Those long 9 minutes--when India’s power grid operators held their breath

To compound matters, the estimated electricity load reduction went off the charts and was at 32 giga watts (GW)—enough to meet the entire power demand of Pakistan. It was earlier projected to be around 13 GW.

According to a preliminary report by the government late Sunday night reviewed by Mint, “The anticipated reduction in all India demand during this period of 9 minutes was around 12000–14000 MW considering that only lights would be switched off."

The directive was clear, with no margin for error. The unprecedented ramp down and build up of electricity load had to be done successfully, within a small window of nine minutes—-something that hasn’t been tried anywhere in the world on such a scale.

At 9 pm, heeding Prime Minister Narendra Modi’s call, India switched off lights for 9 minutes. The load sharply dropped and kept on falling as people switched off more than their lights.

“The demand went down from 117300 Megawatts at 2049 hrs to 85300 Megawatts till 2109 hrs; that is a reduction of 32000 megawatts. Then it started increasing. Frequency was maintained within a band of 49.7 to 50. 26 Hz, which means the voltage was kept stable," said power minister Raj Kumar Singh.

“Grid Frequency during the event remained in the range of 50.26 Hz to 49.70 Hz with maximum and minimum frequency of 50.259 Hz and 49.707 Hz recorded at 20:49 Hrs and 21:08 Hrs respectively," the government report added.

Grid frequency is a critical aspect of power system operations, with global standards requiring that grid frequency be kept close to 50 hertz (Hz). India’s grid code calls for grid frequency to be in the range of 49.5- 50.2 Hz. Any sudden change in demand pattern impacts the grid frequency. The engineers were particularly worried given India’ massive power transmission failures in July 2012, which left around 700 million people without electricity.

“The total reduction in all India demand recorded during the event was 31,089 MW. All India demand started reducing from 20:45 Hrs and minimum demand of 85,799 MW was recorded at 21:10 Hrs. Subsequently, from 21:10 Hrs, the demand started picking up and settled around 114,400 MW at 22:10 Hrs," the report added.

Given the enormity of the event, power minister Singh along with power secretary Sanjiv Nandan Sahai and his team was keeping a close eye on grid operations from National Power Monitoring Centre housed in Shram Shakti Bhawan, a Soviet era styled government building located on Rafi Marg.

The task to manage such a complex grid wasn’t easy as it involved a synchronous dance across the Indian power sector, with India’s grid code calls for grid frequency to be in the range of 49.5- 50.2 Hz. It required close coordination between the grid operators and power project generators across coal, gas, hydro, nuclear and green energy sources run by the Centre, states and the private sector.

Power sector experts were effusive in their praises.

“It is indeed a superbly executed engineering feat that we pulled off a 32 GW fall in demand even though the preparedness was for 12–14 GW. Demonstrated the synchronised actions, resilience of grid and capabilities of our LDCs," said Sambitosh Mohapatra, partner, power and utilities at PwC India.

“Withstanding the wild fluctuation in system demand yesterday in a short time proved that India’s electricity grid has come a long way since the Grid collapse of July 2012, where one third of the country plunged into darkness," added Debasish Mishra, partner at Deloitte India.

India’s hydropower stations played a key role as it provided the flexibility of a quick generation ramp up and down as they take the least time to switch on or off.

“Hydro generation across the country was maximized by 20:45 Hrs and generation reduction of 17543 MW (from 25559 MW to 8016 MW) between 20:45 Hrs to 21:10 Hrs (matching with demand reduction of 31089 MW during the same period) was achieved with these resources. This hydro generation was again ramped up from 8016 MW to 19012 MW from 21:10 Hrs to 21:27 Hrs to meet the increase in demand after the event," the report said.

India has one of the largest interconnected power grid that is capable of transferring 99,000 mega watts (MW) of electricity from any corner of the country. It is also connected with Bangladesh, Nepal and Bhutan.

“Reduction of total 10950 MW generation was achieved through thermal (6992 MW), gas (1951 MW) and wind generation (2007 MW) during 20:45 Hrs to 21:10 Hrs," the report added.

The expertise of its grid engineers further bolsters India’s ambitious green energy plans with the country looking to add 175 gigawatts (GW) of renewable capacity from infirm sources such as wind and the Sun. Given the national’s grid interconnection with India’s neighbours, it also adds heft to the ambitious global electricity grid plan pitched by Prime Minister Narendra Modi that plans to leverage solar power generated in one geography to feed the electricity demands of other nations.

“In managing a staggering 31 GW ramp down on demand in matter of minutes, hydro resources helped the grid managers like a rock star. Kudos to Posoco and the LDCs for pulling off this spectacular event within the technical range of system frequency," Mishra added.

It is Posoco which manages these complex functions through the NLDC, RLDCs and SLDCs—-drawing comparisons with an air traffic controller. The country has 33 SLDCs, five RLDCs—for the five regional grids that form the national grid—and one NLDC.

“Our engineers managed it brilliantly. Full credit goes to our system operators—NLDC, RLDCs, SLDCs and generators," said Reji Kumar Pillai, president, India Smart Grid Forum and chairman, Global Smart Grid Federation who had correctly estimated that the projected load reduction of 12.87 GW was on the lower side.

The nationwide lockdown has resulted in peak electricity demand coming down, with commercial and industrial power demand taking a hit after many factories shut down. However, household consumption, which accounts for around a quarter of India’s power demand, has gone up.

“You can call it quite an experience," quipped a government official closely involved in the gargantuan exercise requesting anonymity.