Underexcited Operation of Large Turbine Generators on Pacific Gas and Electric Company´s System [includes discussion]

The power factor on the Pacific Gas and Electric Company´s transmission system has increased gradually in certain areas. This has been due largely to the growth of the high-voltage transmission line capacity and the increased use of unswitched capacitors which tend to bring about a high-voltage condition, particularly during light load periods. The ability to regulate system voltage by supplying underexcited kilovars from turbine generators has therefore become important. During May 1951 extensive tests were conducted at the Moss Landing Steam Plant of the Pacific Gas and Electric Company on two hydrogen-cooled 3,600-rpm units, one of which is rated 115,000 kva and the other 129,375 kva at 15- pound-per-square-inch-gauge hydrogen pressure. These tests were conducted as a joint venture with the General Electric Company and the objective was to determine limits of operation in the leading power factor range and thereby establish the basis for safe operating procedures under these conditions.