A Single-line-to-ground Fault Location Method For Generator Stators Considering The Phase Characteristics Of Windings

At present,the three-phase synchronous generator is the main unit of thermal power generation in most countries in the world,Improving the protection scheme of large-scale generator units can not only ensure the stable operation of the generator unit,but also improve the safety and reliability of the entire power system.As an important branch of stator winding single-line-to-ground protection,stator winding fault location has certain research value.And the stator single-phase ground fault is the fault with the highest probability of occurrence.When the generator stator single-line-to-ground fault occurs,if the maintenance personnel do not check the fault in time,the single-line-to-ground fault may develop into a more harmful inter-phase and inter-turn short circuit fault.Therefore,the protection scheme of single-lineto-ground fault location of non-salient pole generator is studied in this paper.In this paper,the stator single-line-to-ground fault locating method of three-phase synchronous generator is studied from the following aspects:①The winding structure difference between salient pole generator and non-salient pole generator is analyzed,the electrical parameters such as fault winding potential,zero sequence voltage and winding potential phase angle after the stator single-line-to-ground fault of the non-salient pole generator are analyzed,which creates theoretical conditions for the formulation of subsequent protection schemes;②Simulation experiments were carried out on two generator fault phase selection methods,and the discriminant results were compared,and the more sensitive method was selected among the two methods,which provided a guarantee for the accurate location of the fault;③A fault position determination method considering the phase characteristics of the winding is proposed:On the basis of considering the potential phase characteristics of the windings of large-scale hidden pole generators,an accurate mathematical expression of the potential of the fault windings is proposed,combined with the transition resistance parameters after the single-phase grounding fault of the stator of the generator,the accurate positioning of the stator ground fault of the hidden-pole synchronous generator is realized;④A fault position determination method based on zero sequence voltage trajectory circle is proposed:Further,the distribution law of the zero-sequence voltage of the non-salient pole generator at different locations is analyzed,and the trajectory diagram of the zero-sequence voltage at the fault of each turn coil is calculated,and since the trajectory equation is determined only by the fault position and transition resistance,a new method is proposed to use the zero-sequence voltage trajectory diagram to determine the number of fault turns.Simulation results show that the proposed fault location methods can accurately locate the fault location under different generator operating conditions,which improves the situation that the traditional positioning method has low accuracy and is greatly affected by the transition resistance,and has certain guiding value for the application of generator stator single-line-to-ground fault protection in actual engineering.