US3531609A

US3531609A - Electrical circuit breaker

Info

Publication number: US3531609A
Application number: US630303A
Authority: US
Inventors: Jean Louis Gratzmuller
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-04-15
Filing date: 1967-04-12
Publication date: 1970-09-29
Anticipated expiration: 1987-09-29
Also published as: ES339719A1; AT284946B; BE696503A; NL6705071A; CH462922A; GB1169459A; DE1640215A1; NL151207B; SE336159B; FR1537673A; SU516359A3

Description

p 1970- J. 1.. GRATZMULLER v 3,531,609

I ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 e Sheets- Shet 1 Sept. 29, 1970 GRATZMULL-ER 3,531,609

ELECTRICAL CIRCUITV'BREAKER Filed April 12, 1967 6 Sheets-Sheet 2 -FIG.2

Sept. 29, 1970 J. 1. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 6 Sheets -Sheet 3 Sept. 29, 1970 J. L. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER I Filed April 12, 1967 6 Sheets-Sheet &

v I27 15246 I e 90 I 'iMliH S t. 29, 1910 J. L. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 6 Sheets-Sheet 5 p 1970 J. GRATZMULLER 3, 3 0

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 e Sheets-Sheet s United States Patent O M 3,531,609 ELECTRICAL CIRCUIT BREAKER Jean Louis Gratzmuller, 66 Boulevard Maurice Barres, Neuilly-sur-Seine, Hauts-de-Seine, France Filed Apr. 12, 1967, Ser. No. 630,303 Claims priority, application France, Apr. 15, 1966,

Int. Cl. rionl 33/68 US. Cl. 200150 13 Claims ABSTRACT OF THE DISCLOSURE BRIEF SUMMARY OF THE INVENTION This invention relates to electrical circuit breakers especially but not exclusively to circuit breakers for use in high and very high voltage circuits.

An object of the invention is to operate the cut in the arc in a dielectric medium consisting of a liquid under permanent pressure, as a result of which, certain characteristics of the dielectric medium, such as the extinguishing power and the dielectric rigidity are improved which allows better performances in the breaking and/or a lessening of the volume of the dielectric and so of the apparatus.

A further object of the invention is to use the energy contained in the form of pressure in the dielectric liquid under pressure, this constantly available pressure being utilized to operate the moving contact of the circuit breaker in the direction of separating the contacts, i.e., for the release.

As a result, as soon as the moving contact is no longer held in the closed position by the locking devices or the normal holding devices (mechanical, hydraulic, pneumatic, etc.) this contact is pulled and separated from the fixed contact to produce the break.

The present invention is an electrical circuit breaker comprising a circuit interrupting chamber in which are arranged a fixed contact and a movable contact and which contains a liquid dielectric, resilient means for keeping said liquid dielectric under permanent pressure, a breaking piston solid with the movable contact, a cylinder in which the piston slides and communicating at the end turned towards the moving contact with the circuit interrupting chambers, releasable interlocking devices to bring and maintain selectively the movable contact against the fixed contact in opposition to the pressure of the liquid dielectric exerted on the breaking piston.

Preferably the insulating liquid is a liquefied gas having a high dielectric strength, such as sulphur hexafiuoride SP Preferably also, the resilient means for maintaining the insulating under pressure, is a pneumatic device such as a cushion of gas under pressure acting on the dielectric liquid directly or through a hydraulic line; alternatively, it is a mechanical device such as a spring pushing a piston which compresses the dielectric liquid of the circuit breaker.

According to certain preferred embodiments of the invention the resilient devices for maintaining pressure comprise a hydraulic accumulator, the same accumulator being used, in certain cases as a pressure source for con- 3,531,609 Patented Sept. 29, 1970 tinuously maintaining the insulating liquid under pressure and as a pressure for controllably moving the movable contact of the circuit breaker to closed position against the action of the continuously maintained pressure.

