13:00 voltage profile was before any outages. Figure G.2 also shows a more desired voltage profile of 103 percent (which could be even higher: standard voltage range is 345 kV ± 5 percent). Voltage at the west (left) end near Detroit is very good. Voltage at a large Ohio River power plant on the east end is relatively low. Despite substantial reactive power reserves in the American Electric Power area (Figure G.2) and a 765 kV infeed, voltage at the South Canton bus is poor.
Figure G.3 shows the very low reactive power reserves at power plants in the Cleveland area. Again, the corresponding high reactive power output combined with old excitation equipment caused the initial Eastlake 5 outage. The poor voltage profile contributed to lines sagging into trees (with heating and sagging inversely proportional to voltage squared). Although inadequately discussed in the reports on the August 14, 2003, blackout, the disaster would likely have been avoided with many more capacitors banks in the Cleveland/Akron area. The power system would have been much more robust and resilient.
Example of Special Protection System Implementation
Bonneville Power Administration (BPA) may have the world’s largest implementation of SPSs. The most important SPSs involve the Pacific AC and DC interties, where the main action is tripping of up to 2,700 MW of hydro generation. This is for high power transfer from the Pacific Northwest to California, where the generator tripping prevents instability (loss of synchronousness among generators). Load tripping at the California end would have a similar benefit for stability.
The most complex scheme involves preventing separation of the 4,800 MW Pacific AC inter-tie where high-speed outage detection of around fifty 500 kV lines is installed (detection at both line ends). Outage detection is transmitted over redundant microwave or fiber-optic communications to BPA’s two control centers. Fault tolerant (triple-redundant) programmable logic controllers are at the control centers. Each logic computer has the equivalent of around 1,000 logic gates to detect the many combinations of single, double, and triple line outages in the series/parallel transmission line path. Commands are then sent to generating plants. Besides hydro generation tripping in the Northwest sending end to reduce power transfer, the controls also switch 500 kV capacitor/reactor banks. If an intertie separation does occur, controlled separations of the northern and southern portions of the western interconnection into two electrical islands is initiated. Following a severe outage, control actions are executed in less than a second.
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