The second 1,000 MW nuclear power unit at Kudankulam is expected to restart power generation on October 7, the Power System Operation Corporation Ltd (Posoco) saod.
The mega nuclear power plant was shut down on August 4, due to hydrogen concentration in the stator.
The unit was earlier expected to restart generation on September 4.
India's atomic power plant operator Nuclear Power Corporation of India Ltd (NPCIL) has two 1,000 MW nuclear power plants at KNPP built with Russian equipment.
Kudankulam is in Tirunelveli district around 650 km from here.
However, officials of NPCIL at Kudankulam were not available for comment as to the reason for the delay in the plant's restart.