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In the advisory POSOCO said that unlike normal operation, this reduction in load of the order of 12-13 GW would happen in 2-4 minutes and recover nine minutes later within 2-4 minutes.
POSOCO has termed this event ‘unprecedented’ and said it will have to be handled through reduction in generation of hydro and gas resources. According to the advisory, north will witness a 3,436 MW reduction demand, west will witness 3,686 MW reduction demand, south will see a 2,660 MW reduction demand. Eastern region is expected to see a 2,511 mw fall, while north east will witness a 567 mw reduction in demand load.
Highest dip in demand is expected to be witnessed by Uttar Pradesh followed by Maharashtra, estimated at 1865 MW and 1744 MW respectively.
To start with POSOCO has asked all generating stations to synchronize their clocks to the Indian standard time. During evening peak hours — from 6.10 pm to 8 pm, hydro generation will be reduced and conserved for providing flexibility during the 9 pm event.
During this time thermal and gas generation shall be scheduled in a manner so as to manage the peak. Subsequently after the peak hours, thermal inter-state generating stations (ISGS) generation would be gradually reduced to near technical minimum level of 60 % by 8.55PM and simultaneously hydro generation shall be increased to maintain the load generation balance.
Hydro generation and gas generation shall be ramped down starting from 8.57 PM keeping a watch on the system frequency. The hydro units should be kept rolling at 0 – 10 % of the rating and not to be disconnected during this period. Gas station shall be ramped down to the minimum level.
Ramping up of thermal machines will be carried out from 9.05 PM onwards. further from 9.09 PM onwards hydro generation shall be ramped up to meet increase in load. After stabilization of system parameters hydro units may be withdrawn in consultation with regional and state grid systems.
Pumped storage hydro units shall be brought in pumping mode by 8.45 PM and will be kept in service till 9.09 PM. After that, machines shall be withdrawn from the grid through under frequency relays graded between 49.90 to 49.70 Hz amongst the units at each of the pumped hydro stations.
State and inter-state level wind generators will be advised to automatically disconnect the wind generating plants from state and intra-state transmission level when frequency is more than 50.2 Hz.
This over frequency setting may be removed after the event and units synchronized after 9:30 PM. This setting will be implemented at the transmission level sub-stations.
For having a better level of ramping resources, security constrained economic despatch (SCED) may be stopped from 6 PM onwards and would be resumed any time after the event.
All India grid frequency may be kept at lower side of 49.90 Hz from 8.30 PM onwards in view of anticipated frequency rise due to demand reduction at 9 PM.
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