EP4053873A1

EP4053873A1 - Insulating nozzle for circuit breaker with improved inner configuration

Info

Publication number: EP4053873A1
Application number: EP21160769.2A
Authority: EP
Inventors: Emilien Pierres
Original assignee: General Electric Technology GmbH
Current assignee: GE Vernova GmbH
Priority date: 2021-03-04
Filing date: 2021-03-04
Publication date: 2022-09-07
Also published as: WO2022184818A1

Abstract

An electric arc-blast nozzle (100) for circuit breaker comprising a median part (100b) internally defining an axial passage (130) for a male arc contact, the axial passage having, in the direction of flow of a blowing gas which exits from the nozzle a first region (131) and a second region (132) narrowed relative to the first region (131) (figure 7).

Description

TECHNICAL FIELD

The present invention relates to an improved nozzle intended to be included in a medium- or high- or very high-voltage circuit breaker and also to a medium- or high- or very high-voltage circuit breaker including such a nozzle.

PRIOR ART

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or a short circuit. Once a fault is detected, the circuit breaker contacts open and separate to interrupt the circuit. A high voltage circuit breaker generally comprises at least one female arc contact 2, also called "tulip contact" that is typically made of contact fingers in a shape of tulip, and at least one male arc contact 4 that may be in a shape of a pin and called "pin contact". Such a device further includes an insulating nozzle 10 that is mechanically attached to the female contact 2.
During an opening operation of the circuit breaker that is conducted to interrupt current, a moving contact, typically the male contact 4, is traveling inside a nozzle internal passage while the contacts 2, 4 are separated and an arc is formed.
Thus, when a high current or voltage is interrupted, an electrical arc is generated between the contacts and such arc must be terminated. The strong radiations generated by this arc inside the nozzle passage evaporate the nozzle material and generate locally high pressure and heat. A part of pressurized gas is accumulated inside an expansion volume 21 and will help to extinguish the arc by blowing on it at the end of the interruption process. The nozzle 10 is thus configured to participate to the blow out the arc.
A conventional nozzle 10 is shown in figures 1 to 4. It comprises the following parts:

a median part 10b also called "neck" internally defining an axial passage 13,
a first end 10a part extending on a first side of the median part and defining internally a first volume 12 communicating with the axial passage 13,
a second end 10c part extending on a second side of the median part opposite said first side, said second end part defining internally a second volume 14 communicating with the axial passage 13 and situated opposite the first volume.

The first internal volume 12 of the nozzle 10 is configured to accommodate the female contact 2. During the various phases of operations, the female contact 2 typically remains in the first volume 12. The male contact 4 is caused to move between various phases of operations in the axial passage 13. Thus, the axial passage 13 is configured to accommodate the moving contact 4 and has typically a section narrowed compared to the first and second volumes 12, 14 of the nozzle 10.
When the circuit breaker is in closed position (figure 1), the male contact 4 extends into the second volume 14, into the axial passage 13 and into the first volume 12. To cut the current, the male contact 4 and the female contact 2 are moved away from each other (figures 2 and 3), so that the male contact 4 leaves the first volume 12 and moves in the axial passage 13 towards the second volume 14. During the "opening", the male contact 4 must be well aligned with the nozzle axial passage 13 in order to avoid mechanical high speed impact and damage of the circuit-breaker. In that purpose, the gap between the male contact 4 and the inner wall of the axial passage 13 is rarely lower than 1 mm.
While approaching the contacts 2, 4 during the closing, the electrical field on the male contact 4 and female contact 2 increases until arc ignition between them. In the case of very high voltage, the nozzle axial passage 13 may be provided rather long. Due to vibration or a wrong alignment there is a risk of mechanical contact between the male contact 4 tip and the nozzle 10 inner wall 11 in the axial passage 13 (figure 3). This may induce the arc ignition along the nozzle neck earlier in the closing process, or the arc uncontrolled re-ignition in the opening process. This phenomenon is accentuated by a high tangential electrical field on the nozzle neck surface 11 and leads to a higher risk of damaging the nozzle by the arc.
In order to respond to the requirements listed above, the axial passage 13 usually have a constant diameter D and the gap between the male contact 4 and the inner wall 11 of the nozzle neck is rarely lower than 1 mm.
However, the gas pressure rise is one of the most important parameter for current breaking. But as described above, the space between the male contact 4 and the nozzle neck inner wall is provided in order to prevent mechanical impact of the pin on the nozzle. Consequently, the pressure rise is not optimized for current breaking. There is also a risk of contact of the pin inside the nozzle neck when opening and closing at high travel speed, leading to uncontrolled arc ignition and a risk of nozzle damage (figures 3 and 4).
There is therefore a need to find a new circuit breaker structure that is improved with respect to at least one of the disadvantages listed above.

