EP0515268B1 - Varistor insertion device incorporated in an H.T. circuit breaker - Google Patents

Abstract

Device for the momentary insertion, in parallel with the contacts of a circuit breaker, of an electric component, such as a varistor, connected to a contact arm carrying a contact ring, characterised in that it comprises a metal tube (32) connected mechanically and electrically to the main moving contact (9), a rod (37) being able to slide inside the said tube, the said rod comprising at a first end a metal contact sleeve (43) which can come into electrical contact with the said contact ring (31A), the said sleeve running into a stop on a first end of the said tube (32), the second end of the said tube being provided with a conical stop (38), the second end of the said tube (32) having, internally, a conical shape complementary to that of the said stop (38). <IMAGE>

Description

The present invention relates to a circuit breaker with means for the momentary insertion, in parallel on the contacts, of an electrical component.

The state of the art in this field is given by the document GB-A-2 032 180, which relates to a circuit breaker with means for momentary insertion, in parallel on the contacts of the circuit breaker, at the start of opening and at the start of the closing of the circuit breaker, of an electrical component chosen from resistors, varistors, capacitors or a combination of these elements, said circuit breaker comprising, for each phase, at least one breaking chamber comprising a sealed insulating envelope filled of gas with good dielectric properties and comprising inside a fixed arcing contact connected to a first socket, and a movable assembly comprising a movable arcing contact connected to a second socket and an operating rod, said circuit breaker further comprising inside said chamber said electrical component connected on the one hand to said first socket and on the other hand to at least one contact arm act carrying a contact ring, circuit breaker which also comprises a metallic guide element mechanically and electrically connected to said moving element, a rod which can slide inside said guide element, said rod comprising at a first end a metallic contact of the electrical component being able to come into electrical contact with said crown, a sleeve at the first end of the rod abutting on a first end of said guide element, a spring of conductive material being arranged around said rod between the first end of said guide element and the second end of said rod, said spring being relaxed when the circuit breaker is in the engaged or tripped rest position, the sleeve in this position being in abutment on the first end of said element guide and the second end of the rod being spaced from the second end of said guide member.

Such a circuit breaker has a drawback: the rapid movement of moving parts, in the absence of any damping means, can cause operating shocks.

An object of the present invention is to define a circuit breaker of the aforementioned type which, despite rapid movement of its constituent elements, has damping means making it possible to avoid suddenly and any possible rebound which could cause a reboot.

The subject of the invention is a circuit breaker with means for the momentary insertion, in parallel on the contacts of the circuit breakers, at the start of the opening and at the start of the closing of the circuit breaker, of an electrical component chosen from the resistors, varistors, capacitors or a combination of these elements, said circuit breaker comprising, for each phase, at least one breaking chamber comprising a sealed insulating envelope filled with gases with good dielectric properties and comprising inside a fixed main contact connected to a first electrical outlet and a fixed arcing contact, and a movable assembly comprising a movable main contact connected to a second electrical outlet, a movable arcing contact and an operating rod, said electrical component being placed inside of said chamber and being connected on the one hand to said first socket and on the other hand to at least one contact arm carrying a crown contact, the circuit breaker further comprising a metal tube mechanically and electrically connected to said movable main contact, a rod which can slide inside said tube, said rod comprising at a first end a metal contact sleeve which can come into electrical contact with said crown, said sleeve abutting on a first end of said tube, a spring of conductive material being disposed inside said tube and around said rod between the first end of said tube and the second end of said rod, said spring being relaxed when the circuit breaker is in the rest position engaged or tripped, characterized in that that the second end of said rod is provided with a conical stop carrying an O-ring made of polytetrafluoroethylene, the second end of said tube having internally a conical shape complementary to that of said stop.

Advantageously, the end of the contact sleeve is made of a metallic material impregnated with a product which releases, under the effect of the electric arc, a dielectric gas.

