US2735040A - Electric apparatus having a - Google Patents

Description

Feb. 14. 1956 A. M. OPSAHL 2,735,040

ELECTRIC APPARATUS HAVING A PROTECTIVE GAP Filed Feb. 8, 195] F lnsullution WITNESSES: INVENTOR 9 qaiyifjgl ATTORNEY United States Patent '0 ELECTRIC APPARATUS HAVING A PROTECTIVE GAP Alert M. Opsahl, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corpora tion of Pennsylvania Application February 8, 1951, Serial No. 210,013 Claims. Cl. 317-16 My invention relates to improvements in electric appa ratus for distribution systems, and it has reference in particular to a protective gap for reclosing circuit breakers, sectionalizing switches and such devices as have series connected operating coils.

One object of this invention is to provide in a circuit interrupter of the type described, novel means for protecting the coil from lightning and voltage surges from other causes.

Another object of this invention is to provide in a device of the type described a simple and inexpensive protective air gap for protecting the operating coil thereof.

Another object of the invention is to provide an electric apparatus having an insulating bushing affording a connection to a series type operating coil, for locating a protective air gap for the coil inside the bushing above the oil level.

These and other objects of this invention will become more apparent upon consideration of the following detailed description of a preferred embodiment thereof, when taken in connection with the accompanying drawing, in which Figure l is a substantially central vertical section of a sectionalizing switch constructed in accordance with this invention and Figure 2 is an enlarged vertical sectional view, broken out in part, of the contact rod assembly used in the insulating bushing shown in Fig. 1.

In order to illustrate one embodiment of my invention I have shown it as applied to a sectionalizer of the type described in detail in copending application Serial No. 106,886 of James M. Wallace and Andrew W. Edwards, which sectionalizer is disposed to be used in conjunction with an automatic reclosing circuit breaker for opening after a predetermined number of breaker openings, so as to disconnect a faulty line section and permit the breaker to reclose and stay closed. However, it is to be understood that my invention is not intended to be limited to this type-of circuit interrupters, but may be used with reclosing breakers and other types of electrical apparatus also.

Referring to Fig. 1 it will be seen that a sectionalizer 17 is shown as being enclosed within a metal tank 27, which is provided with an insulating liner 28, and which is surmounted by a top casting 29. An incoming line 15 enters through a bushing 31 which terminates inside of the tank. The circuit then continues, through a conductor 32, to the sectionalizer coil 19. From the sectionalizer coil 19, the circuit continues through a conductor 33 back under neath the bushing 31 for the incoming lead 15, and thence to the terminal 3 which constitutes one of the stationary contacts of the sectionalizer. Ordinarily, the sectionalizer has two bushings, each with its lead passing through the bushing, and each bushing terminates at its bottom in, or supports at its bottom, one of the stationary contacts of the sectionalizer, but since Fig. 1 shows an approximate central vertical section through the sectionalizer,

the second stationary contact is not visible in Fig. 2. The movable contact 20 is shown, in Fig. 1, as a contact bar or bridge which presses up against the underside of the stationary contact 34 and the other stationary contact (not shown) in the closed position of the sectionalizer, and which is lowered by gravity, to operate the sectionalizer, upon the release of a pull rod 36, which is shown in the form of an upwardly extending insulating tube.

A counter and lockout mechanism 23 is segregated, in Fig. 1, into its component parts, consisting of the counter 37 and the operating mechanism 38.

The sectionalizer 17 can theoretically operate either in air, or in an insulating oil or other insulating fluid. It is sometimes desirable for the counter 37 to operate in oil, as it involves dashpot or fluid flow operation, as subsequently described, which is somewhat more diflicult to obtain in air, with the necessary time constants. It is sometimes desirable to have the contacts 34-20 also operating in oil. We have consequently illustrated our apparatus, by way of example, as having the counter 37 and the contacts 3420 immersed in oil 40 which is contained in the tank 27.

The particular operating mechanism 38 which is shown in the accompanying drawing constitutes the subject matter of application Serial No. 106,887 of J. M. Wallace and A. W. Ogg. In brief, it will perhaps sufiice to say that this operating mechanism comprises a bell-crank trigger 53 and an operating handle 69. The trigger 53 supports a lever 47 which is pivotally mounted by a pivot 43 on a frame 41 secured to the casting 29. A lever 43 is pivotally mounted on the lever 47, and the rod 36 is pivotally secured to one point of the lever 43, which is generally triangular. A lever 46 which is connected in toggle arrangement with a handle 66 mounted on the casting 29 by a pivot 61, is pivotally connected to the third point on the lever 43. The trigger 53 has a downwardly extending abutment-portion 56 which is adapted to be tripped when an upward movement of a trip pin 57 of the counter 37 raises said abutment point 56 of the trigger, whereupon the linkage of the operating mechanism permits the pull rod 36 and the movable-contact member 20 to drop freely in the opening operation of the mechanism.

