Per-unit power costs of traditional and innovative OHLs: a multi-criteria comparison

The need to increase power transmission capability in electrical power systems led to the proposal of possible alternatives to the traditional three-phase (3P) AC overhead transmission lines (OHLs). In addition to high-voltage DC connections, the alternatives include non-conventional solutions such as 4P AC lines and combined AC–DC lines. All these solutions have been examined in recent works where, however, the technical and economic aspects are usually separately analysed. On the contrary, a proper comparison among different solutions requires a combined technical–economic evaluation and, therefore, a systematic methodology based on a multi-criteria approach. This study compares the various possible OHL solutions resorting to an original methodology that joins technical and economic aspects. The former are taken into account by means of the loadability curves (properly computed for each solution). The latter include various cost items (for investment, energy losses, reliability and land occupation) computed for each solution. The different aspects are joined by computing the per-unit-of-transportable-power cost of each solution. This parameter provides, for any given line length, a total cost normalised in terms of the theoretical transmission capability of each solution and, thus, an interesting comparison tool among different solutions.