US2901570A

US2901570A - Hydraulically actuated electric circuit-breakers

Info

Publication number: US2901570A
Application number: US649327A
Authority: US
Inventors: Gratzmuller Jean Louis
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-04-04
Filing date: 1957-03-29
Publication date: 1959-08-25
Anticipated expiration: 1976-08-25
Also published as: GB817619A; FR1147257A

Description

Aug. 25, 1959 2,901,570

HYDRAULICALLY ACTUATED ELECTRIC CIRCUIT-BREAKERS J. L. GRATZMULLER 3 Sheets-Sheet 1 Filed March 29 7 T lzwazz for Graizanw Zer Aug. 25, 1959 J. L. GRATZMULLER 2,901,570

HYDRAULICALLY ACTUATED ELECTRIC CIRCUIT-BREAKERS Film Aug. 25, 1959 .1. 1.. GRATZMULLER 2,901,570

HYDRAULICALLY ACTUATED ELECTRIC CIRCUIT-BREAKERS Filed March 29, 1957 3 Sheets-Sheet s 3 Q Q 53 V///Z V////////////////// ///AZ Z//// //////J United States Patent HYDRAULICALLY ACTUATED ELECTRIC CIRCUIT-BREAKERS Jean Louis Gratzmuller, Paris, France Application March 29, 1957, Serial No. 649,327

Claims priority, application France April 4, 1956 2 Claims. (Q1. 20082) This invention relates to hydraulically actuated electric circuit-breaker assemblies of the kind having oil-immersed fixed contacts connectible by an axially movable contact rod directly actuated by a single-acting hydraulic actuator with spring return, which is incorporated with the circuit-breaker itself in a unitary structure and is always live, the actuator being connected to a control station at earth potential by combined feed and exhaust-ducting made of insulating material, and the hydraulic liquid being, as is usual, an insulator.

The invention is especially, though not exclusively, applicable to hydraulically actuated circuit-breaker installations of the suspended type.

The main object of the invention is to make the complete installation more compact than present installations,

primarily by enabling a shorter length of insulating feed and exhaust ducting to be used, and secondarily by shortening the overall length of the combined circuitbreaker and actuator assembly.

Installations of this kind as hitherto designed and using a linear actuator, i.e. a simple hydraulic jack, have called for a separation between the fixed contact, at which the circuit is made and broken, and the earthed control station of more than five times the separation of the fixed contacts, which for high voltages may be of the order of one to three feet. This factor, of arises from the following considerations. Since the separation of live members from one another or from earth required to guard against flash-over in air is about twice the corresponding separation in oil, the length of the insulating feed and exhaust ducting must be at least twice the separation of the fixed contacts; and since the jack stroke must be substantially equal to the separation of the fixed contacts and the length of the jack assembly must, allowing for constructional necessities, be more than twice the jack stroke, the combined length of the circuit-breaker itself, the jack assembly and the insulating ducting must amount to more than (1-|2+2=5) X the contact separation.

The present invention makes use, as its primary feature, of the principle of immersing the insulating ducting and part at least of the actuator assembly in a column of insulating oil enclosed in a tubular insulator, thus enabling the length of the ducting to be reduced by about half.

A secondary, optional feature of the invention, applicable to the case in which the circuit-breaker is connected across a pair of bare conductors, is based on the fact that the separation in air of such conductors must be about twice the separation in oil of the fixed contacts. This feature consists essentially in extending the actuator assembly into the contact-breaker chamber which is enclosed by an insulating casing and contains the oil in which the fixed contacts are immersed.

The term oil as used herein (including the claims hereof) is to be understood to mean any suitable electrically insulating and hydraulic liquid.

. .In a preferred form of construction, the actuator is a Patented Aug. 25, 1959 single-acting hydraulic jack of which the movable element carrying the contact rod is the cylinder, the piston being fixed and hollow and forming a continuation of a single insulating feed and exhaust duct, the contact-making stroke being effected by admitting oil under pressure into the jack and the return stroke, by which contact is broken, being effected, on release of pressure in the feed and exhaust duct, by a spring.

Preferably also, the jack cylinder is nested within the return spring, thus promoting compactness of the structure.