The counter 37, which is described in detail and claimed in the copending application Serial No. 106,886 of J. M. Wallace and A. W. Edwards, is suspended from the top of the top casting 29, by means of a plurality of depending insulating supports or tubes 70, which support the base frame 71 of the counter. The counter proper 37 comprises a vertically disposed tube 72, which is preferably made of brass'or other non-magnetizable metal. The lower end of the tube is tightly closed by a plug 73, while the top of the tube 72 is open. The series current coil 19 surrounds a portion of the tube 72, intermediate its upper and lower ends. Immediately above and below the coil 19 are two perforated magnetizable plates 74 and 75, respectively, both of which are perforated so as to surround the tube 72. The plates 74 and 75 serve as the two pole pieces of an electromagnetic circuit, the excitation of which is provided by the coil 19.

Inside of the tube 72 are two normally spaced magnetizable cores or armatures 76 and 77, which are slidably movable, with a close fit of say perhaps 3 mils radial clearance, within said tube. The upper armature 76 extends partly above and partly below the level of the upper plate 74, while the lower armature 77 extends partly above and partly below the lower plate 75. Each of these armatures 76 and 77 thus extends partly within and partly without the space between the two plates 74 and 75.

At least one of the armatures, such as the upperarmature 76, and preferably both of the armatures 76 and 77, are provided with a plurality of annular magnetizable ribs 78 which are vertically spaced from each other by a spacing which is preferably approximately the same distance as the closable distance between the two armatures 76 and 77, or other disposition which will magnetically lock the respective armatures against unwanted vertical displacement or slippage. A compression spring 79 is disposed between these two armatures, so that, when the coil 19 is sufliciently energized, the two armatures are brought together, storing up energy in the interposed compression-spring 79, as will be more fully described hereafter.

Each of these armatures 76 and 77 is provided with a central bore, the lower end of which is closable by means of a ball valve 82 so that the fluid which is entrapped within the closed lower end of the tube '72 resists any rapid downward movement of either armature, be cause of the closure of these ball valves, while said valves permit the free upward movement of either armature. The entrapped fluid could be any gas or liquid having the required viscosity in comparison with the mechanical clearances which are provided. The idea is to permit the respective armatures to move freely upwardly, in a step by step motion, as will be subsequently described, while permitting said armatures to drift back downwardly again, by fluid leakage, at a very slow rate.

At the top of the upper armature 76 is a tubular tip or trip pin 57, which is capable of actuating the trigger 53 after any desired number of counts, such as 1, 2, 3 or 4, within the range of the counting mechanism 37.

In the operation of the counting mechanism 37, when the coil 19 is first energized, with a current corresponding to the setting of the counter, the two armatures 76 and 77 are drawn together, so as to close the air gap which separates the inner ends of said armatures. The upper armature 76 cannot move downwardly to bring the two armatures together, because of the presence of its fluid flow valve, and hence the lower armature 77 must move upwardly. The attractive force between the two armatures is greater than the attractive force between the lower plate 75 and the corresponding rib 78 of the lower armature 77, which was at first on the same level as said lower plate 75. When the lower armature completes its upward movement, compressing the spring 79, its next rib 78 comes into a magnetic interlock with the lower plate 75, thus holding said lower armature from drifting or settling downward, due to gravity and the slow leakage of the fluid filling of the tube 72.

When there is a fault on the distribution line, within the protective reach of the recloser associated with the sectionalizer, the recloser contact quickly opens, and quickly again recloses, but during the moment (12 cycles or more, in a 60-cycle line) when said recloser contact was open, the sectionalizer coil 19 is deenergized, and the compression spring 79 between the two armatures 76 and 77 expands, and pushes the two armatures apart again, to their normal separation distance. During this action, however, the lower armature 77 cannot move downwardly, because of its fluid flow valve, and hence the upper armature 76 must move upwardly, which it is free to do, so far as fluid action is concerned, because its valve will open during such movement. The magnetic attraction between the upper and lower plates 74 and 75 and the corresponding magnetizable ribs 78 of the upper and lower armatures 76 and 77 is now practically nonexistent, because of the deenergization of the coil 19, and hence the upper armature 76 is notched upwardly by a distance corresponding to the amount of compression of the spring 79.

