These long, high, thick wires are often described as the highways of our power systems. They connect the big wind farms, hydroelectric plants, solar facilities, and other power plants to the edges of cities, where substations step down the voltage before delivering electricity into homes and businesses along distribution lines that are more akin to city streets.  There are three major grid systems in the US: the Western Interconnection, the Eastern Interconnection, and the Texas Interconnected System. Regional grid operators such as the California Independent System Operator, the Midcontinent Independent System Operator, and the New York Independent System Operator oversee smaller local grids that are connected, to a greater or lesser extent, within those larger networks. Transmission lines that could add significant capacity for sharing electricity back and forth across the nation’s major grid systems are especially valuable for cutting emissions and improving the stability of the power system. That’s because they allow those independent system operators to draw on a far larger pool of electricity sources. So if solar power is fading in one …