GB2225177A

GB2225177A - Bracket for a busbar

Info

Publication number: GB2225177A
Application number: GB8925536A
Authority: GB
Inventors: Peter Maurice Rowles
Original assignee: Barduct Ltd
Current assignee: Barduct Ltd
Priority date: 1986-04-08
Filing date: 1989-11-11
Publication date: 1990-05-23
Anticipated expiration: 2006-04-08
Also published as: GB2189070B; GB2225177B; GB8925536D0; GB8608536D0; GB2189070A

Abstract

A mounting bracket for a busbar comprises two substantially identical parts 21, 22, the bracket having first, opposing, parallel flanges 23 and a further four flanges 24, 25, 26, 27 all of which are parallel to one another and transverse to said first, opposing flanges, each said part carrying one of said first, opposing flanges and two of said further four flanges, at least some of the flanges being provided with means, for example fixing holes, to fix the bracket and thereby the busbar to a support, for example a wall. <IMAGE>

Description

ELECTRICAL CONDUCTOR This invention relates to an electrical conductor more particularly in the form of a busbar or a kit of busbar parts having bus bar lengths connectable together in end to end relationship.

Various designs of busbar are in operation and these may consist of trunking having an extruded aluminium alloy channel shaped housing defining a base and side walls and an interlocking top cover strip made of Noryl. One such form of busbar is in use by the Applicant firm, and Pour conductor lengths, for example of aluminium or copper extend side-by-side within the housing and these conductor lengths are generally of channel section. Ratings of 160A, 250A and 315A are achievable in this design with aluminium conductor length and ratings of 250A, 315A and 450A are achievable with copper. Plugin tapping boxes may be provided every so often along a length of trunking where tapping outlets from each conductor length are provided in the cover strip.It is known to provide busbars of a type having much higher current carrying capacities out such systems tend to be more cumbersome. more expensive and are necessarily utilised with fixed, ciamp-on tapping boxes. The busbars of this latter type are usually employed in a different environment (for example in office blocks or flats) to the first mentioned type which are more suitable for an industrial environment where possible tapping access is required at a considerable number of locations along the busbar length (usually tapping outlets are provided at six generally equidistantlv spaced locations for every three metres of busbar!.

A need has been recognised for a busbar (more particularly utilizable with plug-in tapping boxes andior where space is at a premium) which has a current carrying capacity of up to, or more than.

twice any of the aforementioned current carrying capacities. Of course, if twice the current carrying capacity~ 5 required hen two busbars could be provided but this would, in most cases, be generally inconvenient for several reasons. Firstiv, space is a ner important consideration and usually there will be restrictions in the amount or space available for the busbar trunking. Ductwork in which the trunking may have to run may be of standard dimensions and there simply may not be enough room to run parallel trunking.Additionally, to run a duplicate line of trunking may prove a costly exercise and be generally inconvenient and could also be inconvenient for use in some instances.

It is an object of the present invention to provide a busbar, or kit of busbar parts, in which the current carrying capacity of the design Is generally increased but in which the busbar or the busbar lengths of the kit is;are still of relatively compact form.

According to the present invention there is provided a busby comprising a channel-shaped housing carrying two layers of conduct+ lengths in parallel relationship.

Usually there will be eight conductor lengths. preferably of generally U-shaped channel section, provided in the housing with four of the conductors lengths being m one layer arranged in back-to-back reiationship with the other four conductor lengths provided in the second layer.

Usually, longitudinally spaced tapping outlets will be provided on opposed sides of the busbar to allow convenient connection of plug-in tapping boxes.

In one embodiment of the present invention the channel shaped housing is generally symmetrical about a transverse axis lying inbetween the two layers of conductor lengths. The housing may have integral longitudinal channel pockets each receiving an insulating sleeve, said conductor lengths being slidably received in associated sleeves. The housing may have an open top and open bottom closed off by resilient snap-it or interlocking fit cover strips. The housing itself may be generally H-shaped with the cross member of the H-shape lying in-between said layers of conductor lengths. The housing may have longitudinal side flanges and special mounting brackets may be provided which may be attached to these side flanges, for example by releasable nut and bolt fastenings.