An embodiment of the invention, with certain preferred constructional details and modifications, is illustrated by way of example only, in the accompanying drawings, of which:

Figure 1 is a somewhat schematic, vertical section, partly in elevation, of a combined circuit-breaker and hydraulic actuator;

Figures 2 and 3 show two portions of the assembly shown in Figure 1, on an enlarged scale and including more detail;

Figure 4 corresponds to a part of Figure 2, on a still larger scale and illustrates preferred constructional details and modifications;

Figure 5 is a large scale view in vertical sect-ion of part of the assembly illustrating further preferred constructional details; and

Figure 6 is a large scale sectional view of a device for rapidly exhausting the hydraulic actuator, illustrating preferred constructional details.

The assembly shown in Figure 1 comprises two outer tubular insulators 1 and 2 disposed vertically one above the other. Insulator 1 encloses the circuit-breaker elements and insulator 2 encloses the hydraulic actuator and its feed and exhaust duct 13, S1. The tubular insulator 1 is closed at the top by a metal cover plate 4, to which is connected one of the line wires 3, the other line wire 6 being connected to the basal flange 7 of a metal bell 8, flange 7 being sandwiched between the lower end of insulator 1 and the upper end of insulator 2. Plate 4 carries on its inner face a resilient, tulip type, fixed contact 5 and the bell 8 carries a resilient, tulip type, fixed contact 9 through which passes, in sliding contact, an axially movable contact rod 11, which is guided in the top part of the bell 8. In the position shown in Figure 1 rod 11 makes good contact with contact 5 and thus establishes electrical connection between line wires 3 and 6 through flange 7, bell 8, contacts 9, 5 and plate 4.

The actuator of the circuit-breaker is constituted by a single-acting hydraulic jack with spring return, comprising a movable cylinder 12 rigidly and directly connected to the contact rod 11, a fixed hollow piston 13 whose interior communicates with the inside of cylinder 12 and with the upper end of a combined feed and exhaust duct 51 made of insulating material, and a helical return spring 14, coiled round the outside of cylinder 12 and acting in compression between the inner face of the hell 8 and the upper face of a flange 15 on the lower end of cylinder 12. The return spring 14 effects the contact-opening stroke of the jack which is limited by a metal collar 16 fixed on the lower end of piston 13 and receiving the upper end of the insulating duct 51. The contact-closing stroke of the jack, effected by hydraulic pressure, is limited by engagement of the top of the cylinder 12 with the inner face of the bell 8.

The lower end of insulator 2 is closed by a container 18 enclosing an automatic device hereinafter described, which operates to direct pressure liquid supplied through a feed pipe 17 into the interior of duct 51 and to exhaust liquid from duct 51 into the container 18, which constitutes an intermediate receiver for exhausted liquid, the

3 latter being ultimately returned to a sump (not illustrated) through a drain 19 (Figure 3).

Both the interior of the tubular insulator 1 and the interior of the tubular insulator 2, including the interior of bell 8, are filled with an insulating oil.

The operation of this assembly is as follows:

When the feed pipe 17 is under pressure, the automatic device in container 18 closes the connection to exhaust of duct 51 and allows liquid under pressure to enter duct 51 and :raise the cylinder 12. into contact-making position as seen in Figure 1; and as long as pipe 17 is under pressure this pressure is transmitted to the jack and keeps cylinder 12 in the raised position. As soon as the pressure in pipe 17 is relieved the automatic device allows the liquid in the jack to be rapidly exhausted through duct 51 into the intermediate-receiver 18, and the spring 14 effects a rapid return of cylinder 12 to its lowest position, thus causing a quick contact-break.

This assembly is characterized by certain dimensional features. It is to be assumed that the separation of two live conductors or of a live conductor from earth required to avoid all possibility of flashover is, in air 2L, and in oil L. The length of the insulator 1, which is dictated by the separation of the line wires 3, 6, is therefore 2L, while the separation of contacts 5, 9, which are oilimmersed is L. This separation dictates the stroke of the jack, which is likewise L. Since the cylinder 12 is alive and is electrically connected by means of piston 13 with collar 16, the latter will also be alive; it must therefore be separated from the top of container 18 by a distance L. The distance between collar 16 and the inner face of the top of hell 8 must be at least twice the stroke of the jack plus the length of engagement of the piston 13 in the cylinder 12 when the latter is at its uppermost position, this length being denoted d; and taking into account the thickness e of the collar 16 the total separation of the inside of the top of bell 8 from the top of container 18 is therefore 3L+d+e. Now if the insulating duct 51 lying below the collar 16 were not oil-immersed but was in air it would have to be twice as long; and the saving in bulk thus effected by the oilimmersion will be evident. A further saving in bulk is effected by extending the bell 8 up into the tubular insulator 1 as shown. Thus, if of constructional necessity the top part of bell 8 and the contact 9 occupy a length c as shown, the total distance between flange 7 and container 18 can be reduced to 3L+c+d+eL, i.e.

