Normal power supply system of a nuclear power plant — Modelling and simulation studies for fast bus transfer

Nuclear power plants have Normal and Emergency power supply systems. Both the power supply systems are to be reliable for safe operation of the plant. Prototype Fast Breeder Reactor (PFBR) coming up at Kalpakkam is a single unit 500 MWe project. The normal power supply system consists of two Station Buses and two Unit Buses. The station buses are fed from grid through a Station Transformer (ST). The Unit buses are fed through Unit Auxiliary Transformers(UATs) either from plant generator or grid. The UATs are normally fed by generator while plant is in operation. When plant generator is not available the UATs are fed from grid through generator transformer. Normally unit buses and station buses supply the loads connected to them. In the event of a need on supply interruption to one unit bus, the loads supplied from this bus can be transferred to a designated station bus and vice-versa for continuity of power supply to the loads. The ST and UAT are adequately sized for this. This paper covers the modeling of turbine generator, ST, UAT and the loads connected to the station and unit buses of this system to analyze the bus transfer of loads from a unit bus to station bus and vice-versa which keeps the plant loads running on fast transfer mode.