US3646295A

US3646295A - Synchronous circuit interrupter

Info

Publication number: US3646295A
Application number: US12206A
Authority: US
Inventors: Robert Ray Circle
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1970-02-19
Filing date: 1970-02-19
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28
Also published as: JPS5211031B1; JPS461569A

Abstract

In a circuit breaker, main current carrying contacts are in parallel with secondary or synchronous interrupter contacts, and an isolating switch is in series with both the main contacts and the synchronous interrupter. The synchronous interrupter is switched into the circuit when the main contacts open and interrupts the current at a current zero after the opening of the main contacts. The synchronous contacts are operated by electrodynamic drive means controlled by a current zero anticipator of a static type. The synchronous contacts can be small and light to facilitate synchronous operation since they carry the fault current only for the time between the opening of the main contacts and interruption of the fault.

Description

waited States Eatent Feb. 29, 1972 Circle [54] SYNCHRONOUS CIRCUIT INTERRUPTER [72] Inventor: Robert Ray Circle, Woodbridge, Va.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

[22] Filed: Feb. 19, 1970 [2]] Appl. No.: 12,206

[52] U.S.Cl ..200/l48.],307/133,3l7/ll A, 335/ 19 [51] Int. Cl. ..Hlh 33/82 [58] Field ofSearch ..307/133;317/ll A; 200/l46 A,

200/146 R, 148 J; 335/19; 200/148 A [56] References Cited UN lTED STATES PATENTS 3,215,866 11/1965 Kesselring et al. ..200/l48 .1 3,390,240 6/1968 Circle et al ..200/l48 A 3,449,537 6/1969 Kesselring ..200/l48 A- FOREIGN PATENTS OR APPLICATIONS 1,142,201 1/1963 Germany ..200/148 A Primary ExaminerJarnes D. Trammcll At!0rneyA. T. Stratton. Clement L. McHule and Willard R. Crout 57 ABSTRACT in a circuit breaker, main current carrying contacts are in parallel with secondary or synchronous interrupter contacts, and an isolating switch is in series with both the main contacts and the synchronous interrupter. The synchronous interrupter is switched into the circuit when the main contacts open and interrupts the current at a current zero after the opening of the main contacts. The synchronous contacts are operated by electrodynamic drive means controlled by a current zero anticipator of a static type. The synchronous contacts can be small and light to facilitate synchronous operation since they carry the fault current only for the time between the opening of the main contacts and interruption of the fault.

7 Claims, 4 Drawing Figures i 5 I? L z 7 96 37 ii i 66 5 18 87 HIGH 92 73 j T PRESSURE 4e a 2 RESERVOIR 83 74 COMPRESSOR L 37 40 1e 7 5:

Patented Feb. 29, 1972 3,646,295

2 Sheets-Sheet l II I IIII llllllllll on go (o LL. E 2

Patented Feb. 29, 1972 3,646,295

2 Sheets-Sheet I HIGH PRESSURE RESERVOIR 1 SYNCHRONOUS CIRCUIT INTERRUPTER BACKGROUND OF THE INVENTION This invention relates, generally, to circuit interrupters and, more particularly, to interrupters of the synchronous type which are opened slightly before a current zero of an alternating current wave. 7

One of the problems encountered when building a circuit breaker having a synchronous interrupter is that of providing contact members heavy enough to carry large amounts of current yet light enough to permit them to be opened in the short time available for synchronous operation. A circuit breaker described in a copending application, Ser. No. 435,557, filed Feb. 26, 1965, now US. Pat. No. 3,390,240, issued June 25, 1968 to R. R. Circle and T. O. Prunty, and assigned to the Westinghouse Electric Corporation is provided with main or nonsynchronous contacts and secondary or synchronous contacts which are connected in parallel-circuit relation when the breaker is closed. The main contacts normally carry most of the current since they are of a heavier construction and provide a shorter path having a low-voltage drop through the breaker. When the breaker begins to open, all of the current is shunted through the secondary contacts which are opened just prior to a current zero by gas pressure developed by a puffer and controlled by a valve operated by a synchronous operator. The same puffer supplies gas to extinguish the arc drawn either at the synchronous contacts, which interrupt high fault currents, or at the nonsynchronous contacts, which interrupt currents too low to operate the synchronous operator. The

puffer is driven by the mechanism which operates the main contacts of the circuit breaker.

