IE20020600A1 - An improved modular busbar - Google Patents

Abstract

An electrical busbar (2) comprises a fixed three-dimensional framework (21) having a plurality of support members (21a) to (21c), support insulators (23a) and (23b) and pairs of conducting bars (22). The electrical current carried by the busbar (2) is split into three current phases and a neutral phase. Two pairs of conducting bars (22a) carry each of the four phases. The conducting bars (22) are arranged within the fixed three-dimensional framework to provide an effective cancellation of the magnetic fields caused by individual phase bars. In addition the heating effect and mechanical stresses caused during fault conditions are reduced. The busbar (2) can carry a number of different current ratings without adjusting the size of the three dimensional framework (21), by replacing the size of the conductor bars (22). <Figure 2>

Description

AN IMPROVED MODULAR BUSBAR An electrical busbar (2) comprises a fixed three dimensional framework (21) having a plurality of support members (21a) to (21c), support insulators (23a) and (23b) and pairs of conducting bars (22). The electrical current carried by the busbar (2) is split into three current phases and a neutral phase. Two pairs of conducting bars (22a) carry each of the four phases. The conducting bars (22) are arranged within the fixed three dimensional framework to provide an effective cancellation of the magnetic fields caused by individual phase bars. In addition the heating effect and mechanical stresses caused during fault conditions are reduced. The busbar (2) can carry a number of different current ratings without adjusting the size of the three dimensional framework (21), by replacing the size of the conductor bars (22). of a busbar enabling a higher rating to be achieved.

The terms “bus” and “busbar” are industrial terms used within the electrical sector. The term “bus” is used to describe a junction of circuits, generally the junction has a small number of inputs and a larger number of outputs. A “busbar” is used to describe the form the bus takes, which is a bar or bars of conducting material. A busbar is best described as the main current carrying conductor within an electrical/switchgear enclosure. The conductor is usually manufactured from a high conductive material such as copper or aluminum and is secured in place with insulated support fixings. A busbar is used to carry current of a particular rating, which can vary from 100 amps to 10,000 amps. This is a simple cost effective way of feeding current throughout a switchgear panel. Within the switchgear enclosure all electrical components are connected across the length of the busbar. All types of busbars incorporated within low voltage electrical switchgear must be certified to BS EN 60439 standards.

There are problems associated with conventional busbars. Generally as the current rating carried by a busbar increases, the frame size of the busbar must also increase to allow for the extra components required. Subsequently as the frame size increases the switchgear enclosure size must also increase and can often be up to 1800mm deep. This can lead to installation difficulties and higher costs.

It is essential that the conductor carrying the current within a busbar be isolated away from the structure of the switchgear enclosure. Conventional systems use support insulators and steel brackets. Whilst this addresses the problem of isolating the conductor, improvements can be made. Also conventional busbars do not spread the induced magnetic current instead a higher magnetic field is concentrated in a particular area. To overcome this, some conventional busbars require a higher quantity of copper to achieve the desired current rating, again resulting in higher costs. t.

It is the object of the present invention to seek to alleviate the aforementioned problems.

The present invention provides a busbar comprising a fixed three dimensional framework having a plurality of support members, a plurality of support insulators engaged with the support members, and pairs of conducting bars engaged with the support insulators, wherein the support insulators comprise a middle support insulator for supporting the juxtaposed edges of upper and lower bars of each pair of conducting bars and movable upper and lower support insulators engagable with the other edges of the conducting bars, and the conducting bars being coated with an insulating material and having insulatable tap off points and being selectable from a range of different capacity bars depending on the current rating required.

Advantageously, the conducting bars are connectable at their ends by one or more joiner plates to like size conducting bars so as to provide elongated conductors, the joiner plates being insulatable.

The frame of the busbar comprises horizontal, vertical and transverse components. Ideally the components are formed from a suitable metallic and non-metallic material. It is preferable for the horizontal components to be paired and orientated such that each pair is equidistant. Ideally, the transverse components are situated at specific sites in the same plane and perpendicular to the horizontal components connecting each pair of horizontal components. The horizontal and transverse components comprise the base of the frame. It is preferable for . the. vertical members to be attached to the horizontal components at the same points of attachment as the transverse components such that the vertical components are protruding from the frame base in one direction only, perpendicular to the frame base. Ideally each vertical component should have a corresponding component on the opposite horizontal member. Whilst this is the preferred arrangement for a frame structure within the busbar, the present invention is not limited to this arrangement and any suitable frame structure can be used.

