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Owens Corning Develop Boron Free Glass for High-Voltage Applications

08 April 2005

Owens Corning have introduced SE 8400 LS, a new single-end Type 30 roving for pultruded FRP applications in medium- and high-voltage transmission and distribution long-rod insulators.

In a move which signals a measure of diversification for Owens Corning - being the first to develop e-glass on this scale for the electrical distribution network - the new low seed roving is aimed at competing and potentially replacing the widespread use of ceramic rod insulators in high voltage applications, especially as, according to Owen Corning, the temperature resistance of the composite insulator rods is equivalent to ceramic rods and competes on cost with ceramics.

The SE 8400 LS combines the anti-corrosion, electrical, and mechanical benefits of boron free Advantex E-glass manufactured using advanced glass melting technology and advanced low-seed filament technologies, ensuring seed levels well below .5 seeds/gram. Minimizing microscopic bubble voids or “seeds” in the glass avoids the formation of hollow filaments, which increase conductance, offering the path of least resistance to the electrical energy, and causing system failure.

Seeds are caused by gas formation from raw ingredients in the glass, as well as melting conditions within the furnace. It is important to control both the number and size of the seeds within the glass. A large number of seeds within the glass means a greater number of voids within the filaments, reducing the overall resistance of the glass filaments and the composite matrix.

Previously, most other low seed filament technologies failed to reduce the seeds per gram to beyond 10 which exceeded many of the worldwide regulations on seed count.

The properties of SE 8400 LS single-end Type 30 roving offers not only the required high electrical resistance from low seed production but also:
higher corrosion and temperature resistance of Advantex over conventional E-glass, reducing brittle fracture failure,
quicker processing than alternatives owing to fast wet-out in polyester, vinyl ester and epoxy resins,
low migration for improved wet-out and glass to resin bonding
improved flashover resistance in highly polluted areas
high mechanical strength (weight ratio)
greater design flexibility and overall system costs reduction

“While the industry has been working with non-ceramic insulators for several years, developing and ensuring the consistent manufacture of a non-corrosive, boron-free glass with seed counts well below .5 seeds per grams has been the “tipping point” level this marketplace needs to transform to a new technology – and SE 8400 truly delivers that solution,” said Wisdom Dzotsi, Owens Corning Global Product Manager, T30 Direct Roving.

MacLean Power Systems (US) are one of the customers have tested the glass with James Schmiedeknecht, VP International Sales and Marketing commenting that “avoiding moisture ingress has been and will continue to be the first line of defence in preventing brittle fracture. Brittle fracture is a primary concern of the utility engineer when evaluating the use of composite insulators.”

Adding that “the major insulator manufacturers have paid particular attention to sealing the end fitting of the FRP rod, silicone rubber housing junction and several have designed redundant seal systems. The use of boron free glass fibres has been a long acknowledged means of preventing brittle fracture if an insulator's housing has been breached. However, earlier generations of boron free fibres had seed count levels that were too high and wouldn't consistently pass qualification tests mandated by insulator standards,” continued Schmiedeknecht.

“Owens Corning has solved that problem with their Advantex corrosion resistant E-glass fibre that is low in seed count. Insulator manufacturers like MacLean Power Systems can now take full advantage of boron free glass fibres and also have wicking performance comparable to standard E-glass. MacLean Power Systems can now offer the utility engineer that extra margin of safety at a relatively low incremental cost,” Schmiedeknecht concluded.

Owens Corning SE 8400 LS roving is available globally and manufactured in Norway (Europe). The Roving is available in 113 yield (4400 TEX), 103 yield (4800 TEX), and 52 yield (9600 TEX). The 52 yield requires fewer ends of roving to produce a part of equal glass content, something Owens Corning regard as a significant advantage for pultrusion manufacturers with building or creel size restrictions, who wish to produce larger parts.

Speaking to Owens Corning at JEC earlier this week, it appears that the roving has potential in the growing wind energy industry as well other industries that require power distribution via a generator or electrical network. Owens Corning would not confirm the number of customers for the product but they did state that interest had been received from China and Europe.

The image show voids (black dots) within filaments in a composite matrix. Typical filament diameters are 20-30 microns.






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