SUMMARY OF THE INVENTION In accordance with one embodiment of the invention, a circuit breakerhas main current carrying contacts in parallel with secondary or synchronous interrupter contacts, and isolating contacts in series with both the main and the secondary contacts. The synchronous interrupter is switched into the circuit when the main contacts open and interrupts the current at a current zero after the opening of the main contacts. Thus, the synchronous interrupter is required to carry the fault current only for the time between the opening of the main contacts and interruption of the fault. Therefore, the synchronous contacts can be small and light to facilitate synchronous operation. The synchronous contacts are operated by electrodynamic drive means controlled by a current zero anticipator of a static type.

BRIEF DESCRIPTION OF THE DRAWINGS.

For a better understanding of the nature of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a circuit breaker and electrodynamic operating mechanism and control embodying principal features of the invention;

FIG. 2 is a view, in section, of a modified operating mechanism for a synchronous interrupter; and

FIGS. 3 and 4 are views, in section, of a valve utilized in the mechanism shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, particularly to FIG. 1, the circuit breaker structure shown therein comprises a housing 10,

terminal bushings

11 and 12 mounted on the housing 10, main or nonsynchronous contact means 13, a synchronous interrupter 14 comprising secondary contact means 15 and electrodynamic drive means 16 for operating the secondary contacts 15, capacitance energy storage means 17 for energizing the electrodynamic means 16, and current zero anticipating means 18 for controlling the energization of the electrodynamic means 16. The housing'or tank 10 contains an interrupting medium, preferably sulfur hexafluoride (SF gas, at a relatively low pressure. Other interrupting gases, even air, may be utilized if desired.

The main contact means 13 includes a relatively movable main contact member 19, a relatively stationary contact finger assembly 21, an orifice member 22 having an arcing ring 23 disposed in a generally cylindrical throat 24 of the orifice member, a generally cup-shaped member 25 movably disposed in the finger assembly 21, a contact finger assembly 26 slidably engaging the movable contact member 19 and an insulating member 27 having one end attached to the movable member 19 and the other end connected by means ofa link 20 to an external operating mechanism (not shown). The external operating mechanism may be of a type well known in the circuit breaker art.

The finger assembly 26 is mounted in an insulating body member 28 and the assembly 26 is electrically connected to a portion 29 of the terminal bushing 12. The cup-shaped member 25 is biased outwardly in the finger assembly 21 by a compression spring 31. The finger assembly 21 is connected to a conductor 32 and also to a portion 33 of the terminal bushing 11. The

bushings

11 and 12 may be connected to suitable power conductors. The main contact members are of a relatively heavy construction. Thus, when the movable contact member 19 is closed to engage the member 25 and then the fingers 21, a current path having a relatively low resistance and low-voltage drop is provided through the circuit breaker from the terminal bushing 11 to the terminal bushing 12.

When the main contacts are fully open, they perform the function of a series isolating switch. With the proper match between the main contact velocity and the distance between the stationary main contact and the arcing ring, arcing across the isolating contact can be eliminated, except in the case of load break switching and low level fault interruption. The secondary contacts 15, which are normally closed, are in parallel-circuit relation with the main contacts and the isolating switch is in series-circuit relation with both the main current contacts and the secondary or synchronous contacts. The main current contacts are constructed to meet all current carrying requirements, while the isolating switch meets the open circuit voltage requirements and interrupts load currents and faults below a predetermined amount, for example, 5,000 amperes. The synchronous interrupter 14 is switched into the circuit when the main current contacts open and interrupts the current at a current zero after the opening of the main con tacts. Thus, the synchronous interrupter is required to carry the fault current only for the time between the opening of the main contacts and interruption of the fault. Therefore, the synchronous contact can be quite small and light to facilitate synchronous operation.