In a particular embodiment, the contact arm is produced in the form of a tube provided at one end with contact fingers and with a partition to delimit a blowing volume, an insulating nozzle surrounding the contact fingers.

Alternatively, the insulating nozzle with the tube forms a blowing volume, the partition being removed.

For the insertion of a varistor, the distance corresponding to the length of the displacement of the tube before driving the rod is determined to obtain an insertion time of the varistor at the opening of the order of 8 milliseconds.

• la figure 1 est une vue partielle en coupe axiale d'une chambre de coupure avec varistance à l'intérieur de ladite chambre et dispositif d'insertion de cette varistance, selon un premier mode de réalisation de l'invention,
• les figure 2A et 2B sont des vues agrandies en coupe axiale du dispositif d'insertion, dans des positions correspondant respectivement à l'état fermé du disjoncteur et en cours de manoeuvre d'ouverture,
• la figure 3 est une vue en coupe axiale d'un dispositif d'insertion selon une variante de réalisation de l'invention.

The invention is clarified by the description of several embodiments of the invention, with reference to the appended drawing in which:

• FIG. 1 is a partial view in axial section of a breaking chamber with varistor inside said chamber and device for inserting this varistor, according to a first embodiment of the invention,
• FIGS. 2A and 2B are enlarged views in axial section of the insertion device, in positions corresponding respectively to the closed state of the circuit breaker and during the opening operation,
• Figure 3 is an axial sectional view of an insertion device according to an alternative embodiment of the invention.

In FIG. 1, the reference 1 designates an insulating envelope, preferably made of porcelain, delimiting a volume 2 containing the breaking elements of the circuit breaker. The insulating envelope is closed at one end by a metal plate 3, fixed to a metal crown 4 constituting a first and prolonged socket, inside the envelope by arms 5 to which are fixed a first metal tube 6 constituting the main fixed contact, and a second tube 7, coaxial with the first, constituting the fixed arcing contact.

Volume 2 is filled with a gas with good dielectric properties, such as sulfur hexafluoride, under a pressure of a few bars.

The mobile assembly of the circuit breaker comprises a metal tube 9, extended by a corona hood 10, and provided with a transverse metal partition 11 carrying contact fingers 12 constituting the movable main contact, and a blowing tube 13 extended by contact fingers 14 constituting the movable arcing contact. The partition 11, pierced with holes 15 for the passage of the blowing gas, carries a blowing nozzle 17 made of insulating material. The blowing is provided by a fixed piston placed inside the tube 9, and not shown in FIG. 1. The tube 9 is connected, by sliding contacts, not shown, to a second outlet of the circuit breaker.

A varistor is placed inside the volume 2. This consists of a stack of discs 18 placed in an insulating tube 19, fixed at one end to the plate 3 and closed at the other end by a metal block 20 .

As a variant, the varistor can be associated with several ohmic elements (resistance); the invention also applies to circuit breakers in which there are only ohmic elements. In the following, for the sake of simplification, we will only mention the presence inside the breaking chamber of a varistor, but it should be understood that the invention applies to any circuit breaker in which an electrical component ( varistor, resistor, capacitor, or any combination of these) must be inserted either when the circuit breaker opens, when it closes, or during these two operations.

The insertion device of the invention is generally represented at 30 in FIG. 1. It cooperates with a contact consisting of arms 31, fixed to the metal block 20 and carrying a metal crown 31A ..

A detailed example of an embodiment of the insertion device is shown in FIGS. 2A and 2B.

The insertion device comprises a metal tube 32, having a projection 32A by which the tube is mechanically fixed and electrically connected to the tube 9, for example by brazing. Inside the tube is disposed a sleeve 33, for example made of Teflon. The sleeve 33 and the tube 32 define a housing in which is housed a first end of a spring 34 which bears against a shoulder 32B formed inside the tube 32. The sleeve 33 is screwed onto the shoulder 32B. An insulating washer 35 is glued to the upper end of the tube 32. The lower end of the tube 32 has an internal profile of conical shape, the role of which will be explained below.

