Power grid FAQ

Published: Tuesday 31 July 2012

What's a power grid failure?

A power grid is an interconnected network of high-power transmission lines that transmit electricity from a power plant to houses. India has five regional grids: northern region (NR), eastern region(ER), western region (WR), southern region (SR) and north-east region (NER). The western, northern, north-eastern and eastern grid run in a synchronised fashion and are called the New Grid collectively. Technical problems, like fluctuation in frequency due to overdrawing of power by states, along the course of a grid network can cause the grid to trip or fail. On July 30, the northern grid failed, and subsequently on July 31 even the eastern and north-eastern grid failed.

How does a grid fail?

Electricity has to be transmitted at a certain frequency. Fluctuations in the frequency up to a certain range can be tackled by the grid, but beyond a certain point it can cause the grid to trip. Frequency required for proper transmission of electricity is around 50 Hz. One important reason for frequency fluctuation is over-drawing of power. Lack of rains can cause states to overdraw. Lowering of frequency can reduce the speed of the generators at power houses, leading to their inevitable shutdown. This can snowball into a chain event, subsequently shutting down several power stations one by one. This is how a grid fails.

What areas have been affected in the past two days?

According to the Power Grid Corporation of India (PGCI), the failure of the northern region grid on July 30 disrupted power supply to nine states in the region including Delhi. The grid disturbance occurred at about 2.35 am. On July 31, the northern, eastern and north eastern grids failed at about 1 pm, rendering about half of India’s population without electricity. Power supply to major networks like the railways and metro was also disrupted, leaving passengers stranded. Thirty million people rely on the northern railway division every day. According to the Indian Railways, 300 trains have been affected because of the power outage. On the other hand, most of the traffic lights in tier 1 as well as tier 2 cities stopped working, causing long traffic snarls. Shut down of metro rail service affected close to two million commuters. On the second day after the collapse of the three power grids, the authorities found that fault occured near Agra at a load dispatch centre. Both times, the fault had occured in the same tranmission lines near Agra. R N Nayak, chief of the Power Grid Corporation of India (PGCI), said in a press release that power would be restored by 7:30 pm in all the 19 states affected by power crisis. “At present, the northern grid is getting power from Gwalior and Agra sub stations as well as from three hydropower projects in Tehri and Vishnu Prayag in Uttarakhand and Nathpa Jhakri plant in Himachal Pradesh,” said Nayak.

Major grid collapses in the past

The 2001 grid collapse was India's biggest grid collapse. The tripping happened because of a fault in a substation in Uttar Pradesh. It took more than twelve hours to fix it. Winters of 2008 and 2010 also saw grid collapses as fog caused technical snag in the transmission lines.

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