US3345487A - Hydraulically operated circuit breaker - Google Patents

Hydraulically operated circuit breaker Download PDF

Info

Publication number
US3345487A
US3345487A US432983A US43298365A US3345487A US 3345487 A US3345487 A US 3345487A US 432983 A US432983 A US 432983A US 43298365 A US43298365 A US 43298365A US 3345487 A US3345487 A US 3345487A
Authority
US
United States
Prior art keywords
interrupting
housing
hydraulically operated
puffer
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US432983A
Other languages
English (en)
Inventor
Albert P Strom
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Westinghouse Electric Corp
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US432983A priority Critical patent/US3345487A/en
Priority to JP891666A priority patent/JPS4121658B1/ja
Priority to US651851A priority patent/US3500723A/en
Application granted granted Critical
Publication of US3345487A publication Critical patent/US3345487A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02—Details
    • H01H33/28—Power arrangements internal to the switch for operating the driving mechanism
    • H01H33/30—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator
    • H01H33/34—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator hydraulic

Definitions

  • Circuit breakers of the sulfur hexafiuoride have been found to be very effective interrupters and have a number of advantages over breakers of other types.
  • SP gas pufier type For high current interruption a large amount of power is required to operate the puffer.
  • the puffer and the movable contact member are tied together, making it diificult to build up sufiicient gas pressure at the start of arcing.
  • Another difficulty is that when the contacts open before pressure has built up sufficiently to have appreciable interrupting ability, gas is being discharged through the interrupting orifice and lost for use later when the contacts have reached a separation at which interruption can take place.
  • such a breaker may be unable to interrupt at the first current zero because of too low a gas pressure, and the loss of gas up to that point will cause a reduction pressure at the following current zero, thereby making interruption more difiicult at that time.
  • An object of this invention is to increase the interrupting ability of hydraulically operated circuit breakers of the puffer type.
  • a more specific object of the invention is to make the contact operation separate from the putter operation, opening the contacts at any desired point of the putter motion.
  • Another object of the invention is to prevent the flow of the interrupting gas through the orifice of the inter rupter until the movable contact starts to move.
  • a further object of the invention is to increase the speed of response of a hydraulic system, thereby rapidly initiating the gas blast and opening the contacts sufiiciently for interruption.
  • Still another object of the invention is to utilize the mechanism housing of a circuit breaker as a central storage space for the interrupting gas.
  • a still further object of the invention is to discharge the interrupting gas from two interrupting units into the central storage space, thereby reducing the size and the cost of the porcelain arc chambers for the interrupting units.
  • Another object of the invention is to locate the sump chamber for the hydraulic system within the mechanism housing and cover the chamber with a diaphragm, thereby permitting it to operate at the pressure of the interrupting gas in the breaker without exposing the hydraulic oil to the gas.
  • a further object of the invention is to utilize one puffer for supplying high pressure gas to a plurality of interrupting units in a circuit breaker.
  • a large puffer in the top of the mechanism housing for a circuit breaker is actuated by a hydraulically operated piston and supplies compressed SP gas to two interrupters 3,345,487 Patented Oct. 3, 1967 located in porcelain arc chambers on opposite sides of the central mechanism and gas storage chamber.
  • the interrupter contacts are actuated by means of a pair of small hydraulically operated pistons controlled by a pilot valve which is operated by a cam connected to an extension of the puffer hydraulic operator piston rod. This cam can be adjusted to initiate motion of the contacts at any desired position of the putter piston.
  • the accumulator and the sump for the hydraulic system are located in the mechanism housing which is at high potential.
  • the puffer hydraulic operator is controlled by a control valve located in the mechanism housing.
  • the pilot valve for this control valve is located at ground potential, as is the high pressure hydraulic pump. Opening and closing operations are initiated by solenoid mechanisms.
  • FIGURE 1 is a diagrammatic view of a hydraulically operated circuit breaker embodying principal features of the invention.
  • FIGS. 2 and 3 are diagrammatic views of modifications of the invention shown in FIG. 1.
  • the circuit breaker structure shown therein comprises a mechanism housing 11 having a pair of interrupting units 12 extending from opposite sides thereof, insulating members 13 for supporting the housing 11 which is maintained at a relatively high potential, and control apparatus 14 which may be at ground potential and enclosed in a suitable housing (not shown).
  • Each interrupting unit 12 includes an arc-extinguishing structure 15 enclosed within a porcelain weatherproof hollow casing 16 only a portion of which is shown.
  • the casing 16 extends laterally from the housing 11 and is attached to the side of the housing by means of a flanged rim 17 which may be cemented to the porcelain casing 16 and attached to the housing 11 by suitable bolts.