Inside the sleeve 33 can slide a rod 37, for example of high resistance brass, terminated by a portion 37 A of larger diameter pierced with a threaded bore 37B. Towards the lower end of the portion 37A, a shoulder 37C serves as a support for the second end of the spring 34. On the lower end of the portion 37A is engaged a stop or ring 38, with conical external profile, preferably made made of polytetrafluoroethylene, and provided with an O-ring 39. The ring 38 is held in place by the head of a bolt 40, screwed into the bore 37B with interposition of rings 41 and 42.

At the upper part of the rod 37 is screwed a contact sleeve 43, advantageously made of copper.

• lorsque le disjoncteur est en position fermée (figures 1 et 2A), le manchon de contact 43 est en contact avec la couronne 31A et la varistance est court-circuitée par les contacts principaux et les contacts d'arc. Le ressort 34 est détendu.
• à l'ouverture du disjoncteur, l'équipage mobile est entraîné vers le bas de la figure, entraînant le tube 32 qui comprime le ressort 34; en raison de l'inertie de la tige 37 et du manchon de contact 43, ceux-ci restent immobiles, de telle sorte que la varistance est insérée dans le circuit du disjoncteur après la séparation des contacts d'arc 7 et 14. Le courant passe alors par les bras de contact 31, la couronne 31A, le manchon de contact 43, la tige 37, le ressort 34 le tube 32 et le tube 9. Le ressort est avantageusement réalisé en cuivre au beryllium.

The operation of the device is as follows:

• when the circuit breaker is in the closed position (FIGS. 1 and 2A), the contact sleeve 43 is in contact with the ring 31A and the varistor is short-circuited by the main contacts and the arcing contacts. The spring 34 is relaxed.
• when the circuit breaker opens, the moving element is driven downwards in the figure, driving the tube 32 which compresses the spring 34; due to the inertia of the rod 37 and of the contact sleeve 43, these remain stationary, so that the varistor is inserted into the circuit breaker after the separation of the arcing contacts 7 and 14. The current then passes through the contact arms 31, the crown 31A, the contact sleeve 43, the rod 37, the spring 34 the tube 32 and the tube 9. The spring is advantageously made of beryllium copper.

When the spring reaches the end of compression (position of FIG. 2B), the rod 37 is driven, which produces the separation of the contact sleeve 43 and the crown 31A and, consequently, the disinsertion of the varistor.

When the moving part of the circuit breaker has come to a standstill, the rebound of the spring returns the rod 37 to its initial position relative to the tube 32.

Thanks to the conical part of the tube 32, which cooperates with the conical ring 38, these two elements having complementary conjugate shapes the drive of the rod is done smoothly.

• d'une part, la longueur d1 correspondant à la longueur du déplacement du tube 32 avant entraînement de la tige 37 (figure 2B),
• d'autre part, la distance a entre la couronne 31A et l'extrémité du tube 7 (figure 1). Plus la distance a est faible, plus il faut allonger la distance d1.

It is possible to size the device so as to adjust the insertion time of the varistor at the opening of the circuit breaker; for this, we have two parameters:

• on the one hand, the length d1 corresponding to the length of the displacement of the tube 32 before driving the rod 37 (FIG. 2B),
• on the other hand, the distance a between the ring 31A and the end of the tube 7 (Figure 1). The smaller the distance a, the longer the distance d1 must be extended.

The device also allows the varistor to be inserted when the circuit breaker closes. It is enough for this that the end of the sleeve 43 comes into contact with the crown 31A before the arcing contacts 7 and 14 come into contact. The distance a determines the insertion time at closing, the duration of which is usually of the order of 8 ms. If, at rest, the end of the movable arcing contact 14 and the end 43A of the contact sleeve 43 are at the same level, and if the distance a is zero, there can be no insertion of the varistor when closing of the circuit breaker.

