EP4651167A1

EP4651167A1 - Arc chute for a direct current switching device

Info

Publication number: EP4651167A1
Application number: EP24175493.6A
Authority: EP
Inventors: Piotr Honkisz; Adam Skrudlik; Jakub LUGOWSKI; Jacek Mrowiec
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-05-13
Filing date: 2024-05-13
Publication date: 2025-11-19

Abstract

The present invention discloses an arc chute for a direct current switching device comprising at least one stack formed by a plurality of substantially parallel metallic splitter plates (1), at least one stack formed by a plurality of substantially parallel insulation plates (3), the edges of the insulation plates (3) facing the edges of the splitter plates (1), a housing (2) made of electrically insulating material surrounding at least one stack of splitter plates (1) and at least one stack of insulation plates (3). Between splitter plates (1) and insulation plates (3) there is provided a separator (4a, 4b) having insulative properties.

Description

Technical Field

The invention belongs to the field of electrical switching devices with arc chutes for arc quenching. More particularly, the invention relates to an arc chute for direct current (DC) switching device, especially circuit breaker.

Background

Circuit breakers are devices used to interrupt the electric current flow especially in the case of abnormal operating conditions, for example current overload. When a fault occurs, a circuit breaker interrupts the current by moving the contacts apart. Upon separation of the contacts, an electric arc is generated between them. An electric arc is the discharge of electric current through gas or air. Electric arc or arc discharge generates a large amount of heat, which can cause damage to the contacts by melting them, as well as it can cause damage to other components of the circuit breaker. Moreover, as the arc temperature is very high, when a surrounding structure is melted and broken, a metal powder or soot of carbon is produced, which adheres to a main contact. Thus, a contact resistance at an adhering portion is increased, and there is a possibility that energization fault occurs. According to that, frequent condition checks of main contact are required, and the adhering portion needs to be frequently removed.
Therefore, to minimize the damage, the arc needs to be safely and rapidly extinguished, and the current needs to be interrupted as soon as possible. For this purpose, arc chutes are used which are placed near the circuit breaker contacts. Thus, arc chutes are one of the key components of circuit breakers - they protect the circuit breakers from heat and damages caused as a result of arc formation.
Alternating current (AC) switching systems utilize the naturally occurring zero-crossings of the alternating current flowing through the switching system for extinguishing the arc. Direct current (DC) switching systems cannot utilize natural zero-crossings since there are none - DC current does not pass through zero like AC. Thus, for DC switching systems, circuit breaker has to reduce the current down to zero by itself (forcing the current passage to zero). When connecting such a circuit breaker to a DC circuit, unlike an AC circuit in which the current zero point is set at regular intervals, the arc generated when the DC circuit is interrupted continues. Therefore, the conventional circuit breakers connected to the DC circuit increase the arc voltage by increasing the gap between the fixed and movable contacts at the time of opening, and the voltage between the contacts is higher than the power supply voltage of the DC circuit. In this way, the current drops down and is interrupted.
As known from the art, arc chutes are made of a highly durable, arc-proof material, in which the arc plates (splitter plates) have been integrated. Arc chute contains a set of stacks of substantially parallel metal plates insulated from each other by an air gap between each of them. The splitter plates split the arc into partial arcs and increase the arc voltage by multiplying the anode and cathode voltage drop. Because of their high heat capacity, the plates and arc chute walls absorb a large amount of the arc's energy. Thus, arc chute allows to divide, cool down and extinguish the electric arc. Specifically, the metal splitter plates, normally made of ferromagnetic material, allow to elongate the arc in arc chute.
The arc is attracted by magnetic and fluid-dynamic forces towards and between the splitter plates. The structure of the arc chute lengthens the arc further and splits it into small segments. This increases the arc length, cools it down and finally arc is extinguished.
The simplest known arc chutes do not comprise any insulating plates (especially these used for circuit breakers having lower short-circuit capacities). Other known arc chutes comprise insulation plates or other insulation elements placed above the splitter plates. Generally, insulation plates or other insulating elements allow to limit the speed of the arc spreading and allow to keep the arc inside the arc chute as long as possible, until it is completely extinguished. Additionally, insulation plates cool down the arc by increasing its resistance. They also help to increase the overall length of the arc.
There are many prior art documents which relate to several different problems in the field of arc breakers.
For example, EP3229250B1 discloses a DC high-speed circuit breaker comprising an arc chute including insulation plates and a plurality of grids which are arranged on the upper side of fixed main contact and movable main contact, wherein said grids are configured by combining a flat plate grid and a U-shaped grid. Insulation plate is disposed on the side surface in the plate thickness direction of the flat grid to prevent the arc from jumping out of the flat grid, and on the side surface of the U-shaped grid.
CN210403640U discloses an arc extinguishing cover of a direct current quick breaker comprising an insulating shell and an arc extinguishing grid plate component arranged in the insulating shell. The insulating shell is enclosed into a square frame by a left side plate, a right side plate, a front end plate and a rear end plate, h-shaped isolation plates are arranged at the lower parts of the left side plate and the right side plate, L-shaped arc striking angles are clamped in clamping grooves at the bottoms of the front end plate and the rear end plate. The arc extinguishing grid plate component comprises a first arc extinguishing grid plate component and a second arc extinguishing grid plate component which are alternately arranged. First arc extinguishing bars piece subassembly is formed by first insulating bars piece and first metal bars piece overlap joint from top to bottom. Second arc extinguishing bars piece subassembly is formed by second insulating bars piece and second metal bars piece overlap joint from top to bottom.
Document US4405847A discloses an arc chute for a circuit breaker including a plurality of steel arc splitter plates. Each plate has a pair of spaced parallel limbs of rectangular cross-section diverging from a central notch and having ends of quadrant form centered on the outer edge portions of the limbs. At an end portion remote from the limbs the plate is coated with an insulating material. Spaced along each limb and opposed edge regions of the rectangular portion are a series of aligning bores. The series arcs are prevented from escaping from the arc chute by the presence of the coating of insulating material on the arc splitter plates.
Nevertheless, there are several problems with known arc chutes comprising parallel splitter plates and insulation plates. In the known design of the DC arc chute, splitter plates stick or overlap of the insulation plates. During use or during type testing of maximum energy or the biggest inductance load, a common failure occurs, which is smoking and ignition of the insulation plates, due to heat transfer from splitter plates. This is caused by high temperature of splitter plates after arc interruption, as splitter plates normally reach the temperature as high as above 500°C.
Therefore, it is necessary to provide solution allowing to prevent ignition of insulation plates and reduce smoking of the insulation plates caused by high temperature of the splitter plates.