SUMMARY OF THE INVENTION

According to a particular aspect, an embodiment of the present invention provides a nozzle for a circuit breaker comprising:

a median part internally defining an axial passage for a male arc contact,
a first end part extending on a first side of the median part, said first end part defining internally a first volume for a female arc contact, said first volume communicating with said axial passage and being configured to receive a female arc contact,
a second end part extending on a second side of the median part opposite said first side, said second end part defining internally a second volume for said male arc contact, the axial passage having, in a direction going from the first volume towards the second volume, a first region communicating with the first volume and provided with a first cross section, in the extension of the first region, a second region communicating with the second volume, the second region having a narrowed cross section relative to the first cross section.

Such a configuration enables better guidance of a moving contact in the axial passage and reduces the risk of pin impact in a high electrical field area. It further participates to obtain higher pressure blast.
Advantageously, the axial passage may comprise a narrowing between the first region and the second region.
According to an embodiment, the narrowing may have a linearly decreasing section from the first region to the second region.
Advantageously, the first region has a first length L₁ and the second region has a second length L₂, said second length L₂ being lower than said first length L₁.
According to a particular embodiment, the axial passage is defined by a wall made of dielectric material such as a fluoropolymer or a ceramic material.
The invention further provides a medium-, high-, or very high-voltage circuit breaker comprising an electric arc-blast nozzle such as defined above.
The circuit breaker typically further provides two arc contacts that can be axially moved in relation to each other, between a circuit breaker opening position in which the arc contacts and are separated from each other and a circuit breaker closing position in which the arc contacts and are in contact with each other, said two arc contacts comprising a female arc contact arranged in said first volume and a male contact.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be better understood on reading the description of exemplary embodiments given, purely as an indication and in no way limiting, with reference to the appended drawings in which:

Figure 1 shows a partial schematic longitudinal section of a circuit breaker comprising an electric art blast nozzle according to the prior art, the circuit breaker being shown in a closed position";
Figure 2 shows the same circuit breaker during an opening operation";
Figure 3 shows the same circuit breaker shown during opening operation, when a male contact is misaligned°;
Figure 4 shows the same circuit breaker during closing operation, also with a misaligned position of the male contact in the axial passage of the nozzle neck";
Figure 5 shows a partial schematic longitudinal section of a circuit breaker comprising a nozzle implemented according to an embodiment of the present invention";
Figure 6 shows a partial schematic longitudinal section of a circuit breaker comprising a nozzle implemented according to an embodiment of the present invention, in a closed position of the circuit breaker wherein the arc contacts are in contact with one other";
Figure 7 shows a partial schematic longitudinal section of a circuit breaker comprising a nozzle implemented according to an embodiment of the present invention, during opening operation of the circuit breaker";
Figure 8 shows a partial schematic longitudinal section of a circuit breaker comprising a nozzle implemented according to an embodiment of the present invention, during opening or closing operation in case a male arc contact is subject to vibrations";