Preferably, the current carried by the present invention is split into three phases and a neutral phase, ideally two pairs of conducting bars carry each phase. Ideally, the conducting bars are composed of copper however any suitable conducting material can be used. In a preferred embodiment of the invention the pairs of conducting bars are positioned such that there is a fixed distance between the centres of phase pairs of the same type.

Preferably, the pairs of bars are positioned with the three phases and neutral phase interlaced between each other. For example, in a typical arrangement the first pair of neutral conducting bars are positioned at the first point on a support insulation bar. Positioned next to the first pair of neutral conducting bars are the first pair of phase conductor bars L1(R). The pairs of phase conductor bars carrying L2(S) and L3(T) are located at the third and fourth points on the support insulation bar. The sequence is repeated with the exception of the neutral conducting bar, thus at the fifth, sixth and seventh positions on the support insulation bar are the pairs of phase conducting bars carrying L1(R), L2(S) and L3(T) respectively. The final pair of neutral conducting bars are positioned at the eighth point on the support insulation bar. This enables a more effective cancellation of the magnetic fields caused by individual phase bars, reducing the heating effect and mechanical stresses caused during fault conditions.

With this design, each pair of conducting bars carry half of the busbar current rating (for example in a 4000 Amp system each pair carries 2000 (Amps each). This results in the magnetic field of each phase spreading out across the width of the panel. In this example, the quantity of copper used is reduced by up to 42% over conventional busbars. Optionally, the . conducting bar can be fully insulated. Ideally the bars are coated with an insulating material. For exemplary purposes the insulation material is an extruded epoxy resin with uniform thickness. Preferably the coating is extruded over the conducting bar using a method that will prevent the formation of air pockets between the conductor and the insulation. Ideally the insulation material is black in colour promoting heat dispersion. There are live points situated on the conducting bar, where the current is “tapped off’ for use elsewhere. There are also live points at the busbar joints; it is necessary to cover these points to insulate the conductor bar. Ideally this is done using shrouds designed to cover the specific type of live point. By way of example, the shroud covering the “tap-off” point is made from ABS plastic and is designed to suit all busbar sizes however any suitable covering can be used.

It is preferable for the conducting bars to be located along the length of the frame and held in position by insulated supports attached to the vertical components. Ideally the insulated supports are glass-reinforced supports which have high mechanical strength. This enables the conducting bar to be clamped into position by means of the support insulator alone without the necessity for additional steel brackets. For exemplary purposes only, one suitable material is GP03, many others will suggest themselves to the skilled person. Ideally there are two different types of support, there is an upper/lower support and a middle support. Preferably the upper/lower support has slots in which the conducting bars will rest on one surface only whilst the middle support will have slots on two opposing sides. Thus the lower support is attached to the vertical beam with condueting bars in the slotted positions. The middle support is then designed to serve a dual purpose of stabilising the lower conducting bars (first bar in a phase pair) in a vertical position and acting as a lower support for the upper conducting bars (second bar in a phase pair).

The busbar of the present invention is able to carry a number of different current ratings (for example 4000, 5000 and 6300 Amps). Ideally, the frame size of the busbar is not altered, enabling a person skilled in the art to adjust the components readily without changing the entire switchgear enclosure. Varying the current rating is easily achieved, by replacing the size of the conductor bar. Preferably the centre of the busbar is held, at. a calculated, datum in the horizontal plane, the middle support remains at this datum plane, as the conductor bar changes size the upper and lower supports spread outward from the datum line and the height of the transverse bracket is lowered.

The invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a perspective view of the complete assembly of a switchgear enclosure; Figure 2 is a perspective view of the lower half of a switchgear enclosure, showing a first embodiment of a busbar; Figure 3 is a plan view of the busbar of Figure 2; Figure 4 is an end view of the busbar of Figure 2; Figure 5 is a side view of the busbar of Figure 2; Figure 6 is an exploded perspective view of a busbar joint assembly; Figure 7a is an end view of a second embodiment of a busbar; Figure 7b is an end view of a third embodiment of a busbar; Figure 7c is an end view of a fourth embodiment of a busbar; Figure 7d is an end view of a fifth embodiment of a busbar; Figure 7e is an end view of a sixth embodiment of a busbar; Figure 7f is an end view of a seventh embodiment of a busbar; Figure 8 is a perspective view of a upper/lower support in a busbar; Figure 9 is a perspective view of a mid support in a busbar; Figure 10a is a perspective outer view of a split cover; Figure 10b is a perspective inner view of a split cover; Figure 11 a is a perspective inner view from a first end of a busbar shroud; Figure 1 lb is a perspective inner view from a second end of a busbar shroud; Figure 1 lc is perspective outer view of a busbar shroud; and Figure 12 is a perspective view of the transverse support bracket used in a busbar.

