hans.bjorklund@se.abb.com Upgrading the Intermountain HVDC Project to handle 480 MW additional Wind Power Mohammed J. Beshir Hans Bjorklund Los Angeles Department of Water and Power ABB USA Sweden SUMMARY The Intermountain Power Project, Southern Transmission System (IPP STS) was built in the early 80’s and commissioned in 1986 to bring power from a 1600 MW coal-fired generating plant in Utah to Southern California. The original project comprised of one bipole with 1600 MW ±500 kV continuous rating, meeting (N-1) reliability criteria. IPP STS had a very unique short-time overload rating allowing one pole to run at 2.3 p.u. current for few seconds before ramping down to operate continuously at 1.5 p.u. current (1200 MW power) should one pole trip [1]. To achieve this large overload on one pole all redundant cooling equipment for the transformers and the valves were used. The reactive consumption increased for the overloaded pole, but the full reactive power compensation for the bipole was available for that single pole. Some of this overload capability was used in 1989 when the bipole was up-rated to 1920 MW. To advance California’s environmental policies, in 2005 Los Angeles initiated an aggressive renewable resource development program to reach a 20% renewable portfolio standard (RPS) by 2010 (which was later supplemented with 35% RPS by 2020 and 30% CO2 reduction by 2030). One possible source for additional renewable resources was the wind power potential of southern Utah. To be able to bring such power into the Los Angeles area the IPP HVDC link provided a very interesting opportunity as well as a challenge. Since each pole of the IPP STS was rated 1200 MW, continuous operation, there was a potential to have a bipole rating of 2400 MW resulting in a 480 MW capacity upgrade. However, at 2400 MW rating, the (N-1) reliability criteria could not be met and still maintain the (N-1) redundancy criteria, as redundant A.C. filters and cooling for the valves and transformers were not available at this power level. At the same time the project had been running for over 20 years and a control system upgrade before 30 operational years had already been planned. These two needs were combined and LADWP issued a request for proposal for a power and control system upgrade to take place before the end of 2010. The contract to perform these upgrades was awarded in December 2008. The control concepts needed to integrate 480 MW of fluctuating wind power into an existing HVDC link and still maintain a large amount of bulk power transfer capability created many new challenges and special control features were developed to handle this efficiently. 21, rue d’Artois, F-75008 PARIS B4-108 CIGRE 2012 http : //www.cigre.org