ABSTRACT
Modern electric power systems are oµen characterized by generating stations located far away from the consumption centers, with long overhead transmission lines to transmit the energy from the generating sites to the load centers. From the few tens of kilovolts in the early years of the twentieth century, the line voltage has reached the extra-high voltage (EHV) levels of 800 kV AC (Lacroix and Charbonneau, 1968) and 500 kV DC (Bateman et al., 1969) in the 1970s, and touched the ultrahigh voltage (UHV) levels of 1200 kV AC (Bortnik et al., 1988) and 600 kV DC (Krishnayya et al., 1988). Although overhead lines operating at high voltages are the most economical means of transmitting large amounts of energy over long distances, their exposure to atmospheric conditions constantly alters the surface conditions of the conductors and causes large variations in the corona activities on the line conductors.
