Patent Application
20140238867
The present disclosure generally relates to a coated overhead conductor which better radiates heat away, thereby reducing operating temperature.
As the need for electricity continues to grow, the need for higher capacity transmission and distribution lines grows as well. The amount of power a transmission line can deliver is dependent on the current-carrying capacity (ampacity) of the line. For a given size of the conductor, the ampacity of the line is limited by the maximum safe operating temperature of the bare conductor that carries the current. Exceeding this temperature can result in damage to the conductor or the accessories of the line. Moreover, the conductor gets heated by Ohmic losses and solar heat and cooled by conduction, convection and radiation. The amount of heat generated due to Ohmic losses depends on current (I) passing through the conductor and its electrical resistance (R) by the relationship—Ohmic losses=I2R. Electrical resistance (R) itself depends on temperature. Higher current and temperature lead to higher electrical resistance, which, in turn, leads to more electrical losses in the conductor.
In accordance with one embodiment, a coated overhead conductor includes an assembly including one or more conductive wires. The assembly also includes an outer surface coated with an electrochemical deposition coating forming an outer layer. The electrochemical deposition coating includes a first metal oxide. The first metal oxide is not aluminum oxide.
In accordance with another embodiment, a method of making a coated overhead conductor includes providing a bare conductor and performing electrochemical deposition of a first metal oxide on an outer surface of the bare conductor to form an outer layer on the bare conductor. The outer layer includes an electrochemical deposition coating. The first metal oxide is not aluminum oxide.
In accordance with yet another embodiment, a coated overhead conductor includes an assembly including one or more conductive wires. The one or more conductive wires are formed of aluminum or aluminum alloy. The assembly includes an outer surface coated with an electrochemical deposition coating forming an outer layer. The electrochemical deposition coating includes titanium oxide, zirconium oxide or combinations thereof. The outer layer has a thickness from about 5 microns to about 25 microns.
Various embodiments will become better understood with regard to the following description, appended claims and accompanying drawings wherein:
Selected embodiments are hereinafter described in detail in connection with the views and examples of
Metal oxide coated overhead conductors, when tested in under similar current and ambient conditions, can have a reduced operating temperature by at least 5° C. compared to the temperature of the same conductor without the surface modification.
Accordingly, it can be desirable to provide a modified overhead conductor that operates at significantly lower temperatures compared to an unmodified overhead conductor that operates under the same operating conditions, such as current and ambient conditions. Such a modified overhead conductor can have a coating of metal oxide other than aluminum oxide, such that when tested under similar current and ambient conditions, has a reduced operating temperature by at least 5° C. compared to the operating temperature of the same conductor without the coating. At higher operating temperatures, e.g. above 100° C., a coated conductor can have a reduction of at least 10° C. when compared to an uncoated conductor when tested under similar current and ambient conditions (e.g., operating conditions).
Overhead conductors can be coated using a variety of techniques; however, one advantageous method includes coating the overhead conductor via electrochemical deposition with a metal oxide on the surface of the overhead conductor. The method can contain the steps of:
Suitable pre-treatment for a surface of an overhead conductor can include hot water cleaning, ultrasonic, de-glaring, sandblasting, chemicals (like alkaline or acidic), and others or a combination of the above methods. The pre-treatment process can be used to remove dirt, dust, and oil for preparing the surface of the overhead conductor for electrochemical deposition.
The overhead conductor can be made of conductive wires of metal or metal alloy. Examples include copper and aluminum and the respective alloys. Aluminum and its alloys are advantageous for an overhead conductor due to their lighter weight.
Electrochemical deposition of a metal oxide is one method for coating the surface of an overhead conductor. Electrochemical coating compositions using an electrochemical deposition process can include, for example, those found in U.S. Pat. Nos. 8,361,630, 7,820,300, 6,797,147 and 6,916,414; U.S. Patent Application Publication Nos. 2010/0252241, 2008/0210567, 2007/0148479; and WO 2006/136335A1; which are each incorporated herein by reference in their entirety.
One method for forming a metal oxide coated aluminum overhead conductor can include the steps of: providing an anodizing solution comprising an aqueous water soluble complex of fluoride and/or oxyfluoride of a metal ion selected from one or more of titanium, zirconium, zinc, vanadium, hafnium, tin, germanium, niobium, nickel, magnesium, berrilium, cerium, gallium, iron, yttrium and boron, placing a cathode in the anodizing solution, placing the surface of the overhead conductor as an anode in the anodizing solution, applying a current across the cathode and the anode through the anodizing solution for a period of time effective to coat the aluminum surface, at least partially, with a metal oxide on the surface of the surface of the conductor to form a coating. Such coatings having a metal oxide can include a ceramic coating.
