While gleaning through the Wikipedia article, "Power Outage", I've came up with most of these facts.
A power outage may take one of three forms. 1) Blackout: where power is completely lost. A "rolling blackout" is a common term for a controlled way of rotating available generation capacity between various districts, thus avoiding wide area total blackouts. 2)Brownout: where the voltage level is below the normal minimum level specified for the system. This can be particularly damaging to electric motors. Some brownouts , called voltage reductions, are made to prevent a full power outage. 3)Dropout: where loss of power only lasts seconds.
Power failures are particularly critical for hospitals, since many life critical medical devices and tasks require power. For this reason hospitals, just like many other enterprises have emergency power generators which are typically powdered by diesel fuel. Power outage may also be the cause of sanitary sewer overflow, a condition of discharging raw sewage into the environment (water).
Under certain conditions, a network component shutting down can cause current fluctuations in neighboring segments of the network, though this is unlikely, leading to a cascading failure of a larger system of the network. This may range from a block to an entire city, to the ENTIRE GRID. Modern power systems are designed to be resistant to this sort of cascading failure, but it may be unavoidable. It has recently been argued on the basis of historical data and computer modeling that power grids are self-organized critical systems. These systems exhibit unavoidable disturbances of all sizes, up to the size of the ENTIRE SYSTEM, and any attempts to reduce the probability of small disturbances only increase the probability of the larger ones. Some observers have expressed concern that there is a tendency to erode the resilience of the network over time which is only corrected after the major failure occurs.
Restoring power after wide-area outage can be difficult, as power stations need to be brought back on line. Time being of the essence, before cascading problems amount to insurmountable problems. Normally, this is done with the help from the rest of the grid. In the total absence of grid power, a so-called "black start" needs to be performed to "bootstrap" the power grid into operation.
An example of this power loss through cascading events occurred Aug. 13, 2003. It was the largest blackout in North American history. Effecting 10 million people (1/3 the population) of Canada and 40 million (1/7 the population ) in the U.S., encompassing eight states. During this outage water systems in several cities lost pressure forcing boil water advisories. Cellular telephones experienced significant service disruptions. Most interstate passenger rail transport in the affected areas were shut down and the power outage's impact on international air transport and financial markets were widespread. Meanwhile, the reliability and vulnerability of all electrical power grids was called into question....
At this point we can assume that a threat of the entire grid shutting down is real, it's a possibility. To think that the Northeast Blackout occurred in 2003, leaving 50 million people without power, is fact. I view this threat to our present environment very much as viable as Peak Oil, Climate Change and Financial Collapse.