US3364325A - Gas-operated gas-blast circulating-type circuit breaker with simplified pneumatic control - Google Patents

Description

Jan. 16, 1968 J. M. TELFORD 3,364,325

GAS-OPERATED GAS-BLAST CIRCULATING-TYPE CIRCUIT BREAKER WITH SIMPLIFIED PNEUMATIC CONTROL 2 Sheets-Sheet l Filed'Dec. 7, 1964 4 INSULATION INSULATION 3 CLOSE msuumow P' Jan. 16 1968 TELFORD 3,364,325

GAS-OPERATED GAS-BLAST CIRCULATING-TYPE CIRCUIT BREAKER WITH SIMPLIFIED PNEUMATIC CONTROL Filed Dec. 7, 1964 2 Sheets-Sheet 2 HIGH PRESSURE GAS PRESSURE SWITCH PUMP LOW PRESSURE GAS INVENTOR James M.Te|ford M/QM ATTORNEY United States Patent O GAS-OPERATED GAS-BLAST CIRCULATING-TYPE CIRCUIT BREAKER WITH SIMPLIFIED PNEU- MATIC CONTROL James M. Telford, Pittsburgh, Pa., assiguor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 7, 1964, Ser. No. 416,262 4 Claims. (Cl. 200-148) ABSTRACT OF THE DISCLOSURE A compressed-gas circulating-type circuit interrupter of the pressurized tank type has a pair of arcing contacts and a pair of serially-related disconnecting contacts disposed Within a metallic dead tank having a pair of terminal bushings extending therein. One terminal bushing supports a stationary disconnecting contact structure, and the other terminal bushing is electrically connected through an interrupting assembly to the movable isolating contact. A highly efiicient gas, such as sulfur hexafluoride (SP is used; and an exhausting blast tube extends from the interrupting assembly into a low-pressure externally-disposed tank. A simplified pneumatic control scheme is used involving a minimum number of valves for efficient sequential operation of the arcing and disconnecting contacts. A three-way air-pilot-operated normallyclosed first valve has a tank connection to the closing side of the piston for the disconnecting contact under deenergized conditions. A two-Way normally-closed second valve disposed externally of the pressurized tank controls the pilot section of the first valve through a check-valve-controlled pneumatic line. A three-way normally-open trip valve controls the exhausting or pressurizing of the cylinders for the arcing contacts; and an auxiliary switch has a direct pneumatic connection to the pilot section of the first valve.

This invention relates, generally, to circuit breakers and, more particularly, to gas-blast circuit breakers of the dual-pressure type.

Prior gas-blast circuit breakers have required either costly mechanisms for mechanically operating the breakers or complicated valves for controlling fluid-pressure actuated operating means. Furthermore, in breakers utilizing compressed air as the arc-extinguishing medium the air is exhausted to atmosphere after passing through the circuit interrupters in a circuit breaker. This is not economical when an expensive interrupting gas is utilized as the arc-extinguishing medium,

An object of this invention is to provide a circuit breaker in which an interrupting gas stored in a h gh pressure tank is utilized as an operating medium, thereby eliminating a costly mechanism, mechanical links and shaft seals from the breaker structure.

Another object of the invention is to provide a gasblast circuit breaker of the dual-pressure type in which the arced interrupting gas is blasted into a low pressure chamber and then filtered before being returned to the high pressure tank, thereby preventing the main parts of the interrupter and the bushings inside the tank from being exposed to the by-products of the arced interrupting gas.

