Gel impregnated bushing

1. A high-voltage (HV) bushing comprising:

a condenser core configured for surrounding a HV electrical conductor, the condenser core comprising an insulation material comprising wound layers of a permeable solid material impregnated with a thermo-reversible gel, the thermo-reversible gel comprising an oil and a thickener, the oil comprising iso-paraffinic oil in an amount within the range of 0.1-100 wt % of the oil, and the thickener comprising at least one styrenic copolymer in an amount within the range of 0.1-10 wt % of the thermo-reversible gel, the at least one styrenic copolymer comprising polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene, polystyrene-b-poly (ethylene/butylene)-b-polystyrene and polystyrene-b-poly(ethylene/propylene),

a liquid form of the thermo-reversible gel having a viscosity below 1 Pa·s, and

a solid form of the thermo-reversible gel having a viscosity of at least 1 Pa·s at 105° C.

2. The bushing of claim 1 , wherein the oil comprises iso-paraffinic oil in an amount within the range of 50-100 wt % of the oil.

3. The bushing of claim 1 , wherein the at least one styrenic copolymer is present in an amount of at least 1 wt % of the thermo-reversible gel.

4. The bushing of claim 1 , wherein the at least one styrenic copolymer has an average molecular weight of at least 200 kg/mole.

5. The bushing of claim 1 , wherein the polystyrene-b-poly(ethylene-ethylene/propylene) -b-polystyrene and polystyrene-b-poly(ethylene/butylene)-b-polystyrene are in an amount of at least 0.1 wt % of the thermo-reversible gel.

6. The bushing of claim 1 , wherein the polystyrene-b-poly (ethylene/propylene) in an amount of at least 0.1 wt % of the gel.

7. The bushing of claim 1 , wherein the oil comprises a mineral oil in an amount of a range of 10-50 wt % of the oil, blended with the iso-paraffinic oil.

8. The bushing of claim 1 , wherein the oil comprises the iso-paraffinic oil in an amount of a range of 60-80 wt % of the oil.

9. The bushing of claim 1 , wherein the permeable solid material comprises a cellulose-based material, an aramid paper, or a combination thereof.

10. A method of preparing a condenser core for a high-voltage (HV) bushing, the method comprising:

winding a web of a permeable solid material around a longitudinal passage for a HV electrical conductor;

mixing an oil with a thickener to form a thermo-reversible gel;

heating the thermo-reversible gel to a first temperature at which the thermo-reversible gel has a viscosity associated with a liquid form of the thermo-reversible gel below 1 Pa·s;

impregnating the wound permeable solid material with the thermo-reversible gel at said first temperature to form an insulation material comprising wound layers of the permeable solid material impregnated with the thermo-reversible gel; and

cooling the insulation material to a second temperature that is lower than 105° C. at which the thermo-reversible gel has a viscosity associated with a solid form of the thermo-reversible gel of at least 1 Pa·s to form the condenser core,

the oil comprising iso-paraffinic oil in an amount within the range of 0.1-100 wt % of the oil and the thickener comprising at least one styrenic copolymer in an amount within the range of 0.1-10 wt % of the thermo-reversible gel, the styrenic copolymer comprising:

a tri-block copolymer comprising at least one of polystyrene-b-poly(ethylene-ethylene/propylene) -b-polystyrene and polystyrene-b-poly(ethylene/butylene)-b-polystyrene; and a di-block copolymer comprising polystyrene-b-poly(ethylene/propylene).

11. The method according to claim 10 , wherein heating the thermo-reversible gel to the first temperature comprises heating the thermo-reversible gel to at least a first temperature at which the thermo-reversible gel has a viscosity at or below 0.1 Pa·s.

12. The method according to claim 10 , wherein cooling the insulation material to the second temperature comprises cooling the insulation material to the second temperature at which the thermo-reversible gel has a viscosity at or above 5 Pa·s.

13. The method according to claim 10 , wherein the first temperature is a temperature above a transition temperature of the thermo-reversible gel, wherein the second temperature is a temperature below the transition temperature, wherein the transition temperature is within a temperature range of 80° C. to 105° C.

14. The method according to claim 10 , wherein heating the gel to the first temperature comprises heating the thermo-reversible gel to at least a first temperature at which the thermo-reversible gel has a viscosity at or below 0.01 Pa·s.

15. The method according to claim 10 , wherein cooling the insulation material to the second temperature comprises cooling the insulation material to the second temperature at which the thermo-reversible gel has a viscosity of at least 100 Pa·s.

16. A high-voltage (HV) bushing comprising:

a condenser core configured for surrounding a HV electrical conductor, the condenser core comprising an insulation material comprising wound layers of a permeable solid material impregnated with a thermo-reversible gel, the thermo-reversible gel comprising an oil and a thickener, the oil comprising iso-paraffinic oil in an amount within the range of 0.1-100 wt % of the oil, and the thickener comprising at least one styrenic copolymer in an amount within the range of 0.1-10 wt % of the thermo-reversible gel, the at least one styrenic copolymer comprising polystyrene-b-poly(ethylene/butylene)-b-polystyrene and polystyrene-b-poly(ethylene/propylene),

a liquid form of the thermo-reversible gel having a viscosity below 1 Pa·s, and

a solid form of the thermo-reversible gel having a viscosity of at least 1 Pa·s at 105° C.