Principal peculiarities of ceramic and composite insulators for overhead EHV/UHV power transmission lines: Electrical characteristics, performance, reliability and application areas

Areas of rational application of cap-and-pin and rod line insulators manufactured of various materials (porcelain, glass and polymers) are discussed in terms of ensuring high reliability and adequate performance of strings on EHV and UHVAC and DC overhead power transmission lines. It is shown that the most critical characteristics of both cap-and-pin and rod units are their quality in terms of annual in-service failure rates and their polluted dielectric strength at long-duration exposure to the operating voltage. Additional features of importance for HVDC lines are high resistivity of the dielectric and good dielectric strength of each individual unit.