The thesis addresses the procedure of the generator circuit-breaker selection on the basis of a short-circuit analysis. The procedure is then evaluated by using the example of the real system from the Nuclear Power Plant Krško (NEK).
The process of defining rated parameters suggests a calculation of short-circuit currents in two cases: the system-source short-circuit current and the generator-source short-circuit current through the generator circuit-breaker. The analysis is conducted by using the procedure for manual calculation. Its results are then validated by using the engineering software ETAP (Electrical Transient and Analysis Program).
The results of the short-circuit analysis provide the information about the maximum short-circuit current through the generator circuit-breaker for both of the above stated cases, when the generator is unloaded prior the fault. Additionally, the analysis using the engineering software ETAP provides the information about the short-circuit current, for cases when the generator is loaded prior the fault. In both cases the maximum short-circuit current is described with two parameters: the RMS value of its AC component and the peak current value. Lastly, the findings address the information about the degree of asymmetry at the moment of the contacts separation.
The comparison of both methods shows that the results common to both methods match well. The analysis shows that the rated parameters defined by the standard [1] can be calculated using only the procedure for manual calculation in the case of generator circuit-breaker for NEK. However, the usage of designated engineering tools provides the ability to analyze more complex modes of operation.
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