A memo prepared at FERC in late June for Mr. Wellinghoff before he briefed senior officials made several urgent points. "Destroy nine interconnection substations and a transformer manufacturer and the entire United States grid would be down for at least 18 months, probably longer," said the memo, which was reviewed by the Journal. That lengthy outage is possible for several reasons, including that only a handful of U.S. factories build transformers.

"Today’s publication by The Wall Street Journal of sensitive information about the grid undermines the careful work done by professionals who dedicate their careers to providing the American people with a reliable and secure grid. The Wall Street Journal has appropriately declined to identify by name particularly critical substations throughout the country. Nonetheless, the publication of other sensitive information is highly irresponsible. While there may be value in a general discussion of the steps we take to keep the grid safe, the publication of sensitive material about the grid crosses the line from transparency to irresponsibility, and gives those who would do us harm a roadmap to achieve malicious designs. The American people deserve better."

“To address physical vulnerability, it is also important to focus our efforts on modernizing our electric grid. Building the grid of the future will play a key role in addressing multiple security and reliability threats or situations. We should look to further deployment of phasor measurement units, wide-area management systems and enhanced situational awareness. Furthering efforts in the development and deployment of microgrids and smart grid technology will also greatly assist in addressing grid resiliency. These efforts, along with system-wide planning, are just a few examples of how we can increase our ability to make the grid more reliable and efficient.

Because it is difficult to build new transmission routes, existing big substations are becoming more crucial to handling electricity.