Improved hydrogenerator field winding thermal monitoring

Abstract

A new monitoring method for determination of average hydrogenerator field winding temperature is introduced in order to increase the robustness of the temperature measurement system using the classic U-I method. The classic approach is prone to error due to brush voltage drop, especially when field voltage is low. Developed thermal model is based on field current and cold cooling air temperature measurements, as well on temperatures acquired from digital temperature sensors mounted across the field winding. To monitor the rotor temperature for generators with brushless excitation where field voltage and current measurements are not accessible, a mathematical model was developed to estimate the average field winding temperature based on the existing temperature monitoring of the cooling medium and mounted sensors. Importance of the proposed approach arises from the foreseen widespread use of brushless generators in distributed generation. The developed models were compared and their sensitivity was examined thoroughly.