Dimension calculation and selection of grounding transformer and associated resistance for grounding of generator in HPP Prancevici
Abstract
The paper presents a detailed analysis and accompanying calculation based on which the equipment for grounding the star point of the synchronous generator at the Prancevici SHPP was dimensioned. It is a (single-phase) transformer for grounding the star point of the generator stator winding (which has a block transformer) with an associated resistor on its secondary. A current transformer in the secondary winding of the transformer for grounding intended for the connection of the 90% ground fault protection of the generator stator was also dimensioned. When selecting the equipment for grounding the generator, care was taken to optimally satisfy the following criteria: (i) the ground fault current at the generator voltage level must be limited to the value prescribed by the generator manufacturer (amount and duration), (ii) internal overvoltages at the generator voltage level must be lower than the withstand voltages of the insulation, (iii) the sensitivity of the 90% ground fault protection of the generator should be as high as possible.