3,364,325" Patented Jan. 16, 1968 A further object of the invention is to provide for utilizing standard commercially available valves for controlling the operation of the contact members of the interrupters and the isolating switch of a gas-operated gasblast circuit breaker.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a circuit breaker comprises a relatively high pressure tank and a relatively low pressure chamber which are connected in a closed system. An interrupting unit and an isolating switch mounted inside the tank on the lower ends of terminal bushings establish a series circuit through terminal conductors inside the bushings. The contact members of the interrupter and the isolator are operated by the high pressure gas in the tank and controlled by standard, commercially available valves. When the interrupter is opened, the high pressure gas is blasted through the arc, into an orifice and out through a blast tube into the low pressure chamber. After the interrupter has reached its open position, the isolator is opened and the interrupter is then reclosed. When the in terrupter opens and high pressure gas is blasted into the low pressure chamber, the change in differential pressure starts a pump and the arced gas is returned to the high pressure tank through a filter.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which FIGURES 1A and 1B constitute a diagrammatic view of a circuit breaker and control apparatus embodying principal features of the invention, the contact members of the breaker being in the closed position.

Referring to the drawing, the circuit breaker 1 shown therein may be of a three-phase type having three pole units, only one of which is shown in the present drawing. Preferably, each pole unit comprises a generally cylindrical high pressure tank 2, which is supported by feet 3, and a low pressure reservoir 4 attached directly to the tank 2. The tank 2 is grounded for safety reasons.

An interrupting gas, for example, sulfur hexafiuoride, SP gas, is retained in the tank 2 under four or more atmospheres pressure. The gas in the low pressure reservoir 4 is held at one atmosphere pressure. Other interrupting gases, such as selenium hexafluoride, SeF may be utilized if desired.

Terminal bushings 5 are mounted on top of the tank 2. Each terminal bushing contains a conductor (not shown) which carries current into the pressurized tank 2 to be interrupted by an arc-extinguishing assemblage 6. The assemblage 6 is mounted on a metal base 7 attached to a conducting supporting plate 8 by insulating mem bers 9. The plate 8 is attached to the lower end of one terminal bushing 5. A stationary contact member 10 is attached to the lower end of the other terminal bushing 5. The arc-extinguishing assemblage 6 may be of the type described in a copending application Serial No. 59,882, filed October 3, 1960, now US. Patent 3,214,540, issued October 26, 1965, and assigned to the Westinghouse Electric Corporation.

As shown, each arc-extinguishing assembly 6 includes a separable pair of main contacts 11, a pair of main interrupting contacts 12, and a pair of resistance or impedance interrupting contacts 13. The main interrupting contacts 12 and the resistance interrupting contacts 13 exhaust into an insulating blast tube 14 which is connected directly to the low pressure chamber 4. A resistance or impedance 15 is connected in series with the resistance contacts 13 and serves to facilitate the interruption of the current through the main interrupting contacts 12. As well known in the art, the insertion of the impedance 15 into the circuit during a portion of the interrupting operation reduces the magnitude of the current to be interrupted.

The interruption of the resistance current by the resistance interrupter 13 completely interrupts the passage of current through the arc-extinguishing assembly 6. After the interruption of the current, it is desirable to disengage a movable isolating contact member 16 from the stationary contact member 10. By providing an isolating gap 17 between the isolating contacts, which maintains the circuit open, reclosure of the main contacts 11, the main interrupting contacts 12 and the resistance contacts 13 may then be efifected. Since the interior region 18 of the tank 2 contains gas at a relatively high pressure, it is obvious that the disconnecting gap is in a high dielectric strength atmosphere and, consequently, only a relatively small disconnecting gap distance need be provided. Therefore, the circuit breaker may be reclosed in a relatively short time.

During an interrupting operation the main contacts 11 are separated first, then the main interrupting contacts 12 are separated, and then the resistance contacts 13 are separated. After the separation of the resistance contacts the isolating contact 16 is separated from the stationary contact 10, after which the contacts 11, 12 and 13 are reclosed. The circuit is maintained open by the separated disconnecting or isolating contact 16. Thus, the circuit breaker may be reclosed by merely efi'ecting re-engagement of the isolating contact 16 with the contact 10.