In practice, there can be fitted to circuit breakers in accordance with the invention, devices for controlling the pressure and the volume of the dielectric liquid as well as devices for compensating variations in pressure and volume arising, for example, from variations in temperature.

In a circuit breaker according to the invention, a very effective deionization of the medium is effected Where the arc sparks due to the pressurizing of the liquid dielectric. In addition, the pressure existing in the dielectric acts against cavitation phenomena which normally arise as the moving contact withdraws. The deionization and anticavitation thus obtained due to the invention are all the more elfective because of the high pressure of the liquid dielectric. This deionization can be made even more effective by circulating dielectric under pressure right at the heart of the arc, circulation producing a hydraulic blow and being very simply obtained in a circuit breaker according to the invention.

BRIEF DESCRIPTION OF THE DRAWING Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of a circuit breaker in which the resilient devices for pressurising the dielectric are made up of a cushion of gas under pressure acting directly on the free level of the dielectric;

FIGS. 2 and 3 represent in section two variations of the circuit breaker in which the resilient devices are made from a spring acting on a piston which directly compresses the dielectric;

FIG. 4 is a partial sectional view of a circuit breaker similar to those of FIGS. 1, 2 and 3 but having in addition a hydraulic system for blowing the arc;

FIGS. 5 and 6 are partial sectional views of circuit breakers similar to those of FIGS. 1 to 4 but including accessory devices for control, compensation and safety;

FIG. 7 is a more complete partial sectional view of a hydraulic control circuit which also maintains pressure according to another embodiment of the invention; and

FIG. 8 represents another variation of the invention in which the same elastic devices elfect the pressure maintenance of the hydraulic fluid of the control circuit of the breaker as well as the pressure maintenance of the liquid dielectric.

DETAILED DESCRIPTION Referring to the drawings, the circuit breaker shown in FIG. 1 has a cutting chamber 2 in which are arranged, as is normal, a fixed contact 4 linked to a current feed cable 6, and a movable contact 8 which can slide in a contact jaw 10 linked to a current exit cable 12. p

In the embodiment shown the circuit interrupting chamher 2 is mounted on the top of an insulating column 14 elongated at its lower part by a cylinder 16 into which can slide a piston or breaking piston 18. This piston is linked to the movable contact 8 by an insulating rod 20 and an intermediate rod 22. The lower face of piston 18 is subject to atmospheric pressure by means of openings 19 in cylinder 16. Fluid-tight joints are interposed at the junctions between cylinder 16, the diiferent elements of column 14 and the circuit interrupting chamber 2. This latter is surmounted by a fluid-tight compartment 24 supplied with a liquid level 26. The above assembly forms a fluid-tight space, the space of the circuit interrupting chamber 2 and of compartment 24 linking with the space of the insulating column 14, for example, by an opening 3 28. Thus, the movable contact 8 does not need to slide in a fluid-tight manner through the bottom 30 of the cutting chamber 2.

The whole of the above space is filled with a dielectric liquid 32 which is kept permanently under pressure by resilient means comprising in this embodiment a cushion of gas 34 under pressure (for example air, but preferably nitrogen) occupying the upper part of compartment 24 and acting directly on the free level 36 of the liquid dielectric.

One end of cylinder 16 is turned towards the movable contact 8 (i.e. the upper end of this cylinder) and communicates with the space filled with pressurized liquid dielectric. This means that the breaking piston 18 is permanently subject to a force directed downwards and equal to the product of the pressure of the dielectric multiplied by the surface of the piston, this force tending to push the movable contact 8 from the fixed contact 4 and, as a result, releasing the circuit breaker.

The breaker also comprises, as is normal, releasable interlocking devices modified to bring and maintain selectively the movable contact against the fixed one.

