Study On Protective Relaying Of Weak Feed Mode

Weak feed is a common phenomenon in power system, which may obstruct the right action of protective relaying.In order to meet the four kinds of requirements for relay protection, scholars at home and abroad are researching on the weak feed side relay protection continuously.Witn many achievements made,there are still some deficincies. The paper focuses on the study of the weak feed lelectric parameters and the methods of weak feed mode identification and faulted-phase selection with better performance.First,by using the method of fault analysis,the expressions of measured impedance expressions and the tracks of measured impedance changing with positive sequence distribution coefficient are figured out.These results,which playing an important role in the study of weak feed electric parameters, is the precondition of exploring weak feed mode identification and faulted-phase selection methods.The main content of this article is weak feed mode identification and faulted-phase selection.Regarding weak feed mode identification,faulted-phase selection and the discriminant of power direction as a whole,the process of weak feed protective relaying is integrated in this paper.New method of weak feed mode identification makes full use of the lelectric parameters of negative sequence and zero sequence,which makes the weak feed identification result more reliable.New method of weak feed fault phase selection,which belongs to sequence component phase selection,is divided into selected phase selection and ground fault phase selection.Benefiting from the electric parameters choiced,this method of weak feed faulted-phase selection is free from the influence of transition impedance and load current.