DETAILED DESCRIPTION

Figures 5-8 show a part of a circuit breaker provided with an electric arc-blast nozzle 100 according to an embodiment of the present invention.
In the partial view given in figure 5, the male contact 40 is not shown in order to facilitate reading.
The nozzle 100 comprises a first end 100a part extending on a first side and defining internally a first volume 120, a second end 100c part extending on a second side opposite said first side, and defining internally a second volume 140 that is situated opposite the first volume. The nozzle 100 further comprises a median 100b neck-forming part between said end parts 100a, 100c and defining internally an axial passage 130 that is situated between the first volume 120 and the second volume 140 and communicates with the first volume 120 and the second volume 140.
These parts 100a, 100b, 100c may have a symmetrical revolution around axis A'A (i.e. an axis parallel to the x-axis of an orthogonal marker [O; x; y; z] given in the figures. The end parts 100a and 100c respectively receive and surround arc contacts 20 and 40.
The first end part 100a, may be disposed upstream and the second end part 100b disposed downstream in the direction of the flow of an electric arc cut-off gas.
In the extension of the first end of the nozzle 100, a pressurized gas is accumulated inside an expansion volume 121 located outside the nozzle 100 and communicating with the first volume 120 of the nozzle. After, passing though the axial passage 130, the pressurized gas is expelled of the nozzle 10 via the second volume 140.
The axial passage 130 has a smaller cross-section than that of the first volume 120 since the latter accommodates a first arc contact 20, which is typically a female contact 20 e.g. in the form of a tulip contact. This female contact 20 is attached to the nozzle 100. The axial passage 130 is configured to accommodate only a second arc contact (not represented in figure 5) which is a male contact 40 e.g. in the form of a pin contact.
An improved profile of the insulating nozzle 100 inner wall 135 is here proposed. The axial passage 130 has the particularity of not having a constant section and is, in the present case, provided with regions 131, 132 of different sections. The axial passage 130 comprises, in the extension of the first volume 120, a first region 131 communicating with the first volume 120 and with a first cross section. In the extension of the first region 131 of the passage 130, the axial passage 130 further comprises a second region 132 of section narrowed relative to the first region 131. The second region 132 of the axial passage 130 is thus provided with a second cross section smaller than the first cross section. By "cross section" it is here meant a section taken orthogonally to a longitudinal direction defined parallel to the x-axis of the reference system [O; x; y; z].
Hence, in a direction taken from the first end 100a of the nozzle 100 on the side of a female contact 20 to the second end 100b of the nozzle opposite to the first end 100a, the axial passage 130 is provided with a narrowing.
Such a configuration of the axial passage 130 located in the median part 100b of the nozzle 100 is provided, in order to limit a contact between a moving arc male contact 40 and the internal wall 135 of the nozzle 100 in a critical region of the nozzle 100, that is to say in the vicinity of the female contact 20. It further allows a lower leak between the male contact 40 and the nozzle 100 internal wall and enables higher pressure blast. A better guidance of the moving contact 40 is also obtained. It reduces the risk of pin impact in high electrical field area on the nozzle 100 neck 100b. With such a configuration, the formation of triple points, the metallization of the insulator inner wall in the first region 131 are avoided and thus the unexpected formation of arcs at this surface is avoided.
In the median part of the nozzle 100, instead of having an axial passage 130 with an inner diameter that is constant or increasing in the direction of the male contact 40, here is provided an axial passage 130 with a second region 132 having a diameter D2 that is reduced compared to that D1 of the first region 131 (D1, D2 being dimensions measured parallel to γ-axis of an orthogonal mark [O;°x;°y;°z] given in the Figures), thereby reducing the gas flow out of the nozzle 100. The second diameter D2 may correspond substantially to the diameter of an axial passage of a conventional nozzle.
According to a particular example, the first diameter D₁ may be for example between 19 and 21 mm whereas the second diameter D2 may be for example 18mm.
In the axial passage 130, the first region 131 of larger cross-section is preferably provided with a first length L₁ greater than the second length L₂ of the second region 132 (L₁ and L₂ being dimensions measured parallel to the longitudinal axis of the nozzle parallel to an x-axis of the orthogonal mark [O;°x;°y;°z]). Thus, in combination with the narrowing, this helps to minimize potential metallization of the inner wall of the nozzle 100 when the male arc contact 40 moves.
The second length L₂ may be comprised between 50% and 70% of the total L axial passage length.
According to a particular example, the first length L₁ may be for example between 50 and 70mm whereas the second length L2 may be for example between 50 and 30 mm.
To promote the circulation and ejection of gas out of the nozzle 100, inner wall of the axial passage 130 is such that the change of section between the first region 131 and the second region 132 of the axial passage 130 is done gradually. An intermediate region 133 of decreasing cross section is thus advantageously provided between said first region 131 and said second region 132 of the axial passage 130. The intermediate region 133 can in particular be delimited by means of a frustoconical part 133a between the first region 131 and the second region 132. The intermediate region 133 may have thus a linearly decreasing section from the first region 131 to the second region 132.
The nozzle 100 is typically made of at least a dielectric material. The axial passage 130 is delimited by wall(s) 131a, 132a, 133a that is/are typically formed of at least a dielectric or insulating material. This material can be e.g a composition comprising a fluorocarbon polymer matrix, such as polytetrafluoroethylene (PTFE), or a ceramic material.
In Figure 6, the circuit breaker is shown in a closed position wherein arc contacts 20, 40 are in contact with one other such that a current can flow. When the arc contacts 20 and 40 are in contact with each other the male arc contact 40 closes the axial passage 130 of the nozzle partially and extends up to the first volume 120.
In Figure 7, the circuit breaker is then shown during opening, the first region 131 of the axial passage 130 with increased diameter being provided with an inner surface SV of vaporization 131a that is larger. Therefore the pressure increase during arc extinction is higher. There is an electric arc cut-off gas routing channel between the male arc contact 40 and the wall 132a of the second region 132, which allows the circulation of gas in the axial passage 130, from its inlet to its outlet, to cut an electric arc that is likely to be formed during the movement of arc contacts 20 and 40 from the closing position to the opening position of the circuit breaker. The leakage around the male contact 40 is lower in the second region 132, so the pneumatic and self-blast effect for arc extinction during opening is not reduced.
Figure 8 shows a closing operation in a particular case due to the effect of a potential vibration or to a misalignment of the male contact 40 in the axial passage 130. Due to the configuration of the axial passage 130, the pin is better guided. Possible metallic traces left on the nozzle inner surface 131a near the tulip contact is avoided, which is particularly important during closing operation under high voltage condition. The pin cannot impact the nozzle neck in the critical area of high electric field close to tulip contact during closing under high voltage condition.
An arrangement as described above is situated in an arc-control chamber of the circuit breaker. The arc-control chamber is typically arranged inside a casing. The arc-control chamber is thus placed in a space that is internally defined by this casing. This space is usually filled with an insulating gas, such as SF6 or dry air or nitrogen or carbon dioxide CO₂ or a gaseous mix comprising mainly CO₂.
Besides the above mentioned arcing contacts, the chamber includes another set of electrical contacts (not shown) comprising a first main contact cooperating with a second main contact.
A nozzle as described above can be adapted to various circuit breakers from medium-voltage to high-voltage circuit breakers, i.e. operating at voltages typically ranging between 52 kV and 1200 kV.
The invention is not limited to a circuit breaker as described above with one fixed and one moving contact. The invention may in particular be applied to double-motion circuit breakers.

