The India grid was tested as no grid in the world has ever been by Prime Minister Narendra Modi’s irresponsible 9 minutes-at-9-PM lights-off call. An unprecedented load reduction to the tune of 27%—or 32 Giga Watts (GWs)— took place and came back again, all within a span of 10-12 minutes.
No grid anywhere has ever seen a plunge and surge of load of this magnitude. It was indeed a trial by fire for Indian authorities who man the state, regional and national grids. It is the combined effort of grid authorities, power engineers and electricity workers that helped us overcome what could easily have turned into a disaster. If the Indian grid had failed—and it had a few anxious moments—it would have been a disaster for the country and its hospitals under the current lockdown due to the Covid-19 epidemic.
Why did Modi give a call which endangered the electricity grid? Was it only to make the people feel good about themselves, and that they were ‘doing something’, even if it is merely symbolic? Or was it some strange numerology or astrology mumbo jumbo, from which this “power of nine” was sought to harnessed against the virus? Modi bhakts flooded the social media with bizarre arguments of how the coronavirus would flee after being blinded and then suddenly lit up under Modi’s 9*9 call!
Whatever the reason for Modi’s call—some magical mumbo jumbo or merely optics—the danger to the grid was very real. Suddenly, in a matter of minutes, we lost 32 GWs or 27% of load on the system. Before we could even stabilise the grid from this blow, the load again came back within 10 minutes, delivering a second punch to the grid. The grid authorities had to then fight this new instability in the system as well.
From the preliminary report of Power System Operation Corporation (POSOCO), it can be see that the frequency change during the event was as much as 0.56% or almost 4 times the normal of 0.15% frequency change permitted in the grid. The magnitude on the grid of this Modi-created event can be seen from the frequency chart in the POSOCO report. This gives a lie to the Ministry of Power’s contention that the switching off and on of lights at this magnitude is well within the normal operations of the grid.
Why did the frequency change so significantly in the grid, rising to almost 4 times from its normal operating range? Frequency change indicates the lack of balance between supply and demand. When supply is more than demand, the frequency rises; if demand is more than supply, then the frequency falls. If the grid had been kept operational before the 9 PM event, then the rise of 0.56 of frequency that we witnessed after lights were switched off could have taken the grid frequency to 50.56, or past the 50.5 upper limit. This would have led to various protections—essentially to protect equipment from high frequency—coming into operation and lead to tripping of some of the generators. Under such conditions, it would have been much more difficult to save the grid when the lighting load came back into the system again.
This was the reason why the grid authorities changed the operating frequency band and kept the frequency of the grid at 49.7 before the event. From the chart, we can see that the frequency was lowered to 49.7, or 0.2 points below 49.9, the normal lower operating range of the grid, at 8.45 PM. This allowed the extra margin that helped save the grid. For an imbalance of 1,200-1,500 MW, there would be a 0.1% change in frequency. The frequency curve during the entire lights-off period showed that the grid frequency was rising continuously as the loads being shed were not enough to balance the grid—and therefore, the continuous rise of frequency.
Such a frequency rise also means that every equipment connected to the grid, including the motors in our homes—fans, compressors in refrigerators, air conditioners—ran a little faster to absorb the surplus energy of the grid. The system and all grid connected equipment were stressed, but the grid survived, though not without cost.
Let us look at how the grid managed the sudden decrease and increase of load in the grid. From the chart that POSOCO has given in its preliminary report, we can see the steep fall in demand and its coming back after a few minutes.
How did the grid withstand this huge plunge and surge in load, all within a few minutes? POSOCO had prepared a comprehensive 26-point plan in consultation with regional and state load despatch centres on how to handle this emergency. Broadly, they had decided that they would bring down the load of thermal power stations, which respond slowly, and increase hydro- and gas-based generation, which respond much faster to a demand change.
Our chart below, constructed from POSOCO data, shows how the hydro and the gas based stations took about 20 GW of the 32 GW load drop, the rest by thermal. The grid also tripped about 2 GW of wind turbine supply in order to manage the surplus power with all the lighting load being shed at 9 PM. There is a cost to all of this massive jugglery that the grid had to perform to save it from tripping, both when the lights went out and came back. The generators, particularly the hydro- and gas-based stations absorbed the major part of this cost, and the stresses on their equipment.
Why did POSOCO, as well as we, underestimate the load that would go off the grid at 9 PM? POSOCO had anticipated about 12-14 GW of load would reduce at 9 PM and come back. One reason is a number of feeders in colonies and housing societies being switched off by the Modi bhakts to enforce the 9 minute blackout call. Also, fears among a section of the people of damage to equipment during a grid instability saw loads go off the system even before the 9 PM schedule. This led to a much larger shedding of load than any of us anticipated.
The Ministry of Power had issued a statement on 4 April, saying that the 5 April call by the PM was well within normal limits and would be handled by standard operating protocols of the grid. This was a complete lie. In its 26-point advisory, issued to all power operators, POSOCO calls this event “unprecedented” and laid down extraordinary measures to be taken specifically to handle this Modi event. And just for the record, the last point in POSOCO’s 26-point list of actions to be taken, was “preparations for a black start” for “restoration of services”. Black start is required when a power station has to start without grid power being available, as happens after a grid collapse needing restoration of grid services. Clearly, POSOCO was well aware of the risk to the grid under the Modi-initiated “unprecedented” event of 5 April.
The grid was not knocked out as POSOCO, the national, regional, and state load despatch centres, the generating stations and all the electricity staff made extensive preparations. The question remains, should the PM have created this emergency for the grid when we are already facing an epidemic and a national lockdown?