Experts believe that while the quantum of power demand reduction can be handled by the grid operator, the rate of change may pose a problem.
Seized of the issue, state run Power System Operation Corp. Ltd (Posoco) that oversees India’s electricity load management functions, in an advisory issued on Saturday, said “It is inferred that total domestic lighting load reduction at all-India level is anticipated to the tune of 12-13 GW. 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."
The advisory was reviewed by Mint.
Posoco manages these complex functions through the National Load Despatch Centre (NLDC). While the regional load despatch centres (RLDCs), responsible for maintaining grid discipline, supervising optimum scheduling and delivery of electricity in their regions, function under Posoco, state load despatch centres (SLDCs) usually act as part of state governments. The country has 33 SLDCs, five RLDCs—for the five regional grids that form the national grid—and one NLDC.
The grid operator will have to manage power projects across coal, gas, hydro, nuclear and green energy sources run by the Centre, states and the private sector. Also, India’s national grid is connected with Bangladesh, Nepal and Bhutan.
“This sharp reduction in load and recovery, which is unprecedented, will need to be handled through hydro and gas resources," Posoco said in the advisory issued to all RLDCs, SLDCs and NLDC.
"Some apprehensions have been expressed that this (the blackout) may cause instability in the grid and fluctuation in voltage which may harm the electrical appliances. These apprehensions are misplaced," the union power ministry said in a statement on Saturday.
“There is no call to switch off either street lights or appliances like computers, TVs, fans, refrigerators and ACs in the homes. Only lights should be switched off," it said, adding that “The lights in hospitals and all other essential services like public utilities, municipal services, offices, police stations, manufacturing facilities, etc will remain on. The call given by Hon’ble PM is to just switch off lights in residences."
“All local bodies have been advised to keep the street lights on for public safety," the statement said.
India’s peak electricity demand has already come down, with commercial and industrial power demand taking a hit after many factories shut down because of the lockdown imposed to check the spread of covid-19 in the country. However, domestic consumption that accounts for around a quarter of India’s power demand has gone up.
Of India’s total electricity demand load pattern, industrial and agricultural consumption account for 41.16% and 17.69% respectively. Commercial electricity consumption accounts for 8.24% of total demand.
“With industrial and commercial down by 50%, the overall demand has fallen by 25%. This blackout will take this remaining 25% domestic demand out. LDCs now need to manage this sharp drop and raise of demand within just a time-block span," said Sambitosh Mohapatra, partner, power and utilities at PwC India.
“I'm guessing LDCs can manage it given we have time to plan unlike a real disaster situation," he added.
Comparisons are been drawn with India’s electricity demand load curve on Sunday, 22 March - the day of the Janata Curfew. India’s power demand on 29 March was around 101,207 MW at 6.07 pm and went up to 112,551 MW at 9 pm during the evening peak load compared with peak electricity demand of about 127.96 GW on 25 March - the day the lockdown began. The demand was about 163.73 GW on 20 March.
India’s peak demand in FY19 was 168.74 GW and touched a record high of 176.72 GW in April last year.
“All-India grid frequency may be kept at lower side of the IEGC (Indian Electricity Grid code) band i.e 49.90 Hz from 20:30 hrs onwards in view of anticipated frequency rise due to demand reduction at 21:00 hrs," the Posoco advisory said.
Grid frequency is a critical aspect of power system operations, with global standards requiring that grid frequency be kept close to 50 hertz (Hz). Any sudden change in demand pattern impacts the grid frequency. India faced massive power transmission failures in July 2012, which left around 700 million people without electricity.
Some experts said it is better to err on the side of caution.
“Posoco and other state grid operators have made all possible precautionary measures in this short notice. They estimated a load reduction of 12.87 GW during this period which in my opinion is very much on the lower side," said Reji Kumar Pillai, president, India Smart Grid Forum and chairman, Global Smart Grid Federation.
“People will switch off other appliances also fearing voltage spikes might damage them. My suggestion is to switch off lights and other appliances one by one from 8.30 pm onwards and switch on one by one by one from 9.10 to 9.45pm," Pillai added.
Apart for asking all generating stations to synchronise their clocks to the Indian standard time (IST) and all RLDCs/SLDCs and NLDC to extend the evening shift timings till 10 pm, and to overlap them with the incoming night shift, the advisory has also called for hydropower generation to be be reduced and conserved during evening peak hours (6.10 pm to 8 pm). Given a hydropower station takes the least possible time to switch on or off, this will help provide 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," the advisory said, adding that “Subsequently after the peak hours, thermal Inter State Generating Stations (ISGS) generation would be gradually reduced to near technical minimum level of 60 % by 20:55 hrs. and simultaneously hydro generation shall be increased to maintain the load generation balance."
India has been in a lockdown since 25 March, which will last until 14 April as of now. Only essential services are allowed to function during the period because of which businesses have shut down and the country has almost ground to a halt.
“Hydro generation and gas generation shall 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 shall be ramped down to the minimum level," the detailed advisory said.
Also, given wind power’s infirm nature of generation, it may be disconnected at the inter- and intra-state transmission level when frequency is more than 50.2 Hz.
A Union government official ruled out any chance of grid instability on Sunday.
India has an installed power generation capacity of 368.69GW, and the national grid is capable of transferring 99,000 mega watts (MW) of electricity from any corner of the country.
“Ramping up of thermal machines shall be carried out from 21:05 hrs onwards. further from 21:09 hrs 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 RLDCs & SLDCs," the advisory said.
India’s per capita power consumption, about 1149 kilowatt-hour (kWh), is among the lowest in the world. In comparison, the world’s per capita consumption is 3600 kWh.
“Perhaps, we are worrying too much as earth hour is for one hour and here we are talking about nine minutes," Mohapatra said.