Dense fog over northern India led to total blackout in many parts of Punjab, Haryana and Jammu and Kashmir this morning due to disruption in transmission lines. The CMD of Power Grid, S K Chaturvedi said, the northern grid tripped at around 3.02 am following a technical snag in transmission lines that reduced power to zero at many sub stations. He said, NCR lines were saved because of certain precautionary steps like<br/>cleaning of transmission lines in advance. Power supply was disrupted in Ropar, Bhatinda, Yamuna Nagar and Panipat power stations, which are connected to the northern grid. However, by 7:30 am electricity was partially restored in some parts of Punjab and Srinagar after supply from Jalandhar, Nathpa and Uri sub stations were diverted to these states.<br/>Power is yet to be restored in smaller towns like Moga. Mr Chaturvedi said, the Delhi-NCR line is totally safe and work is going on to restore supply in the rest of the region.