What happens when 130 crore Indians switch off lights in their homes, together?

That's the question that engineers in India's power sector are now grappling with, after Prime Minister Narendra Modi called upon the nation to do so, in solidarity amidst the COVID-19 crisis.

"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," said a senior executive from the power sector.

According to industry executives, they have two days time to plan for those nine minutes. "It is a challenge, and something unprecedented. But it is possible," said another executive from the industry.

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To clearly understand the challenge, one needs to know how the power sector functions.

How you get electricity?

Three important stakeholders come to play to ensure electricity reaches 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.

"It's like you have the aircraft, airport and the ATC. The SLDC functions like the ATC, which ensures aircraft take off and land smoothly and without any delay," explained Gopal Jain, Senior Advocate, Supreme Court of India, and advises on regulatory and policy matters

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.

"It is a highly automated and scientific process," added Sitesh Mukherjee, a lawyer specialising in infrastructure regulatory disputes.

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," he said.

Something similar to what happened in 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.

Controlling supply

On April 5, instead of demand, the danger is of supply surging and disrupting the frequency when Indians switch off lights all at once at 9 pm. This could trip the line, and lead to a blackout.

But, assure senior engineers in the sector, it can be handled as they have the time to plan.

The critical part is to manage the supply.

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India gets power from different sources - thermal, hydel, gas, wind and solar. Which of these sources can be adjusted to reduce the supply?

"Solar doesn't generate in the night. Wind is continuous and can't be stopped. But it is possible to completely shut down a hydel and gas plant," said an engineer. And it is not a herculean task to restart a hydel or gas plant.

Not so with a thermal plant. "It can take hours to restart a thermal plant," said an executive.

Fortunately, because of the coronavirus impact, thermal plants are already running on low capacity. At the same time, they can't be shut completely to reduce the supply on April 5. What they can do is to keep capacity utilisation at the lowest for those nine minutes on Sunday.

"From the moment the Prime Minister made the announcement, the stakeholders - power generators, DISCOMs and SLDCs - have started planning for Sunday," said one of the senior executives quoted above.

Nine minutes

The nine minutes are a challenge because it doesn't constitute a time block of 15 minutes, and the sophisticated systems can't be re-configured at a short notice.

What will help the industry is that on April 5, it will be only the lights that will go off. "People won't switch off fans or air conditioners. Also, street lights and those in other public places will be on. Moreover, there will be some percentage of people who will forget to switch off!" says an engineer.

Executives in the industry expect the fluctuation to be of about 9-10 percent of the total power requirement. "It is not very high. At the same time, adjusting the electricity supply won't be easy. It is a challenge, says an executive.

Particularly challenging could be the 10th minute, when everyone probably will put on the lights again. Will the supply meet the sudden spurt in demand?

"It will be interesting to know," is how one executive put it.

With inputs from Jitendra Gupa