How Indian power engineers sailed the electric grid through the Sunday 9 pm 9 minutes event

National power demand on Sunday, 5th April, 2020, between 8:30 PM - 10:00 PM as compared to previous day demand during the same time. Image Source: Report published by POSOCO

In the global crisis of the COVID-19 pandemic, the 'normal life' as such has come to a standstill. Amid the 21 days nationwide lockdown, the Indian Prime Minister urged the nation to express solidarity for India's collective stand against Corona pandemic #India Fights Corona. The task given to Indian citizens was simple: turn off all lights in the house and instead light lamps, candles, or torchlight for 9 minutes at 9 PM on Sunday, 5th April. 

 Soon, several social media platforms and news feeds were filled with mixed reactions to the appeal, mainly correlating simultaneous switching-off of lights with failure of the electric grid. Voices from all spectrums of social life voiced their grave concerns for the Indian electric grid. Amid the hullabaloo, it became difficult for a voice of reason and domain knowledge to be audible. Now that all dust has settled down, this article details a factual analysis of the 9pm9minutes event acknowledging the Indian power engineers who pulled this unprecedented event successfully without interrupting Indian electric grid that serves more than 200 million customers.

How does the electric grid work?

The most critical task in the successful operation of an electric grid is matching up power generation with power consumption at all times. This task may seem challenging at first. It can be reasoned that switching on and off electric equipment at home multiple times a day, must make power consumption volatile. But the good news is that you and all your neighbors do not turn on or off your TV or lights at the same time. The grid caters to lakhs of such customers, and it is the aggregate behavior that matters. When we take the sum-total of power consumption by all the customers across a large region (typically a state or a metropolitan area), the aggregate power consumption turns out much smoother and predictable. Thus, it is easier than thought to match up power generation with power demand.

 An obvious question which arises is, what happens when the generation and demand do not match? The Indian power grid operates at a frequency of 50 Hz.  When power generation is more than the demand, frequency tends to increase and go beyond 50 Hz. Conversely, for total generation less than aggregate demand, the frequency drops below 50 Hz. Thus, frequency monitoring of the electric system helps grid operators to take remedial control of power generation accordingly. For a successful grid operation, frequency needs to be maintained between a tight bound of 49.95 Hz - 50.05 Hz as dictated by the Indian Electricity Grid Code. If this deviation of frequency is not controlled, it can lead to collapse or what we call a blackout.

 In this regard, it is vital to understand a property of electric energy generation known as "ramp rate". Typically, electrical energy is generated at large hydroelectric power plants, coal, petroleum or nuclear-based thermal power plants with the recent addition of wind turbines and solar energy. In these massive plants, it is often challenging to alter power generation instantaneously. The measure of their ability to change power generation with respect to time is defined as the ramp rate of the generators. For example, typically, hydroelectric power plants have a high ramping rate and can reach full capacity from a cold start within a few minutes.

 What was so peculiar about the ‘9 PM 9 minutes’ event for the electric grid?

The Indian prime minister's call to turn off electric lights in the households had a unique implication for the electric grid. As the whole country was going to turn off their lights precisely at 9 PM, and then turn them back on again after 9 minutes, this should have led to a very sharp decrease in energy demand followed by a sharp increase. Besides, amid the ongoing lockdown, most industries and businesses have already turned down their power consumption. This has increased the total share of household lighting load in aggregate power demand.

 The government agency- Power System Operation Corporation (POSOCO), which is responsible for ensuring reliable operation of the Indian grid, had predicted a net change in demand close to 12-14 GW during this event. The task for the grid operators was to decrease generation by a considerable amount sharply at 9 PM and then go back to the original level in minimum time. Otherwise, the system frequency could have gone beyond the stable operation of the grid and may have led to grid failure or blackouts. It is worthwhile to note that this is not the first of its kind event. USA President Herbert Hoover asked citizens to switch off the lights on Oct 21st, 1931 to show national mourning on the death of Thomas Edison who invented the light bulb. There was another planned event to turn on the lights of Perth, Australia on February 20th, 1962 to mark Astronaut John Glenn’s orbital passage over the city. 

How did Indian power grid engineers navigate through this smoothly?

Given that the nature and magnitude of the 9pm9minutes event were unusual for the electric grid, still, proper planning and timely intimation, gave POSOCO and other concerned organizations time and resources to plan for preemptive actions. They were prepared to mitigate all probable scenarios that could have jeopardized electric grid operation.

  • Sunday, 8:49 PM: Frequency was kept very low at 49.7 Hz to provide room for frequency shoot up in the following few minutes as people started switching off the lights. All hydroelectric plants were running to support the grid owing to their flexible operation capabilities at high ramp rates.
  • Sunday 8:50- 9:10 PM: The total demand went down by 31 GW, much higher than the predicted 12-14 GW. However, the operational hydropower plants were prepared to handle such worst-case uncertainties. Thus the system continued smoothly.
  • Sunday, 9:10 PM: Frequency was kept at the higher end for the next few minutes. This enhanced the grid's ability to accommodate a sharp load increase, eventually leading the system into normal operation.

 Beyond the aforementioned, various coordinated technical actions were taken to ensure smooth operation at the level of individual customers. While this event has garnered national attention in media platforms, for power engineers, it was business as usual, to keep the grid operational without interrupting the power supply to millions of customers.

Impact of mainstream and social media

POSOCO estimated a reduction of around 12-14 GW for this event based on the detailed information available from consumer data, load composition, etc. However, in reality, it turned out to be 31 GW, more than double the prediction. The most well-understood hypothesis to explain this massive gap is that speculation of possible damage to electric equipment in social media created public fear. This was further fueled by widespread coverage by mainstream media, without reaching out to domain experts. As a result, people may have disconnected the power supply of their entire households, thereby taking out various other loads such as refrigerators, fans and air conditioners. This action by a large segment of the population may have led to the enormous gap between expected and actual load change.

 In general, the role of media should be a subject of scrutiny in all science and engineering related matters. We believe that an unnecessary hype and out of proportion attention is likely to put an extra pressure on the shoulders of scientists and engineers that may detract them.

Conclusion

Analyzing the timing and utility of the Indian prime minister's '9 PM 9 minutes' initiative is not in the purview of this article. However, the successful and smooth execution of this event reflects the robustness of the Indian electric grid. Successfully managing a ramp-up and down of 31 GW demand is no less than an achievement. This highlights the competence and preparedness of Indianpower engineers to deal with extreme scenarios.

Reference: POSOCO Report on 9 PM 9-minute event:  https://posoco.in/download/preliminary-report-on-pan-india-light-switch-off-event-on-5th-april-2020/?wpdmdl=28177

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