Isn’t an underground line more reliable?

While it seems overhead transmission lines would have significantly more outages than underground installations, this is not necessarily true, particularly with larger transmission lines. The larger bulk transmission lines are designed to withstand extreme weather conditions expected in the region and the lines are built on right of ways that are kept clear of trees that could interfere with the line. When outages occur on aerial transmission lines, they can be repaired in a relatively short amount of time. When an outage occurs on underground lines the restoration time and cost is significantly higher. There can also be significant ground disturbance as the damaged cable is located, uncovered, and repaired. Back to top.