  • the circuit breaker may be generally of the type fully described in Patent No. 3,075,060, issued Jan. 22, 1963, to A. P. Strom and assigned to the Westinghouse Electric Corporation.
  • Each arc-extinguishing structure 15 includes a relatively stationary, generally tubular contact member 21, only a portion of which is shown, and a movable contact assembly 22 comprising a plurality of contact fingers 23 and an arcing contact member 24.
  • the contact fingers 23 and the arcing member 24 are removably attached to a sliding valve member 25 disposed inside a casing 26 supported within the mechanism housing 11.
  • the valve member 25 and the movable contact assembly 22 are actuated in a manner which will be fully described hereinafter.
  • the contact fingers 23 slidably engage the tubular contact member 21 which may be of the type fully described in a copending application Ser. No. 61,284, (Case No. 32,903) filed Oct. 7, 1960, by R. G. Colclaser and R. N. Yeckley and assigned to the Westinghouse Electric Corporation.
  • a generally cup-shaped orifice member 27 is also removably attached to the sliding valve member 25.
  • the orifice 27 has an opening 28 therein through which the contact member 21 extends, a relatively tight fit being maintained between the contact member 21 and the orifice 27.
  • the orifice 27 is preferably composed of polytetrafluoroethylene which is sold under the trade name Teflon.
  • the mechanism housing 11, the interrupting units 12 and a vertically disposed porcelain casing 29 is filled with an interrupting gas, for example sulfur hexafiuoride (SP which is maintained at a relatively low pressure, for example 60 p.s.i.
  • SP sulfur hexafiuoride
  • the puffer mechanism 31 comprises a piston 32 disposed inside a cylindrical portion 33 of a member 34 mounted within the mechanism housing 11.
  • the piston 32 is actuated by a hydraulic operator 35, the operation of which is controlled by a hydraulic control valve 36 mechanism housing 11.
  • a piston rod 40 is attached to the valve 25.
  • the operators 38 are both controlled by a single hydraulic control valve 42 which, in turn, is controlled by a pilot valve 43..
  • a hydraulic accumulator 44 supplies oil at a high pressure to the hydraulic operators and the control valve, and a sump 45 receives discharged oil from the operators and the valves.
  • An auxiliary accumulator 46 may be provided.
  • the accumulators may be of a type well known in the art, each comprising a chamber which is separated into two compartments by a movable piston 47.
  • One compartment contains a compressible gas, such as nitrogen, at a relatively high pressure for example 2000 p.s.i. and the other compartment contains oil.
  • the oil pressure in the accumulator is maintained by a compressor 48 driven by a motor 49.
  • the compressor 48 withdrawsoil from the sump 45 through a hydraulic line 51 and returns it to the accumulators through a check valve 52 and a hydraulic line 53.
  • the hydraulic operators 35 and 38, the control valves 36 and 42, and the pilot valves 37 and 43 are similar to those described in the aforesaid patent and their manner of operation is, in general, similar to that described in the patent.
  • the contact operation is separate from the puffer operation and provision is made for opening the contacts at any desired point of the puffer motion.
  • the flow of compressed gas from the puffer into the interrupting units is delayed until high pressure has been built up in the puffer, thereby preventing the loss of any of the puffer gas prior to the opening of the contact members and the drawing of an are between the contact members.
  • valve 42 comprises a piston 61 which is attached to a sleeve valve 62 by means of a spider 63.
  • the valve 62 controls the flow of high pressure oil downwardly through passages 64 in a valve casing 65.
  • oil is permitted to flow across the top 66 of the valve and out through ports 67 and through a hydraulic line 68 and thence into one end of the cylinder 41 of the operators 38 causing operators 38 to move toward the closed contact position.
  • the other end of each cylinder is connected to the accumulator 44 through a hydraulic line 69.
  • the cam 73 may be adjusted on the piston rod 59 to operate the pilot valve 43 at any desired point on the travel of the puffer piston 32, thereby determining the time at which the contact members are opened with reference to the travel of the puffer piston.
  • the compressed gas from the putter cannot escape through passageways 80 and the ports 55 into the interrupting chamber until the side valves 25 are opened along with the contact members of the arcextinguishing structures.
  • the pilot valve 37 is shown in the tripped position.
  • a solenoid 81 has been energized to actuate a latch
  • the hydraulic operators are similar to those described in the aforesaid patent.
  • the operators are of'the balanced pressure type.
  • the puffer piston 32 is retained in. its uppermost position because of a difference in cross sectional areas of piston rods 58 and 59.
  • the contact members of the interrupters are retained in the closed position.
  • the puffer piston 32 is actuated to its lowermost position and the contact members are opened by reducing the fluidpressure on one side of the pistons in the operators 35 and 38 by means of the control valves 36 and 42, respectively.
  • control valves 36 and 42 are similar to those described in the aforesaid patent.