The structure and manner of operation of the arcextinguishing assembly 6 is fully described in the aforesaid copending application. Accordingly, only a general description is given herein. Referring to the drawing, it will be seen that the arc-extinguishing gas for interrupting current flow between a relatively stationary orifice contact 19 and a movable main arcing contact 20 of the main interrupting contacts 12 is exhausted operatively through a cup-shaped contact support 21 and into the interior 22 of the low pressure chamber 4 through the blast tube 14. To facilitate centering of the main current are drawn through the orifice contact 19, and the receiving of a radial inward blast of gas, an arc centering horn 23 is provided. The are horn 23 is perforated and is positioned by a supporting arm 24 which is fastened by bolts 25 to a shoulder portion of the contact support 21. An opening 26 in the base 7 registers with the opening through the contact support 21 and, as previously mentioned, the blast tube 14, which is attached to the base 7 around the opening 26, communicates with the interior of the low pressure reservoir 4.

Similarly, a relatively stationary orifice contact 27 and a relatively movable resistance contact 28 are separated to draw a resistance current arc, which is subjected to a gas blast from the region 18 interiorly of the tank 2, through the orifice opening 27 and out through an opening 29 and the blast tube 14 to the region 22 within the low pressure chamber 4.

As shown in the drawing, the main current contacts 11 include a plurality of inwardly extending contact fingers 31 which engage a movable main contact member 32. The contact fingers 31 are attached to the metal base 7. The movable contact member 32 is biased downwardly by compression springs 33. The movable contact member 32 is attached by means of a piston rod 34 and a spacing sleeve 35 to a piston 36 operated vertically within an operating cylinder 37. As will be described more fully hereinafter, exhausting of the gas pressure above the piston 36 will effect upward opening movement of the piston 36 and the movable contact member 32. This will force the current passing through the main contacts 11 to flow by means of the main interrupting contacts 12 and the resistance interrupting contacts 13, although the latter will carry a relatively small proportion of the current be cause of the presence of the series resistance The main movable arcing contact member 20 is rnoved upwardly by a piston 38 movable within an operating cyl= inder 39 and biased downwardly in a closing direction by a compression spring 49. The upper end of anupwardly extending portion 41 of the contact member 20 which is secured to the piston 38 has a reduced spindle valve ertion 42 and an upper enlarged valve spool portion 43. As a result, the valve portions 42 and 43 form a sleeve valve which prevents or permits communication between a passageway 44 and a passageway 45 leading to the region above a piston 46 of the impedance interrupting unit 13. The passageway 45 is connected to a passageway 47 in a cylinder head 48 of the interrupter 13 by means of an insulated tube 49.

The movable contact member 23 of the resistance interrupter 13 is carried by the piston 46 which operates in a cylinder 51. The piston 46 is biased downwardly by a compression spring 52 disposed between a piston head 53 and the cylinder head or body 48. When gas is exhausted from above the piston 46 the pressure of the gas Within the tank 2 on the piston head 53 forces the piston 46 up wardly against the compression of the spring 52.

The isolating or disconnecting switch structure, which is designated generally by the reference numeral 55, ineludes the disconnecting contact member 16 which is actu= ated by pressure differences across a piston 56 movable within an operating cylinder 57. Relatively stationary contact fingers 58 bear upon the sides of the movable disconnecting contact 16 to transmit current therethrough from a cylinder head 59. The cylinder head 59 is electri cally and mechanically connected to the base 7 by a conducting and supporting member 60. The resistor 15 is connected to the support plate 8 by a conductor 64. The plate 8 is connected to the main interrupter unit 12 by means of a conductor 65.

In the closed circuit position of the breaker as shown in V the drawing, the current path extends through the terminal conductor enclosed by one of the terminal bushings 5, the support plate 8, the conductor 65 and through the closed contacts 11, 12 and 13 to the conducting base 7. The current path then extends through the conducting member 60, the disconnecting contact structure 55 and the contact member 16 which engages the contact mem ber 10, and thence to the terminal conductor in the other bushing 5.

