Railroads might run commuter trains on 33,000 volts. But households require only 110 volts for small appliances and lights. The transmission and distribution system doesn't rely much on computers. It can be operated manually by technicians who read dials and flip switches. But the network is far-flung, and isolated equipment is vulnerable to attacks or accidents.
Power surges can melt transmission lines.
Electrical arcs between terminals can fuse iron components. Sudden spikes or dips in demand can trigger brownouts. By midmorning on July 6, operators at the Mid-Atlantic grid in Norristown, Pa., saw power demand exceeding their plants' capacity. But it's not too neighborly. Mid-Atlantic had to buy the extra power at prices 30 times higher than the regular rate.