WO2001023691A1

WO2001023691A1 - Cross arm formed of insulator

Info

Publication number: WO2001023691A1
Application number: PCT/AU2000/001176
Authority: WO
Inventors: Alfred George Baker; Kenneth Brett Boag
Original assignee: Electrical Moulded Components Pacific Pty. Ltd.
Priority date: 1999-09-28
Filing date: 2000-09-28
Publication date: 2001-04-05
Also published as: MY129056A; CA2385741C; AUPQ312699A0; CA2385741A1

Abstract

Electrical reticulation apparatus (1) replaces the traditional cross-arm and insulator(s) construction for overhead power lines. The apparatus (1) is a unitary casting or a composite structure and is insulating throughout. It includes arms (2 and 3) which are adapted to be orientated substantially horizontally when in use and an arm (4) which is adapted to be orientated substantially vertically when in use. A mounting means (11) is provided for mounting the apparatus (11) to a pole, tower or the like. The ends of the arms (2, 3 and 4) which are remote from the mounting means (11) are adapted for the retention of overhead conductors.

Description

TITLE : CROSS ARM FORMED OF INSULATOR

FIELD OF THE INVENTION:

The present invention relates to the reticulation of electrical power.

BACKGROUND OF THE INVENTION:

Above ground power distribution, with voltages ranging from 1 lkV to 72kV, involve multiple conductors attached to support structures at intervals up to 500 metres (but often much more frequently to suit delivery of power to consumers). Each support structure is generally made from timber, steel or concrete. These support structures must be high enough to clear normal traffic and vegetation.

Each support structure is fitted with at least one cross member, commonly referred to as a 'cross-arm'. The cross-arms in turn support insulators at specified spacings. Conductors are then attached to the insulators.

Power is normally distributed in a three-phase arrangement which involves three conductors travelling together to the destination. The structures involved for power transmission, at higher voltages up to 1 ,000 kN, are larger and more complex, but employ the same elements of support structure, cross member, insulator and conductor.

In the prior art, the insulators are attached to either steel or timber cross-arms. Traditionally the insulators have been ceramic. Ceramic insulators have a number of disadvantages. For example, they cannot be cast in asymmetrical shapes. Porcelain insulators also have to be assembled from multiple components with steel joining sections. Ceramic insulators also have the disadvantage that the difference in the thermal coefficients of expansion between the steel sections and the ceramic insulating material, together with the brittleness ofthe ceramic, means that failure by fracture ofthe ceramic is prevalent.

The traditional cross-arms have been of either timber, or more recently, steel. Both timber and steel cross-arms have disadvantages.

In the case of timber cross-arms:-

• The use of timber is a waste of natural resources. This is particularly so as the majority of cross-arms that are cut are found to be unsuitable by the time that they are required for service due to the natural flaws that occur in timber.

• Timber rots in time and unless pre-treated and/or selected from the most hardy variety, the safe service life can be as short as two years. This problem is even worse in tropical areas.

Timber does not effectively contribute, at distribution voltages, to the insulative capacity of the configuration. This worsens as the timber ages and absorbs moisture and airborne pollutants. • In electrical storms, the timber can actually ignite and cause disruption to power supply.

• While not as heavy as steel cross-arms, timber cross-arms are still comparatively heavy and are difficult to replace.

In the case of steel cross-arms:-

• The steel cross-arm is a conductor and any breakdown in the insulator causes an immediate short-circuit to earth or to the adjacent conductor, resulting in interruption to power supply.

• The weight ofthe steel cross-arm is most difficult to handle.

• Unless they are hot dip galvanised, steel cross-arms will corrode quickly, particularly in industrial and salt spray environments.

• Lightning strikes will cause an arc to form between the conductor and the steel cross-arm and/or the adjacent conductor.

The following disadvantages apply to both timber and steel cross-arms.-

• Insulators are attached to the cross-arm by means of a variety of sometimes complex steel plates, bolts, nuts, washers or the like that require a linesperson to fit as many as twelve components to attach one insulator. The linesperson will need to fit as three such insulators, and fit the cross-arm itself.

• Replacement of cross-arms and insulators to existing structures is particularly hazardous, due to weight, complexity and conductivity.

The present invention accordingly aims to provide electrical reticulation apparatus which does not require the attachment of insulators to cross-arms. The present invention also aims to provide electrical reticulation apparatus which does not use timber or steel cross arms.

SUMMARY OF THE INVENTION:

The present invention accordingly provides electrical reticulation apparatus for use in an electrical reticulation system which includes poles, towers or the like for the support of overhead conductors, the reticulation apparatus including an insulating support member:-

which is attachable to a pole, tower or the like; and

which is integral with at least one attachment means for the attachment of an overhead conductor.