The synchronous interrupter 14 comprises a generally cylindrical metal housing 34 which is closed at the lower end by a flanged terminal member 35 and at the upper end by an insulating disk 36. The housing 34 is connected through a pipe 37 to a high pressure reservoir 38 which supplies the interrupting medium to a region 39 within the housing 34. The interrupting medium may also be supplied to the main contact means 13 through a branch of the pipe 37. The medium is withdrawn from the housing 10 and returned to the reservoir 38 by a compressor 40.

The secondary contact means 15 comprises a hollow cylindrical stationary contact 41 which is secured in the disk 36 by means of a flanged ring 42, and a movable contact member 43 which closes the lower end of the stationary hollow contact 41 when the movable contact is in the closed position. A seal 44 engages a flange 45 on the movable contact 43 to close the entrance to the cylindrical member 41. When the movable contact 43 is opened, the interrupting gas flows from the region 39 through the contact 41 to interrupt the arc and is vented into the tank 10 through openings 46 in the side wall of the cylinder 41.

The movable contact 43 is carried by a reciprocating armature 47 having a shaft or stem 48 and a round base 49. The

stem 48 is slidably disposed in an insulating guide member 51 which may be threaded into the housing 34. The base 49 of the armature 47 is connected to a flange 52 on the terminal 35 by means of a flexible copper disk 53. The current path through the interrupter is from the conductor 32, which is connected to the terminal 35, through the flexible disk 53, the armature 47, the movable contact 43 and the stationary contact 41, current transformer

primary windings

54, 55 and 56, and a conductor 57 which is connected to the arcing ring 23.

The armature 47 is actuated downwardly to open the contact members by means of a repulsion coil 58 and upwardly by a repulsion coil 59 which assists a spring 61 in reclosing the contact members. Downward movement of the armature is stopped by a shock absorber 62 mounted on the terminal base 35. The coil 58 is retained on the lower side of the guide member 51 by a flanged retaining ring 63. The coil 59 is mounted on the upper side of an insulating washer 64 disposed inside the flange 52 on the base 35.

Contact motion is produced by discharging a capacitor 65 through the opening coil 58. This induces a current in the armature base 49. The armature current reacts with the magnetic field of the current in-the coil 58 producing the force which opens the contacts. A relatively high velocity in a short period of time is obtained. The moving contact 43 will be stopped by the shock absorber 62 with the armature base 49 close to the reclosing coil 59 at about the time the fault current reaches zero.

If the interrupter should fail to interrupt and pass up a current zero, the reclosing coil 59 is energized by current in the secondary winding 66 of a current transformer, the primary winding 54 of which is in series with the

synchronous contacts

41, 43. This current transformer is so constructed that the core saturates a few milliseconds after the fault current goes through zero and remains saturated until the fault current reaches zero again one-half cycle later. As the current reverses, the flux in the core goes to saturation in the other direction, producing an emf which energizes the closing coil 59. Preferably, each

coil

58 or 59 is wound of a single spiral of thin, flat copper strip. This arrangement provides the highest possible current density in the core and evenly distributes the electromechanical force over the entire coil.

The capacitor 65 which energizes the opening coil 58 is charged through a full wave bridge rectifier 67 by the current in the secondary winding 68 of a current transformer, the primary winding 55 of which is in series with the synchronous interrupter 14. The charging is done during the half cycle prior to the current zero at which the synchronous interrupter 14 is to operate.