Summary

The object of the invention is to overcome said drawbacks of the prior art and to prevent heat transfer from the splitter plates to the insulation plates what reduces insulation plates temperature compared to known solutions.
This has been achieved by providing an arc chute for a direct current switching device, comprising:

at least one stack formed by a plurality of substantially parallel metallic splitter plates,
at least one stack formed by a plurality of substantially parallel insulation plates, the edges of the insulation plates facing the edges of the splitter plates,
a housing made of electrically insulating material surrounding at least one stack of splitter plates and the at least one stack of insulation plates,
wherein between splitter plates and insulation plates there is provided a separator having insulative properties.

Preferably, the separator is in the form of an air space having height of at least 1 mm.
Preferably, the separator in the form of the air space has height up to 3 mm.
Alternatively, the separator is in the form of an insulating element made of insulating material resistant to temperatures of above 500°C, whereby one separator is provided for each pair of splitter plate and insulation plate.
Preferably, the insulating material of the separator in the form of the insulating element is chosen from glass bonded mica, heater micanite, high-temperature technical ceramic, glass-cement boards.
Preferably, the separator in the form of the insulating element has thickness from 1 mm to 3 mm.
Preferably, the separator in the form of the insulating element has height from 10 mm to 40 mm.
Preferably, the splitter plates are made of ferromagnetic material.
Preferably, the splitter plates are made of steel.
Preferably, the arc chute comprises a support structure supporting the plurality of splitter plates and/or the plurality of insulation plates in spaced relation in a stack.
Alternatively, the housing has parallel grooves on the internal side of its side walls, supporting the plurality of splitter plates and/or the plurality of insulation plates in spaced relation in a stack.
Preferably, the housing is made of electrically insulative and heat resistant resin, preferably unsaturated polyester.
Preferably, the housing is made of an inorganic insulating material, preferably ceramics.
Preferably, splitter plates have cutouts placed alternately towards one and towards the other side of each subsequent splitter plate.

