Government of Andhra Pradesh enacted the AP Electricity REFORMS ACT in 1998.As a sequel the APSEB was unbundled into Andhra Pradesh Power Generation Corporation Limited (APGENCO) & Transmission Corporation of Andhra Pradesh Limited (APTRANSCO) on 01.02.99. APTRANSCO was further unbundled w.e.f. 01.04.2000 into "Transmission Corporation" and four "Distribution Companies" (DISCOMS).
From Feb 1999 to June 2005 APTransco remained as Single buyer in the state -purchasing power from various Generators and selling it to DISCOMs in accordance with the terms and conditions of the individual PPAs at Bulk Supply Tariff (BST) rates. Subsequently, in accordance with the Third Transfer Scheme notified by GoAP, APTransco has ceased to do power trading and has retained with powers of controlling system operations of Power Transmission