AU2011101542A4 - Arc flash protection apparatus - Google Patents

Abstract

-12 Arc flash protecti on 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 elecLrical 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 APPAFATUS FIELD OF INVENTION THIS INVENTION relates to arc flash protecLior apparatus. The invention has particular application to arc flash protection 5 apparatus for protecting againsL arc flash burns tc personnel working on polyphase, alter-nating current power supply systems. However, the invention may have application to other fields of use. BACKGROUND ART J 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 he 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 Lension power supply systems such as those provided in large mobile structures such as draglines. The presenL invention aims to provide arc flash protection 0 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 IhlVnITIObI With the toregoing in view, the present inventi on in one aspect resides broadly in arc flash protect on apparatus i including: a power supply busbar in electrical communication with a power supply; a power del very busbar spaced from the power supply busbar and in electrical communication wiLh the low tension side of a power distribution system; and a plurality of more than two fuses connected in parallel betwoon the power supply y 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 clements and nrefe.ralyh v b-P f1 sa arep subi1S L Lntially idrntical with one another. Preferably, the power supply busbars and the power distribution busbars are substantially identical with each other. Preferably, the arc flash protecLion apparatus includes monitoring apparatus for monitoring Lhe fuses whereby the activation of the tlash protection apparatus (by blowing the fuses) can be signalled. For example, striker clements may be provided, one in physical contact with each fuse, each striker element being operatively associated with a limit switch and -3 arranged to open or close the limit sw. t ch upon any or each fuse ceing blown. Preferably, the size of the busbars is selecLed to minimise impedance losses according to the el ectrical characteristics of the power supply Lo be conducted therethrough and the resitivity 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 minimize 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, iL 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 de] i very 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 Lo one end of the power delivery busbar. It will be appreciated that in order to attain optimum balance of the lead across the fuses, it is necessary to have both the power supply and the power delivery connecLed to the respective busbars substantially centrally between Lhe ends.

-4 In another aspect, the present invention resides broadly .i n a method of substantially eliminating arc flash including: elecLrically 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 the low tension side of a power distribution system; and electrically connecting the power supply busbar to the power delivery busbar by a plurality of more than two 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 suppclv busbars and the nower distributio-n 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 wiLh each striker element and arranging each lim.1t switch to open or close upon any or each fuse being blown.

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$RIEF DESCRIPTIOK or Emz DAWIINGS In order Lhat the invention may be more readily understood and pt- into practical effect, a preferred embodiment of the presenL invention will now described wiLh reference to the 5 following drawings, and wherein: Fig. 1 is an isometric view of arc flash protection apparaLus according to the invention wiLh outside walls removed Lo 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 protecLion 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 apparaLus of Fig. 1; and Fig. 6 is an isometric view showing a typical installation of the arc fiash protection apparatus of Figs. 1 to b. DETAILED DESCRIPTION OF THE DrAWINGS 3 'The arc flash protection apparatus illustrated in the drawings is for a three phase power supply. The aL flash protection apparatus 10 shown in Figs. I 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 -6 into a cabinet 11 shown in Fig. 2. Each set of husbars has L!ree members, the incoming busbars being referred to as first phase, second phase and third phase incoming bushars i4a, 14b and 14c respectively. Likewise, the outgoing busbars are referred to as 5 first phase, second phase and third phase out going busbars 16a, 161b and 16c respecLively. 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 dispositi on. The busbars are plate-like in form, the first phase, second phase and third phase husbars being arranged spaced from one another in substantially parallel relaLionship. The incoming and outgoing bubars for each phase are al1so 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 insul ating 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 oirs are mounted to one of the upper insulating mountings. The neutral busbar has its own upper and lower insulating mountings 16d and 17d.

-7 Four intermediate insulating mountings 19 are provided, twu being arranged to engage with Lhe edges of each of the incomingQ busbars intermediate the upper aid lower insulating mountings and tho other two being arranged Lo engage with the edges cf each of 5 the outgoing busbars intermediate the upper and lower insulaLing mountings. The insulaLing mountings are supported at substantially even spacing from one another and in opposing pairs by insulation mounting rails 15. The upper insulating mounLings 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 par of intermediate insulating mountings is supported by a pair of intermediate insulating mounting rails 15c. The intermediate insulation mounting rails run front to hack, supporting Lhe 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, 0 one of each towards the front and the others Luwards 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 5 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 provi des additional support for the insulaLion panels. Eight fuse elemen-Ls shown typical ly at 12 are mounted to provide electrical connection between each phase pair of busbars. 5 The fuse elements are arranged in pai rs alongside one another as shown typically at 20 in Fig. 5, 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 0 to the busbars by cables shown typically at 13 connected to the insulation panels. In use, arc flash proLection apparatus may be physically mounted and electrically connected to a transfurner 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 connecLed to the transformer. Arc flash protection apparatus according to the invention is suited to low tension power systems, such as systems operating beLween 690 Vac and 415 Vac. ) In systems such as power supply systems for large mobile structures including draglinco and the like where high tension power supplies are provided, arc flash remains a potential problem. Accordiingly, arc flash protection apparatus according to the invention may be adapted to such installations by, for example, mounLing the busbars in a horizontal attitude instead of tie vertical altitude of that i llustraLed in the drawings. Such -9 installations may also use flexible busbars or cables for connectors because the arc flash apparatus is reqiured to be of sufficient mechanical robustness to withstand movement of the structure al ong with the arc flash apparatus installed Lherein. 5 The rapidity with whi ch 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 t.hat where Lhe power supply is provided in the form of a polyphase alternaLing ) OULet power supply, a power supply busbar, power deliver-y blsbar and fuses electrically inLerposed therehetween are provided for each phase to constitute arc flash protection apparatus according to the invenLion. Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the in vent ion may be embodied in other terms and mechanical equivalents within the broad scope and ambit of Ulie invention as herein set forth and defined by the following claim.

Claims (4)

1. Arc flash protection apparatus including: a power supply busbar in electrical communication wiLh a power supply; a power delivery busbar spaced from the power supply busbar and :n e)ectrical communicaLion with the low tension side of a power distribution system; and a plurality of more than two fuses connected in parallel between the power supply busbar and the power distribution busbar.

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

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 Lhe 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. -1 1 S, The arc flash protection apparatus according t_ Claim ', wherein striker elements are. provided, one in physical contact wi-h each fuse, each striker element being operatively associated wiLh a limit switch and arranged to open or closc the limit switch upon any or each fuse being blown.