Research On Accurate Fault Location For Multi-Terminal Transmission Lines Based On Sequence Components

Usually,accidents such as power failure and voltage instability caused by transmission line failures result in significant economic losses.In addition,the longer the accident,the greater the loss.Therefore,after the fault occurs,the location of the fault is precisely and promptly locked,and staff members are promptly dispatched to repair the fault at the fault point,which can effectively guarantee the reliable electricity consumption at the load end.Nowadays,high-voltage multi-line and "petal" distribution network of new circuits and so on for power supply reliability requirements.As well as multi-terminal lines formed by distribution network with wind power,put forward higher requirements for quick and effective fault location.In this paper,the fault location of T-type circuit,complex multi-terminal line and T-type line with wind turbine are studied.The main achievements are as follows:(1)A two-terminal fault location algorithm based on power frequency sequence components is proposed.According to the fault characteristics,the equivalent value order impedance,the grid control and the outlet current characteristics of the doubly fed asynchronous wind turbine,the characteristics of impedance and current at the time of line fault of wind turbine are obtained and the need of fault location is clarified.Realizing the fault location of multi-end line with wind power.(2)Aiming at the problem that the traditional fault location method has a large dead zone near the branch contact,a precise fault location method based on positive sequence component is proposed.Fault branch identification and fault location can be achieved simultaneously.In the meantime,in view of the fact that most existing methods do not extend well to multi-end circuits with complicated topologies,this paper improves the proposed method and makes it suitable for multi-end circuits with more complex topologies.(3)In order to solve the problem of multi-terminal line fault location with wind turbines in recent years,a negative sequence correction algorithm is proposed to realize the fault location of multi-terminal line with wind turbines.At the same time,aiming at the fault location of the line during the startup process of wind turbine,the improved fault location method based on the positive sequence fundamental component is put forward.Finally,aiming at the problem of the special zone fault identification of the two wind turbines described in this paper,the corresponding fault zone identification method is put forward.Instead of using the numerical range as the basis for fault diagnosis,the method proposed in this paper discriminates the faulty branches based on the existence of two opposite solutions of the two-terminal equation.Thus effectively reducing the range of the dead zone near the branch contact.At the same time,fault location and tributary identification can be realized without prior identification of the tributary where the fault occurs.At the same time,the proposed virtual fault point makes the method of this paper simple and easy to popularize the multi-terminal fault location of various topologies by extending the discriminant matrix dimension.Based on the fact that the negative sequence equivalent impedance of wind turbine is relatively stable,the proposed negative sequence correction algorithm can be effectively used for the fault location of multi-terminal line with wind power.And the improved method is well adapted to the new requirements of fault location in the special operation of wind turbines.At the same time,the identification of special fault areas according to the voltage difference of bus bar can be effectively used in the fault location of the line with wind turbine.In this paper,the fault location of the existing complex multi-terminal line and T-line with wind turbine is studied in detail.The results of PSCAD simulation show that the proposed method is effective and reliable,and the application prospect is good.At the same time,the content of this paper is of some reference to further study the fault location of complex multi-terminal lines and T-type lines with wind power.