AU2018264092A1

AU2018264092A1 - Device for reducing fault arcs in an electric distribution unit

Info

Publication number: AU2018264092A1
Application number: AU2018264092A
Authority: AU
Inventors: Thomas Gattringer; George Reuberger
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2017-11-17
Filing date: 2018-11-15
Publication date: 2019-06-06
Anticipated expiration: 2038-11-15
Also published as: NL2022014B1; GB201818547D0; DE102017127077A1; GB2569233A; CN109802325A; GB2569233B; NL2022014A; CN109802325B; AU2018264092B2; DE102017127077B4

Abstract

In a device (1) for reducing fault arcs in an electric distribution unit, comprising a housing (2), a first busbar (3) and a second busbar (4), wherein the first busbar (3) has a first electric connection point (5) and the second busbar (4) has a second electric connection point (6), wherein the first busbar (3) is positioned at a distance from the second busbar (4), it is proposed that, within the housing (2), at a predetermined burn-up point (7) for a fault arc, a breakdown voltage value between the first busbar (3) and the second busbar (4) is lowest, and that the housing (2) is open. 10,1 4,18 15 r ~ I r5,18 2,8 Fig.1 2,13 2,13

Description

The present invention refers to a device for reducing fault arcs in an electric distribution unit

Fault arcs occurring in an electric distribution unit, such as an electric cabinet, represent a great danger due to the sudden and unpredicted high 5 power generated, which may have explosive effects. On one hand, long inactivity periods and costly maintenance may occur due to the damage caused by fault arcs. Moreover, fault arcs often occur in case of unproperly executed maintenance work, as a result of which operators are frequently injured.

The generation of a fault arc inside an electric distribution unit may have various causes. Frequently, a tool or other loose object left in the distribution unit may cause fault arcs when the distribution unit is switched on. A further possibility of generating a fault arc is when, at switch-off of a low voltage power switch, ionized air is expelled from the electric distribution unit and reduces the breakdown voltage between the phases. Since induced voltage peaks may also occur when switching off a low voltage power switch, a fault arc may be generated between the phases due to the combination of these two effects.

Devices for reducing fault arcs are known which detect the occurrence of a fault arc and short-circuit the phases of the electric distribution unit when a fault arc is detected so that energy is removed from the fault arc.

Such devices, which have to short-circuit the phases as fast as possible, are very complex and expensive to produce. Also, the use of electronic components is required for a fast switch-off.

An object of the invention is to provide a device for reducing fault arcs of the aforementioned type, by means of which said drawbacks may be 25 prevented, and which may reduce the damage caused by the occurrence of a fault arc while being very simple to produce.

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According to the invention there is provided a device for reducing fault arcs in an electric distribution unit, comprising a housing, a first busbar and a second busbar, wherein the first busbar has a first electric connection point and the second busbar has a second electric connection point, wherein the first 5 busbar is positioned at a distance from the second busbar, characterized in that, within the housing, at a predetermined burn-up point for a fault arc, a breakdown voltage value between the first busbar and the second busbar is lowest, and that the housing is open.

Consequently, the advantage is obtained is that a predetermined position within the electric distribution unit may be provided for the fault arc, i.e. the burn-up point in the device, in which the fault arc may burn in a controllable environment until the electric distribution unit is switched off or the fault arc selfextinguishes. This is achieved by the fact that a predetermined point having the lowest breakdown voltage is formed between the first busbar and the second 15 busbar, at which point the fault arc may be either generated in presence of ionized gases or may be captured in case it is generated at another position within the electric distribution unit. Through the open housing, on one hand, ionized gas may enter and/or a fault arc moving along the phases of the electric distribution unit may be led from the phases of the electric distribution unit to the burn-up point within the housing. Thus, the destructive effects of a fault arc may be controlled, and equipment and people may be protected against damages without the use of fault-prone components such as detectors.

The invention is now explained in further detail, with reference to the annexed drawings, which only illustratively represent a preferred embodiment.

In particular:

Fig. 1 shows a preferred embodiment of the device in an axonometric view;

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Fig. 2 shows the preferred embodiment of the device in an exploded view; and

Fig. 3 shows a portion of the preferred embodiment of the device in a plan view.

Figs. 1 to 3 show at least portions of a preferred embodiment of a device for reducing fault arcs within an electric distribution unit, comprising a housing 2, a first busbar 3 and a second busbar 4, wherein the first busbar 3 has a first electric connection point 5 and the second busbar 4 has a second electric connection point 6, wherein the first busbar 3 is positioned at a distance from 10 the second busbar 4.

