For power sector professionals and enthusiasts in India, ‘The 9 Minutes Lights Off’ event on Sunday, 5 April 2020 was equivalent to a celestial event for astronomy. What made the event very unique is there is no known precedent of about 25 per cent power demand switching off and coming back up in matter of less than 20 minutes in a large and complex interconnected power grid.

Key Concern

The general discourse in the country was the event would result in grid failure, blackout, damage to equipment, essential medical equipment losing functionality etc.

While a lot of people supported the event as a signal of national solidarity and resolve, others questioned the need to conduct such an exercise when the country is facing a pandemic.

Though the officials and grid operators put up a brave face, there was certainly a lot of anxiety whether the event would pass off without a glitch.

While some of the concerns were valid given the unprecedented event; robust regulatory regime, strong power infrastructure, flexible generating capacity and detailed planning meant the event passed off with flying colours providing a number of lessons for the future shape of the power grid.

Electricity Grid Balancing – A Tug of War

For people not from the power sector, a good analogy of how the power grid operates is with the sport of tug of war.

In the sport, the force on rope is applied by a pull from the opposing ends. As long as the pull is equal from both the ends, the rope is in equilibrium not moving beyond the tolerance zone marked by central lines.

If suddenly a few members from one side stop exerting any pull or new members start exerting extra pull, there is disruption in balance with one side being overwhelmed and the whole set up collapsing.

Similarly, in a large integrated power grid, a state of equilibrium normally exists between the power generators and consumers.

Electricity cannot be stored. It is transported from the generator to the consumer via transmission and distribution wires on a real time basis. This transmission happens at a pre-determined electrical frequency. All generation, transmission, distribution and consumption equipment are rated to operate at this pre-determined frequency.

Like the tolerance zone marked by central lines in the sport of tug of war, Power System Operation Corporation Limited (POSCO), the national grid operator, endeavours to ensure that the power grid frequency remains within the 49.7-50.2 Hz band with a target to keep it operating around 50 Hz.

Also, the Indian grid code mandates all participants of the power grid make all possible efforts to operate within 49.9 to 50.05 Hz. Overall 75 per cent to 80 per cent of the times the power grid operates within this band. Technically, tolerance of the power grid is higher than the above mentioned frequency range.

When either the demand or supply goes out of sync; electrical frequency becomes unstable. This results in the power grid operating beyond the pre-determined levels leading to grid failure and blackouts.

Manoeuvres to stabilise the power grid by starting new power stations and/or implementing demand side management with new load profile is technically complex and time consuming.

The infamous 2012 power blackout impacting more than 700 million people in North, East and North Eastern India was essentially a result of surge in demand resulting in very low frequency and grid collapsing.

Evolution Of India Power Grid

The Indian power grid has significantly evolved and modernised in the last few years. It has augmented its ability to respond to sudden supply-demand mismatch.

Earlier, the national power grid was functioning as five separate regional power grids. It was plagued with frequency indiscipline due to inadequate regulations and weak enforcement of the same.

Since 2014, with the southern grid integrating with the rest of the national grid, India operates as ‘one nation, one grid’ with one frequency mode. This allows for better balancing of both supply and demand.

Additionally, inter regional power transmission capacity has risen to almost 78 GW. This allows for large quantum of electricity movement between regions to balance the shortfall in supply from one region to another.

The erstwhile uninterrupted interchange mechanism for load balancing has been substituted with a more effective deviation settlement mechanism (DSM) for better discipline of scheduling and forecasting.

Since 2017, POSCO operates as a separate company managing the national load dispatch centre (NLDC) and five regional load dispatch centres (RLDCs) ensuring integrated and reliable operation.

Power Sector At A Glance Leading Up To ‘The 9 Minutes Lights Off’ Event

As of 31.3.2020, all India generation capacity is 370 GW. Before the lockdown due to the pandemic, typically about 160 GW of peak demand and about 3,600 BUs of energy demand was met during the day. This fell by about 25 per cent to about 120 GW of peak demand and about 2,200 BUs of energy demand.