Sample Blackout at National Level (Case Studies)
- Our country’s grid is divided into five electrical regions-Northern, Eastern, Western, North Eastern and Southern. The grid frequency is to be maintained within specified limit (49.7 Hz to 50.05 Hz) by each regional load despatch centre.
- In 2012, the four grids were synchronized and were collectively called NEW Grid The Southern Grid was isolated l.e. It was not the part of the four grids. The southern grid had its own network functioning independently.
- When demand is more than the generation of supply, the frequency drops down, causing stress on the grid. Beyond a certain limit it leads to interconnections collapsing (cascade tripping) and the generating stations shutting off automatically as a result. The relays and circuit breakers have to perform this task of cutting off demand when the grid is overloaded. From reference material available on 30 July 2012 it is noted that there was heavy over drawing of power from the transmission line between the western and northern regions. Due to bad weather conditions, a lot of transmission lines and sub-stations, some generating stations were under outage on that day. The western region was having less load, hence most states in western region were under-drawing, whereas in northern region, a high demand was created, and states in northern regions started overdrawing. Net Import to northern region was 6000 MW, and net import from western region was also around 6000 MW. This created entire western and northern regions link overburdened. Therefore the frequency dropped down and the generating stations in this region were disconnected. This caused increased load on the other generating stations and these were overloaded which then began to break down one after the other. This is cascade tripping.
- This resulted into blackout in nearly the entire northern region covering all the 8 States Le, the States of Delhi, Uttar Pradesh, Uttarakhand, Rajasthan, Punjab, Haryana, Himachal Pradesh and Jammu and Kashmir as well as the Union Territory of Chandigarh.
- The All India Demand Met prior to the incident was about 99700 MW and the demand being met in the northern region was about 38000 MW.
Restoration Work :
- The blackout is very serious issue for any country, hence Immediate restoration of supply is done at warfoting level. Hydro Plants require very less time to restart, hence these were started. Some start up supply was extended to WR and SR, by 0800 hours all essential services like, Metro, Railways, Airports etc. were restored, and by 1000 hours around 40% supply was restored. However another blackout happened at around 1230 on 30 July 2012. Again similar steps were taken and by 1530 hours essential services were restored and by 1830 entire system was successfully restored.
Sample blackout at International level (Case study of National Grid Failure in 2012)
- Northeast United States and Northern Canada// November 9, 1965 : A faulty relay at Sir Adam Beck Station caused the biggest power failure in U.S. history At 5.16 p.m., the tripping of a 230 kV transmission line. This caused blackout in New York City Power was restored for most people within 13 hours.
- Thailand Nationwide Blackout// March 18, 1978 : The generators in the South Pranakhorn Powerplant in Samut Prakan failed, a nationwide blackout spread throughout Thailand. It took 09 hours to restore the system.
- Southern Brazil// March 11, 1999 : In 1999, approximately 97 million of the 160 million people living in Brazil lost power in what was the biggest blackout ever at the time. A lightning struck an electricity substation, which in turn shut down Itaipu, which was the largest power plant in the world.