US2401963A

US2401963A - Electric circuit breaker

Info

Publication number: US2401963A
Application number: US486066A
Authority: US
Inventors: Earl B Rietz; Dell K Tower
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1943-05-07
Filing date: 1943-05-07
Publication date: 1946-06-11
Anticipated expiration: 1963-06-11

Description

June 11, 1946. n E, B, RlETz ETAL 2,401,963

ELECTRIC CIRCUIT BREAKER Filed May '1, 194s Figa.

Fig.

Insulation oil Level-- n v a i K i i 7 I l l3`- Insulation ,Z l Z0 Insulation Inventors: ,Eavd B. Rietz Dell Tower;

Their Attorney Patented June 11, 194s UNITED STATES PATENT OFF@ iznnofrluc cmcorr Bananen.

-Earl B. Rietz,A Lansdowne, and Dell K. Tower, y Newton Square, Pa., assignors to General Electric Company, a corporation o! New York Application May 7, 1943, Serial No. 486,066

liruterrupting unit that is electrically efficient and simple and compact in construction.

Our invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features ci novelty which characterize our invention will be pointed out with particularity inthe claims annexed to and forming a -part of this specification.

Referring to the drawing, Fig. l. is an elevational view, partly in section, of an oil circuit breaker embodying the present invention, Fig. 2 is an enlarged sectional view of one ci the interrupting chambers shown in Fig. i, and Fig.- 3 is a plan view taken along the line -3-3 oi Fig. 2. The oil circuit breaker shown by Fig. l is of the high voltage type, such as that used in power transmission systems. The circuit breaker comprises essentially an oil tank I having a top frame structure 2 in which are mounted the high voltage insulating bushings 8 and 4 for the lead-in conductors and 6, respectively. The insulators and lead-in conductors extend into the oil tank l and have attached to their lower ends the contact containing interrupting chambers generally indicated as 1 and 8, respectively. The interrupting chambers and the insulators are rigidly interconnected by an insulating brace 9.

For cooperating with the ilxed contact structure hereinafter described within the interrupting chambers, a movable bridging contact member In having hollow contacts Il and i2 is vertically movable by an insulating operating rod I3 to make and break the circuit within the interrupting chambers. The bridging member is suitably operated by mechanism (not shown) within the dome 2. In normal operation the interrupt- 5 Claims. (C1. 200-150) Referring more particularly to Fig. 2 which shows an enlarged sectional view of the contact containing chamber t, the Contact containing chamber is supported at the lower end of the insulator 4 by means of a metallic adapter i4 that is in turn electrically connected to the lower end of the lead-in conductor 6. The adapter has secured thereto, as by screw-threaded engagement,

.a strong metal cylinder i5 serving as the main mechanical structure of the interrupting or blast chamber 8. The adapter also has mounted in depending relation therefrom a substantially fixed butt contact i6 that is also electrically connected at li to the adapter. The butt Contact is suitably mounted for limited wiping movement against the bias of its spring lil.

A oating contact it located intermediate the rlxed contact i6 and the bridging contact member tact iii is biased downward by a spring 23 toward following engagement with the contact l2., In

closing, the contact i2 first engages the contact portion lea of the floating Contact and pushes it upward against the bias of spring 23 until the contact portion i917 firmly engages the iixed contact it. In opening, lowering of the contact i2 rst causes separation of the contacts I6 and i913, and subsequently separation of the contacts lSa and l2, This. sequential formation of two breaks in series causes the arcing pressure generated at the break kiG-i9b to be utilized to blast oil through the interrupting break i9a-I2. This is generally known as oil-blast action. This type of oil circuit breaker ls well known in the art and further description l of the arc interrupting process is unnecessary.

As previously stated, contact containing chamber' 8 comprises essentially a metal pot or cylinksupporting the insulating throat bushing 25 that is heldin position by lan insulating clamping ring v25 bearing on the ilange I5b. The throat bushing 25 forms the passagethrough which the contact I2 moves into the oil-blast chamber and in which the arc is drawn upon separation oi the contacts lla and I2.