If a fault continues on the distribution system, at a point beyond the sectionalizer coil 19, the reclosure of the recloser contact reenergizes the sectionalizer coil 19 and causes a second compression of the spring 79, in a manner already described. If the fault is still on the system, as has just been assumed, the recloser contact again opens, and a second upward stepping movement of the trip pin 57 is obtained. And thus the step by step movement of the counter mechanism continues.

When the last upward stepping of the upper armature 76 is obtained, depending upon the vertical positioning of the trip pin or tubular tip 57, this pin 57 comes into contact with the trigger 53 during this last upward move ment, and trips out the sectionalizer contact 20. It will be noted that this last upward movement of the trip pin 57 occurs during a time when the current in the sectionalizer coil 19 is off. In the operation of a reclosing circuit breaker the current remains ofi, that is, the recloser contact remains open, for a minimum of l2 cycles (on a 60-cycle line), before the recloser contact recloses. The opening of the sectionalizer contact 20 requires something like 2 or 3 cycles, so that it is seen that the sectionalizer contact 20 opens during the current ott period, so that the sectionalizer contact 20 does not have to interrupt any substantial current.

In order to protect the sectionalizer coil 19 from volt age surges such as caused by lightning and the like, it is desirable to use a protective gap to permit such surges to bypass the coil. Becausea gap in oil requires such a close spacing for it to be effective that it makes such a gap difiicult to calibrate and maintain, an air gap is more desirable. Instead of providing a separate gap device as has been used heretofore, I propose to build the gap integrally with the bushing 15, whereby a simple and inexpensive, as well as durable and reliable air gap structure is provided.

Referring to Figs. 1 and 2 it will be seen that the conductor 15 may comprise a rod 80 threaded at its upper end to receive a suitable terminal connection. A threaded portion 31 may be provided adjacent the lower end of the rod 81 to receive a tubular conductor 84. The tubular conductor may be provided with a shoulder 83 adjacent its lower end, by means of a bushing 85 which may be brazed or otherwise secured in the conductor together with a connector terminal 86. A central electrode rod 87 may be positioned in the conductor 84 by means of an insulating bushing 89, being located by means of a snap ring 90 and a nut 92 on rod 87. An insulating washer 93 separates the nut 92 from the end of tubular conductor 84. A contact 34 and a connector terminal 95 may be secured on the lower end of the electrode 37. An annular gap 96 will thus be provided between the upper end of the electrode 87 where it projects beyond the bushing 89 and the inner Wall of the conductor 84, which is connected in shunt circuit relation with the coil 19 by conductors 32 and 33. Any voltage surge appearing across the coil 19 will thus be bypassed around the coil across the gap.

By utilizing a protective gap in the manner hcreinbefore described, a positive and reliable air gap is provided for protecting the series coil against voltage surges such as may be caused by lightning or switching surges. The gap integral with the insulating bushing makes a compact and efficient structure requiring fewer parts and making a less expensive assembly. The gap is so located that its calibration is unaffected by the presence of oil in the tank, yet all parts of the gap are adequately insulated from ground.

Since certain changes may be made in the above described construction, and different embodiments of the invention may be made without departing from the spirit or scope thereof, it is intended that all the matter contained in the above description and shown in the accompanying drawing shall be considered as illustrative and not in a limiting sense.

I claim as my invention:

1. A circuit interrupter comprising a metal casing, a stationary contact and a cooperating movable contact in said casing, electro-responsive means in said casing eleetrically'connected in series circuit relation with said contacts and operable in response to predetermined abnormal cOnditiOns in the circuit to effect movement of said movable contact to an open circuit position to interrupt the circuit, said contacts and electro-responsive means being electrically insulated from said casing, a hotlow insulating bushing extending through a Wall of said easing into the interior thereof, a conductor extending into said bushing from outside said casing and electrically connected in series circuit relation with said electro-responsive means and said contacts, a second conductor coaxially disposed in predetermined spaced relation with the aforesaid conductor in said bushing to provide a protective gap therebetween completely enclosed by said bushing and insulated from said casing for protecting said electro-responsive means from predetermined abnormal voltage conditions, said second conductor being electrically connected to said stationary contact and to said electroresponsive means so that said gap is electrically connected in shunt relation to said electro-responsive means, said stationary contact being supported from said insulating bushing.

