Research Results and Recommendations for Automatic Processes for Identifying Interconnections Frequency Events and Estimate Frequency Response

There are two objectives for Phase-3 of the DOE-CERTS supported research on Frequency Response performance and reliability standards adequacy. The first Phase-3 objective is to investigate automatic methods to identify interconnections frequency events by extending and validating the approach recommended by Florida Region Representatives and using phasor 1-second frequency data. The second Phase-3 objective is to research a methodology to automatically estimate and validate the Frequency Response for the events identified within the first objective. This is accomplished by: using the Frequency Response Standard Drafting Team (FRSDT) definitions of frequency events for locations of points A, B and C; and the Balancing Authority (BA) with the highest ACE during frequency events or ACE for the contingent BA.

First Objective – Investigate Automatic Methods and Processes to Identify Frequency Events
The team concluded that the method and parameters recommended by the Florida Region, to identify and define Eastern Interconnection frequency events, do not produce a representative and adequate set of frequency events. The team concluded that the method recommended by the Florida Region does produce a representative and adequate set of frequency events if the below 60.00 Hz initial frequency criteria is removed, and the size of the frequency change and/or time window is adjusted for each interconnection. The team further concluded that the proposed method selects events consistent with those manually selected by the Resources Subcommittee for 2008 if the Initial Frequency bounds are removed from the event selection process.

The team recommends an event selection criteria using a 15-second time window for frequency deviations greater than 36, 70, and 90 mHz for the Eastern, Western and Texas Interconnections respectively with 1 second frequency data. The team also recommends that data selection criteria select events that cause frequency to increase as well as decrease to maintain measurement symmetry. In addition, the team advises that the frequency change size and time window duration be reviewed periodically. These parameters should be modified to provide an average number of events per month between four (4) and seven (7) as the additional data is collected and data quality improves.

Second Objective – Investigate Methodology to Estimate and Validate Events Frequency Response
The team concluded there is still a great deal of uncertainty associated with the estimates for Frequency Response on all three interconnections as indicated by the Standard Deviations of the measured Frequency Responses. However, there is reasonable consistency in the mean values for Frequency Response for the years evaluated. This consistency in mean Frequency Response indicates that the measurement methodology is valid.

The team recommends ongoing evaluation and adjustments for the proposed event selection and Frequency Response methodologies as more data is collected and data quality improves. The team recognizes the value of selecting events with appropriate frequency characteristics. However, the team recommends that any event selection process be reviewed carefully to ensure the selection process produces an unbiased sample of frequency events. The potentially dire consequences of relying on biased samples, whether biasing is intentional or not, are well documented.