US2075748A - Electric circuit breaker - Google Patents

Description

March 30, 1937 w PAUL 2,075,748

ELECTRIC CIRCUIT BREAKER Filed Aug. 1, 1935 Inventor: William E. Paul,

Patented Mar. 30, 1937 UNITED STATES ELECTRIC CIRCUIT BREAKER William E. Paul, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 1, 1935, Serial No. 34,178

8 Claims.

My invention relates to electric circuit breakers, more particularly to electric circuit breakers of the oil-blast type for use in a transmission line which is controlled by time delay relays, such as relays of the well known inverse time limit type.

It is customary to control the circuit breakers in a high voltage power transmission line by means of time delay relays which function to delay tripping of the breaker a few cycles in re- 10 sponse to comparatively light overloads, but which act quickly to trip the breaker on heavy overloads or short circuits. Circuit breakers of the well known oil-blast type have heretofore been used in high voltage transmission lines, the

operation of such breakers generally depending on a tripping operation initiated by the current responsive relay. When the breaker is tripped, separation of the contact structure causes an initial ,or pressure-generating arc and a second or.

main arc in series therewith which is extinguished by a blast of liquid directed by the pressure-generating arc. Accordingly, it will be noted that in systems as above described formation of the pressure-generating arc is dependent on the conventional breaker tripping operation.

In accordance with my invention; the pressuregenerating arc is formed independently of the relay operation or tripping of the breaker and in case of appreciable time delay in the tripping operation is formed prior to the actual tripping of the breaker so that adequate pressure is immediatelyavailable for interrupting the main arc.

My invention will be more fully setforth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a diagram- 0' maticillustratio'n of a single phase of a high voltage transmission line in which my invention is incorporated and Fig. 2 is an elevational view,

partly in section, of, a circuit breaker of the oilblast type embodying my invention.

Referring more particularly to Fig. 1, a single phase power circuit indicated at I is controlled by a circuit breaker 2 operatively related-to a tripping latch 3 and being illustrated by way of example.

The breaker, which is normally biased towards time delay relay 4, a relay of the inverse time limit type, well known in the art,

to close the circuit of the strip coil 8 through the contacts at 9. Subsequent release of the latch at 3 permits the breaker to open under the influence of suitable bias. An auxiliary switch is indicated at II) for opening the trip coil circuit after the breaker is opened, thereby permitting resetting of the latch at 3.

The circuit breaker 2, which is preferably of the well known oil-blast type, comprises a movable bridging member Il, each end of which coacts with a relatively movable intermediate contact I2 and pressure-generating contact l3. In the closed circuit position illustrated, the contacts of each pole are in abutting engagement, the circuit being completed through the bridging member I I. In a well known form, the contact structure is arranged so that opening movement of the bridging member I I first causes separation of the contacts I2 and I3 to form the pressure-generating arc and subsequently causes separation of the contacts I I and I2 .to form the main arc which is subjected to the oil blast.

For the purpose of initiating formation of the pressure-generating arc independently of the tripping operation, each contact I3, which is composed of magnetic material, is electrically connected and operatively related to a coil I4 which when sufiiciently energized draws the contact I3 away from contact I2 to form the pressure-generating arc. Accordingly, notwithstanding a delayed action of the relay 4 in tripping the breaker the electro-magnetic means at I4 would cause, in response to predetermined current, movement of the contacts l3 to form the pressure-generating arc.

In circuit breakers of the oil-blast type this feature is particularly desirable since adequate pressures are generated at heavy currents but at lower currents a stronger oil blast is often-desired for quick and positive interruption of the arc. By building up pressure before the inyerse timelimit relays operate at low currents to trip the breaker, a strong, positive oil blast is assured.

Referring more particularly to Fig. 2 which illustrate's the structural details of an oil-blast circuit breaker adapted for the system above described, the circuit at I is completed by the bridging member I I and by relatively movable contact structure within an explosion pot I5. The explosion pot, which is composed of a suitable mechanically strong insulating material, issupported by an adapter l6 which is in turn mounted at the lower end of the lead-in conductor insulating bushing-I1. The structure above described is immersed in a suitable arc extinguishing liquid such as oil, the level of which is indicated at it.

The breaker which is illustrated in the closed circuit position comprises an electromagnetic device l9 mounted at the upper part of the explosion chamber for controlling the pressuregenerating contact la. The device l9 comprises the coil M, which is electrically connected at one terminal to the lead-in conductor at 2d and at the other terminal to the contact l3, and a magnetic core 2!! within which the contact id is drawn against the bias of spring 22 upon predetermined fiow of current through the coil M.

The intermediate contact i2 is suitably supported in the top of the explosion chamber by an insu ating plate 23 and supports 24 and is biased by spring 25 into engagement with the tubular contact 26 carried by the bridging member l t.

For the purpose of facilitating acceleration of the oil blast, the intermediate contact it is provided with a passage 2i communicating directly with the interiors of the explosion pot it and the tubular contact 2 respectively. This feature per se is disclosed and claimed in my copending application (S. N. 34,179) filed concurrently herewith and assigned to the same assignee as the present invention.