Referring to the drawings and initially to Figure 1, there is shown a typical complete assembly of a switchgear enclosure indicated generally by the reference numeral 1. There is an area of the side panel cut away for the purpose of visualising the position of the busbar 2 within the switchgear enclosure 1.

Figure 2 shows a perspective view of the busbar 2. In this first embodiment there is a frame 21 comprising a pair of horizontal beams 21a, a plurality of transverse support brackets 21b and a plurality of vertical columns 21c.The horizontal beams 21a are orientated so that they are parallel to each other. The transverse support brackets 21b are strategically positioned to support and connect the horizontal beams 21a. The vertical columns 21c are attached to the horizontal beams 21a at the same point as the transverse support brackets 21b so that the vertical columns 21c are situated in pairs directly opposite one another on opposing, horizontal beams 21a. The vertical columns 21c protrude from the horizontal beams 21a in one direction only, defining the perimeter of the frame structure 21. The transverse support bracket 21b can be altered in size, by altering the dimensions of the vertical plate 60.

The busbar 2 carries three current phases and a neutral current phase along conducting bars 22. In this preferred embodiment the conducting material used is copper, however, the invention is not limited to this material, any other suitable conducting material can be used. There are eight pairs (22g and 22h being a first conductor bar in a pair and a second conductor bar in a pair respectively) of conducting bars 22 positioned along the length of the frame 21. Two pairs of conducting bars carry each phase of current. This enables each pair of conducting bars to carry half of the busbar current rating; this in turn allows the magnetic field of each phase to disperse across the width of the assembly.

Each pair of conducting bars carry either one of three different current phases or a neutral phase. The three phases and neutral phase are interlaced between one another displacing the phases such that the phases are in sequence (as can be seen in Figure 4, where N 22d is a neutral phase, R 22a is a first current phase, S 22b is a second current phase and T is a third current phase). Displacement of the phases enables a more effective cancellation of the magnetic fields caused by individual phase bars. Attached to the vertical columns 21c are specially designed support insulators 23a and 23b which are used to assist the positioning of the conducting bar pairs 22g and 22h respectively.

There are “tap off’ points (not shown) for each pair of conducting bars 22 of the same phase. Each “tap off’ point is connected to a connecting copper kit 24, which facilitates the removal of current at the “tap-off’ point. Specially designed shrouds cover the live connections between the conducting bars 22, the “tap off’ points and the copper connecting kit 24 (shroud 25) and the busbar joints (shroud 26). For clarity the “tap off’ shrouds 25 have been omitted from all but one of the “tap off’ points.

Fault level testing is carried out on busbars to test the overall mechanical strength to test both the system and it’s fixings. Simulating a short circuit condition carries out the testing. Testing on the 4000amp, 5000amp and 6300amp embodiments have shown that a fault level of 100k for 1 second was achieved. This test also incorporated a circuit breaker connecting kit (not shown) which would be positioned on the copper connecting kit 24 at the point indicated 24a.

Figure 3 is a plan view of the busbar of Figure 2. The copper connecting kits 24 used to connect the “tap-off’ points of each phase pair are clearly shown. There are three current phases and neutral current phase carried by this embodiment 2 labelled L1(R) 22a, L2(S) 22b, L3 (T) 22c and Neutral (N) 22d. Each of these phase pairs are positioned so that there is a minimum distance 22e of 300mm between them (only the distance 22e between phase pair 22a is shown).

Figure 4 is an end,,view of the busbar of Figure 2. The strategic interlacing of the current phases 22a - 22d in this embodiment is seen.

Figure 5 is a side view of the busbar of Figure 2. The “tap-off’ points 27 which are connected to the copper connecting kit 24 for taking current from the conducting bar 22, are shown.

