Synchronous machines with brushless excitation have the disadvantage that the field winding is not accessible for the de-excitation of the machine. This means that, despite the proper operation of the protection system, the slow de-excitation time constant may produce severe damage in the event of an internal short circuit. A high-speed de-excitation system for these machines was developed, and this study presents the continuation of a previously published study. This study presents the design by computer simulation and the results of the first commissioning of this de-excitation system in a commercial 20 MVA hydro-generator. The de-excitation is achieved by inserting resistance in the field circuit, obtaining a dynamic response similar to that achieved in machines with static excitation. In this case, a nonlinear discharge resistor was used, making the dynamic response even better.

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Φ Abstract --In this paper, the applicability of the FRA technique is discussed as a method for detecting inter-turn faults in stator windings. Firstly, this method is tested in an individual medium-voltage stator coil with satisfactory results. Secondly, the tests are extended to a medium-voltage induction motor stator winding, in which inter-turn faults are performed in every coil end of one phase. Results of the frequency response in case of inter-turn faults are evaluated in both cases for different fault resistance values. The experimental setup is also described for each experiment. The results of the application of this technique to the detection of inter-turn faults justify further research in optimizing this technique for preventive maintenance.Index Terms-Fault detection, inter-turn fault, stator winding.

Synchronous generators with brushless excitation have the disadvantage that the field winding is not accessible for the de-excitation of the generator. This means that, despite the proper operation of the protection system, the large deexcitation time constant may produce severe damage in the event of an internal short circuit. This paper describes a novel high speed de-excitation system (HSBDS) aimed at limiting the damage in the synchronous generator in case of an internal short circuit. The HSBDS for these generators was developed and it is in commercial operation. However in a power plant is not possible to test the operation of the HSBDS under sudden short circuit. This paper presents the results of a several tests in a laboratory 15 MVA brushless synchronous machine where internally reduced voltage sudden short-circuits have been performed. As a rated voltage short circuit could damage the laboratory 15 MVA machine, a computer model has been developed in order to assess the performance of the HSBDS in a real short circuit at rated voltage. The HSBDS under sudden short circuit conditions has been evaluated and validated through laboratory tests and computer simulations with satisfactory results.

Abstract-This paper presents a high performance system of regulation and stabilization of luminous flux for public street lighting installations. Its purpose is to reduce the luminous flux of the luminaries efficiently by reducing their voltage supply, resulting in the improvement of energy efficiency in the installation. The system is basically composed of electromagnetic components which provide robustness and high-performance to the device, as well as minimum maintenance requirements. However, the voltage regulation is based on the application of voltage steps. Aging studies of the luminaries have been carried out to analyze the impact of this discrete voltage regulation. A specific prototype of this voltage and stabilizer regulator have been in operation in a real outdoor lighting installation for more than one year.