PREFERRED FEATURES OF THE INVENTION:

It is further preferred that the reticulation apparatus includes means for mounting the support member to the pole, tower or the like.

It is further preferred that each attachment means be provided integrally with one end of an arm, and that the other end of the arm be provided integrally with the means for mounting the support member to the pole, tower or the like.

It is preferred that the reticulation apparatus include at least two such arms. It is especially preferred that these two arms extend co-linearly.

It is preferred that the reticulation apparatus include a third arm, which is orientated to extend in a direction mid-way between the other two arms.

It is preferred that the reticulation apparatus include a socket for the reception ofthe top of a pole.

It is preferred that there be at least one shed provided on each arm, between the mounting means and the means for mounting the support member to the pole, tower or the like.

It is preferred that means for the temporary mounting of a block and tackle or the like be provided on at least one arm between the mounting means and the sheds.

It is preferred that the apparatus be a casting.

It is further preferred that the apparatus be cast in an epoxy, phenolic, polyester, vinyl ester or polyurethane resin. It is especially preferred that the apparatus be cast in cyclo- aliphatic epoxy.

It is especially preferred that the apparatus be a composite structure which includes reinforcing which is within a casting.

It is preferred that the apparatus includes a guard to guard against access by possums or like animals, which possum guard is void in its interior and which includes a generally frustro-conical surface which flares outwardly.

In order that the invention may be more readily understood, preferred embodiments of it will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is a side elevational view of electrical reticulation apparatus according to one embodiment ofthe present invention.

Figure 2 is a side elevational view, showing some hidden detail, of electrical reticulation apparatus according to another embodiment ofthe present invention.

Figure 3 is an elevational view ofthe embodiment of figure 2, showing it when mounted on a pole.

Figure 4 is an elevational view, partly in section, of a modification of a portion of the embodiments of figures 1 and 3.

Figure 5 is an elevational view of another embodiment ofthe present invention.

Figure 6 is a plan view ofthe embodiment of figure 5, showing it when mounted on a pole.

In order that the invention may be more readily understood, preferred embodiments of it will be described with reference to the drawing.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION:

Electrical reticulation apparatus according to one embodiment ofthe present invention, and which is adapted for use in a three-phase power supply is indicated generally at 1 in figure 1.

The apparatus 1 includes three arms 2, 3 and 4 which are provided integrally. The arms 2 and 3 are configured so that they can extend generally horizontally when the apparatus 1 is mounted on a pole, tower or the like. The arm 4 is provided centrally between arms 2 and 3 and is configured to extend generally vertically when the apparatus 1 is mounted on a pole, tower or the like.

The apparatus 1 includes means 11 for mounting the apparatus to the pole, tower or the like. In the present embodiment of the invention, the mounting means 11 includes a socket for the reception ofthe top of a pole. Alternative embodiments ofthe invention which are not illustrated use other suitable mounting means.

The ends of the arms 2, 3 and 4 which are remote from the mounting means 11 carry mountings 6, 7 and 8 respectively. The mountings 6, 7 and 8 are similar to the mountings which are used for retention of overhead conductors by traditional ceramic insulators.

Sheds 12, 13 and 14 are provided on the arms 2, 3 and 4 respectively and serve the same functions as do the sheds on a traditional ceramic insulator. There are additional sheds 15 in the transitional region between the mounting means 11 and the arm 4 to provide additional protective creepage from the conductors to the pole or tower.

When mounting conductors on a cross-arm or the like, workers currently may temporarily attach a block and tackle or the like to the cross-arm to lift cable up to the cross-arm. It is accordingly preferred that a support member 1 according to the present invention further include a mounting means (which is not illustrated in the drawings) integrally with either or both ofthe arms (2 and 3) at a position between the mounting means (6 and 7) and the sheds (12 and 13) for temporarily mounting a block and tackle or the like.

As will be appreciated, the one-piece structure of apparatus 1 does not require any pre- assembly before it mounted on a pole or tower or before the overhead conductors are attached to it.

The lengths ofthe arms 2 and 3 can be varied to achieve the preferred or specified clear air distance which is required between conductors.

The embodiment ofthe invention which is shown in figures 2 and 3 is the same as the embodiment of figure 1 except that it includes a possum guard 21. The possum guard 21 includes a frustro-conical surface which flares outwardly from the apparatus. The interior of the possum-guard 21 is void, and surrounds the end of the supporting pole or the like 22 to prevent possums from climbing from the pole 22 onto the apparatus.

