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Control Performance Standard 1

CPS1. A standard that measures impact on frequency error.

Definition by NERC

Source: 1 (p29)

  • CPS1 assigns each Control Area a share of the responsibility for control of Interconnection frequency.
  • CPS1 is a yearly (i.e., rolling twelve month) standard that measures impact on frequency error, with a 100 percent minimum allowable score.

Explanation by NERC

Source: 2 (p3)

CPS1 is a:

  • Statistical measure of ACE variability
  • Measure of ACE in combination with the Interconnection’s frequency error
  • Based on an equation derived from frequency-based statistical theory

Simple Calculation by NERC

Source: 1 (p24)

CPS1 captures these relationships using statistical measures to determine each BA’s contribution to such “noise” relative to what is deemed permissible. The CPS1 equation can be simplified as follows:

\[ \text{CPS1} (\text{in percent}) = 100 * \left[ 2 – (\text{Constant}) * (\text{frequency error}) * (\text{ACE}) \right] \]

Tip

The size of this constant changes over time for BAs with variable bias, but the effect can be ignored when considering minute-to-minute operation. It is equal to -10 * B / ε1^2

Calculation by NERC

Source: 3 (p5)

\[ CPS1 = (2 - CF) * 100\% \]

Frequency-related compliance factor (CF)

\[ CF = \frac{CF_{\text{12-month}}}{\epsilon1^2} \]

Where \(\epsilon1\) is a constant derived from a targeted frequency bound for each Interconnection:

  • Eastern Interconnection \(\epsilon1 = 0.018~Hz\)
  • Western Interconnection \(\epsilon1 = 0.0228~Hz\)
  • ERCOT Interconnection \(\epsilon1 = 0.030~Hz\)
  • Quebec Interconnection \(\epsilon1 = 0.021~Hz\)

Warning

A clock-minute average is the average of the reporting Balancing Authority’s valid measured variable (i.e., for Reporting ACE (RACE) and for Frequency Error) for each sampling cycle during a given clock-minute.

Clock-Minute Average of Reporting ACE (RACE)

\[ {\frac{RACE}{-10B}}_{\text{clock-minute}} = \frac{\frac{\sum RACE_{\text{sampling cycles in clock-minute}}}{n_\text{sampling cycles in clock-minute}}}{-10B} \]

Clock-Minute Average of Frequency Error ($ \Delta F_{\text{clock-minute}} $)

\[ \Delta F_{\text{clock-minute}} = \frac{\sum \Delta F_{\text{sampling cycles in clock-minute}}}{n_\text{sampling cycles in clock-minute}} \]

Balancing Authority's Clock-Minute Compliance Factor ($ CF_{\text{clock-minute}} $)

\[ CF_{\text{clock-minute}}= \left[ \left( \frac{RACE}{-10B} \right)_{\text{clock-minut}e} * \Delta F_{\text{clock-minute}} \right] \]

Warning

Normally, 60 clock-minute averages of the reporting Balancing Authority’s Reporting ACE and Frequency Error will be used to compute the hourly average compliance factor

Hourly Average Compliance Factor ($ CF_{\text{clock-hour}} $)

\[ CF_{\text{clock-hour}}=\frac{\sum CF_{\text{clock-minute}}}{n_\text{clock-minute samples in hour}} \]

Warning

The reporting Balancing Authority shall be able to recalculate and store each of the respective clock-hour averages (\(CF_{\text{clock-hour average-month}}\)) and the data samples for each 24-hour period (one for each clock-hour; i.e., hour ending (HE) 0100, HE 0200, ..., HE 2400).

Monthly Compliance Factor (\(CF_{\text{month}}\))

\[ CF_{\text{clock-hour average-month}} = \frac{\sum_{\text{days-in-month}} \left[ \left( CF_\text{clock-hour} \right) \left( n_\text{one-minute samples in clock-hour} \right) \right] }{ \sum_{\text{days-in-month}} \left[n_{\text{one-minute samples in clock-hour}} \right]} \]
\[ CF_{\text{month}} = \frac{\sum_{\text{hours-in-day}} \left[ \left( CF_\text{clock-hour average-month} \right) \left( n_\text{one-minute samples in clock-hour-averages} \right) \right] }{ \sum_{\text{hours-in-day}} \left[n_{\text{one-minute samples in clock-hour averages}} \right]} \]

12-Month Compliance Factor (\(CF_{12-month}\))

\[ CF_{\text{12-month}} = \frac{\sum_{i=1}^{12} (CF_{\text{month-i}}) (n_\text{one-minute samples in month-i})}{\sum_{i=1}^{12} (n_\text{one-minute samples in month-i}) } \]

Warning

To ensure that the average Reporting ACE and Frequency Error calculated for any one-minute interval is representative of that time interval, it is necessary that at least 50 percent of both the Reporting ACE and Frequency Error sample data during the one-minute interval is valid. If the recording of Reporting ACE or Frequency Error is interrupted such that less than 50 percent of the one-minute sample period data is available or valid, then that one-minute interval is excluded from the CPS1 calculation.

Last modified: 2025-11-29

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  1. NERC (2021). Balancing and Frequency Control Reference Document. https://www.nerc.com/comm/RSTC_Reliability_Guidelines/Reference_Document_NERC_Balancing_and_Frequency_Control.pdf ↩↩

  2. NERC (2013). BAL-001-2 - Real Power Balancing Control Performance Standard Background Document. https://www.nerc.com/pa/Stand/Project%202010141%20%20Phase%201%20of%20Balancing%20Authority%20Re/BAL-001-2_Background_%20Document-Clean-20130701.pdf#search=Real%20Power%20%20Balancing%20Control%20%20Performance%20Standard%20Background ↩

  3. NERC (2015). Standard BAL-001-2 - Real Power Balancing Control Performance. https://www.nerc.com/pa/Stand/Reliability%20Standards/BAL-001-2.pdf ↩