The state-run Power System Operation Corporation (POSOCO) in its advisory to all states on Saturday clearly said that the reduction in load of the order of 12,000 to 13,000 MW would happen in 2-4 minutes and recover nine minutes later within 2-4 minutes on April 5 in the wake of switching off lights for nine minutes announced by PM Modi. This sharp reduction in load and recovery, which is unprecedented, will need to be handled through hydro and gas resources.
POSOCO has asked that all clocks at generating stations may be synchronized to Indian standard time (IST). During the evening peak hours – from 18.10 to 20.00 hrs- hydro generation will be reduced and conserved for providing flexibility during 2100 hrs event. During this time thermal and gas generation should be scheduled in a manner so as to manage the peak.
Subsequently, after the peak hour, thermal interstate generation stations generation would be gradually reduced to near technical minimum level of 60% by 20.55 hrs and simultaneously hydro generation should be increased to maintain the load generation balance.
Hydro generation and gas generation should be ramped down starting from 20.57 hrs 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 should be ramped down to the minimum level.
Ramping up of thermal machines should be carried out from 21.05 hrs on wards further from 21.09 hrs on wards hydro generation should be ramped up to meet increase in load. After stabilization of system parameters hydro units may be withdrawn in consultation with regional load dispatch centres (RLDCs) and state load dispatch centres (SLDCs).
More importantly, all India grid frequency may be kept at lower side of the Indian Electricity Grid Code (IEGC) band (49.90 Hz) from 20.30 hrs on wards in view of anticipated frequency rise due to demand reduction at 21.0 hrs.
Since COVID-19 containment measures implemented from March 25, nearly 220-240 lines at 400 kV voltage level and above are kept in an open condition for voltage control. System voltages have been within the Indian Electricity Grid Code (IEGC) band. The voltage levels would be within control keeping the generation scheduling.
Notwithstanding these measures, all switching operation of transmission lines, line reactors, and bus reactors should be completed by 20.00 hrs to keep voltage preferably around 760 kV/400 kV respectively on April 5.
Further, POSOCO has told regional and state entities to maintain their interchange with the grid as per schedule. All SLDCs have been asked to advise distribution companies to avoid any feeder switching operation from 20.00 hrs to 22.00 hrs.
All the RLDCs, SLDCs and National Load Dispatch Centre are advised to extend the evening shift timings till 22.00 hrs preferably and allow overlap with the incoming night shift.
PowerGrid Corporation Advisory
The PowerGrid Corporation of India, which is a Central Transmission Utility, in its separate advisory has said that the grid power requirement is likely to reduce on April 5 following switching off lights for 9 minutes. ‘’This may lead to sudden increase in system voltage at various stations can lead to outage of grid element due to grid constraints,’’ added PowerGrid.
PowerGrid Corporation has asked its regional centres to advise all station in charge and Regional Transmission Asset Management Centre (RTAMC) operation staff to be on high alert with required staff. Extreme vigil needs to be maintained and immediate liaison with National Transmission Asset Management Centre (NTAMC) may be made in case of any abnormality/assistance required.
All bus/line reactors should be in service or available for taking into service as per advice of RLDCs and NLDC. Station in charge and senior level executives should be available at their respective station control rooms and respective RTAMC and Central Power Coordination Centre (CPCC) to take care of any contingency and also for smooth coordination with respective RLDCs. Emergency gang/tools and plants, if required, may be tied up in advance.
The precautionary guidelines for COVID-19 regarding use of social distancing and mask should be ensured at all locations.
Meanwhile, the Forum of Load Dispatchers Advisory held an emergency meeting through video conferencing to discuss measures to be taken to ensure the security and reliability of the electricity grid on April 5.
