On 20 October 2011 the Tasmania to Victoria interconnector (Basslink) was taken out of service for planned maintenance work.
The outage caused a failure of AEMO’s Dynamic Security Assessment (DSA) and required a temporary solution in AEMO’s Energy Management System (EMS). The solution, applied from 1037 hrs on 20 October 2011, was only partially completed, and resulted in the Basslink status incorrectly showing Basslink as still in-service until corrected at 1123 hrs that day.
Basslink was returned to service at 1452 hrs on 24 October 2011 and the temporary solution removed, but shortly after there was an EMS database update that resulted in Basslink status reverting to a prior state and incorrectly showing Basslink as still out of service until corrected at 0318 hrs on 26 October 2011.
Basslink status is used by the central dispatch process as an input to the Frequency Control Ancillary Services (FCAS) constraint equations that determine the contingency FCAS requirements in Tasmania for the loss of Basslink.
Consequently, incorrect FCAS was enabled in the Tasmania region for a number of periods between 1510 hrs on 24 October 2011 and 0320 hrs on 26 October 2011.
Under clause 3.8.24 (a)(2) of the National Electricity Rules, AEMO has determined that scheduling errors occurred during the dispatch intervals (DIs) that the incorrect Basslink status was used.
For further information on this document, please contact: Ross Gillett, Electricity Market Performance.