The core of the capacitor charging transformer is built with a small airgap to provide enough reluctance in the magnetic circuit to prevent the core from remaining saturated when no ampere turns are applied. if the core were to remain saturated with no applied M.M.F., a fault current might flow for as long as one-half cycle, or longer if the current is asymmetrical, in the direction to increase the flux in the already saturated core and produce essentially no output from the current transformer. The small air gap will cause the magnetic flux to be zero initially, and thus able to shift to saturation in either direction. By making the core of the proper size, and winding the correct number of turns on the secondary, a condition is obtained where the magnetic flux must shift from zero to saturation, and then back to zero again, to bring the capacitor to the proper charge.

Thus, at least one half cycle of fault current must flow after the first current zero to bring the capacitor to full charge for the first operation. This condition insures against the possibility of a current zero and an interruption occurring before the main current contacts have separated sufficiently to withstand recovery voltage. The current transformer is so constructed that a half cycle of current of 5,000 amperes or more is adequate to shift the magnetic flux in the core from saturation in one direction to saturation in the other. Thus, when the interrupter operates at current zero, the core can be expected to be saturated.

If the breaker fails to interrupt, the magnetic flux will be shifted to saturation in the opposite direction, bringing the capacitor 65 to a full charge for another operation at the next current zero. A nonlinear resistor 69 is connected in series with another winding 71 on the core to prevent ovcrvoltages across the capacitor 65, particularly likely to occur during the half cycle just before the first operation. In all other cases, overvoltage is limited by the saturation of the current transformer.

The capacitor 65 is discharged through the coil 58 and two trinistors; or silicon controlled rectifiers, 72 and 73 connected in series. The discharging of the capacitor is controlled by the current zero anticipator 18. The current zero anticipator 18 comprises a resistance-inductance network which includes a resistance 74 and an inductance 75 energized by the current in the secondary winding 76 of a current transformer, the primary winding 56 of which is connected in series with the synchronous interrupter 14.

The resistance-inductance network produces a relative phase shift between the parallel components of the current produced by the current transformer, with the current in the resistance element leading and the current in the inductance element lagging the line current. The current zero of the resistive current therefore anticipates the current zero of the line current. The resistive current zero is detected by two oppositely poled silicon diodes 77 and 78. This signal is amplified with a germanium transistor 79, rectified by a transformer 81 and rectifiers 82, and sent through a control trinistor 83 to fire the trinistors 72and 73, and discharge the capacitor 65 to energize the opening coil 58. A capacitor 84 is connected between the gate of'the trinistor 72 and ground to aid in the firing of the trinistors.

The amplified signal from the current zero anticipator 18 produced by the transistor 79 is proportioned to the voltage on the energy storage capacitor 65. If the capacitor is adequately charged to provide enough energy to the opening coil 58 to produce proper operation, the signal from the current zero anticipator 18 will break through the control trinistor 83 and energize the switching transistors 72 and 73. If the energy storage capacitor 65 is not adequately charged, the control trinistor 83 will not be broken down and the switching trinistors 72 and 73 will not be energized or fired.

A germanium diode 85, connected between the silicon diodes 77 and 78 and common or ground is matched with the transistor 79. The germanium diode 85 cooperates with the silicon diodes 77 and 78 to provide a biasing voltage on the transistor 79 so that it will switch from conducting to nonconducting as precisely as possible at the exact instant that the resistive current goes to zero. This proper matching is necessary to eliminate variation in the anticipation of line current zero at varying levels of line current. When the transistor 79 becomes nonconducting, a capacitor 86 is charged. This provides suffi-' cient voltage to fire the control trinistor 83-which, in turn, fires the switching transistors 72 and 73.

Biasing resistors

87, 88, 89 and 91 are provided with the current zero anticipator 18. A volt trap including a Zener diode 92, resistors 93 and 94,

diodes

95 and 96, and

resistors

97 and 98 is provided with the capacitance means 17.

