Publikacje

Abstract:

Due to the supply reliability concerns or to supply remote loads in some distribution networks, the synchronous generators are used as auxiliary power sources. In Poland the generators are usually connected to the network of TN (earthed neutral point) structures. Both TN-C and TN-S or their mixed arrangements TN-C-S are used. Overcurrent protection in these circuits, according to Polish and international standards and the recommendation of SEP (Association of Polish Electrical Engineers), should also act as anti-shock protection. The protection is considered to be effective (for 400 V electrical installations) if the overcurrent protection trip takes less than 0.4 s (maximum allowable time of touching voltage occurrence). The investigation performed by authors, showed that the producers of the generators usually use B or C characteristic circuit breakers and for large generator sets (greater than 100 kVA) they recommend load split to the value of one fifth of the generator maximum power. Additionally, the most frequently excitation forcing equipment is mounted to keep short circuit current three times greater than nominal current of the generator. To assess the effectiveness of the anti-shock protection measures in circuits fed from auxiliary generator and for current lower than 32 A, the set up including a self-exiting 5.5 kVA and 400 V generator, overcurrent protection and load was built in laboratory. The set up uses miniature circuit breakers and enables short circuits in different instants, compared to the initial phase angle of the generator voltage.

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Experimental analysis of assessing of the tripping effectiveness of miniature circuit breakers in an electrical installation fed from a synchronous generator set