The device 1 is provided for reducing fault arcs within an electric distribution unit. The reduction occurs in that an uncontrolled propagation of the fault arc is prevented, and the fault arc may release its energy, which has been reduced by the device, at a predetermined point. A fault arc is an unwanted 15 electric arc. The device 1 comprises a housing 2, which housing 2 preferably has an upper housing part 13 and a lower housing part 14, which are releasably fixed to each other.

The device 1 also has a first busbar 3 and a second busbar 4. In this context, busbars 3, 4, 10 are considered to be uninsulated and solid 20 conductors, which are suitable for high currents, such as those used in busbar distribution systems within low voltage distribution units. The first busbar 3 has a first electric connection point 5, which is provided for connection to a first phase of the electric distribution unit. The second bus bar 5 has a second connection point 6, which is provided for connection to a second phase of the 25 electric distribution unit.

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The first busbar 3 is also positioned at a distance from the second busbar 4, so that the first busbar 3 is not electrically contacting the second busbar 4.

Within the housing 2, at a predetermined burn-up point 7 for a fault arc, the breakdown voltage between the first busbar 3 and the second busbar 4 is lowest and the housing 2 is open.

The first busbar 3 and the second busbar 4 are thus formed in a way that at a predetermined point, which is called the burn-up point 7 for a fault arc, the breakdown voltage between the first busbar 3 and the second busbar 4 has the 10 lowest value. The breakdown voltage is the voltage required for generating the electric arc. In this case, the presence of ionized air in particular is assumed in order to calculate the breakdown voltage. The breakdown voltage is primarily determined by the geometry of the first busbar 3 and of the second busbar 4, in particular by the minimum distance between the first busbar 3 and the second 15 busbar 4. The burn-up point 7 for the fault arc may thus be in particular a restriction point where the distance between the first busbar 3 and the second busbar 4 is at a minimum. Thus, the fault arc, if present, essentially burns only at the burn-up point 7 without leaving the device 1.

The fact that the breakdown voltage between the first busbar 3 and the second busbar 4 is smallest at the burn-up point 7 for a fault arc means in particular that it is at a minimum with respect to the breakdown voltage between the first busbar 3 and the second busbar 4 both apart from the burnup point 7 as well as in particular with respect to an expected breakdown voltage of the electric distribution unit intended to be used.

The fact that the housing 2 is open means that the housing 2 has entry openings 15 for gases and/or fault arcs which are not closed. Thus, ionized gases, which may be generated in particular in case of a faulty switch-off

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2018264092 15 Nov 2018 process of a power switch and/or fault arcs may be led from outside into the housing 2 and thus also to the burn-up point 7. A faulty switch-off process is considered in this case to be a switch-off process of the power switch in which an unusually high discharge of ionized gases occurs.

The advantage thus obtained is that a predetermined point may be provided for a fault arc within the electric distribution unit, i.e. the burn-up point 7 within the device 1, in which the fault arc may burn in a controllable environment until the electric distribution unit is switched off or a self-extinction of the fault arc occurs. This is achieved by the fact that a predetermined point 10 having the lowest breakdown voltage is formed between the first busbar and the second busbar, at which point the fault arc may be either generated in presence of ionized gases or may be captured in case it is generated at another position within the electric distribution unit. By way of the open housing 2, ionized gas may enter and/or a fault arc moving along the phases of the 15 electric distribution unit may be led from the phases of the electric distribution unit to the burn-up point 7 within the housing 2. Thus the destructive effects of a fault arc may be controlled, and equipment and people may be easily protected from damages or injuries without the use of fault-prone components, such as detectors.

Preferably, it can be provided that the device 1 comprises a third busbar having a third electric connection point 11, that the third busbar 10 is positioned at a distance from the first busbar 3 and the second busbar 4, that, within the housing 2 at a further predetermined burn-up point 12 for a fault arc, the breakdown voltage between the third busbar 10 and the second busbar 4 is lowest, wherein, in particular, the further burn-up point 12 is essentially formed in the same way as the burn-up point 7 between the first busbar 3 and the

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2018264092 15 Nov 2018 second busbar 4. As a result, the device 1 may be suitable for an electric distribution unit having three phases.

The connection points 5, 6, 11 may in particular be positioned outside of the housing 2. The busbars 3, 4, 10 may then lead from the connection points 5 5, 6, 11 into the housing.

In order to form the connection points 5, 6, 11, the busbars 3, 4, 10 may be provided at an end with slots, through which a screw connection with the phases may be provided.

The busbars 3, 4, 10 may preferably be made primarily of copper.

