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Enron Mail |
Ken,
Thanks for the opportunity to review the initial studies performed by the ERCOT System Planning Technical Operations group and to have the opportunity to comment on them at the January 31, 2001 CSC meeting. After I began reviewing the reports that you sent out, I noticed the need for the following items to be addressed quickly in order for all market participants (including ERCOT) to perform meaningful transmission studies: 1) A listing of single element contingencies that PSS/E and/or MUST performs that aren't valid (phantom) contingencies from a physical perspective (i.e. the protection schemes in place would not allow this issue to occur anyway). The easiest to explain example of this situation is when parallel step up transformers are used at a power plant. When one transformer is outaged by automatic single element contingency functions of PSS/E or MUST, the remaining transformer is reported to experience massive overloads that aren't really relevant since the protection scheme in place wouldn't allow this to physically occur. While step up transformers of this nature can easily be screened from the output of PSS/E and MUST, other phantom contingencies that are reported on transmission line outages can't be. This listing of phantom contingencies should be developed and stored in such a fashion that allows it to be included in PSS/E and/or MUST runs as an exception file of contingencies to be ignored. A separate file should be maintained and posted on the ERCOT website for each of the dataset A & B cases that are prepared annually. 2) A listing by load flow bus number of all special contingencies that should be included in PSS/E and/or MUST simulations to reflect the actual response of protection schemes in place needs to be provided by the TPs. A simple example of a special contingency from a PSS/E and/or MUST stand point that is really a single contingency from a physical system stand point is when an autotransformer is connected to the line side of a breaker in a station, rather than to the station bus. PSS/E and MUST needs to be instructed to remove both components at the same time in order to accurately simulate what is really a single contingency from a physical perspective. A separate file should be maintained and posted on the ERCOT website for each of the dataset A & B cases that are prepared annually. 3) A listing by load flow bus number of all double circuit lines that are greater than 0.5 miles in length needs to be provided by the TPs. This listing is needed by market participants to simulate ATC during severe weather situations and for evaluating planned transmission additions using PSS/E and/or MUST. A separate file should be maintained and posted on the ERCOT website for each of the dataset A & B cases that are prepared annually. 4) A listing of valid operator actions that will be taken to alleviate post contingency overloads should be provided by the TPs in a format that is compatible with PSS/E and/or MUST. A separate file should be maintained and posted on the ERCOT website for each of the dataset A & B cases that are prepared annually. In addition, the following requested information would better allow all market participants to understand the planned expansion and operation of the ERCOT transmission system: 1) Prepare an annual transmission plan document that is posted on the ERCOT website which graphically and verbally illustrates the following aspects of proposed projects: location, electrical connectivity (i.e. one-line representation), estimated cost, anticipated system benefits, and proposed in-service date. The projects proposed and described in this expansion plan document should be of the same scope and timing as the ones modeled in the SSTF dataset A & B cases. Ideally, this document would be posted annually on the website at the same time as the dataset A & B cases. The California ISO currently provides this information on their website at the following address: http://www.caiso.com/thegrid/planning/transassessments/. 2) Prepare an annual document that will be posted on the ERCOT website, which explains how the commercially significant constraints (CSCs) will be handled (i.e. preventative generation redispatch or post contingency operator action to reconfigure the transmission system through opening or closing breakers). To the degree that is possible, please include these issues in your agenda for discussion at the January 31, 2001 CSC meeting. Thanks Shannon Caraway, P.E. TXU Energy Trading (214) 875 9397
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