The modern power systems normally operate at heavily loaded condition and often faced with the steady increase in load demand. In spite of adoption of many precautionary measures, still all over the world, collapse of power systems or grid failure are common which incur huge losses of tariff as well as industrial production. Normally, these blackouts are avoided by severing a critically loaded line but it causes aftermath effects, like oscillations and instability problem leading to grid failure or blackout. Thus the ability to maintain voltage stability of stressed power systems has become a major concern for practical operation. The worst blackouts of the last 50 years 1.India - July 30-31, 2012 (700 million people affected)The worst blackout in recent history occurred in northern India on two consecutive days in July 2012. The first blackout occurred on 30 July in the Northern grid, affecting 300 million people in nine states including India's capital region New Delhi.A bigger blackout occurred the next day in the NEW grid which comprised the Northern, Western, Eastern and North-Eastern grids after the Northern grid was restored and synchronised with it. It affected a total of 700 million people across 20 Indian states.Overdrawing of electricity by certain states and weak inter-regional power transmission corridors were cited as the reasons behind the blackout.The incidents caused trains to fail and traffic lights to stop working, causing multiple traffic jams. Surgical operations were cancelled and construction and mining work was halted across the northern region of the country.2.India - January 2, 2001 (230 million people affected)India witnessed another blackout on 2 January 2001 due to the collapse of the Northern grid, which affected approximately 230 million northern Indians depending on the second biggest interconnected network in the country.The failure of a substation in the state of Uttar Pradesh triggered the collapse, while poor and inadequate transmission equipment were also blamed.More than 80 trains were stranded across the region and other businesses and services were also halted. The grid took 16 to 20 hours to be restored, causing an estimated loss of up to INR 5bn.3.Java and Bali, Indonesia - 18 August 2005 (120 million people affected)A power outage occurred across the Indonesian islands of Java and Bali in August 2005, affecting 120 million people or nearly half of the country's population. The capital city Jakarta and its neighboring province of Banten were completely blacked out, and parts of West Java, Central Java and East Java also suffered blackouts.The Java-Bali power grid, which had an installed capacity of 19,615MW, collapsed due to the failure in a 500kV transmission line between Cilegon and Saguling in West Java.Transport services were disrupted and a number of international and domestic flights were delayed or cancelled due to the outage. The grid system was, however, fully restored within 24 hours.4.Southern Brazil - 11 March 1999 (97 million people affected)Approximately 97 million people were left in the dark across south and south-eastern Brazil in March 1999 after a bolt of lightning struck an electricity substation in Sao Paulo. The incident caused a chain reaction that resulted in the shutting down of Itaipu, one of the world's biggest hydroelectric power plants.The blackout, which lasted for five hours, paralyzed Sao Paulo and Rio de Janeiro, two of Brazil's biggest cities.Approximately 60,000 people were stranded in Rio's underground subway. To prevent looting and assaults, 1,200 military police officers were deployed in Rio and the city tunnels in S�o Paulo were closed.5.Brazil and Paraguay - 10 November 2009 (67 million people affected)