Resumo:
This dissertation work evaluates the behavior and the protection of a synchronous generator in parallel with a self-excited induction generator feeding several types of loads, on an isolated system, all modeled on the Real Time Digital Simulator (RTDS). A field of recent studies that still has few works in development, especially using large machines, as in this dissertation work.
To accomplish that, five operation scenarios were modeled from the main system and several disturbances were applied. The variation of synchronous machine excitation level and several short circuit faults in the system were simulated to analyze the machines response and the loss-of-field (ANSI 40) protection function and differential (ANSI 87G) protection function.
The correct machinery initialization sequence was analyzed on this work, and the protection functions were tested by using a commercial generator protection relay connected by hardware-in-the-loop to the RTDS. The dissertation presents the necessity of initialize the induction machine as a motor, as well as the operational characteristics of the system including a synchronous generator in parallel with an induction generator and the master and slave relationship between them.
The loss-of-field protection (ANSI 40) is tested by applying the reduction of 50% and 100% of the synchronous generator excitation. It was possible to analyze the non-acting of the protection ANSI 40 due to the lack of reactive power in the system with only one SG in parallel with the IG, and the operation of the protection in the system with two synchronous generators in parallel with the induction machine.
Furthermore, the differential protection function ANSI 87G was tested by applying line-ground, line-line and three-phase short circuits in several points of the system, in order to evaluate the protection behavior under the fault condition and to analyze the system behavior. After the application of the fault on the SG terminals, it is possible to verify the motorization of the IG after the protection function operates and removes the fault from the system.
