A Conductance-Susceptance Approach for Underexcitation Protection and Control Studies of Hydrogenerators

Synchronous generators protection and its controls are crucial for the reliability and stability of power systems. Their operation is interrelated, which means that they must be coordinated. In other words, their settings must be configured to be matching to avoid failure. With the objective of contributing to a straightforward analysis of the coordination between the ANSI 40 protection and the underexcitation limiter, this work presents the G-B plane as an alternative to the R-X plane This is a different way of dealing with the issue in question, since in the literature this analysis is usually made in the impedance (R-X) and the power (P-Q) planes. Noteworthy, the use of the P-Q plane is not accurate enough.. The generation system studied has its protection functions and controls modelled in a real-time digital simulator, with emphasis in the ANSI 40 protection and the underexcitation control. A physical relay takes part in the hardware-in-the-loop tests performed. The oscillography of the related machine control variables are graphically presented and discussed for each case analyzed. Bearing in mind this study and some complimentary literature, future research should focus on the enhancement of the above mentioned coordination.