These hydraulic interlocking devices may comprise an interlocking screw 38 (pressure cylinder) of which the piston 40 of the plunger piston type, is linked by translation to the breaking piston 18 by a linkage 41. The screw 38 can be selectively supplied with oil under pressure or drained by a system of hydraulic commutation shown in the drawing by a three-way gate 42. The circuit is completed by a hydraulic accumulator 44, for example oleo-pneumatic, fed from a pump 46 which extracts the oil from a tank 48 acting as a draining tank. The three-way gate 42 is a selector valve permitting connection of the pressure cylinder 38 to the hydropneumatic accumulator 44 or to the reservoir 48.

In the interlocked position of the circuit breaker shown in FIG. 1 the oil pressure of accumulator 44 operates in the interlocking screw 38 and holds the moving contact 8 against the fixed contact 4 as long as the gate 42 stays in its feed position shown against the pressure of the liquid dielectric 32 which acts on the operating piston 18.

As soon as the screw 38 is drained by operating gate 42 the pressure of the gas cushion 34 transmitted by the liquid dielectric 32 pushes the breaking piston 18 downwards and separates the movable contact from the fixed one.

In a breaker of the invention an elastic force is always available ready to effect the break, which is an important safety factor, and, in addition, the harmful phenomena of cavitation when the moving contact withdraws are considerably reduced or even eliminated due to the pressurizing of the liquid dielectric which feeds with fresh dielectric the empty space left at the break by the moving contact.

In a breaker of this type, insulating oil for circuit breakers may be used 'as liquid dielectric but it is more advantageous to use a liquified dielectric gas since elastic pressurizing devices are already available, which will liquify the gas, and these dielectrics have better features than oil. Particularly good results are obtained from the gas SF (sulphur hexafluoride), pressurizing being effected by an elastic cushion of gas 34, for example nitrogen, having a higher liquefaction pressure than SP In accordance with the invention the resilient pressurizing devices for the dielectric act both as continually available breaking devices and as devices for keeping the dielectric gas in the liquid state.

A circuit breaker of the invention can be completed by certain control devices or safety devices such as: the visible level 26 which allows a visual check on the amount of dielectric (the level of SP being visible like a water level); a safety valve 50; a draining valve 52; a filling valve '54 which can be used to extract air during installation by means of nitrogen before the first filling and to elfect the filling with ISF6 and nitrogen; and a control device 56 for the pressure of the liquid dielectric.

In a. modification shown in FIG. 2 only the top part of the breaker has been shown, since the lower part with the breaking device can be identical to that of FIG. 1 or any other standard type.

In this modification the resilient devices for pressuriz ing the liquid dielectric are not pneumatic (such as the cushion of nitrogen 34 in FIG. 1) but mechanical being made up of a spring 58 which acts through a linkage 6062 on a piston 64 sliding in a cylinder 66.

The internal space of the cylinder 66 communicates with the closed space 32 of the circuit breaker, this space being entirely filled, right up to the top 68 of the compartment 24, with liquid dielectric such as liquified SF It is more suitable to arrange cylinder 66 and the spring 58 in the lower part of the breaker since this allows, by means of a graduated rod 70 solid with the piston 64, a check on the volume of liquid dielectric contained in the installation. Due to the choice of section of piston 64, the spring 58 need have only a low rate of displacement during the breaking.

Thus a breaker is obtained with breaking by spring but in which the effort of the spring is transmitted hydraulically without any need for mechanical reduction and in which the same spring effects the pressurizing (and in particular the liquifying) of the dielectric.

In the embodiment shown in FIG. 3 the resilient pressurizing devices for the liquid dielectric comprise, as in FIG. 2, a spring-piston system, but this system is mounted in the upper part of the breaker, since the cylinder 65 in which the piston 64' slides is mounted above the circuit interrupting chamber 2, i.e., in place of compartment 24 of FIGS. 1 and 2. The spring 58' is supported on a fixed flange 72 mounted on the top of the breaker by ties 74, the other end of the spring acting on a movable flange 76 solid in translation with piston 64' due to ties 78, a wall-plate 80 and a push rod 62'. As a result of this arrangement a spring 58' of a diameter larger than the bore of cylinder 65 can be used.

