The northern grid had a close call on Wednesday night,with 18 transmission lines outages on account of transient faults caused under dense fog conditions. Fast restoration of the lines and simultaneous load reduction by the system operator prevented a cascade tripping that could have potentially caused a flashover and endangered the grid.
Officials said that the tripping was largely attributed to the lack of early winter rain this year. A combination of dirty insulators,atmospheric dust and carbon,along with the dense winter fog,forced multiple tripping of lines that could have caused blackouts or brownouts in large parts of the grid.
This phenomenon,which was earlier largely confined to the areas in the vicinity of Delhi as a result of the atmospheric pollution around the capital,has now spread to the northern hinterland,especially the Uttar Pradesh,Punjab and Haryana belt. This has largely been on account of excessive crop burning in Punjab and Uttar Pradesh,resulting in carbon in the air adding to the vehicular and industrial pollution. Under dense foggy atmospheric conditions,break down strength of the surface of the porcelain insulator reduces due to deposit of pollutant over it,triggering an outage.
The most recent incident experienced on this account was on January 2,2010,resulting into partial blackout in the northern regional grid affecting Punjab,Haryana,J&K and Himachal Pradesh. This was triggered by tripping of multiple lines due to transient faults caused under dense fog conditions in the affected areas.
Similar incidents of multiple lines tripping resulting in partial blackout in a major sections of the northern region earlier too on March 7 and 9,2008,January 27,2007,February 16,2006,December 23,2002,and January 2,2001.
In a bid to mitigate the impact of fog on the safety of the electricity grid,the grid managers have started monitoring of the weather parameters and have installed temperature and humidity transducers at key substations in the northern region. Such monitoring was found to be very useful in handling contingencies arising due to fog related trippings in real time.
Early winter rains have been extremely helpful in washing away some of the pollutants from the insulators and lines before the onset of fog.
In addition to monitoring weather conditions during winter nights,preventive actions such as replacement of porcelain insulators by anti-fog or polymer insulators having better breakdown strength under such conditions are being taken,officials said.