EP2795648B1 - Device for protection against particles generated by an electric switching arc - Google Patents

Description

TECHNICAL AREA

The invention relates to a device for protection against particles generated by a switching electric arc. Such a device is particularly suitable for high voltage (HV) and medium voltage (MV) electrical equipment, including HV circuit breakers, MV circuit breakers and generator circuit breakers.

STATE OF THE PRIOR ART

In the majority of circuit breakers, there is a main electrical circuit for the passage of electric current when the circuit breaker is in the closed position and a secondary electrical circuit for the function of breaking the current when it is desired to place the circuit breaker in the open position.

The figure 1 is a longitudinal sectional view of a circuit breaker disclosed in the document EP-A-0 982 748 (corresponding to the patent US 6 211478 ) and showing a main electrical circuit and a secondary electrical circuit. In this figure, there is a casing 1 circuit breaker having a longitudinal axis 2, consisting of a metal upper portion 3, a lower metal portion 4 and a central portion 5 of electrically insulating material connecting the parts 3 and 4 .

The main electrical circuit comprises the upper and lower metal portions 3 and 4 and intermediate metal elements: the contact 6 fixed to the upper part 3, the contact 7 integral with the lower part 4 and the movable contact 8 consisting of a succession of fingers and which can be moved to connect the fixed contacts 6 and 7 (as shown in the figure to the left of the axis 2) or not to ensure the connection between the fixed contacts 6 and 7 (as shown in the figure to the right of the axis 2).

The secondary electric circuit comprises a contact pin 14 able to be moved from a high position (see the left-hand part of the figure) to a low position (see the right-hand part of the figure) by means of a ordered. The contact pin 14 slides along the longitudinal axis 2 while being guided by a slideway 13. In the up position, the contact pin 14 is in electrical connection with the upper part 3 of the housing via the horizontal partition 9 of FIG. the part 3 equipped in the center of the tulip contact 11. In the low position, the contact pin 14 is no longer in electrical connection with the upper part 3 of the housing 1.

The figure 1 also shows an arrangement 10 for the switching arc whose volume 18 is limited by the partition 9, the tulip contact 11, the circular wall 20 of eclectically insulating material, the partition 15 secured to the part 4 and equipped in its center of the nozzle 12.

The figure 1 still shows an arc chamber 16, an electric arc 17, a circular blast slot 19, blast cylinders 21, blast pistons 22, blast channels 23 and check valves 24.

During the opening operation of the circuit breaker, the main contacts (the movable contact 8 and the fixed contacts 6 and 7) separate first and the electric current that passed through these contacts switches on the secondary circuit. This switching gives rise to an arc between the fixed contacts and the moving contact. This arc rejects sparks that disturb the dielectric strength of the equipment. To overcome this drawback, the document EP-A-0 982 748 advocates the use of materials resistant to electrical erosion. However, if the amount of sparks then emitted is lower, it is still critical for the dielectric strength of the equipment.

The document US3984651 describes a device according to the preamble of claim 1.

STATEMENT OF THE INVENTION

The object of the present invention is to provide a protection device for limiting the impact of the electric arc phenomenon, so as to increase the dielectric withstand / output of the device, equipped with this protection device transient as steady state.

A first object of the invention consists of a protection device against particles generated by an electric arc when a first electrically conductive part and a second electrically conductive part of an electrical connection assembly are separated from each other, the first electrically conductive part and the second electrically conductive part each having a cylindrical contact surface and the separation of the first and second parts by relative sliding of one of the contact surfaces on the other surface of the contact, the protection device comprising a protection element disposed near the location of the separation of the first part and the second part and facing one of the contact faces to screen said particles, the element of protection being of cylindrical shape and located outside the cylindrical shapes of the first t of the second piece, characterized in that the device comprises another cylindrical protective element located inside the cylindrical shapes of the first and second part.

The protective element or the other protective element can then be metallic or metallized.

The protective element or the other protective element may be of electrically insulating material.

The protective device may comprise an additional ring-shaped or ring-shaped protective element, located within the cylindrical shapes of the first and second parts, substantially perpendicular to a direction of sliding of the surfaces of the contact between them and facing a contact surface discovered by the sliding of the contact surfaces between them. This additional protection element may be of electrically insulating material.

A second object of the invention consists of a circuit breaker comprising a main electrical circuit for the passage of electric current when the circuit breaker is in the closed position and a secondary electrical circuit intended for the function of breaking the current to place the circuit breaker in the open position, the circuit main electrical system comprising an electrical connection assembly equipped with a protection device against particles generated by an electric arc as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue en coupe longitudinale d'un disjoncteur selon l'art connu,
• la figure 2 est un schéma explicatif du fonctionnement du dispositif de protection contre les particules engendrées par un arc électrique de commutation selon l'invention.

