Renewable hydrocarbon based insulating fluid

Abstract

Electrical equipment including insulating fluid and having isoparaffins derived from a renewable carbon source, the fluid having a flash point of at least 210° C. and comprising at least 70 wt % of the isoparaffins. The electrical equipment can be installed and operated subsea.

Claims

1. An electrically insulating fluid comprising isoparaffins derived from a renewable carbon source in an electrical equipment, the fluid having a flash point of at least 220° C. and comprising at least 70 wt % of the isoparaffins.

2. The fluid according to claim 1, comprising at least 90 wt % of the isoparaffins.

3. The fluid according to claim 1, with a biodegradability of at least 65% or at least 95% according to OECD 301B.

4. The fluid according to claim 1, wherein the isoparaffins have been derived from the renewable carbon source by means of micro organisms or algae, such as bacteria, yeast or algae.

5. The fluid according to claim 1, wherein the isoparaffins have been derived from terpenes or unsaturated compounds obtained from the renewable carbon source.

6. The fluid according to claim 5, wherein the isoparaffins have been derived from terpenes by means of micro organisms or algae, such as bacteria, yeast or algae.

7. The fluid according to claim 1, wherein the renewable carbon source is biomass, such as sugar cane, molasses or cellulose pulp.

8. The fluid according to claim 1, wherein the fluid has a pour point of less than −25° C. in accordance with ASTM D 5950.

9. The fluid according to claim 1, wherein the fluid has a kinematic viscosity at 100° C. in the range 2 cSt to 10 cSt.

10. The fluid according to claim 1, wherein the fluid also comprises one or more additives, such as an antioxidant or a pour point depressant.

11. The fluid according to claim 1, wherein the electrical equipment is an electrical transformer, an electrical motor, a capacitor, a reactor or a bushing.

12. An electrical equipment having an electrically insulating fluid comprising isoparaffins derived from a renewable carbon source, the fluid having a flash point of at least 220° C. and comprising at least 70 wt % of the isoparaffins.

13. The electrical equipment of claim 12, wherein the electrical equipment is an electrical transformer, an electrical motor, a circuit breaker pole, a frequency converter selected from the group comprising, a capacitor, a reactor, a bushing, or a combination of these.

14. The electrical equipment of claim 12, wherein the electrical equipment is installed and operated subsea.

15. The electrical equipment of claim 14, wherein the electrical equipment is installed inside a housing containing the electrically insulating fluid and one or more parts of the electrical equipment are immersed in the insulating fluid.

16. The fluid according to claim 1, wherein the electrical equipment is installed and operated subsea.

17. The fluid according to claim 1, wherein the electrical equipment is installed inside a housing containing the electrically insulating fluid and one or more parts of the electrical equipment are immersed in the insulating fluid.

18. A transformer comprising: a housing; a metal core inside the housing, the metal core surrounded by windings; the fluid according to claim 1 inside the housing, the metal core immersed in the fluid; the transformer pressurized to a hydrostatic pressure level on a seabed.

19. The electrical equipment of claim 14, wherein the electrical equipment is pressurized to a hydrostatic pressure level on a seabed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic side sectional view of an embodiment of an electrical transformer in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. However, other embodiments in many different forms are possible within the scope of the present disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.

(4) Base oils, e.g. isoparaffins can be derived from terpene feedstocks by reacting them with olefin co-monomers (see e.g. 2. WO 2012/141784). To generate isoparaffins, a hydrocarbon terpene feedstock is coupled with one or more olefin co-monomers in the presence of a catalyst to form one or more branched alkenes. These branched alkenes are then hydrogenated to form one or more isoparaffins. An interesting aspect of these derived isoparaffins is that the terpene feedstocks can be produced from a renewable source and their properties can be tuned by selecting the right type of olefin co-monomer and terpene for the reaction.

(5) Isoparaffin fluids have been developed for electrical insulation purpose and today, isoparaffin oils for transformer applications are both commercially available and also under development. Isoparaffins can be produced through different processes, e.g. refining of crude oil or by gas to oil (GTL) technologies. Although isoparaffins derived from crude oil have desirable properties with respect to viscosity and pour points, they have only marginally higher biodegradability compared to existing mineral oils and low fire/flash point values.

(6) In some embodiments, the insulating fluid comprises at least 90 wt % of the isoparaffins. This even higher isoparaffin content may improve the flash point and the biodegradability of the fluid even further. In some embodiments, the fluid has a biodegradability of at least 65%, which is higher than a corresponding isoparaffin fluid derived from mineral oil. Biodegradability may be measured in accordance the OECD 301B. In some embodiments the fluid is readily biodegradable in accordance the OECD 301B.

(7) In some embodiments, the isoparaffins have been derived from the renewable carbon source by means of micro organisms or algae, such as bacteria, yeast or algae. Biological production, at least in one stage, of the isoparaffins and the isoparaffin fluid may be convenient and more environmentally friendly than regular chemical synthesis. See e.g. the microbial methods of WO 2012/141784 and WO 2012/116783 mentioned in the background.

(8) In some embodiments, the isoparaffins have been derived from terpenes or unsaturated compounds obtained from the renewable carbon source. In these embodiments, the isoparaffins are derived from the renewable carbon source, via terpenes or (other) unsaturated compounds. The terpenes may first be derived from the renewable carbon source and then, the isoparaffins are derived from said terpenes, or the terpenes may be part of the renewable carbon source. Terpenes may be convenient compounds to produce isoparaffins from (see e.g. the method of WO 2012/141784). Thus, in some embodiments, the isoparaffins have been derived from terpenes by means of micro organisms or algae, such as bacteria, yeast or algae.

