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Year 2000 Issues for the Electric Utility Industry 6 <br />How DATE USAGE CREATES PROBLEMS <br />In Figure 3 a layout is shown for a typical power plant. Each of these scenarios can <br />cause date -related problems: <br />■ Problems at a lower level can infect the higher-level systems <br />■ The greatest problems tend to be with controller codes, interface codes, custom <br />communications codes, and decision codes. <br />■ A lower level embedded device has problems due to date logic in its microcode. In <br />this case its function was not so critical but the device did generate a bad date stamp <br />that was fed back into the SCADA system, which sorted the record erroneously. <br />This later caused erroneous trend analysis. <br />■ Another example is a valve that shut down from failed communications with its <br />DCS. This is a critical process that could cause a plant trip. <br />■ One of the operator terminals is having problems displaying some of the dates it has <br />received through the SCADA system. The operator.is not sure how to interpret the <br />date and has begun to manually enter his own. <br />• One of the higher-level PCs has lost its network link because its particular <br />communications package is not compliant and has failed. <br />4 <br />■ Finally, a few applications of the plant management "host" computer have locked up <br />trying to generate new schedules. Control begins to quickly deteriorate as the ripple <br />effects kick in, resulting in the source and root causes of the problems being lost. <br />Some of the bad data and schedule information starts being fed to others. <br />Copyright 1998, TAVA/R. W. BeckLLc <br />All rights reserved. NAVA R W BECK <br />