US2306240A

US2306240A - Gas blast circuit breaker

Info

Publication number: US2306240A
Application number: US398128A
Authority: US
Inventors: Bryce W Wyman
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1941-06-14
Filing date: 1941-06-14
Publication date: 1942-12-22
Anticipated expiration: 1959-12-22
Also published as: USRE22298E; GB557728A

Description

Dec. 22, 1942, a. w. WYMAN GAS BLAST CIRCUIT BREAKER BLAST EXI'IlUST GAS PRESSURE Filed June 14, 1941 Inventor": Bryce W. Wyman,

His Attorney.

Patented Dec. 22, 1942 GAB BLAST CIRCUIT BREAKER Bryce W. Wyman, Yeadon, Pa., assignor to General Electric Company, a corporation of New York Application June 14, 1941. Serial No. 893.128

scum.

My invention relates to gas blast circuit oreakers wherein the arc to be interrupted is confined in an insulating structure and traversed by a blast at gas fiowing at high velocity under pressure. and has for its principal obiect the provision of an improved method of operation of and structural arrangement for. a circuit breaker of the aforesaid type so that it is particularly adapted for interrupting heavy currents throughout a wide range oi line ,voltage.

Theinterruptlon oi heavy overload and short circuit currents at moderate voltages, such as kv., has been efiiciently accomplished by a cross-blast type air circuit breaker wherein the arcisdrivenbyatransverseblastofgasinto an arc chute having insulating barriers or partitions extending edgewise to and transversely of the arcstream. The hot blast gasesfiowing from the region of arcing are directed to exhaust through the chute passages defined by the aforesaid partitions. Such a circuit breaker is housing I defining arc extinguishing structure in which are mounted for relative movement the disclosed and claimed in application Serial No.

803,126 filed November 6', 1939, by D. 0. Prince et al. for "Circuit breaking apparatus and method of operating the same" now Patent No. 2,284,842 issued June 2, 1942 and assigned to the same assignee as the present invention. When this type circuit breaker is used for interruptin'g power currents at appreciably higher voltages. such as 50 kv., insulation diiiiculties appear and, instead of clearing the circuit, the breaker may fail d to fiashover. s

In accordance with my invention, the desirable current interrupting characteristics oi the aforesaid cross-blast type breaker are retained and the voltage range of the breaker is appreciably increased by incorporating in the circuit breaker structure auxiliary meansior subjecting the arc to a high velocity axial blast prior to completion of the breaker opening operation.

My invention will be more fully set forth in the following description referring to the accompanying drawing. and the features of novcity 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. l is an elevational view in section of a gas blast circuit breaker embodying my invention in an initial stage of the opening operation, and Fig. 2 is a similar view illustrating the final stage oi a high voltage circult interrupting operation.

The circuit breaker illustrated by way of example in Figs. 1 and 2 comprises an insulating breaker contacts 2 and 8. The contact I. which may be of any suitable type, such as the resilient finger type, is shown as fixed in the housing and is connected to one line terminal oi the breaker indicated at 2'. The contact, I is termed as a blade member and is reciprocally movable in the insulating housing with respect to the fixed contact I, and is electrically connected as indicated to the other line terminal of the breaker at 8'. v

The

contacts

2 and 3 are separable within a narrow slot-like passage 4 in'the housing and this passage is arranged to be connected at one side to a source of gas pressure indicated at I. and at the pposite side (tor the first part of the contact-opening movement) with 'an arc chute 8.

atmosphere at I. The hot blast gases fiowing fromtheregionoiarcingatlarecooiedby means of spaced metallic plates disposed edgewisetothegasflowasindicatedatl. The insulating barrier I is preferably composed of a vaporizable insulating material. such as hard fibre. that does-not lose its dielectric strength in the presence of the are. An arc chute of this character is disclosed and claimed in the Prince et al. application above-identified;

When the breaker is to be opened. the movable contact I is actuated by suitable means (not shown) toward the left as.viewed in Fig. i so as to separate item contact 2 and form an arc gap opposite the entrance of the chute I. At practically the same instant, the interrupting gas is admitted under pressure by way of the conduit I to the passage 4 so that the resulting blast of gas necessarily traverses the are between the contacts I and 3 and drives it sideward against the insulating barrier I on its way to exhaust from the chute passage I. At this stage of the opening operation, the gas blast is eilective to interrupt very heavy currents at the first current zero.

In the case of high voltage circuits and circuits having a high rate of rise of recovery voltage. this interruption at the first current nero may not be permanent and the dielectric strength of the gap so formed between the contacts may be insuilicient to prevent voltage breakdown and reestablishment of arcing. This difilculty in clearing the circuit is overcome in accordance with my invention by connecting in shunt with The chute t is provided with at least one insulating barrier or partition I dividing the chuteintoblastpassagesthatareventedto the contacts during the initial opening operation, and in series therewith for the final interrupting operation an auxiliary gas blast circuit breaker of the axial blast type, preferably in series with a resistance.

