Apart from creating less visual and environmental impact that generates large opposition from local communities, underground cables have several other unique benefits, in particular, they:
- have lower transmission losses;
- can absorb emergency power loads;
- have lower maintenance costs;
- emit no electric field and can be engineered to emit a lower magnetic field than an overhead line;
- require a narrower band of land to install, and;
- are less susceptible to the impacts of severe weather.
Underground cables are - at installation - more expensive than overhead lines and for this reason, EHV underground cables are rarely appropriate for an entire new Alternating Current (AC) power transmission project. Instead, guidelines should be established for the appropriate use of UGCs to balance the needs of economic stakeholders, local communities and the natural environment, notably in sections of projects which have:
- Densely populated urban areas;
- Areas where land is unavailable or planning consent is difficult to obtain within an acceptable timeframe;
- Waterways and other natural obstacles;
- Land with outstanding natural or environmental heritage or vulnerable eco-systems;
- Historically or culturally important sites/buildings;
- Areas of significant or prestigious infrastructure development; and
- Land whose value must be maintained for future urban expansion or rural development.
Major transmission projects require careful analysis and specific solutions. Unless an acceptable overhead route can be found, underground cables are an appropriate solution for sections of a line.