The busbar may comprise a busbar length connectable to an exactly similar busbar length in end to end relationship therewith by means of conductor length connections comprising longitudinally reciprocable sleeves surrounding adjacent ends of two parallel (usually back to back) conductor lengths. The sleeves may be of closed loop section and may be fixed relative to the associated conductor lengths by, for example, screws. Where channel section conductor lengths are provided in back-to-back relationship as aforesaid, conductor lengths may be connectable end-to-end by a relative lateral movement of busbar lengths followed by a slide movement of the sleeves.The conductor lengths of one layer may be provided with bridging bars which are fixed relative thereto 'for example by a retaining spring), which bars extend some distance beyond the end of their associated conductor lengths, whilst other bars are slidably arranged in associated conductor lengths of the other layer and fixed relative to their associated sleeves. In this way, the sleeves may be movable to a retracted position in which the bridging bars of one conductor layer project beyond the conductor lengths whilst the bridging bars of the other layer are retracted within their associated conductor lengths. The projecting bridging bars may then be offered laterally to one layer of conductor lengths of an adjoining length and the sleeves slid into an extended position thereby carrying the slidable bars into the ends of the adjoining channel conductor lengths.Said bars fixed relative to their conductor lengths may be provided with limit stops to limit the movement of the sleeves in at least one longitudinal direction. It is conceivable that a converse connection arrangement might be provided where the conductor lengths themselves may be solid bars and the bridging bars themselves are channel shaped. Any convenient connection of conductor lengths n end-to-end relationship may be provided. If preferred, conductor bridging bars in each layer may be slidabie in their associated conductor lengths with their associated sleeves.

Further according to the present invention there Is provided a kit of parts comprising a plurality of busbar lengths each comprising a channel shaped housing carrying two layers of conductor lengths in parallel relationship, said busbar lengths having conductor length connections. The kit may comprise busbar corner connections and/or plug-in tapping boxes. The scope of the present invention also extends to a busbar system including a busbar and plug-in tapping boxes installed in situ, where the busbar is in accordance with the first- statement of invention.

Many other advantageous features will be evident from the following description and drawings.

An embodiment of a busbar, or a kit of busbar parts, in accordance with the present invention, will now be described, by way of example only, with reference to the accompanying simplified diagrammatic drawings in which: FIGURE 1 shows a side view of the busbar; FIGURE 2 shows a section through the busbar taken on line II of FIGURE 1; FIGURE 3 shows a detail top or front view of part of the busbar and conductor length onnections, .e. looking in the direction of arrow A in FIGURES 1 and 2, FIGURES 4 to 7 show details of a connection from one conductor length to another, and FIGURE 8 shows an isometric view of a bracket for attaching the busbar to a fixture, for example a wall.

FIGURE 1 shows a busbar 1 which is a standard busbar length of, for example 3mm connectable to other busbar lengths in end-to-end relationship (part of another busbar length is shown connected at the righthand end of FIGURE 1 and is represented in chain dotted 'ines; in FIGURE 3 this other busbar length is shown in solid lines). Plug-in tapping boxes (not shown) may be conveniently located in shown manner at longitudinally spaced tapping outlet locations T only one location of four tapping outlets shown in FIGURE 3).

Referring to FIGURES 1, 2 and 3, the busbar 1 has an aluminium alloy channel-shaped housing 2 carrying eight parallel conductor lengths 3 (only two conductor lengths 3 are shown in FIGURE 2 for ease of illustration), which lengths are themselves generally Ushaped of channel section and may be of aluminium or copper. The lengths 3 are arranged in two layers of four conductor lengths in back-to-back relationship.

The lower half of the housing 2 (as shown in FIGURE 2) is the mirror image of the upper half of the housing (i.e. symmetrical about transverse axis X-X) and eight integral longitudinal channel pocke 2a are provided for the individual reception of longitudinal Noy sleeves 4. The conductor lengths 3 are slidably received in associated sleeves 4 and the sleeves insulate the conductor S from the housing 2. As shown in FIGURE 3 the sleeves a have end pieces 4a extending beyond the length of housing 2 and these are colour coded to denote phase and neutral conductors.Noryl snap-fit nterlocking cover strip 6 closes off the open top of the housing 2 in a manner which should be generally self explanatory from FIGURES 2 and 3 and a similar cover strip 6' closes off the open bottom of the housing 2 in similar manner. The overall shape of the housing 2 could be described as providing two integral, generally U-shaped channels back-to-back, each U-shaped channel receiving four conductor lengths or the housing 2 could alternatively be referred to generally as an H-shaped channel member with the cross-member 2b of the H-shape lying in between the two layers of conductor lengths.Of course, other shapes or general confIgurations of housing are possible which will conveniently locate the two layers of conductor lengths 3, and the lengths themselves need not necessarily be channel-shaped.

