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US 6,124,549 AGranted
Electrical stress control
OwnerChristian Kemp, Georg Bachmaier +1inventors
InventorsChristian Kemp, Georg Bachmaier, Hansjoerg Gramespacher
Life of this patent
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Abstract
A composition for use as an electrical stress controlling layer (12) for use with cable joints and terminations has a non-linear V-I characteristic. The composition comprises a polymeric matrix filled with doped zinc oxide varistor powder. The particulate filler is sieved at 125 micrometers, calcined at 1100.degree. C., and lightly ground to maintain the spherical shape of the particles. More than 50% by weight of the particles have a maximum dimension between 5 and 100 micrometers.
Claims25
An electrical stress- controlling composition, comprising:
- (a) a polymeric matrix, and
- (b) a particulate filler comprising doped zinc oxide varistor powder;
- wherein
- (i) the particles of the filler are calcined at a temperature between 800.degree. C. and 1400.degree. C., and subsequently broken up such that substantially all of the particles retain their original shape,
- (ii) at least 85% of the weight of the filler comprises zinc oxide,
- (iii) more than 50% by weight of the filler particles have a maximum dimension of between 5 and 100 micrometers such that the composition has a specific impedance that decreases by at least a factor of 10 when subjected to an electric field increase of less than 5 kV/cm at a region within an electrical field range of 5 kV/cm to 50 kV/cm,
- (iv) the filler comprises between 5% and 60% of the volume of the total composition;
- and
- (v) the particles of the filler are generally spherical.
6 more elements
An electrical stress-controlling composition, comprising:
- a polymeric matrix;
- and
- a plurality of filler particles comprising:
- (a) a zinc oxide varistor powder;
- and
- (b) a dopant layer on particles of the zinc oxide varistor powder, the dopant layer being selected from the group consisting of Bi.sub.2 O.sub.3, Cr.sub.2 O.sub.3, Sb.sub.2 O.sub.3, Co.sub.2 O.sub.3, MnO.sub.3, Al.sub.2 O.sub.3, CoO, Co.sub.3 O.sub.4, MnO, MnO.sub.2, SiO.sub.2, and trace amounts of lead, iron, boron and aluminum;
- wherein
- (i) the filler particles are calcined at a temperature of between about 800.degree. C. and about 1400.degree. C., and subsequently broken up such that substantially all of the filler particles retain their original shape;
- (ii) at least about 85% of the weight of the filler particles comprises zinc oxide;
- (iii) more than about 50% by weight of the filler particles have a maximum dimension of between about 5 and about 100 micrometers;
- and
- (iv) the filler particles comprise between about 5% and about 60% of the volume of the electrical stress-controlling composition.
9 more elements
An electrical stress control apparatus for an electrical power cable comprising:
- a cover configured to be placed over the electrical power cable;
- and
- an electrical stress-controlling composition positioned between the cover and the electrical power cable, the electrical stress-controlling composition comprising:
- (a) a polymeric matrix, and
- (b) a particulate filler comprising doped zinc oxide varistor powder;
- wherein
- (i) the particles of the filler are calcined at a temperature of between about 800.degree. C. and about 1400.degree. C., and subsequently broken up such that substantially all of the particles retain their original shape;
- (ii) at least about 85% of the weight of the filler particles comprises zinc oxide;
- (iii) more than about 50% by weight of the filler particles have a maximum dimension of between about 5 and about 100 micrometers;
- (iv) the composition has a specific impedance that decreases by at least about a factor of 10 when subjected to an electric field increase of less than about 5 kV/cm at a region within an electrical field range of about 5 kV/cm to about 50 kV/cm;
- (v) the filler particles comprise between about 5% and about 60% of the volume of the composition;
- and
- (vi) the filler particles are generally spherical.
10 more elements
An electrical stress control apparatus for an electrical power cable comprising:
- a cover configured to be placed over the electrical power cable;
- and
- an electrical stress-controlling composition positioned between the cover and the electrical power cable, the electrical stress-controlling composition comprising:
- a polymeric matrix;
- and
- a plurality of filler particles comprising:
- (a) a zinc oxide varistor powder;
- and
- (b) a dopant layer on particles of the zinc oxide varistor powder, the dopant layer being selected from the group consisting of Bi.sub.2 O.sub.3, Cr.sub.2 O.sub.3, Sb.sub.2 O.sub.3, Co.sub.2 O.sub.3, MnO.sub.3, Al.sub.2 O.sub.3, CoO, Co.sub.3 O.sub.4, MnO, MnO.sub.2, SiO.sub.2, and trace amounts of lead, iron, boron and aluminum;
- wherein
- (i) the filler particles are calcined at a temperature of between about 800.degree. C. and about 1400.degree. C., and subsequently broken up such that substantially all of the filler particles retain their original shape;
- (ii) at least about 85% of the weight of the filler particles comprises zinc oxide;
- (iii) more than about 50% by weight of the filler particles have a maximum dimension of between about 5 and about 100 micrometers;
- and
- (iv) the filler particles comprise between about 5% and about 60% of the volume of the electrical stress-controlling composition.
12 more elements
Dependencies are inferred from the claim text.