In the embodiment shown in FIG. 4 the resilient pressurizing devices act directly on the liquid dielectric contained in the circuit interrupting chamber 2, as has been described with reference to FIGS. 1 and 3, but the communication between the internal space 82 of the circuit interrupting chamber 2 and the internal space 84 of the insulating column 14 is no longer by a large communicating orifice such as 28 in the base 30' of the cutting chamber. This communication is effected by a channel 86 which is bored in the rod of the movable contact 8 and which opens out at one end into space 82 through the top of the movable contact and at the other end into space 84 by the orifices 88. The movable contact slides in fluid-tight manner in the base 30' (or at least with some clearances of total section lower than the section of channel 86) with the result that at breaking an intensive circulation of liquid dielectric takes place through channel 86 which causes a hydraulic blast of the arc jumping between the end of the moving contact and the fixed contact 4'.

In FIG. 5 is shown a device for regulating the pressure of the liquid dielectric in a breaker of the invention. This device can be applied to any of the preceding embodiments which is why only one part of the insulating column 14 and one part of the cylinder 16 in which the breaking piston 18 slides have been shown. One couplesto the space of the breaker enclosing the liquid dielectric, for example to the internal space 84 of insulating column 14, one of the ends of a cylinder 90 in which slides a free piston 92 and the other end of which is coupled to an oil hydraulic circuit of constant pressure 93. To sum up, the compartment 94 of the cylinder 90 contains liquid dielectric under pressure, e.g., liquid SF while compartment 96 contains oil. Circuit 93 can comprise a pump 98 driven by an electric motor 100, an oil tank 102 and a pressure switch of manostat 104 which is sensitive to the pressure in compartment 96 and whose contacts 106 close to operate motor 100 when the pressure falls below a predetermined value P.

If there is a drop in temperature leading to a contraction of the liquid SP or if there is a leak of the SP or, as in the FIG. 1 embodiment, a leak of the gas in the cushion 34, the pressure switch detects a fall in pressure. Below pressure P the pump 98 sends oil into compartment 96 until pressure is re-established. In this embodiment the piston-cylinder system 90-92 serves only to regulate (which can be slow) without motivating the break, which is why the tubing 108 has only a very small section compared to that of tubing 66 (FIG. 2) which links cylinder 66 with the internal space of the breaker.

If, on the other hand, there is a rise in the pressure of the liquid dielectric caused, say, by a rise in temperature, this increase in temperature is transmitted to the oil compartment 96 and a safety valve 109, linked to compartment 96 by channelling -111, drains oif the excess oil to tank 102.

The regulating device above described can be completed by a simple gauging device comprising a cock 110 and a graduated receptacle 112. By opening cock 110 the oil compartment 96 can be emptied and the quantity of oil therein measured. From this the position of piston 96 and, consequently, the amount of SP can be found. Two cocks 114-116 permit insulation of pump 100.

FIG. 6 shows another device for compensation and regulation of pressure for a breaker of the invention.

This device comprises, as in the preceding case, a cylinder 90' separated by a piston in two compartments: one, 94 communicates by a pipe 108 with the space 84 of the breaker and the other 96' is coupled to a circuit of oil under constant pressure 93. In this embodiment the piston 92' is fitted with an exiting rod 118 which is graduated and lets one know the amount of oil and thus the SE; in the installation.

A pressure switch 104 controls, as in the preceding embodiment, the operation of the motor 100 of the oil pump 98 if the pressure drops but, in the case of excess pressure (for example, following dilation due to temperature rise), the pressure switch closes its contacts 120 to activate a draining electro-valve 122. The excess oil returns to tank 102 by piping 124. A derived piping system 125 into which is fitted a cock 127 allows one to link up the oil compartment 96' with tank 102 to drain this compartment, particularly when filling the installation.

FIG. 7 shows an embodiment in which is combined the hydraulic interlocking control shown in FIG. 1 with the device for compensation and pressure regulation described in connection with FIG. 6.

