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Issue 68 Quarter Two - 2005 Volum e 13 - Number 2

Quarterly Review INMRINMRQuarterly Review

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Strmbeck. Insulators benefit from an efficient and cost-effective production process.

might at first glance seem astrange policy for a prominentmultinational such as ABB. Yet, asRoger Sundqvist, Plasts Managerof Marketing and Sales explains,

the decision to locate allproduction of hollow corecomposite insulatorsin Pite was actuallyquite a logical one giventhe plants uniquecapabilities.

The Plast organization,says Sundqvist, has beeninvolved for many years inmanufacturing pressurevessels as well as molded

Sundqvist. Now promoting insulator sales outside the ABB Group.

The reindeer country inthe far northern reachesof Sweden is not exactlythe type of place whereone might expect to finda supplier of strategiccomponents forHV networks.

However, tucked awayin Pite, a town locatedin a region near the ArcticCircle and where trees,rivers and lakes faroutnumber people, isABB Plast - a factorysupplying the hollowcore composite insulators

The process of ABBs entry into the business of producinghollow core composite insulators began long before the firstsuch insulator ever rolled off the production line in Pite.

ABB Corporate Research in

Sweden devoted several years ofdevelopment work during the mid1990s aimed at evaluating therelative electrical performance ofvarious silicone formulations aswell as reviewing alternativeinsulator production technologies.This work helped to clarify therequirements for what would beregarded as the ideal siliconematerial for the special productionprocess ultimately selected.

Then, in mid 1998, the first small-scale pilot plant for insulators was

established inLudvika, Sweden amidmuch internal fanfare(see INMR Vol. 6No. 3). At the plantsinaugural ceremonyin the Spring of thatyear, key personnelfrom all of ABBsnearby manufacturingcenters for HV

apparatus were invited to tour the

new facility. Management at thenew pilot plant used this opportunityto put forward their argumentsabout all the potential benefits ofreplacing externally-purchasedporcelain with the new, internally-produced composite insulators.

Plast had, by this time, in factalready started to play an importantrole in ABBs insulator business,being the sole supplier of thefiber-reinforced plastic (FRP)tubes used by the new Ludvikafacility.

Over the years, it became increasinglyapparent that adding the siliconehousing onto these tubes was a stepwhich might more efficiently beperformed at the same locationwhere the tubes were themselvesbeing manufactured.

Says R&D Manager Anders Strmbeck,Plast already had the expertisenecessary to manufacture the FRPtubes. All that we needed therefore

was to incorporate into our facility thespecial extrusion molding technologyused to apply the housing to the tube.The strategic decision was thereforemade to focus all of ABBs productionof insulators in Pite.

Generally-speaking, a productionfacility for hollow core compositeinsulators is much more compactthan would be required tomanufacture equivalent insulatorsmade of porcelain. This is becausethe manufacturing process involvesfar fewer steps - a fact which becomesvery evident when moving throughthe Pite plant.

Strmbeck explains that allincoming raw materials needed formanufacturing these insulators arechecked for conformity to Plastspecifications. In the past, thiswas already routine work for theproduction of the FRP tubes. Now,a similar procedure has also beenestablished for the high-temperaturevulcanized (HTV) silicone rubberused in the external housing.

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Producing highly-specializedinsulators in northern Sweden andat quite a distance from many ofthe manufacturing facilities whichutilize them in HV apparatus

and injected plastic componentsused in a variety of industries.Therefore, when ABB decidedto go into the large-scalemanufacturing of hollow compositeinsulators, it made sense for ourplant to be selected as the soleproduction center.

In point of fact, the process ofABBs entry into the business ofsupplying hollow core compositeinsulators actually began longbefore the first such unit ever rolledoff the production line in Pite.

To begin with (as reported in pastissues of INMR), scientists at

which are now finding increasingapplication on electrical networksworldwide. One of many productioncenters within the huge Swiss-Swedish multinational, this particularplant has actually been in existencesince the mid 1960s - well beforeAsea and Brown Boveri mergedto form ABB.

In this article, INMR ContributingEditor Dr. Claude de Tourreil,travels to visit what may well bethe worlds most northerly factoryin the field of HV engineeringand reports on this facilitysproducts as well as manufacturingtechnology.

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Remote Plant Plays Key Rolein ABB Insulator Business

Executives from other ABB companies in Ludvika examinenew composite insulator with obvious interest.

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ABB has been supplying composite insulators to the electrical utility industry for many years.Today, we deliver thousands of pieces annually to an expanded portfolio that includesapplications for high voltage breakers, instrument transformers, lightning arresters andbushings. Our patented helical extrusion method makes applying varying silicone rubber shed profiles on differing housing geometries l ess of an investment than other methods.