In accordance with our invention the outer wall of the chamber comprises a combined insulating sleeve and resistor unit, the insulating,r sleeve 21 fitting closely over the pot I and extending from near the top of the pot structure to an arcing member 28 hereinafter described, secured to the lower end of the pot, and the resistor 29 being wound about the sleeve 21 in grooves in the form of a helix. The upper terminal oi' the resistor is electrically connected at 29a to the top of the pot I! and the lower terminal is electrically connected in any suitable manner at h to the arcing member 28. In the specific arrangement shown the resistor unit above described is further insulated and shielded by an insulating sleeve 3U mounted on an outer flange of the arcing member at ll and suitably spaced from the resistor as indicated at 32. In another arrangement the resistance supporting sleeve 2'I is suitably carried by an insulating collar secured to the lower end of the throat bushing 25.

The arcing member 2B is shown also in plan view by Fig. 3 and comprises a disk-like conducting structure secured directly by fibre holding studs 32 to the pot flange- I5b. In an alternative arrangement the arcing member 28 can be directly secured to the insulating collar above referred to.

When clamped in the Fig. 2 position by the stud nuts 33a against the insulating ring 26 the arcing member is insulated from the metal pct but is electrically connected to it through the resistor 29 and through the screw thread mounting to adapter I4. At the exhaust end of.' the throat bushing the arcing member forms four electrode portions 28a spaced approximately 90 degrees apart and extending substantially to or slightly beyond the periphery of the throat opening. It will therefore be seen that the contact I2, in

moving from the chamber, has slight mechanical clearance at the electrodes 28a but usually touches some of them 4in operation because practically it cannot be perfectly centered.

The operation of the circuit breaker is as iollows: When the circuit breaker is closed the power circuit includes the lead-in conductor 6, adapter- M and the contacts Il, I8 and I2. Although the contact I2 may touch 22a, the resistor 2l does not carry an appreciable part of the normal power current in the closed circuit position of the breaker. When the breaker is opened the contacts separate in the sequence above described with the result that the interrupting arc between Ia and I2 is subjected to the oil blast. The contact l2 moves through the throat passage during interruption of the power arc at a current zero by the oil blast. Immediately after momentary interruption at a current zero the returning voltage between the contacts Il and I2 causes current to flow through the resistor either because contact I2 touches Ila or the voltage breaks down the gap at one or more of the arcing electrodes 28a (due to the short gap between the electrode and the contact I2 as compared with the main interrupting gap at the break iSd-I2). The resistor 22 is thereby inserted in series with the power circuit so that the resistance circuit now shunts the main chamber contacts.

The magnitude of the arc current is correspondingly decreased by the resistance and the dimculty of completely interrupting the circuit is greatly diminished, particularly in the caseiot circuits having high rates of increase of the recovery voltage and also in the case of capacitance switching. In the former case the rate of increase of recoveryl voltage is greatly reduced and the power factor is improved thereby simplifying the problem of interruption, and in the latter cass high switching over-voltages are prevented in the manner described in a copending application Serial No. 477,400, flied February 27, 1943 by Boehne and Peterson for Means for eliminating the switching over-voltage hazard in alternating current circuits vand assigned to the same assignee as the present invention, now Patent No. 2,391,672, issued Dec. 25, 194,5.

The ohmic value 0i' the resistance at 28 forms no part of the present invention and depends on the characteristics of the circuit to be controlled.

When the comparatively weak are current through the resistor is ilnaliy extinguished by the cooling effect oi' the oil, further downward movement of the contact I2 serves to increase the oil gap for isolating the contacts from each other so that there is no danger of fiashover or restriking of the arc.

It will therefore be seen that we have provided an eilcient, simple and compact interrupting unit that occupies practically no more space within the oil tank than conventional interrupting chambers and that is easy to inspect or repair. For example, the resistor unit can be readily removed from the breaker and replaced independently of the main chamber and the contacts therein so that complete disassembly of the cham ber construction is unnecessary. Also the complete contact assembly can be removed as a unit by unscrewing it from the adapter il. Due to the compactness of the unit, the size of the oil tank need not be increased to provide additional essential electrical clearance.

In certain cases, it is within the scope of our invention to providewiping contact engagement between the auxiliary electrode structure and the movable contact I2. In this arrangement, the resistance is inserted in the circuit through current flow. Also, it is within the scope of our invention to provide, for example, a molded cylinder of suitable resistance material in lieu of the insulating cylinder 2l and wire resistor 20.

