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Enron Mail |
marketrelations@nyiso.com writes to the NYISO_TECH_EXCHANGE Discussion List:
Dear Market Participants Many Market Participants recognized the mismatch in prices which were posted on the NYISO website versus those which were used for billing in the settlement statements. The NYISO has identified the various differences and has modified software necessary to update and / or correct the prices associated with the categories listed below; Upon completion of all the Historical LBMP updates noted below, the NYISO will recompute and post new real time weighted files. Information on what intervals have been changed, as a result of a specific issue noted below, will be provided. Issue #1: Prices and Postings During Reserve Pickup Intervals: During instances where the dispatch interval is in response to a Reserve Pickup request, the price which will be used to bill a Reserve Pickup (RPU) period is the price associated with the most recent normal SCD execution interval preceding the reserve pickup interval. There were limited instances during the first 11 months of operation where an LBMP was incorrectly calculated and posted for the reserve pickup intervals. Solution Issue #1: For the period 11/99 until the present, all RPU intervals that were inadvertently posted with price calculations based on the reserve pickup intervals will be replaced with the price from the dispatch cycle immediately preceding the reserve pickup. Any modifications made which result in changes to the billing data will be corrected through the re-bill and true-up process in future months. Issue #2: Posted Price Discrepancies Between Proxy Bus and Load Bus Prices: During the process of correcting and reposting prices, the Generator or proxy bus prices were updated, but not the Zonal or load prices. Solution Issue #2: ALL proxy gen prices which are different from their corresponding zonal prices, will be copied into the zonal bus prices to overwrite any possible discrepancies between these two files, as these should be identical. NOTE: The Billing & Accounting System (BAS) was coded to use the generator proxy bus price. Therefore the BAS calculations have been consistent with the generator proxy price and should not affect any bills. Issue #3: Missing SCD Intervals In Pass of Data Between SCD and PTS- Due to Loss of Communications: At times there periods exist when communication links between operating systems, namely SCD and Performance Tracking (PTS) in this case, have failed and have to be manually reactivated. During these sub-system failure periods, SCD intervals are being saved and when communications are restored or through the price correction process the SCD intervals are restored. During these failure periods the SCD Start/Stop signals are not being transferred to the PTS. Six-second actual data continues to be received by PTS during these failure periods. PTS develops an average actual value over the SCD interval periods. During the failure periods the PTS observations do not match the number of SCD interval observations. The BAS is coded to ignore any intervals where there is not a match between the price file and the metered MW files. For example, if SCD had intervals for :05, :10 and :15 and the PTS integrated actuals covered the period :05 - :15 then the BAS would calculate the billing based on the consistent sets of data, The interval then becomes a 10 minute interval. Solution Issue #3 The system will be programmed such that it will recognize when an interval is missing in PTS and the PTS interval will be generated by splitting the large interval, with the assumption that the energy was delivered uniformly over the entire interval. Retroactive to Nov'99, the missing intervals will be created. Through the monthly rebill and true-up process, these intervals will be used and billing results may change as a result. Issue #4: Dispatch Interval Type "R" When SCD is in a reserve pickup, and the pick-up is unsuccessful after 10 minutes, an extra PTS interval is generated for performance tracking of units. This interval is not an actual interval where basepoints are calculated and sent to generators. At the time the PTS intervals are sent to the MIS, an LBMP interval is also sent. These intervals were posted on the OASIS and then ignored in BAS. Solution Issue #4 Retroactively to Nov'99, all LBMP intervals generated as part of the reserve pickup performance tracking process will be deleted. In the future, the intervals will not be sent to MIS for posting. Issue #5: Consistent Updated Price Postings Prior to January 2000, intervals updated as part of price corrections were posted to a different spot on the OASIS in a different format, thus making it difficult for market participants to locate the correct data. Solution Issue #5 Retroactively to Nov'99, an update of the current LBMP posting files will be accomplished to include the price corrections not originally posted. The intent of the NYISO is to have all corrections for retroactive price posting discrepancies, and software enhancements completed by the end of Nov 2000.
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