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SAŽETAK: Jedan od glavnih razloga pogrešnih prorada relejne zaštite transformatora je pojava uklopnih struja. Tranzijentna uklopna struja javlja se pri uklopu transformatora u prazan hod, a posljedica je zasićenja jezgre transformatora. U ovom radu analiziran je uklop autotransformatora 400/115/10, 47 kV, nazivne snage 300 MVA. Koristeći PAMSUITE alat za parametarsko modeliranje, na velikom broju EMTP simulacija prikazan je utjecaj pojedinih parametara modela na iznos i trajanje uklopnih struja te je određena vjerojatnost pojave drugog harmonika diferencijalne struje. Rezultati simulacija pokazuju da se kontroliranim uklopom smanjuje amplituda uklopnih struja i povećava udio drugog harmonika u diferencijalnim strujama. Na temelju rezultata proračuna određena su optimalna podešenja diferencijalne zaštite te izračunata vjerojatnost pogrešne prorade zaštite. ABSTRACT: One of the main causes of the incorrect operation of transformer relay protection are inrush currents. The transient inrush current occurs when energizing the unloaded transformer, and it is a consequence of the transformer core saturation. This paper presents analysis of transients caused by energization of autotransformer 400/115/10, 47 kV, with rated apparent power 300 MVA. Using the PAMSUITE parametric modeling tool, a large number of simulations was performed to show the impact of model parameters on the amplitude and duration of inrush currents as well as the probability of differential current 2nd harmonic amplitude occurrence. Simulation results show that controlled switching reduces inrush currents amplitudes and increases 2nd harmonic content in differential currents. Based on the simulation results, the optimal differential protection settings were determined, and the probability of false relay protection operation was calculated. |