Insofar as system operation is concerned advantages of our invention include improved system stability, reduction of insulation failures due to vswitching over-voltages and subsequent interruption of service, and increased capacitive kva. switching ability of the breaker, thereby making possible increased breaker economy as well as the release of more wattiess kva. for useful manuxacture by the greater use of capacitor banks for power factor correction.

It should be understood that our invention is not limited to specific details oi' 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 our invention. For example, the oilblast chamber may `be of the well-known sidevent type wherein the exhaust port is located in the side wall ot the chamber instead of at the bottom through which the movable contact passes. In this arrangement the operation is essentially the same except that the oil blast is directed transversely instead o! longitudinally through the arc.

What we claim as new and desire to secure by Letters Patent 0I the United States is:

i. An electric circuit breaker comprising an insulating and arc extinguishing liquid, an are lnterrupting blast chamber immersed in said liquid, contacts separable in said chamber to interrupt the circuit, a resistor associated with said chamber and electrically connected to one of said contacts. an arcing electrode also associated with said chamber at the blast opening thereof, and means for operating said contacts so that the circuit through said contacts is interrupted while another of said contacts is moving through said exhaust opening adjacent to said arcing electrode, said resistor being arranged to shunt said contacts in accordance with current ilow between said arcing electrode and said moving contact whereby said resistor is inserted in the circuit to be interrupted.

2. An electric circuit breaker comprising an insulating and arc extinguishing liquid, an arc interrupting oil blast device having an exhaust opening immersed in said liquid, contacts including a movable contact separable in said device to interrupt the' circuit, a resistorassociated with said device and electrically connected to one of saidA contacts, an arcing electrode connected to said resistor and positioned at said exhaust opening so as' to have slight mechanical clearance with said movable contact, and means for operating said movable contact so that the circuit through said contacts is interrupted while said movable contact is moving through saidexhaust opening adjacent to said arcing electrode, said resistor being arranged to shunt said contacts upon comwhcreby said resistor is inserted in the circuit to be interrupted. l

3. An electric circuit breaker comprising an insulating and arc extinguishing liquid, an arc interrupting oil blast chamber having an ex` haust opening immersed in said liquid, contacts including a contact movable through said exhaust opening separable in said chamber to interrupt the circuit, a resistor mounted on said chamber and electrically connected to one of said contacts. an arcing electrode connected to said resistorand positioned at said exhaust openpletion of circuit at the clearance vgap between said arcing electrode and said movable contact said arcing electrode and said'movable contact whereby said resistor is insertedin the circuit to be interrupted. l

4. An electric circuit breaker of the oil-blast type comprising an insulating and arc extinguishing liquid, an oil-blast arc interrupting chamber having an exhaust opening immersed in said liquid, contacts including a contact movable through said exhaust opening separable in said chamber to interrupt the circuit, a resistor generally in the form of a helix surrounding said chamber and electrically connected to one of said contacts, an arcing electrode disposed at said chamber exhaust opening connected to said resistor, and means for operating said movable contact so that the circuit .through said contacts is interrupted while said movable contact is moving through said exhaust opening adjacent to said arcing electrode, said resistor being arranged to shunt said contacts upon voltage breakdown of the clearance .gap between said arcing electrode and saidmovable contact whereby said resistor is inserted in the circuit to be interrupted. 5. An electric circuit-breaker of the oil-blast type comprising an insulating and arc extinguishing liquid, an arc interrupting device including a chamber having an exhaust opening immersed in said liquid, contacts including a contact movable through said exhaust opening separable in said chamber to interrupt the circuit, a resistor mounted on said chamber and elecl .arcing electrode comprising a conducting ringlike structure substantially vsurrounding said movable contact and having slight mechanical clearance therewith, said arcing electrodebeing connected to said resistor and located substantially in alinement with said -exhaust openingat said exhaust opening, and means for operating said contact so that the circuit through said contacts is interrupted while the moving contact is passing through said" exhaust opening adjacent tol said arcing electrode, said resistor being ar ranged to shunt said contacts upon voltage breakdown of the clearance gap-between said arcing electrode and said movable contact whereby said resistor is inserted in the circuit to be interrupted.

EARL n. RmTz. DELL K, 'rowm