The 1660 MW HVDC transmission system of the Intermountain Power Project (IPP) is designed to deliver energy from a coal-fired, two-unit generating plant in Delta, Utah, to load centers in southern California, USA. To minimize disturbance to the adjacent AC network and the relatively isolated generating plant, several special control features as well as high short-time and steady-state overload capability are required in the design of the IPP HVDC converter stations. The power system reliability requirements of the Western Systems Coordinating Council (WSCC) on the DC transmission system resulted in the specification of guaranteed reliability and availability requirements. The main features in the design of the main circuit equipment, HVDC controls, and the reliability and availability consideration of the IPP transmission system are presented. >