WO2011044624A1

WO2011044624A1 - Arc flash protection apparatus

Info

Publication number: WO2011044624A1
Application number: PCT/AU2010/001350
Authority: WO
Inventors: Bradley Scott Gradwell; Craig Louis Gradwell; Christopher John Nichols; Peter Leslie Cameron
Original assignee: Pace Engineers Group Pty Ltd
Priority date: 2009-10-16
Filing date: 2010-10-13
Publication date: 2011-04-21

Abstract

Arc flash protection apparatus including: a power supply busbar in electrical communication with a power supply; a power delivery- busbar spaced from the power supply busbar and in electrical communication with a power distribution system; and a plurality of fuses connected in parallel between the power supply busbar and the power distribution busbar.

Description

ARC FLASH PROTECTION APPARATUS FIELD OF INVENTION

THIS INVENTION relates to arc flash protection apparatus.

The invention has particular application to arc flash protection apparatus for protecting against arc flash burns to personnel working on polyphase, alternating current power supply systems. However, the invention may have application to other fields of use .

BACKGROUND ART Arc flash has long been recognised as a problem for personnel working in the area of electrical power distribution systems, particularly where such systems must be tested for operation while live. The presently available circuit breakers are not fast enough to eliminate arc flash burns when a short circuit is accidentally made between conductors having a high electrical energy difference between them. The problem also may arise in high tension power supply systems such as those provided in large mobile structures such as draglines.

The present invention aims to provide arc flash protection apparatus which alleviates the problem of arc flash in electrical systems. Other aims and advantages of the invention may become apparent from the following description. DISCLOSURE OF THE INVENTION

With the foregoing in view, the present invention in one aspect resides broadly in arc flash protection apparatus including : a power supply busbar in electrical communication with a power supply; a power delivery busbar spaced from the power supply busbar and in electrical communication with a power distribution system; and a plurality of fuses connected in parallel between the power supply busbar and the power distribution busbar.

Preferably, the fuses are provided in the form of high speed semiconductor fuses, such as ceramic coated semiconductor fuse elements and preferably, the fuses are substantially identical with one another. Preferably, the power supply busbars and the power distribution busbars are substantially identical with each other .

Preferably, the arc flash protection apparatus includes monitoring apparatus for monitoring the fuses whereby the activation of the flash protection apparatus (by blowing the fuses) can be signalled. For example, striker elements may be provided, one in physical contact with each fuse, each striker element being operatively associated with a limit switch and arranged to open or close the limit switch upon any or each fuse being blown. Preferably, the size of the busbars is selected to minimise impedance losses according to the electrical characteristics of the power supply to be conducted therethrough and the resistivity of the material from which the busbars are formed. Preferably, the busbars are formed substantially from copper and are formed as a rectangular prism. Preferably, the busbars for the phases are spaced from one another a distance sufficient to minimise derating of the busbars due to the proximity effect between the phases . Preferably, the incoming power supply is connected intermediate the ends of the power supply busbar to balance the current distribution across the fuses. However, in some applications, it may be appropriate to connect the incoming power supply at or near to one end of the power supply busbar. Preferably, the outgoing power delivery is connected intermediate the ends of the power delivery busbar to balance the current distribution across the fuses. However, in some applications, it may be appropriate to connect the outgoing power delivery at or near to one end of the power delivery busbar. It will be appreciated that in order to attain optimum balance of the load across the fuses, it is necessary to have both the power supply and the power delivery connected to the respective busbars substantially centrally between the ends.

In another aspect, the present invention resides broadly in a method of substantially eliminating arc flash including: electrically connecting a power supply busbar to a power supply; mounting a power delivery busbar in spaced disposition from the power supply busbar; electrically connecting the power delivery busbar to a power distribution system; and electrically connecting the power supply busbar to the power delivery busbar by a plurality of fuses connected in parallel between the power supply busbar and the power distribution busbar.