2L+c+d+e i.e., it need only exceed 2L by a small amount arising from constructional considerations.

Figures 2 and 3 illustrate certain constructional details, of which one is the enclosure of the whole jack system from the top of bell 8 down to the collar 16 in a tubular metal sheath 35, which is introduced for reasons of ease of assembly and also serves as a guide for spring 14. Another such detail is the venting of the top of the contact breaker chamber enclosed by the tubular insulator 1, to allow for expansion of the oil contents thereof, by means of openings 21 in the cover plate 4, protected against ingress of foreign bodies by a cap 22 having a depending flange which overlaps an upstanding flange 25 on the cover 4.

In the arrangement shown in Figures 1 to 3, the tubular insulator 2 extends from flange 7 to container 18 and its length is therefore 2L+c+d+e. This is greater than is necessary since the required length for avoiding flashover in air is only 2L. In order, therefore, to provide greater mechanical strength and to economise in expensive insulating material, the effective length of insulator 2 can be reduced to 2L, as shown in Figure 4 by interposing between the top of insulator 2 and the flange 7 a metal tubular member 81 welded to upper and lower collars 82, '84 respectively, collar 82 being secured by screws 83 to a flange 31, which is in turn secured by screws 29 to flange 7, to which is also secured by screws 27 a flanged ferrule 26 screwed on to the lower end of insulator 1, while collar 84 is similarly secured by screws to a flange having a depending collar to which the upper end of insulator 2 is secured by a flanged ferrule and a ring nut. Sealing rings, such as 28, 32 are provided for sealing all the joints of this structure.

The annular space between the outer tube, constituted by the member 81 and the insulator 2, and the tubular sheath 35 is vented to the interior of sheath 35 by openings 87, 88 (and 89see Figure 5) in the latter.

Flange 31 is formed integrally with a member 30, the whole being of top-hat form, the crown of this member constituting the upper abutment for spring 14 and the upper stop for cylinder 12; the cylindrical sleeve portion of member 30 constitutes a continuation of sheath 35, which is welded to flange 31.

Vents 91 in the sleeve portion and crown of member 30 provide communication between the oil space surrounding the jack assembly and the space enclosed between the member 30 and the bell 8, the latter being vented at 86 to the circuit breaker chamber enclosed by insulator 1. Thus, the

events

87, 88, 89, 91 and 86 provide intercom munication between the lower chamber enclosed by insulator 2 and the upper chamber enclosed by insulator 1, so that no separate venting to atmosphere of the lower of these chambers is required to accommodate expansion.

The upper end of cylinder 12 is formed by a separate screwed-on head 33, between which and the end of the cylinder 12 itself is trapped the head of a stud 34 which is screwed into the lower end of the contact rod 11, the latter being of tubular form. The tulip contact 9 is screwed on to an upward extension of bell 8 which guides the rod 9.

Figure 5 illustrates preferred constructional details of the lower end of the jack assembly and its connection to the collar 16 and insulating duct 51.

The lower end of sheath 35 is secured to collar '16 by a circlip 37.

The lower end of piston 13 is secured to collar 16 by a nut 43, spacer ring and circlip 92.

On the lower end of cylinder 12 is screwed a ferrule 38 of special form whose upper end is counter-bored to receive sealing rings 39, axially compressed by means of a spacer ring 41 located on the cylinder 12 by a circlip 42. There is a clearance between the piston 13 and cylinder 12, the latter being guided on the piston by means of a sleeve 44 lodged in the bore of ferrule 38 and lubricated by oil derived from the interior of insulator 2 through holes 45 drilled in the ferrule 38 and sleeve 44. The cylinder piston seal is provided by a sealing ring 46 located on the upper end of sleeve 44 and compressed by a loose flanged collar 47 backed by a spring 48, which is precompressed by the lower end of cylinder 12.

The flange 15 forming the lower abutment of spring 14 is formed integrally on ferrule 38. The upper end of the insulating duct 51 is secured to the collar 16 by a flanged ferrule 52 screwed on to the duct 51 and a nut 53 screwed into the collar 16 to locate the flange of ferrule 52 against a shoulder in collar 16. This connection is scaled by sealing rings 94, 96.