Figure 6 is an exploded perspective view of the busbar joint assembly. The conducting material is fully insulated. The copper conducting bar 22 is coated with a layer of insulation 22f. A black epoxy resin plastic coating is extruded over the copper bars 22 resulting in a coating with uniform thickness of 1,6mm. The extrusion process prevents the formation of air pockets between the conductor and the insulation material. The insulation material is designed to uniformally remove heat from the conducting bars 22, thus avoiding hotspots. Whilst the insulation material is an epoxy resin, this material meets particular required specifications in order to meet the insulation properties and to keep within the working temperature limits of the switchgear enclosure. There are other suitable insulation materials known to those skilled in the art. ..

Joining conducting bars 22 together via conductor joiner plates 26c elongates the copper conducting bar 22. The conductor joiner plates 26c are positioned on both sides of the conductor bars 22 at pre-elongated sites 28. The conductor joiner plates 26c are secured in position using bolts 26a, washers 26b and nuts 26d. A specially designed shroud known as a split cover 26 is used to cover the exposed conductor joiner plates 26c, thus insulating the live connection point. In this preferred embodiment a clip on split cover 26 is used. Any suitable cover can be used for example, a specially moulded shroud with quick release clips.

Figures 7a - 7f illustrate the different arrangements of conductor bars used to carry different current ratings on different embodiments of the busbar. The width of the busbar for each embodiment is the same regardless of the current rating.

The centre of the busbar is held at, a calculated datum in the horizontal plane, the middle support insulator 23b in all cases remains at this datum plane. In order to achieve different current ratings, the size of the conductor material alters and the upper and lower support insulators 23 a spread outwards from the datum plane. The height of the support bracket 21b is the only component part, which is altered to accommodate an increase in the current rating. This is done by changing the dimensions of the vertical plate 60. As the current rating decreases in figures 7a to 7f the height of the vertical plate 60 in the transverse support bracket 21b is increased 60a to 60f. Careful calculations are done to determine the required height of the vertical plate for each desired current rating. The following is a list of the Figures 7a 7e, the corresponding current rating for each figure and the dimensions of the conductor material used to carry each phase of the current at a particular rating.

Figure Nominal Current Rating Maximum Current Rating Quantity and Dimensions 7a 6300A 8000A (No. x Height x Width) 4 x 120mm x 10mm Copper 7b 5000A 6300A 4 x 100mm x 10mm Copper 7c 4000A 5000A 4 x 80mm x 10mm Copper 7d 4500A 2 x 100mm x 10mm Copper and 7e 5500A 2 x 80mm x 10mm Copper 2 x 120mm x 10mm Copper and x 100mm x 10mm Copper Figures 7d and 7e are midway ratings and are achieved by mixing the sizes of the conductor bars. In these particular embodiments the larger sized conductor bar 22g is positioned beneath the datum plane 23b whilst the smaller sized bar 22h is situated above the datum plane 23b. The current ratings are not confined to these listed above. The current ratings for this system can vary from 3000A upwards, which is easily achieved by replacing the size of the conductor bar 22. Thus, the busbar is not limited, as broad variations of current ratings are available.

Figure 7f is- an end view of a seventh embodiment of a busbar with a 200% rating- neutral phase. An additional slot has been formed on the middle support insulator 23b and the upper/lower support insulators 23 a, to accommodate the extra bars of copper conducting material 22 required.

Figure 8 is a perspective view of the upper/lower support insulator 23a. When the support insulator 23 a is used in the lower position relative to the middle support insulator (Figure 7a, 23b) the support insulator 23 a is orientated such that the slots 30 are in the uppermost position. The situation is reversed for the support insulator 23 a when it is in the upper position relative to the middle support insulator (Figure 7a, 23b) then the support insulator 23a is orientated such that the slots 30 are in lowermost position. The copper conductor bars 22 are positioned in the slots 30. Supports traverse from the upper support insulator 23a, through the middle support insulator 23b (see Figure 7a) to the lower support insulator 23a at the points 31. There are two scribed lines 32 running the full length of the upper/lower support insulator 23a on the copper conductor bar slot 30 side of the support insulator 23a.

Figure 9 is a perspective view of the middle support insulator 23b used in a busbar. The copper conducting bars 22 are positioned in the slots 30. The supports between the upper/ lower support insulators 23a pass through the middle support insulator 23b at the points 31.

There are two scribed lines 32 running the full length of the middle support insulator 23b on the both copper conducting bar slot 30 sides. The scribed lines are positioned 10mm apart, both are 5mm apart from the centre of the part, enabling the busbar to be positioned during manufacturing such that a 10mm expansion gap is present at each joint.

