On Sunday (6 April), large parts of India switched off domestic power sources and lighted diyas and candles, coming together in India’s war against coronavirus.

The #9PM9minute event – celebrating a Diwali-like 9-minute night sans the bulbs usually made in China – was quite a success.

When Prime Minister Narendra Modi called for this show of solidarity, newly minted power transmission experts, especially on social media, claimed that Indian grid operations will collapse.

The argument they had was since large parts of the country will switch off their domestic lights suddenly and then switch on again equally rapidly, it would lead to the grid shutting down.

Although the Ministry of Power expressly clarified that this event will not impact the grid, the Power System Operation Corporation Limited (POCOSO) – the public sector unit which manages power supply across all regional power grids in India – ensured that proper planning was in place.

It estimated total load reduction of 12-13 GW on account of domestic lighting switching off. POCOSO released estimates for each of the five regional grids – North, West, South, East and North East – on what load reduction they expected to handle.

Since power has to be consumed once generated – it cannot be stored for most part – any changes to the load on the grid can cause damage to transmission or generation equipment. Thermal power generation systems cannot adjust rapidly to changes in load.

Ahead of the event, POCOSO took actions like switching of some transmission lines while Power Grid and state transmission companies ensured proper working of all relevant equipment.

Starting 6 pm, the hydropower generation was reduced with thermal and gas power sources meeting the peak demand.

Just before the event at 9 pm, the gas and the hydro generating stations were ramped down to basic minimum, so as to reduce the load but also ensuring availability after the event. The thermal generating stations were put back up by 9.05 pm in anticipation of the load increasing.

The initial load on the upside was supported by the hydro stations around 9.09 pm but then thermal stations took over once fully operational.

These measures ensured that the grid stability was maintained throughout and there were no issues either before 9 pm or after 9.09 pm.

The following table indicates the reduction and later the increase of demand starting 8.45 pm across all five regions.