The operation of the circuit breaker illustrated at Fig. 2 is believed to be apparent from the foregoing description. In response to predetermined current, which. may be insufficient to cause instantaneous operation of the relay, the contact i3 is drawn by the coil E l away from the contact 32, thereby forming within the explosion pot an initial pressure generating are. Subsequent tripping of the breaker causes the tubular contact 26 to move downwards followed for a short distance the intermediate contact under the bias of spring 25. At the throat lid of the explosion pot separation of the contacts l2 and 26 takes place to term the main arc which is immediately subjected to an oil blast from the pot under the influence of the pressure generated therein.

The instant application of the oil blast is not only effective to shorten the duration of arcing and therefore the arc length, but also the predetermined building up of pressure assures positive and consistent interruption of the circuit at light currents. In the case of heavy currents, the pressure is not unduly increased by the in stant formation of the pressure-generating arc since in such a case the relay also acts practically instantaneously to trip the breaker.

It will be noted that the passage directly connecting the interiors respectively of the e plosion pot and movable tubular contact permits the oil blast to be under Way in response to the pressure-generating are at the time the breaker is tripped, thereby further speeding up the application of the oil blast. passage likewise relieves excessive pressure within the explosion pot.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric circuit breaker of the oil-blast type comprising an arc-extinguishing liquid, circuit interrupting structure immersed in said liq- The aforesaid acvaves uid including means forming a pressure generating arc, means forming a main arc, means utilizing the pressure of said first are for directing liquid through said main arc, and means responsive to predetermined current through said breaker for controlling formation of said pressure generating arc prior to the main circuit opening movement of said breaker.

2. An electric circuit breaker of the oil-blast type comprising an arc-extinguishing liquid, separable contact structure immersed in said liquid arranged to form a pressure generating arc and a main arc including a movable contact member for causing formation of saidmain arc, means utilizing the pressure of said first are for directing liquid through said main arc, and means responsive to current through said breaker for causing formation of said pressure generating are independently of said movable contact member.

3. An electric circuit breaker of the oil-blast type comprising an arc-extinguishing liquid, rel-- atively movable contact structure immersed in said liquid arranged upon circuit opening movement of said breaker to form two breaks in series, and electromagnetic means connected in the circuit to be interrupted coacting with said contact structure for causing, in response to predetermined current, formation of one of said breaks independently of said other break= l. An electric circuit breaker of the oil-blast type comprising an arc-extinguishing liquid, circuit interrupting structure immersed in said liquid including a relatively fixed contact, an intermediate contact and a movable contact arranged to form a preliminary pressure generating arc and a main are upon opening movement of said movable contact, and electromagnetic means coacting with said fixed contact for causing, in response to predetermined current, formation of said pressure generating arc prior to and independently of opening movement of said movable contact.

5. An electric circuit breaker oi the oil-blast type comprising means forming a pressure generating arc, means forming a main arc, means for directing an arc extinguishing liquid under pressure into said main arc, and means responsive to a predetermined current through said breaker for causing'tormation of said pressure generating arc prior to and independently of the contact movement for forming said main are so that preliminary acceleration of liquid in the path of said blast is effected prior to formation of said main arc.

6. An electric circuit breaker of the oil-blast type comprising an explosion pot, a relatively fixed contact, an intermediate contact and a tubular contact coacting in said pot and arranged so as to cause a pressure generating arc and a main arc, and electromagnetic means connected in the circuit to be interrupted coacting with said fixed contact for causing in response to predetermined current separation of said fixed and intermediate contacts to cause formation of said pressure generating arc independently of said tubular contact, said intermediate contact hav ing a passage for transmitting pressure from said pot to the interior of said tubular contact prior to separation of said intermediate and tubular contacts so that preliminary acceleration of liquid in said tubular contact is effected in response to pressure in said pot prior to formation of said main arc.

7. A circuit interrupting system comprising an electric circuit breaker of the oil-blast type in cluding an arc-extinguishing liquid, circuit interrupting structure immersed in said liquid ar- 5 ranged to form a main are upon tripping of said breaker and a pressure generating are for causing interruption of said main arc, and a time delay relay responsive to circuit conditions for causing tripping of said breaker, said breaker in- 10 eluding means responsive to said circuit conditions for forming said pressure-generating arc prior to tripping of said breaker.

8. A circuit interrupting system comprising in combination a relay of the inverse time limit type and an electric circuit breaker oi the oil blast type, said relay arranged to trip said circuit breaker in. response to and in accordance with predetermined circuit conditions, said circuit breaker comprising relatively movable contact structure immersed in an arc-extinguishing liquid arranged to form two arcs in series, the pressure generated in said liquid by one of said arcs being utilized to cause interruption of the other of said arcs, and electromagnetic means responsive to the aforesaid circuit conditions for forming the pressure-generating arc prior to tripping of the circuit breaker by said relay.

WILLIAM E. PAUL.

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