To this end, an auxiliary gas blast switch of the axial blast type generally indicated at i is disposed adjacent to the path of movement of the blade contact 3 so that the auxiliary switch Ill is in electrical contact with the blade 3 during the initial part of the opening movement to shunt the original arc gap and is placed in series with the blade contact and breaker terminals immediately upon interruption of the are at thefirst current zero in the chute 6. In a simplified arrangement, the auxiliary breaker l0 comprises a movable rod contact I i that is resiliently biased, such as by a spring l2, into sliding electrical contact at H with the blade I. The rod contact H is also electrically connected through a flexible conductor I3 to a terminal indicated at H, which is in turn electrically connected through a resistance ii to the breaker line terminal 2' as indicated at IS. The rod contact II is guided for reciprocal movement in a cylinder ll formed in the main insulating housing and includes a piston l8 which functions both as a guide for the rod contact and as a valve for uncovering the blast vent port It leading from the cylinder H. The rod contact Ii is operable within a restricted nozzle-like passage 20 communicating with the cylinder I! located a short distance beneath the point of contact engagement with the blade 3.

From the above description, it will be seen that immediately upon interruption of the main power are at a current zero in the chute 6, the auxiliary breaker l0 and the resistor'i5 are connected in series with the breaker terminals 2' and 3".

' Accordingly, the current as reestablished after the current zero through this connection will be of decreased magnitude, and in addition the power factor will be improved. Therefore, when the blade contact 3 in continuing its opening movement uncovers the aforesaid nozzle passage and moves out of engagement with the rod contact ll of the auxiliary breaker, the resulting arc, which is immediately drawn into the restricted nozzle 20 due to the action of blast pressure from 5 on the piston II, is more readily extinguished by the high velocity constricted axial blast within the insulating nozzle as clearly indicated by Fig. 2. When theauxiliary breaker contact reaches the position shown by Fig. 2, the blast passage is is also uncovered so that the gas blast can sweep unhindered through and longitudinally of the arc path. This blast flows through as well as longitudinally (or axially) of the arc stream and the arrangement avoids many of the insulation difliculties of other types of gas blast breakers. The axial blast arrangement above described has been found to be particularly adapted for interrupting high voltage circuits, although it is not so well adapted as the cross blast type above described for interrupting heavy currents. Therefore by first interrupting the heavy current are momentarily at a current zero, at which time a. resistance is automatically inserted in the circuit, and then by interrupting the reduced current in the manner above described, it will be seen that I provide means for interrupting high voltage power circuits not heretofore provided in the known types of gas blast breakers.

It will also be seen that the gas pressure within the nozzle passage is caused to build up until the contact piston-valve it opens the blast exhaust vent. This increased gas pressure in the region of arcing is an additional asset during the interruption operation since the dielectric strength of the gas is thereby increased.

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:

l. A gas blast circuit breaker for high voltage power circuits comprising contacts including a movable contact separable to form an arc gap, an arc chute having an entrance opposite the initially formed part of said gap, means for directing an interrupting blast of gas through said initially formed part of the arc gap to drive the arc into said chute for extinguishing it at 9. current zero, a resistance arranged to be connected in shunt with said part of said gap whereby a reestablished power current is reduced, and. a separately operable auxiliary gas blast circuit breaker connected in series with said resistance, said auxiliary breaker having a blast operated movable contact coacting with the aforesaid movable contact to form an arc gap and having a nozzle-like arc interrupting passage for said last-formed arc gap, and means for directing a second gas blast into said nozzle-like passage axially of the are for finally interrupting the reduced current are therein.

2. A gas blast circuit breaker for high voltage power circuits comprising relatively fixed and movable contacts separable to form an arc gap, an arc chute having an entrance opposite the initially formed part of said gap, means for directing an interrupting blast of gas through and across said initially formed part of the arc gap to drive the are into said chute for extinguishing it at a current zero, a resistance arranged to be connected in shunt with said part of said gap whereby a reestablished power current is reduced, and a separately operable auxiliary gas blast circuit breaker included in said shunt connection having a separate movable contact operable in response to gas pressure to form a second arc gap, said auxiliary breaker having a nozzle-like arc interrupting passage inwhich said second arc gap is formed, and means for directing a second gas blast into said nozzle-like passage axially of the are for finally interrupting the reduced current arc therein, said second gas blast also being effective to build up pressure in said passage to cause opening movement of said movable auxiliary breaker contacts.

3. A gas blast circuit breaker for high voltage power circuits comprising relatively movable contact structure separable to form an arc gap, an arc chute having insulating partitions forming arc barriers and having an entrance opposite an initially formed part of said gap, means for directing an interrupting blast of gas transversely through said initially formed part of the arc gap so as to drive the are into said chute against said barriers for extinguishing the are at a current zero, a resistance arranged to be connected in shunt with said part of said gap whereby a reestablished power current is reduced, and a separately operable auxiliary gas blast circuit breaker included in the resistance shunt connection and having a movable contact arranged to make electrical contact with the aforesaid relatively movable contact structure so as to form a second arc gap only after predetermined separation 01' said contact structure, said auxiliary breaker having a nozzle-like arc interrupting passage through which said auxiliary contact is movable and in which said second arc gap is formed, and means for directing a second as blast into and through said nozzle-like passage 5 the reduced current are.

BRYCE W. WYMAN.