European practices in testing insulation in large synchronous machines

In discussions with a Swiss engineer relative to acceptance tests on a large generator of European manufacture, the authors learned that a number of test procedures were employed in Europe which are not too generally known in North America. It was felt that a presentation of some of the concepts and methods would be of interest to an American audience. Two tests of special note are a high frequency ionization test and an accelerated direct current high potential test (1).