M-4 Interconnection Frequency Response



About This Metric​
This metric is used to track and monitor Interconnection Frequency Response. Frequency Response is a measure of an Interconnection’s ability to stabilize frequency immediately following the sudden loss of generation or load. It is defined as sum of the change in demand, plus the change in generation, divided by the change in frequency, expressed in megawatts per 0.1 Hertz (MW/0.1 Hz). It is a critical component to the reliable operation of the bulk power system, particularly during disturbances and restoration. The metric measures the average Frequency Response for all events where frequency drops more than the Interconnection’s defined threshold. While the calculations may show trends from year to year, no attempt has been made in this analysis to determine or state what indicates an “acceptable” level of Frequency Response for any of the interconnections. Rather, they show the relative performance from year-to-year and can be a basis for further root-cause analysis. Further, the Frequency Response should not be compared between interconnections as their bulk power system characteristics differ significantly in terms of number of facilities, miles of line, operating principles and simple physical, geographic and climatic conditions. Some annualized Frequency Responses are higher due to the large number of disturbances in the dataset where frequency changes were greater than the generator deadbands.

The chart shows the Frequency Response of 163 events in the Eastern Interconnection. A linear regression equation is an adequate statistical model to describe a relationship between time (predictor) and Frequency Response (response variable). The graph of the linear regression line and Frequency Response scatter plot is given in the chart. For the dataset, the regression line has a small positive slope estimate, meaning that the Frequency Response variable has a slowly increasing general trend in time. The value of the slope estimate is 0.00000303805 (the time unit is a second). This means that, on average, Frequency Response increases daily by 0.26 MW/0.1Hz, monthly by 7.87 MW/0.1 Hz, and annually by 95.81 MW/ 0.1Hz (for a month with 30 days , and a year with 365 days).

Metric Definition Document
M-4 Interconnection Frequency Response​