Composites insulators of today are a proven technology with well-established manufacturingpractices ensurin g reliable service over the life of ones electrica l apparatus. C ompositeinsulators with silicone rubber sheds offer several advantages over traditional ceramics being

self-clea ning, reduced incidence of flashover, low weight and non-brittl e construction. The self-cleanin g property of

silicone remains over its lifetime reducing incidence of fla shover due to airborne contaminants. Their lig htweightand non-brittle construction makes handling and transportation easier and reduces incidence of an outage due toan earthquake. In addition,their non-brittle construction can reduce personnel injury and property damage due toelectrical apparatus failure.

The inherent advantages of composites improve insulator performance over varying mechanical and environmentalconditions. The hollow composite tube provides for a strong but light construction that remains fl exible and able tosurvive under varying mechanical loads. The silicone rubber sheds ensure reliable performa nce in harsh environmentalconditions. Together, the hollow composite with sili cone rubber sheds is the best solution for todays appl ications.

We took our lessonsfrom nature

Read more about hollow composite insulators underwww.abb.com/insulation2005 ABB

Hollow Composite Insulators by ABB

Winding machine for 4 meter tubes.Mandrels for manufacturing FRP tubes(in background stands 7 meter long winding machine)

According to Strmbeck, a decisionwas made to work with two differentsilicone suppliers so as to bestensure an uninterrupted supplyof this key strategic and what hesays is a relatively costly material.

The Pite plant is set-up such thatthere are two separate windingstations to produce the FRPtubes which form the core ofeach insulator. One station cansimultaneously accommodate two4 meter-long steel mandrels whilea second winding machine canproduce tubes of up to 7 meters

in length. The parameters of themanufacturing process for eachtube can be adjusted so as to obtainexactly the mechanical performancerequired from each insulator inits final application.

This is accomplished mainly byselecting the correct angle forwinding onto the mandrel theglass fibers which have beenpre-impregnated with resin.The thickness of the tube wallalso influences its final mechanicalstrength.

After the impregnated glass fibershave been wound onto the mandrel,the entire unit is placed intoa curing oven where polymerizationof the epoxy resin takes place.As the mandrel moves through thisoven, it is subjected to variouslevels of temperature and controllingthis temperature profile is apparentlyquite important in obtaining aconsistently high quality tube.

Another key production variableis the sizing of the glass fibersthemselves so as to ensure

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For every given epoxy formulation and type of glass fiber,a change in the sizing of these fibers can result in FRP tubeshaving very different mechanical and electrical performance.

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Insulator bending test. Preparing an insulator for bending test.

Up to now, hollow core composite insulators havemost typically been used as a direct one-for-onereplacement for porcelain.

tests as well as other testingprocedures developed in-house.Finally, the tube extremities aremachined to receive the flangeswhich are glued onto both ends.

The next operation in the productionprocess is performed in anatmosphere-controlled chamberwhere a special primer is appliedto the surface of the tube inpreparation for the next majorproduction step. The tube isnow ready for the externalsilicone housing.

Strmbeck states that theproduction technology selectedby ABB for application of thesilicone onto the FRP tube -an extrusion process in whichthe housing is helically woundonto the tube - is especiallyinteresting inasmuch as it offersseveral important productionadvantages. The shape of thesheds, a key factor influencing theinsulators electrical performance,is then determined by the designof the extrusion head.

According to Strmbeck, thisproduction process, which heindicates has now been patentedin many countries, is a very efficientand cost-effective way to apply thehousing onto the FRP tube. This isbecause the special extrusionmachine can employ only one dyeplaced on the machine head toproduce a wide range of insulatorshaving different diameters andlengths. This contrasts with oneof the main alternative productiontechnologies for hollow corecomposite insulators which

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optimum bonding between themand the resin. Says Strmbeck,the specific type of glass fibersand epoxy resin used to manufacturetubes are certainly important inensuring high performance. However,for every given epoxy formulationand for every type of glass fiber,a change in the sizing of these fiberscan result in FRP tubes having verydifferent electrical and mechanicalperformance.

Strmbeck goes on to explainthat the quality of the fiber-resin

interface is a determining factoraffecting the mechanical stress levelat which micro-cracks will appearwhen the insulator is placed undermechanical loads. On a microscopiclevel, this is basically equivalentto the damage level concept usedin the IEC 61462 standard.

Indeed, mechanical testing ofFRP samples having different resinto glass fiber bond strength clearlydemonstrates the influence ofsizing on the appearance of suchmicro-cracks.

FRP tubes can be manufacturedto have cylindrical, conical or evenbarrel-like shapes so as to bestadapt to the type of apparatuscomponent which will be placedinside them. When the siliconematerial is extruded onto andbonded to the tube in a later step,the resulting finished insulatormaintains exactly the same shapesince the housing follows all thecontours of the tube.

The quality of every tube is thenverified using various IEC-specified

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IEC electrical test of FRP tube sample after boiling. Set-up for IEC boiling test of FRP tube sample.