The invention will be better understood and other advantages and particularities will appear on reading the following description, given by way of non-limiting example, accompanied by the appended figures among which:

• the figure 1 is a longitudinal sectional view of a circuit breaker according to the prior art,
• the figure 2 is an explanatory diagram of the operation of the protection device against particles generated by a switching electric arc according to the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The invention finds a particularly interesting application in the field of circuit breakers which have a main circuit for the passage of the permanent current and a secondary circuit for the power failure. In this case, the invention makes it possible to deal with the problem of switching between the main circuit and the secondary circuit.

The figure 2 is an explanatory diagram of the operation of the protection device against particles generated by a switching electric arc according to the invention.

In this figure, there are shown two elementary parts forming part of an electrical connection assembly: a first electrically conductive part 31 (in general, it is a contact finger) and a second electrically conductive part 32. parts 31 and 32 can be made totally or partially or not at all with materials particularly resistant to electrical erosion. On the figure 2 the ends 33 and 34 of the parts 31 and 32 intended to be brought into contact are provided with a material particularly resistant to electrical erosion.

In the case of a circuit breaker having a main electrical circuit and a secondary electrical circuit, the opening of the main circuit is achieved by the relative movement of the part 32. During the separation of the parts 31 and 32, a switching arc s establishes as indicated on the figure 2 where the separation is shown by the arrow to the right of the figure.

The figure 2 also shows a protection device against the particles generated by the electric arc formed between the ends of the parts 31 and 32. In this embodiment, the protection device comprises three protection elements: the elements 43, 44 and 45.

The elements 43, 44 and 45 are arranged to trap the particles emitted by the switching arc as shown by the curved arrows on the figure 2 .

Element 44 is not always essential. It can be omitted if the circuit breaker configuration allows it.

The element 43 is a spark arrester, that is to say a screen that retains the emitted particles. This element can also perform the function of the corona shield and make it possible to improve the distribution of the electric field prevailing inside the circuit-breaker. In the case of use as a corona barrier, the element 43 must be metallic or metallized.

The elements 44 and 45 are very close to the parts 31 and 32 in relative movement and are, for this reason, made of electrically insulating material.

The elements 43 and 45 can be made in one piece if this piece is insulating material. This piece can be metallized on the side designated by crosses on the figure 2 , and the metallization can be put to the potential of the piece 31.

The protection device according to the invention makes it possible to prevent the particles generated by the electric arc from entering zone A, which is a highly dielectrically stressed zone.

The efficiency provided by the protection device according to the invention is optimal if the conductive part 32 (that is to say the conductive part which in this example is the moving part), or at least its end 34, remains under the element 45 until the extinction of the switching arc.

The elements 43, 44 and 45 are for example fixed to a fixed part of the circuit breaker by means available to those skilled in the art. In the case of a circuit-breaker of the type represented partially in figure 1 , the elements 43, 44 and 45 of the protective device can be fixed to the upper part 3 of the housing 1 to provide protection against the particles generated by the electric arc during the separation between the fixed contact 6 and the movable contact 8 .

If, as for the circuit breaker figure 1 , the contact surfaces of the first part 31 and the second part 32 are of cylindrical shape, the elements 43 and 44 are also of cylindrical shape and are located on either side of the fixed and movable contacts 6 and 8. element 45 then has the shape of a ring.

Claims (6)

1. A protection device for providing protection against the particles generated by an electric arc when a first electrically conductive part (31) and a second electrically conductive part (32) of an electrical connection unit are separated from each other, the first and the second electrically conductive parts each having a contact surface of cylindrical shape and separation of the first and second parts is performed by relative sliding of one of the contact surfaces on the other contact surface, the protection device including a protection element (43) disposed in the proximity of the place at which the first part (31) and the second part (32) separate and disposed facing one of the contact surfaces in order to form a shield against said particles, the protection element (43) being of cylindrical shape and located outside the cylindrical shapes of the first and second parts, characterized in that the device comprises an other protection element of cylindrical shape (44) located inside the cylindrical shapes of the first and the second parts.
2. A protection device according to claim 1, wherein the protection element (43) or the other protection element (44) are made of metal or are metal-plated.
3. A protection device according to claim 1, wherein the protection element (43) or the other protection element (44) are made of electrically insulating material.
4. A protection device according to any one of claims 1 to 3, including a supplementary protection element (45) in the form of a ring or a ring sector, located inside the cylindrical shapes of the first and second parts, substantially perpendicular to a sliding direction of the contact surfaces relative to each other and facing a contact surface that is uncovered by the contact surfaces sliding relative to each other.
5. A protection device according to claim 4, wherein the supplementary protection element (45) is made of electrically insulating material.
6. A circuit breaker including a main electrical circuit intended for passing electric current when the circuit breaker is in the closed position and a secondary electrical circuit intended for interrupting current in order to place the circuit breaker in the open position, the main electrical circuit including an electrical connection unit fitted with a protection device according to any one of claims 1 to 5 for providing protection against the particles generated by an electric arc.

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