A test-bed for researching the interactions of underexcitation and overexcitation limiters of synchronous generators with protection functions.

A test-bed implemented in a real-time digital simulation environment is presented in this article to perform coordination studies between protection functions and excitation limiters of automatic voltage regulators of synchronous generators. A hardware-in-the-loop simulation is implemented in laboratory to test and evaluate several protection schemes during underexcited and overexcited events. The interactions among the underexcitation and overexcitation limiters (UEL and OEL) with these protection functions are investigated, and the best settings for their coordination are proposed. This article increases the scope of [1] and [2] by including the interactions among the protection functions ANSI 24 (V/Hz), ANSI 59 (overvoltage), and ANSI 81 (underfrequency and overfrequency) with the OEL, and the interactions among the protection functions ANSI 21 (distance) and ANSI 27 (undervoltage) with the UEL in addition to the coordination between the protection function ANSI 40 (loss of excitation) and the UEL. Thus, the appropriate settings for these protection and controls are proposed for the excitation system developed. The main results are presented and discussed