Figures 10a and 10b are perspective diagrams of a front and rear view of the split cover shroud 26 used to insulate the exposed conductor joiner plates 26c (see Figure 6).

Figures 11a and lib are two different orientations of a perspective rear view of a “tap-off’ shroud 25. Figure 11c is a perspective front view of a “tap-off’shroud 25. The “tap-off’ ..shroud 25 is moulded from ABS plastic, however, any material suitable can be used. The shroud 25 is suitable for all busbar sizes and is held in position by quick release clips 40. The shroud 25 is readily adaptable if the size of the connecting copper kits varies. The membrane situated on the top and sides of the shroud 25 is easily cut to suit the required size.

Figure 12 is a perspective view of the transverse support bracket 21b. As the current ratings are varied for different applications, the height of the copper conducting bars 22 and the height of the vertical plate 60 is altered to accommodate the different lengths required.

It is to be understood that the invention is not limited to the specific details described herein which are given by way of example only and that various modifications and alterations are possible without departing from the scope of the invention.

Claims (16)

1. A busbar comprising a fixed three dimensional framework having a plurality of support members, a plurality of support insulators engaged with the support members, and pairs of 5 conducting bars engaged with the support insulators, wherein the support insulators comprise a middle support .insulator for supporting the juxtaposed edges of upper and lower bars of each pair of conducting bars and movable upper and lower support insulators engagable with the other edges of the conducting bars, the conducting bars being coated with an insulating material, having insulatable tap off points and being 10 selectable from a range of different capacity bars depending on the current rating required.

2. A busbar as claimed in Claim 1, in which the conducting bars are located along the length of the frame. 15

3. A busbar as claimed in Claim 1 or Claim 2, in which the pairs of conducting bars are connectable at their ends by one or more joiner plates to like size conducting bars so as to provide elongated conductors, the joiner plates being insulatable.

4. A busbar as claimed in any one of the preceding Claims, in which the current carried by 20 the pairs of conducting bars within the busbar is split into three current phases and a neutral phase with two pairs of conducting bars carrying each phase, wherein the pairs of conducting bars are positioned so that there is a fixed distance between the centres of same type phase pairs. 25

5. A busbar as claimed in Claim 4, in which the pairs of conducting bars are positioned with the three current phases and neutral phase interlaced between each other.

6. A busbar as claimed in Claim 4 or Claim 5, in which the pairs of conducting bars are positioned so that each outer pair of conducting bars carry the neutral phase with the pairs of conducting bars carrying the three current phases positioned intermediate the neutral phase pairs.

7. A busbar as claimed in Claim 6, in which the central current phase pairs are positioned so that a first, second and third pair of current phase conducting bars each carry one of the three current phases with a fourth,, fifth and sixth pair of current phase conducting bars also adapted to each carry one of the three current phase pairs.

8. A busbar as claimed in Claims 6 and 7, in which the three current phases carried by the first, second and third pairs of current phase conducting bars and subsequently the fourth, fifth and sixth pairs of current phase conducting bars are in sequence, wherein each current phase is carried by one of the first, second and third pairs of current phase conducting bars and the order in which the current phases are carried is repeated in the fourth, fifth and sixth pairs of current phase conducting bars respectively.

9. A busbar as claimed in any one of the preceding Claims, wherein the insulated support members are glass-reinforced.

10. A busbar as claimed in any one of the preceding Claims, in which the conducting bars are coated with an insulating material.

11. A busbar as claimed in Claim 10, wherein the insulation material is an extruded epoxy resin with uniform thickness.

12. A busbar as claimed in Claim 10 or Claim 11, in which the coating is extruded over the conducting bar without forming air pockets between the conductor and the insulation.

13. A busbar as claimed in any one of the preceding Claims, in which there are uninsulated live points situated on the conducting bar, where the current is “tapped off’ for use elsewhere.

14. A busbar as claimed in Claim 13, wherein any uninsulated live points that are not in use are covered by a shroud, wherein the shroud is a shaped piece of insulating material.

15. A busbar as claimed in anyone of the preceding claims, which can carry different current 5. Ratings without altering the size of the fixed three dimensional framework. , V'.

16. A busbar substantially in accordance with any of the embodiments as herein described with reference to and as shown in the accompanying drawings.