On January 14–April 27, a 380 kV transformer failure in Bursa Natural Gas Fueled Combined Cycle PP in Turkey, was accused of voltage deviations in the interconnected power grid that resulted in a blackout. Another failure occurred in 154 kV Babaeski substation which caused a blackout in Thrace. 6 cities and more than 20 million people were affected by the Marmara blackout of 2012. The power was back in all cities in the evening. The blackout disrupted metro and tram operation in Istanbul. Also gas heating systems did not work during the blackout. The problem was resolved by getting electricity from Bulgaria to Thrace and feeding lines in İstanbul from Ambarlı Natural Gas PP in İstanbul, 104 days fully restored.