The operation of the circuit breaker is controlled by a solenoid operated, three way, normally open trip valve 71, a solenoid operated, straight way normally closed close valve 72 and a gas-pilot operated, three Way, nor= mally closed valve A with an internal bleeder connection, indicated by the dotted line a, between the pilot section and outlet. The valves 71, 72 and A are standard com mercially available air or gas valves. The trip valve 71 is of adequate capacity to exhaust the interrupters at the desired rate. As an alternative, two or more smaller valves may be used in parallel for tripping by connecting the operating coils in series or parallel. Valves B and C are standard, commercially available check valves. One each of valves A, B and C is required for each interrupter. One each of the close and trip valves is required per circuit breaker, or multiple trip valves may be paralleled as indicated above.

An auxiliary switch 73 is operated by a double acting fluid-pressure cylinder 74, the front or stem end of which is connected to the high pressure tank 2 through a pipe 75. Pressurizing or exhausting the rear end operates the piston inside the cylinder due to the piston area difierential. A sensing, or indicating, line 76 from the rear of the cylinder 74 may be connected to the pilot of the isolator control valve A as shown, or directly to the rear of the isolator cylinder 57. In either case the indicating line 76 will indicate the pressure condition controlling the position of the isolator contact 16.

A pressure switch 77, connected to the low pressure reservoir 4 controls the operation of a pump or compressor 78. The switch 77 may be of a type well known in the art. When the breaker opens and high pressure gas is blasted into the low pressure reservoir 4, the change in pressure will operate the switch 77 to start the pump which draws gas from the reservoir 4 through a filter 79 and returns it to the high pressure tank 2, thereby restoring the original differential in pressure between the tank and the reservoir.

In the drawing, the circuit breaker is shown in the closed position. Energizing the solenoid 81 of the trip valve 71 by means of any conventional electrical control scheme through a conductor 82 and contact members 83 of the auxiliary switch 73 closes the valve 71 and exhausts tube 84 leading to the interrupters. This exhausts the high pressure gas from the top of the interrupter pistons into the low pressure chamber 4 through a pipe 85, causing the main contacts 11, the main interrupting contacts 12 and the resistor interrupting contacts 13 to open in sequence and interrupt the current through the circuit breaker. When the main and the resistor interrupters open, the high pressure gas is blasted through the blast tube 14 into the low pressure reservoir 4. As described in the aforesaid copending application, the sequential operation of the interrupters is obtained by means of sleeve valves 86, 87, and 88 in the interrupters 11, 12 and 13, respectively.

Opening the resistor interrupter 13 permits the pilot section 89 of valve A to be exhausted through check valve C and a line 80. Valve A will thus move to its normally closed position, exhausting the isolator cylinder 57 through lines 9t} and 91 into the blast tube 14 and causing the isolator contacts 16 to move to the open position. At this time the sensing line 76 is also exhausted, causing the auxiliary switch 73 to open contacts 83 and close contacts 93. Opening contacts 83 deenergizes the solenoid 81, permitting the trip valve 71 to return to its normally open position. This admits high pressure gas from the tank 2 to the top of the interrupter pistons to reclose the interrupter contacts and the blast orifices. Reclosing the resistor interrupter readmits pressure in the line 80 leading to check valve C. However, the check valve prevents gas flow to the pilot section of valve A. The isolator cylinder thus remains exhausted, maintaining the breaker open position.

Since the tubes from the pilots of valves A for other interrupting units of the breaker all have a common connection at the close valve 72, check valves B are provided to prevent the exhausting of the pilots of all valves A by the first interrupter to open. This interlocks each isolator with its own interrupter.

The closing operation of the circuit breaker is initiated by energizing the solenoid 94 of the close valve 72 through a closing circuit and the contacts 93 of the auxiliary switch 73. This opens the valve 72 admitting pressure from the tank 2 through check valve B to the pilot section 89 of valve A and causing it to move to the open position. High pressure gas is admitted from the tank 2 through an inlet opening 95 in the valve A to the isolator cylinder 57, thereby actuating the piston 56 to cause contact member 16 to engage contact member and close the circuit through the breaker since the interrupters have been recloscd previously. The front of the isolator cylinder is connected to the low pressure chamber at all times through lines 96, 91 and the blast tube 14.