  • high pressure fluid is permitted to flow from the high pressure line 53 through a port 86 into a line 87 and thence to thecontrol valve 36 which is operated in the same manner as the valve 42 to release the fluid pressure from the lower side of the piston 57 in the putter operator 35, thereby causing the putter piston 32 to be driven downwardly to compress gas in the cylinder 33.
  • the cam 73 operates the pilot valve 43 to open the contact members of the interrupters in the manner previously described.
  • a solenoid 91 is energized to move the spindle to the left against the force of a spring 92, thereby permitting fluid to be discharged from the control valve 36 through the pilot valve 37 into the sump line 51.
  • the control valve 36 is operated to permit high pressure fluid to enter the operator 35 through the line 88, therby driving the puffer piston 32 to its uppermost position.
  • the spindle 72' is actuated by a spring 93 to the position in which oil is released from the control valve 42, thereby causing this valve to admit high pressure oil to the operators 38 to close the contact members of the interrupters.
  • the sump chamber 45 is located within the mechanism housing 11, thereby permitting it to operate at the pressure of the SP gas within the mechanism housing. In order to prevent the oil within the sump chamber from being exposed to the gas, so that no gas is absorbed in the hydraulic oil to cause foaming,
  • the sump chamber is covered with a neoprene diasump chamber.
  • a neoprene diasump chamber only three insulating lines are required between the apparatus which is at ground potential and the apparatus which is at the high operating potential of the circuit breaker.
  • Each one of these three lines may be relatively small in diameter, thereby permitting the porcelain insulating casing 29 which encloses the three lines to be relatively small in diameter which reduces its cost.
  • the mechanism housing 11 serves as the storage space for the SP gas.
  • the porcelain arc chambers 16 are reduced in diameter, hence the cost is reduced, due to the discharge of the interrupting gas being in communication with the central gas storage chamber.
  • the interrupting ability of the interrupters is increased by making the operation of the contact members separate from the operation of the putter and so timing the opening of the contact members and the valves which control the admission of the interrupting gas into the interrupters that only high pressure gas is admitted into the interrupters to obtain maximum performance of the interrupting gas.
  • parallel resistors may be desirable. These may be of the type described in the aforesaid patent and may be mounted in additional tubular porcelain chambers paralleling the main interrupting chambers and similar to, but smaller than, the main porcelains. Interrupting contacts would also be located in these resistor tubes of similar structure and contact separation as those shown for the main interrupters, but of smaller size. The operation of these contact members would also be initiated by the cam on the pufier operator piston rod extension, operating on a separate pilot valve and control valve functioning in the manner of the valves herein described.
  • the speed of response in a hydraulic system can be considered as instantaneous. By this is meant when pressure is applied at one point of a hydraulic line or system, equal pressure is instantaneously present at all other points in the line.
  • the speed of response of a hydraulic system can be increased to practically that of solid materials by filling the hydraulic line with one or more loosely fitting cylinders of solid material having a high speed of response.
  • Glass for example, is such a material.
  • wood of some types or Mic'arta may be utilized where the hydraulic line must be of insulating material. Where insulation is notv necessary, utilized, response.
  • FIG. 2 shows how a system may be applied to a circuit breaker of the type described hereinbefore. Calculations show that approximately two milliseconds can be saved by this system over a straight hydraulic system for each ten foot length of hydraulic line.
  • a loosely fitting member 96 which may be either solid or hollow, is disposed inside a hydraulic line 87' which interconnects a pilot valve 37 and a control valve 36' of the type hereinbefore described.
  • the member 96 may be composed of a suitable solid material, such as glass or steel as previously mentioned.
  • a spring rest 97 for the member 96 may be provided at the lower end of the line 87'.
  • a hydraulic shock absorber comprising a spring 98 disposed inside a housing 99 may be provided at the upper end of the line 87.
  • Another method for high speed response in a hydraulic system is to utilize a solid rod of insulating material, such as glass, from ground potential to high potential, with hydraulic operating cylinders at each end of the rod of solid material.
  • a pressure is applied to the cylinder at ground potential, which may be considered the control cylinder.
  • This pressure is transmitted through the solid rod to the upper cylinder which is at high potential and may be considered the controlled cylinder.
  • a piston in the upper cylinder is actuated to open the valve or trip a latch.
  • a piston 101 may be disposed in a cylinder 102 and biased to its uppermost position by a spring 103.
  • the piston 101 is connected to a piston 104 by means of a rod 105 of solid material.
  • the piston 104 Y is disposed inside a cylinder 106 containing oil.
  • the cylinder 106 may be connected to a main operating valve or trip release by means of a line 107.
  • the piston 104 has an opening 108 therethrough connecting to an oil reservoir above the piston to insure pressure of oil under piston 104.
