The Columbia Gorge Discovery Center’s new exhibit highlights the HVDC Test Center that Bonneville Power Administration operated for over 50 years near the Big Eddy substation.  The Discovery Center’s Eloise Russell says the test center was the first of its kind in the United States, established to use emerging industry knowledge of conversion between alternating current and direct current in designing a system to transmit power from the Celilo Converter Station 846 miles to the Sylmar Converter Station in Los Angeles.  The test center was demolished two years ago, and over 30 boxes of archives was salvaged to create segments of the exhibit.  The exhibit opens Saturday and will be on display until the end of May.