At this time, the auxiliary switch 73 is operated to open contacts 93 and close contacts 83, thereby deenergizing the solenoid 94 which permits the valve 72 to move to its normally closed position. Trapped gas pressure in the pilot section of valve A, maintained by the bleeder connection, holds valve A in the open position, thus maintaining 6 the isolator contacts in the breaker closed position until another tripping operation is initiated.

As previously explained, the circuit breaker may be either a single pole or a multiple pole breaker, each pole unit being similar to the one herein shown and described. Also, a simplified interrupting structure may be utilized in which the main contacts and the resistor interrupter are omitted, only the main interrupter and the isolator being provided for each pole unit.

From the foregoing description, it is apparent that the invention provides a circuit breaker in which an interrupting gas stored in the breaker under pressure is utilized as an operating medium for operating the contact members of the breaker, thereby eliminating a costly mechanism, mechanical links and shaft seals required in prior gasblast circuit breakers.

Also, the arced gas is blasted out through a blast tube into a low pressure chamber and then filtered before being returned to the high pressure tank. Thus, the main parts of the interrupter and the bushings inside the tank are not exposed to the by-products of the arced interrupting gas.

Furthermore, the operation of the breaker is controlled by a small number of standard commercially available valves. The simplicity of the control scheme, with the resulting low cost and maintenance, is an important advantage.

Certain features of the pneumatic control scheme are set forth and claimed in US. patent application Serial No. 416,455, filed Dec. 7, 1964, by William A. Fish, Jr., and James M. Telford, and assigned to the assignee of the present application.

Since numerous changes may be made in the abovedescribed construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A compressed-gas circuit interrupter of the closed circulating type including means defining a pressurized tank containing a highly efficient arc-extinguishing gas under pressure, an interrupting assembly with an exhaust structure and a serially related disconnecting contact structure disposed within said tank including a pair of separable arcing contacts (27, 28) and a pair of seriallyrelated disconnecting switch contacts (10, 16) all disposed within said pressurized tank, a low-pressure tank disposed externally of the aforesaid tank and connected to said exhaust structure, an isolator piston (56) for moving one of said disconnecting switch contacts to the open and closed-circuit positions, a three-way normally-closed first control valve (A) having a gas-operated pilot section (89) for pressurizing or exhausting the closing side of said isolator piston (56) and disposed within the pressurized tank adjacent the disconnecting switch contacts, an operating piston (46) movable within a cylinder for opening one of said arcing contacts, a main exhaust second valve (71) for pressurizing or exhausting the closing side of said operating piston (46), a check-valve-controlled pneumatic line pneumatically interconnecting the closing side of said operating piston (46) with the pilot section (89) of said first control valve (A), and a check-valve-controlled pneumatic line pneumatically interconnecting the pilot section (89) with a two-way normally-closed third close valve (72) to pressurize the pilot section (89) and thereby open the first control valve (A) to close the isolator piston (56).

2. The combination according to claim 1, wherein a main contact structure (11) and a main arcing contact structure (12) is in electrical parallel with said pair of separable arcing contacts.

3. The combination of claim 2, wherein a resistance is disposed serially in circuit with the last mentioned pair of separable arcing contacts (27, 28).

4. The combination according to claim 1, wherein a pressure switch controls a pump to raise the pressure of gas from the low-pressure tank to the level requisite for feeding into the pressurized tank.

References Cited UNITED STATES PATENTS 2,459,600 1./ 1.949 .Strom 200148 8 10/1960 Caswell et al. 200-148 11/1961 Schrameck et al 200148 10/1965 Schrarneck et a1. 200-145 FOREIGN PATENTS 3/ 1960 France. 11/ 1946 Great Britain.

ROBERT S. MACON, Primary Examiner.

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