A New Runaway Speed Limiter for Kaplan Turbines

Abstract

The object of the paper is to show that the maximum runaway speed of a Kaplan turbine can be reduced, from 2.5 to 3.0 times normal, inherently common for this type, to a maximum value of less than 1.85 thus substantially reducing the cost of the generator. This is accomplished by means of a dependable “Runaway Speed Limiter” recently developed. The paper sets forth the basic principles involved and the confirmation of these principles by laboratory and field tests. It discusses several ways of utilizing these principles and leads to the selection of the preferred type on the basis of reliability. It then gives examples of applications of the selected type of Runaway Speed Limiter to new Kaplan units and results of the field tests available to date.