Several states shot off letters to power utilities to take steps to deal with the possibility of a sudden drop in electricity demand, which has already dipped by 25 per cent to 125.81 gigawatts due to the lockdown shutting down most businesses.

But what happens when 130 crore Indians switch off lights in their homes at the same time? Speaking to Moneycontrol, a senior executive from the power sector said, “It’s like suddenly putting a brake of a car in motion, or suddenly pushing the accelerator to the floor…it is difficult to predict how the car will exactly behave. It is the same predicament, but much more complicated, that we all are facing.”

Three key players ensure electricity supply to our homes - power generators like Tata Power and NTPC; the distribution companies that each state has; and finally the state load dispatch centres, or SLDCs, who play a critical role in matching the supply, with demand of power. Like the ATC, the SLDC coordinates between generators and distributors to decide how much power is supplied into the grid. A day is divided into 96 time blocks of 15 minutes each, and the SLDC in each state prepares a schedule of demand and supply for every block. SLDC has a very critical role – it has to ensure that the frequency of power that runs in the power grid lines should be between 48.5 and 51.5 hertz. If it goes too high (when the supply is too high) or too low (when the demand goes haywire), then lines can trip, leading to outages. A somewhat similar situation arose during the 2012 blackout - the biggest in the world - when a sudden surge in demand led to tripping and almost 600 million Indians went without electricity.

In order to maintain stability of the power grid, Power System Operation Corporation Ltd (POSOCO) has to manage supply within a frequency range based on projections of demand. If the demand and supply mismatch is large, the grid could trip causing power outages. To manage the sudden drop and then the equally sudden rise within a matter of nine minutes on Sunday, the grid authorities have to ensure that they first reduce electricity supply and then increase it to be able to match the demand at 9.09 pm.

Prime Minister Narendra Modi addressed the nation through a video message at 9 am on Friday, urging the public to switch off the lights for 9 minutes at 9 pm on April 5 and light candles instead. If not candles, torches and mobile flashlights too can be used across balconies and gates to show solidarity in the fight against coronavirus, he said.

Modi’s Friday announcement has prompted sharp reactions from opposition leaders.

Maharashtra Energy Minister Nitin Raut on Friday urged citizens to reconsider Modi’s call to switch off all lights for nine minutes on April 5, saying this could lead to a power grid failure in the country, ANI reported.

Power System Operation Corporation Ltd (POSOCO), the agency responsible for managing electricity grid, said the lighting load of household consumes may be no more than 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,' it said. 'This sharp reduction in load and recovery, which is unprecedented, will need to be handled through hydro and gas resources.'

Its gameplan of managing the sudden change in demand is to reduce hydro power generation during 6:10 pm to 8:00 pm on Sunday and conserve it for providing flexibility during the 9:00 pm event.

Also, coal-based generators as well as gas fired power stations would be scheduled in a manner so as to manage the peak demand.

The switching off of only lights may lead to about 10-15 GW of reduction in electricity consumption out of expected demand of 115-125 GW on Sunday, Ashwini Vaishnav, BJP MP and a bureaucrat who served in Atal Bihari Vajpayee's PMO said.

The government on its part moved to assuage any concerns on this front, saying the call was only for voluntary switching off the lights, and appliances such as computers, TV, refrigerators and ACs are to function normally.

Also, lights in all essential services including hospitals, police stations and manufacturing facilities as well as street lights are not to be switched off.

'Some apprehensions have been expressed that this may cause instability in the grid and fluctuation in voltage which may harm the electrical appliances. These apprehensions are misplaced,' an official statement said. 'The Indian electricity grid is robust and stable and adequate arrangements and protocols are in place to handle the variation in demand.'

It said the appeal of the Prime Minister is to simply switch off the lights in their homes from 9 pm to 9:09 pm on April 5.

'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,' the statement said. 'The lights in hospitals and all other essential services like public utilities, municipal services, offices, police stations, manufacturing facilities, etc will remain on.'

Stating that the Prime Minister has appealed to the people to voluntarily switch off their lights between 9:00 p.m to 9:09 pm, it said all local bodies have been advised to keep the street lights on for public safety.

Union Power Secretary Sanjiv Nandan Sahai also wrote to heads of state power departments, saying 'the National Load Despatch Centre has worked out the procedures for grid balancing during the period which they will be communicating to the regional and state load despatch centres separately.'

He said there is no call to switch off either street lights or appliances in homes. 'Adequate arrangements and protocols are in place to handle the variation in demand. People should be assured not to worry and continue running all appliances as usual.'

A power ministry spokesperson had on Friday said there would be no such impact on grid stability as everything has been taken care of.

Meanwhile, the State Load Dispatch Centre (SLDC) of Uttar Pradesh has written to state utilities to take a series of steps to deal with the possibility of a sudden drop in power demand.

The SLDC in its letter asked the utilities to keep all the reactors of state grid in service while keeping capacitor banks inoperational.

The SLDC has also asked them to start load shedding from 8 pm to 9 pm on Sunday in a staggered manner.

Similar instructions have been given by the Tamil Nadu Transmission Corporation in a letter to its operational executives, saying that availability of sufficient staff should be ensured.

Meanwhile, an official on the condition of anonymity said power demand may fall by 10 GW to 12 GW during the blackout, which will have no bearing on stability of the national power grid.

The official further said this is not the first time the country is going for a blackout, as earlier too such exercises have been conducted for initiatives like 'Earth Hour'.

The Prime Minister's request is for switching off lights at home, and all other appliances will continue to run besides street lights and essential services, he said, adding out of about 115-125 GW expected power demand on Sunday, only about 10-15 GW will reduce by switching off of home lights.

Congress MP Shashi Tharoor and Trinamool MP Mahua Moitra put out acerbic tweets, condoning the prime minister’s appeal.

India has witnessed an unprecedented fall in power demand over the past two weeks of lockdown. Following the announcement of a 21-day lockdown due to the corona pandemic, power demand has fallen by close to 30 per cent during March. According to the power ministry data, the maximum power demand in the country stood at 1,25,817 MW on April 2, almost 20 per cent lower than April 2, 2019 of 1,68,326 MW. This had already put the power sector in a fix to maintain the stability of the grid – a similar but more amplified event is expected when the lockdown ends on April 15.