The housing 2 has additIonal longitudinal side flanges 2c and metal brackets , are secured thereto, by releasable nut and bolt fastenings o, over the cover Strips 6 to prevent accidental dislodgement of the cover strips from the housing 2.

The provision of a housing 2 carrying two layers of 'conductor lengths 3 as aforedecribed does cause special problems in the end-toend connect on of one busbar length to another as well as to other busbar parts such as corner or angle fittings. In a prior art arrangement it was possible to join two busbar lengths together carrying one layer of conductor lengths by relative lateral movement (relative vertical movement when viewing FIGURE 2). In said arrangement one set of channel conductor lengths carries relatively short solid metal bars received in the connecting ends of the channels and extending longitudinally therefrom. The extending parts of the metal bars are all simultaneously introduced into the associated channel conductor lengths of the adjacent connecting busbar length on relative lateral movement of the lengths.Then, aluminium or copped connecting sleeves already surrounding associated conductor lengths 0 one set are slid into, and screwed down at, final connecting positions covering the adjacent ends of the adjoining conductor lengths.

In this way, this prior art arrangement caters for the connection of busbar lengths together where end to end connection by relative longitudinal movement thereof is severely restricted and it would seem that a viable arrangement would also preferably cater for connection of bus bar lengths where relative longitudinal movement thereof is restrict. For further details of this prior art arrangement reference is made to 'B' line busbars as described in publication No. 20i dated May 1985 of the Applicant firm.

Such a simple connection as this prior art arrangement is not possible with the busbar as already described in relation to FIGURES 1, 2 and 3 because the metal bars could only be Introduced in the channel conductor lengths 3 of one layer on said relative lateral movement and the problem of connecting the second layer of conductor lengths would still remain. Therefore, an Important part of the present Invention is the provision of suitable and advantageous busbar conductor length connectIons indicated generally by reference numeral 9 which will now be described more particularly with reference to FIGURES 1 and 3 to Each conductor length connection 9 has an aluminium alloy longitudinally reciprocable sleeve 10 surrounding the adjacent ends of two parallel conductor lengths 3, which are arranged back-to-back.

Therefore, as shown in FIGURE 3 four connection sleeves 10 are provided.

FIGURE 4 shows a view of a connection 9 which is an enlarged more detailed view of the right-hand end of the busbar 1 shown in FIGURE 1. FIGURE 5 is a longitudinal sectional view similar to FIGURE 4, FIGURE 5 is a cranked transverse sectional view taken on line VI-VI of FIGURE 4 and FIGURE 7 is a further view similar to FIGURE 4 but this time showing the sleeve 10 in a retracted position and indicatIng the manner of coupling of busbar lengths together.

Each sleeve 10 is of closed loop cross sectlon and may be fixed relative to the remainder of the busbar 1 when four screws are tigtened (by means of Allen keys - not shown). On slackening off the screws 11 the sleeve is movable longitudinally and the extent of movement or reciprocatIng stroke S is shown in FIGURE 1. Each sleeve 10 Is movable from a fully extended position as shown in FIGURES 1. 3, D 5 to a retracted position as shown In FIGURE 7. As shown in FIGURES 4 to r, in the upper one of the conductor lengths 3, a generally flat metal bridging (aluminium alloy or copper, bar 12 s located so that about half the length of the bar extends from the conductor 3. The bar 12 is fixed in the channel in a manner which should be evident from the drawings by means of a plate spring 13 located in a square hole 14 in the bar. A limit stop 15 is formed on the upper surface of the bar i2 to limit the longItudinal movement of the sleeve 10. Stop i5 could be of any convenient form.

A transverse V-shaped groove is also provided on the upper surface of the bar 12 which acts as a guide for positioning the bar 12 relative to the conductor 3 with the correct proportion of the bar extending therefrom.

In the lower one of the conductor lengths 3 a second metal bar 16 of similar dimensions to bar 12 is located therein. However, no spring is provided for securing the bar i6 in the associated channel conductor length 3 since the bar 16 is arranged to be slidable in, and relative to, said length 3 in unison with sleeve 10, by any suitable means. In this instance, bar 16 has a notch 16a which receives a screw 16b (see FIGURE 5) so that the bar is movable with sleeve 10 from the position shown in FIGURE 4 to the position as shown in FIGURE 7, where it does not extend longitudinally beyond the associated conductor length 3.

