An unprecedented day in Indian history has left a lot of questions in its lurch. Arguably the biggest ever power outage in Indian history has taken place today, and at its peak it had left more than half of India powerless. At a time, as many as 19 out of 26 states reported to be without power, but that situation improved quickly. Even then, it wasn’t quick enough to save face and the Indian government has a lot of political questions to answer. We attempt to answer the other question that the public are asking: Why this massive failure?
What happened in India: a summary
It is futile to simply hypothesize the root cause of the trip, but it is clear that over draw of power from the Northern Grid was responsible for the initial failure of the grid. In fact, the Northern Grid had already fallen once yesterday, but was shoddily restored.
Unfortunately, it was drawing too much power from the Eastern Grid while operating at less than full capacity and the Eastern Grid fell too. With two massive power grids out of commission, even large parts of the National Capital were left without electricity. The corridors of power fell dark and, pun intended, powerless!
The official reason for the outage isn’t known. The details might take months to unravel. The truth might be as tangled up as the wires that might have caused this disaster. Instead of foraging for the truth, let us take a look at a couple of other famous power outages, both in North America, and also take a look at what caused them.
Case Study 1: Quebec, 1989
In 1989, a huge solar storm hit North America and specifically knocked out Quebec’s power supply. With Hydro-Quebec out of operation, the load fell on James Bay. With five lines tripping one after the other on James Bay, the load on the station grew to 21,350 MW, way higher than what it could possibly handle. The station blew within seconds, putting a lot more load on whatever system was still feeding Quebec power.
Those systems tripped soon after. The whole James Bay area grid had fallen within a minute!
Info from: http://www.ips.gov.au/Educational/1/3/12
Why do grids trip in a cascading fashion?
And that is exactly the trend that large electricity grids follow! Electricity grids are important because electricity, once produced, cannot be stored. Electrical power is immediately consumed and it is critically essential that demand and supply are just equal. Now, consider a huge transmission network carrying power from one substation to a few nearby sub-substations for efficient distributions.
It is important that the sub-substations accept whatever power is being fed to them. Now, say that there is a surge in one of these sub-substation lines, due to either a solar storm or a short circuit. Now, this excess current flow will trip off necessary safety devices, called relays, which will immediately try to regulate the current in the line. That relay might trip if the current is too high and then the excess power being fed to the sub-substation will divert to other sub-substations. These lines will then overload, causing a similar effect of trip and transfer. In fact, the more the system trips, the more the transfer of power, which gives a nasty positive feedback. This runaway or a cascade process leads to the collapse of all connected substations, essentially blacking out a complete grid.
Lesson: In case of a power surge, the grid drops like a series of dominos.
Wait there is more!
Case study 2: Northeast America and Ontario, 2003
In August, 2003, large parts of the Northeastern and Midwestern parts of America and Ontario, Canada faced a large power shortage.
The reason was the failing of a generating plant in Eastlake, Ohio. As the plant went out of operation, the high electrical power demand immediately started sucking power out of the connected lines like leeches. This drainage of excess power caused the transmission lines to overheat (more the current flowing, the more is the heat produced). The overheating caused the wires to sag and it caught some really tall trees, which caused a short circuit. The excess power on this line again caused the familiar cascading failure and the whole grid went bust!
Power was restored to all parts within 20 hours. Most parts regained power within four!
Meanwhile back in India…
It is very safe to bet that something like this has happened in the Indian scenario. The northern states of Haryana, Punjab and Uttar Pradesh were supposedly drawing too much power – much more than what they were entitled to. The reason that this collapse didn’t take place for so long is that the lines could handle much more than what their ratings say. This time something tripped and a spark fell on the tinderbox.