Transmission Efficiency Optimization for the operation of double-circuit Overhead Lines

Nowadays the question of improving overhead-line (OHL) operation efficiency is more than ever considered as a very critical issue. This is because power losses have recently acquired an extra cost due to the CO2 release penalty. It is well known that a good portion of the electricity required to operate a power grid is spent as OHL power losses. In this paper the key points of the maximum OHL transmission-efficiency theory are reviewed. OHL loading enabling the maximum transmission efficiency is given. With a case study it is then shown how to optimize the double-circuit OHL transmission-efficiency for the periods of OHL off-peak loading. The OHL transmission-efficiency vs. OHL loading curves of the OHL is presented and the change in the character from capacitive to inductive with an increasing OHL load is illustrated. Potential transmissionefficiency gains in percentage points are calculated. Conclusions of practical importance are drawn both for OHL design purposes as well as for its operation optimization.