2. In combination, electrical apparatus having electroresponsive means operable to etfect operation thereof, a metal casing for enclosing said electrical apparatus, said apparatus and electro-responsive means being mounted within said casing and insulated therefrom, a hollow insulating bushing extending through said casing into the interior thereof and having an electrical conductor means extending from outside said casing into said bushing and insulated from the casing thereby, an additional conductor coaxially disposed in spaced relation with the aforesaid conductor means within said bushing to provide a gap therebetween completely enclosed by the bushing, said additional conductor being electrically connected to the electrical apparatus, and circuit means electrically connecting said conductor means to one terminal of the electro-responsive means and said additional conductor to the other terminal of said electro-responsive means to provide a single protective gap within the bushing with both said conductor means and additional conductor insulated from the metal casing by the bushing and said single gap disposed directly in shunt circuit relation with said electro-responsive means.

3. A circuit interrupter comprising, a metal container having an insulating fluid therein, a metal cover for said container, a pair of stationary contacts disposed in the fluid, support means for said contacts including a conductor extending through the cover, support means for said conductor comprising an insulating bushing disposed about the conductor and extending through the cover into the fluid, a movable contact normally disposed in bridging relation With said stationary contacts, trip means including an electromagnetic device electrically connected in series circuit relation with said contacts operable in response to predetermined conditions in the circuit for effecting separation of the movable contact from the stationary contacts, and an additional conductor disposed in said bushing between said first mentioned conductor and the stationary contact, said additional conductor being supported by said bushing and electrically connected to one of said stationary contacts and disposed in spaced end to end relation with said first mentioned conductor, said first mentioned conductor including a tubular extension secured thereto and extending about a portion of the additional conductor to provide a predetermined radial air gap therebetween above the fluid and remote from the cover, and rigid connectors extending radially from the first mentioned conductor and additional conductor connecting said conductors and the electromagnetic device to place the electromagnetic device in series with the contacts and the gap in shunt circuit relation with the electromagnetic device.

4. A circuit interrupter comprising, a metallic container, a metal cover for said container, separable contacts disposed in said container, electro-responsive means having a solenoid electrically connected in series with said contacts operable in response to predetermined overload conditions to effect separation of said contacts, said contacts and electro-responsive means including said solenoid being electrically insulated from said metallic container and cover, an insulating bushing extending through said cover into a central portion of the container having a conductor therein connected in circuit relation With said contacts and solenoid, electrode means carrying one of said contacts disposed in coaxial and spaced relation with said conductor in said bushing and supported by the bushing in the central portion of the container, said conductor including a hollow extension extending about a portion of said electrode means and in predetermined spaced relation therewith to provide a protective gap within said bushing to protect said solenoid of the electro-responsive means from excessive voltage surges, and rigid connectors electrically connecting said hollow extension of said conductor to one terminal of said solenoid and electrically connecting said electrode means to the other terminal of said solenoid so that said protective gap is in shunt relation to said solenoid.

5. In a protective device for a circuit interrupter having a metal container, separable contacts disposed in said container, and electro-responsive means having a solenoid connected in series circuit relationship with said contacts disposed in said container operable in response to predetermined overload conditions to effect separation of said contacts; said contacts and electro-responsive means being electrically insulated from said metal container, an insulating bushing extending into a central portion of said container provided with a conductor therein disposed to be connected in series circuit relation with said solenoid of the electro-responsive means and said contacts, said conductor having a hollow portion Within said insulating bushing in said central portion of the container with oppositely disposed openings therein, an electrode disposed within the hollow portion of said conductor connected to and supporting one of said contacts and having an end adjacent said openings, insulating means supporting said electrode in predetermined spaced relation with said conductor to provide a protective air gap therebetween, and rigid radial connectors on the electrode and hollow portion connecting the electrode in said series circuit relation with the solenoid of the electro-responsive means as to connect the gap in shunt relation therewith.

References Cited in the file of this patent UNITED STATES PATENTS 656,680 Thomson Aug. 28, 1900 1,310,054 Brown July 15, 1919 1,472,346 Kline July 17, 1923 2,142,188 Gaston Jan. 3, 1939 2,242,838 Somes May 20, 1941 2,250,165 Mitschrich July 22, 1941 2,281,073 Leonard Apr. 28, 1942 2,333,604 Wallace Nov. 2, 1943 2,414,786 Luicks et al. Jan. 21, 1947 2,464,303 Gesellschap Mar. 15, 1949 2,567,413 Van Ryan et al. Sept. 11, 1951

Images