Porcelain or Polymer

8/11/2019 Porcelain or Polymer

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High Voltage Surge Arresters

Porcelain or Polymer?


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ABB GroupDecember 10, 2013 | Slide 2

Insulator primary function

Insulate HV from ground Mechanical support

Protect the active partfrom the environment

Introduction


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Porcelain Housings


ADVANTAGES

Well proven

Widely accepted

Mechanically strong

DISADVANTAGES

Heavy

Easily damaged

Risk for injury

Limited mounting possibility

Many components

Hydrophilic surface


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Polymer Housings


ADVANTAGES

Less flashover r isk

Pollution performance

Short-circuit safety

Non-brittle

Low weight

Easier & flexible

installation

Seismic performance

Low maintenance

New applications

USER CONCERNS

Expected l ifetime?

Price comparison?

Dimensioning rules?

Integration into network?

Easy porcelain replacement?


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Silicone and EPDMused as HV insulation for over 35 years

Line insulators provided first applications

Apparatus insulators have approximately

20 years experience

Silicone is today by far the most common

polymer material used for HV applications

Applications and milestones


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RTV 1 = Room Temperature Vulcanizing 1 componentCondensation curing at room temperature, catalyzed by the moisture in the air that diffuses

into the rubber. Leaves acetic acid or alcohol's as by-product. Gluing and sealing

RTV 2 = Room Temperature Vulcanizing 2 componentAddition curing by platinum catalyst. Faster curing at higher temperatures. Liquid.Casting and encapsulating

HTV = High Temperature VulcanizingOne component solid rubber compound. Crosslinks at high temperature (130-190o)

with catalyst. Injection moulding and extrusion.

LSR = Liquid Silicon RubberTwo component addition curing by platinum catalyst . Curing at high temp.

Pasty to liquid consistence. Injection moulding.

FIM = Fast Injection MouldingOne component addition curing by platinum catalyst. Heat cured.

Pasty consistency. Fast injection moulding.

Silicone

Types


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Ageing

Permanent loss of propertiesthat affect the performance

Insulators are exposed to mechanical, electricaland environmental stresses

Only insulators that are dimensioned for all these stresseswill survive for the intended lifetime

Polymeric materials

are potentially susceptible to ageing

Porcelain is not (to the same extent)

Ageing

Cause for concern?


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Use hydrophobic materials

Use tracking resistant materials

Avoid or limit corona

Limit field stress

Change in hydrophobicity during artificial ageing as per IEC 61109

Ageing

Countermeasures

Silicone providesthe solution

in combination with

a sound design


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Silicone is naturally hydrophobicdue to low molecular weight oils

Automatic hydrophobicity recovery (HR) afterpossible temporary reduction under constantheavy pollution

Effective hydrophobicity transfer (HT)

adequate to withstand extreme pollutionepisodes

No ageing effect

Result:Excellent pollution performance with minimummaintenance throughout total service life

Silicone

Hydrophobicity


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Hydrophobicity Classification (HC)


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Silicone polymeric chain

CH3

Si

CH3

CH3

Si

CH3

OO

n n > 1000

Methyl

Oxygen

Silicone

Silicone has backbone structure composed of Si-O bonds.EP-rubber has backbone structure composed on C-C bonds.These two bonds have significantly different bond energies.

Silicone

Weathering resistance

BOND BOND ENERGY (kJ/m)

Si - O 445

C-C 348

Sunlight at 280nmwavelength 398

Si-O bond energy is higher than the energy of the sunlightgiving a high degree of UV stability


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Naturally highly fire-retardant

Readily improved by fillers Aluminium Trihydroxide (ATH)

ATH releases its bound water at 230Cand cools the arc

Self extinguishing

No burning drops

No halogens

Smoke suppressant

No hard insulator pieces to shatter

Reduced risk for damage or injury

Silicone

Safety


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Performance tests

Short term tests to verify that the insulator canwithstand the maximum stresses thatit is rated for

Tracking and erosion tests(weather ageing)

Accelerated long term laboratory tests to verify

that the material and the design of the insulatorare suitable for its intended use

Field tests

Long term testing under voltage in actualapplications and environments

Testing

Methods


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Inspection of composite insulators

Dungeness (England)


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Inspection of composite insulators

Kelso (South Africa)


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In comparison with ceramic insulatorssilicone insulators have Improved performance

under pollution in service in salt fog tests under ice and seismic conditions

Equal or better performance mechanical (standard or special)

Conclusion CIGRE (report A3-104) Shed profile designed after experience Possible to reduce the creepage distance

with at least one pollution levelaccording to IEC 60815

Conclusions

Silicone Apparatus Insulators


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Silicone

How much creepage is enough?

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Porcelain or Polymer