Alternator characteristics under conditions approaching instability

In this paper the comparatively recent discovery of generator instability is discussed. A method of testing synchronous machinery in the unstable as well as in the stable range is described. The results of tests performed on two machines is shown and discussed. The conclusion is drawn that the design of customary machines will have to be improved, synchronous condensers installed on many long lines, or inefficient underloading of units will have to be tolerated.