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GB System Frequency Excursions - FY1920

  • GB System Frequency Excursions - FY1920

    The National Grid Electricity System Operator (ESO) publishes annually report on the performance of the National Electricity Transmission System in Great Britain and fulfils Transmission Licence Standard Condition C17: Transmission System Security Standard and Quality of Service.

    The Electricity Safety, Quality and Continuity Regulations 2002 permit variations in frequency no exceeding 1% above and below 50Hz: a range of 49.5 to 50.5Hz. Any frequency excursions outside these limits for 60 seconds or more will be reported.

    System Frequency may exceed steady-state operational limits of 49.8Hz and 50.2Hz under fault conditions or when abnormal changes to operating conditions occur. Losses of generation between 1320 and 1800MW are considered abnormal and a maximum frequency change of 0.8Hz may occur, although the operation is managed so that the frequency should return within the lower statutory limit of 49.5Hz within 60 seconds.

    This dataset shows all reportable frequency excursions till date in 2019/2020 based on C17 reporting criteria.

Table Information

Incident date and time

Title Incident date and time
Type datetime
Description Gives the date and time of the start of the excursion in Dth MONTH YEAR, HH:MM format.
Example 9th August 2019, 16:52

Incident Description

Title Incident Description
Type string
Description Provides information on whether the frequency excursion was high or low, and what led to it.
Example Low Frequency Demand Disconnection

Nominal Frequency (Hz)

Title Nominal frequency (Hz)
Type number
Description The frequency that would have been measured if there was no excursion.
Example 50
Unit Hz

Frequency (Hz)

Title Frequency (Hz)
Type number
Description The frequency measured which was furthest away from the nominal frequency during the excursion.
Example 48.8
Unit Hz

Duration (Seconds)

Title Duration (seconds)
Type integer
Description The length of time for which the frequency was deviated from statutory limits.
Example 142
Unit s