall of the end arcing chamber la.l The base l is mounted at the top o! a hollow insulator column, not shown, through which a pressure circuit breaker of Fis'. 1; and v gas is supplied to separate the arclng contacts and to extinguish the arcs drawn between the separating contacts. The pressure gas enters the end chamber la through openings 'l in the base 6, and flows from one chamber to the next through ports 8 in the transverse wall plates I.

Each plate 3 has a passage 9 extending laterally from the outer edge of the plate to the centrai part where it opens downwardly through a nozzle contact that cooperates with a movable pin contact carried by the next lower plate l or, in the case of the end chamber la, by the base plate 8. The nozzle contacts and the movable pin contacts of the several arclng chambers la to ig are identified by reference lila- Illy and ila-iig, respectively.

In the embodiment shown inFigs. l and 2, the power rupturing capacities of the cooperating arclng contacts of all intermediatearcing chambers Ib-If are the same, and only the end arcingv chambers la and Ig are designed for a greater rupturing capacity. The several transverse wall plates 3 are preferably of identical. design, as shown in Fig. 2, and the dimensions of the several nozzle contacts are varied by a selection of the nozzle bushings I2a, |21), etc., that are threaded into the nozzle openings of the metal plates 3. The contour of the cooperating pin contacts is adjusted to conform to the-geometry of the diierent nozzle contacts by interchangeable caps |30., I3b, etc., that are threaded upon the ends of the movable contacts. The movable contacts are slidable in cylinders i4 that project above the base B and all plates 3 except the top plate. 'I'he movable contacts are normally retained in circuit closing position by springs I5 and are forced downward by pressure gas admitted to the several arclng' chambers. are mounted within the cylinders I4 to limit the opening movement of the several pin contacts. The stop pins I 6a and |60 of the end chambers are somewhat shorter than the stop pins lib to |6f of the intermediate arclng chambers.

Inspection of Fig. 2 will show that the nozzle contact bushing I2a has a substantially larger numerals bore than that of the next higher nozzle contact bushing I2b. The lowermost arclng chamber therefore has a greater rupturing capacity than the adjacent arclng chamber. Similarly. the power interrupting capacity of the cooperating contacts log, Hg of the top arclng chamber is greater than that of the next lower and'all intermediate arclng chambers. y

The general structure of the circuit breakers of Figs. 3 and 4 is similar to the Fig. 1 embodiment, but the several embodiments differ from each other in the design of the relative power rupturing capacities of the several sets 0f arclng contacts. Corresponding reference numerals are applied to those elements of Figs. 3 and 4 that are, or may be, identical with the similar parts of Fig. l.

In the Fig. 3 embodiment, the two outer sets of arclng contacts at each end of the circuit breaker are designed for one rupturing capacity, and the intermediate sets of contacts are designed for a smaller rupturing capacity. The cooperating nozzle contacts I0 and movable pin contacts li of the end chambers Sla, lib and llf, Sig

- are therefore somewhat larger than the sets of nozzle and pin contacts Il', Il', respectively, of the intermediate arclng chambers llc to Sie.

In Fig. 4, 4the rupturing capacities of the se- 4 la are progressively graduated from a maximum acompa value at the outer sets of contacts to a mlnimumvalue for the arclng contacts of the central arclng chamber lid. This progressive grading of the dimensions of the nozzle contacts 42o- 42g oi* the type in which impedances were shunted across the points of circuit interruption to establish a preselected voltage gradient along the several arclng contacts. The breakers are opened by admitting a pressure gas to the arclng chambers through the openings 1 of the base plate i. The pressure gas hows upwardly through the ports l, and forces the several pin contacts away.y from the cooperating nozzle contacts. The pressure gas then escapes through the nozzle contacts and lateral passages as high velocity blasts that extinguish the arcs. The voltage gradient along .the series of gaps is not uniform when the arclng contacts open under load but, as described above, the several sets of arcing contacts are designed for a higher rupturing capacity at .the points of higher electrical stress. Relativelyl large quantities of the pressure gas are discharged across and around the relatively high power arcs that are drawn between the outer sets of arclng contacts, and lesser quantities of pressure gas are used to extinguish the lower power arcs that are drawn between the intermediate sets of `arclng pin contacts. Greater design latitude is had Stop pins ries of arclng contacts within the chambers l Iawhen both of these factors are variable, but it is to be understood that the contacts may be designed for a change in only the bore size o'f the nozzle contact or only the stroke of the pin contact.

I claim: 1

1. A multiple break gas blast circuit breaker of the type including a plurality of sets of cooperating arcing contacts arranged electrically and spatially in series, terminal connections for an electrical line at the outer contacts of said serially arranged'sets. one contact of each set being movable by pressure gas to separate that contact from the cooperating contact and one contact of each set being a nozzle contact through which the pressure gas escapes as an arc-extinguishing gas upon the separation of the cooperatlng contacts, characterized by the fact that the sets of arcing contacts at each end of the series include means for establishing through the nozzle contacts thereof arc-extinguishing blasts of greater power rupturing capacity than the arcextinguishing blasts established through the noz.- zle contacts of the intermediate sets of arclng contacts.a

2. A multiple break gas blast circuit breaker of the type including a plurality of sets of cooperating arcing contacts arranged lelectrically and spatially in series, one contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to separate the cooperating contacts, characterized by the fact that the nozzle contacts of the cooperating sets of contacts at the outer ends of the series have bores of larger size than the bore of the nozzle contact of an intermediate set of cooperating contacts.

3. A multiple break gas blast circuit breaker of the type including a plurality of sets of 'cooperating arcing contacts arranged electrically and spatially in series, one v*contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to separate the cooperating contacts, characterized by the fact that the nozzle contacts of 'each outer set of cooperating contacts at the respective ends oT the series have bores of larger size than the bores of the nozzle contacts of all intermediate sets oi cooperating contacts. v

4. A multiple break gas blast circuit breaker of the type including a plurality ol sets of cooperating arcing contacts arranged electrically and spatially in series, one contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to Vseparate the cooperating contacts, characterized by the fact that the nozzle contacts of the two outer sets oi cooperating contacts atl the respective ends of the series have bores of larger size than the bores of the nozzle contacts of all intermediate sets of cooperating contacts.

5. -A multiple break gas blast circuit breaker of the type including a plurality of sets of `cooperating arcing contacts arranged electrically and spatially in series, one contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to separate the cooperating contacts. characterized bythe fact that the nozzle contacts of the several sets than the opening of cooperating contacts have bores that vary in size progressively from a maximum at the outer nozzle contacts to a minimum at the centrally located nozzle contact.

6. A multiple break gas blast circuit breaker of the type including a plurality of sets of cooperating arcing contacts arranged electrically and spatially in series, one contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to separate the cooperating contacts, characterized by the fact that means is provided to limit theopening move- .ment of the movable contacts of the intermediate sets of cooperating contacts to a lesser value movement of the movable contacts of the outer sets of cooperating contacts.

7. A multiple break gas blast` circuit breaker of the type including a plurality oi'vsets of cooperating arcing contacts arranged electrically and spatially in series,l one contact of each set being a nozzle contact and one contact of each set being movable by pressure gas to separate the cooperating contacts, characterized by the fact that means is provided to limit the opening movement of the movable contacts of the intermediate sets of cooperatingcontacts to a lesser value than the opening movement of the two outer sets of cooperating contacts at reach end ofwthe series.

a HANS mom/IEN.