  • the opening 108 is closed by a pin valve 109 when the piston moves downwardly.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a plurality of interrupting units extending from the housing, a movable contact member in each interrupting unit, a single pufier for supplying compressed gas to all interrupting units, first hydraulically operated means for actuating the putter, second bydraulically operated means for actuating the movable contact members, and control means for causing operation of the puffer prior to operation of the movable contact members.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a pair of interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single puffer for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puller, second hydraulically operated means for actuating the movable contact members, and control means responsive to movement of the puffer for controlling the operation of the movable contact members.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a plurality of interrupting units extending from the housing, a movable contact member in each interrupting unit, puffer means disposced Within the housing for supplying compressed gas to the interrupting units, first hydraulically operated means for actuating the puffer means, second hydraulically operated means for actuating the movable contact members, and control means actuated by the puffer means for controlling the operation of the second hydraulically operated means.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a pair of interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single puffer disposed Within the housing for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the putter, second hydraulically operated means for actuating the movable contact members, control means disposed externally of the housing for controlling the operation of the first hydraulically operated means, and additional control means disposed Within the housing and actuated by the putter for controlling the operation of the second hydraulically operated means.
  • a mechanism housing containing an interrupting gas,'insulating means supporting the housing, a pair of'interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single puller disposed Within the housing for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puffer, second hydraulically operated means for actuating the movable contact members, control means disposed externally of the housing for controlling the operation of the first hydraulically operated means, additional control means disposed within the housing and actuated by the puffer for controlling the operation of the second hydraulically operated means, a sump disposed within the housing for receiving oil from the hydraulically operated means, and diaphragm means covering said sump.
  • a mechanism housing containing an interrupting gas, insulating means contact member in each interrupting unit, a single pufier for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puffer, second hydraulically operated means for actuating the movable contact member-s, control means for causing operation of the puffer prior to operation of the movable contact members, and valve means movable with the movable contact members for admitting compressed gas from the putter into the interrupting units.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a pair of interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single puffer disposed within the housing for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puller, second hydraulically operated means for actuating the movable contact members, control means actuated by the puffer for controlling the operation of the second hydraulically operated means, and valve means actuated by the second hydraulically operated means simultaneously with the movable contact members for admitting compressed gas from the puffer into the interrupting units.
  • a mechanism housing containing an interrupting gas, insulating means supporting the housing, a pair of interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single puffer disposed within the housing for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puffer, the second hydraulically operated means for actuating the movable contact members, control means actuated by the putter for controlling the operating of the second hydraulically operated means, valve means actuated by the second hydraulically operated means simultaneously with the movable contact members for admitting compressed gas from the putter into the interrupting units, and said gas being discharged from the interrupting units into said housing.
  • a mechanism containing an interrupting gas in combination, a mechanism containing an interrupting gas, insulating means supporting the housing, .a pair of-interrupting units extending from opposite sides of the housing, a movable contact member in each interrupting unit, a single pufier disposed Within the housing for supplying compressed gas to both interrupting units, first hydraulically operated means for actuating the puffer, second hydraulically operated means for actuating the movable contact members, control means disposed externally of the housing for controlling the operation of the first hydraulically operated means, a hydraulic line interconnecting said control means and said first hydraulically operated means, solid material movably disposed in said hydraulic line, and additional control means disposed within the housing and actuated by the putter for controlling the operation of the second hydraulically operated means.