On separation of the contact sleeve 43 and the contact ring 31A, an arc is produced; it will be more easily extinguished if the end 43A of the contact sleeve 43 is made of a metallic material impregnated with a product which releases, under the action of the arc, gas, such as fluorine. Mention may be made, for example, of a product based on metal powder impregnated with a polymer, known under the trademark FULMEX.

FIG. 3 represents an alternative embodiment of the device, which can advantageously be used for circuit-breakers with a metal grounded enclosure, in which there is a relatively large space around the breaking elements. In this embodiment, where the elements common to the preceding figures and to FIG. 3 have been given the same reference numbers, the contact arms 31 are replaced by a tube 50 terminated by contact fingers 51. The tube has a bottom 53, so that its internal volume 56 constitutes a blowing volume of the arc which is established at the separation of the fingers 51 and of the contact 43A. A nozzle 54, made of an insulating material such as polytetrafluoroethylene, promotes this blowing.

The tube 32 of the device is fixed to the mobile tube by an arm 55. In this embodiment, where distance a is equal to zero, there is no insertion of a varistor when the circuit breaker closes.

We can also remove the bottom 53 and use the volume 57 as the volume of thermal expansion and blowing. In this case, a double blowing of the arc is carried out with an upward gas flow through the tube 50 and a downward gas flow through the neck of the nozzle 54.

The invention applies to high-voltage circuit breakers of the conventional type with a ceramic shell or of the type with a metal shell on the ground.

Claims (5)

1. Circuit-breaker with means for temporarily inserting an electrical component (18) selected from a resistor, a varistor, a capacitor and any combination of said components in parallel with the contacts of a circuit-breaker at the start of opening or at the start of closing of said circuit-breaker, said circuit-breaker comprising, for each phase, at least one interrupting chamber comprising a gas-tight insulative casing (1) filled with a gas having good insulative properties and comprising inside it a fixed main contact (6) connected to a first terminal (4) and a fixed arc contact (7) and a mobile assembly comprising a mobile main contact (9) connected to a second terminal, a mobile arc contact (14) and an operating link, said electrical component (18) being disposed inside said chamber and connected firstly to said first terminal (4) and secondly to at least one contact arm (31) carrying a contact ring (31A), the circuit-breaker further comprising a metal tube (32) mechanically joined and electrically connected to said main mobile contact (9), and a rod (37) adapted to slide inside said tube and comprising at a first end a metal contact tube (43) adapted to come into electrical contact with said ring (31A), said sleeve abutting a first end of said tube, a conductive material spring (34) being disposed inside said tube (32) and around said rod (37) between the first end of said tube (32) and the second end of said rod (37), said spring being relaxed when said circuit-breaker is in an armed or tripped rest position, characterised in that the second end of said rod is provided with a conical abutment (38) carrying a polytetrafluoroethylene O-ring (39), the second end of said tube (32) having inside it a conical shape complementary to that of said abutment (38).
2. Circuit-breaker according to claim 1 characterised in that the end (43A) of said contact sleeve is made from a metal impregnated with a product adapted to release an insulative gas due to the effect of the electrical arc.
3. Circuit-breaker according to claim 1 or claim 2 characterised in that the contact arm is in the form of a tube (50) provided at one end with contact fingers (51) and with a bulkhead (53) for delimiting a gas blast volume, an insulative nozzle (54) surrounding the contact fingers.
4. Circuit-breaker according to claim 3 characterised in that the insulative nozzle (54) forms with the tube (50) a gas blast volume (57), said bulkhead (53) being dispensed with.
5. Circuit-breaker according to any one of claims 1 to 4 characterised in that the distance (d1) over which the tube (32) is displaced before it entrains the rod (37) is determined in such a way as to achieve a varistor insertion time on opening in the order of eight milliseconds.

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