PATNA, June 23 -- Power supply from the Gaurichak grid to the Mithapur grid was affected following a snag on Sunday evening, as many areas in central Patna went without electricity for around an hour, said officials. Power supply was disrupted to localities like Ramkrishna nagar, Bahadupur and areas catered to by the Mithapur I and II sub-stations, said officials. "We have been able to restore power supply to the 132 kV Mithapur grid through the Jakkanpur source. Our engineers are on the job and trying to locate the fault in the Gaurichak grid, which also supplies power to the Mithapur grid," said a senior officer who requested anonymity. The fault came barely a couple of days after power supply from the emergency restoration system (ERS), a temporary tower erected to provide power supply to the affected areas by bypassing the grid, was shifted to the normal supply chain on Friday evening. The snag in the grid caused a scare on Sunday, as it had taken the engineers almost nine days to fix the fault in the gas insulated station (GIS) of the Mithapur grid, reported at around 10.30pm on June 11. The fault plunged half of Patna into darkness for almost 17 hours, forcing the authorities to set up the ERS. A team from Crompton Greaves Ltd., the manufacturers of the GIS, was requisitioned to fix the fault, and the exercise was completed last Friday. The GIS at the grid that controls high voltage burst on June 11, leading to leakage of SF6 (sulfur hexafluoride) gas, which is primarily used in the electricity industry for insulation of the switchgear system. "We are not dismantling the ERS tower at this stage. The ERS will remain in place to attend to any exigency arising during the summer," said the officer....