Figure 6 illustrates the automatic valve device for the admission and rapid exhaustion of oil to and from the jack cylinder 12, via the hollow piston 13 and insulating duct 51, as well as preferred constructional details of the attachment of this device and the container 18 to the lower ends of the tubular insulator 2 and the insulating duct 51. The lower end of duct 51 is secured to a tubular body 57 by means of a flanged ferrule 55 screwed on to the duct 51, a ring nut 56 screwed into the body 57 and a distance piece lodged between the flange of ferrule 55 and a shoulder in the bore of body 57. The latter is secured by means of a circlip and ring washer in the central opening of a recessed disc 58 to which is secured by studs 59 a flanged ferrule 61 screwed on to the lower end of the tubular insulator 2. The body 57 extends through the base of the container 18, which is clamped against the underside of disc 58 by a nut 63 screwed on to the body 57. The bottom of body 57 is closed by a screwed plug 67 into which the feed pipe 17 is screwed.

The bore of body 57 is interrupted by a partition 98 formed integrally with the body and dividing the interior of the body into an upper chamber communicating with the duct 51 and a lower chamber in which a plunger 64 is vertically slidable. Partition 98 is pierced by a passage 100 affording communication between the upper and lower chambers. The upper part of plunger 64 constitutes a valve needle which seats on the edge of a blind bore 73 in the partition 98 which communicates with the interior of container 18 through a lateral port into which is screwed a calibrated nipple 74. The plunger 64 is axially bored and screw-threaded to receive a screwed plug 65 having a blind axial passage 69 whose upper margin forms the seating for a ball 71. Oblique drillings 72 connect the space above ball 71 with the lower chamber of the body 57 below partition 98. Radial drillings 68 in plug 65 provide communication between the lower end of passage 69 and a recess in plug 67 communicating with the feed pipe 17. In this recess is lodged a spring 66 which presses on the underside of plug 65 and urges it and plunger 64 upwards and normally holds the needle part of the plunger on its seating.

Between the outlet of nipple 74 and the general interior of the container 18 is a labyrinth composed of a cylindrical wall 75 formed integrally with the container and surrounding, but spaced from, the body 57, and a sleeve 76 surrounding, but spaced from, the wall 75, and clamped between the base of container 18 and the underside of disc 58. Wall 75 extends nearly to the underside disc 58 and sleeve 76 has openings 77 at the bottom. The drain 19 communicates with a vertical gallery 102 formed in the wall of the container 18 and opening into the container about half way up it. Another vertical gallery 104 in the container wall opens into the container near the top of it and communicates with an atmospheric vent 78. All the joints in this structure which are subjected during operation to pressure differences or require protection against leakage are provided with sealing rings, such as 62.

The operation of this automatic feed and rapid exhaust device is as follows:

When pipe 17 is under pressure, the pressure is transmitted through drillings 68 and passage 69 to unseat ball 71, at the same time acting on the base of plug 65 and plunger 64 to assist spring 66 in holding the needle of plunger 64 on its seating and thus keeping the exhaust passage 73, 74 closed. Lifting of ball 71 allows the liquid under pressure to pass from the feed pipe 17 through the drillings 72 and passage 100- into the insulated duct 51 and thence into the jack cylinder 12, thus raising the latter and performing the contact-making stroke. When the pressure in pipe 17 falls abruptly, either by design or inadvertently, the pressure above the ball 71 causes it to seat immediately, thus sealing off the feed pipe 17, and acting on the top face of plunger 64 drives the latter downwards, unseating the plunger-needle and allowing the liquid to escape from the jack cylinder through duct 51, passage 100, bore 73 and nipple 74 into the container, the liquid being rapidly expelled by the now unopposed effort of spring 14 in effecting the contactbreaking stroke of the jack. The labyrinth 75, 76, 77 prevents splashing and undue agitation of the liquid in the container, from which it cannot escape into drain 19 until the container is half full. Displaced air is expelled through vent 78.

It has been found that the disposition of the container or intermediate receiver 18 at the bottom of the long vertical, tubular assembly comprised by the jack cylinder 12, hollow piston 13 and insulating duct 51 has the unexpected beneficial result of effecting through de-aeration of the liquid expelled from the jack at each contact-breaking operation, such tie-aeration being brought about by the high velocity with which the liquid column is ejected.