The hydraulic interlocking control comprises the parts described above, namely, the cylinder 38 and its piston 40, the oleo-pneumatic accumulator 44, the oil pump 46 and its motor 47, as well as tank 48. A manostat 104 controls the operation of motor 47 of pump 46 if there is a drop in pressure in accumulator 44.

The three-way cock supply-drain, shown schematically in FIG. 1, is replaced by an interlocking electro-valve 42' and by an interlocking electro-valve 42" whose electrical operation will be described hereinafter.

The piston-cylinder system of compensation device 90- 92' is identical to that described for FIG. 6, but the oil compartment 96', instead of being fed by a special system of feeding under constant pressure (pump 98, motor 100, pressure switch 120) is coupled by piping 126 to the hydraulic control circuit of the breaker. The piping 126 is coupled to the oil compartment 128 of accumulator 44 by a relief-drainer 130 to reduce the pressure of the hydraulic control circuit to the pressure desired in chamber 96.

Where the liquid dielectric is liquid SP its pressure can 6 be in the order of 50 kg./cm. whilst the oil pressure in the hydraulic control circuit can be 200 to 300 kg./cm.

The outlet of the relief-drainer is linked by piping 132 to tank 48. In cases of excess pressure in chamber 96 (for example as a result of an increase in temperature) the oil pushes the piston 134 of drainer 130 against the scaled spring 136, which'uncovers a draining orifice normally formed from a clapper valve 138. The oil in excess escapes through piping 132.

Activation of the coil of the interlocking electrovalve 42' is controlled by an interlocking contact 142 while activation of the coil of the breaking electro-valve 42" is controlled by an interlocking contact 146. On the valve 42" a contact 148 prevents operation of the interlocking when the valve is open. As in FIG. 6 piston 92' has a rod 118 which permits one to ascertain the volume of dielectric but this rod also acts as an automatic safety device. Should there be no dielectric in compartment 94 the end 150 of rod 118 closes a contact 152 which causes activation of the coil of a relay 154 which automatically closes the activating circuit 156 of coil 144 of the electrovalve 42". Therefore, below a certain minimal volume of dielectric in the circuit breaker there is automatic breakmg.

A switch 158 permits manual stopping of the activation of relay 154, and so cancels the order of breaking, to permit the circuit breaker to be put back into service. A general switch 160 completes the installation.

The embodiment shown in FIG. 8 is a variation de rived from the embodiments of FIG. 7 and FIGS. 1 and 2. In this embodiment the resilient pressure device for the dielectric liquid in the circuit breaker is made up of the cushion of gas 166 of the oleo-pneumatic accumulator 44, being part of the hydraulic control for the breaker. These resilient devices do not act directly on the dielectric but through the intermediary of the oil contained in the oil compartment 128, in tubing 168 and in the oil compartment 170 of a cylinder-piston system 162-164 Whose compartment 172 is in communication with the internal space 84 of the breaker by a large-section tube system 174 like the tubing 66' of FIG. 2, which permits a large flow.

The cylinder-piston system 162-164 plays the same role as the system 64-66 in FIG. 2, i.e., it maintains the pressure of the liquid dielectric and transmits to the breaking piston 18 the energy necessary for breaking. In addition, the system 162-164 plays the same role as the system 90-92 in FIG. 7, i.e., it ensures compensation for variations in volume and pressure of the dielectric.

In this embodiment the adaptation of the high pressure in accumulator 44 to the lower pressure of the liquid dielectric is effected, not by a reducer (such as reducer 130 in FIG. 7) but by providing the system 162-164 with a dilferential piston whose surfaces, turned respectively to the oil compartment 170 and the liquid dielectric compartment 172, are in the desired pressure relationship. That is why the rod 118' of piston 164 has a larger section than that of rod 118 in FIG. 7. The only other modication in respect of the hydraulic or electrical circuits shown in FIG. 7 lies in the fitting of a safety valve 176 on the oil circuit to replace the drainer 134-138 incorporated in the reducer-drainer 130 which has been removed.