(9) In some embodiments, the renewable carbon source is biomass, such as sugar cane, molasses or cellulose pulp. However, any renewable carbon source, as opposed to fossil carbon sources, is contemplated for the present invention.

(10) In some embodiments, the fluid has a pour point of less than −25° C. in accordance with ASTM D 5950. A low temperature pour point is advantageous in electrically insulating fluids for use in electrical equipment, and may be obtained with a fluid in accordance with the present invention.

(11) In some embodiments, the fluid has a kinematic viscosity at 100° C. in the range 2-10 cSt (centi Stokes or mm.sup.2/s). Such a kinematic viscosity is advantageous in electrically insulating fluids in electrical equipment, and may be obtained with a fluid in accordance with the present invention.

(12) In some embodiments, the fluid also comprises an additive, such as an antioxidant or a pour point depressant. The isoparaffins may be combined with any suitable additives for improving properties of the insulating fluid for the application in which the fluid is used.

(13) In some embodiments, the electrical equipment is an electrical transformer, an electrical motor, a capacitor, a circuit breaker pole, a frequency converter, a reactor or a bushing. The fluid is envisioned to be advantageously used in transformers, but also used in electrical motors or other electrical equipment, especially high temperature apparatuses.

(14) FIG. 1 is a schematic illustration of an embodiment of an electrical equipment of the present invention, here in the form of an electrical transformer (1). The transformer (1) has housing (2) containing the electrical parts of the transformer immersed in an insulating fluid (3). The electrically insulating fluid (3) is in accordance with any embodiment thereof discussed herein, having a flash point of at least 210° C. and comprising at least 70 wt % of the isoparaffins. At the top of the transformer 1, a gas, e.g. air, phase (6) may be present within the housing and above a top surface of a liquid fluid (3). The electrical parts of the transformer (1) comprises a metal core (4) surrounded by coils/windings (5) of electrical conductors (8) and (10). In the very simplified illustration of the FIGURE, an incoming electrical conductor (8) enters within the housing (2) via a bushing (7), and an outgoing electrical conductor (10) exits the housing (2) via a bushing (10). The transformer (1), or other electrical equipment in which the fluid is used, may e.g. be a high temperature transformer, arranged to operate at a temperature which is higher than the normal operating temperature of mineral oil derived insulating fluid, e.g. an operating temperature of above, 160° C., 180° C. or above 200° C.

(15) In recent years, there has been a growing interest in installing electrical installations on the sea floor in depths from a few tens of meters to even kilometers. Subsea oil and gas production employs electric equipment like drilling motors, pumps, and compressors that are currently driven by frequency converters located on topside platforms. Electric power is provided to the subsea machinery by expensive umbilicals. By installing transformers, breakers, frequency converters and other electric power equipment subsea, cables and topside installations could be spared and enormous cost savings could be achieved.

(16) In bringing electric power at subsea depths, two general concepts exist: (1) the equipment stays at atmospheric pressure; and (2) the equipment is pressurized to the hydrostatic pressure level on seabed. The two concepts can be differentiated as follows. Concept (1) has the advantage that standard electric components, known from onshore installations, can be used, while disadvantages include thick walls needed for the enclosure to withstand the pressure difference between inside and outside. Thick walls make the equipment heavy and costly. In addition, heat transfer through thick walls is not very efficient and huge, expensive cooling units are required. Concept (2) has the advantage that no thick walls are needed for the enclosure since no pressure difference exists between inside and outside the containment. Cooling is greatly facilitated by thin walls. Disadvantages of concept (2) are that all the components must be free of gas inclusions and compressible voids, otherwise they implode during pressurization and are destroyed. By using the electrically insulating fluid comprising isoparaffin, with advantageous properties at high pressures, i.e. lower viscosity and higher thermal conductivity, than commonly used oils or esters, the subsea installation and operation of insulating fluid containing electrical equipment can be made more reliable

(17) In some embodiments, the electrical equipment is installed below the water/sea surface i.e. subsea, the electrical equipment is an electrical transformer, an electrical motor, a capacitor, a circuit breaker pole, a frequency converter, a reactor or a bushing. The fluid is envisioned to be advantageously used in transformers, but also used in other electrical equipment.

(18) In some embodiments the electrical equipment is installed inside a housing (2) containing the electrically insulating fluid (3) and one or more parts of the electrical equipment are immersed in the insulating fluid (3) and in this case the electrical equipment can be, for example, power electronic modules.

EXAMPLE

(19) The insulating isoparaffin fluid according to the present invention may be a dielectric liquid e.g. fluid, which is derived from terpenes. Dielectric fluids based on terpenes or derived from terpenes (i.e. a fluid according to the present invention) may have the following advantageous properties in addition to a cost that is similar to mineral oil. Renewable feedstock is used High biodegradability (>65%) Excellent kinematic viscosities (adjustable between 2 cSt to >12 cSt at 100° C. and <30 cSt at 40° C.) High flash points (>210° C.) Low pour points (<−30° C.) Better heat transfer capabilities compared to mineral oil Superior oxidation stability Lower viscosity and higher thermal conductivity at high pressures

(20) The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended patent claims.