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HI*LITE INSULATORS SAVE ENERGY AND DOLLARS AVOID GENERATING NON-REVENUE POWER ® ® POWER SYSTEMS, INC. Hi-Tension News Reprinted from 9001-H Fall/Wint. 1990 ISO 9001-94 Cert. No. 002196 The Ohio Brass Co. Wadsworth, OH USA ® POWER SYSTEMS, INC. 573-682-5521 ANDERSON Fax 573-682-8714 ® http://www.hubbellpowersystems.com ® ® ® UNITED STATES • 210 N. Allen • Centralia, MO 65240 • Phone: 573-682-5521 • Fax: 573-682-8714 • e-mail: [email protected] CANADA • 870 Brock Road South • Pickering, Ontario L1W 1Z8 • Phone: 905-839-1138 • Fax: 905-831-6353 • e-mail: [email protected] MEXICO • Av. Coyoacan No. 1051 • Col. Del Valle • 03100 Mexico, D.F. • Phone: 525-575-2022 • Fax: 525-559-8626 • e-mail: [email protected] NOTE: Because Ohio Brass has a policy of continuous product improvement, we reserve the right to change design and specifications without notice. © Copyright 2001 • Hubbell/ Ohio Brass Bulletin EU1424-H Printed in U.S.A. Hi*Lite Insulators Save Energy And Dollars – Avoid Generating Non-Revenue Power Your porcelain suspension insulators may be costing you more than you think! Recent test data indicates that Hi*Lite polymer insulators exhibit as much as a 90 percent reduction in energy loss in comparison with equivalent porcelain suspension insulator strings. Similar energy loss ratios have been reported in other industry papers. A series of tests were conducted at the Frank B. Black Research Center to investigate and measure the Power Loss on insulators. Various system voltages were examined as the losses are a function of both voltage and humidity. The results of these tests are shown in Figures 1-5. Curve “A” represents the energy losses associated with porcelain insulator strings and Curve “B” represents the losses associated with Hi*Lite insulators. The shaded area between curves “A” and “B” reflects the difference between real power lost through leakage currents occurring across the insulators. The lower losses associated with Hi*Lite insulators can best be explained as a result of their design. Five factors contribute to the lower energy losses. These factors are: (1) Leakage Distance (2) EP/Silicone Alloy Weathershed Material (3) Core Diameter (4) Electrical Stress Distribution (5) Dielectric and Corona Losses Within the Insulator String Leakage Distance: Hi*Lite insulators contain more inches of leakage distance than an equivalent 2 Figure 1 Figure 2 porcelain insulator string. Based upon an equal insulator wet switching surge strength, Hi*Lite insulators have 14 percent greater leakage distance at 138 kV and a 19 percent greater leakage distance at 500 kV. A longer leakage distance is typically associated with lower leakage currents and, therefore, lower losses. The typical design criteria used for line insulator selection based upon contamination performance calls for no less than 1.0 inch of leakage distance per kV-RMS to ground in clean environments. In areas with moderate contamination conditions, this value is 1.1 to 1.25, and for areas with heavy contamination, a value of 1.5 to 1.75 may be used. Hi*Lite insulators exhibit a level of 1.1 to 1.25 inches of leakage distance which falls into the “Moderate Contamination” level. For heavy contamination areas, additional porcelain units or a longer Hi*Lite unit may be used to obtain the desired leakage distance. EP/Silicone Alloy Weathershed: Hi*Lite insulator weathersheds are molded from a proprietary Ethylene Propylene (EP) material alloyed with Silicone. The EP material has superb tracking resistance, excellent mechanical strength, UV stability exceeding 50 years, and is very resistant to ablation from arcing and ozone conditions. A small amount of Silicone is alloyed with the EP rubber to obtain a long lasting hydrophobic property of the insulator weathershed material. This desirable hydrophobic property is the tendency to repel water, thus preventing moisture from forming a conductive sheet or 3 continuous film across the weathershed. This results in lower leakage currents under wet conditions which correspond to lower energy losses. Another benefit of a hydrophobic surface is a reduction in the capture of airborne contamination. This translates to a cleaner surface which will exhibit lower leakage currents and, therefore, lower energy losses. In contrast, the glaze used on porcelain insulators is hydrophillic, the opposite of hydrophobic. Some