Use of a silicone rubber composition for the manufacture of an insulator for high voltage direct current applications
AssigneeMomentive Performance Materials Inc.
InventorsBeatrice Grau, Lada Bemert, Harry Zumaque, Oliver Safarowsky
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Abstract
The invention relates to a silicone rubber composition having specific dielectric properties which can be used as insulator material in high voltage direct current applications and a method for the manufacture of cable accessories like cable joints. The invention comprises as well a method for the determination of the optimum dielectric properties and the related amount of dielectric active additives.
Claims16
A method for the manufacture of a cable joint or a cable termination comprising the steps of:
- (i) providing a silicone composition, obtained by curing a composition comprising:
- a) 100 pt·wt. of at least one polyorganopolysiloxane having alkenyl groups,
- b) 0-100 ptwt. of a crosslinker component comprising at least one polyorganohydrogensiloxane,
- c) 0-100 pt·wt. of a filler component comprising one or more reinforcing silicas,
- d) >0.1-2 pt·wt. of at least one dielectric active compound selected from the group consisting of oxides, carbides, ferrites or spinels of any of Ti, Al, Zn, Fe, Mn, Mo, Ag, Bi, Zr, Ta, B, Sr, Ba, Ca, Mg, Na, K, and Si,
- e) a curing catalyst selected from the group consisting of 0-1000 ppm of a compound enabling hydrosilylation and 0.1 to 2 wt.-% of an organic peroxide each related to the sum of the amounts of the components a) to d), and
- f) 0-50 pt·wt. of one or more auxiliary additives,
- said silicone composition having a temperature dependency of the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm, such that the ratio of the maximum volume resistivity and the minimum volume resistivity is <10, and the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm is between 1*1014 and 1*1016 Ohm*cm,
- (ii) providing a conductive shaped optionally cured silicone composition which differs from the silicone composition of (i), and
- (iii) encapsulating at least a part of the surface of the composition of (ii) with a composition according to (i) in a mold to form and cure a cable joint or cable termination.
A method of insulating or field grading of high voltage direct current assemblies, comprising the step of forming an insulating or field grading layer in said high voltage direct current assemblies by curing a composition comprising:
- a) 100 pt·wt. of at least one polyorganopolysiloxane having alkenyl groups,
- b) 0-100 ptwt. of a crosslinker component comprising one or more polyorganohydrogensiloxanes,
- c) 0-100 pt·wt. of a filler component comprising one or more reinforcing silicas or resins,
- d) >0.1-2 pt·wt. of at least one dielectric active compound selected from the group consisting of oxides, carbides, ferrites or spinels of any of Ti, Al, Zn, Fe or Mg,
- e) a curing catalyst selected from the group consisting of 0-1000 ppm of a compound enabling hydrosilylation and 0.1 to 2 wt.-% of an organic peroxide each related to the sum of the amounts of the components a) to d), and
- f) 0-50 pt·wt. of one or more auxiliary additives,
- said cured silicone composition having a temperature dependency of the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm, such that the ratio of the maximum volume resistivity and the minimum volume resistivity is less than 10, and the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm is between 1*1011 and 1*1016 Ohm*cm.
Dependencies are inferred from the claim text.