The U.S. electric system is in danger of widespread blackouts lasting days, weeks or longer through the destruction of sensitive, hard-to-replace equipment. Yet records are so spotty that no government agency can offer an accurate tally of substation attacks, whether for vandalism, theft or more nefarious purposes. Most substations are unmanned and often protected chiefly by chain-link fences. Many have no electronic security, leaving attacks unnoticed until after the damage is done. Even if there are security cameras, they often prove worthless.