Frequency Data Analysis - Half Hourly Summaries

Data Quality: Based on the percentage of expected one-second records received: Optimal ≥99%; Operational ≥95% and <99%; Incomplete <95%. Optimal can include small gaps; this describes record availability, not electricity supply quality.

Coverage: Percentage of the period covered by recorded measurement intervals. Missing time is not estimated; overlaps are counted only once. This can differ slightly from the percentage of expected records received.

Samples: Number of valid frequency records used. At one record per second, a full half-hour expects 1,800 records and a full day 86,400.

Largest Gap: Longest continuous time without measurement coverage, including gaps at the start or end of the period.

Within Typical Range: Percentage of recorded frequency values within the Typical Range stored for that period. Missing records are excluded.

Max RoCoF: Largest absolute rate of change of frequency, |f(t) − f(t − Δt)| / Δt, for Δt = 1 or 10 seconds, displayed in mHz/s (1 Hz/s = 1,000 mHz/s), rounded to one decimal place. Evaluated at recorded measurement times within each period; the earlier value is linearly interpolated between adjacent readings for the exact time interval. Windows crossing missing or invalid readings, sequence breaks or timing discontinuities are excluded. No additional smoothing is applied. “—” means no eligible window is available.

Clock Error: Estimated accumulated time gain (+) or loss (−) of a synchronous clock designed for exactly 50 Hz, in milliseconds, over the observed measurement time.

Absolute Deviation: Accumulated magnitude of frequency departure from 50 Hz over the observed measurement time, in Hz·s. Deviations above and below 50 Hz add together rather than cancel.

“—” means the metric is unavailable.