In the posItion shown in FIGURE 7 busbar lengths are coupled together via their conductor lengths 3, by a lateral movement L of one set of conductor lengths 3 relative to the other set of conåuct lengths 3. On such lateral movement L the metal bars 12 are locate in, and immediately bridge across the upper end to end conductor lengths 3, the lower bars 16 lying in a retracted position thereby offering no obstructIon to such lateral movement. Next the sleeves 10 are each Individually moved to the right (it is conceivable that the sleeves 10 may be interconnected and movable In unison) as shown by arrow R in FIGURE 7, thereby sliding the bars 16 therewith into the end placed conductor lengths 3.Finally, the screws 11 are thightened up (against the upper edge of each bar 12) to hold the sleeves 10 In place and firmly make the connections 9. The connections 9 may then be covered by an insulating cover (not shown). Horizontal bar 17 see FIGURE 6) is also provided on, and carried by, sleeve 10. This Is fixed in place by screws 18 :only one shown in FIGURES i and 7) In similar manner to bar 16.

FIGURE 8 shows a mounting bracket 20 which is of a neat two part design and which in itself may be individually patentably inventive. It is formed of two identical parts 21, 22 and may be positioned anywhere along the busbar 1 to hold the bus bar to a supporting fIxture. for example a wall, In a manner which should be generally self -evident. Each part 21, 22 has opposing, parallel flanges 23 and a further four flanges 24, 25, 26, 27 all of which are parallel to one another and transverse to flanges 23. Flanges 23. 2a.

26, 27 are provided with fixing holes H. 11 flanges 23 to 2, extend to.the same side of the main plane of the part 21. 22.

Flanges 26, 27 may be positioned as shown in FIGURE 8 to engage and sandwich therebetween the side flanges 2c of housing 2 (see FIGURE 2), with screws passing through the aligned holes H in flanges 26, 27 and through the flanges 2c. The parts 21, 22 are shaped to closely embrace the busbar trunking. Parts 21, 22 are fixed together by way of holes H'. The design of bracket 20 is such that different thicknesses of housing flanges 2c may possibly be accommodated.

Advantageously. the busbar 1 as aforedescribed may provide current carrying capacities of twice those previously achieved by tht space saving twin conductor length arrangement. Advantageously, th; neat connections 9 allow bus bar lengths to be connected together where relative longitudinal movement of the lengths is severely restricted.

.Additionally, other suitable busbar parts may be provided for example corner connections) which are utIlizable with the busbar lengths to facilitate instalment. The busbar ; may be installed in any suitable orientatIon and access to each set of four conductor lengths 3 will be needed (at least part way along the length) from opposed sides of the busbar via tapping outlet locatIons T and plug-in tapping boxes vino: shown). Advantageously, many standard components (e.g. the tapping boxes per se) can be used with the busbar as aforedescribed. It is possible that a design of busbar based on this general principle incorporating more than eight conductors in the same housing, for example twelve or sixteen, and,or more than two layers of conductors could be provided. The tapping outlet locations may be generally opposed or offset'from one another on either side of the trunking.

It is to be understood that the scope of the present invention Is not to be unduly limited by the choice of partIcular terminology and use of any particular term may extend to use of any equivalent or generic term where sensible. Individual features of apparatus, method or functIons relatIng thereto r partcu#ar combinatIons thereof may be Individually patentably Invent-Ve.

Claims

1. A busbar comprising a channel-shaped housing carrying two layers of conductor lengths in parallel relationship.

2. A busbar as claimed in Claim 1 comprising eight conductor lengths provided in the housing with four of the conductors lengths being in one layer arranged in back-to-back relationship with the other four conductor lengths provided in the second layer.

3. A busbar as claimed in Claim 1 or Claim 2 in which the conductor lengths are of generally U-shaped channel section.

4. A busbar as claimed in any one of the preceding claims in which longitudinally spaced tapping outlets are provided on opposed sides of the busbar to allow convenient connection of plug-in tapping boxes.

busbar as claimed in any one of the preceding claims in which the channel shaped housing Is generally symmetrical about a transverse axis lying in between the two layers of conductor lengths.

Ö. A busbar as claimed in any one of the preceding claims In which the housing has integral longitudinal channel pockets each receiving an insulating sleeve, said conductor lengths being slidably received in associated sleeves.

