The threat of climatic factors triggering the collapse of power grids remains real, show the 21 cases of fog-induced outages in north India over a span of three nights. This is despite the fact that the risk of a grid failure due to over-drawal by power distribution companies (discoms) has receded after the blackout in July last year, which left more than half of the country without electricity for several hours.
Tripping of power transmission lines happens when heavy fog mixes with unburnt carbon and other pollutants in the air and settles on the conventional porcelain disc insulators along the lines, shorting the conducting path and triggering a flashover.
According to experts, if the tripped lines were not repaired during the night itself, there was a risk that mounting load during morning would have put additional load on the remaining lines, which could have snapped under pressure, replaying the massive 12-hour-long blackout that happened eleven years ago in January 2002 in the northern region due to the failure of a sub-station in UP.
The central electricity regulatory commission (CERC), Power Grid and system operator Posoco are mandated to manage grid stability.
Last year's blackout was triggered by grid collapse due to excessive drawing of electricity by northern states such as Uttar Pradesh and Haryana. The norther grid collapsed first, triggering the failure of the eastern and north-eastern grids. With three of the five electricity grids down, more than 600 million of the country's population had to live without electricity for several hours on July 31. In comparison, the black-out a day before, on July 30, was limited to the norther region only.
After narrowing the grid frequency band in May, the CERC is expected to come out with new regulations soon to further tighten grid discipline. Specifically, the regulator plans to narrow the existing frequency band of 49.7-50.2 Hz to 49.9-50.1 Hz while increasing penal UI charges from Rs 9 a unit to more than Rs 11 a unit. When grid frequency is close to the lower or the upper band, overdrawl of electricity by power distribution companies could attract the maximum UI rate of payment. “We have completed the consultation process on the new grid frequency band and the final order may be issued soon,” a senior CERC official told FE.
The last revision of a grid frequency band was undertaken by the CERC following the grid collapse of July 2012.
In the inquiry ordered by the Union power ministry to find out the causes of the grid failure, UP emerged as the biggest culprit. Faced with a power shortage of 1,500-2,000 mw and without cash to buy electricity from the open market, UP was heavily overdrawing from the grid to mitigate its shortages.
However, now the UP discom has become cash-rich after casting its short-term loans recently with lenders, and it can buy power from the market rather than relying on the UI route to overcome its power shortfall. Haryana, which was also found overdrawing power from the grid on July 30-31, has now surplus power supply because of brisk capacity additions.
Following the recommendations of the inquiry committee, the regional and state load despatch centres are implementing projects, including islanding to restrict and localise the impact of tripping of power lines and avoid grid failure. Further, states have also been asked to improve their power purchase planning so that they do not have to rely too much on the UI mechanism to meet their power shortfall.
But apart from unscrupulous power overdrawl by discoms, climatic factors like fog can also trigger power supply disruptions. “Tripping of power transmission lines happens because of fog. However, our preparations to avoid such accidents have become better,” a senior Power Grid official said. Former power secretary RV Shahi said, “Though accidents can never be ruled out, both Power Grid and system operator Posoco are cautious enough to avoid a repeat of incidents like last year's grid collapse.”