This Sunday (April 5) at 9 PM, crores of us are going to switch off lights at once to participate in Modi's 'Diya' call. This has become a headache of sorts for the power industry! The power sector, say technical experts, has been engaged in a massive preparation exercise to prevent power outages on a large scale because of the 9 PM exercise.

Here is what is problematic about everyone switching off lights at 9 PM. Engineers say that there should always be a match in the supply with demand for power. State load dispatch centres (SLDCs) take care of this aspect.

"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," says a report published by Money Control. The supply of power will be constant from 9 PM. However, with everyone switching off lights, the demand will drastically go down.

What happens when this balance gets upset? Lines will trip, resulting in outages.

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

The SLDCs, together with power generators and distribution companies, are planning for the 9 PM event to avoid the tripping of lines. Engineers are hoping that the problem won't be unmanageable because we won't be switching off fans, air conditioners, etc. Even street lights will be on.

Electricity boards are already in preparation mode:

Writes journalist Arvind Gunasekar," Due to Modi’s call for switching off of lights for 9 mins on April 5, load is expected to have a steep fall at 9 PM and a steep rise around 9.09 PM... To keep the Power Grid safe, load shedding in a staggered manner from 8-9 PM is advised...men on standby."