7. A busbar as claimed in any one of the preceding claims in which the housing has an open top and open bottom closed off by resilient snap-fit or interlocking fit cover strips.

8. A busbar as claimed In any one of the preceding claims in which the housing itself is generally H-shaped wit the cross member of the H-shape lying between said layers of conductor lengths.

-#. A busbar as claimed In any one of the preceding claims in which the housing has longitudinal side flanges.

10. A busbar as claimed in Claim 9 in which mounting brackets are provided which can be attached to these side flanges, for example by releasable nut and bolt fastenings.

11. A busbar as claimed in any one of the preceding claims which comprises a busbar length connectable to an exactly similar busbar length in end to end relationship therewith by means of conductor length connections comprising longitudinally reciprocable sleeves surrounding adjacent ends of two parallel conductor lengths.

12. A busbar as claimed in Claim 11 in which the sleeves are or closed loop section.

13. A busbar as claimed in Claim 11 in which the sleeves can be fixed relative to the associated conductor lengths by. for example, screws.

14. A busbar as claimed in any one of Claims 11 to 13 in which channel section conductor lengths are provided in back-to-back relationship and are connectable end-to-end by a relative lateral movement of busbar lengths followed by a sliding movement of the sleeves.

15. Abusbar as claimed in Claim 14 in which the conductor lengths of one layer are provided with bridging bars which are fixed relative thereto, which bars extend some distance beyond the end of their associated conductor lengths, whilst other bars are slidably arranged in associated conductor lengths of the other layer and fixed relative to their associated sleeves.

16. A busbar as 'claimed in Claim 15 In which said bars fixed relative to their conductor lengths are provided with limit stops to lImit the movement of the sleeves In at least one longitudinal direction.

17. A busbar as claimed in any one of Claims 11 to 13 in which the conductor lengths themselves are solid bars and comprising bridging bars which are channel shaped.

18. A busbar as claimed in Claim 14 or Claim 17 in which conductor bridging bars, or the bridging bars, in each layer are slidable in their associated conductor lengths with their associated sleeves.

19. A busbar substantially as herein described and illustrated with reference to FIGURES 1 to 7 of the accompanying drawings.

20. A busbar as claimed in any one of the preceding claims including a bracket substantially as herein described and illustrated with reference to FIGURE 8 of the accompanying drawings.

21. A busbar system including a busbar as claimed in any one of the preceding claims and plug-in tapping boxes installed in situ.

22. A kit of parts comprising a plurality of busbar lengths each comprising a channel shaped housing carrying two layers of conductor lengths In parallel relationship, said bus bar lengths having 'conductor length connections.

23. A kit of parts as claimed in Claim 22 comprising busbar corner connections and/or plug-in tapping boxes.

24. A mounting bracket for a busbar comprising two substantially identical parts, the bracket having first, opposing, parallel flanges and a further four flanges all of which are parallel to one another and transverse to said first, opposing flanges, each said part carrying one of said first, opposing flanges and two of said further four flanges, at least some of the flanges being provided with means, for example fixing holes, to fix the bracket and thereby the bus bar to a support. for example a wall.

25. A bracket as claimed in Claim 24 in which all said flanges extend to the same side of the main plane of the bracket.

Amendments to the claims have been filed as follows 1. A mounting bracket for a busbar comprising two substantially identical parts, the bracket having first, opposing, parallel flanges and a further four flanges all of which are parallel to one another and transverse to said first, opposing flanges, each said part carrying one of said first, opposing flanges and two of said further four flanges, at least some of the flanges being provided with means, for example fixing holes, to fix the bracket and thereby the busbar to a support, for example a wall.

2. A bracket as claimed in Claim 1 in which all said flanges extend to the same side of the main plane of the bracket.

3. A mounting bracket as claimed in Claim 1 or Claim 2 in which different thicknesses of busbar housing flanges can be accommodated.

4. A mounting bracket for a busbar, substantially as herein described and illustrated with reference to FIGURE 8 of the accompanying drawings.

5. A busbar, or kit of busbar parts, including one or more brackets as claimed in any one of the preceding claims.

6. A busbar, or kit of busbar parts, as claimed in Claim 5 in which side flanges of a busbar housing engage and are sandwiched between opposing pairs of said further four flanges, with screws passing through aligned holes in said pairs of bracket flanges and through the busbar housing flanges.

