TABLE 61.3 Typical Line Insulation Line Voltage, kV No of Standard Disks Controlling Parameter(Typical Lightning or contamination 2306 Lightning, switching surge, or contamination 24-26 Switching surge or contamination Switching surge or contamination about their use are still under study. Improvements in design and manufacture in recent years have made synthetic insulators increasingly attractive since the strength-to-weight ratio is significantly higher than that of porcelain and can result in reduced tower costs, especially on EHV and UHV transmission lines. NEMA Publication"High Voltage Insulator Standard"and AIEE Standard 41 have been combined in ANSI Standards C29.1 through C29. 9. Standard C29.1 covers all electrical and mechanical tests for all types of insulators. The standards for the various insulators covering flashover voltages(wet, dry, and impulse; radio influence; leakage distance; standard dimensions; and mechanical-strength characteristics)are addressed. These standards should be consulted when specifying or purchasing insulators The electrical strength of line insulation may be determined by power frequency, switching surge, or lightning typical line insulation levels and the controlling ges, different parameters tend to dominate. Table 61.3 shows performance requirements. At different li Defining Term Surge impedance loading(SIL): The surge impedance of a transmission line is the characteristic impedance with resistance set to zero(resistance is assumed small compared to reactance). The power that flows in a lossless transmission line terminated in a resistive load equal to the lines surge impedance is denoted as the surge impedance loading of the line. Related Topics 3.5 Three-Phase Circuits 55.2 Dielectric Losses References Aluminum Electrical Conductor Handbook, 2nd ed. Aluminum Association, 1982. J.R. Carson, Wave propagation in overhead wires with ground return, " Bell System Tech J, vol 5, Pp. 539-554 S. Chen and w. E. Dillon,"Power system modeling, Proc. IEEE, vol 93, no. 7, Pp. 901-915, 1974. E. Clarke, Circuit Analysis of A-C Power Systems, vols. I and 2, New York: Wiley, 1943. Electrical Transmission and Distribution Reference Book, Central Station Engineers of the Westinghouse Electric Corporation, East Pittsburg .E. El-Hawary, Electric Power Systems: Design and Analysis, revised edition, Piscataway, N J. IEEE Press, 199 Further Information Other recommended publications regarding EHV transmission lines include Transmission Line Refe 345 and Above 2nd ed. 1982. from Electric Power Research Institute, Palo Alto, Calif and the ieee Group on Insulator Contamination publication "Application guide for insulators in a contaminated ment, IEEE Trans. Power Appar Syst, September/October 1979 Research on higher voltage levels has been conducted by several organizations: Electric Power Research Institute, Bonneville Power Administration, and others. The use of more than three phases for electric transmission has been studied intensively by sponsors such as the U.S. Department of Energy c 2000 by CRC Press LLC© 2000 by CRC Press LLC about their use are still under study. Improvements in design and manufacture in recent years have made synthetic insulators increasingly attractive since the strength-to-weight ratio is significantly higher than that of porcelain and can result in reduced tower costs, especially on EHV and UHV transmission lines. NEMA Publication “High Voltage Insulator Standard” and AIEE Standard 41 have been combined in ANSI Standards C29.1 through C29.9. Standard C29.1 covers all electrical and mechanical tests for all types of insulators. The standards for the various insulators covering flashover voltages (wet, dry, and impulse; radio influence; leakage distance; standard dimensions; and mechanical-strength characteristics) are addressed. These standards should be consulted when specifying or purchasing insulators. The electrical strength of line insulation may be determined by power frequency, switching surge, or lightning performance requirements. At different line voltages, different parameters tend to dominate. Table 61.3 shows typical line insulation levels and the controlling parameter. Defining Term Surge impedance loading (SIL): The surge impedance of a transmission line is the characteristic impedance with resistance set to zero (resistance is assumed small compared to reactance). The power that flows in a lossless transmission line terminated in a resistive load equal to the line’s surge impedance is denoted as the surge impedance loading of the line. Related Topics 3.5 Three-Phase Circuits • 55.2 Dielectric Losses References Aluminum Electrical Conductor Handbook, 2nd ed., Aluminum Association, 1982. J. R. Carson, “Wave propagation in overhead wires with ground return,” Bell System Tech. J., vol. 5, pp. 539–554, 1926. M. S. Chen and W. E. Dillon, “Power system modeling,” Proc. IEEE, vol. 93, no. 7, pp. 901–915, 1974. E. Clarke, Circuit Analysis of A-C Power Systems, vols. 1 and 2, New York: Wiley, 1943. Electrical Transmission and Distribution Reference Book, Central Station Engineers of the Westinghouse Electric Corporation, East Pittsburgh, Pa. M. E. El-Hawary, Electric Power Systems: Design and Analysis, revised edition, Piscataway, N.J.: IEEE Press, 1995. Further Information Other recommended publications regarding EHV transmission lines include Transmission Line Reference Book, 345 kV and Above, 2nd ed., 1982, from Electric Power Research Institute, Palo Alto, Calif., and the IEEE Working Group on Insulator Contamination publication “Application guide for insulators in a contaminated environ￾ment,” IEEE Trans. Power Appar. Syst., September/October 1979. Research on higher voltage levels has been conducted by several organizations: Electric Power Research Institute, Bonneville Power Administration, and others. The use of more than three phases for electric power transmission has been studied intensively by sponsors such as the U.S. Department of Energy. TABLE 61.3 Typical Line Insulation Line Voltage, kV No. of Standard Disks Controlling Parameter (Typical) 115 7–9 Lightning or contamination 138 7–10 Lightning or contamination 230 11–12 Lightning or contamination 345 16–18 Lightning, switching surge, or contamination 500 24–26 Switching surge or contamination 765 30–37 Switching surge or contamination