Preferably, the fuses are provided in the form of high speed semiconductor fuses substantially identical with one another. Preferably, the power supply busbars and the power distribution busbars are substantially identical with each other. Preferably, the method further includes monitoring the fuses and signalling when the fuses are blown. It is also preferred that method includes mounting a striker element in physical contact with each fuse, associating a limit switch with each striker element and arranging each limit switch to open or close upon any or each fuse being blown.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood and put into practical effect, a preferred embodiment of the present invention will now described with reference to the following drawings, and wherein: Fig. 1 is an isometric view of arc flash protection apparatus according to the invention with outside walls removed to show internal details;

Fig. 2 is an isometric view of the arc flash protection apparatus of Fig. 1 with the outside walls in place;

Fig. 3 is a plan view, of the arc flash protection apparatus of Fig. 1;

Fig. 4 is a front elevation of the arc flash protection apparatus of Fig. 1;

Fig. 5 is an elevation of the right hand side of the arc flash protection apparatus of Fig. 1; and

Fig. 6 is an isometric view showing a typical installation of the arc flash protection apparatus of Figs. 1 to 5.

DETAILED DESCRIPTION OF THE DRAWINGS

The arc flash protection apparatus illustrated in the drawings is for a three phase power supply. The arc flash protection apparatus 10 shown in Figs. 1 and 3 to 5 includes three pairs of busbars comprising a set of incoming busbars 14 and a set of outgoing busbars 16. The apparatus is incorporated into a cabinet 11 shown in Fig. 2. Each set of busbars has three members, the incoming busbars being referred to as first phase, second phase and third phase incoming busbars 14a, 14b and 14c respectively. Likewise, the outgoing busbars are referred to as first phase, second phase and third phase outgoing busbars 16a, 16b and 16c respectively. The front of the arc flash protection apparatus is the side closer to the incoming busbars. A neutral busbar 16d is also provided in spaced relationship from the outgoing busbars, but does not have a corresponding busbar paired with it . The busbars are formed as rectangular prisms, elongate in form and mounted in an upright disposition. The busbars are plate-like in form, the first phase, second phase and third phase busbars being arranged spaced from one another in substantially parallel relationship. The incoming and outgoing busbars for each phase are also spaced from each other and substantially co-planar with each other. Three lower insulating mountings 17 are provided, each one supporting one of the incoming busbars and one of the outgoing busbar for one of the phases. The busbars pass through the lower insulating mountings and are mechanically joined to, but electrically isolated from, in their respective phase pairs by an insulating panel 27. The busbars are also retained in their positions by three upper insulating mountings 18. Each of the first, second a third phase busbar pairs are mounted to one of the upper insulating mountings. The neutral busbar has its own upper and lower insulating mountings 18d and 17d.

Four intermediate insulating mountings 19 are provided, two being arranged to engage with the edges of each of the incoming busbars intermediate the upper and lower insulating mountings and the other two being arranged to engage with the edges of each of the outgoing busbars intermediate the upper and lower insulating mountings. The insulating mountings are supported at substantially even spacing from one another and in opposing pairs by insulation mounting rails 15.

The upper insulating mountings are supported by a pair of upper insulating mounting rails 15a. The lower insulating mountings are supported by a pair of lower insulating mounting rails 15b. Each pair of intermediate insulating mountings is supported by a pair of intermediate insulating mounting rails 15c. The intermediate insulation mounting rails run front to back, supporting the intermediate insulating mountings across the incoming busbars towards the front of the cabinet and across the outgoing busbars towards the back of the cabinet. The upper and lower insulating mountings run front to back in the cabinet. The upper and lower insulation mounting rails run across the cabinet, one of each towards the front and the others towards the back of the cabinet.

The mounting rails are supported in their respective positions by fastening to a box construction panel (not shown) across the back of the cabinet and to each of two side panels 29 forming the outside of the cabinet. The cabinet is enclosed by a top panel 28, a rear panel 24 and a front door panel 25. An upper frame 22 provides additional support for the upper insulation mounting rails and the upper insulating mountings. A lower frame 23 provides additional support for the insulation panels.

Eight fuse elements shown typically at 12 are mounted to provide electrical connection between each phase pair of busbars. The fuse elements are arranged in pairs alongside one another, each pair being arranged between fuse monitoring elements shown typically at 21. The members of each pair of fuses are mounted on opposite sides of the busbars as seen more clearly in Fig. 4. Electrical connections are made to the busbars by cables shown typically at 13 connected to the insulation panels.