utilities apply special coatings to their porcelain insulators to repel water, contamination, and to reduce flashovers caused from excessive leakage currents. Hi*Lite insulators do not need these coatings to obtain these desirable characteristics. In summary, Hi*Lite insulator weathersheds are specially compounded to obtain the hydrophobic properties of a Silicone rubber with the excellent mechanical and electrical properties of an EP rubber. This alloyed rubber limits the energy losses associated with the surface leakage currents. Core Diameter: The small core diameter of Hi*Lite is also a contributing factor to the lower energy losses associated with these polymer insulators. Under wet or contamination conditions, surface leakage currents on Hi*Lite have a greater current density in comparison to the large core diameters associated with porcelain insulators. The higher current density exists while the overall leakage current on the insulator is less than that for porcelain under identical environmental conditions. This 4 higher current density leads to a more rapid drying of the insulator and a more rapid extinction of these surface leakage currents. The overall effect is that the small core diameter of Hi*Lite insulators results in faster drying of the insulator while maintaining a smaller overall leakage current in comparison to the porcelain insulator. Electrical Stress Distribution: In conventional porcelain suspension insulators, pinhole and cap lip corona in the line end units of higher voltage strings will also contribute to the measured energy losses. Changes occur in the voltage distribution of the insulator string as the string becomes wet. This increases corona discharge. There is no corresponding line end corona source on the equivalent Hi*Lite insulator as no intermediate metal fittings exist. The lack of intermediate metal components in Hi*Lite insulators contribute to their overall lower energy losses. Dielectric Losses Within the Insulator: The dielectric material inside Hi*Lite insulators is a solid resin fiberglass core. This material has a dielectric strength of 100 kV/ inch. The fiberglass core runs the entire length of the insulator providing a continuous insulating medium between end fittings. The total insulating material in a 5-3/4 inch section in the middle of the Hi*Lite insulator is 5-3/4 inches. In comparison, porcelain insulators only have approximately 5/8 inch of pure dielectric between the metal cap and pin in a 5-3/4 inch section length. The power factor or dissipation factor of a typical porcelain 5-3/4 inch x 10 inch suspension insulator Polymer and porcelain suspension insulator equivalents. 5 TABLE 6 6 is in the range of 2.0-3.0 percent. The power factor of an equivalent Hi*Lite suspension insulator is approximately 10 percent that of porcelain or 0.2-0.3 percent. While these losses are small, they contribute to the overall insulator energy loss. Converting the Energy Savings to Dollars: The energy losses associated with porcelain and Hi*Lite insulators are a function of humidity and voltage. Since the loss relationship is nonlinear, it is important to evaluate these losses as a function of the time spent at the varying humidity conditions. This will result in a weighted loss evaluation which will most accurately estimate the total losses on an annual basis. (See Table 6.) These losses can then be prorated over the life of the line to obtain a present worth value or savings of these insulators. This present worth may then be used for cost analysis during purchasing, similar to the evaluations conducted on most utility transformer purchases. See Table 7 for an example calculation. A computer program is available from Ohio Brass to assist in this present worth analysis for energy losses. Please contact your local Ohio Brass District Manager or Agent for your free computer diskette. Be sure to specify size, 5.25 inch or 3.5 inch. Polymer insulator application. 7 Present Worth of Savings Calculation Present Worth Savings = [ (Avg Watts) (24 hrs/day) x (365 days/year) (1 kW/1000 watts) (EC $/kW-hr) (P/A) ] EC = Energy Cost in Dollars per kW-hr n n P/A = [ (1 + i) – 1] / [i (1 + i) ] i = Interest Rate (Rate of return for the utility) n = Design Life of the Transmission Line Present Worth Savings = $/Hi*Lite insulator* * This value should be discounted from the purchase price of Hi*Lites at time of bid review. TABLE 7 8