1. The electric system was originally built as many local or regional grids, linking generators to loads. 2. Local grids were joined to improve reliability and lower costs by sharing generation. 3. With the development of power trading markets and long- distance backbone transmission lines, the US and Canada evolved into 3 large regional interconnections. 4. 640,000 mi network linking over 75,000 MW of generation to millions of customers served by 3,000 utilities.
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