Described above have been circuit breakers of the type proposed but it will be appreciated that the invention applies to all types of circuit breakers and that, in addition, the hydraulic control devices for interlocking and maintaining locking have been described only by way of example. Further, the cylinder and piston for breaking 16-18 can be situated at any point in the breaker other than the one shown as long as the piston 18 is submitted to the pressure of the liquid dielectric.

I claim:

1. A circuit breaker comprising a circuit interrupting camber containing an insulating liquid, a fixed contact and a movable contact disposed in said chamber so as to lie within said liquid for all postions of the movable contact relative to the fixed contact, a hydraulically operatedpiston means connected to the movable contact, said piston means having opposite faces, resilient means for continuously producing a pressure in the insulating liquid applied through said liquid to one face of the piston means for urging the latter in a direction corresponding to the opening stroke of the movable contact, actuating means coupled to the piston means and including a plunger connected to said other face of the piston means, a cylinder slidably supporting said piston means and a source of liquid under pressure connectable to said plunger to displace the same and the piston means therewith against the action of the resilient means, and control means for selectively connecting said plunger to said source of liquid under pressure or exhaust, said cylinder which supports the piston means separating the insulating liquid and said source of liquid under pressure.

2. A circuit breaker as claimed in claim 1 in which said insulating liquid is a liquified dielectric gas maintained permanently in the liquid state due to the pressure exerted by the resilient pressurizing means.

3. A circuit breaker as claimed in claim 2, in which the liquified gas is a gas having a high extinguishing power.

4. A circuit breaker as claimed in claim 1 in which the resilient pressurizing means for the liquid dielectric is pneumatc, comprising a cushion of gas under pressure.

5. A circuit breaker as claimed in claim 1 in which the resilient pressurizing means for the liquid dielectric is a mechanical device comprising at least one spring pushing a piston which compresses the liquid dielectric.

6. A circuit breaker as claimed in claim 4 in which the cushion of gas under pressure acts directly on the free surface of the liquid'dielectric, said cushion being contained in a fluid-tight compartment which surmounts the circuit interrupting chamber.

the cushion of gas under pressure is a gas having a pressure of liquefaction higher than that of the liquified dielectric gas filling the circuit interrupting chamber.

being in communication, directly or through the intermediary of a hydraulic fluid, with the dielectric of the circuit breaker in order to maintain it in the liquid state.

9. A circuit breaker as claimed in claim 1 in which the resilient pressurizing means for the dielectric comprises a hydraulic accumulator of the hydro-pneumatic or spring type.

10. A circuit breaker as claimed in claim 1 in which said source of liquid under pressure comprises a hydraulic accumulator, the said accumulator acting also as a resilient pressurizingdevice for the liquid dielectric.

11. A circuit breaker as claimed in claim 1 in which devices are provided to control the pressure of said insulating liquid.

12. A circuit breaker as claimed in claim 1 comprising means for control of the volume of the insulating liquid contained in the circuit breaker.

13. A circuit breaker as claimed in claim 1 in which the movable contact is hollow, the hollow part communicating on one hand with the circuit interrupting chamber and on the other with a compartment filled with liquid dielectric, as a result of which there is a circulation of dielectric through the movable contact when this is displaced, this circulation directing a flow of liquid dielectric into the zone where the arc is formed.

References Cited 7. A circuit breaker as claimed in claim 6, in which 8. A circuit breaker as claimed in claim 7 in which the cushion of gas under pressure acts on one face of a piston sliding in a cylinder, the other face of this piston UNITED STATES PATENTS 2,850,593 9/1958 Hoover et al. 3,150,245 9/ 1964 Leeds et al. 3,205,331 9/1965 Thommen et al.

' 3,259,724 7/ 1966 Aspey et al.

3,406,269 10/ 1968 Fischer.

FOREIGN PATENTS 430,968 6 1926 Germany.

ROBERTS. MACON, Primary Examiner US. Cl. X.R.