/. A busbar, or kit of busbar parts. as claimed in Claim 5 or Claim 6 in which said first, opposing flanges closely embrace the busbar housing.

8. A busbar, or kit of bushar parts. as claimed in any one of Claims 5 to 7 comprisillF a #hannel-shaped hotisin# rarrvitla two layers of conductor lengths in parallel relationship.

9. A busbar, or kit of busbar parts, as claimed in Claim 8 comprising eight conductor lengths provided in the housing with four of the conductors lengths being in one layer arranged in back-to-back relationship with the other four conductor lengths provided in the second layer.

10. A busbar, or kit-of busbar parts, as claimed in Claim 8 or Claim 9 in which the conductor lengths are of generally U-shaped channel section.

11. A busbar, or kit of busbar parts, as claimed in any one of Claims 8 to 10 in which longitudinally spaced tapping outlets are provided on opposed sides of the busbar to allow convenient connection of plug-in tapping boxes.

12. A busbar. or kit of busbar parts, as claimed in any one of Claims 8 to ll in which the channel shaped housing is generally symmetrical about a transverse axis lying in between the two layers of conductor lengths.

13. A busbar, or kit of busbar parts, as claimed in any one of Claims 8 to 12 in which the housing has integral longitudinal channel. pockets each receiving an insulating sleeve, said conductor lengths being slidably received in associated sleeves.

14. A busbar. or kit of busbar parts, as claimed in any one of Claims 8 to 13 in which the housing has an open top and open bottom closed off by resilient snap-fit or interlocking fit cover strips.

15. A busbar, or kit of bus bar parts, as claimed in any one of Claims 8 to lll in which the housing itself is generally lI-shaped with the cross member of the li-shape Lying between said layers of conductor lengths .

16. A busbar, or kit of busbar parts. as claimed in any one of Claims 5 to 15 in which the housing has two, opposed longitudinal side flanges.

17. A busbar, or kit of busbar parts, as claimed in Claim 16 in which a plurality of mounting brackets are provided as claimed in any one of Claims 1 to 4, which brackets can be attached to these side flanges, for example by releasable nut and bolt fastenings.

18. A busbar, or kit of busbar parts, as claimed in any one of Claims 5 to 17 which comprises a bushar length connectable to an exactly similar busbar length in end to end relationship therewith by means of conductor length connections comprising longitudinally reciprocable sleeves surrounding adjacent ends of two parallel conductor lengths.

19. A busbar, or kit of busbar parts, as claimed in Claim 18 in which the sleeves are of closed loop section.

20. A busbar, or kit of busbar parts, as claimed in Claim 19 in which the sleeves can be fixed relative to the associated conductor lengths by, for example, screws.

21. A busbar, or kit of busbar parts, as claimed in Claim 8 or any claim dependent therefrom in which channel section conductor lengths are provided in back-to-back relationship and are eonneetabl.e end-toend by a relative lateral movement of busbar lengths followed by a sliding movement of the sleeves.

22. A busbar, or kit of busbar parts, as claimed in Claim 21 in which the conductor lengths of one layer are provided with bridging bars which are fixed relative thereto, which bars extend some distance beyond the end of their associated conductor lengths, whilst other bars are slidably arranged in associated conductor 1 Pngths of the other layer and fixed relative to their associated sleeves.

23. A btisbar,. or kit of hushar parts, as .1 aimed in c'liiil 22 in which said bars fixed relative to their conductor lengths are provided with limit stops to limit the movement of the sleeves in at Yeast one longitudinal direction.

24. A busbar, or kit of busbar parts, as claimed in any one of Claims 18 to 20 in which the conductor lengths themselves are solid bars and comprising bridging bars which are channel shaped.

25. A busbar, or kit of busbar parts, as claimed in, Claim 21 or Claim 24 in which conductor bridging bars, or the bridging bars, in each layer are slidable in their associated conductor lengths with their associated sleeves.

26. A busbar system including a busbar, or kit or busbars, as claimed in any one of Claims 5 to 25 and plug-in tapping boxes installed in situ.

27. A kit of parts comprising a plurality of busbar lengths each comprising a channel shaped housing carrying two layers of conductor lengths in parallel relationship, said busbar lengths having conductor length connections. and comprising a plurality of mounting brackets as claimed in any one of Claims 1 to .

28. A kit of parts as claimed in Claim 27 comprising busbar corner connections and/or plug-in tapping boxes.