What is claimed is:

1. In an electric circuit breaker for making and breaking a circuit between a pair of conductor terminals, a tubular insulator extending from one of the terminals to the other of the terminals, with the insulator defining an oil filled chamber, a fixed contact located at the upper end of the chamber and operatively connected to one of the terminals, an electric conducting bell-shaped element defined by an end portion, a tubular sleeve portion and a flange portion with the end portion and sleeve portion being located within the lower portion of the chamber, and the other terminal being connected to the flange portion, a second fixed contact carried by said end portion, the said tubular sleeve portion and second fixed contact having an over-all length such as to extend within the chamber to a point substantially midway of the conductor terminals, a movable conductor rod passing through an aperture formed in said end portion and making a sliding contact with said second contact member, the upper end of the rod serving to engage the first-named contact to close the circuit through approximately onehalf the length of the chamber, actuator means connected to the lower end of the rod to move the rod longitudinally between circuit making and circuit breaking positions, the actuator means including a second tubular insulator connected to the flange portion of the bell-shaped element in co-axial relationship with the first-named tubular insulator and forming a second oil filled chamber, a grounded base member closing the lower end of the second tubular member, a single-acting cylinder-piston means of electric conducting material positioned partly within the bellshaped element and partly within the upper end of the second named chamber, the movable component of the cylinder-piston means being connected to the lower end of the rod, compression spring means surrounding the movable part, with one end thereof bearing against the bell-shaped element and the other end bearing against abutment means on the movable part to urge the movable part and the rod to circuit breaking position, and a feed and exhaust pipe of insulating material located within the second chamber serving to establish communication between the base member and the movable part of the cylinder-piston means, the length of the pipe being substantially equal to the distance between the fixed contacts whereby oil under pressure conducted through the base member and the pipe to the movable part will cause the movable part to move the rod against the action of the spring means into circuit making position.

2. In an electric circuit breaker for making and breaking a circuit between a pair of conductors, a tubular insulator extending from one of the conductors to the other of the conductors, with the insulator defining an oil filled chamber, a fixed contact located at the upper end of the chamber and opcratively connected to one of the conductors, an electric conducting bell-shaped element defined by an end portion, a tubular sleeve portion and a flange portion with the end portion and sleeve portion being located within the lower portion of the chamher and the other conductor being connected to the flange portion, a second fixed contact carried by said end portion, the tubular sleeve and second fixed contact having an overall length such as to extend within the chamber to a point substantially mid-way of the conductors, a movable conductor rod passing through an aperture formed in said end portion with the rod making a sliding contact with the second contact, the upper end of the rod serving to engage the first named contact to close the circuit through approximately one-half the length of the chamber, actuator means connected to the lower end of the rod to move the rod longitudinally between 7 circuit making and circuit breaking positions, the actuator means including a second tubular insulator connected to the flange portion of the bell-shaped element in co-axial relationship with the first named tubular insulator and forming a second oil filled chamber, a grounded base member closing the lower end of the second named chamber, a single-acting cylinder-piston means of electric conducting material positioned partly within the bellshaped element and partly within the upper end of the second named chamber, said piston being immovable relative to the bell-shaped element and the second chamher and the cylinder being movable longitudinally on the piston relative to the bell-shaped element and the second chamber, the cylinder :being connected to .the lower end of the rod, abutment means on the lower end of the cylinder, compression spring means surrounding the cylinder with one end of the spring means bearing against the bell-shaped element and the other end hearing against the abutment means on the cylinder to urge the cylinder and the rod to circuit breaking position, and

a feed and exhaust pipe of insulating material located within the second chamber serving to establish communioation between the base member and the cylinder, the length of the pipe being substantially equal to the distance between the fixed cont-acts whereby oil under pressure conducted through the base member and the pipe to the cylinder will cause the cylinder to move the rod against the action of the spring means into circuit making position.

References Cited in the file of this patent UNITED STATES PATENTS 735,452 Bliss Aug. 4, 1903 2,239,554 Dufling Apr. 22, 1941 2,249,006 Kesserling et al July 15, 1941 2,477,837 Strom Aug. 2, 1949 2,611,846 Applegate Sept. 23, 1952 2,668,217 Vogelsanger et 'al. Feb. 2, 1954 2,813,177 Eberhard Nov. 12, 1957