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Source of Information on International Developments in Transmission & Distribution

Issue 68 • Quarter Two - 2005 • Volume 13 - Number 2

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Remote Plant Plays Key Role in ABB Insulator Business

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

might at first glance seem a strange policy for a prominentmultinational such as ABB. Yet, asRoger Sundqvist, Plast’s Manager of Marketing and Sales explains,

the decision to locate allproduction of hollow corecomposite insulators in Piteå was actually quite a logical one giventhe plant’s 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 in the far northern reaches of Sweden is not exactlythe type of place where one might expect to find a supplier of strategiccomponents for HV networks.

However, tucked away in Piteå, a town located in a region near the ArcticCircle and where trees,rivers and lakes faroutnumber people, is ABB Plast - a factorysupplying the hollow core composite insulators

The process of ABB’s entry into the business of producing

hollow core composite insulators began long before the first

such insulator ever rolled off the production line in Piteå.

ABB Corporate Research in Sweden devoted several years ofdevelopment work during the mid1990s aimed at evaluating therelative electrical performance ofvarious silicone formulations as well 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. 6 No. 3). At the plant’sinaugural ceremony in the Spring of thatyear, key personnelfrom all of ABB’snearby manufacturingcenters for HV

apparatus were invited to tour thenew facility. Management at the new pilot plant used this opportunityto put forward their arguments about 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 ABB’s insulator business,being the sole supplier of the fiber-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 location where the tubes were themselvesbeing manufactured.

Says R&D Manager Anders Strömbeck,“Plast already had the expertisenecessary to manufacture the FRPtubes. All that we needed thereforewas 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 ABB’s productionof insulators in Piteå.”

Generally-speaking, a productionfacility for hollow core compositeinsulators is much more compact than would be required tomanufacture equivalent insulatorsmade of porcelain. This is because the manufacturing process involves far fewer steps - a fact which becomesvery evident when moving through the Piteå plant.

Strömbeck explains that all incoming raw materials needed formanufacturing these insulators arechecked for conformity to Plastspecifications. In the past, this was already routine work for theproduction of the FRP tubes. Now, a similar procedure has also beenestablished for the high-temperaturevulcanized (HTV) silicone rubber used in the external housing.

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Producing highly-specializedinsulators in northern Sweden and at quite a distance from many of the manufacturing facilities whichutilize them in HV apparatus

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

In point of fact, the process ofABB’s entry into the business ofsupplying hollow core compositeinsulators actually began long before the first such unit ever rolledoff the production line in Piteå.

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 merged to form ABB.

In this article, INMR ContributingEditor Dr. Claude de Tourreil, travels to visit what may well be the world’s most northerly factory in the field of HV engineering and reports on this facility’s products as well as manufacturingtechnology.

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54 I N S U L A T O R S

Remote Plant Plays Key Role in ABB Insulator Business

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

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Photo: Courtesy of ABB Plast

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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 rubbershed profiles on differing housing geometries less of an investment than other methods.

Composites insulators of today are a proven technology with well-established manufacturingpractices ensuring reliable service over the life of ones electrical apparatus. Compositeinsulators with silicone rubber sheds offer several advantages over traditional ceramics being

self-cleaning, reduced incidence of flashover, low weight and non-brittle construction. The self-cleaning property ofsilicone remains over its lifetime reducing incidence of flashover due to airborne contaminants. Their lightweightand 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 flexible and able tosurvive under varying mechanical loads. The silicone rubber sheds ensure reliable performance in harsh environmentalconditions. Together, the hollow composite with silicone rubber sheds is the best solution for today’s applications.

We took our lessonsfrom nature

Read more about hollow composite insulators underwww.abb.com/insulation

©2005 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 Strömbeck, a decisionwas made to work with two differentsilicone suppliers so as to bestensure an uninterrupted supply of this key strategic and what hesays is a relatively costly material.

The Piteå plant is set-up such thatthere are two separate windingstations to produce the FRP tubes which form the core of each insulator. One station cansimultaneously accommodate two 4 meter-long steel mandrels while a second winding machine canproduce tubes of up to 7 meters

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

This is accomplished mainly byselecting the correct angle forwinding onto the mandrel the glass fibers which have been pre-impregnated with resin. The thickness of the tube wall also influences its final mechanicalstrength.

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

Another key production variable is 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 tubes

having very different mechanical and electrical performance.

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Figure 1: Crack Density Versus Elongation (in %)

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Insulator bending test. Preparing an insulator for bending test.

Up to now, hollow core composite insulators have

most typically been used as a direct one-for-one

replacement 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 applied to the surface of the tube inpreparation for the next majorproduction step. The tube is now ready for the external silicone housing.

Strömbeck states that theproduction technology selected by ABB for application of thesilicone onto the FRP tube - an extrusion process in which the housing is helically wound onto the tube - is especiallyinteresting inasmuch as it offersseveral important productionadvantages. The shape of the sheds, a key factor influencing theinsulator’s electrical performance,is then determined by the design of the extrusion head.

According to Strömbeck, thisproduction process, which heindicates has now been patented in 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 one of the main alternative productiontechnologies for hollow corecomposite insulators which

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optimum bonding between them and the resin. Says Strömbeck, “the specific type of glass fibers and 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.”

Strömbeck goes on to explain that 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 equivalent to the damage level concept used in the IEC 61462 standard.

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

FRP tubes can be manufactured to 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 extrusion

machine can produce a wide range of insulators with

different diameters and lengths. Ph

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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 Strömbeck. “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 Strömbeck, also favours composite insulators for equipment applications.

“An exploding porcelain shell due to vandalism or an internalproblem,” he says, “can be lethalbecause of the sharp pieces ejectedat great velocity. By contrast,composite insulators are much safer 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 advantage in present market conditions where inventories are kept as low as 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. At the same time, he emphasizes thatfor voltages higher than 300 kV, the pricing of composite insulators is 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 will put a significant effort to promotingsales to other OEM customers, even if they are competitors to ABB.

Asked about possible product ormanufacturing developments in the future, Strömbeck 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 typically been used as a direct one-for-onereplacement for porcelain. In thisrespect, says Strömbeck, it has not always been possible to takeadvantage of the full potential ofthis technology in terms of allowingfor radically new and innovativeequipment designs. To remedy this shortcoming, Sundqivst andStrömbeck believe that in the futureOEMs and manufacturers of theseinsulators should work more closelytogether in order to realize all the possible benefits offered by this 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 ofquality 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 directcontact 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 other

OEM customers, even if they might be competitors to ABB.

Chamber for pressure and tightness testing (in background).

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