Brief Description of the Drawings

The present invention will be presented in a more detailed way with reference to the accompanying drawing, in which:

Fig. 1a shows the arc chute in cross-section parallel to the plane of the splitter plates, whereby the separator is in the form of the air space;
Fig. 1b shows the arc chute in cross-section parallel to the plane of the splitter plates, whereby the separator is in the form of the insulating element;
Fig. 2 shows the arc chute in cross-section parallel to the plane of the splitter plates, with a cut-out showing the grooves in which the splitter plates and insulation plates are inserted;
Fig. 3 shows the splitter plates mounted in the support structure;
Fig. 4 shows partial cross-section of the DC circuit breaker and arc chute;
Fig. 5 shows the example of the arrangement of splitter plates and insulation plates.

Detailed Description

Preferred embodiments of the invention are described in detail below. The examples serve only as an illustration and do not limit the scope of the present invention.
The invention, in general, concerns an arc chute for direct current switching device, which may be provided in various types of electric equipment such as circuit breakers, contactors etc. The device may more particularly be used in a direct current (DC) circuit breaker, specifically for low and medium voltage application. The arc chute according to the invention is designed to be used in industrial applications, for example in DC circuits on railway, tramways or metro power distribution systems, copper processing plants, mining or steel mills.
DC circuit breaker normally comprises a switch with a first switch contact and a second switch contact, wherein the second switch contact is movable between a first position, in which the first switch contact is touching the second switch contact, and a second position, in which the first and second switch contacts are separated from each other. Further, DC circuit breaker comprises an arc chute having a stack of a plurality of substantially parallel metal plates separated from each other by a certain distance, as it was described above. The arc chute typically also comprises a pair of arc horns for guiding the arc in the arc chute towards the splitter plates. Arc horns are connected with arc runners, the arc runners being elements of the circuit breaker which guide the arc towards the arc chute. In other words, arc horns placed in the arc chute are the end elements of the arc runners.
The arc chute according to the invention is schematically presented in Fig. 1a, Fig. 1b in cross-section parallel to the plane of the splitter plates 1. Arc chute comprises at least one stack formed by a plurality of substantially parallel splitter plates 1, separated by air gaps. Air gaps between splitter plates 1 may be equal or may be of different width. The housing 2 of the arc chute, surrounding the splitter plates 1, is made of electrically insulative and heat resistant material. The housing 2 is thus made, for example, of electrically insulative and heat resistant resin, such as UP (unsaturated polyester); or of inorganic insulating material such as ceramics. Splitter plates 1 are arranged in spaced relation in a stack, and their arrangement is obtained for example by inserting them into the grooves 6 located on the internal side of the housing 2 side walls, surrounding the arc chute, as shown in Fig. 2. In another embodiment, splitter plates 1 are mounted on a support structure 5 supporting the plurality of splitter plates 1 in spaced relation, placed between the housing 2 and the splitter plates 1. Fig. 3 shows a part of the arc chute comprising splitter plates 1 - thus, it shows the arrangement of the splitter plates 1 arranged in the support structure 5. However, supporting and positioning of the splitter plates 1 may be achieved differently. Fig. 4 shows partial cross-section of the DC circuit breaker and arc chute, whereby this cross-section is perpendicular to the plane of the splitter plates 1.
Preferably, splitter plates 1 may have legs 1a, formed by longitudinal protrusions of each splitter plate 1. Thus, preferably, each splitter plate 1 may be longer on its both ends have the inverted V-shaped opening. The shape of the arc splitter plate 1 and the presence of the magnetic field causes that the arc is drawn towards the apices of the V-shaped openings in each of the arc splitter plates 1. At the top of the V-shaped openings the presence of the magnetic field is mitigated and the arc is broken down into a plurality of arcs known as series arcs. Such uneven placing of the splitter plates 1 allows to make it easier for the arc to move up (from the bottom) and to move down (from the top) to extend the arc as much as possible.
As can be seen for example in Fig. 1a, Fig. 1b and Fig. 2, splitter plates 1 may have cut-outs 7, placed alternately towards one and towards the other side of each subsequent splitter plate 1, starting preferably from the center of the bottom edge of the splitter plate 1. In said Fig. 1a, Fig. 1b and Fig. 2, the first splitter plate 1 has the cut-out 7 directed to its left side, and thus the next splitter plate 1 adjacent to it (subsequent splitter plate 1) has the cut-out 7 directed to its right side (not visible). This is an optional feature, intended to facilitate movement of the arc upwards.