In one embodiment, electrochemical deposition of the coating includes maintaining an anodizing solution at a temperature between 0° C. and 90° C.; immersing at least a portion of the surface of the overhead conductor in the anodizing solution; and applying a voltage to the overhead conductor. The anodizing solution can be contained within a bath or a tank.
The current passed through a cathode, anode and anodizing solution can include pulsed direct current, non-pulsed direct current and/or alternating current. When using pulsed current, an average voltage potential can generally be not in excess of 600 volts. When using direct current (DC), suitable range is 10 to 400 Amps/square foot and 150 to 600 volts. In a certain embodiment, the current is pulsed with an average voltage of the pulsed direct current is in a range of 150 to 600 volts; in a certain embodiment in a range of 250 to 500 volts; in a certain embodiment in a range of 450 volts. Non-pulsed direct current is desirably used in the range of 200-600 volts.
A number of different types of anodizing solutions can be used. For example, a wide variety of water-soluble or water-dispersible anionic species containing metal, metalloid, and/or non-metal elements are suitable for use as components of the anodizing solution. Representative elements can include, for example, titanium, zirconium, zinc, vanadium, hafnium, tin, germanium, niobium, nickel, magnesium, berrilium, cerium, gallium, iron, yttrium and boron and the like (including combinations of such elements). In certain embodiments, components of the anodizing solution are titanium and/or zirconium.
In one embodiment, the anodizing solution can contain water and at least one complex fluoride or oxyfluoride of an element selected from the group consisting of titanium, zirconium, zinc, vanadium, hafnium, tin, germanium, niobium, nickel, magnesium, berrilium, cerium, gallium, iron, yttrium and boron. In certain embodiments such elements are titanium and/or zirconium. In certain embodiments, the coating can further contain IR reflective pigments.
In another embodiment, a method for making an overhead conductor can include providing of a metal oxide coating. The method can include providing an anodizing solution containing water, a phosphorus containing acid and/or salt, and one or more additional components selected from the group consisting of: water-soluble complex fluorides, water-soluble complex oxyfluorides, water-dispersible complex fluorides, and water-dispersible complex oxyfluorides of elements selected from the group consisting of titanium and zirconium, placing a cathode in the anodizing solution, placing the overhead conductor having a surface of an aluminum or aluminum alloy as an anode in the anodizing solution, passing a pulsed current across the cathode and the anode through the anodizing solution for a period of time effective to form a titanium oxide or zirconium oxide coating on at least a surface of the overhead conductor.
Electrochemical deposition of a metal oxide coating can be achieved either directly on the finished conductor or coating individual conductive wires separately before stranding the coated individual wires to make the overhead conductor. In certain embodiments, it is possible to have all of the wires of the conductor surface coated, or more economically, via another embodiment, only having the outer most wires of the conductor surface coated. In another embodiment, the electrochemical deposition coating can be applied only to the outer surface of the overhead conductor. Here, the conductor itself is stranded and made into final form before electrochemical deposition. Electrochemical deposition can be done by batch process, semi-continuous process, continuous process, or combinations of these processes.
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Composite core conductors can beneficially provide lower sag at higher operating temperatures and higher strength to weight ratio. Reduced conductor operating temperatures due to surface modification can further lower sag of the conductors and lower degradation of polymer resin in the composite core.
The surface modification described herein can also be applied in association with conductor accessories and overhead conductor electrical transmission related products and parts, for the purpose of achieving temperature reduction. Examples include deadends/termination products, splices/joints products, suspension and support products, motion control/vibration products (also called dampers), guying products, wildlife protection and deterrent products, conductor and compression fitting repair parts, substation products, clamps and other transmission and distribution accessories. Such products are commercially available from a number of manufacturers such as Preformed Line Products (PLP), Cleveland, Ohio, and AFL, Duncan, S.C.
The electrochemical deposition coating can have a desired thickness on the surface of the overhead conductor. In certain embodiments, this thickness can be from about 1 micron to about 100 microns; in certain embodiments from about 1 micron to about 25 microns; and in certain embodiments, from about 5 microns to about 20 microns. The thickness of the coating can be surprisingly even along the conductor. For example, in certain embodiments, the thickness can have a variation of about 3 microns or less; in certain embodiments, of about 2 microns or less; and in certain embodiments, of about 1 micron or less. Such electrochemical deposition coatings as described herein can be non-white in color. In certain embodiments, the color of the electrochemical deposition coatings can range in color from blue-grey and light grey to charcoal grey depending upon the coating thickness and relative amounts of metal oxides, such as titanium oxide and/or zinc oxide. In certain embodiments, such coatings can also be electrically non-conductive. As used herein, “electrically non-conductive” means volume resistivity greater than or equal to 1×104 ohm-cm.
Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the coatings and overhead conductors as described herein and practice the claimed methods. The following examples are given to further illustrate the claimed invention. It should be understood that the claimed invention is not to be limited to the specific conditions or details described in the cited examples.