Further preferably, an electric distribution unit, in particular an electric cabinet comprising the device 1 for reducing fault arcs, is provided within an electric distribution unit. The electric distribution unit may in particular have phases, which are also composed of busbars. Such electric distribution units are often used in low voltage applications in a main distribution facility or in industrial plants.

The device may preferably be solely connected to the phases, i.e. it may lack an additional earth or PEN conductor.

In particular, it is preferred that the electric distribution unit has a power switch, and that the device 1 for reducing fault arcs is positioned within an 20 electric distribution unit in the region of the power switch, in particular in an unprotected path of the power switch. The power switch may in particular be an open power switch and/or a low voltage power switch. In such power switches, the electric arc generated during a switch-off process is blown out by means of air through an opening so that ionized air is released in the region of the power 25 switch. The device 1 may in this case be connected to the same phases of the power switch. The arrangement of the device 1 in the area of the power switch

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2018264092 15 Nov 2018 means in this context that the device 1 is near the power switch. The device 1 may in particular be positioned in the unprotected path of the power switch.

In this case, the unprotected path of the power switch is the portion of the electric distribution unit at the power switch which is under voltage even 5 when the power switch is switched off. Specifically, if the power switch blows on a downstream path, which is therefore protected, this de-energized path is not endangered due to the switch-off process of the power switch, but the unprotected path positioned upstream of the power switch is. The fault arc may be burned off there in a controlled way until further protection devices de10 energize this portion as well.

The device 1 may in particular be composed of a module. In this case, the device 1 is already provided as a finished unit and only a connection with the phases of the electric distribution unit is required. A modular device 1 is advantageous in that it may be rapidly mounted or replaced. This is particularly 15 advantageous since the device 1 has to be replaced after the occurrence of a fault arc.

Alternatively, the device 1 may be directly mounted into the electric distribution unit.

In particular, it is advantageous that the housing 2 has a high20 temperature-resistant and electrically insulating cladding part 8. The cladding part 8 has both the task of preventing, for as long as possible, the destruction of the housing 2 by the fault arc and the task of insulating the inside of the housing 2 from the outside. The cladding part 8 may also have the function of absorbing a portion of the thermal energy which is released by the fault arc and 25 thus of cooling down the fault arc. The cladding part 8 may also be in particular composed of a plurality of parts.

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The cladding part 8 may in particular be composed of ceramics or stone, preferably fireclay.

Preferably, the cladding part 8 may in particular be made of a duroplastic material which is preferably reinforced by fibers, such as in particular 5 Durostone. Thus, the cladding part 8 may additionally better resist the pressure wave caused by the electric arc.

According to the preferred embodiment of the device 1, the housing 2 has an additional external cover 17 surrounding the high-temperature-resistant and electrically insulating cladding part 8.

Alternatively, the housing 2 may only be composed of the cladding part

8.

In particular it is preferred that the first busbar 3 and/or the second busbar 4 have an electrode 9 at the burn-up point 7. The electrode 9 may in particular be part of the busbar 3, 4, 10 which is made of a material that is 15 different from the rest of the busbar 3, 4, 10. As a result, the portion of the busbar 3, 4, 10 which is subject to the highest stress due to the fault arc may be better protected against those stresses.

It may preferably be provided that the electrode 9 is made of a metal or a metal alloy having a melting point higher than 1,200°C.

It may also be preferably provided that the electrode 9 has a convex shape. Due to the convex shape, a defined and larger contact surface for the fault arc may be provided, thus reducing wear. Moreover, due to the convex shape, the electric field strength is increased, as a result of which the breakdown voltage may be reduced. The convex shape may in particular have a radius of essentially 50 mm.

Preferably, the electrode 9 is formed by a head of a carriage bolt 16.

Thus, the electrode 9 may be particularly easy to form.

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A side opposite to the electrode 9 may be preferably formed by a counter-electrode 20.

The counter-electrode 20 may in particular also have a convex shape.

The minimum distance between the electrode 9 and the counter5 electrode 20 is preferably kept as small as possible in order to still comply with the required minimum leakage path and air gap requirements.

A minimum distance between the electrode 9 and the counter-electrode 20 may in particular be between 10 mm and 15 mm, preferably essentially 11.5 mm.

Moreover, the electrode 9 may have an electric conductivity lower than

10^Λ7 A/(Vm). This electric conductivity is thus smaller than copper, which is about 6*10^Λ7 A/(Vm). Due to the reduced electric conductivity, the current value of the fault arc is reduced, whereby wear is reduced.

Particularly advantageous is the case when the electrode 9 is made of steel, in particular stainless steel. Steel, in particular stainless steel, is particularly suitable since the wear on it caused by the fault arc is lower due to its high mechanical strength, thermal resistance and relatively low electric conductivity.