The arc chute has insulation plates 3 placed above the splitter plates 1, as shown in Fig. 1a, Fig. 1b and Fig. 2. Insulation plates 3 also form a stack like splitter plates 1. In exemplary embodiment, the number of insulation plates 3 may be equal to the number of splitter plates 1. In another embodiment, for example due to the structure of the arc chute (due to presence of mounting points of the arc chute on the side walls of the housing), the number of insulation plates 3 may be smaller than the number of the splitter plates 1. Insulation plates 3 are also arranged in spaced relation in a stack. Their arrangement is obtained for example by inserting them into the grooves 6 located on the internal side of the housing 2 side walls, as shown in Fig. 2, or by mounting them on a support structure 5 supporting the plurality of insulation plates 3 in spaced relation (not visible). In the embodiment, splitter plates 1 are of alternating heights and the heights of the corresponding insulation plates 3 correspond to the heights of the splitter plates 1 (shown in Fig. 5). This type of arrangement also additionally protects the insulation plates 3 from excessive degradation.
The essence of the invention is providing separation between splitter plates 1 and insulation plates 3. Thus, between splitter plates 1 and insulation plates 3 there is provided separation in the form of an separator 4a, 4b, separating splitter plates 1 from insulation plates 3 on their whole or partial width. The presence of the separator 4a, 4b is most important in the area of direct exposure to the arc, where the splitter plates 1 are heated up the most (thus not all of the area between splitter plates 1 and insulation plates 3 has to be separated by separator 4a, 4b.
In the first embodiment, shown in Fig. 1a, the separator 4a is formed as an air space. The air space preferably has height of at least 1 mm. Experiment has proven that even such a small air space (~ 1mm) between splitter plates 1 and insulation plates 3 prevents ignition and significantly reduces smoking of insulation plates 3. The largest height of the air space, not interfering the proper operation of the arc chute, is 3 mm. Preferably, the height of the air space is 2,5 mm. The air space may be formed in various ways - for example, as a cut-out in the insulation plates 3, or as a cut-out in the splitter plates 1, or by ensuring a proper distance (of at least 1 mm) between the insulation plates 3 and the splitter plates 1 (for example by appropriate shaping of the arc chute housing 2 walls or by placing splitter plates 1 in the grooves 6 of the housing 2 or in the support structure 5 downwards, at a distance of at least 1 mm from the insulation plates 3).
In the second embodiment, shown in Fig. 1b, the separator 4b is formed as an insulating element - spacer - made of insulating material, having appropriate temperature-resistant properties. The insulating element is thus made of a material resistant to temperatures above 500°C. For example, the spacer forming the separator 4b is made of an insulating material such as glass bonded mica, heater micanite, high-temperature technical ceramic or glass-cement boards. There is provided one plate of separator 4b in the form of the spacer (insulating element) for each pair of splitter plate 1 and insulation plate 3. Thus, between splitter plates 1 and insulation plates 3 there are provided multiple plates of separators 4b, respectively to the number of said pairs. The thickness of the separator 4b being a spacer (its thickness measured horizontally and perpendicularly to splitter plates 1 plane, according to Fig. 1b) is preferably from 1 mm to 3 mm. For example, the spacer made of glass bonded mica may be 2,4 mm thick, and the spacer made of a heater micanite may be 2mm. The height of the separator 4b being a spacer (measured vertically according to Fig. 1b) is preferably from 10 mm to 40 mm. Figs. 2, 3, 4 and 5 show the embodiment as in Fig. 1a, in which the separator 4a is in the form of the air space. Nevertheless, these figures are also valid for the embodiment in which the separator 4b is in the form of the insulating element (as the only difference is the separator 4b).
Therefore, in the inventive design of the DC arc chute, splitter plates 1 no longer stick or overlap of the insulation plates 3 - the separator 4a, 4b prevents heat transfer from the splitter plates 1 to the insulation plates 3. Temperature of insulation plates 3 is reduced, and thus ignition and smoking of the insulation plates 3 is significantly reduced compared to known solutions.
The arc chute disclosed herein is intended for being arranged in a switching device such as circuit breaker, comprising a stationary contact and a moveable contact, connectable/disconnectable to said stationary contact, forming an electrical switch.

