Intermountain Power Project

The Intermountain HVDC transmission system operated by the Los Angeles Department of Water and Power (LADWP) brings power from a coal-fired station in Utah to the Los Angeles area. LADWP is the largest municipal utility in the U.S., serving over 4 million residents.

Original rated power was 1,600 MW at ±500 kV DC. The link was upgraded to 1,920 MW and then was recently upgraded again to 2,400 MW. Each pole has a 1,200 MW continuous and 1,600 MW short term overload capacity, to minimize impact on the power system in the event of a pole outage.

The receiving station in Adelanto is located in a seismically active area, so suspended thyristor valves are used to achieve maximum security. Hitachi Energy’s redundant converter control system was developed to meet stringent reliability requirements, and has since become Hitachi Energy’s standard for HVDC in every project.

Hitachi Energy had complete turnkey responsibility for the converter stations, which were commissioned in April 1986.

In 2011, Hitachi Energy made an additional upgrade, which included delivery of the MACH control system, additional AC filters and cooling system in order to reach a transmission capacity of 2,400 MW, to help LADWP expand input of renewable generation.

The upgrade demonstrates how an existing HVDC link designed mainly for bulk power transfer can be successfully converted to handle large amounts of volatile renewable wind power generation. It also shows how to utilize all inherent overload capability in such systems in order to increase the rating of a 25 year old HVDC link by 25 percent.

The control and valve cooling upgrade was done one pole at a time in just a few weeks, with minimal loss of transfer capability.