Estimated FIs and Preprocessing Publication of estimated FI values AEMO publishes indicative FI values close to real time as it understands this may be useful for Market Participants. These values are to be treated as subject to change because: they are produced by an automated system and not all of the data inputs may be available at the time of publication; FI values are subject to manual verification and checks before applying them in Contribution Factor calculations. Verification and exclusion of FI values An FI may not correlate to the net frequency error in any 4 second period for a number of reasons, including: low pass filtering, smooths any changes to the Regulation FCAS requirement in response to a sharp deviation in frequency; time error correction, which requires the AGC to target the frequency to get to a value other than the nominal frequency. the integral control part of the AGC logic, which adds a component to the Regulation FCAS requirement to correct the long term average of the frequency error; and deadbands applied for stability, which does not respond to small changes in frequency. FI values in any 4 second period are excluded where either: frequency > 50 Hz and FI > 0; or frequency<50Hz and FI <0. If a significant proportion of the 4-second FI values in the same DI are excluded under paragraph (b), all performance data for the relevant DI and area will be excluded from Contribution Factor calculations. If an abnormal frequency island (as defined in the frequency operating standards) forms within an area, separate FI values for each island are not determined and all performance data for the area for the duration of the islanding will be excluded from Contribution Factor calculations. Determine 4-Second Deviation Values Four-second deviations (in MW) are calculated by comparing SCADA measurements against a reference trajectory which differs depending on the deviation source. These calculations are described in the following clauses. Scheduled and semi-scheduled plant The reference trajectory for scheduled generating units, semi-scheduled generating units and scheduled loads is illustrated in Table 2. Table 2 Scheduled generating units, semi-scheduled generating units, and scheduled loads Reference Trajectory Actual Measurement Example
Estimated FIs and Preprocessing Publication of estimated FI values AEMO publishes indicative FI values close to real time as it understands this may be useful for Market Participants. These values are to be treated as subject to change because: they are produced by an automated system and not all of the data inputs may be available at the time of publication; FI values are subject to manual verification and checks before applying them in Contribution Factor calculations. Verification and exclusion of FI values An FI may not correlate to the net frequency error in any 4 second period for a number of reasons, including: low pass filtering, smooths any changes to the Regulation FCAS requirement in response to a sharp deviation in frequency; time error correction, which requires the AGC to target the frequency to get to a value other than the nominal frequency. the integral control part of the AGC logic, which adds a component to the Regulation FCAS requirement to correct the long term average of the frequency error; and deadbands applied for stability, which does not respond to small changes in frequency. FI values in any 4 second period are excluded where either: frequency > 50 Hz and FI > 0; or frequency<50Hz and FI <0. If a significant proportion of the 4-second FI values in the same DI are excluded under paragraph (b), all performance data for the relevant DI and area will be excluded from Contribution Factor calculations. If an abnormal frequency island (as defined in the frequency operating standards) forms within an area, separate FI values for each island are not determined and all performance data for the area for the duration of the islanding will be excluded from Contribution Factor calculations. Determine 4-Second Deviation Values Four-second deviations (in MW) are calculated by comparing SCADA measurements against a reference trajectory which differs depending on the deviation source. These calculations are described in the following clauses. Scheduled and semi-scheduled plant The reference trajectory for scheduled generating units, semi-scheduled generating units and scheduled loads is illustrated in Table 2. Table 2 Scheduled generating units, semi-scheduled generating units, and scheduled loads Reference Trajectory Actual Measurement Example
Regulation-FCAS-Contribution-Factors-Procedure-v2.docx