Power Grid Corporation of India (Powergrid) on Monday said its board has approved a proposal to raise up to Rs 1,200 crore by issuing bonds.'The Committee of Directors for Bonds approved the raising of bonds as unsecured, non-convertible, non-cumulative, redeemable, taxable Powergrid bonds - LXXVI (76th) issue up to Rs 1,200 crore,' the company said in an exchange filing.On the size of the issue, the company said the base size is Rs 400 crore, along with the green shoe option of Rs 800 crore.The bonds are redeemable at par at the end of the 10th year, and interest payment on a yearly basis, the company said.Powergrid, under the Ministry of Power, is India's largest electric power transmission utility with 1,76,762 ckm of transmission lines.