Particularly preferably, it can be provided that a fault arc propagation region free from built-in components and extending from the connection points

5, 6 to the burn-up point 7 be arranged between the first busbar 3 and the second busbar 4. The fault arc propagation region is in this case a free space extending from the connection points 5, 6 to the burn-up point 7, along which a fault arc generated outside of the device 1 may propagate, unhindered, to the 25 burn-up point 7. In this case, it can in particular be provided that, at the position on the housing 2 where the busbars 3, 4, 10 penetrate from outside into the housing 2, the space between the busbars 3, 4, 10 is not enclosed by the

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2018264092 15 Nov 2018 housing 2. Thus, entry openings 15, which are not closed, may be formed between the busbars 3, 4, 10. Thus, a fault arc which was initially propagating in the electric distribution unit may be led to the burn-up point, where it is then retained.

Preferably, the housing 2 may be provided with a slot in the region of the connection points 5, 6, 11, through which the busbars 3, 4, 10 pass. The slot may in particular be formed between the housing upper part 13 and the housing lower part 14.

First parts 18 of the busbars 3, 4, 10 may have a plate-like shape, and in particular they may be placed in a plane, wherein preferably the second busbar 4 is positioned between the first busbar 3 and the third busbar 10.

The first busbar 3 and the third busbar 10 may preferably be essentially formed by the first part 18 only.

The second busbar 4 may preferably have a second part 19, which protrudes from the plane and extends over the first busbar 3 and the third busbar 10. The electrodes 9 may be positioned on the second part 19. Thus, the burn-up points 7, 12 may be readily produced.

A reliable distancing between the busbars 3, 4, 10 may be obtained by insulating distance pieces 21.

Moreover, an electrically insulating separation piece having an aperture may be positioned at the burn-up point Ί between the first busbar 3 and the second busbar 4. The separation piece is not shown in Figs. 1 to 3. The fault arc may burn in the aperture, wherein the separation piece prevents a lateral propagation of the fault arc, thus limiting its power.

Moreover, the aperture in the separation piece may be smaller than the electrode 9, in order to prevent an unwanted collision between the electrode 9 and the counter-electrode 20.

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The aperture in the separation piece may in particular have an open edge. Thus, the fault arc may move from outside into the aperture.

Alternatively, the aperture in the separation piece may be closed, i.e. only represent a hole. This hinders the movement of the fault arc from outside 5 into the burn-up point 7. However, the fault arc may still form in the burn-up point 7, wherein the closed aperture reliably holds the fault arc at the burn-up point 7.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

1. A device for reducing fault arcs in an electric distribution unit, comprising a housing, a first busbar and a second busbar, wherein the first busbar has a first electric connection point and the second busbar has a second electric connection point, wherein the first busbar is positioned at a distance from the second busbar, characterized in that, within the housing, at a predetermined burn-up point for a fault arc, a breakdown voltage value between the first busbar and the second busbar is lowest, and that the housing is open.
2. The device of claim 1, characterized in that the housing has a hightemperature-resistant and electrically insulating cladding part.
3. The device of claim 1 or 2, characterized in that the first busbar and/or the second busbar have an electrode at the burn-up point.
4. The device of claim 3, characterized in that the electrode has a convex shape.
5. The device of claim 3 or 4, characterized in that the electrode has an electric conductivity lower than 10^Λ7 A/(Vm).
6. The device of any of claims 3 to 5, characterized in that the electrode (9) is made of steel, in particular stainless steel.
7. The device of any of claims 1 to 6, characterized in that a fault arc propagation region, which is free from built-in components and which extends from the connection points to the burn-up point, is positioned between the first busbar and the second busbar.

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8. The device of any of claims 1 to 7, characterized in that an electrically insulating separation piece having an aperture is positioned at the burn-up point between the first busbar and the second busbar.
9. The device of any of claims 1 to 8, characterized in that the device has a third busbar having a third electric connection point, that the third busbar is positioned at a distance from the first busbar and the second busbar, that, within the housing, the breakdown voltage between the third busbar and the second busbar is lowest at a predetermined further burn-up point for a fault arc, wherein in particular the further burn-up point is essentially formed in the same way as the burn-up point between the first busbar and the second busbar.
10. An electric distribution unit, in particular an electric cabinet, comprising a device for reducing fault arcs in an electric distribution unit according to any of claims 1 to 9.
11. The electric distribution unit of claim 10, characterized in that the electric distribution unit has a power switch, and that the device for reducing fault arcs in an electric distribution unit is positioned in the region of the power switch, in particular within an unprotected path of the power switch.