Governing of a Francis Turbine Model Subjected to Load Variations

Abstract

In this work, the problem of mechanical backlash in the governor system for the Francis test rig at the Waterpower Laboratory, NTNU Trondheim, is investigated. Through numerical simulations on a digital model of the test rig, done in the software SIMSEN, the maximum allowable backlash which still enables stable governing was detected. This was done by further developing the model used in the work by A. Ingranata [1], to perform load variation tests presented by Statnett [2]. From these frequency control tests it was concluded that the maximum mechanical backlash which still enables stable governing, is 1% of maximum stroke length of the servomotor present in the governor system. To design a system which can achieve the requirements of 1% backlash, a more conventional layout which utilizes links instead of the slots present in the existing governor ring, is suggested.