Recommendations on Selecting the NPP Generator Transformer VA Rating

Abstract

The specific features of selecting the VA rating of a nuclear power unit step-up transformer are analyzed. The analysis is based on the provisions of the international standard IEEE C57.116-2022, which is a guide for transformers connected to turbine generators, taking into account the definition of the term “transformer VA rating” according to Russian and European standards (GOST 16110-82 and GOST 30830-2002). The definition of this term in this guide differs from that adopted in Russia and the EU member states. An example of analytical calculation of the generator step-up transformer steady-state apparent power in the reactive power generation and absorption modes (turbine generator inductive and capacitive operation modes) is considered. The calculation is confirmed by the simulation results in the ETAR software package. The inexpediency of selecting the generator step-up transformer VA rating from the standardized range of rated capacities according to GOST 17544-85 and GOST 9680-77 is substantiated. An adverse effect of overestimating the transformer VA rating on the maximum three-phase short-circuit fault current in the generator voltage circuit (in the main electrical connection circuit section between the turbine generator and step-up transformer) of a nuclear power plant unit is shown.