Capacitor with insulation composition showing thermo-reversible oil-to-gel-transition

Patent metadata

Field	Value
Publication number	US-11657973-B2
Application number	US-201916982278-A
Country	US
Kind code	B2
Filing date	Mar 11, 2019
Priority date	Mar 19, 2018
Publication date	May 23, 2023
Grant date	May 23, 2023

Abstract

A wet capacitor is provided, and the use of an insulation fluid composition in such a capacitor. The capacitor includes a package of a metal foil and a polymeric insulating film, or of a metallized polymeric film, wherein the insulation composition includes a synthetic or natural aromatic oil and a polymer. The insulation composition is configured to undergo a thermo-reversible oil-to-gel transition at a predefined gel-point temperature. Further, methods of producing such wet capacitors are provided, optionally including additional filling materials, and methods of sealing leaks in such capacitors.

First claim

The invention claimed is:

1. A capacitor, comprising:
a container, comprising:
at least one wound package of a metal foil and a polymeric insulating film, or of a metallized polymeric film, and
an insulation composition,

wherein the insulation composition comprises:
a synthetic aromatic oil or a natural aromatic oil, and
a polymer in a concentration of about 0.1 wt % to about 10 wt %,

wherein the insulation composition is configured to undergo a thermo-reversible gelation below a gel-point temperature in the range from about 30° C. to about 90° C., the gel point being defined as the temperature at which the storage modulus G′ of the insulation composition is equal to the loss modulus G″ of the insulation composition.

2. The capacitor of claim 1 , wherein the insulation composition has a complex viscosity at a temperature below the gel point, which is about a factor of at least 70 larger than the complex viscosity at temperatures above the gel point.

3. The capacitor of claim 1 , wherein the insulation composition has a complex viscosity of equal to or greater than 0.01 Pa·s at a temperature below the gel point, and a complex viscosity at temperatures above the gel point which is substantially equal, with a difference of less than about 30%, to the complex viscosity of the insulation composition without the polymer.

4. The capacitor of claim 1 , wherein the polymer comprises a polymer and/or a copolymer and/or a block copolymer, a tri-block copolymer and/or a di-block copolymer, which is selected from at least one of:
ethylene butyl acrylate;
styrene-ethylene-(ethylene-isopropylene)-styrene;
ethylene-vinylacetate;
ethylene-butyleneacrylate; and
syndiotactic polystyrene.

5. The capacitor of claim 1 , wherein the insulation composition further comprises an additive, being at least one of:
an inorganic filler, at a concentration of 10 wt. % or less based on the total weight of the insulation composition, and
an antioxidant, at a concentration of 2 wt. % or less based on the total weight of the insulation composition;
and wherein a space in the capacitor other than the wound package is filled up with the insulation composition or with plastic material or with a mineralic substance, or with a mixture of any of these substances.

6. The capacitor of claim 1 , wherein the aromatic oil comprises a benzyl-toluene.

7. A capacitor according to claim 1 , comprising:
an oil-based insulation composition is absorbed by the at least one wound package,
and wherein a space in the container other than the wound package is filled up with a plastic material or with a mineralic substance, or with a mixture that includes a dielectric fluid.

8. A method of producing the capacitor according to claim 1 , comprising:
adding hot gel into the container with the metal film, the polymeric insulating film or the metallized polymeric film at below the gel transition temperature,
filling the container with the aromatic oil at reduced pressure below the gel transition temperature,
sealing the container,
heating the container to about 80° C., and mixing the gel and oil at elevated temperature, and
cooling the container down to room temperature.

9. A method of producing a capacitor according to claim 1 , comprising: filling the container with the at least one wound package with the insulation composition at reduced pressure,
storing for 20-60 hours to allow the films to swell in the oil,
removing excessive oil that was not absorbed by the at least one wound package, by emptying the container at room temperature,
heating the container to about 80° C.,
filling the container with the insulation composition that was heated; or alternatively filling up the container with a plastic material or with a mineralic substance or a mixture thereof or a mixture thereof together with the insulation composition;
cooling the container down to room temperature,
filling up the insulation composition to compensate shrinkage, and
sealing the container.

10. A method of treating a leak in a capacitor that includes:
a container, comprising:
at least one wound package of a metal foil and a polymeric insulating film, or of a metallized polymeric film, and
an insulation composition,
wherein the insulation composition comprises:
a synthetic aromatic oil or a natural aromatic oil, and
a polymer in a concentration of about 0.1 wt % to about 10 wt %,

wherein the insulation composition is configured to undergo a thermo-reversible gelation below a gel-point temperature in the range from about 30° C. to about 90° C., the gel point being defined as the temperature at which the storage modulus G′ of the insulation composition is equal to the loss modulus G″ of the insulation composition, the method comprising:
operating the capacitor, wherein the insulation composition is configured such that the insulation composition is in a liquid phase during standard operation of the capacitor, in case of a leak in the capacitor to the outside, spilling an amount of the insulation composition through the leak, and

wherein the spilled amount undergoes a thermo-reversible oil-to-gel transition during or after the spilling when the spilled amount is exposed to the temperature outside the container.

11. A method of producing a capacitor that includes a container, comprising:
 at least one wound package of a metal foil and a polymeric insulating film, or of a metallized polymeric film, and
an insulation composition,
wherein the insulation composition comprises:
a synthetic aromatic oil or a natural aromatic oil, and
a polymer in a concentration of about 0.1 wt % to about 10 wt %,

wherein the insulation composition is configured to undergo a thermo-reversible gelation below a gel-point temperature in the range from about 30° C. to about 90° C., the gel point being defined as the temperature at which the storage modulus G′ of the insulation composition is equal to the loss modulus G″ of the insulation composition, the method comprising:
wrapping packages of the metal foil and the polymeric insulating film or of the metallized polymeric film, by insulating papers; heating the insulation composition;

impregnating the wrapped packages, with the heated insulation composition, at a reduced pressure and an elevated temperature, to allow the heated insulation composition to impregnate the package, and letting the films swell for several hours,
cooling the container with the packages and allowing the insulating composition to gel at room temperature, refill the insulation composition to compensate shrinkage, and
sealing the container.

Assignees

• Hitachi Energy Switzerland Ag

Inventors

• Qi Lejun
• Scheel Saskia
• Logakis Emmanuel
• Bandalo Felix
• Zhang Richard-Changyu
• Singh Biswajit

Classifications

• C08L91/00

  Compositions of oils, fats or waxes; Compositions of derivatives thereof · CPC title

• C08L23/12

  Polypropene · CPC title

• H01G4/015

  Special provisions for self-healing · CPC title

• H01G2/12

  Protection against corrosion (H01G2/10 takes precedence) · CPC title

• C08L23/0869

  with unsaturated acids, e.g. [meth]acrylic acid; with unsaturated esters, e.g. [meth]acrylic acid esters · CPC title