List of reference signs:

1 - splitter plate
1a - legs
2 - housing
3 - insulation plate
4a - separator in the form of the air space
4b - separator in the form of the insulating element
5 - support structure
6 - groove
7 - cut-out

Claims

An arc chute for a direct current switching device comprising
at least one stack formed by a plurality of substantially parallel metallic splitter plates (1),

at least one stack formed by a plurality of substantially parallel insulation plates (3), the edges of the insulation plates (3) facing the edges of the splitter plates (1),

a housing (2) made of electrically insulating material surrounding at least one stack of splitter plates (1) and at least one stack of insulation plates (3),

characterized in that between splitter plates (1) and insulation plates (3) there is provided a separator (4a, 4b) having insulative properties.
The arc chute for a direct current switching device according to claim 1, wherein the separator (4a) is in the form of an air space having height of at least 1 mm.
The arc chute for a direct current switching device according to claim 1 or 2, wherein the separator (4a) in the form of the air space has height up to 3 mm.
The arc chute for a direct current switching device according to claim 1, wherein the separator (4b) is in the form of an insulating element made of insulating material resistant to temperatures of above 500°C, whereby one separator (4b) is provided for each pair of splitter plate (1) and insulation plate (3).
The arc chute for a direct current switching device according to claim 4, wherein the insulating material of the separator (4b) in the form of the insulating element is chosen from glass bonded mica, heater micanite, high-temperature technical ceramic, glass-cement boards.
The arc chute for a direct current switching device according to claim 4 or 5, wherein the separator (4b) in the form of the insulating element has thickness from 1 mm to 3 mm.
The arc chute for a direct current switching device according to claim 4 or 5 or 6, wherein the separator (4b) in the form of the insulating element has height from 10 mm to 40 mm.
The arc chute for a direct current switching device according to any of the preceding claims, wherein the splitter plates (1) are made of ferromagnetic material.
The arc chute for a direct current switching device according to claim 8, wherein the splitter plates (1) are made of steel.
The arc chute for a direct current switching device according to any of the preceding claims, wherein it further comprises a support structure (5) supporting the plurality of splitter plates (1) and/or the plurality of insulation plates (3) in spaced relation in a stack.
The arc chute for a direct current switching device according to any of the claims 1 to 9, wherein the housing (2) has parallel grooves (6) on the internal side of its side walls, supporting the plurality of splitter plates (1) and/or the plurality of insulation plates (3) in spaced relation in a stack.
The arc chute for a direct current switching device according to any of the preceding claims, wherein the housing (2) is made of electrically insulative and heat resistant resin, preferably unsaturated polyester.
The arc chute for a direct current switching device according to any of the claims 1 to 11, wherein the housing (2) is made of an inorganic insulating material, preferably ceramics.
The arc chute for a direct current switching device according to any of the preceding claims, wherein splitter plates (1) have cutouts (7) placed alternately towards one and towards the other side of each subsequent splitter plate (1).