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Short circuit current supplied by induction generators is becoming a matter of concern due to the increasing power share. Besides, in spite of that the induction generator operation principle is analogous to the traditional synchronic generator, its excitation and thus short-circuit supply is widely dissimilar. Induction generators are mainly applied to produce electric energy through wind turbines. Several papers showing analytical studies have been published, but just a few experimental results have come out. The present work is carried out mainly experimentally, extending the results by applying simulation software. Experiments using laboratory scale induction generator are presented. Four induction generator excitation types where investigated: remnant magnetism excitation, capacitor excitation, dc rotor excitation, and double feed induction generator. As rarely just one type of excitation is available, combined excitations were also studied. The research shows that induction machine short circuit contribution is closely related to excitation type and that the currently used initial and successive damped values represent an overestimation.

High breaking capacity (HBC) fuse is today one of the most used low and medium voltage protective devices. Its operation principle presents two singular current values of difficult interruption, "critical current" and "minimum breaking current". These fuses, in general are not able to break any current that begins the melting process. An introduction about the HBC fuse design characteristics and operation modes is given. Standardized fuse classes are discussed based upon the IEC 60269 and IEC 60282 specifications. The error in the selection of the appropriate class is the most common mistake and the consequences go from damages to the protected equipment up to fuse violent explosion. Real typical cases of incorrect selection are presented, pointing out the consequences and risks. It is concluded that the only way to avoid errors in the selection is by means of the deep knowledge of the methodology of application of the HBC fuses.

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