Synchrophasor Initiative in India - erldc

SYNCHROPHASORS - INITIATIVE IN INDIA JUNE 20125.6.9 Case Study-37: Study of Ringdown oscillations during event on 19-Apr-2012The case was examined by studying the Ringdown oscillation due to tripping of Anpara andRihand units in the early morning of 19 th April 2012. The total generation loss was around 1600MW with the tripping of Anpara 1, 2, 3(3x200 MW) and Rihand 1, 2 (2x500 MW) units. The dropin frequency was from 50 Hz to 49.2 Hz.From the SOE it was observed that following incidences occurred:• 400kV Anpara-Varanasi line-2 - 0 3:24:43.916 hrs (Varanasi end)• Unit#1 at Rihand STPS - 03:29:02.393 hrs• Unit#2 at Rihand STPS - 03:30:53:626 hrsTripping of Anpara TPS could not be confirmed from U.P SOE. NRLDC SOE does not revealany tripping at above mentioned time. Anpara TPS informed that tripping of Anpara-A unitsoccurred at 03:29hrs but did not substantiate.Figure 124: PMU plot for Vindhyachal frequency showing the three incidencesFrom the SOE and PMU plot shown above, three time intervals has to be analysed for properinvestigation of Ringdown oscillation.Duration 1 : 03:24:44.000 Hrs - 03:24:48.960 Hr (Tripping of 400kV Anpara-Varanasi line-2)Duration 2 : 03:29:02.600 Hrs - 03:29:11.960 Hrs (Tripping of Rihand Unit 1 )Duration 3 : 03:30:52.000 Hrs - 03:30:55.960 Hrs (Tripping of Rihand Unit 2 )POSOCO Page 120 of 143