In use, arc flash protection apparatus may be physically mounted and electrically connected to a transformer 50 as illustrated in Fig. 6. Three phase power may be connected to the incoming busbars and outgoing power from the arc flash protection apparatus connected to the transformer. Arc flash protection apparatus according to the invention is suited to low tension power systems, such as systems operating between 690 Vac^" and 415 Vac.

In systems such as power supply systems for large mobile structures including draglines and the like where high tension power supplies are provided, arc flash remains a potential problem. Accordingly, arc flash protection apparatus according to the invention may be adapted to such installations by, for example, mounting the busbars in a horizontal attitude instead of the vertical attitude of that illustrated in the drawings. Such installations may also use flexible busbars or cables for connectors because the arc flash apparatus is required to be of sufficient mechanical robustness to withstand movement of the structure along with the arc flash apparatus installed therein. The rapidity with which the fuse elements blow upon overload is sufficient to substantially eliminate arc flash because downstream conductors are deprived of electrical potential before a substantial arc can form. It will be appreciated that where the power supply is provided in the form of a polyphase alternating current power supply, a power supply busbar, power delivery busbar and fuses electrically interposed therebetween are provided for each phase to constitute arc flash protection apparatus according to the invention.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in other forms and mechanical equivalents within the broad scope and ambit of the invention as herein set forth and defined by the following claim.

Claims

1. Arc flash protection apparatus including:

a power supply busbar in electrical communication with a power supply; a power delivery busbar spaced from the power supply busbar and in electrical communication with a power distribution system; and a plurality of fuses connected in parallel between the power supply busbar and the power distribution busbar.

2. The arc flash protection apparatus according to Claim 1, wherein the fuses are provided in the form of high speed semiconductor fuses substantially identical with one another.

3. The arc flash protection apparatus according to Claim 2, wherein the power supply busbars and the power distribution busbars are substantially identical with each other.

4. The arc flash protection apparatus according to any one of the preceding claims and further including monitoring apparatus for monitoring the fuses whereby the activation of the flash protection apparatus (by blowing the fuses) may be signalled.

5. The arc flash protection apparatus according to Claim 4, wherein striker elements are provided, one in physical contact with each fuse, each striker element being operatively associated with a limit switch and arranged to open or close the limit switch upon any or each fuse being blown.

6. The arc flash protection apparatus according to any one of the preceding claims, wherein the size of the busbars is selected to minimise impedance losses according to the electrical characteristics of the power supply to be conducted therethrough and the resistivity of the material from which the busbars are formed .

7. The arc flash protection apparatus according to any one of the preceding claims, wherein the busbars for the phases are spaced from one another a distance sufficient to minimise derating of the busbars due to the proximity effect between the phases.

8. The arc flash protection apparatus according to any one of the preceding claims, wherein both the power supply and the power delivery connected to the respective busbars substantially centrally between the ends.

9. A method of substantially eliminating arc flash including: electrically connecting a power supply busbar to a power supply; mounting a power delivery busbar in spaced disposition from the power supply busbar; electrically connecting the power delivery busbar to a power distribution system; and electrically connecting the power supply busbar to the power delivery busbar by a plurality of fuses connected in parallel between the power supply busbar and the power distribution busbar .

10. The method according to Claim 9, including providing the fuses in the form of high speed semiconductor fuses substantially identical with one another.

11. The method according to Claim 10, wherein the power supply busbars and the power distribution busbars are substantially identical with each other.

12. The method according to any one of claims 9 to 11 and further including: monitoring the fuses; and signalling when the fuses are blown.

13. The method according to Claim 12, and further including: mounting a striker element in physical contact with each fuse; associating a limit switch with each striker element; and arranging each limit switch to open or close upon any or each fuse being blown.

14. The method according to any one of the claims 9 to 13, including selecting the size of the busbars to minimise impedance losses according to the electrical characteristics of the power supply to be conducted therethrough and the resistivity of the material from which the busbars are formed.

15. The method according to any one of the claims 9 to 14, including spacing the busbars for the phases from one another a distance sufficient to minimise derating of the busbars due to the proximity effect between the phases.

16. The method according to any one of claims 9 to 15, including connecting both the power supply and the power delivery connected to the respective Busbars substantially centrally between the ends .