A modified synchronous interrupter 14 is shown in FIG. 2. The structure shown therein comprises two cylinders 101, two pistons 102, two valves 103, two repulsion coils 104, two valve guides 105, a housing 106 which is closed at the ends by two members 107, and a high pressure reservoir 108 which is connected to the cylindrical housing 106 by pipes 109. As shown, the pistons 102 are disposed at opposite ends of the housing 106. The pistons 102 have stems 111 which are joined by a sleeve 112 into which the ends of the stems are threaded. The structure of each valve 103 is shown more clearly in FIGS. 3 and 4. Each valve 103 comprises a spider 1 13 having a flanged rim 114 and a hollow stem 115.

As shown in FIG. 2, each valve stem 115 is slidably disposed in one of the valve guides and each piston stem 111 is slidably disposed inside one of the valve stems 115. A movable contact member 43', similar to the movable contact 43, is attached to a reciprocable extension 116 on the upper piston 102. The movable contact member 43 engages a relatively stationary, hollow cylindrical contact member 41' when in the closed position. When the movable contact 43 is opened, the arc is interrupted in the manner hereinbefore described. The interrupting gas is supplied to the region 39 from the reservoir 108. A conductor 32 is connected to a base 117 of a contact finger assembly 118 which slidably engages an extension 116 on the lower piston 102. A transformer 54 is connected to the stationary contact 41 Thus, the modified synchronous interrupter 14' may be utilized in place of the synchronous interrupter 14.

As shown in FIG. 2, the repulsion coil 104 at the bottom of the structure functions as the opening coil and the coil 104 at the top of the structure functions as the closing coil. The opening coil 104 may be energized by a capacitor discharged in the manner hereinbefore described, and the closing coil 104 may be energized by a saturating current transformer in the manner hereinbefore described. Each coil operates one of the valves 103. When the coil is energized, a current is induced in the rim of its respective valve. This current reacts with the magnetic field of the current in the coil producing the force which operates the valve. The valves are provided with a pneumatic boost so that the repulsion coil need only crack the valve and the pneumatic boost will being the valve to the fully open position. The device is capable of opening and reclosing a circuit breaker in a few milliseconds. [f the breaker should fail to interrupt at the first current zero, the mechanism is capable of reclosing the breaker'and attempting interruption at successive current zeros.

To open the separable contact members of the synchronous interrupter, the coil 104 at the lower part of the structure is energized as described above. The rapidly rising current in the coil induces a current in the rim of the valve which reacts with the current in the core to produce a force to open the valve. As soon as the valve is cracked," high-pressure gas from the reservoir 108 will flow between the coil and the valve, forcing the valve to the full open position. High pressure gas then flows onto the lower piston 102, developing the force to open the contact members of the interrupter 14'. As the gas flows onto the piston 102, it also flows through passageways 121 in the valve guide 105 to balance the gas pressure on the respective valve so that the valve may be reclosed by a spring 122 without damage. The spring 122 which recloses the valve is constructed to be stiff enough to hold the valve closed when the high pressure gas fills the gas reservoir and to reclose the valve at about the time the piston clears exhaust ports 123. The ports 123 exhaust gas from the cylinder 101 into the tank which contains the interrupter or to atmosphere in case it is not desired to reuse the gas. The lower opening piston 102 then continues its travel until it comes to a halt at the bottom of the cylinder 101 where it is cushioned by means of an airpocket vented through small openings 124 in the lower cylinder end 107.

This travel brings the other upper piston 102 at the upper end of the mechanism to the minimum volume position of its cylinder 101. Then, if the interrupter fails to interrupt at current zero, the upper closing coil 104 is energized in the manner hereinbefore described to operate the upper closing valve 103 to effect immediate reclosure. The operation of the mechanism at the top of the structure to provide reclosure is the same as the first operation to open the contacts of the synchronous interrupter. The synchronous interrupter may be closed initially by a suitable operating mechanism.

The pistons may be composed of a light-weight highstrength material, such as aluminum or an alloy thereof, and they may be provided with sufficient area for a predetermined pneumatic pressure to provide sufficient force to operate the contact members of the synchronous interrupter at a high speed. Thus, the mechanism is capable of synchronously opening and reclosing a circuit interrupter within a few milliseconds.