Claims

An electric arc-blast nozzle (100) for a circuit breaker comprising:
- a median part (100b) internally defining an axial passage (130) for a male arc contact,

- a first end part (100a) extending on a first side of the median part, said first end part defining internally a first volume (120) for a female arc contact, said first volume (120) communicating with said axial passage (130),

- a second end part (100c) extending on a second side of the median part opposite said first side, said second end part defining internally a second volume (140) for said male arc contact, the axial passage having, in a direction going from the first volume towards the second volume, a first region (131) communicating with the first volume (120) and provided with a first cross section, and in the extension of the first region, a second region (132) communicating with the second volume (140), the second region (132) having a narrowed cross section relative to said first cross section.
A nozzle (100) according to claim 1, wherein the axial passage (130) comprises an intermediate region (133) with a narrowing section between the first region (131) and the second region (132).
A nozzle (100) according to claim 1 or 2, said intermediate region (133) having a linearly decreasing section from the first region (131) to the second region (132).
A nozzle (100) according to any of the claims 1 to 3, wherein the first region (131) has a first length L₁ and wherein the second region (132) has a second length L₂, said second length L₂ being lower than said first length L₁.
A nozzle (100) according to any of the claims 1 to 4, wherein the axial passage (130) is defined by a wall made of dielectric material such as a fluoropolymer or a ceramic material.
A medium-, high-, or very high-voltage circuit breaker comprising:
- an electric arc-blast nozzle (100) such as defined according to any one of the claims 1 to 4,

- at least two arc contacts that can be axially moved in relation to each other, between a circuit breaker opening position in which the arc contacts (20) and (40) are separated from each other and a circuit breaker closing position in which the arc contacts (20) and (40) are in contact with each other, said two arc contacts comprising a female arc contact (20) arranged in said first volume and a male contact.