Insulator with resistivity gradient
A composite insulator includes an insulating elongated core, a protective layer surrounding the elongated core, the protective layer including an outer surface with a shed profile and an adhesive primer layer disposed between the elongated core and the protective layer for adhering the protective layer to the elongated core, the adhesive primer layer including a coupling agent and particles of a low resistivity material. The method for producing a composite insulator includes preparing a first solution including a solvent, a coupling agent and particles of a low resistivity material, applying the first solution on at least a part of an envelope surface of an insulating elongated core and thus forming one or more first adhesive primer layers and applying a protective layer onto the first adhesive primer layer on the elongated core, wherein the protective layer includes an outer surface with a shed profile.
1. A composite insulator, comprising:
an insulating elongated core;
a protective layer of a high resistivity material surrounding the elongated core, the protective layer comprising an outer surface with a shed profile; and
an adhesive primer layer disposed between the elongated core and the protective layer for adhering the protective layer to the elongated core, the adhesive primer layer comprising a coupling agent and particles of a low resistivity material;
wherein at least part of the adhesive primer layer comprises the particles of a low resistivity material and at least part of the adhesive primer layer is free of the particles of a low resistivity material.
2. The composite insulator according to claim 1 , wherein the surface resistivity of the adhesive primer layer comprising particles of a low resistivity material is between 10 8 and 10 14 Ω/square, and preferably between 10 10 and 10 12 Ω/square.
3. The composite insulator according to claim 1 , wherein the particles of the low resistivity material comprise particles of any of, or a combination of: Cr 2 O 3 iron oxides (Fe 2 O 3 , Fe 3 O 4 ), TiO 2 , ZnO, ZnO microvaristors, SiC, CuO, Carbon Black, graphene/graphite oxide and thermally reduced graphene/graphite oxide.
4. The composite insulator according to claim 1 , wherein the coupling agent comprises at least one of: silanes, titanates, orthosilicate esters or metal orthoesters.
5. The composite insulator according to claim 1 , wherein the proportion of particles of a low resistivity material in the adhesive primer layer is high enough for creating a percolated particle network and <40% by volume.
6. The composite insulator according to claim 1 , wherein the adhesive primer layer has a thickness of between 0.01 and 500 micrometer, and preferably between 0.1 and 100 micrometer.
7. The composite insulator according to claim 1 , wherein the protective layer comprises a high resistivity polymeric base material.
8. The composite insulator according to claim 7 , wherein protective layer comprises silicone rubber.
9. The composite insulator according to claim 1 , wherein the elongated core comprises a glass fiber reinforced composite tube.
10. A method for producing a composite insulator, the method comprises:
preparing a first solution comprising a solvent, a coupling agent and particles of a low resistivity material;
applying the first solution on at least a part of an envelope surface of an insulating elongated core and thus forming one or more first adhesive primer layers;
applying a second solution, the second solution comprising the solvent and the coupling agent and is without the particles of a low resistivity material, on the remaining parts of the envelope surface thus forming one or more second adhesive primer layers; and
applying a protective layer of a high resistivity material onto the first and second adhesive primer layers on the elongated core, wherein the protective layer comprises an outer surface with a shed profile.
11. The method according to claim 10 , wherein applying the first solution comprises spraying, dipping or painting the first solution onto the envelope surface of the elongated core.
12. The method according to claim 10 , wherein applying the second solution comprises spraying, dipping or painting the second solution onto the envelope surface of the elongated core.