Innovative high-voltage technology supports wind power transfer from remote Californian desert

2013-05-29 - ABB teamed up with San Diego Gas and Electric to develop a 500 kilovolt gas-insulated Station Service Voltage Transformer “TIP” for a switching substation in El Centro California, offering the ideal solution to supply small amounts of power directly from high-voltage lines in remote locations.

By ABB Communications

500 kilovolt (kV) switching substation at Ocotillo

Wind and solar farms have sprung up across the southwest deserts of California to help feed the energy starved population centers on the west coast of the United States. To facilitate transfer of this clean renewable energy, San Diego Gas and Electric (SDG&E) constructed a large 500 kilovolt (kV) switching substation at Ocotillo. Such high-voltage switching substations require relatively small amounts of low- and medium-voltage alternating current (AC) to run vital auxiliary and control applications. Usually the power supplied to auxiliary loads at substations is delivered by either a distribution line or the tertiary winding of the main power transformer, but at this remote site neither solution was available.

SDG&E engineers saw a standard single phase power transformer as the simplest solution to the problem, ABB engineers instead identified a more cost-effective way to tackle the problem. They suggested the gas-insulated SSVT “TIP.” The challenge was that ABB had a solution that was only rated up to 420 kV with outputs up to 600V, whereas the site application required a 525 kV product and a medium-voltage (7.2 kV) output at 333 kilovolt-amperes (kVA).

Modified gas-insulated Station Service Voltage Transformer “TIP” for 500kV.
The BIL of the existing ABB's TIP 420kV matched the transformer requirements for Ocotillo substation, but the unit required re-qualifying for 525kV by using bigger cores and tank, and designing the bushing for medium-voltage output to ensure efficient transfer of power from the SSVT to the distant control room. After discussions between ABB’s factory in Italy, where its gas-insulated SSVTs are developed, and SDG&E, the right-sized SSVT was identified and a modification proposed. The new optimized solution proved to be compact, cost effective and energy efficient.

After customer design reviews, two units were manufactured to meet the critical schedule set by SDG&E. The units successfully passed design and witness tests by SDG&E, together with the stringent seismic shock tests required for the region. In less than seven months ABB was able to design, manufacture, test and deliver an upgraded product on time. The units have been installed and successfully energized on site to the customer’s satisfaction.

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