Blue door of a curing chamber and insulatorsdestined for the Three Gorges Project in China. Checking conformity of flange position.

Preparing extremities of tube to receive flanges. Extrusion of helical silicone housing onto tube.

Using only one dye placed on the head, the special extrusionmachine can produce a wide range of insulators withdifferent diameters and lengths. P h o

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New 400 kV breaker incorporating composite insulators.

An IEC Standard governing hollowcore insulators is not expectedbefore the end of 2006.

Hollow composite insulators haveseveral distinct advantages overporcelain in terms of performance,claims Strmbeck. They are quitelight and therefore ideal for use inareas prone to seismic disturbances.Also, because of the hydrophobicproperties of their silicone rubberhousings, they perform well underpolluted service conditions. Inaddition, if a shed is damaged,depending on the type and locationof the damage, it can be repaired.

Safety, according to Strmbeck,also favours composite insulatorsfor equipment applications.

An exploding porcelain shell dueto vandalism or an internalproblem, he says, can be lethalbecause of the sharp pieces ejectedat great velocity. By contrast,composite insulators are muchsafer because they just tear openunder such circumstances.

Another factor, adds Sundqvist,relates to production lead times.Hollow composite insulators,he remarks, have a very shortdelivery time compared to porcelain.This can be a real advantagein present market conditionswhere inventories are kept as lowas possible.

The utility marketplace is todayextremely conscious of costs and

therefore pricing of insulators takeson a more crucial role than perhapsever before.

ABB Plast manufactures hollow corecomposite insulators for apparatusfrom 145 kV to above 500 kV.Sundqvist acknowledges that forvoltage levels below 230 kV, theseinsulators may have some difficultyin competing price wise withporcelain alternatives, especiallywhen these come from Asia. Atthe same time, he emphasizes thatfor voltages higher than 300 kV,the pricing of composite insulatorsis today very competitive.

Until recently, nearly all theinsulator production of Plast hasbeen sold to other ABB units, notonly in Europe but also in Australiaand to a large extent in the UnitedStates. Now, with a fairly largeproduction capacity in place,Sundqvist indicates that he willput a significant effort to promotingsales to other OEM customers,even if they are competitors to ABB.

Asked about possible product ormanufacturing developments inthe future, Strmbeck replies,we really do not see any radicallynew hollow core composite insulatordesigns emerging over the nearterm. Rather, we believe that byoptimizing the present design andproduction process we will be ableto reduce production costs.

Up to now, hollow core compositeinsulators have most typicallybeen used as a direct one-for-onereplacement for porcelain. In thisrespect, says Strmbeck, it hasnot always been possible to takeadvantage of the full potential ofthis technology in terms of allowingfor radically new and innovativeequipment designs. To remedythis shortcoming, Sundqivst andStrmbeck believe that in the futureOEMs and manufacturers of theseinsulators should work more closelytogether in order to realize allthe possible benefits offered bythis technology.

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Pressure and tightness testing.

requires expensive new moulds forevery different tube diameter.

After extrusion, the housing is curedin an oven after which themanufacturing process is essentiallycomplete. However each insulatorstill has to go through a series of

quality control checks.For example, the main dimensionsof the unit as well as the

parallelism, co-axiality, concentricityand eccentricity of the flanges areverified. Moreover, every insulator issubjected to a mechanical bendingtest in which a cantilever load isapplied to one flange while the otheris solidly fastened to the testmachine.

If required by the apparatus ofwhich it will become a part, theinsulator may also undergo a

pressure test. While the insulator isunder internal pressure, a tightnesscheck is performed to test for leaksusing a mixture of air and hydrogen.

The finished insulators are thenshipped to various OEM customerswhere they will become an integralpart of a range of HV equipment andcomponents such as circuitbreakers, bushings, instrumenttransformers and cable terminations.

Although the technology behindhollow core composite insulators hasexisted for more than 20 years now,the process of its broad acceptanceby electric utilities has taken a verylong time and much longer than wasthe case for insulators used onoverhead lines. This, in turn, hasmade most electrical apparatusOEMs reluctant to commit toointensively to this technology,preferring instead to let the finalcustomer decide on choice ofinsulator type in each case.

Indeed, the fact that the end user ofapparatus is typically not in direct

contact with the manufacturer of thecomposite insulator is seen by somein this industry as having played anadverse role in the extent of marketpenetration of this technology.

Another factor which was not helpfulin the process of rapid marketacceptance was the relatively longtime it took to issue internationaldocuments and standards for thesetypes of insulators.

IEC Technical Report 61462 waspublished in late 1998 and used bysome in the industry as a Standard.However, this was already more thanten years after these insulators hadfirst been developed and marketed.

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With a fairly large production capacity now in place,Plast will put a significant effort to promoting sales to otherOEM customers, even if they might be competitors to ABB.

Chamber for pressure and tightness testing (in background). P h o

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Inmr Sepla Article_q205 (Origlr)