An experimental set-up to measure the effectiveness of an electrochemical deposition coating to reduce operating temperature of a conductor is prepared as described below. A current is applied through coated and uncoated samples. The coated sample can be a metal oxide coated aluminum or aluminum alloy substrate. The uncoated sample can be a similar aluminum or aluminum alloy substrate, but uncoated. The test apparatus is shown in
The sample to be tested was connected in series with the AC current source through a relay contact controlled by the timer. The timer was used to control the time duration of the test. The 60 Hz AC current flowing through the sample was monitored by the true RMS clamp-on current meter. A thermocouple was used to measure the surface temperature of the sample. Using a spring clamp, the tip of the thermocouple was kept firmly in contact with the center surface of the sample. The thermocouple was monitored by the temperature datalog recording device to provide a continuous record of temperature.
Both uncoated and coated substrate samples were tested for temperature rise on this experimental set-up under identical conditions. The current was set at a desired level and was monitored during the test to ensure that a constant current was flowing through the samples. The timer was set at a desired value; and the temperature datalog recording device was set to record temperature at a recording interval of one reading per second.
The metal component for the uncoated and coated samples was from the same source material and lot of Aluminum 1350. The finished dimensions of the uncoated sample was 12.0″(L)×0.50″(W)×0.027″(T). The finished dimensions of the coated sample was 12.0″(L)×0.50″(W)×0.028″(T). The increase in thickness was due to the thickness of the applied coating.
The uncoated sample was firmly placed into the test set-up and the thermocouple secured to the center portion of the sample. Once this was completed, the current source was switched on and was adjusted to the required ampacity load level. Once this was achieved the power was switched off. For the test itself, once the timer and the temperature datalog recording device were all properly set, the timer was turned on to activate the current source starting the test. The desired current flowed through the sample and the temperature started rising. The surface temperature change of the sample was automatically recorded by the temperature datalog recording device. Once the testing period was completed, the timer automatically shut down the current source ending the test.
Once the uncoated sample was tested, it was removed from the set-up and replaced by the coated sample. The testing resumed making no adjustments to the AC current source. The same current level was passed through the uncoated and coated samples.
The temperature test data was then accessed from the temperature datalog recording device and analyzed using a computer. Comparing the results from the uncoated sample test with that from the coated test was used to determine the comparative emissivity effectiveness of the coating material.
To study thermal stability of an electrochemical deposition coating, coated samples were places in air circulation oven at a temperature of 325° C. for a period of 1 day and 7 days. After the thermal aging was complete, the samples were placed at room temperature for a period of 24 hrs. The samples were then bent on different cylindrical mandrels sized from larger diameter to smaller diameter and the coatings were observed for any visible cracks at each of the mandrel sizes. Results were compared with the flexibility of the coating prior to thermal aging.
Uncoated strips of aluminum (ASTM grade 1350; Dimensions: 12.0″(L)×0.50″(W)×0.028″(T)) were tested for operating temperature as per the test method described above. The test set up is illustrated in
The same strips of aluminum described in Comparative Example 1 were coated with an electrochemical deposition coating of titanium oxide (commercially available as Alodine EC2 from Henkel Corporation). The sample dimensions prior to coating were 12.0″(L)×0.50″(W)×0.028″(T). The thickness of the coating was 12-15 microns. The sample was then tested for reduction in operating temperature by the test method described above. The titanium oxide coated sample was found to demonstrate significantly lower operating temperature compared to the uncoated sample (Comparative Example 1), as summarized in Table 1 below.
The same strips of aluminum described in Comparative Example 1 were anodized. The anodized layer thickness was 8-10 microns. The flexibility of the anodized coating was tested by performing the mandrel bend test as described above. The flexibility test was also conducted after thermal aging at 325° C. for 1 day and 7 days.
The same strips of aluminum described in Comparative Example 1 were coated with a coating containing 40% sodium silicate solution in water (75% by weight) and zinc oxide (25% by weight) by brush application. The coating thickness was about 20 microns. Flexibility of the coating was tested by performing the mandrel bend test as described above. The flexibility test was also conducted after thermal aging at 325° C. for 1 day and 7 days.
The flexibility test data is summarized in Table 2 below. The sample with the electrochemically deposited titanium oxide coating showed significantly better flexibility compared to each of the anodized coating and the sodium silicate with ZnO brush coating. Moreover there was no change in the flexibility of the titanium oxide coating with thermal aging at 325° C. for 1 and 7 days.
While particular embodiments have been chosen to illustrate the claimed invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the claimed invention as defined in the appended claims.
The present application claims priority of U.S. provisional application Ser. No. 61/769,492, filed Feb. 26, 2013, and hereby incorporates the same application herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61769492 | Feb 2013 | US |