Landscapes

  • Circuit Breakers (AREA)
US432983A 1965-02-16 1965-02-16 Hydraulically operated circuit breaker Expired - Lifetime US3345487A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US432983A US3345487A (en) 1965-02-16 1965-02-16 Hydraulically operated circuit breaker
JP891666A JPS4121658B1 (enrdf_load_stackoverflow) 1965-02-16 1966-02-16
US651851A US3500723A (en) 1965-02-16 1967-07-07 Hydraulic systems with increased speed of response

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US432983A US3345487A (en) 1965-02-16 1965-02-16 Hydraulically operated circuit breaker

Publications (1)

Publication Number Publication Date
US3345487A true US3345487A (en) 1967-10-03

Family

ID=23718375

Family Applications (1)

Application Number Title Priority Date Filing Date
US432983A Expired - Lifetime US3345487A (en) 1965-02-16 1965-02-16 Hydraulically operated circuit breaker

Country Status (2)

Country Link
US (1) US3345487A (enrdf_load_stackoverflow)
JP (1) JPS4121658B1 (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766343A (en) * 1970-11-23 1973-10-16 J Gratzmuller High power hydraulic control systems for an electric switch
US4461937A (en) * 1981-09-18 1984-07-24 Mcgraw-Edison Company Fail-safe hydraulically operated circuit breaker accumulator arrangement
US4514783A (en) * 1982-02-15 1985-04-30 Siemens Aktiengesellschaft Encapsulated, compressed-gas-insulated, high-voltage switching installation

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2051659A (en) * 1934-09-06 1936-08-18 Gen Electric Electric circuit breaker
US2055312A (en) * 1933-08-19 1936-09-22 Ruppel Sigwart Switch
US2056033A (en) * 1934-09-15 1936-09-29 Gen Electric Electric circuit interrupter
US2979591A (en) * 1958-09-19 1961-04-11 Westinghouse Electric Corp Circuit interrupters
US2997564A (en) * 1958-09-19 1961-08-22 Westinghouse Electric Corp Circuit interrupter
US3075060A (en) * 1957-10-30 1963-01-22 Westinghouse Electric Corp Circuit interrupters

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2055312A (en) * 1933-08-19 1936-09-22 Ruppel Sigwart Switch
US2051659A (en) * 1934-09-06 1936-08-18 Gen Electric Electric circuit breaker
US2056033A (en) * 1934-09-15 1936-09-29 Gen Electric Electric circuit interrupter
US3075060A (en) * 1957-10-30 1963-01-22 Westinghouse Electric Corp Circuit interrupters
US2979591A (en) * 1958-09-19 1961-04-11 Westinghouse Electric Corp Circuit interrupters
US2997564A (en) * 1958-09-19 1961-08-22 Westinghouse Electric Corp Circuit interrupter

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766343A (en) * 1970-11-23 1973-10-16 J Gratzmuller High power hydraulic control systems for an electric switch
US4461937A (en) * 1981-09-18 1984-07-24 Mcgraw-Edison Company Fail-safe hydraulically operated circuit breaker accumulator arrangement
US4514783A (en) * 1982-02-15 1985-04-30 Siemens Aktiengesellschaft Encapsulated, compressed-gas-insulated, high-voltage switching installation

Also Published As

Publication number Publication date
JPS4121658B1 (enrdf_load_stackoverflow) 1966-12-17

Similar Documents

Publication Publication Date Title
US2459600A (en) Compressed gas circuit interrupter
US4163131A (en) Dual-compression gas-blast puffer-type interrupting device
US3164706A (en) Mechanical operating means for fluidblast circuit interrupter
US3345487A (en) Hydraulically operated circuit breaker
US3167630A (en) Multi-break gas blast circuit breaker and operating means therefor
US2913559A (en) Fluid-blast circuit interrupter
US2909633A (en) High tension oil switch
US2572406A (en) High-voltage oil circuit breaker
US3185802A (en) Gas blast circuit breakers having at least one tubular contact
US3256414A (en) Operating mechanism for electrical circuit breaker of the gas blast type
US2924690A (en) Circuit interrupters
US3008017A (en) Circuit breaker
US3500723A (en) Hydraulic systems with increased speed of response
US3257533A (en) Fluid-blast circuit interrupters with two selectively-operated fluid-blast sources
US3379849A (en) Dual-pressure gas-blast circuit breaker with piston means and interrupting unit in closed tank
US4342891A (en) Circuit breaker with means for producing a flow of arc-extinguishing gas
US4264794A (en) Circuit interrupter including arc extinguishing fluid pressurization means and pressure accumulating means
US4034175A (en) Protracted-blast electric circuit-breaker for alternating currents
US2025549A (en) Operating mechanism for electric circuit breakers
US2919329A (en) Air blast circuit breakers
US4253002A (en) Self-extinguishing type circuit interrupter
US3334207A (en) Gas blast circuit-breaker with stationary spaced tubular contacts and piston actuated contact bridge including blast valve actuated thereby
US2261711A (en) Circuit breaker
US3333077A (en) Compressed-gas circuit breaker having contacting interrupting and isolating contactswith sequential operation
US2753424A (en) Interrupting device employing a controller for regulating contact closing speeds