From the foregoing description it is apparent that'the invention provides a circuit breaker having a combination of switching elements for segregating the essential functions of interrupting a circuit and isolating the elements. Automatic discrimination between conditions requiring synchronous operation and those requiring only asynchronous opening is provided. in one form, the tripping and reclosing energy is obtained solely from the current to be interrupted, the energy being stored momentarily in a condenser. in an alternate form this energy may be supplemented by stored gas pressure, using the medium which is utilized for interrupting the arc drawn between the contact members of the circuit interrupter. The interrupter is so constructed that it may be operated at a high speed, thereby making it suitable for synchronous operation.

I claim as my invention:

1. A synchronous-type circuit interrupter controlling an electrical circuit including a relatively stationary contact, a relatively movable contact, an operating member for operating the movable'contact, electrodynamic driving means including an opening electrodynamic drive, said opening electrodynamic drive including a repulsion-coil means for causing opening operation of the operating member, a current-transformer having a primary winding connected serially into said controlled circuit and having a secondary winding, a charging capacitor, rectifier means for rectifying the current in the secondary circuit of said current transformer, circuit means for feeding therectified current into said charging capacitor, and means defining a synchronous operator for controlling the proper time of discharge of the capacitor into said repulsioncoil means at a predetermined time prior to current zero in said controlled circuit.

2. The synchronous-type circuit interrupter of claim 1, wherein a second closing electrodynamic drive is provided including a second repulsion-coil means, a second saturating current transformer is provided having a primary winding also connected serially into said controlled circuit and having a secondary winding, and other circuit means for feeding secondary current from said second saturating current transformer into said second repulsion-coil means to effect closing of the operating member.

3. The combination according to claim 1, wherein the synchronous operator includes solid-state static devices responsive to the controlled electrical circuit.

4. The combination according to claim 1, wherein the opening electrodynamic drive includes a pressurized region and an opening ring-shaped valve member.

5. The combination according to claim 2, wherein the opening electrodynamic drive includes a pressurized region and a ring-shaped valve member, and the closing electrodynamic drive includes a pressurized region and a second ring-shaped valve member.

6. The combination according to claim 1, wherein a first piston member is fixedly secured to the operating member, means providing a pressurized region, and a ring-shaped opening valve for being repelled by energization of the repulsioncoil means. I

7. The combination according to claim 2, wherein the operating member has two pistons fixedly secured thereto, the opening electrodynamic drive includes a pressurized region and a ring-shaped valve member being repelled by the first repulsion-coil means, and the second closing electrodynamic drive includes a pressurized region and a second ring-shaped valve member which is repelled, at times, by the second repulsion-c0il means.

Claims

1. A synchronous-type circuit interrupter controlling an electrical circuit including a relatively stationary contact, a relatively movable contact, an operating member for operating the movable contact, electrodynamic driving means including an opening electrodynamic drive, said opening electrodynamic drive including a repulsion-coil means for causing opening operation of the operating member, a current-transformer having a primary winding connected serially into said controlled circuit and having a secondary winding, a charging capacitor, rectifier means for rectifying the current in the secondary circuit of said current transformer, circuit means for feeding the rectified current into said charging capacitor, and means defining a synchronous operator for controlling the proper time of discharge of the capacitor into said repulsion-coil means at a predetermined time prior to current zero in said controlled circuit.

6. The combination according to claim 1, wherein a first piston member is fixedly secured to the operating member, means providing a pressurized region, and a ring-shaped opening valve for being repelled by energization of the repulsion-coil means.

7. The combination according to claim 2, wherein the operating member has two pistons fixedly secured thereto, the opening electrodynamic drive includes a pressurized region and a ring-shaped valve member being repelled by the first repulsion-coil means, and the second closing electrodynamic drive includes a pressurized region and a second ring-shaped valve member which is repelled, at times, by the second repulsion-coil means.