Slide Image: A visualization map shows the relative voltage levels in the high voltage electric transmission system in the New York and New England areas of the United States.

In the upper left corner is a color key entitled, "Voltage Magnit…" The scale goes from a low of 0.950 pu to a mid range of 1.000 pu to a high of 1.050 pu.

The lowest level areas on the map are along the New York-Pennsylvania border and in upper Vermont. The highest level is along the coast of Maine. The dots on the map called "buses" are junction points where a number of transmission lines join together.

Using color voltage contours in electric utility control centers can help provide the people operating the transmission system with an early warning of these conditions.

Credit: Tom Overbye, University of Illinois at Urbana Champaign