The embodiment ofthe invention which is shown in figure 4 shows a preferred form or the embodiments of figures 1 to 3. This embodiment differs from figures 1 to 3 in that the sheds 24 are inclined at an angle away from the horizontal. This orientation ofthe sheds encourages the run-off of pollution from the surfaces of the sheds, particularly during rain storms.

The embodiments ofthe invention which are shown in figures 5 and 6 are adapted for use in a two-phase power supply have only two arms such as arms 2 and 3. It is preferred that these arms are mounted horizontally opposed.

Figures 5 and 6 also illustrate a method of mounting the apparatus to the pole 28. It is to be understood that this method of mounting is also suitable for three-phase apparatus, and is not limited to the two-phase form of the invention which is illustrated in these figures.

In the embodiment of figures 5 and 6, the apparatus 1 includes bolt holes 31 and 32 extending through it for reception of mounting hardware 26 and 27. The mounting hardware 26 and 27 is used to mount the apparatus 1 to a pole or the like 28.

In apparatus according to the present invention, the creepage (which is the distance from conductor to earth) is vastly higher than in traditional configurations. This improves protection of the reticulation system from the effects of lightning, pollution and salt spray. Also, protected creepage (the interruption of a direct line of potential arcing between conductor and earth or between conductors) is provided in an optimal manner. As there are no metal components attaching an insulator to a cross-arm, assembly labour is greatly reduced compared with the prior art. The weight ofthe apparatus according to the present invention is also significantly less than the weight of a comparable assembly of a steel or timber cross-arm with attached insulators. The apparatus of the present invention is also strong in every direction as it is free from flaws that are common in timber.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

1. Electrical reticulation apparatus for use in an electrical reticulation system which includes poles, towers or the like for the support of overhead conductors, the reticulation apparatus including an insulating support member:-

which is attachable to a pole, tower or the like; and

2. Electrical reticulation apparatus as claimed in claim 1, further including means for mounting the support member to the pole, tower or the like.

3. Electrical reticulation apparatus as claimed in claim 1 or claim 2, and further including at least one arm, wherein:-

each attachment means is provided integrally with one end of an arm; and

the other end of the arm is provided integrally with the means for mounting the support member to the pole, tower or the like.

4. Reticulation apparatus as claimed in claim 3, and including at least two such arms.

5. Reticulation apparatus as claimed in claim 4, wherein two ofthe arms extend co- linearly.

6. Reticulation apparatus as claimed in claim 4 or claim 5 and which has three such arms, wherein the third arm is orientated to extend in a direction mid-way between the other two arms.

7. Reticulation apparatus as claimed in any one ofthe preceding claims wherein the means for mounting the apparatus to a pole or the like includes a socket for the reception ofthe top of a pole.

8. Reticulation apparatus as claimed in any one of claims 3 to 8, further including at least one shed provided on each arm, between the mounting means and the means for mounting the support member to the pole, tower or the like.

9. Reticulation apparatus as claimed in any one of claims 3 to 9, further including means for the temporary mounting of a block and tackle or the like.

10. Reticulation means as claimed in claim 10, wherein the means for temporarily mounting of a block and tackle is provided on at least one arm between the mounting means and the sheds.

11. Reticulation apparatus as claimed in any one of the preceding claims which is fabricated in the form of a casting .

12. Reticulation apparatus as claimed in claim 12, wherein the reticulation apparatus is a composite structure which includes reinforcing within the casting.

13. Reticulation apparatus as claimed in claim 12 or claim 13, wherein the casting is cast in an epoxy, phenolic, polyester, vinyl ester or polyurethane resin.

14. Reticulation apparatus as claimed in claim 14 wherein the casting is cast in cyclo- aliphatic epoxy.

15. Reticulation apparatus as claimed in any one of the preceding claims, further including a guard to guard against access by possums or like animals, which possum guard:-

includes a generally frustro-conical surface which flares outwardly; and

is void in its interior.

16. Reticulation apparatus as claimed in any one of the preceding claims, substantially as described with reference to:-

Figure 1 ofthe drawings;

Figure 2 of the drawings;

Figures 5 and 6 ofthe drawings;

Figures 1 and 4 ofthe drawings; or

Figures 2 and 4 ofthe drawings.

17. Reticulation apparatus substantially as herein described with reference to:-

Figure 1 ofthe drawings;

Figure 2 ofthe drawings;

Figures 5 and 6 ofthe drawings;

Figures 1 and 4 ofthe drawings; or

Figures 2 and 4 ofthe drawings.