Studies On Stator Single-phase-to-ground Faults Protection For A Powerformer Considering The Winding Electromotive Force Distribution

The Powerformer breaks through the limitation of traditional generator winding insulation,and the higher output voltage at the machine end can be directly connected to the power grid without going through a step-up transformer.Under the background of increasing environmental resource constraints,the advent of Powerformer is expected Become the next generation of power generation technology.However,the relay protection technology and secondary equipment research and development technology for Powerformer restrict the development of Powerformer.The unique physical structural characteristics of Powerformers’stators and windings will produce unique fault characteristics and fault mechanisms,making the traditional relay protection technology of the generator cannot be simply applied to the Powerformer.Therefore,based on the physical structure characteristics of the Powerformer and considering the influence of changes in the electrical characteristics of the windings on fault characteristics,the single-phase grounding protection of the Powerformer stator is studied in this paper,which is expected to expand the research ideas of the Powerformer stator grounding protection and improve the performance of the stator grounding protection scheme.In this paper,the single-phase grounding protection of Powerformer stator is studied according to the following main contents:First,on the basis of considering the unique physical structure characteristics of the Powerformer,the stator structure,winding material,winding insulation method,winding way and the grid connection method of the Powerformer stator are analyzed.The influence mainly analyzes the influence of the difference in the physical structure of the Powerformer on the distribution of the winding capacitance to the ground and the distribution of the winding potential.Secondly,based on the differences in the electrical characteristics of the windings,the influence of the changes in the electrical characteristics of the windings on the fault characteristics is analyzed.The effects of the fundamental zero-sequence voltage and the third harmonic voltage fault characteristics are mainly analyzed.A kind of single-phase grounding protection scheme for Powerformer stator considering winding potential distribution.This scheme is divided into two parts:fundamental zero sequence voltage protection and third harmonic voltage protection.Finally,a distributed parameter model of the stator windings of the Powerformer is built in the PSCAD/EMTDC simulation software.The model takes into account the differences in the electrical characteristics of the windings,and performs simulation verification and applicability analysis of the proposed protection scheme.The protection scheme proposed in this paper fully considers the influence of the electrical characteristic distribution of the Powerformer stator windings on the protection scheme,and the simulation results show that the protection scheme has good protection performance,which is expected to provide ideas for the further study of the single-phase grounding protection technology of the Powerformer stator.