On Tuesday, India was hit with its second large blackout in two days. When the northern grid went dark Monday at around 2:30 am local time, more than 300 million people were left without electricity for several hours. The Power Systems Operation Corp. reported that New Delhi was completely restored by 1:00 pm, as well as 70 percent of the rest of the region. But the problems weren't over.
"The northern grid has failed again," Arvinder Singh Bakshi, the chairman of the Central Electricity Authority, told Reuters this afternoon. Today's outage affected nearly 600 million people, according to estimates.
India's power system is composed of five regional grids. In 2007, all but one of the regional grids were synchronized so that power-rich regions could transfer power to areas that needed it. Yesterday, the eastern and northeastern grids provided power to restore the northern grid, but today, they also collapsed. Both New Delhi and Kolkata, in the eastern region, were left without power.
According to a senior electricity official, who was not willing to be identified because he was not authorized to speak publicly, "Apparently, North was drawing 1300 MW from West and 0 MW from East when West-North connectivity failed, putting the entire load on East-North connectors. That also collapsed and North was plunged into darkness. Apparently deficit in Northern Region was 21 to 26 percent. With start-up power from West and East, North was limping back to normalcy and now that has gone again. A high level enquiry committee has been set up and no one is prepared to say anything."
A peculiarity of the Monday failure is that the first outage happened in the middle of the night—not when most people would expect the grid to be at peak load. "Common sense says at 2:30 AM, the power drawn should not be so high," says Sivaji Chakravorti, an electrical engineering professor at Jadavpur University in Kolkata. But energy policies in India have created a different type of demand, he explains. During the day, industrial customers can only draw a limited amount of power. But after 10pm, the restriction is withdrawn, and they're allowed to draw as much as they want. "At midnight, when the demand should have been lower, it is higher," says Chakravorti.
While the exact cause of the collapse will emerge in the next few weeks, it's clear that these outages were due to the basic mismatch of supply and demand. Large power outages can happen anywhere, of course, but India is unique in its dependence on seasonal rainfall.
This year's monsoon season, especially in Northern India, hasn't provided the water that the region's farmers need for their crops. Less rain means that farmers need to pump more water from deep boreholes, using highly subsidized electricity. Haroon Yusuf, Delhi's Power Minister was quick to blame neighboring agricultural states for drawing more power than they were allotted.
Grid regulators were certainly aware that the overdraw was a problem. According to Zee News,
in May this year, the Central Electricity Regulatory Authority (CERC) had issued notices to the state load dispatch centres (SLDCs) of Uttar Pradesh, Rajasthan, Punjab and Haryana asking them to halt overdrawing power from the Northern Grid.
While the CERC had asked these SLDCs to be prepared to buy additional power to meet the anticipated demand during summer/monsoon, the states failed to take notice and did not maintain the grid discipline.
Even more recently, in a 26 July hearing, CERC brought up the issue again. For the week of 10 July, the state of Uttar Pradesh overdrew an average of 26 gigawatt hours per day, according to CERC documents. After yesterday's blackout, the Central Electricity Authority has projected a peak power deficit of 8 to 12 percent.
Less monsoon rain also causes water levels to drop and hydropower production to slow. The northern grid is particularly reliant on hydropower, which accounts for 28 percent of the region's installed capacity [PDF]. Nationally, hydropower accounts for less than 20 percent.
So where can India get the power it needs to keep up with ever increasing demand? One potential solution is from hydropower plants that aren't monsoon dependent. Yesterday, much of the power that brought New Delhi back online (albeit temporarily), came all the way from dams in Bhutan. Over the last few years, India has provided funding to build several large hydroelectric plants and transmission lines in Bhutan, such as the 1 gigawatt Tala project. The government of India has promised to purchase at least 10 gigawatts of power from Bhutan by 2020.
There are also plans in the works to link the Indian grid to other regional neighbors like Sri Lanka and Bangladesh. The events of the past two days may give such projects even more political momentum.
Additional reporting by Saswato R. Das
See IEEE Spectrum's 2010 special report on the critical links between water and energy.