THE Indian grid was tested as no grid in the world has ever been by PM’s 9-minute at 9 pm lights off call, on April 5. An unprecedented load reduction to the tune of 27 per cent or 32 Giga Watts took place and came back again, all within a span of 10-12 minutes. No grid in the world has ever seen a plunge and surge of load of this magnitude, so it was indeed a trial by fire for the Indian grid authorities, both state and national, and the generators. It is this combined effort of all the authorities, the power engineers and the electricity workers that he
lped 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 and the Covid-19 epidemic.
Why did Modi give such a call which endangered the electricity grid? Was it only to make the people feel good about themselves that they were doing something, even if it was merely symbolic? Or was it some strange numerology or astrology on which this “power of nine” was sought to be harnessed against the virus? Social media from Modi bhakts flooded with more and bizarre arguments of how the coronavirus would flee after being blinded and then suddenly lighted 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. We suddenly, in a matter of minutes, lost 32 GWs or 27 per cent of load on the system. Before we could even stabilise the grid from this blow, this 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 seen that the frequency change during the event was as much as 0.56 per cent or almost four times the normal of 0.15 per cent frequency change permitted in the grid. The magnitude of this Modi created event on the grid can be seen from the frequency chart in the POSOCO report. This gives lie to ministry of power’s contention that the switching off and on of light of this magnitude is well within the normal operations of the grid.
Why did the frequency change so significantly in the grid, rising to almost four 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 a rise of 0.56 of frequency that we witnessed after lights were switched off, would have taken the grid fre
quency to 50.26, or very close to the 50.5 upper limit. This would have led to various protections – essentially to protect equipment from high frequency – coming into operation leading to tripping of equipment. Under such conditions, it would have been much more difficult to save the grid when all the lighting load came back into the system.
This was the reason that 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. It also meant that every equipment connected to the grid, including the motors in our homes – fans, compressors in the 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.
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.
The ministry of power had issued a statement on April 4, saying that the April 5 call by prime minister 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 an “unprecedented” one and lays 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” and “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 and grid services have to be restored. Clearly, POSOCO was well aware of the risk to the grid under the Modi-initiated “unprecedented” event of April 5.
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 prime minister have created this emergency for the grid? When we are already facing an unprecedented epidemic and a national lockdown?
