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A Day in the Life of Transmission Congestion

A forecast for California on Aug. 16, 2006

Fortnightly Magazine - May 2005
Figure 3 - Price Contour Map Visualizing Nodal Prices in California

entity). It is also clear that even in one utility's boundary, the variance in nodal prices can be quite high.

Figure 3 illustrates nodal prices at each bus using a price contour map. Different colors are assigned different price ranges. In this figure, blue signifies an area where nodal prices are $10/MWh or less and red signifies prices $50/MWh or more. The legend in Figure 3 provides the range of nodal prices assigned to each color. The four price snapshots assist in visualizing nodal prices throughout one day in August 2006.

  • 1 a.m. : No congestion is present. The figure shows nodal prices at the beginning of the day (1 AM) at a homogenous low price. In this hour, no congestion is present. The green areas represent a transmission region where no bus pricing information is available.
  • 7 a.m. : Congestion is present. Higher prices begin to develop in Northern California, while Southern California prices increase—albeit at a lower level—and a generation pocket in the Monterey, Calif., area results in much lower prices than other areas in California.
  • 2 p.m. : Nodal prices increase throughout California; congestion remains. Color-differentiated congestion is present throughout the transmission network since the red shaded areas only signify higher prices and do not differentiate the congestion present within the red shaded areas.
  • 12 p.m. : Nodal prices decrease throughout California. While congestion still remains, as evidenced by pricing in Northern California being higher than Southern California, nodal prices have decreased significantly from their peak-period prices.