AU782978B2 - Electrical insulator - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

SEC

113 ame of Applicant: 'N 0' Actual Inventor(s): U) C- fa'- Oc- F'Il IL +CA mctrtc r t T.

Address for Service: ALFRED BAKER and BRETT BOAG SANDERCOCK COWIE 69 Robinson Street, DANDENONG VIC 3175 Invention Title: ELECTRICAL INSULATOR oooo Details of Associated Provisional Application(s): No(s): Australian Provisional Application No. PQ9426 Filed: 16 1h August, 2000.

The following statement is a full description of this invention, including the best method of performing it known to us: 2001 -0-16.A:\347eectricalicomplete pdl e TITLE: ELECTRICAL 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 kV 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 2001-08-16.A:346electrical completcwpd.I 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 kV, are larger and more complex, but employ the same elements of support structure, cross member, insulator and conductor.

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 steeljoining 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 of the ceramic, means that failure by fracture of the ceramic is prevalent.

Ceramic, porcelain and other prior art insulators also generally have a steel centre pin which attaches the insulator to the cross-arm.

The traditional cross-arms have been of either timber, or more recently, steel. Neither 25 timber (at distribution voltages) nor steel contribute to the insulative capacity of the configuration. Thus an insulation breakdown or flash-over to the centre pin of the insulator is effectively to earth.

•Embrittlement leads to cracks in ceramic and glass insulators. Cracks allow the ingress of water and with it live organisms. Failure due to freezing becomes possible.

2001-08-16,AA346lectrca compicie -v'pd.2 -3- SUMMARY OF THE INVENTION The present invention accordingly provides an electrical insulator for use in an electrical reticulation system which includes poles, towers, cross-arms or the like for the support of overhead conductors, the insulator including:an insulating body; and integral therewith, an insulating attachment for attachment of the insulator to a pole, tower, crossarm or the like.

PREFERRED FEATURES OF THE INVENTION It is preferred that the insulating body and the insulating attachment be provided integrally.

It is preferred that the insulator be a casting.

•go It is further preferred that the insulator be cast in an epoxy, phenolic, polyester, vinyl 20 ester or polyurethane resin.

It is preferred that the insulator be a composite structure which includes reinforcing which is within a casting. It is especially preferred that the reinforcing is itself a composite of materials. Suitable reinforcing materials include plastics and metals.

Such insulators are intended for 1 Ikv, 24kv and 66kv installation. The insulator body may be 250-600mm long and 90-200mm in diameter at the sheds. The average pin length is 180mm. The pin bore in a mount is standard. The mounts may vary in depth and accordingly the pin may vary likewise. The exposed end of the galvanised steel bolt is threaded and takes a nut.

2001-8-16,A:U46ccric alcirpltc.pd.3 -4- BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a side elevational view of an insulator according to one embodiment of the present invention.

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 An insulator which is adapted for use in a three-phase power supply is indicated generally at 1.

The insulator 1 includes a generally axially extending insulating body 2.

One end of the insulating body 2 carries an integral cable mounting 3 for the receipt of a cable. The cable mounting 3 is similar to the mountings which are used for retention of overhead conductors by traditional ceramic insulators.

20 The other end of the insulating body 2 carries an embedded circular rod which extends generally coaxially from the end of the insulating body 2. The end of the insulating mounting 4 remote from the body 2 carries a screw-thread 6 for the receipt of mounting •hardware.

The insulating body 2 carries sheds 7, 8 and 9 extending generally radially from it, and placed intermediate the cable mounting 3 and the insulating mounting 4. Sheds 7, 8 and 9 serve the same functions as do the sheds on a traditional ceramic insulator. The cable mounting 3 carries a cable fitting which encircles the mounting but is not shown because it is standard. 1.3kg of cycloaliphatic epoxy casting resin and 1.7kg of silonised silica flour are blended to a uniform mix. The mix is transferred to the injection chamber of a pressure gelation apparatus and brought to routine elevated temperature. Meanwhile a galvanised pin 180mm long is loaded into the casting jig so that the knurled portion will be embedded. The mix is injected into the casting cavity and allowed to cure for 2001-08-16.A:346cloctrca compicte wpcl 4 minutes. Air bubbles are expressed in known manner. The item is retrieved and transferred to an oven which supplies stress relief. This process and the conditions for its operation are in the literature.

In a second example some of the silica flow is substituted with nylon monofil fibres long. In a third example only nylon monofil strands are used as reinforcement.

We have found the advantages of the above embodiment to be:- 1. The one-piece structure does not require any pre-assembly before it is mounted on a pole, tower cross-arm or the like before the overhead conductors are attached to it.

2. Lesser weight makes installation easier.

3. Creepage (which is the distance from conductor to earth) is higher than in traditional insulators. This improves protection of the reticulation system from the effects of lightning, pollution and salt spray.

20 4. The flexibility of the resin gives reliable operation. Embrittlement is much less of a problem.

2001-08-16.A:\46cIectricalcomplcte wpd4

Claims (8)

1. An electrical insulator for use in an electrical reticulation system which includes poles, towers and cross arms for the support of overhead conductors, the insulator comprising a solid unitary cast body of polymeric resin having an integral conductor support at one end and an integral, partially embedded mounting pin of a composition different from that of the body, extending from the opposite end, and multiple sheds extending from the body between the mounting pin and the conductor support.

2. An electrical insulator as claimed in Claim 1, wherein the insulator is cast in an epoxy, phenolic, polyester, vinyl ester or polyurethane resin. o

3. An electrical insulator as claimed in Claim 2, wherein the cast material contains 15 particulate or strand reinforcement.

4. An electrical insulator as claimed in Claim 3, wherein the reinforcement is a 000...composite material. 20

5. An electrical insulator as claimed in any one of Claims 1-4, wherein the mounting pin is a metal pin or a composite rod, wherein the partially embedded end is surface treated to resist displacement.

6. A method of making an electrical insulator as claimed in Claim 1 comprising loading a mounting pin into a casting jig and forming the insulating body around one end of the mounting pin by pressure gelation of a reinforced polymer resin.

7. An electrical insulator when made by the process of Claim 6.

8. An electrical insulator substantially as herein described with reference and as illustrated in the accompanying drawings.

2005-0721 \S pecifications\elecca complete wpd,6 Dated this 2 1S" day of July, 2005. SANDERCOCK COWIE PATENT ATTORNEYS FOR wC)c0 Fcc Rc EemfbmubITee4NEf fec P*-bo' 2005-07- 2 1.ZA~pecfiionIeericcomptepd, 7