Tree planting, as related to power lines, is a science and Northern Neck Electric Cooperative has a handy guide for tree planting and explains it in the news item Right Tree, Right Place.
The key takeaways:
Be sure to consider the mature height of the tree when determining a suitable planting location. Native species often will grow better with fewer insect and disease problems than non-native trees. For areas near houses and overhead utilities, there are tree height zones.
Low Tree Zone - Only plant trees with a mature height of 15 feet or less within 20 feet of power lines.
Medium Tree Zone - Plant trees that will be shorter than 40 feet when mature can be planted at least 25 feet from power lines.
Large Tree Zone - Plant all trees over 40 feet at least 50 feet away from power lines.